Food Chemistry 145 (2014) 903–909
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Food Chemistry journal homepage: www.elsevier.com/locate/foodchem
Effect of farming systems on the yield, quality parameters and sensory properties of conventionally and organically grown potato (Solanum tuberosum L.) tubers V. Brazinskiene a,⇑, R. Asakaviciute a, A. Miezeliene b, G. Alencikiene b, L. Ivanauskas c, V. Jakstas c, P. Viskelis d, A. Razukas a a
Voke Branch of Lithuanian Research Centre for Agriculture and Forestry, Zalioji a. 2, Traku Voke, LT-02232 Vilnius, Lithuania Food Institute, Kaunas University of Technology, Kaunas, Taikos Rd. 92, LT-51180 Kaunas, Lithuania c Department of Analytical and Toxicological Chemistry, Lithuanian University of Health Sciences, A. Mickeviciaus g. 9, LT-44307 Kaunas, Lithuania d Institute of Horticulture, Lithuanian Research Centre for Agriculture and Forestry, Kauno g. 30, LT-54333 Babtai, Kaunas Distr., Lithuania b
a r t i c l e
i n f o
Article history: Received 24 April 2013 Received in revised form 29 August 2013 Accepted 3 September 2013 Available online 11 September 2013 Keywords: Potatoes Conventional and organic farming Yield Phenolic acids Phytophthora infestans Sensory properties
a b s t r a c t The objectives of this two-year research were to study the impact of two different farming types, conventional and organic, on the yield and sensory properties of five Lithuanian varieties of potato tuber. The parameters and properties examined were: phenolic acids; dry matter and starch content; and the spread and intensity of Phytophthora infestans growth. It was determined that potato yield fluctuates with the variety, but for conventional farming it is significantly (p < 0.05) higher than that obtained by organic farming. The farming type has no significant effect (p > 0.05) on the content of phenolic acids. No significant effect (p > 0.05) of farming type on dry matter and starch content, or sensory properties was found. No significant relation (p > 0.05) was found between the content of phenolic acids and P. infestans spread. The spread of P. infestans was faster and infection was heavier in organically grown potatoes. Ó 2013 Elsevier Ltd. All rights reserved.
1. Introduction Potatoes are among the world’s most widely cultivated crops, so the conditions under which they are grown, and the impact of these conditions on qualitative and quantitative parameters of potatoes, are very important. Most studies show that the average yields in farms engaged in organic farming are very small: less than 60% of yields obtained in conventional farms (Ninner & Horse, 1989; Sharpley, Robinson, & Smith, 1995). However, certain supporters of organic farming assert that the efficiency of organic farming nearly matches that of conventional farms (Ninner & Horse, 1989). According to Lithuanian and foreign authors, the yield of organically grown tubers decreases by between 5% and 40%, due to potato pests and diseases (Asakaviciute, Brazinskiene, & Razukas, 2013; Hansen, 2000; Razukas, Jundulas, & Asakaviciute, 2008). Quality also worsens: germination of potato tubers reduces, and storing properties deteriorate. Potato blight, caused by the fungus Phytophthora infestans (Mont.) de Bary, is one of the most important potato diseases ⇑ Corresponding author. Tel.: +370 5 2645439; fax: +370 5 2645430. E-mail address: [email protected] (V. Brazinskiene). 0308-8146/$ - see front matter Ó 2013 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.foodchem.2013.09.011
(Schepers, 2001). This disease causes serious problems in countries where high relative humidity prevails in summer, with warm days and cool nights. Potato blight causes yield losses of 15–50% every year, and during blight epiphytoty the yield loss can reach 80% (Sunseri, Johnson, & Dasgupta, 2002). The blight damage varies depending on: the locality of potato cultivation; growing conditions; weather conditions during the growing season; the disease onset time; variety resistance to blight; and volume and quality of plant protection measures (Asscheman et al., 1996; Hermansen, Hannukkala, Naerstad, & Brurberg, 2000). The main protection measures against blight are preventive, agrotechnical and chemical (Asscheman et al., 1996). Conventional agriculture receives a lot of criticism due to its chemical pollution of the environment, therefore much attention is now paid to the organic farming alternative (Hole et al., 2005). On organic farms herbicides are banned in potato crops. Weeds in potato fields are removed by mechanical means: cutting, ploughing, cultivation and harrowing. After potato sprouting, weeds are removed by earthing up and hoeing. Appropriately chosen rotation may also reduce the number of weeds in the soil. Colorado beetles, nematodes, wireworms, and cockchafers significantly damage potato crops. Colorado beetles could be collected and destroyed (in small areas), but in larger potato cultivation
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areas biological plant protection measures have to be used. In organic potato crops the use of synthetic pesticides, growth regulators, and genetically modified potato varieties is prohibited. The popularity of organic foods may be attributable to the perception that they are healthier, safer and tastier than conventionally produced foods (Hajslova et al., 2005; Gilsenan, Burke, & Barry-Ryan, 2010). In order to prove this in respect of potatoes, contents of various compounds accumulated in organically and conventionally grown potato tubers are often compared. This study examined the influence of farming type on phenolic acids, which are among the most important compounds for human health. Hydroxycinnamic acid derivative and chlorogenic acid and its isomers comprise up to 90% and more of the total content of phenolic compounds determined in potato tubers. Small amounts of caffeic, ferulic and coumaric acids are also determined (Friedman, 1997; Im et al., 2008; Mattila & Hellstrom, 2007; Ramamurthy, Maiti, Thomas, & Nair, 1992). Chlorogenic acid is a very important compound for human health because it is characterised not only by antioxidant (Higdon, 2006) but also anti-cancer (LaChance, 1997), and antidiabetic effects (Chesnay, 2007) as well as other beneficial properties. There is a growing volume of publications comparing the sensory properties of organically and conventionally grown potatoes (Gilsenan et al., 2010; Hajslova et al., 2005). However, very little attention has been given to the impact of farming type on the potato sensory profiles. The objectives of this study were to investigate the impact of the two different farming types, conventional and organic, on the degree of potato blight development, the yield, dry matter and starch content, sensory properties and phenolic acid content of the potato tubers of five Lithuanian varieties.
2. Materials and methods 2.1. Plant material Five Lithuanian potato varieties (VB Venta, Goda, VB Liepa, VB Rasa and VB Aista) were cultivated in the Voke branch of the LRCAF breeding plots with sandy loam soil on carbonated fluvioglacial eluviated gravel (JDp), according to FAO UNESCO classification – Haplic Luvisol (LVh) (Buividaite, 2005), with the following agrochemical characteristics: pHKCl – 5.9, the content of absorbed bases – 105 mEq kg 1 of soil, organic matter content – 2.1%, available phosphorus (P205) – 230 mg kg 1 and available potassium (K20) – 310 mg kg 1. Potatoes were grown following traditional potato production technology in both organic and conventional farming systems. In autumn the soil was ploughed deep. In spring, after soil maturation, the field was cultivated twice, then the land was cultivated with a rotary cultivator to a depth of 0.25 m. The field was furrowed before potato planting. In the case of conventional cultivation, potatoes were locally fertilised with universal complex fertilisers (Kemira Cropcare N10P10K20), and 80 kg ha 1 of nitrogen, 80 kg ha 1 of phosphorus and 160 kg ha 1 of potassium were added at planting time. In the case of organic farming, 60 kg ha 1 of nitrogen (Provita), 60 kg ha 1 of phosphorus (phosphorite powder) and 90 kg ha 1 of potassium (Patentkali) were inserted at planting time. After planting the interrows were hoed twice, every 7 days, using a rotary hiller. In the case of conventional farming, before the potato germination the field was sprayed with herbicide (Kernel 480 SL 3 l ha 1, active substance glyphosate 480 g l 1). Later the following pesticides were used: at the inflorescence formation (BBCH 50-55) and flowering (BBCH 6267) stages fungicide (Ridomilas Gold 2.5 kg ha 1, active substance metalaxyl-M 40 g kg 1 and mancozeb 640 g kg 1) in combina-
tion with insecticide (Actar 25 WG 0,07 kg ha 1, active substance thiamethoxam 250 g kg 1) were sprayed. In the organic farming potato field mechanical measures were used to fight weeds, and the larvae of Colorado beetles were collected by hand and destroyed. 2.2. Assessment of the degree of potato blight development Potato blight spread and degree of development were assessed at the flowering stage BBCH 60-65 (for each tested genotype). 100 plants were evaluated. Disease intensity was measured by the OEPP/EPPO approved and recommended scale (Schepers, 2000). Disease spread was calculated by the formula: P = n 100/N, where P – the spread of disease (%), n – number of infected plants, N – number of checked infection-free and infected plants. Disease intensity was calculated using the following formula: R = R(x)/N, where R – the disease intensity (%), R(x) – product sum (R) of the disease development percent and number of damaged plants in a certain percent group, N – number of checked infection-free and infected plants. 2.3. HPLC analysis for determination of phenolic acids 2.3.1. Chemicals Standards of seven materials were used in the chromatographic analysis: chlorogenic acid (Chromadex, USA); caffeic acid (labour dr. Ehrenstrofer-Schafers, Germany); neochlorogenic acid; vanillic acid; trans-cinnamic acid; trans-p-coumaric acid; and trans-ferulic acid (Sigma–Aldrich Production Gmbh, Switzerland). For extraction and chromatographic analysis gradient grade methanol (Sigma–Aldrich, Germany), purified and deionised water (18.2 mX cm 1), produced with a Millipore (USA) water purification system, and 99.8% acetic acid (Sigma–Aldrich, Germany) were used. 2.3.2. Sample preparation From the storage of each potato variety 5 randomly chosen tubers were taken. Washed, air-dried and sliced potato tubers were dried in a lyophilisator (Ilshin Lab Co., Ltd, Korea). Lyophilised potatoes were ground in a knife mill (Grindomix GM 200, Retsch, Germany) to a powder. When preparing an analytical sample, 1 g of the obtained powder was placed into an analytical flask and poured over with acetic acid, methanol and water (2:39:59; v/v/v) mixture to 10 ml. The mixture was then placed into an ultrasonic cleaner (Biosonic UC100, Coltene/Whaledent, USA.) for 20 min. Later the obtained potato extract was filtered first through paper and then through the membrane filter with a 0.22 lm pore size. For each potato sample three extracts were prepared. 2.3.3. Analysis The analysis was carried out using a Waters 2695 (Waters, Milford, USA) chromatograph. For the separation of active compounds a 4.6 250 mm, 5 lm ACE C18 column (Advanced chromatographic Technologies, Scotland) was used. During the analysis it was kept at an external temperature control module (Waters, Milford, USA), maintaining 25 °C temperature. During the analysis 10 ll of test solution were injected. The mobile phase flow rate was 1 ml min 1. The following gradient system was used: solvent A – 0.5% acetic acid in water, solvent B – methanol; 0 min – 95% A and 5% B, 40 min – 40% A and 60% B, 41 min – 10% A and 90% B, 55 min – 10% A and 90% B, 56 min – 95% A and 5% B. The separated active compounds were analysed using photodiode array detector Waters 996 PDA (Waters, Milford, USA) at a wavelength ensuring their maximum absorption: neochlorogenic acid – 324 nm, chlorogenic acid – 325 nm, caffeic acid – 323 nm, vanillic acid – 258 nm, cinnamic acid – 275 nm, coumaric acid – 309 nm, ferulic
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acid – 322 nm. Data were collected and analysed using a Waters Millennium 2000 chromatographic manager system (Waters Corporation, Milford, USA).
A 80 70 60 50 % 40 30 20 10 0
2.4. Sensory analysis
VB Venta VB Liepa
Goda
Organic farming
VB Rasa VB Aista
Conventional farming
B 55
50 45 40 35 % 30 25 20 15 10 5 0 VB Venta VB Liepa
Goda
Organic farming
VB Rasa VB Aista
Conventional farming
C
80 70 60 50 % 40 30 20 10 0 VB Venta VB Liepa
Organic farming
Goda
VB Rasa VB Aista
Conventional farming
D
55 50 45 40 35 % 30 25 20 15 10 5 0
2.4.1. Sample preparation The samples for sensory analysis were prepared by the method described by Pardo, Alvarruiz, Perez, Gemez, and Varon (2000): potatoes were washed and rinsed with tap water, then dried with a paper towel. The unpeeled potato samples were boiled for 30 min in unsalted water. The boiled potatoes were cut into cubes 2.0 2.0 cm, placed in warmed individual boxes marked with three digit numbers, covered with plastic lids and tempered for 5–10 min at 55 °C temperature prior to serving to the panellists. 2.4.2. Assessment of potato crumbliness, overall odour and taste intensity A quantitative descriptive analysis (ISO 13299, 2003) was carried out to compare potato samples grown using conventional and organic farming types. A tasting panel consisted of 7 assessors selected and trained to international standards, and experienced in sensory evaluation of different food products. The panel assessed the overall odour and taste intensity, and crumbliness of the boiled potato samples. A structured numerical scale was used for evaluation of the intensity of each attribute. The left side of scale corresponding to the lowest intensity of attribute was given value of 1, and the right side corresponding to the highest intensity was given value of 15. All sessions were conducted in a climate-controlled sensory science laboratory equipped with individual booths at the Kaunas University of Technology Food Institute. The panellists were instructed to clean the palate with water or weak warm tea between evaluations of each sample. The samples were presented to the panellists monadically. A data collection system for automatic acquisition of the assessor scores was used (FIZZ, Biosystems, France). 2.5. Determination of starch content The starch content in tubers was determined by the Reimann Parow scale.
VB Venta VB Liepa
Goda
Organic farming
VB Rasa VB Aista
Conventional farming
Fig. 1. Spread (A) and intensity (B) of potato blight in 2011 (LSD(a)0.05 = 1.703; LSD(b)0.05 = 1.616); spread (C) and intensity (D) of potato blight in 2012 (LSD(a)0.05 = 1.586; LSD(b)0.05 = 1.703).
2.6. Determination of dry matter content Determination of dry matter content was carried out according to the AOAC method. 2 g of raw potato were minced, weighed and then dried in oven at 105 °C for 24 h. The results were expressed as a percentage of dry matter content
Table 1 Main quality parameters of Lithuanian potato varieties. Potato varieties
a
Vegetation
VB Venta
Very early
VB Liepa
Early
Goda
Early
VB Rasa
Late
VB Aista
Very late
Mean of triplicated analysis ± standard error of the mean.
Farming type Organic Conventional Organic Conventional Organic Conventional Organic Conventional Organic Conventional LSD0,05
1
Yield (t ha
)
a
14.0 ± 0.68 27.9 ± 0.88 14.6 ± 0.52 29.3 ± 0.92 17.6 ± 0.91 35.2 ± 1.21 12.3 ± 0.64 24.6 ± 0.74 14.2 ± 0.37 28.4 ± 0.84 1.373
Starch (%)
Dry matter (%)
11.5 ± 0.49 14.4 ± 0.68 11.8 ± 0.54 18.9 ± 0.99 17.7 ± 0.94 17.6 ± 0.92 11.9 ± 0.53 16.6 ± 0.75 15.4 ± 0.69 17.1 ± 0.90 1.301
17.2 ± 0.54 20.2 ± 0.79 17.6 ± 0.61 24.6 ± 0.74 23.5 ± 0.88 23.3 ± 0.78 17.7 ± 0.58 22.4 ± 0.68 21.2 ± 0.68 22.9 ± 0.70 1.244
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Table 2 Contents of phenolic acids accumulated in tubers of organically and conventionally grown potatoes in 2011 and 2012. Potato varieties
Year
Farming type
VB Venta
2011
Organic Conventional Organic Conventional Organic Conventional Organic Conventional Organic Conventional Organic Conventional Organic Conventional Organic Conventional Organic Conventional Organic Conventional
2012 VB Liepa
2011 2012
Goda
2011 2012
VB Rasa
2011 2012
VB Aista
2011 2012
a b c
Content lg g
1
FWa
Neochlorogenic acid
Chlorogenic acid
Vanillic acid
Caffeic acid
Coumaric acid
Ferulic acid
Cinnamic acid
24.61 ± 4.12b 27.48 ± 1.94 18.55 ± 0.82 26.35 ± 0.53 28.33 ± 5.44 14.54 ± 1.52 12.29 ± 0.73 37.51 ± 0.37 93.87 ± 2.54 37.91 ± 2.61 58.46 ± 1.69 90.09 ± 5.40 43.90 ± 2.05 31.73 ± 4.07 27.70 ± 3.11 33.71 ± 2.54 79.93 ± 7.13 45.20 ± 3.26 25.83 ± 1.71 45.80 ± 0.06
106.01 ± 4.16 125.54 ± 5.67 64.95 ± 4.17 80.10 ± 1.11 95.44 ± 12.34 66.08 ± 3.85 48.84 ± 4.80 105.83 ± 0.42 111.81 ± 3.46 57.14 ± 1.81 62.49 ± 1.65 121.56 ± 6.53 143.17 ± 5.44 127.95 ± 18.00 96.12 ± 11.19 107.04 ± 7.71 135.13 ± 3.88 66.43 ± 5.08 53.45 ± 3.22 56.93 ± 0.52
0.28 ± 0.01 0.37 ± 0.02 0.33 ± 0.12 0.54 ± 0.01 0.50 ± 0.05 0.35 ± 0.01 0.37 ± 0.03 0.75 ± 0.03 0.39 ± 0.01 0.37 ± 0.01 0.78 ± 0.02 0.58 ± 0.02 n.d. 0.33 ± 0.02 0.46 ± 0.21 0.42 ± 0.03 0.29 ± 0.01 0.37 ± 0.01 0.63 ± 0.02 0.60 ± 0.03
17.13 ± 2.66 21.89 ± 2.20 10.15 ± 0.56 9.10 ± 0.25 10.73 ± 1.90 8.93 ± 0.42 5.75 ± 1.76 7.97 ± 0.19 13.49 ± 0.26 9.94 ± 0.38 8.01 ± 0.26 8.84 ± 0.83 13.19 ± 1.80 14.81 ± 0.63 7.99 ± 0.50 11.08 ± 0.86 12.12 ± 1.15 7.82 ± 0.53 8.09 ± 0.60 4.28 ± 0.11
n.d.c n.d. n.d. n.d. n.d. n.d. n.d. n.d. 0.78 ± 0.04 0.88 ± 0.01 0.84 ± 0.01 n.d. n.d. n.d. n.d. n.d. n.d. n.d. n.d. n.d.
1.86 ± 0.10 1.86 ± 0.23 1.48 ± 0.04 2.04 ± 0.04 2.37 ± 0.17 2.08 ± 0.04 1.55 ± 0.08 6.03 ± 2.74 6.74 ± 0.14 3.69 ± 0.13 4.61 ± 0.11 4.21 ± 0.25 1.68 ± 0.13 1.95 ± 0.12 1.61 ± 0.05 2.44 ± 0.14 2.76 ± 0.26 2.58 ± 0.10 1.98 ± 0.05 2.92 ± 0.03
0.21 ± 0.03 0.21 ± 0.02 n.d. n.d. 0.27 ± 0.03 0.19 ± 0.01 n.d. n.d. 0.29 ± 0.04 0.40 ± 0.04 n.d. n.d. 0.32 ± 0.04 0.42 ± 0.03 0.17 ± 0.03 0.18 ± 0.01 0.18 ± 0.01 0.32 ± 0.00 n.d. n.d.
Fresh weight. Mean of triplicated analysis ± standard error of the mean. Not detectable level.
2.7. Statistical analysis SigmaStat software, version 3.5 (San Jose, CA, USA) was used for the statistical analysis of the phenolic acids data. The analysis of variance was used to determine if significant differences existed among potato varieties and growth systems. Differences were classified by Tukey multiple comparison test (p < 0.05). The obtained data of potato blight spread and intensity were assessed also by the method of dispersion analysis. Differences were classified by LSD multiple comparison test (p < 0.05). The impact of the factor on the obtained results was evaluated using the partial eta-squared coefficient (g2). Correlation between the spread as well as intensity of blight and content of phenolic acids was calculated using the Pearson correlation coefficient (p < 0.05). SPSS software, version 15.0 (Chicago, IL, USA) was used for statistical analysis of sensory data. Students t test for independent samples was used to evaluate the effect of farming type. The analysis of variance was used to determine if the significant differences among potato varieties existed. Differences were classified by the Duncan multiple comparison test (p < 0.05).
was the most resistant among organically grown potatoes, while VB Liepa and VB Rasa were the most resistant among the conventionally grown. Farming type very strongly influences the spread of blight. In organically grown potato varieties, depending on the variety, the disease spread was between 1.3 and 2.8 times faster, and intensity between 2.5 and 5 times stronger than under conventional farming conditions (Fig. 1). Fungicides used in case of conventional farming type were most effective against P. infestans on plants of VB Rasa, and least effective on plants of VB Aista. Comparison of the influence of variety and farming type on the obtained results showed that farming type (a) had stronger influence than variety (b) or their interaction (ab): 2011 – g2a = 0.66, g2b = 0.23, g2ab = 0.10; 2012 – g2a = 0.70, g2b = 0.22, g2ab = 0.07. In recent years, in a natural infection background, the first signs of the disease appeared not only on leaves but also on stems, leaf axes, and axle shafts of unpaired leaves in the upper part of the plant and plant apexes. This indicates the increased aggressiveness and virulence of local pathogen populations as well as disease harmfulness.
3. Results and discussion 3.2. Qualitative and quantitative parameters of potato tubers 3.1. Potato blight spread and intensity Resistance of potato varieties to P. infestans is one of the most important achievements of the current selection. However, biology and populations of this pathogen change very quickly; the fungus can continuously develop many races that differ in their virulence and aggressiveness (Asscheman et al., 1996; Razukas et al., 2008), so the monitoring of potato varieties resistance to potato blight is very important. Studies of the resistance of Lithuanian potato varieties to blight spread and intensity in a background of natural infection in 2011 and 2012 revealed the significant influence of the variety (p < 0.05) (Fig. 1.). However, the individual characteristics of the variety and growing conditions interact (p < 0.05), so the resistance of potatoes grown under different conditions also differed: VB Aista
Potato yield fluctuates depending on the variety, but in case of conventional farming it is about double that obtained in organic farming (Table 1). In general, no clear tendency was found between farming type and dry matter or starch content. For some varieties, as VB Liepa and VB Rasa, there was higher dry matter and starch content in the case of conventional farming, but for VB Aista it was vice versa. For ‘‘early’’ potato cultivars (Lombardo, Pandino, & Mauromicale, 2012) the effect of farming type on accumulation of dry matter content also varied according to potato variety. The results of our study are not in agreement with the findings of other authors (Gilsenan et al., 2010; Hajslova et al., 2005) where lower dry matter content was found in case of conventional growing compared with organic.
V. Brazinskiene et al. / Food Chemistry 145 (2014) 903–909
μg·g-1 fresh weight
A 240 220 200 180 160 140 120 100 80 60 40 20 0 VB Venta VB Liepa OF bc* b CF a c
Goda a c
Organic farming (OF)
VB Rasa a a
VB Aista a dcb
Conventional farming (CF)
μg·g-1 fresh weight
B 240 220 200 180 160 140 120 100 80 60 40 20 0 VB Venta OF bcd CF ade
VB Liepa c b
Organic farming (OF)
μg·g-1 fresh weight
C
240 220 200 180 160 140 120 100 80 60 40 20 0
μg·g-1 fresh weight
VB Rasa a d
VB Aista d e
Conventional farming (CF)
2011 2012
VB Venta VB Liepa 2011 ab b 2012 bc ac
D
Goda a c
240 220 200 180 160 140 120 100 80 60 40 20 0
Goda c b
VB Rasa c b
VB Aista c bc
Goda b a
VB Rasa a b
VB Aista b b
2011 2012
VB Venta 2011 a 2012 b
VB Liepa b b
Fig. 2. Impact of farming type on total amount of phenolic acids in potato tubers in 2011 (A) and 2012 (B) and impact of meteorological conditions on the total amount of phenolic acids accumulated in potato tubers in cases of organic (C) and conventional (D) farming systems. *Varieties in the same line (same farming type or same year) with different superscripts are different at p < 0.05. Values are means of 3 replicates ± standard error of the mean.
3.3. Content of phenolic acids in potato tubers Comparison of the contents of phenolic acids in potato tubers during 2011 and 2012 in two farming types grown is presented in Table 2. Potato tubers of all varieties accumulated the highest contents of chlorogenic and neochlorogenic acids and the lowest contents of cinnamic acid. Coumaric acid was found only in tubers of Goda variety. The effect of chlorogenic acid on the spread of P. infestans had been noted already in the middle of the 20th century. It was found that a certain content of chlorogenic acid in potato tubers contrib-
907
utes to potato tuber resistance against Streptomyces scabies, Verticillium alboratum and P. infestans. Low concentrations of chlorogenic acid, on the contrary, stimulate the growth of P. infestans and Fusarium solani var. Coreuleum (Johnson & Schaal, 1952; Lee & LeTourneau, 1958; Valle, 1957). Quantitative analysis of phenolic acids accumulated in potato tubers of Lithuanian varieties revealed no statistically significant (p > 0.05) relationship between the spread of P. infestans and content of phenolic acids in potato tubers grown both organically and conventionally. The potato tubers were studied for two years (Fig. 2). The analysis of variance showed that the content of phenolic acids in potato tubers significantly (p < 0.05) depends on the variety and the year of harvest in both conventional and organic farming types. It can be assumed, therefore, that climatic conditions strongly influence biochemical processes in plants, and simultaneously the contents of the accumulated biologically active compounds. A statistically significant (p < 0.05) interaction among potato varieties and different harvest years was noted, therefore it is appropriate to analyse the results of each year separately. The content of accumulated phenolic acids in potatoes of the 2011 harvest depends on the farming type (Fig. 2A). Tubers of organically grown VB Liepa, Goda, VB Rasa and VB Aista accumulated higher contents of active compounds (49%, 106%, 14% and 87%, respectively) than conventionally grown tubers, but higher contents of statistical significance were determined only for VB Liepa, Goda and VB Aista tubers. Meanwhile, organically grown VB Venta (very early potato variety) tubers accumulated by 15% less phenolic acids than those grown conventionally. The content of accumulated phenolic acids in potatoes of the 2012 harvest also depends on the farming type (Fig. 2B), but, contrary to the 2011 results, tubers of all organically grown varieties accumulated less phenolic acids than in case of conventional cultivation: VB Venta – 19%, VB Liepa – 56%, Goda – 40%, VB Rasa – 13%, VB Aista – 19%. Significant (p < 0.01) influence of farming type on the contents of phenolic acids was determined only for VB Liepa and Goda tubers. In 2011 organically grown potatoes accumulated from 51% to 156% more phenolic acids than in 2012 (Fig. 2C). Such significantly (p < 0.01) higher content of biologically active compounds can be explained by the fact that June 2011 was much hotter and drier compared with 2012 and with the many-year average (Fig. 3). Since various abiotic and biotic factors (Dixon & Paiva, 1995) promote the accumulation of phenylpropanoids in potato tubers, the abiotic stress to plants during the year 2011 explains the increased contents of phenolic acids. This is confirmed by the analysis of variance, showing stronger influence of meteorological conditions (g2 = 0.52, p < 0.05) on the content of active compounds than of variety characteristics (g2 = 0.25, p < 0.05). The influence of the interaction of meteorological conditions and variety is significant (p < 0.05) but negligible (g2 = 0.07). In 2011 tubers of conventionally grown VB Venta, VB Rasa and VB Aista accumulated more phenolic acids than in 2012 (50%, 14% and 11%, respectively) (Fig. 2D). Significantly (p < 0.01) higher contents of active compounds in 2011 than in 2012 were recorded only in tubers of VB Venta, but VB Liepa and Goda in 2011 accumulated significantly lower contents of phenolic acids than in 2012 (42% and 51%, respectively). This is explained by the analysis of variance showing that in the case of conventional farming the content of accumulated phenolic acids is predetermined by both the variety (p < 0.05) and meteorological conditions (p < 0.05), but the strongest influence is exerted by the interaction of the individual characteristics of the variety and meteorological conditions (g2 = 0.52, p < 0.01). Summarising the above, it can be stated that the results obtained in the course of both years show no impact (p > 0.05), of the farming type on the content of phenolic acids, and this study
V. Brazinskiene et al. / Food Chemistry 145 (2014) 903–909
165
21
150
20
135
19
120
18
105
17
90
16
75
15
60
14
45
13
30
12
15
11
Rainfall multiannual average Rainfall 2011
Air temperature, Cº
Rainfall, mm
908
Rainfall 2012
Air temperature multiannual average Air temperature 2011
10
0
May
June
July
Air temperature 2012
August
Fig. 3. Precipitation and air temperature in May–August, 2011–2012.
Table 3 Sensory attributes of the Lithuanian potato varieties. Potato varieties
*
Vegetation
VB Venta
Very early
VB Liepa
Early
Goda
Early
VB Rasa
Late
VB Aista
Very late
Farming type Organic Conventional Organic Conventional Organic Conventional Organic Conventional Organic Conventional
Overall odour intensity *a
11.83 12.67ab 12.50ab 12.75ab 12.17ab 12.08ab 13.08ab 12.67ab 12.50b 12.83ab
Overall taste intensity a
11.08 11.42a 12.17a 12.58a 11.33a 11.08a 12.17a 12.17a 11.08a 11.25a
Crumbliness 6.75ab 6.33ab 6.42ab 7.25b 5.83ab 7.33b 4.83ab 5.25ab 4.17a 4.33a
Values within each column with different superscripts are different at p < 0.05. Values are means of 12 replicates.
confirms the conclusions of other authors (Soltoft et al., 2010). Meteorological conditions and individual characteristics of the variety have the greatest influence on the content of phenolic acids. Considering the content of phenolic acids, organically grown potatoes are more sensitive to climate change (abiotic stress). 3.4. Sensory analysis of potatoes Overall odour and taste intensity of the samples was not affected by farming type (Table 3). Significant (p < 0.05) differences in odour intensity were found between varieties VB Venta and VB Aista grown organically. Tubers of VB Aista had more overall odour in comparison with VB Venta (p < 0.05). The potatoes of both farming types were described as having typical odour and taste. The crumbliness was perceived as moderate regarding what is typical for potatoes boiled without peeling. Despite the fact that no significant effect of farming type was determined for potato crumbliness, some significant differences between varieties can be mentioned. Conventional VB Liepa and Goda tubers had higher crumbliness (p < 0.05) than VB Aista grown organically or conventionally. As reported for other potato varieties, no effects of farming type on sensory properties were determined for boiled tubers of ‘‘early’’ cultivars (Lombardo et al., 2012), unpeeled tubers boiled in steam (Hajslova et al., 2005), or raw samples of potato (Gilsenan et al., 2010). Potato skin has a significant effect on peculiarities of sensory perception in sensory analysis (Wszelaki et al., 2005), as usually panellists were able to detect sensory differences between samples containing skin, but for samples without skin such differences were not determined.
4. Conclusions Potato yield fluctuates depending on the variety, but in the case of conventional farming it is significantly higher than that obtained by organic farming (p < 0.05). Spread of potato blight was faster and its intensity was higher in organically grown potatoes than in those grown conventionally. No significant relation was found between the content of phenolic acids and P. infestans spread (p > 0.05). Evaluation of the two-year results show that farming type has no significant effect on the content of phenolic acids in potato tubers (p > 0.05). The farming type had no significant impact on the sensory properties of the potato varieties tasted. Potatoes grown in organic and conventional farming types had conventional odour, typical taste and moderate crumbliness. No significant effect (p > 0.05) of farming type on dry matter and starch content was found. Acknowledgement This work was partly supported by Research Council of Lithuania, Grant No. SVE-07/2011. References Asakaviciute, R., Brazinskiene, V., & Razukas, A. (2013). Late blight Phytophtora infestans (Mont.) de Bary resistance evaluation in ten Lithuanian potato cultivars. Icelandic Agricultural Sciences, 26, 45–48. Asscheman, E., Van der Zaag, D. E., Brinkman, H., Bus, C. B., Van Delft, M., Hotsma, P. H., Meijers, C. P., Mulder, A., Turkensteen, L. J., & Wustman, R. (1996). Potato diseases. The Netherlands: NIVAA. 216.
V. Brazinskiene et al. / Food Chemistry 145 (2014) 903–909 Buividaite, V. V. (2005). Soil survey and available soil data in Lithuania. ESB-RR9, 211–223. Chesnay, M. D. (2007). Caring for the vulnerable-perspectives in nursing theory, practice, and research. Jones Bartlett Publishers. 293. Dixon, R. A., & Paiva, N. L. (1995). Stress-induced phenylpropanoid metabolism. Plant Cell, 7, 1085–1097. Friedman, M. (1997). Chemistry, biochemistry, and dietary role of potato polyphenols. A review. Journal of Agricultural and Food Chemistry, 45, 1523–1540. Gilsenan, C., Burke, R. M., & Barry-Ryan, C. (2010). A study of the physicochemical and sensory properties of organic and conventional potatoes (Solanum tuberosum) before and after baking. International Journal of Food Science & Technology, 45, 475–481. Hajslova, J., Schulzova, V., Slanina, P., Janne, K., Hellenas, K. E., & Andersson, Ch. (2005). Quality of organically and conventionally grown potatoes: Four-year study of micronutrients, metals, secondary metabolites, enzymic browning and organoleptic properties. Food Additives & Contaminants, 22(6), 514–534. Hansen, J. G. (2000). Evaluation of variety field resistance against Phytophthora infestans in observation trials under natural conditions – Data from Estonia, Lithuania and Denmark. First year report on test of late blight resistance of local varieties, 17. Hermansen, A., Hannukkala, A., Naerstad, R. H., & Brurberg, M. B. (2000). Variation in population of Phytophthora infestans in Finland and Norway: Mating type, metalaxyl resistance and virulence phenotype. Plant Pathology, 49(1), 11–22. Higdon, J. (2006). An evidence-based approach to dietary phytochemicals (1st ed.). New York: Thieme. 27. Hole, D. G., Perkins, A. J., Wilson, J. D., Alexander, I. H., Grice, P. V., & Evans, A. D. (2005). Does organic farming benefit biodiversity? Biological Conservation, 122(1), 113–130. Im, H. W., Suh, B. S., Lee, S. U., Kozukue, N., Ohnisi-Kameyama, M., Levin, C. E., & Friedman, M. (2008). Analysis of phenolic compounds by high-performance liquid chromatography and liquid chromatography/mass spectrometry in potato plant flowers, leaves, stems, and tubers and in home-processed potatoes. Journal of Agricultural and Food Chemistry, 56(9), 3341–3349. ISO 13299, (2003). Sensory analysis – Methodology – General guidance for establishing a sensory profile. Johnson, G., & Schaal, L. A. (1952). Relation of chlorogenic acid to scab resistance in potatoes. Science, 115, 627–629. LaChance, P. A. (1997). Nutraceuticals-designer foods III: Garlic, soy and licorice (1st ed.). Trumbull: Food & Nutrition Press. 335.
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Lee, S. F., & LeTourneau, D. J. (1958). Chlorogenic acid content and verticillium wilt resistance of potatoes. Phytopathology, 48, 268–274. Lombardo, S., Pandino, G., & Mauromicale, G. (2012). Nutritional and sensory characteristics of ‘‘early’’ potato cultivars under organic and conventional cultivation systems. Food Chemistry, 133(4), 1249–1254. Mattila, P., & Hellstrom, J. (2007). Phenolic acids in potatoes, vegetables, and some of their products. Journal of Food Composition and Analysis, 20, 152–160. Ninner, B. J., & Horse, G. J. (1989). The search for sustainable agroecosystems. The Journal of Soil and Water Conservation, 44(2), 111–116. Pardo, J. E., Alvarruiz, A., Perez, J. I., Gemez, R., & Varon, R. (2000). Physical–chemical and sensory quality evaluation of potato varieties (Solanum tuberosum L.). Journal of Food Quality, 23(2), 149–160. Ramamurthy, M. S., Maiti, B., Thomas, P., & Nair, P. M. (1992). High-performance liquid chromatography determination of phenolic acids in potato tubers (Solanum tuberosum) during wound healing. Journal of Agricultural and Food Chemistry, 40(4), 569–572. Razukas, A., Jundulas, J., & Asakaviciute, R. (2008). Potato cultivars susceptibility to potato late blight (Phytophthora infestans). Applied Ecology and Environmental Research, 6(1), 95–106. Schepers, H. T. A. M. (2000). The development and control of Phytophthora infestans in Europe in 1999. PAV-Special Report, 6, 10–18. Schepers, H. T. A. M. (2001). The development and control of Phytophthora infestans in Europe in 2000. PAV-Special Report, 7, 9–18. Sharpley, A., Robinson, I. S., & Smith, S. I. (1995). Assessing environmental sustainability of agricultural systems by simulation of nitrogen and phosphorus loss in runoff. The European Journal of Agronomy, 4(4), 453–464. Soltoft, M., Nielsen, J., Laursen, K. H., Husted, S., Halekoh, U., & Knuthsen, P. (2010). Effects of organic and conventional growth systems on the content of flavonoids in onions and phenolic acids in carrots and potatoes. Journal of Agricultural and Food Chemistry, 58(19), 10323–10329. Sunseri, M. A., Johnson, D. A., & Dasgupta, N. (2002). Survival of detached sporangia of Phytophthora infestans exposed to ambient, relatively dry atmospheric conditions. American Journal of Potato Research, 79(6), 443–450. Valle, E. (1957). On anti-fungal factors in potato leaves. Acta Chemica Scandinavica, 11, 395. Wszelaki, A. L., Delwiche, J. F., Walker, S. D., Liggett, R. E., Scheerens, J. C., & Kleinhenz, M. D. (2005). Sensory quality and mineral and glycoalkaloid concentrations in organically and conventionally grown redskin potatoes (Solanum tuberosum). Journal of the Science of Food and Agriculture, 85, 720–726.
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Food Chemistry journal homepage: www.elsevier.com/locate/foodchem
Effect of farming systems on the yield, quality parameters and sensory properties of conventionally and organically grown potato (Solanum tuberosum L.) tubers V. Brazinskiene a,⇑, R. Asakaviciute a, A. Miezeliene b, G. Alencikiene b, L. Ivanauskas c, V. Jakstas c, P. Viskelis d, A. Razukas a a
Voke Branch of Lithuanian Research Centre for Agriculture and Forestry, Zalioji a. 2, Traku Voke, LT-02232 Vilnius, Lithuania Food Institute, Kaunas University of Technology, Kaunas, Taikos Rd. 92, LT-51180 Kaunas, Lithuania c Department of Analytical and Toxicological Chemistry, Lithuanian University of Health Sciences, A. Mickeviciaus g. 9, LT-44307 Kaunas, Lithuania d Institute of Horticulture, Lithuanian Research Centre for Agriculture and Forestry, Kauno g. 30, LT-54333 Babtai, Kaunas Distr., Lithuania b
a r t i c l e
i n f o
Article history: Received 24 April 2013 Received in revised form 29 August 2013 Accepted 3 September 2013 Available online 11 September 2013 Keywords: Potatoes Conventional and organic farming Yield Phenolic acids Phytophthora infestans Sensory properties
a b s t r a c t The objectives of this two-year research were to study the impact of two different farming types, conventional and organic, on the yield and sensory properties of five Lithuanian varieties of potato tuber. The parameters and properties examined were: phenolic acids; dry matter and starch content; and the spread and intensity of Phytophthora infestans growth. It was determined that potato yield fluctuates with the variety, but for conventional farming it is significantly (p < 0.05) higher than that obtained by organic farming. The farming type has no significant effect (p > 0.05) on the content of phenolic acids. No significant effect (p > 0.05) of farming type on dry matter and starch content, or sensory properties was found. No significant relation (p > 0.05) was found between the content of phenolic acids and P. infestans spread. The spread of P. infestans was faster and infection was heavier in organically grown potatoes. Ó 2013 Elsevier Ltd. All rights reserved.
1. Introduction Potatoes are among the world’s most widely cultivated crops, so the conditions under which they are grown, and the impact of these conditions on qualitative and quantitative parameters of potatoes, are very important. Most studies show that the average yields in farms engaged in organic farming are very small: less than 60% of yields obtained in conventional farms (Ninner & Horse, 1989; Sharpley, Robinson, & Smith, 1995). However, certain supporters of organic farming assert that the efficiency of organic farming nearly matches that of conventional farms (Ninner & Horse, 1989). According to Lithuanian and foreign authors, the yield of organically grown tubers decreases by between 5% and 40%, due to potato pests and diseases (Asakaviciute, Brazinskiene, & Razukas, 2013; Hansen, 2000; Razukas, Jundulas, & Asakaviciute, 2008). Quality also worsens: germination of potato tubers reduces, and storing properties deteriorate. Potato blight, caused by the fungus Phytophthora infestans (Mont.) de Bary, is one of the most important potato diseases ⇑ Corresponding author. Tel.: +370 5 2645439; fax: +370 5 2645430. E-mail address: [email protected] (V. Brazinskiene). 0308-8146/$ - see front matter Ó 2013 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.foodchem.2013.09.011
(Schepers, 2001). This disease causes serious problems in countries where high relative humidity prevails in summer, with warm days and cool nights. Potato blight causes yield losses of 15–50% every year, and during blight epiphytoty the yield loss can reach 80% (Sunseri, Johnson, & Dasgupta, 2002). The blight damage varies depending on: the locality of potato cultivation; growing conditions; weather conditions during the growing season; the disease onset time; variety resistance to blight; and volume and quality of plant protection measures (Asscheman et al., 1996; Hermansen, Hannukkala, Naerstad, & Brurberg, 2000). The main protection measures against blight are preventive, agrotechnical and chemical (Asscheman et al., 1996). Conventional agriculture receives a lot of criticism due to its chemical pollution of the environment, therefore much attention is now paid to the organic farming alternative (Hole et al., 2005). On organic farms herbicides are banned in potato crops. Weeds in potato fields are removed by mechanical means: cutting, ploughing, cultivation and harrowing. After potato sprouting, weeds are removed by earthing up and hoeing. Appropriately chosen rotation may also reduce the number of weeds in the soil. Colorado beetles, nematodes, wireworms, and cockchafers significantly damage potato crops. Colorado beetles could be collected and destroyed (in small areas), but in larger potato cultivation
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areas biological plant protection measures have to be used. In organic potato crops the use of synthetic pesticides, growth regulators, and genetically modified potato varieties is prohibited. The popularity of organic foods may be attributable to the perception that they are healthier, safer and tastier than conventionally produced foods (Hajslova et al., 2005; Gilsenan, Burke, & Barry-Ryan, 2010). In order to prove this in respect of potatoes, contents of various compounds accumulated in organically and conventionally grown potato tubers are often compared. This study examined the influence of farming type on phenolic acids, which are among the most important compounds for human health. Hydroxycinnamic acid derivative and chlorogenic acid and its isomers comprise up to 90% and more of the total content of phenolic compounds determined in potato tubers. Small amounts of caffeic, ferulic and coumaric acids are also determined (Friedman, 1997; Im et al., 2008; Mattila & Hellstrom, 2007; Ramamurthy, Maiti, Thomas, & Nair, 1992). Chlorogenic acid is a very important compound for human health because it is characterised not only by antioxidant (Higdon, 2006) but also anti-cancer (LaChance, 1997), and antidiabetic effects (Chesnay, 2007) as well as other beneficial properties. There is a growing volume of publications comparing the sensory properties of organically and conventionally grown potatoes (Gilsenan et al., 2010; Hajslova et al., 2005). However, very little attention has been given to the impact of farming type on the potato sensory profiles. The objectives of this study were to investigate the impact of the two different farming types, conventional and organic, on the degree of potato blight development, the yield, dry matter and starch content, sensory properties and phenolic acid content of the potato tubers of five Lithuanian varieties.
2. Materials and methods 2.1. Plant material Five Lithuanian potato varieties (VB Venta, Goda, VB Liepa, VB Rasa and VB Aista) were cultivated in the Voke branch of the LRCAF breeding plots with sandy loam soil on carbonated fluvioglacial eluviated gravel (JDp), according to FAO UNESCO classification – Haplic Luvisol (LVh) (Buividaite, 2005), with the following agrochemical characteristics: pHKCl – 5.9, the content of absorbed bases – 105 mEq kg 1 of soil, organic matter content – 2.1%, available phosphorus (P205) – 230 mg kg 1 and available potassium (K20) – 310 mg kg 1. Potatoes were grown following traditional potato production technology in both organic and conventional farming systems. In autumn the soil was ploughed deep. In spring, after soil maturation, the field was cultivated twice, then the land was cultivated with a rotary cultivator to a depth of 0.25 m. The field was furrowed before potato planting. In the case of conventional cultivation, potatoes were locally fertilised with universal complex fertilisers (Kemira Cropcare N10P10K20), and 80 kg ha 1 of nitrogen, 80 kg ha 1 of phosphorus and 160 kg ha 1 of potassium were added at planting time. In the case of organic farming, 60 kg ha 1 of nitrogen (Provita), 60 kg ha 1 of phosphorus (phosphorite powder) and 90 kg ha 1 of potassium (Patentkali) were inserted at planting time. After planting the interrows were hoed twice, every 7 days, using a rotary hiller. In the case of conventional farming, before the potato germination the field was sprayed with herbicide (Kernel 480 SL 3 l ha 1, active substance glyphosate 480 g l 1). Later the following pesticides were used: at the inflorescence formation (BBCH 50-55) and flowering (BBCH 6267) stages fungicide (Ridomilas Gold 2.5 kg ha 1, active substance metalaxyl-M 40 g kg 1 and mancozeb 640 g kg 1) in combina-
tion with insecticide (Actar 25 WG 0,07 kg ha 1, active substance thiamethoxam 250 g kg 1) were sprayed. In the organic farming potato field mechanical measures were used to fight weeds, and the larvae of Colorado beetles were collected by hand and destroyed. 2.2. Assessment of the degree of potato blight development Potato blight spread and degree of development were assessed at the flowering stage BBCH 60-65 (for each tested genotype). 100 plants were evaluated. Disease intensity was measured by the OEPP/EPPO approved and recommended scale (Schepers, 2000). Disease spread was calculated by the formula: P = n 100/N, where P – the spread of disease (%), n – number of infected plants, N – number of checked infection-free and infected plants. Disease intensity was calculated using the following formula: R = R(x)/N, where R – the disease intensity (%), R(x) – product sum (R) of the disease development percent and number of damaged plants in a certain percent group, N – number of checked infection-free and infected plants. 2.3. HPLC analysis for determination of phenolic acids 2.3.1. Chemicals Standards of seven materials were used in the chromatographic analysis: chlorogenic acid (Chromadex, USA); caffeic acid (labour dr. Ehrenstrofer-Schafers, Germany); neochlorogenic acid; vanillic acid; trans-cinnamic acid; trans-p-coumaric acid; and trans-ferulic acid (Sigma–Aldrich Production Gmbh, Switzerland). For extraction and chromatographic analysis gradient grade methanol (Sigma–Aldrich, Germany), purified and deionised water (18.2 mX cm 1), produced with a Millipore (USA) water purification system, and 99.8% acetic acid (Sigma–Aldrich, Germany) were used. 2.3.2. Sample preparation From the storage of each potato variety 5 randomly chosen tubers were taken. Washed, air-dried and sliced potato tubers were dried in a lyophilisator (Ilshin Lab Co., Ltd, Korea). Lyophilised potatoes were ground in a knife mill (Grindomix GM 200, Retsch, Germany) to a powder. When preparing an analytical sample, 1 g of the obtained powder was placed into an analytical flask and poured over with acetic acid, methanol and water (2:39:59; v/v/v) mixture to 10 ml. The mixture was then placed into an ultrasonic cleaner (Biosonic UC100, Coltene/Whaledent, USA.) for 20 min. Later the obtained potato extract was filtered first through paper and then through the membrane filter with a 0.22 lm pore size. For each potato sample three extracts were prepared. 2.3.3. Analysis The analysis was carried out using a Waters 2695 (Waters, Milford, USA) chromatograph. For the separation of active compounds a 4.6 250 mm, 5 lm ACE C18 column (Advanced chromatographic Technologies, Scotland) was used. During the analysis it was kept at an external temperature control module (Waters, Milford, USA), maintaining 25 °C temperature. During the analysis 10 ll of test solution were injected. The mobile phase flow rate was 1 ml min 1. The following gradient system was used: solvent A – 0.5% acetic acid in water, solvent B – methanol; 0 min – 95% A and 5% B, 40 min – 40% A and 60% B, 41 min – 10% A and 90% B, 55 min – 10% A and 90% B, 56 min – 95% A and 5% B. The separated active compounds were analysed using photodiode array detector Waters 996 PDA (Waters, Milford, USA) at a wavelength ensuring their maximum absorption: neochlorogenic acid – 324 nm, chlorogenic acid – 325 nm, caffeic acid – 323 nm, vanillic acid – 258 nm, cinnamic acid – 275 nm, coumaric acid – 309 nm, ferulic
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acid – 322 nm. Data were collected and analysed using a Waters Millennium 2000 chromatographic manager system (Waters Corporation, Milford, USA).
A 80 70 60 50 % 40 30 20 10 0
2.4. Sensory analysis
VB Venta VB Liepa
Goda
Organic farming
VB Rasa VB Aista
Conventional farming
B 55
50 45 40 35 % 30 25 20 15 10 5 0 VB Venta VB Liepa
Goda
Organic farming
VB Rasa VB Aista
Conventional farming
C
80 70 60 50 % 40 30 20 10 0 VB Venta VB Liepa
Organic farming
Goda
VB Rasa VB Aista
Conventional farming
D
55 50 45 40 35 % 30 25 20 15 10 5 0
2.4.1. Sample preparation The samples for sensory analysis were prepared by the method described by Pardo, Alvarruiz, Perez, Gemez, and Varon (2000): potatoes were washed and rinsed with tap water, then dried with a paper towel. The unpeeled potato samples were boiled for 30 min in unsalted water. The boiled potatoes were cut into cubes 2.0 2.0 cm, placed in warmed individual boxes marked with three digit numbers, covered with plastic lids and tempered for 5–10 min at 55 °C temperature prior to serving to the panellists. 2.4.2. Assessment of potato crumbliness, overall odour and taste intensity A quantitative descriptive analysis (ISO 13299, 2003) was carried out to compare potato samples grown using conventional and organic farming types. A tasting panel consisted of 7 assessors selected and trained to international standards, and experienced in sensory evaluation of different food products. The panel assessed the overall odour and taste intensity, and crumbliness of the boiled potato samples. A structured numerical scale was used for evaluation of the intensity of each attribute. The left side of scale corresponding to the lowest intensity of attribute was given value of 1, and the right side corresponding to the highest intensity was given value of 15. All sessions were conducted in a climate-controlled sensory science laboratory equipped with individual booths at the Kaunas University of Technology Food Institute. The panellists were instructed to clean the palate with water or weak warm tea between evaluations of each sample. The samples were presented to the panellists monadically. A data collection system for automatic acquisition of the assessor scores was used (FIZZ, Biosystems, France). 2.5. Determination of starch content The starch content in tubers was determined by the Reimann Parow scale.
VB Venta VB Liepa
Goda
Organic farming
VB Rasa VB Aista
Conventional farming
Fig. 1. Spread (A) and intensity (B) of potato blight in 2011 (LSD(a)0.05 = 1.703; LSD(b)0.05 = 1.616); spread (C) and intensity (D) of potato blight in 2012 (LSD(a)0.05 = 1.586; LSD(b)0.05 = 1.703).
2.6. Determination of dry matter content Determination of dry matter content was carried out according to the AOAC method. 2 g of raw potato were minced, weighed and then dried in oven at 105 °C for 24 h. The results were expressed as a percentage of dry matter content
Table 1 Main quality parameters of Lithuanian potato varieties. Potato varieties
a
Vegetation
VB Venta
Very early
VB Liepa
Early
Goda
Early
VB Rasa
Late
VB Aista
Very late
Mean of triplicated analysis ± standard error of the mean.
Farming type Organic Conventional Organic Conventional Organic Conventional Organic Conventional Organic Conventional LSD0,05
1
Yield (t ha
)
a
14.0 ± 0.68 27.9 ± 0.88 14.6 ± 0.52 29.3 ± 0.92 17.6 ± 0.91 35.2 ± 1.21 12.3 ± 0.64 24.6 ± 0.74 14.2 ± 0.37 28.4 ± 0.84 1.373
Starch (%)
Dry matter (%)
11.5 ± 0.49 14.4 ± 0.68 11.8 ± 0.54 18.9 ± 0.99 17.7 ± 0.94 17.6 ± 0.92 11.9 ± 0.53 16.6 ± 0.75 15.4 ± 0.69 17.1 ± 0.90 1.301
17.2 ± 0.54 20.2 ± 0.79 17.6 ± 0.61 24.6 ± 0.74 23.5 ± 0.88 23.3 ± 0.78 17.7 ± 0.58 22.4 ± 0.68 21.2 ± 0.68 22.9 ± 0.70 1.244
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Table 2 Contents of phenolic acids accumulated in tubers of organically and conventionally grown potatoes in 2011 and 2012. Potato varieties
Year
Farming type
VB Venta
2011
Organic Conventional Organic Conventional Organic Conventional Organic Conventional Organic Conventional Organic Conventional Organic Conventional Organic Conventional Organic Conventional Organic Conventional
2012 VB Liepa
2011 2012
Goda
2011 2012
VB Rasa
2011 2012
VB Aista
2011 2012
a b c
Content lg g
1
FWa
Neochlorogenic acid
Chlorogenic acid
Vanillic acid
Caffeic acid
Coumaric acid
Ferulic acid
Cinnamic acid
24.61 ± 4.12b 27.48 ± 1.94 18.55 ± 0.82 26.35 ± 0.53 28.33 ± 5.44 14.54 ± 1.52 12.29 ± 0.73 37.51 ± 0.37 93.87 ± 2.54 37.91 ± 2.61 58.46 ± 1.69 90.09 ± 5.40 43.90 ± 2.05 31.73 ± 4.07 27.70 ± 3.11 33.71 ± 2.54 79.93 ± 7.13 45.20 ± 3.26 25.83 ± 1.71 45.80 ± 0.06
106.01 ± 4.16 125.54 ± 5.67 64.95 ± 4.17 80.10 ± 1.11 95.44 ± 12.34 66.08 ± 3.85 48.84 ± 4.80 105.83 ± 0.42 111.81 ± 3.46 57.14 ± 1.81 62.49 ± 1.65 121.56 ± 6.53 143.17 ± 5.44 127.95 ± 18.00 96.12 ± 11.19 107.04 ± 7.71 135.13 ± 3.88 66.43 ± 5.08 53.45 ± 3.22 56.93 ± 0.52
0.28 ± 0.01 0.37 ± 0.02 0.33 ± 0.12 0.54 ± 0.01 0.50 ± 0.05 0.35 ± 0.01 0.37 ± 0.03 0.75 ± 0.03 0.39 ± 0.01 0.37 ± 0.01 0.78 ± 0.02 0.58 ± 0.02 n.d. 0.33 ± 0.02 0.46 ± 0.21 0.42 ± 0.03 0.29 ± 0.01 0.37 ± 0.01 0.63 ± 0.02 0.60 ± 0.03
17.13 ± 2.66 21.89 ± 2.20 10.15 ± 0.56 9.10 ± 0.25 10.73 ± 1.90 8.93 ± 0.42 5.75 ± 1.76 7.97 ± 0.19 13.49 ± 0.26 9.94 ± 0.38 8.01 ± 0.26 8.84 ± 0.83 13.19 ± 1.80 14.81 ± 0.63 7.99 ± 0.50 11.08 ± 0.86 12.12 ± 1.15 7.82 ± 0.53 8.09 ± 0.60 4.28 ± 0.11
n.d.c n.d. n.d. n.d. n.d. n.d. n.d. n.d. 0.78 ± 0.04 0.88 ± 0.01 0.84 ± 0.01 n.d. n.d. n.d. n.d. n.d. n.d. n.d. n.d. n.d.
1.86 ± 0.10 1.86 ± 0.23 1.48 ± 0.04 2.04 ± 0.04 2.37 ± 0.17 2.08 ± 0.04 1.55 ± 0.08 6.03 ± 2.74 6.74 ± 0.14 3.69 ± 0.13 4.61 ± 0.11 4.21 ± 0.25 1.68 ± 0.13 1.95 ± 0.12 1.61 ± 0.05 2.44 ± 0.14 2.76 ± 0.26 2.58 ± 0.10 1.98 ± 0.05 2.92 ± 0.03
0.21 ± 0.03 0.21 ± 0.02 n.d. n.d. 0.27 ± 0.03 0.19 ± 0.01 n.d. n.d. 0.29 ± 0.04 0.40 ± 0.04 n.d. n.d. 0.32 ± 0.04 0.42 ± 0.03 0.17 ± 0.03 0.18 ± 0.01 0.18 ± 0.01 0.32 ± 0.00 n.d. n.d.
Fresh weight. Mean of triplicated analysis ± standard error of the mean. Not detectable level.
2.7. Statistical analysis SigmaStat software, version 3.5 (San Jose, CA, USA) was used for the statistical analysis of the phenolic acids data. The analysis of variance was used to determine if significant differences existed among potato varieties and growth systems. Differences were classified by Tukey multiple comparison test (p < 0.05). The obtained data of potato blight spread and intensity were assessed also by the method of dispersion analysis. Differences were classified by LSD multiple comparison test (p < 0.05). The impact of the factor on the obtained results was evaluated using the partial eta-squared coefficient (g2). Correlation between the spread as well as intensity of blight and content of phenolic acids was calculated using the Pearson correlation coefficient (p < 0.05). SPSS software, version 15.0 (Chicago, IL, USA) was used for statistical analysis of sensory data. Students t test for independent samples was used to evaluate the effect of farming type. The analysis of variance was used to determine if the significant differences among potato varieties existed. Differences were classified by the Duncan multiple comparison test (p < 0.05).
was the most resistant among organically grown potatoes, while VB Liepa and VB Rasa were the most resistant among the conventionally grown. Farming type very strongly influences the spread of blight. In organically grown potato varieties, depending on the variety, the disease spread was between 1.3 and 2.8 times faster, and intensity between 2.5 and 5 times stronger than under conventional farming conditions (Fig. 1). Fungicides used in case of conventional farming type were most effective against P. infestans on plants of VB Rasa, and least effective on plants of VB Aista. Comparison of the influence of variety and farming type on the obtained results showed that farming type (a) had stronger influence than variety (b) or their interaction (ab): 2011 – g2a = 0.66, g2b = 0.23, g2ab = 0.10; 2012 – g2a = 0.70, g2b = 0.22, g2ab = 0.07. In recent years, in a natural infection background, the first signs of the disease appeared not only on leaves but also on stems, leaf axes, and axle shafts of unpaired leaves in the upper part of the plant and plant apexes. This indicates the increased aggressiveness and virulence of local pathogen populations as well as disease harmfulness.
3. Results and discussion 3.2. Qualitative and quantitative parameters of potato tubers 3.1. Potato blight spread and intensity Resistance of potato varieties to P. infestans is one of the most important achievements of the current selection. However, biology and populations of this pathogen change very quickly; the fungus can continuously develop many races that differ in their virulence and aggressiveness (Asscheman et al., 1996; Razukas et al., 2008), so the monitoring of potato varieties resistance to potato blight is very important. Studies of the resistance of Lithuanian potato varieties to blight spread and intensity in a background of natural infection in 2011 and 2012 revealed the significant influence of the variety (p < 0.05) (Fig. 1.). However, the individual characteristics of the variety and growing conditions interact (p < 0.05), so the resistance of potatoes grown under different conditions also differed: VB Aista
Potato yield fluctuates depending on the variety, but in case of conventional farming it is about double that obtained in organic farming (Table 1). In general, no clear tendency was found between farming type and dry matter or starch content. For some varieties, as VB Liepa and VB Rasa, there was higher dry matter and starch content in the case of conventional farming, but for VB Aista it was vice versa. For ‘‘early’’ potato cultivars (Lombardo, Pandino, & Mauromicale, 2012) the effect of farming type on accumulation of dry matter content also varied according to potato variety. The results of our study are not in agreement with the findings of other authors (Gilsenan et al., 2010; Hajslova et al., 2005) where lower dry matter content was found in case of conventional growing compared with organic.
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μg·g-1 fresh weight
A 240 220 200 180 160 140 120 100 80 60 40 20 0 VB Venta VB Liepa OF bc* b CF a c
Goda a c
Organic farming (OF)
VB Rasa a a
VB Aista a dcb
Conventional farming (CF)
μg·g-1 fresh weight
B 240 220 200 180 160 140 120 100 80 60 40 20 0 VB Venta OF bcd CF ade
VB Liepa c b
Organic farming (OF)
μg·g-1 fresh weight
C
240 220 200 180 160 140 120 100 80 60 40 20 0
μg·g-1 fresh weight
VB Rasa a d
VB Aista d e
Conventional farming (CF)
2011 2012
VB Venta VB Liepa 2011 ab b 2012 bc ac
D
Goda a c
240 220 200 180 160 140 120 100 80 60 40 20 0
Goda c b
VB Rasa c b
VB Aista c bc
Goda b a
VB Rasa a b
VB Aista b b
2011 2012
VB Venta 2011 a 2012 b
VB Liepa b b
Fig. 2. Impact of farming type on total amount of phenolic acids in potato tubers in 2011 (A) and 2012 (B) and impact of meteorological conditions on the total amount of phenolic acids accumulated in potato tubers in cases of organic (C) and conventional (D) farming systems. *Varieties in the same line (same farming type or same year) with different superscripts are different at p < 0.05. Values are means of 3 replicates ± standard error of the mean.
3.3. Content of phenolic acids in potato tubers Comparison of the contents of phenolic acids in potato tubers during 2011 and 2012 in two farming types grown is presented in Table 2. Potato tubers of all varieties accumulated the highest contents of chlorogenic and neochlorogenic acids and the lowest contents of cinnamic acid. Coumaric acid was found only in tubers of Goda variety. The effect of chlorogenic acid on the spread of P. infestans had been noted already in the middle of the 20th century. It was found that a certain content of chlorogenic acid in potato tubers contrib-
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utes to potato tuber resistance against Streptomyces scabies, Verticillium alboratum and P. infestans. Low concentrations of chlorogenic acid, on the contrary, stimulate the growth of P. infestans and Fusarium solani var. Coreuleum (Johnson & Schaal, 1952; Lee & LeTourneau, 1958; Valle, 1957). Quantitative analysis of phenolic acids accumulated in potato tubers of Lithuanian varieties revealed no statistically significant (p > 0.05) relationship between the spread of P. infestans and content of phenolic acids in potato tubers grown both organically and conventionally. The potato tubers were studied for two years (Fig. 2). The analysis of variance showed that the content of phenolic acids in potato tubers significantly (p < 0.05) depends on the variety and the year of harvest in both conventional and organic farming types. It can be assumed, therefore, that climatic conditions strongly influence biochemical processes in plants, and simultaneously the contents of the accumulated biologically active compounds. A statistically significant (p < 0.05) interaction among potato varieties and different harvest years was noted, therefore it is appropriate to analyse the results of each year separately. The content of accumulated phenolic acids in potatoes of the 2011 harvest depends on the farming type (Fig. 2A). Tubers of organically grown VB Liepa, Goda, VB Rasa and VB Aista accumulated higher contents of active compounds (49%, 106%, 14% and 87%, respectively) than conventionally grown tubers, but higher contents of statistical significance were determined only for VB Liepa, Goda and VB Aista tubers. Meanwhile, organically grown VB Venta (very early potato variety) tubers accumulated by 15% less phenolic acids than those grown conventionally. The content of accumulated phenolic acids in potatoes of the 2012 harvest also depends on the farming type (Fig. 2B), but, contrary to the 2011 results, tubers of all organically grown varieties accumulated less phenolic acids than in case of conventional cultivation: VB Venta – 19%, VB Liepa – 56%, Goda – 40%, VB Rasa – 13%, VB Aista – 19%. Significant (p < 0.01) influence of farming type on the contents of phenolic acids was determined only for VB Liepa and Goda tubers. In 2011 organically grown potatoes accumulated from 51% to 156% more phenolic acids than in 2012 (Fig. 2C). Such significantly (p < 0.01) higher content of biologically active compounds can be explained by the fact that June 2011 was much hotter and drier compared with 2012 and with the many-year average (Fig. 3). Since various abiotic and biotic factors (Dixon & Paiva, 1995) promote the accumulation of phenylpropanoids in potato tubers, the abiotic stress to plants during the year 2011 explains the increased contents of phenolic acids. This is confirmed by the analysis of variance, showing stronger influence of meteorological conditions (g2 = 0.52, p < 0.05) on the content of active compounds than of variety characteristics (g2 = 0.25, p < 0.05). The influence of the interaction of meteorological conditions and variety is significant (p < 0.05) but negligible (g2 = 0.07). In 2011 tubers of conventionally grown VB Venta, VB Rasa and VB Aista accumulated more phenolic acids than in 2012 (50%, 14% and 11%, respectively) (Fig. 2D). Significantly (p < 0.01) higher contents of active compounds in 2011 than in 2012 were recorded only in tubers of VB Venta, but VB Liepa and Goda in 2011 accumulated significantly lower contents of phenolic acids than in 2012 (42% and 51%, respectively). This is explained by the analysis of variance showing that in the case of conventional farming the content of accumulated phenolic acids is predetermined by both the variety (p < 0.05) and meteorological conditions (p < 0.05), but the strongest influence is exerted by the interaction of the individual characteristics of the variety and meteorological conditions (g2 = 0.52, p < 0.01). Summarising the above, it can be stated that the results obtained in the course of both years show no impact (p > 0.05), of the farming type on the content of phenolic acids, and this study
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21
150
20
135
19
120
18
105
17
90
16
75
15
60
14
45
13
30
12
15
11
Rainfall multiannual average Rainfall 2011
Air temperature, Cº
Rainfall, mm
908
Rainfall 2012
Air temperature multiannual average Air temperature 2011
10
0
May
June
July
Air temperature 2012
August
Fig. 3. Precipitation and air temperature in May–August, 2011–2012.
Table 3 Sensory attributes of the Lithuanian potato varieties. Potato varieties
*
Vegetation
VB Venta
Very early
VB Liepa
Early
Goda
Early
VB Rasa
Late
VB Aista
Very late
Farming type Organic Conventional Organic Conventional Organic Conventional Organic Conventional Organic Conventional
Overall odour intensity *a
11.83 12.67ab 12.50ab 12.75ab 12.17ab 12.08ab 13.08ab 12.67ab 12.50b 12.83ab
Overall taste intensity a
11.08 11.42a 12.17a 12.58a 11.33a 11.08a 12.17a 12.17a 11.08a 11.25a
Crumbliness 6.75ab 6.33ab 6.42ab 7.25b 5.83ab 7.33b 4.83ab 5.25ab 4.17a 4.33a
Values within each column with different superscripts are different at p < 0.05. Values are means of 12 replicates.
confirms the conclusions of other authors (Soltoft et al., 2010). Meteorological conditions and individual characteristics of the variety have the greatest influence on the content of phenolic acids. Considering the content of phenolic acids, organically grown potatoes are more sensitive to climate change (abiotic stress). 3.4. Sensory analysis of potatoes Overall odour and taste intensity of the samples was not affected by farming type (Table 3). Significant (p < 0.05) differences in odour intensity were found between varieties VB Venta and VB Aista grown organically. Tubers of VB Aista had more overall odour in comparison with VB Venta (p < 0.05). The potatoes of both farming types were described as having typical odour and taste. The crumbliness was perceived as moderate regarding what is typical for potatoes boiled without peeling. Despite the fact that no significant effect of farming type was determined for potato crumbliness, some significant differences between varieties can be mentioned. Conventional VB Liepa and Goda tubers had higher crumbliness (p < 0.05) than VB Aista grown organically or conventionally. As reported for other potato varieties, no effects of farming type on sensory properties were determined for boiled tubers of ‘‘early’’ cultivars (Lombardo et al., 2012), unpeeled tubers boiled in steam (Hajslova et al., 2005), or raw samples of potato (Gilsenan et al., 2010). Potato skin has a significant effect on peculiarities of sensory perception in sensory analysis (Wszelaki et al., 2005), as usually panellists were able to detect sensory differences between samples containing skin, but for samples without skin such differences were not determined.
4. Conclusions Potato yield fluctuates depending on the variety, but in the case of conventional farming it is significantly higher than that obtained by organic farming (p < 0.05). Spread of potato blight was faster and its intensity was higher in organically grown potatoes than in those grown conventionally. No significant relation was found between the content of phenolic acids and P. infestans spread (p > 0.05). Evaluation of the two-year results show that farming type has no significant effect on the content of phenolic acids in potato tubers (p > 0.05). The farming type had no significant impact on the sensory properties of the potato varieties tasted. Potatoes grown in organic and conventional farming types had conventional odour, typical taste and moderate crumbliness. No significant effect (p > 0.05) of farming type on dry matter and starch content was found. Acknowledgement This work was partly supported by Research Council of Lithuania, Grant No. SVE-07/2011. References Asakaviciute, R., Brazinskiene, V., & Razukas, A. (2013). Late blight Phytophtora infestans (Mont.) de Bary resistance evaluation in ten Lithuanian potato cultivars. Icelandic Agricultural Sciences, 26, 45–48. Asscheman, E., Van der Zaag, D. E., Brinkman, H., Bus, C. B., Van Delft, M., Hotsma, P. H., Meijers, C. P., Mulder, A., Turkensteen, L. J., & Wustman, R. (1996). Potato diseases. The Netherlands: NIVAA. 216.
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