Meat Science 97 (2014) 223–230

Contents lists available at ScienceDirect

Meat Science journal homepage: www.elsevier.com/locate/meatsci

Effect of different cooking methods on lipid oxidation and formation of volatile compounds in foal meat Rubén Domínguez, María Gómez, Sonia Fonseca, José M. Lorenzo ⁎ Centro Tecnológico de la Carne de Galicia, Rúa Galicia No 4, Parque Tecnológico de Galicia, San Cibrán das Viñas, 32900 Ourense, Spain

a r t i c l e

i n f o

Article history: Received 24 July 2013 Received in revised form 27 January 2014 Accepted 30 January 2014 Available online 9 February 2014 Keywords: Foal meat Thermal treatment Cooking loss Lipid oxidation Volatile compounds

a b s t r a c t The influence of four different cooking methods (roasting, grilling, microwaving and frying) on cooking loss, lipid oxidation and volatile profile of foal meat was studied. Cooking loss were significantly (P b 0.001) affected by thermal treatment, being higher (32.5%) after microwaving and lower after grilling (22.5%) and frying (23.8%). As expected, all the cooking methods increased TBARs content, since high temperature during cooking causes increased oxidation in foal steaks, this increase was significantly (P b 0.001) higher when foal steaks were microwaved or roasted. The four different cooking methods led to increased total volatile compounds (between 366.7 and 633.1 AU × 106/g dry matter) compared to raw steaks (216.4 AU × 106/g dry matter). The roasted steaks showed the highest volatile content, indicating that increased cooking temperature increases the formation of volatile compounds. Aldehydes were the most abundant compounds in cooked samples, with amounts of 217.2, 364.5, 283.5 and 409.1 AU × 10 6/g dry matter in grilled, microwaved, fried and roasted samples, respectively, whereas esters were the most abundant compounds in raw samples, with mean amounts of 98.8 AU × 106/g dry matter. © 2014 Elsevier Ltd. All rights reserved.

1. Introduction Meat aroma develops from the interactions of non-volatile precursors, including free amino acids, peptides, reducing sugars, vitamins, nucleotides and unsaturated fatty acids, during cooking. These interactions include the Maillard reaction between amino and carbonyl compounds, the oxidation of lipids, the thermal degradation of thiamine, and interactions between these pathways (Mottram, 1998). Cooking of meat is essential to achieve a palatable and safe product (Tornberg, 2005). In fact, heat treatments applied to meat, improve its hygienic quality by inactivation of pathogenic microorganisms and enhance its flavour and tenderness (Broncano, Petrón, Parra, & Timón, 2009; Rodríguez-Estrada, Penazzi, Caboni, Bertacco, & Lercker, 1997). However, cooking methods as well as cooking conditions, like heating rate, cooking time and temperature or end-point temperature, modify the chemical composition of meat with a consequent change of nutritional value due to nutrient losses (Brugiapaglia & Destefanis, 2012; Clausen & Ovesen, 2005; Kosulwat, Greenfiel, & Buckle, 2003). Another important adverse effect resulting from thermal treatment is lipid oxidation, a major reason for the deterioration of meat, giving undesirable odours, rancidity, texture modification, loss of essential fatty acids or toxic compound production (Alfaia et al., 2010; Broncano et al., 2009). Moreover, lipid oxidation products are implicated in several human

⁎ Corresponding author. Tel.: +34 988 548 277; fax: +34 988 548 276. E-mail address: [email protected] (J.M. Lorenzo). 0309-1740/$ – see front matter © 2014 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.meatsci.2014.01.023

pathologies (atherosclerosis, cancer, inflammation or ageing processes) (Broncano et al., 2009). There are many factors that influence lipid oxidation, including the composition and content of triglycerides (Carrapiso, 2007), and micro-components, such as antioxidants and metal ions (Ma, Ledward, Zamri, Frazier, & Zhou, 2009). However, for the controlled oxidation of any given lipid, the most important parameters are the thermal treatment conditions (temperature and time of cooking) (Byrnea, Brediea, Mottram, & Martens, 2002). Lower temperature of cooking could reduce energy consumption but a final internal temperature of 65–85 °C must to be reached to ensure safety (Tornberg, 2005). When different cooking methods were compared, roasting, which uses high temperatures for a long time, produces an increased lipid oxidation compared to other methods (Hernández, Navarro, & Toldrá, 1999; Rodríguez-Estrada et al., 1997). However, microwave treatment, despite using shorter time and lower temperature also promotes lipid oxidation (RodríguezEstrada et al., 1997). Frying is one of the oldest methods of food preparation and improves the sensory quality of food by formation of aroma compounds, attractive colour, crust and texture (Bognar, 1998), but oils or fats can change the fatty acid composition of meat and suffer oxidation (Broncano et al., 2009). In 2011, worldwide horse meat production was over 700 thousand tonnes. The major producers were Asia, with 42% of worldwide production, followed by America (32%) and Europe (19%). The greatest importers (by tonnes) of horse meat were Italy, Russia, Belgium and France, and the most important exporters (by tonnes) were Argentina, Belgium, Canada, Mexico and Poland (FAOSTAT, 2011).

224

R. Domínguez et al. / Meat Science 97 (2014) 223–230

Horse meat is characterized by low fat, low cholesterol content, and high levels of Fe–heme (Lorenzo & Pateiro, 2013; Lorenzo, Pateiro, & Franco, 2013). From the point of view of fatty acid composition, horse meat is characterized by high levels of unsaturated fatty acids (above 55%); PUFA, predominantly the essential n− 6 (linoleic acid, 18:2 n−6) and n−3 (ALA 18:3n−3) PUFA and MUFA, primarily oleic acid (18:1n−9c) (Lorenzo, 2013). Animal fat plays an important role in the formation of the characteristic flavour of cooked meat. It is well-known that lipid autooxidation can produce off-flavours, rancidity, known as “warmed-over flavour”. However, moderate lipid oxidation during the initial cooking of meat contributes to desirable aromas (Song et al., 2011). Unsaturated fatty acids and especially polyunsaturated ones (PUFA) are highly susceptible to oxidation (Alfaia et al., 2010), thus oxidation reactions could be very important during thermal treatment and affect the properties of this type of meat. To our knowledge, there are no studies describing the effect of cooking on foal meat quality. This study was, therefore, conducted to assess the influence of four different cooking methods (roasting, grilling, microwaving and frying) on cooking loss, lipid oxidation (by TBARs measurement) and volatile profile (using solid phase microextraction coupled to GC–MS) of foal meat.

2. Material and methods 2.1. Animals management Twelve foals were obtained from “Monte Cabalar” (agricultural cooperative of “Galician Mountain” breed) (A Estrada, Pontevedra, Spain). The majority of the foals were born in April and May of 2010. Animals were reared with their mothers on pasture and were kept suckling and grazing until 6–7 months old. After weaning, foals were fed mainly ryegrass (Lolium perenne), gorse (Ulex europaeus L.) and bracken (Pteridium aquilinum L.), receiving complementary grass silage ad libitum when the grass available was limited, especially in the summer and winter times, but they were never given concentrates. All foals were reared with their mothers in an extensive production system based on wood pasture. The animals were slaughtered at fifteen months old. They were transported to the abattoir the day before slaughter, without mixing foals from different groups, to minimize stress to the animals. The animals were stunned with a captive bolt and slaughtered and dressed according to current European Union regulations (Council Directive of the European Union 95/221EC) in an accredited abattoir. Immediately after slaughter, carcasses were chilled at 4 °C in a cold chamber for 24 h. At this point, longissimus dorsi (LD) muscle was extracted from the right side of each carcass, between the fourth and the ninth rib.

2.2. Sample preparation The LD muscles (n = 12) were sliced into 20 mm thick steaks and divided into five groups according to the cooking methods. A total of 60 samples were obtained (12 muscles × 5 cooking methods). One group was used as control (raw meat), and the other groups were cooked using the following methods: grilled at 130–150 °C during 5 min on each surface, using an electrical griddle (Delonghi, Mod. CG660, Treviso, Italy); microwaved at 1000 W for 1.5 min on each surface, using a microwave oven (Panasonic, Mod. NE-1037, Osaka, Japan); fried using 15 mL refined olive oil, at 170–180 °C during 4 min on each surface; roasted at 200 °C for 12 min using an electrical oven (Rational, Mod. SCC101, Barcelona, Spain). A heating treatment was considered complete when all the samples had reached an internal temperature of 70 °C. After cooking, cooling and calculated cooking loss, the steaks were minced, vacuum-packed and stored at − 30 °C for no longer than four weeks until analysis.

2.3. Cooking loss and TBARs measurement After cooking, the samples were cooled at room temperature for 30 min and the percentage of cooking loss recorded. Cooking loss was calculated as the percent weight difference between fresh and cooked samples relative to the weight of fresh samples: Cooking loss ¼

Raw meat weight−cooked meat weight  100: Raw meat weight

The 2-thiobarbituric acid (TBARs) assay was carried out according to the extraction method described by Vyncke (1975) with a few modifications: the meat sample (2.0 g) was homogenized (Ultra Turrax T-25, Janke & Kunkel IKA-Labortechnik, Staufen, Germany) with 10 mL of a 5% trichloroacetic acid (TCA) for 2 min at 3900 g (Allegra X-22R, Beckman, Fullerton, CA, USA), and the homogenate was centrifuged for 10 min at 2360 g (Allegra X-22R, Beckman, Fullerton, CA, USA) and then filtered through 0.45 μm (Filter Lab, Spain). The extract (5.00 mL) was mixed with 0.2 M thiobarbituric acid (5.00 mL) and heated in a 97 °C water bath (JP Selecta, Precisdg, Barcelona, Spain) for 40 min followed by cooling in ice-water for 5 min. The absorbance was measured (Agilent 8453, Waldbronn, Germany) at 532 nm against a blank consisting of 5 mL of the same homogenizing solution plus 5 mL of TBA solution. Thiobarbituric acid reactive substance (TBARs) values were calculated from a standard curve of malonaldehyde (MDA) and expressed as mg MDA/kg sample. 2.4. Volatile compound profile The extraction of the volatile compounds was performed using solid-phase microextraction (SPME). An SPME device (Supelco, Bellefonte, PA, USA) containing a fused-silica fibre (10 mm length) coated with a 50/30 mm thickness of DVB/CAR/PDMS (divinylbenzene/ carboxen/polydimethylsiloxane) was used and analysis was performed as following: For headspace SPME (HS-SPME) extraction, 3 g of each sample was weighed in a 40 mL vial, after being ground using a commercial grinder. The vials were subsequently screw-capped with a laminated Teflon-rubber disc. The fibre, previously conditioned by heating in a gas chromatograph injection port at 270 °C for 60 min, was inserted into the sample vial through the septum and exposed to headspace. The extractions were carried out in an oven at 35 °C for 30 min, after equilibration of the samples for 15 min at the temperature used for extraction, ensuring a homogeneous temperature for sample and headspace. Once sampling was finished, the fibre was withdrawn into the needle and transferred to the injection port of the gas chromatograph–mass spectrometer (GC–MS) system. A gas chromatograph 6890N (Agilent Technologies, Santa Clara, CA, USA) equipped with a mass selective detector 5973N (Agilent Technologies) was used with a DB-624 capillary column (30 m, 0.25 mm i.d., 1.4 μm film thickness; J&W Scientific, Folsom, CA, USA). The SPME fibre was desorbed and maintained in the injection port at 260 °C during 8 min. The sample was injected in splitless mode. Helium was used as a carrier gas with a linear velocity of 40 cm/s. The temperature programme was isothermal for 10 min at 40 °C, raised to 200 °C at 5 °C/min, and then raised to 250 °C at 20 °C/min, and held for 5 min: total run time 49.5 min. Injector and detector temperatures were both set at 260 °C. The mass spectra were obtained using a mass selective detector working in electronic impact at 70 eV, with a multiplier voltage of 1953 V and collecting data at 6.34 scans/s over the range m/z 40–300. Compounds were identified by comparing their mass spectra with those contained in the NIST05 (National Institute of Standards and Technology, Gaithersburg) library, and/or by comparing their mass spectra and retention time with authentic standards (Supelco, Bellefonte, PA, USA), and/or by calculation of retention index relative to a series

R. Domínguez et al. / Meat Science 97 (2014) 223–230

of standard alkanes (C5–C14) (for calculating Kovats indexes, Supelco 44585-U, Bellefonte, PA, USA) and matching them with data reported in literature. The results are expressed as area units (AU) × 106/g of dry matter. 2.5. Statistical analysis For the statistical analysis of cooking loss, TBARs values and volatile compounds a one way analysis of variance (ANOVA) using IBM SPSS Statistics 19.0 programme (IBM Corporation, Somers, NY, USA) was performed for all cooking treatments. When a significant effect (P b 0.05) was detected, means were compared using Duncan's t-test. Correlations between variables were determined by correlation analyses using the Pearson's linear correlation coefficient with the above statistical software package. 3. Results and discussion 3.1. Cooking loss and TBARs index The values corresponding to cooking loss (%) of foal steaks cooked using the different methods are shown in Table 1. Cooking loss is a combination of liquid and soluble matter lost during cooking and with increasing temperature, water content decreases while fat and protein contents increase indicating that the main part of cooking loss is water (Brugiapaglia & Destefanis, 2012), probably due to heat-induced protein denaturation during meat cooking, which causes less water to be entrapped within the protein structures (Juárez et al., 2010). The cooking loss depends on mass transfer during thermal treatment and, therefore, different cooking methodologies will lead to different losses (Cheng & Sun, 2008). In the present work cooking losses were significantly (P b 0.001) affected by the cooking method and were in the range (11–38%) in agreement with other authors (Brugiapaglia & Destefanis, 2012; Serrano, Librelotto, Cofrades, Saánchez-Muniz, & Jiménez-Colmenero, 2007). The losses were significantly (P b 0.05) higher (32.49 ± 6.41%) after microwaving and lower after grilling (22.45 ± 5.51%) and frying (23.73 ± 2.87%). The lower yield of microwaved steaks was consistent with other authors (Alfaia et al., 2010; Broncano et al., 2009; Serrano et al., 2007). It has been suggested that this is due to the fact that no crust forms during microwave cooking (Sánchez-Muniz & Bastida, 2006). However, this disagrees with Juárez et al. (2010) who observed that frying led to the highest moisture decrease, followed by grilling, while boiling showed the lowest water loss due to the incorporation of water during the cooking process. The effect of the different cooking methods on lipid oxidation of foal steaks is summarised in Table 1. The TBARs values obtained were similar to those found by Broncano et al. (2009) and Juntachote, Berghofer, Siebenhandl, and Bauer (2007) in cooked pork. The high values of TBARs in the present samples could be because meat from foals contains higher proportions of polyunsaturated fatty acids than other meats due to the feeding of these animals (Lorenzo, Fuciños, Purriños, & Franco, 2010; Lorenzo, Sarriés, & Franco, 2013). As expected, all the cooking methods increased TBARs content, since high temperatures increase oxidation processes in meat, the increase being significantly (P b 0.001) higher when foal steaks were microwaved or roasted (Table 1). This is in agreement with Weber, Bochi, Ribeiro, Victório, and Emanuelli (2008) who found more oxidation in microwaved samples than in roasted ones. However,

225

Serrano et al. (2007) noticed found that some cooking methods, such as microwaves and conventional oven, did not increase TBARs values in some restructured meat products. The fact that samples cooked by microwave had high levels of oxidation compounds suggests some interaction between microwave and meat fat which causes oxidation of polyunsaturated fatty acids (Broncano et al., 2009). This is in agreement with Yoshida, Hirakawa, Tomiyama, Nagamizu, and Mizushina (2005) who observed a decrease of PUFA values from phospholipids in different foods after microwave cooking and therefore suggested increased amounts secondary oxidation products originated from these fatty acids. The application of a higher temperature (200 °C) for a long time (12 min) in roasting produces more oxidation compared to the changes caused by frying at 170–180 °C for a shorter time (4 min). Consequently, it could be that oxidation processes during cooking are more affected by cooking time than temperature. Among all the assayed cooking methods, grilling was the one which showed the significantly (P b 0.05) lowest TBARs index, followed by frying (Table 1). The high temperature used in these treatments could cause reaction of the lipid oxidation compounds generated, with other molecules such as amino acids and peptides, that could appear due to proteolytic reactions, and therefore decrease the content of oxidation compounds and malonaldehyde (Meinert, Andersen, Bredle, Bjergegaard, & Aaslyng, 2007). In addition, the malonaldehyde formed during frying could be lost by dissolution in the frying oil (Weber et al., 2008). These results are in disagreement with those of Broncano et al. (2009) and Serrano et al. (2007) who suggested the higher oxidation levels in samples fried using different vegetable oils, such as virgin olive oil, partially hydrogenated plant oil and walnut fat, was due to the oxidation of polyunsaturated fatty acids in the oil. 3.2. Volatile compounds The effect of different cooking methods on the volatile compounds in the headspace of cooked foal steaks (expressed as AU × 106/g dry matter), is presented in Table 2. The SPME technique is not normally used for absolute quantifications, but when exactly the same extraction methodology is utilized, this technique does permit determination of the relative amounts between samples (Roberts, Pollien, Antille, Lindinger, & Yeretzian, 2003). A total of 57 volatile compounds were isolated and identified, of the following chemical families: 20 alkanes, 9 esters, 7 aldehydes, 4 aromatic hydrocarbons, 4 ketones, 3 furans, 3 hydrocarbons cyclic, 3 other compounds, 2 alkenes and 2 alcohols. Aroma flavour characteristics of cooked meat play the most important part in the acceptance and preference of meat by consumers (Van Ba, Hwang, Jeong, & Touseef, 2012). The most important mechanisms responsible for these volatile compounds are thermal degradation of lipid (mainly oxidation), Maillard reaction, interaction between Maillard reaction products with lipid-oxidized products and vitamin degradation (Van Ba et al., 2012). A significantly (P b 0.001) higher amount of total volatile compounds was observed in cooked steaks (between 401.47 and 618.48 AU × 106/g dry matter) compared to raw foal steaks (287.62 AU × 106/g dry matter). It is well known that both the temperature and cooking time significantly affect development of volatile compounds, and therefore the flavour of the cooked meat. The roasted foal steaks were exposed to a higher temperature

Table 1 Cooking loss (g/100 g muscle) and TBARs values (mg MDA/kg muscle) of raw and cooked foal meat.

Cooking loss TBARs a–c

Fresh

Grilled

Microwave

Fried

Roasted

S.E.M.

P value

– 0.11 ± 0.04a

22.45 ± 5.51a 0.40 ± 0.16a

32.49 ± 6.41c 1.31 ± 0.52b

23.73 ± 2.87ab 0.41 ± 0.19a

26.71 ± 3.51b 1.23 ± 0.78b

0.87 0.09

0.000 0.000

Different letters in each parameter indicate significant differences at P b 0.05; S.E.M.: Standard error of the mean.

226

R. Domínguez et al. / Meat Science 97 (2014) 223–230

Table 2 Volatile compounds (expressed as AU × 106/g dry matter) of raw and cooked foal meat. KI Alcohols 1-Pentanol 1-Hexanol, 2-ethyl Aldehydes Pentanal Hexanal 2-Hexenal Heptanal Benzaldehyde Octanal Nonanal Aromatic hydrocarbons Toluene Ethylbenzene p-Xylene o-Xylene Esters Butanoic acid, methyl ester Butanoic acid, 2-[(phenylmethoxy)imino]-, trimethylsilyl ester Butanoic acid, 3-methyl-, methyl ester Pentanoic acid, methyl ester Hexanoic acid, methyl ester Heptanoic acid, methyl ester Octanoic acid, methyl ester Nonanoic acid, methyl ester Decanoic acid, methyl ester Furans Furan, 2-ethyl Furan, 2-n-Butyl Furan, 2-pentyl Hydrocarbons cyclic 1R-.alpha.-Pinene Oxime, methoxy-phenyl Cyclooctane Ketones 2-Pentanone 3-Pentanone 2-Heptanone 3-Nonanone Lineal alkanes Heptane Octane Heptane, 3-ethyl Hexane, 2,2,5-trimethyl Heptane, 2,2,3,5-tetramethyl Undecane, 3-methyl Decane Decane, 2,3,5-trimethyl Nonane, 2,2,4,4,6,8,8-heptamethyl Octane, 2,6-dimethyl Undecane, 2,5-dimethyl Undecane, 3,6-dimethyl Decane, 3-methyl Undecane, 2,8-dimethyl Undecane, 4-methyl Undecane Dodecane Tridecane Tetradecane Nonadecane Lineal alkenes 3-Dodecene 6-Dodecene Other compounds Dimethyl sulfone 2,2-Dimethylhex-4-enylamine Triacetin Total volatile compounds

R

828 1081

m, k m, k

735 843 900 927 1020 1046 1149

m, s, k m, s, k m, k m, s, k m, k m, s, k m, s, k

795 882 889 910

m, k m, k m, k m

755 765

m, k m

811 856 935 1054 1153 1254 1354

m, k m, k m, k m, k m, k m, k m, k

715 903 1009

m, k m m, k

929 1014 1123

m m m

730 738 922 1131

m, k m m, k m

700 800 873 944 973 995 1000 1044 1052 1065 1067 1070 1075 1085 1099 1100 1200 1300 1400 1900

m, s, k m, s, k m m m m m, s, k m m m m m m m m m, s, k m, s, k m, s, k m, s, k m, s, k

1119 1142

m m

1057 1114 1421

m m m

Fresh

S.E.M.

P-value

1.38 0.00 1.38 7.94 0.00 4.16 0.00 0.00 3.78 0.00 0.00 44.14 11.29 5.79 20.23 6.83 145.37 27.76 0.00

± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ±

0.87b 0.00a 0.87b 1.14a 0.00a 1.48a 0.00a 0.00a 1.08 0.00a 0.00a 8.29a 2.56a 1.56 3.10a 1.96c 34.53c 10.21b 0.00a

Grilled 0.00 0.00 0.00 220.04 0.00 212.59 0.74 4.22 2.49 0.00 0.00 49.13 18.43 4.94 21.06 4.70 48.67 6.72 3.16

± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ±

0.00a 0.00a 0.00a 47.37b 0.00a 46.82b 0.32c 1.55b 1.15 0.00a 0.00a 13.08a 5.46b 1.20 4.75a 1.15a 10.73b 3.59a 1.13c

Microwave 0.00 0.00 0.00 376.90 26.58 325.40 0.47 7.84 3.74 0.00 12.87 50.76 18.38 5.92 21.10 5.36 28.19 1.99 2.28

± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ±

0.00a 0.00a 0.00a 76.84cd 7.23b 70.63cd 0.19b 2.75c 0.76 0.00a 2.39b 10.26a 3.56b 1.55 4.53a 1.17ab 11.81ab 0.41a 0.67b

Fried 0.00 0.00 0.00 274.19 0.00 234.06 0.00 6.32 2.57 10.37 20.87 42.65 11.36 5.06 20.72 5.51 55.38 3.93 3.42

± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ±

0.00a 0.00a 0.00a 32.21bc 0.00a 33.20bc 0.00a 3.42bc 0.26 4.09c 5.37d 12.52a 2.50a 1.37 3.87a 1.58abc 15.83b 1.50a 0.74c

Roasted 4.44 4.44 0.00 427.29 28.49 364.02 0.71 7.12 3.61 6.39 16.95 64.16 26.12 4.91 26.53 6.60 22.00 3.51 2.71

± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ±

2.02c 2.02b 0.00a 99.86d 3.97b 85.37d 0.25c 3.78c 1.36 2.22b 3.79c 12.84b 5.10c 2.21 7.66b 1.23bc 3.39a 0.81a 0.62bc

0.221 0.211 0.089 32.316 1.908 28.387 0.055 0.599 0.196 0.585 1.368 2.048 1.112 0.222 0.756 0.233 5.076 1.557 0.239

0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.101 0.000 0.000 0.000 0.000 0.433 0.072 0.008 0.000 0.000 0.000

17.37 2.74 32.01 6.06 24.95 11.87 22.61 0.00 0.00 0.00 0.00 5.94 0.80 5.14 0.00 16.77 6.92 9.15 0.00 0.70 58.62 2.82 5.23 0.00 0.00 1.06 0.00 2.12 4.59 0.00 0.00 0.00 0.00 1.07 0.82 0.00 33.45 2.11 1.41 0.00 0.00 0.00 0.00 0.00 7.46 7.46 0.00 0.00 287.62

± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ±

5.31d 0.71b 10.55c 2.17b 4.70c 4.08b 9.15b 0.00a 0.00a 0.00a 0.00a 1.34b 0.21b 1.20b 0.00a 4.46c 1.88c 3.05d 0.00a 0.24b 4.67a 1.78a 0.84ab 0.00a 0.00a 0.08a 0.00a 0.47a 0.89b 0.00a 0.00a 0.00a 0.00a 0.37bc 0.25a 0.00a 9.27c 0.74a 0.60a 0.00a 0.00a 0.00a 0.00a 0.00a 2.35b 2.35b 0.00a 0.00a 41.91a

6.52 2.01 19.05 0.00 5.76 2.87 2.58 2.54 0.00 0.00 2.54 2.92 0.69 2.23 0.00 8.88 3.07 3.01 1.89 0.91 64.29 2.36 3.61 0.26 5.11 3.36 2.16 4.06 0.00 7.01 2.27 1.83 3.68 0.89 1.84 0.00 21.24 3.45 1.97 0.00 0.30 0.00 0.00 0.00 5.00 3.40 1.21 0.39 401.47

± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ±

1.53c 1.05ab 7.55b 0.00a 1.90a 0.85a 1.62a 1.82b 0.00a 0.00a 1.82b 0.88a 0.31b 0.72a 0.00a 0.42b 0.88b 0.06b 0.80b 0.32bc 10.31b 0.78a 1.30a 0.11b 2.01b 1.10b 0.80b 1.37b 0.00a 1.96b 0.96b 0.49b 2.23b 0.24b 0.84b 0.00a 4.74a 1.45a 0.71a 0.00a 0.07b 0.00a 0.00a 0.00a 1.68a 1.57a 0.37c 0.07b 56.55b

0.00 1.19 16.48 0.00 4.00 2.25 0.00 5.27 0.37 0.80 4.10 2.08 0.00 2.08 0.00 3.05 2.00 0.00 0.00 1.05 89.08 4.36 9.56 0.54 9.87 4.06 4.90 6.93 0.00 9.72 0.00 2.90 3.88 0.00 3.06 1.11 22.68 5.31 3.21 0.41 0.39 1.29 0.00 1.29 4.40 4.22 0.00 0.18 561.02

± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ±

0.00a 0.35a 6.28b 0.00a 1.13a 0.82a 0.00a 2.00c 0.24b 0.23b 1.67c 0.45a 0.00a 0.45a 0.00a 0.75a 0.66a 0.00a 0.00a 0.40bc 18.86c 1.59a 3.40cd 0.24c 4.06c 1.61b 2.20d 3.16c 0.00a 2.97c 0.00a 0.90c 1.50b 0.00a 1.24c 0.49c 3.90ab 2.29b 1.88b 0.16b 0.13c 0.41b 0.00a 0.41b 1.49a 1.56a 0.00a 0.07ab 68.12c

0.00 2.73 27.60 0.00 11.66 3.90 2.14 1.73 0.00 0.00 1.73 7.58 0.00 6.00 1.58 10.44 2.99 6.17 0.00 1.28 95.91 8.60 11.67 0.40 7.48 4.39 3.95 5.79 0.00 12.36 2.95 0.00 3.76 1.57 3.54 0.00 21.84 6.01 2.44 0.00 0.31 2.24 1.09 1.15 6.12 5.37 0.00 0.75 496.24

± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ±

0.00a 1.14b 8.38c 0.00a 3.13b 1.15a 0.47a 0.67b 0.00a 0.00a 1.00b 3.54b 0.00a 3.44b 0.72c 3.79b 1.03ab 0.72c 0.00a 0.71c 13.18c 3.52b 2.37d 0.21bc 2.91bc 2.00b 1.36cd 2.21bc 0.00a 3.57d 0.90c 0.00a 1.57b 0.61cd 1.16c 0.00a 5.22ab 2.72b 0.75ab 0.00a 0.10b 0.89bc 0.52b 0.56b 1.55ab 1.66a 0.00a 0.43c 55.46c

3.23 1.17 5.64 0.00 3.49 1.77 0.48 4.12 1.06 0.00 3.06 3.54 0.00 2.87 0.67 5.83 2.35 0.00 3.48 0.00 78.29 3.20 7.02 0.51 7.04 0.65 3.01 4.92 0.00 6.76 0.00 2.32 2.37 1.70 2.11 0.74 27.57 3.32 2.47 0.37 0.00 2.25 0.91 1.34 6.56 5.22 0.90 0.44 618.48

± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ±

1.16b 0.55a 2.36a 0.00a 1.27a 0.68a 0.26a 2.28b 0.45c 0.00a 1.75bc 1.02a 0.00a 0.79a 0.31b 1.04b 0.68ab 0.00a 1.52c 0.00a 14.44bc 1.61a 3.96bc 0.27c 1.80c 0.47a 0.97bc 1.48b 0.00a 2.92b 0.00a 0.49b 0.67b 0.97d 0.70b 0.17b 5.57b 1.62a 1.14ab 0.16b 0.00a 0.89c 0.48b 0.67b 2.74ab 2.50a 0.35b 0.15b 87.36d

1.180 0.170 1.988 0.349 1.251 0.638 1.573 0.344 0.065 0.043 0.288 0.379 0.060 0.337 0.096 0.771 0.286 0.745 0.251 0.094 2.955 0.432 0.600 0.045 0.639 0.368 0.337 0.370 0.232 0.728 0.195 0.214 0.336 0.113 0.202 0.080 1.074 0.329 0.172 0.029 0.027 0.160 0.081 0.117 0.343 0.339 0.082 0.066 32.533

0.000 0.001 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.010 0.000 0.000 0.000 0.000 0.000 0.005 0.002 0.000 0.000 0.000

a–c Different letters in each parameter indicate significant differences at P b 0.05; S.E.M.: Standard error of the mean; AU: area units resulting of counting the total ion chromatogram (TIC) for each compound; KI: Kovats index calculated for DB-624 capillary column (J&W scientific: 30 m × 0.25 mm id, 1.4 μm film thickness) installed on a gas chromatograph equipped with a mass selective detector; R: Reliability of identification; k: Kovats index in agreement with literature (Lorenzo, Bedia, & Bañón, 2013; Lorenzo, Montes, Purriños, & Franco, 2012; Purriños, Carballo, & Lorenzo, 2013); m: mass spectrum agreed with mass database (NIST05); s: mass spectrum and retention time identical with an authentic standard.

R. Domínguez et al. / Meat Science 97 (2014) 223–230

(200 °C) than the other treatments, and roasted samples also had the highest volatile content, indicating that increased cooking temperature increases the formation of volatile compounds. These findings are in agreement with those of Ames, Guy, and Kipping (2001) in extruded feeds (the homogenate was made with cysteine, sugar and starch), who concluded that the amounts of total volatile flavour compounds increased with cooking temperature. Aldehydes were the main chemical family present in the headspace of cooked foal steaks, with amounts of 220.04, 376.90, 274.19 and 427.29 AU × 106/g dry matter in grilled, microwaved, fried and roasted samples, respectively. However, esters were the most abundant compounds in raw samples, with mean amounts of 145.37 AU × 106/g dry matter. Aldehydes in the cooked meat samples represent between 53 and 65% of total volatile compounds (Fig. 1). The sensory characteristics of aldehydes are mainly associated with a fatty aroma (Song et al., 2011). Within aldehydes, hexanal is the most important compound, representing 97.87, 89.26, 82.55 and 89.23% of the total aldehydes in grilled, microwaved, fried and roasted samples, respectively. However, aldehydes in raw steaks only represent 2.5% of total volatile compounds. Thermal treatment showed significant (P b 0.001) differences in total aldehyde content, since higher levels were observed in roasted and microwave samples, while grilled foal steaks presented the lowest amounts (Fig. 1). This suggests greater lipid oxidation in roasted and microwaved samples than in grilled and fried ones. These outcomes are consistent with those described by Broncano et al. (2009). The volatile compounds that are likely to have been generated from lipid oxidation include: pentanal, hexanal, 2-hexenal, heptanal, benzaldehyde, octanal and nonanal. This is consistent with that Rabe, Krings, and Berger (2003) who showed that lipids generally have the greatest influence on production of aroma components. Chen, Liu, and Chen (2002) reported that about 90% of the volume of volatile compounds in cooked meat arises due to lipid reactions. Mottram (1998) also observed that aldehydes, with 6–10 carbons, are major volatile compounds of all cooked meats and, therefore, play an important role in meat aroma. Similarly to TBARs values, hexanal content increased significantly (P b 0.001) when samples were cooked, suggesting lipid oxidation development. The trend observed for hexanal values was as follows (P b 0.05): roasted ≥ microwaved ≥ fried ≥ grilled. Grilled and fried samples also presented the lowest TBARs values. Taking into account the results of these widely used methods for lipid oxidation determination it is reasonable can say that this phenomenon is less affected by grilling and frying compared to the other treatments. As explained before, the application of 170–180 °C during 4 min in the fried method affected oxidation less than treatments involving longer times and lower temperatures. These results are consistent with those described by Meinert et al. (2007) and Nieto, Bañón, and Garrido (2011), who reported that hexanal was the major aldehyde in cooked lamb samples. In addition, Ma, Hamid, Bekhit, Robertson, and Law (2012) showed that hexanal, along with other aldehydes are important to the flavour of cooked beef. Although hexanal generated initially in meat can be continuously oxidized (Calkins & Hodgen, 2007) and contribute positively to meat flavour, it may produce undesirable flavours at higher concentrations (Ma et al., 2012). The predominance of hexanal over the others compounds in the volatile profile can be attributed to the multiplicity of its synthesis pathways. Nieto et al. (2011) have affirmed that this aldehyde can be generated from oleic acid, linoleic and arachidonic acids, and through the degradation of other unsaturated aldehydes, such as 2,4-decadienal. Unsaturated aldehydes are especially important for the fat aroma of meats, and may play some part in species-characteristic flavour (Rochat & Chaintreau, 2005), such as the 8–9 carbons n-2-alkenals that are related to a nut, tallow or cucumber aroma. Moreover, the high formation rate of the other aldehydes can be explained by theory proposed by Elmore, Mottram, Enser, and Wood (1999) who noticed

227

that the high temperatures used for cooking and reheating meat, favour the rapid oxidation of unsaturated fatty acids and increase the number of free radicals in the middle. These radical compounds attack other, less susceptible fatty acids, such as oleic acid, favouring the synthesis of heptanal, octanal and nonanal. Heptanal is associated with pungent and penetrating smell, while octanal has a flavour of fruit and green (Heiniö et al., 2003; Nieto et al., 2011). On the other hand, nonanal is an oxidation product of oleic acid, while benzaldehyde can be formed from the decomposition of linoleic acid, although some studies have suggested that a non-lipid route may also be involved (Chen et al., 2002). Benzaldehyde was the only aldehyde that displayed the same behaviour in all the four cooking methods, with higher peak area values after microwaving (Table 2). Esters are generated from the esterification of alcohols and carboxylic acids. The ester content was highest in the raw samples, representing 40% while in the cooked meat foal steaks they ranged between 2.6 and 8.9% of total volatile compounds. So, cooking markedly decreased (P b 0.001) the relative concentration of this chemical family, foal steaks after roasting showed the lowest amounts (22.00 AU × 106/g dry matter). Esters are very fragrant compounds with low odour detection thresholds, which are essential for the typical aroma of cured meat and fermented sausages either by adding a fruity note or by masking rancid odours (Gómez & Lorenzo, 2013; Wettasinghe, Vasanthan, Temelli, & Swallow, 2001). In raw meat, esters in the highest amount were hexanoic acid methyl ester, butanoic acid methyl ester, octanoic acid methyl ester and decanoic acid methyl ester. This profile coincides with that described by Lorenzo (2014) in raw foal meat, although the ester content was lower in this study. The lower value of esters in cooked than in raw meat suggests that thermal treatment degrade these esters and this decrease is higher in roasted foal steaks compared to grilled and fried treatments (Table 2). The literature shows no esters in cooked meat samples. In addition, Song et al. (2011) noticed that the presence of esters in cooked meat was probably caused by adding a methanol solution of benzyl alcohol as internal standard. Alkanes represented between 18.5 and 27.6% of the total volatile area in cooked foal steaks (Fig. 1). All cooked foal steaks had higher content of alkanes than the raw samples (Table 2). Alkane contents tended to be higher after microwaving (89.08 AU × 106/g dry matter) and frying (95.91 AU × 106 /g dry matter) than after grilling (64.29 AU × 106/g dry matter). Among these compounds, undecane was the most abundant (between 21.24 and 33.45 AU × 10 6/g dry matter), followed by nonane, 2,2,4,4,6,8,8,-heptamethyl and octane. The main source of aliphatic hydrocarbons with less than ten carbon atoms is lipid oxidation (Wettasinghe et al., 2001). With regard to aromatic hydrocarbons, the four different cooking methods showed significant (P b 0.001) differences, the highest amounts were observed in roasted foal steaks (64.16 AU × 10 6/g dry matter). Hydrocarbons are one of the largest classes in meat flavour, and are derived from the thermal degradation of lipid by thermal homolysis or autoxidation of long-chain fatty acid (Song et al., 2011). This suggests that the application of heat for a long time in roasting led to a higher amount of aromatic hydrocarbons compared to the other cooking methods. Within aromatic hydrocarbons, toluene and p-xylene were the most abundant. Aromatic hydrocarbons, especially toluene, could play an important role in the aroma of cooked foal steaks which give an aroma described as fruity and sweet (Madruga, Elmore, Oruna-Concha, Balagiannis, & Motrram, 2010). Concerning furans, the cooking process caused significant (P b 0.001) differences, since the highest contents were observed in foal steaks after microwaving (5.27 AU × 106/g dry matter), in raw samples furans were not detected (Table 2). Formation of furans is normally associated with heat, and is well-known Maillard reaction products (Chen et al., 2002). In microwaved samples three furans (furan, 2-ethyl, furan, 2-n-butyl and furan, 2-pentyl) were detected, whereas in the roasted foal steaks

228

R. Domínguez et al. / Meat Science 97 (2014) 223–230

1.01%

Grilled

Microwave

0.71%

0.21%

23.18% 25.66% 0.43% 1.32% 0.48% 0.64%

54.31%

0.34%

8.90%

0.83%

59.99%

3.82% 8.00%

10.17%

0.32%

Fried

1.15%

Roasted

0.33%

0.97%

0.71%

18.46% 27.64%

0.52%

0.85%

0.49% 2.59% 53.21%

9.89%

1.47% 1.37%

65.19% 7.59%

0.29% 6.96%

3.01%

0.56% 3.20%

Fresh 15.83% 28.58%

6.63% 39.86% 2.33%

Alcohols Furans Lineal alkenes

Aldehydes Hydrocarbons cyclic Other compounds

Aromatic hydrocarbons Ketones

Esters Lineal alkanes

Fig. 1. Effect of cooking methods on percentage of volatile compounds of foal steaks.

(furan, 2-ethyl and furan, 2-pentyl) and in samples from the fried and grilled methods (furan, 2-pentyl) were found. Van Ba et al. (2012) noticed that furans give an aroma described as sweet, burnt, pungent and caramel-like. These findings are in agreement with other authors (Chen et al., 2002; Ma et al., 2012; Song et al., 2011) who found furans in cooked meat. Regarding ketones, aromas are usually imparted by methylketones, which are the products of β-keto acids, and are derived from triglycerides by heat treatment. Methylketones were not detected in this study, and this may be due to the use of relatively mild thermal treatments. On the other hand, Mottram (1998) observed an increase in the content of ketones with increased lipid oxidation. In contrast, in the present study, foal steaks showed a decrease in total ketones with thermal treatment (Fig. 1). In the present study higher ketone contents were found in raw foal steaks (16.77 AU × 106/g dry matter) compared to cooked ones (between 3.05 and 10.44 AU × 106/g dry matter). Ketones, especially 2-ketones, are considered to have a great influence on the aroma of meat and meat products as they are present

in large amounts and have peculiar aromas, such as ethereal, butter, spicy or blue cheese notes (Van Ba et al., 2012). Finally, only two alcohols were detected in foal steaks. 1-hexanol,2ethyl was found in raw samples, while only one alcohol (1-pentanol) was present in roasted foal steaks. Aliphatic alcohols might contribute to a meat odour by means of unsaturated alcohols, because they have lower threshold values than saturated ones. For example, 1-pentanol was found to contribute to a mild, fusel oil, fruit and balsamic, odour while 1-hexanol,2-ethyl gives an aroma described as resin, flower and green (Calkins & Hodgen, 2007). The correlation coefficients between TBARs index and the major volatile components and total volatile compounds of raw and cooked foal steaks are shown in Table 3. There was a significant positive relationship between TBARs index and hexanal content (r = 0.794; P b 0.01), aldehyde level (r = 0.811; P b 0.01) and furan amount (r = 0.812; P b 0.01). On the other hand, as expected, Pearson correlation test showed higher positive correlation between total aldehydes and hexanal amounts (r = 0.995; P b 0.01). Ahn et al. (1998) also found that the

R. Domínguez et al. / Meat Science 97 (2014) 223–230

229

Table 3 Correlation coefficients between TBARs index and major volatile compounds of foal steaks.

Hexanal Total aldehydes Total esters Total furans Total volatile compounds

TBARs

Hexanal

Total aldehydes

Total esters

Total furans

0.794⁎⁎ 0.811⁎⁎ −0.540⁎⁎ 0.812⁎⁎ 0.766⁎⁎

0.995⁎⁎ −0.799⁎⁎ 0.766⁎⁎ 0.950⁎⁎

−0.806⁎⁎ 0.788⁎⁎ 0.970⁎⁎

−0.597⁎⁎ −0.722⁎⁎

0.722⁎⁎

⁎⁎ P b 0.01.

proportion of aldehydes increased gradually with lipid oxidation. There are a large number of studies that report a high correlation between TBARs values and aldehydes and hexanal amounts. Nieto et al. (2011) found a correlation between TBARs index and hexanal of 0.936, while Brunton, Cronin, Monahan, and Durcan (2000) found a correlation between TBARs value and hexanal of 0.99. The relationship between the contents of esters and TBARs index was significantly negative (r = − 0.540; P b 0.01), which seems to confirm that they degraded as lipid oxidation increased. Esters also showed a significant negative correlation (r = −0.722; P b 0.01) with the content of total volatile compounds. On the other hand, the correlation coefficients between the content of total volatile compounds and hexanal (r = 0.950; P b 0.01), aldehyde contents (r = 0.970; P b 0.01) and TBARs index (r = 0.766; P b 0.01) suggests, as discussed above, the compounds derived from lipid oxidation are the main compounds in the profile of volatile compounds in cooked foal steaks. According to Ahn et al. (1998), hexanal is the highest volatile component in oxidized meat, and the contents of hexanal and total volatile compounds provide the best representation of the lipid oxidation status of cooked meat. In this regard, Shahidi, Pegg, and Shamsuzzaman (1991) reported a linear relationship between the hexanal content and the sensory off-flavour scores in cooked meat. Nevertheless, Nieto et al. (2011) concluded that the use of a single compound, such a hexanal, does not adequately assess the degree of lipid oxidation and perceived flavour characteristics.

4. Conclusions The moderate oxidation of fat plays an important role in the formation of the characteristic cooked foal flavour. Within the cooking procedures used (roasting, grilling, microwaving and frying) microwaving caused the highest cooking loss. Grilling and frying appear to affect lipid oxidation to a lesser extent compared to the methods. As cooking temperature increased, an increasing in the formation of volatile compounds was observed. The cooked foal steaks contained high contents of aldehydes and lineal alkanes. On the other hand, thermal treatment let to a decrease of in esters and ketones levels. Hexanal, total aldehydes and total volatile compounds were highly correlated (P b 0.01) with TBARs value of cooked foal. This indicates that the content of aldehydes and hexanal is representative of the degree of lipid oxidation in cooked foal steaks.

References Ahn, D. U., Olson, D. G., Lee, J. I., Jo, C., Wu, C., & Chen, X. (1998). Packaging and irradiation effects on lipid oxidation and volatiles in pork patties. Journal of Food Science, 63, 15–19. Alfaia, C. P. M., Alves, S. P., Lopes, A. F., Fernandes, M. F. E., Costa, A. S. H., Fontes, C. M. G. A., Castro, M. L. F., Bessa, R. J. B., & Prates, J. A. M. (2010). Effect of cooking methods on fatty acids, conjugated isomers of linoleic acid and nutritional quality of beef intramuscular fat. Meat Science, 84, 769–777. Ames, J. M., Guy, R. C. E., & Kipping, G. J. (2001). Effect of pH and temperature on the formation of volatile compounds in cysteine/reducing sugar/starch mixtures during extrusion cooking. Journal of Agriculture and Food Chemistry, 49, 1885–1894. Bognar, A. (1998). Comparative study of frying to other cooking techniques influence on the nutritive value. Grasas y Aceites, 49, 250–260.

Broncano, J. M., Petrón, M. J., Parra, V., & Timón, M. L. (2009). Effect of different cooking methods on lipid oxidation and formation of free cholesterol oxidation products (COPs) in Latissimus dorsi muscle of Iberian pigs. Meat Science, 83, 431–437. Brugiapaglia, A., & Destefanis, G. (2012). Effect of cooking method on the nutritional value of Piemontese beef. Proceedings of the 58th International Congress of Meat Science and Technology, 12–17 August, Montreal, Canada. Brunton, N. P., Cronin, D. A., Monahan, F. J., & Durcan, R. (2000). A comparison of solid-phase microextraction (SPME) fibres for measurement of hexanal and pentanal in cooked turkey. Food Chemistry, 68, 339–345. Byrnea, D. V., Brediea, W. L. P., Mottram, D. S., & Martens, M. (2002). Sensory and chemical investigations on the effect of oven cooking on warmed-over flavour development in chicken meat. Meat Science, 61, 127–139. Calkins, C. R., & Hodgen, J. M. (2007). A fresh look at meat flavor. Meat Science, 77, 63–80. Carrapiso, A. I. (2007). Effect of fat content on flavour release from sausages. Food Chemistry, 103, 396–403. Chen, W. S., Liu, D. C., & Chen, M. T. (2002). The effect of roasting temperature on the formation of volatile compounds in Chinese-style pork Jerky. Asian-Australia Journal Animal Science, 15, 427–431. Cheng, Q., & Sun, D. W. (2008). Factors affecting the water holding capacity of red meat products: A review of recent research advances. Critical Reviews in Food Science and Nutrition, 48, 137–159. Clausen, I., & Ovesen, L. (2005). Changes in fat content of pork and beef after pan-frying under different condition. Journal of Food Composition and Analysis, 18, 201–211. Elmore, J. D., Mottram, D. S., Enser, M., & Wood, J. D. (1999). Effect of polyunsaturated fatty acid composition of beef muscle on the profile of aroma volatiles. Journal of Agricultural and Food Chemistry, 47, 1619–1625. FAOSTAT (2011). Online database of the Food and Agriculture Organization of the United Nations. http://faostat3.fao.org Gómez, M., & Lorenzo, J. M. (2013). Effect of fat level on physicochemical, volatile compounds and sensory characteristics of dry-ripened “chorizo” from Celta pig breed. Meat Science, 95, 658–666. Heiniö, R. L., Katina, K., Wilhelmson, A., Myllymäki, O., Rajamäki, T., Latva-Kala, K., Liukkonen, K. H., & Poutanen, K. (2003). Relationship between sensory perception and flavour-active volatile compounds of germinated, sourdough fermented and native rye following the extrusion process. Lebensmittel-Wissenschaft und-Technologie, Food Science and Technology, 36, 533–545. Hernández, P., Navarro, J. L., & Toldrá, F. (1999). Lipids of pork meat as affected by various cooking techniques. Food Science and Technology International, 5, 501–508. Juárez, M., Failla, S., Ficco, A., Peña, F., Avilés, C., & Polvillo, O. (2010). Buffalo meat composition as affected by different cooking methods. Food and Bioproducts Processing, 88, 145–148. Juntachote, T., Berghofer, E., Siebenhandl, S., & Bauer, F. (2007). The effect of dried galangal powder and its ethanolic extracts on oxidative stability in cooked ground pork. LWT-Food Science and Technology, 40, 324–330. Kosulwat, S., Greenfiel, H., & Buckle, A. (2003). True retention of nutrients on cooking of Australian retail lamb cuts of differing carcass classification characteristics. Meat Science, 65, 1407–1412. Lorenzo, J. M. (2013). Horsemeat as a source of valuable fatty acids. European Journal of Lipid Science and Technology, 115, 473–474. Lorenzo, J. M. (2014). Changes on physico-chemical, textural, lipolysis and volatile compounds during the manufacture of dry-cured foal “cecina”. Meat Science, 96, 256–263. Lorenzo, J. M., Bedia, M., & Bañón, S. (2013). Relationship between flavour deterioration and the volatile compound profile of semi-ripened sausage. Meat Science, 93, 614–620. Lorenzo, J. M., Fuciños, C., Purriños, L., & Franco, D. (2010). Intramuscular fatty acid composition of “Galician Mountain” foals breed. Effect of sex, slaughtered age and livestock production system. Meat Science, 86, 825–831. Lorenzo, J. M., Montes, R., Purriños, L., & Franco, D. (2012). Effect of pork fat addition on the volatile compounds of foal dry-cured sausage. Meat Science, 91, 506–512. Lorenzo, J. M., & Pateiro, M. (2013). Influence of type of muscles on nutritional value of foal meat. Meat Science, 93, 630–638. Lorenzo, J. M., Pateiro, M., & Franco, D. (2013). Influence of muscle type on physicochemical and sensory properties of foal meat. Meat Science, 94, 77–83. Lorenzo, J. M., Sarriés, M. V., & Franco, D. (2013). Sex effect on meat quality and carcass traits of foals slaughtered at 15 months of age. Animal, 7, 1199–1207. Ma, Q. L., Hamid, N., Bekhit, A. E. D., Robertson, J., & Law, T. F. (2012). Evaluation of pre-rigor injection of beef with proteases on cooked meat volatile profile after 1 day and 21 days post-mortem storage. Meat Science, 92, 430–439. Ma, H. J., Ledward, D. A., Zamri, A. I., Frazier, R. A., & Zhou, G. H. (2009). Effects of high pressure/thermal treatment on lipid oxidation in beef and chicken muscle. Food Chemistry, 104, 1575–1579.

230

R. Domínguez et al. / Meat Science 97 (2014) 223–230

Madruga, M. S., Elmore, J. S., Oruna-Concha, M. J., Balagiannis, D., & Motrram, D. S. (2010). Determination of some water-soluble aroma precursors in goat meat and their enrolment on flavour profile of goat meat. Food Chemistry, 123, 513–520. Meinert, L., Andersen, L. T., Bredle, W. L. P., Bjergegaard, C., & Aaslyng, M. D. (2007). Chemical and sensory characterization of pan-fried pork flavour: Interactions between raw meat quality, ageing and frying temperature. Meat Science, 75, 229–242. Mottram, D. S. (1998). Flavour formation in meat and meat products: A review. Food Chemistry, 62, 415–424. Nieto, G., Bañón, S., & Garrido, M. D. (2011). Effect of supplementing ewes' diet with thyme (Thymus zygis ssp. gracilis) leaves on the lipid oxidation of cooked lamb meat. Food Chemistry, 125, 1147–1152. Purriños, L., Carballo, J., & Lorenzo, J. M. (2013). The influence of Debaryomyces hansenii, Candida deformans and Candida zeylanoides on the aroma formation of dry-cured “lacón”. Meat Science, 93, 344–350. Rabe, S., Krings, U., & Berger, R. G. (2003). Influence of oil-in-water emulsion properties on the initial dynamic flavor release. Journal of the Science of Food and Agriculture, 83, 1124–1133. Roberts, D. D., Pollien, P., Antille, N., Lindinger, C., & Yeretzian, C. (2003). Comparison of nosespace, headspace, and sensory intensity ratings for the evaluation of flavor absorption by fat. Journal of Agricultural and Food Chemistry, 51, 3636–3642. Rochat, S., & Chaintreau, A. (2005). Carbonyl odourants contributing to the in-oven roast beef top note. Journal of Agricultural and Food Chemistry, 53, 9578–9585. Rodríguez-Estrada, M. T., Penazzi, G., Caboni, M. F., Bertacco, G., & Lercker, G. (1997). Effect of different cooking methods on some lipid and protein components of hamburgers. Meat Science, 45, 365–375. Sánchez-Muniz, F. J., & Bastida, S. (2006). Effect of frying and thermal oxidation on olive oil and food quality. Olive Oil and Health (pp. 74–108). Wallingford, United Kingdom: CABI Publishing.

Serrano, A., Librelotto, J., Cofrades, S., Saánchez-Muniz, F. J., & Jiménez-Colmenero, F. (2007). Composition and physicochemical characteristics of restructured beef steaks containing walnuts as affected by cooking method. Meat Science, 77, 304–313. Shahidi, F., Pegg, R. B., & Shamsuzzaman, K. (1991). Color and oxidative stability of nitrite-free cured meat after gamma-irradiation. Journal of Food Science, 56, 1450–1452. Song, S., Zhang, X., Havat, K., Liu, P., Jia, C., Xia, S., Xiao, Z., Tian, H., & Niu, Y. (2011). Formation of the beef flavour precursors and their correlation with chemical parameters during the controlled thermal oxidation of tallow. Food Chemistry, 124, 203–209. Tornberg, E. (2005). Effects of heat on meat proteins. Implications on structure and quality of meat produtcts. Meat Science, 70, 493–508. Van Ba, H., Hwang, I., Jeong, D., & Touseef, A. (2012). Principle of meat aroma flavors and future prospect. In Isin Akyar (Ed.), Latest Research into Quality Control (pp. 145–176). Rijeka: Croatia. Vyncke, W. (1975). Evaluation of the direct thiobarbituric acid extraction method for determining oxidative rancidity in mackerel (Scomber scombrus L.). Fette, Seifen, Anstrichmittel, 77, 239–240. Weber, J., Bochi, V. C., Ribeiro, C. P., Victório, A. M., & Emanuelli, T. (2008). Effect of different cooking methods on the oxidation, proximate and fatty acid composition of silver catfish (Rhamdia quelen) fillets. Food Chemistry, 106, 140–146. Wettasinghe, M., Vasanthan, T., Temelli, F., & Swallow, K. (2001). Volatile flavour composition of cooked by-product blends of chicken, beef and pork: a quantitative GC–MS investigation. Food Research International, 34, 149–158. Yoshida, H., Hirakawa, Y., Tomiyama, Y., Nagamizu, T., & Mizushina, Y. (2005). Fatty acid distributions of triacylglycerols and phospholipids in peanut seeds (Arachis hypogaea L.) following microwave treatment. Journal of Food Composition and Analysis, 18, 3–14.