Article pubs.acs.org/JAFC

Thermal Degradation and Isomerization of β‑Carotene in Oil-inWater Nanoemulsions Supplemented with Natural Antioxidants Jiang Yi,*,† Yuting Fan,‡ Wallace Yokoyama,§ Yuzhu Zhang,§ and Liqing Zhao*,† †

College of Chemistry and Environmental Engineering, Shenzhen University, Shenzhen 518060, China State Key Laboratory of Food Science and Technology, School of Food Science and Technology, Jiangnan University, Wuxi 214122, China § Western Regional Research Center, ARS, U.S. Department of Agriculture, Albany, California 94710, United States ‡

ABSTRACT: The goal of this study was to see the impact on the retention and isomerization of encapsulated β-carotene (BC) in nanoemulsions fortified with natural antioxidants (α-tocopherol (AT) and L-ascorbic acid (AA)). The physical stability of nanoemulsion, oxidative stability, and isomerization of all-trans-β-carotene (BC) in oil-in-water (O/W) nanoemulsions were determined in the presence or absence of natural antioxidants at 25 and 50 °C at certain intervals of time by high-performance liquid chromatography (HPLC). Sodium caseinate was used as the emulsifier, and corn oil (CO) was more protective than medium-chain triglycerides (MCT) and used for isomerization studies. Mean diameters of control (without antioxidants) and AA- and AT-fortified particles were similar. Mean particle diameter of nanoemulsions increased from 10 to 25 nm at 25 °C and from 40 to 50 nm at 50 °C during 30 days of storage. The isomerization from all-trans-BC to cis-BC isomers was inhibited by antioxidants. The isomerization rates were in the following order: 13-cis-BC > 15-cis-BC > 9-cis-BC. AT had better antioxidant activities than AA in inhibiting BC degradation in O/W nanoemulsions. The results indicated that BC encapsulated in nanoemulsions supplemented with antioxidants could significantly improve BC’s chemical stability. KEYWORDS: β-carotene, nanoemulsion, degradation, isomerization, antioxidant



ing.12 Isomerization of BC was reported to occur via a triplet excited state, and cation radical or dication formation are shown to play important roles in the isomerization process.13,14 However, the formation of cis-isomers is not desirable because they may decrease potential health-related activities. For example, a pro-vitamin A activity decrease (0.99. BC isomers were quantified with all-trans-BC equivalents due to unavailable commercial BC isomers. BC isomers were identified by spectral characteristics and Q ratios. The Q value is the height ratio of the cis peak to the main absorption peak in the spectrum. Storage Stability of BC Emulsions. The emulsion samples were transferred into Falcon tubes immediately after preparation. The samples were stored at 25 and 50 °C in incubators in the dark for 30 days, and equal aliquots were removed periodically for Z-average particle diameter, PDI, and BC concentration determination. All measurements were repeated in triplicate. Statistical Analysis. All experiments were conducted in triplicate, and all data were reported as means ± standard deviation. The correlations were determined by one-way ANOVA analysis of variance by using the SPSS17.0 statistical program (IBM Inc., Armonk, NY, USA). Duncan’s multiple-range test was used to determine the significant differences of mean values. A probability value of P < 0.05 was considered statistically significant.

MATERIALS AND METHODS

Materials. Sodium caseinate (Alanate 180) was purchased from Fonterra Co-operative Group (Auckland, New Zealand). Corn oil (CO) containing ∼54% linoleic acid, ∼28% oleic acid, ∼11% palmitic acid, and ∼2% stearic acid, according to the manufacturer, was purchased from a local market (Albany, CA, USA). Neobee 1053 (MCTs) was kindly supplied by Stepan Co. (Maywood, NJ, USA). BC (97%, no. 22040), L-ascorbic acid (AA), α-tocopherol (AT), and HPLC grade solvents (methanol, ethanol, acetonitrile, dichloromethane, n-hexane) were purchased from Sigma-Aldrich (St. Louis, MO, USA) and used without further purification. All other chemicals were purchased from Fisher Scientific (Fair Lawn, NJ, USA); ultrapure water was used in all experiments. Methods. Preparation of β-Carotene Emulsions. Sodium caseinate (SC) was dispersed in 10 mM phosphate buffer (PB) to form a 2% solution. To ensure the full dissolution and hydration, samples were stirred overnight at 4 °C. BC (0.1%) was dissolved in CO or MCT by stirring for 10 min at 50 °C and then for 1 h at room temperature to ensure complete solubilization. A crude emulsion of 10 wt % of the BC corn oil or MCT solution in the 2% SC 10 mM PB (pH 7.0) solution was prepared by high-speed homogenization for 2 min (T25, IKAWerk, Staufen, Germany). The crude emulsion was then further homogenized through a high-pressure microfluidizer (M-110L, Microfluidics, Westwood, MA, USA), seven passes at a homogenization pressure of 15000 psi (103.4 MPa) at constant temperature (25 °C), to make a fine nanoemulsion with reduced particle diameter. After the preparation, sodium azide (0.02%, w/w) was added to inhibit the growth of microorganism. Incorporation of Antioxidants with BC in Nanoemulsions. Due to the different water solubilities of AA and AT different methods were used to incorporate them into the BC nanoemulsions. AA (0.10%, wt) was dissolved in the protein PB (10 mM, pH 7.0) before mixing with the oil phase, and 0.10% (wt) AT was dispersed in CO with BC before the preparation of nanoemulsions. Nanoemulsion Particle Diameter Analysis. The Z-average particle diameter (Dz) and particle size distribution were determined by dynamic light scattering (Zetasizer Nano, Malvern Instruments, Worcestershire, UK) as previously described with minor modification.26 Emulsion samples were prepared by diluting BC-oil-in water nanoemulsions 100 times with 10 mM PB (pH 7.0). The refractive index values used for the instrumental analysis of oil droplets and



RESULTS AND DISCUSSION Analysis of BC Isomers by HPLC. Reverse phase highperformance liquid chromatography (RP-HPLC) was used to analyze and quantify the all-trans-BC and its cis isomers in BCloaded nanoemulsions under two storage conditions. Typical RP-HPLC chromatograms of initial all trans−cis isomers of BC on day 0 after nanoemulsion preparation (A), all trans−cis isomers of BC in nanoemulsion after storage for 30 days at 25 °C (B), and all trans−cis isomers of BC in nanoemulsion after storage for 30 days at 50 °C (C) are shown in Figure 1. The isomers of BC were identified by comparison with published Q ratios (the ratio of the peak in cis isomers at about 330−350 nm to the main peak, Table 1) from their respective spectra (Figure 2). Four peaks were observed in the chromatograms (15-cisBC, 13-cis-BC, all-trans-BC, and 9-cis BC with retention times of 13.20, 13.70, 15.25, and 15.89 min, respectively). The relative amounts of the isomers on day 0 were (from the peak area) 0.8 ± 0.1, 2.9 ± 0.1, 95.2 ± 1.2, and 1.0 ± 0.1% for 15-cisB

DOI: 10.1021/acs.jafc.5b05478 J. Agric. Food Chem. XXXX, XXX, XXX−XXX

Article

Journal of Agricultural and Food Chemistry

Figure 2. HPLC spectra of the corresponding peaks of BC in nanoemulsions. Peaks: 1, cis, not identified; 2, 15-cis-BC; 3, 13-cis-BC; 4, 9,15-cis-BC; 5, all-trans-BC; 6, 9-cis-BC.

Figure 1. HPLC chromatogram of BC-loaded nanoemulsion (A, day 0; B, day 30 at 25 °C; C, day 30 at 50 °C). Peaks: 1, cis, not identified; 2, 15-cis-BC; 3, 13-cis-BC; 4, 9,15-cis-BC; 5, all-trans-BC; 6, 9-cis-BC.

BC, 13-cis-BC, all-trans-BC, and 9-cis-BC, respectively. 13-cisBC was the predominant BC cis isomer. Both singlet oxygen quenching27 and thermal energy produce 13-cis as the major cis isomer.28 Because the samples were exposed to light but not high temperatures, the singlet oxygen might be the more probable cause. After storage for 30 days at 25 °C, no other isomers were found. However, two more peaks were found (cis not identified (peak 1) and 9,15-cis-BC (peak 4)) with retention times of 12.91 and 14.38 min, respectively, under storage at 50 °C. The cis isomers also isomerize and the 9- or 15-cis isomers formed the 9,15-cis-BC. all-trans-BC is also formed from isomerization of the cis isomers. Impact of Oils on the Retention of BC. In this study, CO, a highly unsaturated fat, and MCT, a highly saturated fat, were used to compare the influence of lipids on the stability of BC. MCT contains C8:0 and C10:0, 49.5 and 50.3%, respectively, and CO contains C18:1 and C18:2, 32.93 and 53.57%, respectively. Total BC content decreased during 30 days of storage at 25 °C in the dark (Figure 3). all-trans-BC exhibited time-dependent degradation in both oils. The relative amounts of all-trans-BC (retention) were 78.1 and 25.1% for CO and MCT, respectively, after 30 days of storage. Qiu et al.29 reported that there was an inverse proportion between unsaturation degrees of oils and the oxidative stability of BC, consistent with our results. Refined CO may contain some

Figure 3. Retention of total BC (%) relative to initial concentration in nanoemulsions of different carrier oils (CO, corn oil; MCT, mediumchain triglycerides) during 30 days of storage at 25 °C in the dark. Data represent the mean ± STD (n = 3).

tocopherols, carotenoids (lutein and zeaxanthin), and other antioxidants,30 which may inhibit the BC loss but their concentrations are low compared to the fortification levels. However, even small amounts of AT may have an effect as shown by the greater chemical stability of lycopene in nonstripped CO emulsions than in tocopherol-stripped CObased emulsions.31 CO was chosen as the carrier oil for BC nanoemulsions in the following experiments. Physical Stability of BC Nanoemulsion. Particle diameter profile and polydispersity index (PDI) were used to evaluate the physical stability of the caseinate stabilized CO

Table 1. Characterization of BC cis/trans Isomers

a

peak

name

retention time (min)

1 2 3 4 5 6

not identified 15-cis-BC 13-cis-BC 9,15-cis-BC all-trans-BC 9-cis-BC

12.91 13.30 13.70 14.38 15.25 15.89

λ (nm) (in-line) 350, 334, 340, 335, 458, 347,

437 445, 447, 440, 482 452,

470 476 466 477

λ (nm) (reported) 335, 338, 441, 458, 452,

441, 464 446, 476 466 482 476

Q valuea found

Q value reported38−40

0.02 0.40 0.45 0.21 0.06 0.09

0.41 0.46 0.20 0.06 0.09

Q value: the height ratio of the cis peak (330−350 nm) to the main absorption peak. C

DOI: 10.1021/acs.jafc.5b05478 J. Agric. Food Chem. XXXX, XXX, XXX−XXX

Article

Journal of Agricultural and Food Chemistry nanoemulsions during 30 days of storage at 25 and 50 °C (Figure 4). The initial mean particle diameters were 174−176

Figure 4. Particle size distribution of BC-loaded nanoemulsion encapsulated with SC (2.0%, w/w) at 0 days (1), 30 days at 25 °C (2), and 30 days at 50 °C (3) in the absence of natural antioxidant (control). CO was used as carrier oil.

nm for all BC nanoemulsions (control, fortified with AA or AT, respectively). No remarkable differences were observed among all samples, indicating natural antioxidants had no adverse effects on physical stability. Due to the large difference in density between the oil-emulsified droplets and the aqueous continuous phase, the emulsion particles may rise and concentrate at the surface and flocculate or aggregate. During the 30 days of storage at 25 °C, all samples showed an increase in diameter of 10−25 nm (Figure 5). The particle diameters of emulsions stored at 50 °C increased 40−50 nm, and the particle size distribution increased toward larger diameter (Figure 5). After 30 days of storage at 50 °C, a small peak of about 4000−5000 nm diameter was observed for all samples, indicating aggregation or flocculation (Figure 4). Qian et al. also observed the same larger particles aggregates in nanoemulsions during 15 days of storage at 55 °C. The authors suggested that hydrophobic attraction between nanodroplets increased due to the increase of the amounts of nonpolar amino acid groups of β-lactoglobulin of adjacent droplets exposed resulted in aggregation.19 In this study, the disruption of internal hydrophobic interactions and dissociation of colloidal calcium phosphate of casein micelles during high-pressure processing may result in interparticle bridges leading to aggregation and association.32 Although some aggregations occurred, no phase separation or creaming was observed during 30 days of storage in the dark at both temperatures for any samples, suggesting that SC-stabilized BC-loaded nanoemulsions were highly kinetically stabile.33 Impact of Natural Antioxidants on the Degradation of BC. In this study, the highly polyunsaturated fatty acids in CO may contain hydroperoxides that lead to peroxyl or alkoxyl radial that react with BC. Oxidation and isomerization may be the main reasons for the loss of BC.34 The antioxidants protected BC from degradation. The retention rates were 85.2 and 88.2% with AA and AT, respectively, compared to control without antioxidants (78.1%) at 25 °C (Figure 6) (P < 0.05). BC degradation was higher at 50 °C than at 25 °C. The retention of BC improved by 2.4- and 2.8-fold for AA and AT,

Figure 5. Z-average particle diameter changes of BC-loaded nanoemulsions with 0.1% (w/w) L-ascorbic acid or 0.1% (w/w) αtocopherol as antoxidants stored at 25 °C (A) and 50 °C (B) during 30 days of storage in the dark. Data represent the mean ± STD (n = 3). CO was used as carrier oil.

respectively, compared to the control (Figure 6). α-Tocopherol was more effective at preventing BC degradation than Lascorbic acid at both temperatures, supporting previous observations that nonpolar hydrophobic antioxidants are more effective than the polar hydrophilic antioxidants in emulsion delivery systems.35 Aqueous and lipid-soluble antioxidants generally have different mechanisms and location of activity. L-Ascorbic acid is hydrophilic and acts on the surface of a nanodroplet or in the bulk phase acts as a metal ion chelating agent and dissolved oxygen scavenger. α-Tocopherol is a well-known lipid peroxyl radical scavenger. α-Tocopherol may react with the CO derived free radicals to protect BC from degradation. Becuase BC degradation mainly occurs on the surface of or inside lipid droplets, hydrophilic L-ascorbic acid is less effective. However, Qian et al. found that L-ascorbic acid was a better antioxidant than vitamin E acetate so that lipophilicity by itself may not increase antioxidant activity.19 Isomerization of BC. The isomerization from all-trans to cis isomers can occur by exposure to light through either the singlet excited state by direct exposure to light, triplet excited state by contact with a photosensitizer, or thermal energy.28 The reverse reaction, isomerization from cis isomers to all-trans also readily occurs. These mechanisms of isomerization may go through radical cation intermediates.14 Quantum calculations show that electrons in the highly conjugated system are labile, and the center bonds have the lowest bond orders. The isomerization of BC in the absence or presence of antioxidants (AA or AT) during 30 days of storage at 25 and 50 °C are D

DOI: 10.1021/acs.jafc.5b05478 J. Agric. Food Chem. XXXX, XXX, XXX−XXX

Article

Journal of Agricultural and Food Chemistry

cis-BC is much faster than that of both 9-cis-BC and 15-cis-BC after heat and illumination. The results were in accordance with theoretical and practical studies about the enthalpies or activation energies of BC isomers.11,37 The rotational barrier for the conversion of the all-trans-BC to its mono-cis isomers was in the order 13-cis-BC < 15-cis-BC < 9-cis-BC,37 suggesting the conversion from all-trans-BC to 13-cis-BC was relatively easy and energy needed was least, compared to 15-cis-BC and 9-cis-BC. The amount of all-trans-BC was appreciably improved by AA (74.6%) and AT (76.7%), compared to control (66.9%), after 30 days of storage at 25 °C (P < 0.05). The results indicated that the conversion from all-trans-BC to its isomers was inhibited with antioxidants. Storage at 50 °C accelerated the conversion from all-transBC to 15-cis-, 13-cis-, and 9-cis-BC. The all-trans-BC decreased to 63.9, 69.7, and 79.7% of their initial contents for control, AA, and AT, respectively, in 2 days (P < 0.05). The ratios of alltrans-BC/total BC nanoemulsion (control) were 81.6 and 62.2% at 25 and 50 °C after 30 days of storage, respectively. The concentration of 9-cis-BC was temperature dependent. 9cis-BC concentration was relatively stable after 30 days of storage at 25 °C (Table 2). However, increased temperature significantly pronounced the conversation from all-trans-BC to 9-cis-BC. Compared to initial content, 9-cis-BC was increased by 5.2-, 8.3-, and 8.5-fold, respectivley, for control, AA, and AT after 30 days of storage at 50 °C. Knockaert et al. also found that the concentrations of 9-cis-BC enhanced in carrots with the increase of process temperatures.11 Even though the total amount of 9-cis-BC was increased after 30 days of storage at 50 °C, the ratio of 9-cis-BC/all-trans-BC was decreased. Compared to control (26.5%), the ratio of 9-cis-BC/all-trans-BC declined to 19.5 and 15.8% fortified with AA or AT after 30 days of storage at 50 °C, respectively, indicating that cis isomer formation was inhibited by both antioxidants and the inhibition effect of AT was greater than that of AA. Although 13-cis-BC is the initially most favored cis isomer, rapid isomerization occurs between all isomers and 13-cis-BC appears to be the favored equilibrium product. In conclusion, the BC-loaded O/W nanoemulsions were relatively stable in the presence or absence of natural antioxidants (AA and AT) without creaming and flocculation phenomena during 30 days of storage at 25 and 50 °C. The chemical stability of BC was significantly improved by

Figure 6. Retention of total BC (%) relative to initial concentration in nanoemulsions with 0.1% (w/w) ascorbic acid or 0.1% (w/w) αtocopherol during 30 days of storage at 25 °C (A) and 50 °C (B) in the dark. Data represent the mean ± STD (n = 3). CO was used as carrier oil.

shown in Tables 2 and 3. At 25 °C, no significant increases were observed for 9-cis-BC with or without antioxidants. The concentration of 15-cis-BC increased about 200% in all samples. The 13-cis-BC increased from about 3−4 to 11−12 μg/mL for all treatments. The isomerization rates were in the following order: 13-cis-BC > 15-cis-BC > 9-cis-BC, consistent with the results by Chen et al.,36 who also reported that formation of 13-

Table 2. BC Isomer Concentrations (μg/mL) at Three Conditions (Control, L-Ascorbic Acid, and α-Tocopherol) during 30 Days of Storage at 25 °C in the Dark sample control

L-ascorbic

acid

α-tocopherol

isomer

day 0

day 2

day 9

day 16

day 23

day 30

15-cis-BC 13-cis-BC all-trans-BC 9-cis-BC

0.8 2.9 95.2 1.0

± ± ± ±

0.1 0.1 1.2 0.1

1.3 4.1 91.4 1.1

± ± ± ±

0.1 0.2 2.0 0.1

1.5 6.0 84.2 1.2

± ± ± ±

0.1 0.2 0.7 0.1

1.7 7.9 78.7 1.2

± ± ± ±

0.1 0.1 0.9 0.1

2.5 9.8 70.2 2.0

± ± ± ±

0.1 0.2 1.0 0.1

2.0 11.3 63.7 1.1

± ± ± ±

0.1 0.2 0.7 0.1

15-cis-BC 13-cis-BC all-trans-BC 9-cis-BC

1.0 3.3 94.5 1.0

± ± ± ±

0.1 0.2 1.6 0.1

1.4 4.9 94.4 1.2

± ± ± ±

0.1 0.1 2.7 0.1

1.7 7.7 83.7 1.3

± ± ± ±

0.1 0.4 2.5 0.1

2.0 9.1 80.6 1.3

± ± ± ±

0.1 0.3 1.8 0.1

1.9 11.2 76.9 1.1

± ± ± ±

0.1 0.3 1.6 0.1

1.7 11.3 70.7 1.4

± ± ± ±

0.1 0.3 1.8 0.1

15-cis-BC 13-cis-BC all-trans-BC 9-cis-BC

0.9 3.1 95.0 1.0

± ± ± ±

0.1 0.2 1.1 0.1

1.2 4.7 91.4 1.0

± ± ± ±

0.2 0.1 1.2 0.1

1.7 7.8 85.7 1.2

± ± ± ±

0.1 0.2 2.7 0.1

1.7 8.6 80.5 1.3

± ± ± ±

0.1 0.1 2.7 0.1

2.0 10.8 75.4 1.3

± ± ± ±

0.1 0.1 2.4 0.1

1.9 12.2 72.9 1.2

± ± ± ±

0.1 0.3 1.9 0.1

E

DOI: 10.1021/acs.jafc.5b05478 J. Agric. Food Chem. XXXX, XXX, XXX−XXX

Article

Journal of Agricultural and Food Chemistry

Table 3. BC Isomer Concentrations (μg/mL) at Three Conditions (Control, L-Ascorbic Acid, and α-Tocopherol) during 30 Days of Storage at 50 °C in the Dark sample control

L-ascorbic

acid

α-tocopherol

isomer

day 0

day 2

day 4

day 6

day 23

day 30

± ± ± ±

0.1 0.1 1.2 0.1

4.4 19.7 60.8 2.8

± ± ± ±

0.2 0.2 1.1 0.1

3.9 20.8 50.9 4.4

± ± ± ±

0.1 0.4 1.6 0.2

3.2 17.6 43.8 4.4

± ± ± ±

0.2 0.2 0.5 0.2

3.2 16.8 40.0 4.6

± ± ± ±

0.1 0.3 1.1 0.2

2.6 14.1 34.4 5.1

± ± ± ±

0.2 0.5 0.6 0.1

1.6 9.9 27.8 4.9

± ± ± ±

0.2 0.4 0.7 0.1

1.0 5.7 19.6 5.2

± ± ± ±

0.1 0.2 0.4 0.7

15-cis-BC 13-cis-BC all-trans-BC 9-cis-BC

1.0 3.3 94.5 1.0

± ± ± ±

0.1 0.2 1.6 0.1

1.4 19.8 66.1 1.2

± ± ± ±

0.1 0.3 1.4 0.1

3.8 20.0 61.3 1.8

± ± ± ±

0.4 1.2 3.9 0.1

4.5 21.6 55.4 3.0

± ± ± ±

0.1 0.6 1.8 0.2

4.7 24.2 54.3 3.3

± ± ± ±

0.2 0.3 3.7 0.2

5.1 22.0 48.4 4.9

± ± ± ±

0.2 0.3 1.8 0.2

4.1 20.7 48.4 8.2

± ± ± ±

0.2 0.3 1.5 0.7

3.4 19.4 43.7 8.5

± ± ± ±

0.2 0.9 0.8 0.6

15-cis-BC 13-cis-BC all-trans-BC 9-cis-BC

0.9 3.1 95.0 1.0

± ± ± ±

0.1 0.2 1.1 0.1

3.6 17.9 75.8 1.2

± ± ± ±

0.2 0.9 1.9 0.1

3.6 19.2 73.1 1.9

± ± ± ±

0.2 0.5 2.0 0.1

3.9 20.0 69.0 2.9

± ± ± ±

0.2 0.7 2.7 0.1

4.4 21.6 62.8 3.7

± ± ± ±

0.1 0.6 1.4 0.1

4.9 22.2 58.7 4.7

± ± ± ±

0.2 1.7 2.1 0.2

5.3 22.4 55.4 7.1

± ± ± ±

0.1 0.4 1.2 0.8

5.2 21.5 52.5 8.3

± ± ± ±

0.1 0.8 2.0 0.6

(6) McClements, D. J.; Xiao, H. Potential biological fate of ingested nanoemulsions: influence of particle characteristics. Food Funct. 2012, 3, 202−220. (7) Liang, R.; Shoemaker, C. F.; Yang, X.; Zhong, F.; Huang, Q. Stability and bioaccessibility of β-carotene in nanoemulsions stabilized by modified starches. J. Agric. Food Chem. 2013, 61, 1249−1257. (8) Mao, L.; Yang, J.; Xu, D.; Yuan, F.; Gao, Y. Effects of homogenization models and emulsifiers on the physicochemical properties of β-carotene nanoemulsions. J. Dispersion Sci. Technol. 2010, 31, 986−993. (9) Chandler, L. A.; Schwartz, S. J. Isomerization and losses of transβ-carotene in sweet potatoes as affected by processing treatments. J. Agric. Food Chem. 1988, 36, 129−133. (10) Imsic, M.; Winkler, S.; Tomkins, B.; Jones, R. Effect of storage and cooking on β-carotene isomers in carrots (Daucus carota L. cv. ‘Stefano’). J. Agric. Food Chem. 2010, 58, 5109−5113. (11) Knockaert, G.; Pulissery, S. K.; Lemmens, L.; Van Buggenhout, S.; Hendrickx, M.; Van Loey, A. Carrot β-carotene degradation and isomerization kinetics during thermal processing in the presence of oil. J. Agric. Food Chem. 2012, 60, 10312−10319. (12) Vásquez-Caicedo, A. L.; Schilling, S.; Carle, R.; Neidhart, S. Effects of thermal processing and fruit matrix on β-carotene stability and enzyme inactivation during transformation of mangoes into purée and nectar. Food Chem. 2007, 102, 1172−1186. (13) Fujii, R.; Furuichi, K.; Zhang, J.-P.; Nagae, H.; Hashimoto, H.; Koyama, Y. Cis-to-trans isomerization of spheroidene in the triplet state as detected by time-resolved absorption spectroscopy. J. Phys. Chem. A 2002, 106, 2410−2421. (14) Gao, G.; Wei, C. C.; Jeevarajan, A. S.; Kispert, L. D. Geometrical isomerization of carotenoids mediated by cation radical/dication formation. J. Phys. Chem. 1996, 100, 5362−5366. (15) Nagao, A.; Olson, J. A. Enzymatic formation of 9-cis, 13-cis, and all-trans retinals from isomers of beta-carotene. FASEB J. 1994, 8, 968−973. (16) Deming, D. M.; Teixeira, S. R.; Erdman, J. W. All-trans βcarotene appears to be more bioavailable than 9-cis or 13-cis βcarotene in gerbils given single oral doses of each isomer. J. Nutr. 2002, 132, 2700−2708. (17) Yi, J.; Li, Y.; Zhong, F.; Yokoyama, W. The physicochemical stability and in vitro bioaccessibility of beta-carotene in oil-in-water sodium caseinate emulsions. Food Hydrocolloids 2014, 35, 19−27. (18) Yi, J.; Zhang, Y.; Liang, R.; Zhong, F.; Ma, J. Beta-carotene chemical stability in nanoemulsions was improved by stabilized with beta-lactoglobulin−catechin conjugates through free radical method. J. Agric. Food Chem. 2015, 63, 297−303. (19) Qian, C.; Decker, E. A.; Xiao, H.; McClements, D. J. Inhibition of β-carotene degradation in oil-in-water nanoemulsions: influence of oil-soluble and water-soluble antioxidants. Food Chem. 2012, 135, 1036−1043.

AUTHOR INFORMATION

Corresponding Authors

*(J.Y.) Phone: 86-755-26557377. Fax: 86-755-26536141. Email: [email protected]. *(L.Z.) Phone: 86-755-26733095. Fax: 86-755-26536141. Email: [email protected]. Funding

This work was supported by the Shenzhen Dedicated Funding of Strategic Emerging Industry Development Program (JCYJ20140418091413576, CXZZ20150430093131635). Notes

The authors declare no competing financial interest.



ABBREVIATIONS USED BC, β-carotene; SC, sodium caseinate; WPI, whey protein isolate; CO, corn oil; AA, L-ascorbic acid; AT, α-tocopherol; PB, phosphate buffer; Dz, Z-average particle diameter; O/W, oil-in-water; EDTA, ethylenediaminetetraacetic acid; OSS, octenylsuccinate starch; MCT, medium-chain triglycerides; PDI, polydispersity index; RP-HPLC, reverse phase highperformance liquid chromatography



day 16

0.8 2.9 95.2 1.0

antioxiants AA and AT. The conversion of all-trans-BC to cis isomers was partly inhibited by natural antioxiants. The results may provide some useful information in controlling the isomerizaiton of all-trans-BC. The results of this study may be useful in the designing and delivery of carotenoids in nanoemulsions for delivery in foods.



day 9

15-cis-BC 13-cis-BC all-trans-BC 9-cis-BC

REFERENCES

(1) Grune, T.; Lietz, G.; Palou, A.; Ross, A. C.; Stahl, W.; Tang, G.; Thurnham, D.; Yin, S.-a.; Biesalski, H. K. β-Carotene is an important vitamin A source for humans. J. Nutr. 2010, 140, 2268S−2285S. (2) Akhtar, S.; Ahmed, A.; Randhawa, M. A.; Atukorala, S.; Arlappa, N.; Ismail, T.; Ali, Z. Prevalence of vitamin A deficiency in South Asia: causes, outcomes, and possible remedies. J. Health Popul. Nutr. 2013, 31, 413−423. (3) Krinsky, N. I.; Johnson, E. J. Carotenoid actions and their relation to health and disease. Mol. Aspects Med. 2005, 26, 459−516. (4) Huang, Q.; Yu, H.; Ru, Q. Bioavailability and delivery of nutraceuticals using nanotechnology. J. Food Sci. 2010, 75, R50−R57. (5) Yi, J.; Zhong, F.; Zhang, Y.; Yokoyama, W.; Zhao, L. Effects of lipids on in vitro release and cellular uptake of β-carotene in nanoemulsion-based delivery systems. J. Agric. Food Chem. 2015, 63, 10831−10837. F

DOI: 10.1021/acs.jafc.5b05478 J. Agric. Food Chem. XXXX, XXX, XXX−XXX

Article

Journal of Agricultural and Food Chemistry (20) Guan, Y.; Wu, J.; Zhong, Q. Eugenol improves physical and chemical stabilities of nanoemulsions loaded with β-carotene. Food Chem. 2016, 194, 787−796. (21) Ribeiro, H. S.; Guerrero, J. M. M.; Briviba, K.; Rechkemmer, G.; Schuchmann, H. P.; Schubert, H. Cellular uptake of carotenoid-loaded oil-in-water emulsions in colon carcinoma cells in vitro. J. Agric. Food Chem. 2006, 54, 9366−9369. (22) Brewer, M. S. Natural antioxidants: sources, compounds, mechanisms of action, and potential applications. Compr. Rev. Food Sci. Food Saf. 2011, 10, 221−247. (23) Palozza, P.; Krinsky, N. I. β-Carotene and α-tocopherol are synergistic antioxidants. Arch. Biochem. Biophys. 1992, 297, 184−187. (24) Yi, J.; Fan, Y.; Yokoyama, W.; Zhang, Y.; Zhao, L. Characterization of milk proteins−lutein complexes and the impact on lutein chemical stability. Food Chem. 2016, 200, 91−97. (25) Yi, J.; Lam, T. I.; Yokoyama, W.; Cheng, L. W.; Zhong, F. Betacarotene encapsulated in food protein nanoparticles reduces peroxyl radical oxidation in Caco-2 cells. Food Hydrocolloids 2015, 43, 31−40. (26) Yi, J.; Lam, T. I.; Yokoyama, W.; Cheng, L. W.; Zhong, F. Cellular uptake of β-carotene from protein stabilized solid lipid nanoparticles prepared by homogenization−evaporation method. J. Agric. Food Chem. 2014, 62, 1096−1104. (27) Stahl, W.; Sies, H. Physical quenching of singlet oxygen and cistrans isomerization of carotenoids. In Carotenoids in Human Health; Annals of the New York Academy of Sciences 691; Canfield, L. M., Krinsky, N. I., Olson, J. A., Eds.; Wiley, 1993; pp 10−19.10.1111/ j.1749-6632.1993.tb26153.x (28) Kuki, M.; Koyama, Y.; Nagae, H. Triplet-sensitized and thermal isomerization of all-trans, 7-cis, 9-cis, 13-cis and 15-cis isomers of betacarotene: configurational dependence of the quantum yield of isomerization via the T1 state. J. Phys. Chem. 1991, 95, 7171−7180. (29) Qiu, D. A. N.; Shao, S.-X.; Zhao, B. O.; Wu, Y.-C.; Shi, L.-F.; Zhou, J.-C.; Chen, Z.-R. Stability of β-carotene in thermal oils. J. Food Biochem. 2012, 36, 198−206. (30) Carpenter, A. P. Determination of tocopherols in vegetable oils. J. Am. Oil Chem. Soc. 1979, 56, 668−671. (31) Boon, C. S.; Xu, Z.; Yue, X.; McClements, D. J.; Weiss, J.; Decker, E. A. Factors affecting lycopene oxidation in oil-in-water emulsions. J. Agric. Food Chem. 2008, 56, 1408−1414. (32) Dickinson, E. Structure formation in casein-based gels, foams, and emulsions. Colloids Surf., A 2006, 288, 3−11. (33) Tadros, T.; Izquierdo, P.; Esquena, J.; Solans, C. Formation and stability of nano-emulsions. Adv. Colloid Interface Sci. 2004, 108−109, 303−318. (34) Boon, C. S.; McClements, D. J.; Weiss, J.; Decker, E. A. Factors influencing the chemical stability of carotenoids in foods. Crit. Rev. Food Sci. Nutr. 2010, 50, 515−532. (35) McClements, D. J.; Decker, E. A. Lipid oxidation in oil-in-water emulsions: impact of molecular environment on chemical reactions in heterogeneous food systems. J. Food Sci. 2000, 65, 1270−1282. (36) Chen, B. H.; Chen, T. M.; Chien, J. T. Kinetic model for studying the isomerization of alpha- and beta-carotene during heating and illumination. J. Agric. Food Chem. 1994, 42, 2391−2397. (37) Guo, W.-H.; Tu, C.-Y.; Hu, C.-H. Cis−trans isomerizations of βcarotene and lycopene: a theoretical study. J. Phys. Chem. B 2008, 112, 12158−12167. (38) Heymann, T.; Heinz, P.; Glomb, M. A. Lycopene inhibits the isomerization of β-carotene during quenching of singlet oxygen and free radicals. J. Agric. Food Chem. 2015, 63, 3279−3287. (39) Heymann, T.; Westphal, L.; Wessjohann, L.; Glomb, M. A. Growing and processing conditions lead to changes in the carotenoid profile of spinach. J. Agric. Food Chem. 2014, 62, 4960−4967. (40) Liu, S.-C.; Lin, J.-T.; Yang, D.-J. Determination of cis- and transα- and β-carotenoids in Taiwanese sweet potatoes (Ipomoea batatas (L.) Lam.) harvested at various times. Food Chem. 2009, 116, 605− 610.

G

DOI: 10.1021/acs.jafc.5b05478 J. Agric. Food Chem. XXXX, XXX, XXX−XXX

Thermal Degradation and Isomerization of β-Carotene in Oil-in-Water Nanoemulsions Supplemented with Natural Antioxidants.

The goal of this study was to see the impact on the retention and isomerization of encapsulated β-carotene (BC) in nanoemulsions fortified with natura...
418KB Sizes 0 Downloads 12 Views