Vitamin C,provitamin A carotenoids,and other carotenoids in high-pressurized orange juice during refrigerated storage

Vitamin C, provitamin A carotenoids, and other carotenoids were measured in freshly squeezed juices from oranges (Citrus sinensis L. var. Valencia late) that were subjected to high-pressure (HP) treatment. Also, the stability of these compounds was studied during refrigerated storage at 4 degrees C. HP treatment is an alternative to heat preservation methods for foods; therefore, it is essential to assess the impact of HP on bioactive compounds. Several processes that combine HP treatment with heat treatment for various time periods were assayed: T0, fresh juice (without treatment); T1, 100 MPa/60 degrees C/5 min; T2, 350 MPa/30 degrees C/2.5 min; T3, 400 MPa/40 degrees C/1 min. Fresh and treated samples were kept refrigerated (4 degrees C) over 10 days. After application of HP and during the refrigeration period, the qualitative and quantitative determination of vitamin C, provitamin A carotenoids (beta- and alpha-carotene; beta- and alpha-cryptoxanthin), and the xanthophylls zeaxanthin and lutein was achieved by high-performance liquid chromatography. T1 and T3 juices showed a decrease in ascorbic acid and total vitamin C just after HP treatment (D0) compared with T0 juices. On the contrary, T2 juices, just after HP treatment (D0), had the same levels of both compounds compared to untreated juices. T1, T2, and T3 treatments led to an increase in the extraction of carotenoids and provitamin A carotenoids. Total carotenoid content after the 10-day refrigerated storage period resulted in no significant quantitative changes in T1 juices, whereas in T2 and T3 juices small losses were found at the end of the storage period (20.56 and 9.16%, respectively). These losses could be influenced by the depleted protection of vitamin C toward carotenoid oxidation during the same period. A similar trend was found in provitamin A carotenoids for the different treated juices.     

Relationship between gamma-glutamyl transpeptidase activity and garlic greening, as controlled by temperature

It was established that storage at low temperature (less than 10 degrees C) was required for garlic greening occurring either during processing or in the course of "Laba" garlic preparation while storage at high temperature (higher than 20 degrees C) inhibited its occurrence. However, the reason for this observation is unclear. To obtain insights into a tie connected between storage temperature and garlic greening, it was detected if the gamma-glutamyl transpeptidase (GGT) activity correlated with garlic greening because the activity of this enzyme is very sensitive to storage temperature. Results showed that garlic puree (which was prepared from fresh garlic) turned green upon addition of GGT but the color of garlic puree remained unchanged when either water or heat-treated GGT (which has no activity due to heat treatment) was used, a result giving a positive answer to the above proposal. Subsequently, to further clarify the relationship between the GGT activity and garlic greening, the GGT activity, the degree of garlic greening, and the concentration of total thiosulfinates in garlic bulbs were determined respectively after the garlic bulbs had been stored at 4 degrees C for up to 59 days followed by storage at 35 degrees C for up to 22 days. It was found that cold storage facilitated the GGT activity whereas warm storage inhibited the activity of this enzyme, just like the effect of storage temperature on greening, indicating that the increase of GGT activity could be a direct factor resulting in garlic greening. Consistent with this conclusion, the concentration of total thiosulfinates (the color developers) in garlic purees likewise exhibited a reversible change by moving garlic bulbs from one low storage temperature to a higher one; namely, it increased with increasing storage time during storage at 4 degrees C while decreasing as storage time increased during storage at 35 degrees C. The present study provided direct evidence that the GGT is involved in garlic greening.     

Protein and lipid oxidation during frozen storage of rainbow trout (Oncorhynchus mykiss)

This study aimed at investigating protein and lipid oxidation during frozen storage of rainbow trout. Rainbow trout fillets were stored for 13 months at -20, -30, or -80 degrees C, and samples were analyzed at regular intervals for lipid and protein oxidation markers. Lipid oxidation was followed by measuring lipid hydroperoxides (PV), as well as secondary oxidation products (volatiles) using dynamic headspace GC-MS. Free fatty acids (FFA) were measured as an estimation of lipolysis. Protein oxidation was followed using the spectrophotometric determination of protein carbonyls and immunoblotting. Significant oxidation was observed in samples stored at -20 degrees C, and at this temperature lipid and protein oxidation seemed to develop simultaneously. FFA, PV, and carbonyls increased significantly for the fish stored at -20 degrees C, whereas the fish stored at -30 and -80 degrees C did not show any increase in oxidation during the entire storage period when these methods were used. In contrast, the more sensitive GC-MS method used for measurement of the volatiles showed that the fish stored at -30 degrees C oxidized more quickly than those stored at -80 degrees C. Detection of protein oxidation using immunoblotting revealed that high molecular weight proteins were oxidized already at t = 0 and that no new protein oxidized during storage irrespective of the storage time and temperature. The results emphasize the need for the development of more sensitive and reliable methods to study protein oxidation in order to gain more explicit knowledge about the significance of protein oxidation for food quality and, especially, to correlate protein oxidation with physical and functional properties of foods.     

Effects of lipase, lipoxygenase, peroxidase, and rutin on quality deteriorations in buckwheat flour

To investigate the effects of changes in lipase, lipoxygenase, peroxidase (POX), and rutin concentrations on the quality of buckwheat flour, 14 buckwheat varieties were stored for 0, 4, 10, and 30 days at 5 or 20 degrees C. During the storage period, lipase activity correlated to pH (significantly negative) and water-soluble acid (WSA) (significantly positive). The lipoxygenase 1 protein concentration had a negative correlation to WSA (significant at 0 and 4 storage days at 5 degrees C and at 0 and 10 storage days at 20 degrees C). POX had significant correlation to pH and peroxide value (POV) at 5 degrees C, whereas it was not significant at 20 degrees C. The rutin concentration had negative correlations to WSA (significant at 30 days of storage at 5 degrees C and at 4 days of storage at 20 degrees C). Thus, lipase activity plays an important role that relates to lipid degradation in quality deterioration of buckwheat flour.     

Impact of postharvest disease control methods and cold storage on volatiles, color development and fruit quality in ripe 'kensington pride' mangoes

Postharvest diseases of mango fruit (Mangifera indica L.) cause economic losses during storage and can be controlled by chemical, physical, or biological methods. This study investigated the effects of different physical and/or chemical disease control methods on production of volatiles, color development and other quality parameters in ripe 'Kensington Pride' mango fruit. Hard mature green mango fruit were harvested from an orchard located at Carnavon, Western Australia. The fruit were heat-conditioned (8 h at 40 +/- 0.5 degrees C and 83.5 +/- 0.5% RH), dipped in hot water (52 degrees C/10 min), dipped in prochloraz (Sportak 0.55 mL x L(-1)/5 min), dipped in hot prochloraz (Sportak 0.55 mL x L(-1) at 52 degrees C/5 min), dipped in carbendazim (Spin Flo 2 mL x L(-1)/5 min), and dipped in hot carbendazim (Spin Flo 2 mL x L(-1) at 52 degrees C/5 min). Nontreated fruit served as control. Following the treatments, the fruit were air-dried and kept in cold storage (13 +/- 0.5 degrees C) for three weeks before being ripened at 21 +/- 1 degrees C. The ripe pulp of the fruit that was treated with hot prochloraz or carbendazim at ambient and high temperatures showed enhanced concentrations of volatiles, while heat conditioning and hot water dipping did not significantly affect the volatile development. Ripening time, and color development were measured daily while disease incidence and severity, weight loss, firmness, and concentrations of soluble solids, titratable acidity, ascorbic acid, total carotenoids, and volatiles were determined at the eating soft ripe stage. Hot water dipping or fungicide treatments (at ambient or at a high temperature) reduced postharvest diseases incidence and severity. Fruit quality (soluble solids concentration, titratable acidity, ascorbic acid and total caretonoids) was not substantially affected by any of the treatments.     

NMR signal analysis to characterize solid, aqueous, and lipid phases in baked cakes

Proton mobility was studied in molecular fractions of some model systems and of cake using a 1H nuclear magnetic resonance (NMR) relaxation technique. For cake, five spin-spin relaxation times (T2) were obtained from transverse relaxation curves: T2 (1) approximately 20 micros, T2 (2) approximately 0.2 ms, T2 (3) approximately 3 ms, T2 (4) approximately 50 ms, and T2 (2) approximately 165 ms. The faster component was attributed to the solid phase, components 2 and 3 were associated with the aqueous phase, and the two slowest components were linked to the lipid phase. After cooking, the crust contained more fat but less water than the center part of the cake. The amount of gelatinized starch was lower in the crust, and water was more mobile due to less interaction with macromolecules. This preliminary study revealed different effects of storage on the center and crust.     

Effect of cold storage and packaging material on the major aroma components of sweet cream butter

The major aroma compounds of commercial sweet cream AA butter quarters were analyzed by GC-olfactometry and GC-MS combined with dynamic headspace analysis (DHA) and solvent-assisted flavor evaporation (SAFE). In addition, the effect of long-term storage (0, 6, and 12 months) and type of wrapping material (wax parchment paper vs foil) on the aroma components and sensory properties of these butters kept under refrigerated (4 degrees C) and frozen (-20 degrees C) storage was evaluated. The most intense compounds in the aroma of pasteurized AA butter were butanoic acid, delta-octalactone, delta-decalactone, 1-octen-3-one, 2-acetyl-1-pyrroline, dimethyl trisulfide, and diacetyl. The intensities of lipid oxidation volatiles and methyl ketones increased as a function of storage time. Refrigerated storage caused greater flavor deterioration compared with frozen storage. The intensity and relative abundance of styrene increased as a function of time of storage at refrigeration temperature. Butter kept frozen for 12 months exhibited lower styrene levels and a flavor profile more similar to that of fresh butter compared to butter refrigerated for 12 months. Foil wrapping material performed better than wax parchment paper in preventing styrene migration into butter and in minimizing the formation of lipid oxidation and hydroxyl acid products that contribute to the loss of fresh butter flavor.     

冷藏和冻藏对牦牛瘤胃平滑肌氧化稳定性及加工品质的影响

为探明4℃冷藏和-18℃冻藏对牦牛瘤胃平滑肌脂肪和蛋白质氧化及其加工特性的影响,以PE薄膜和PE真空包装的牦牛瘤胃为研究对象,分别测定其在贮藏过程中的脂肪氧化(硫代巴比妥酸)、蛋白质氧化(羰基值、总巯基、表面疏水性)和加工品质(失水率、蒸煮损失率、剪切力、质构特性)的变化。结果表明,不同贮藏温度和包装方式下的瘤胃均发生了不同程度的脂肪和蛋白质氧化,与薄膜包装相比,真空包装可延缓牦牛瘤胃脂肪和蛋白质氧化的发生,且-18℃冻藏下更为显著。此外,冷(冻)藏条件下不同包装牦牛瘤胃的失水率和蒸煮损失率均显著增大(P<0.05),剪切力值显著降低(P<0.05),硬度先减小后增大,且薄膜包装在冷藏0~5 d和冻藏0~28 d时,其加工特性均优于真空包装。综上表明,2种包装下的牦牛瘤胃在冷(冻)藏过程中均发生了脂肪和蛋白质氧化,但真空包装可以有效地延缓氧化反应的发生。此外,在冷藏0~5 d和冻藏0~28 d时,薄膜包装更有利于改善瘤胃的加工特性,增加其嫩度和弹性,但长时间贮藏会导致瘤胃加工特性下降,冷藏条件下薄膜包装瘤胃的变化表现最为显著。本研究可为瘤胃贮藏过程中食用品质的控制提供参考。     

Changes in polyphenolic content and radical-scavenging activity of sweet potato (Ipomoea batatas L.) during storage at optimal and low temperatures

Polyphenolic content and radical-scavenging activities (RSA) of four sweet potato (Ipomoea batatas L.) cultivars were characterized after storage at optimal (15 degrees C) or low temperature (5 degrees C) for 0, 13, 26, and 37 days. The polyphenolic content increased during storage in three cultivars but not in 'Murasakimasari'. The change in 1,1-diphenyl-2-picrylhydrazyl radical-scavenging activity (DPPH-RSA) correlated very well with polyphenolic content. The increases in polyphenolics and the RSA in 'Benimasari' were significantly greater during storage at 5 degrees C than at 15 degrees C. The main polyphenolic components in all cultivars were chlorogenic acid (ChA) and 3,5-di-O-caffeoylquinic acid (3,5-diCQA). ChA level increased more at 5 degrees C than at 15 degrees C, whereas that of 3,5-diCQA was greater at 15 degrees C. Caffeoylquinic acids and RSA in 'Murasakimasari', which contains a large amount of anthocyanin in flesh tissue, were extremely high at the beginning of storage and remained nearly constant or decreased over time. A non-caffeoylquinic acid component that increased during storage, especially in 'J-Red' at 15 degrees C, was purified by successive chromatographic steps. The isolate was identified as caffeoyl sucrose [CSu, 6-O-caffeoyl-(beta- d-fructofuranosyl-(2-->1))-alpha-D-glucopyranoside] by fast atom bombardment-mass spectroscopy (FAB-MS), infrared spectroscopy (IR), and nuclear magnetic resonance spectroscopy (NMR). These results suggest that storage under cultivar-dependent, controlled temperature is one approach for increasing desirable physiologic function associated with RSA of polyphenolic compounds in sweet potato roots.     

Changes in volatile flavor components of guava juice with high-pressure treatment and heat processing and during storage.

The changes in volatile flavor components of guava juice during pressure processing (25 degrees C, 600 MPa, 15 min), heat processing (95 degrees C, 5 min), and storage at 4 and 25 degrees C were evaluated by purge and trap/gas chromatography/mass spectrometry. Esters were the major volatile fraction in guava juice, and alcohols were the second. Pressure processing could maintain the original flavor distribution of the juice. Heat processing (95 degrees C, 5 min) caused decreases in the majority of flavor components in the juice when compared with freshly extracted juice. High-pressure treatment at 600 MPa for 15 min can effectively sterilize microbes but partially inactivate enzymes of guava juice; therefore, volatile components in pressure-treated juice gradually changed during storage periods. Pressure-treated guava juice showed increases in methanol, ethanol, and 2-ethylfuran with decreases in the other components during storage period. Nevertheless, the volatile distribution of 600 MPa treated guava juice was similar to that of freshly extracted juice when stored at 4 degrees C for 30 days.     

Influence of dietary genistein levels on tissue genistein deposition and on the physical, chemical, and sensory quality of rainbow trout, Oncorhynchus mykiss

Genistein, the primary isoflavone in soybean, is one of the chemical components responsible for some of the off-flavors associated with soy-based foods. The potential effects of genistein on the sensory and chemical quality of fish muscle may affect the full utilization of soybean meal as an alternative protein in aquaculture diets. Fingerling trout fed commercial diets containing 0, 500, 1000, or 3000 ppm pure genistein were analyzed after 6 and 12 months of feeding. Genistein was extracted by enzymatic digestions in Tris buffer and quantified by high-performance liquid chromatography. Moisture, fat, protein, ash, and tristimulus color of the fillets were determined. The extent of lipid oxidation occurring in fillets harvested after 12 months of feeding was studied by measurements of thiobarbituric acid reactive substances (TBARS) after 4 and 8 days of refrigerated storage at 4 degrees C. Triangle tests were performed to determine if there were any detectable sensory differences. A dietary genistein content of 3000 ppm led to the deposition of approximately 5.4 pmol of genistein/mg of fillet. Triangle test panelists were unable to detect any significant (p < or = 0.05) differences between the fillets from trout fed the 0 and 3000 ppm genistein concentrations. Moisture, ash, and protein content were influenced by time of harvest, while color was unaffected. TBARS levels on days 4 and 8 were significantly (p < 0.05) higher in the fillets from the 0 ppm genistein level than in fillets from fish fed dietary genistein.     

Methylation methods for the quantitative analysis of conjugated linoleic acid (CLA) isomers in various lipid samples

Precise methylation methods for various chemical forms of conjugated linoleic acid (CLA), which minimize the formation of t,t isomers and allylmethoxy derivatives (AMD) with the completion of methylation, were developed using a 50 mg lipid sample, 3 mL of 1.0 N H(2)SO(4)/methanol, and/or 3 mL of 20% tetramethylguanidine (TMG)/methanol solution(s). Free CLA (FCLA) was methylated with 1.0 N H(2)SO(4)/methanol (55 degrees C, 5 min). CLA esterified in safflower oil (CLA-SO) was methylated with 20% TMG/methanol (100 degrees C, 5 min), whereas CLA esterified in phospholipid (CLA-PL) was methylated with 20% TMG/methanol (100 degrees C, 10 min), followed by an additional reaction with 1.0 N H(2)SO(4)/methanol (55 degrees C, 5 min). Similarly, CLA esterified in egg yolk lipid (CLA-EYL) was methylated by base hydrolysis, followed by reaction with 1.0 N H(2)SO(4)/methanol (55 degrees C, 5 min). These results suggest that for the quantitative analysis of CLA in lipid samples by GC, proper methylation methods should be chosen on the basis of the chemical forms of CLA in samples.     

Chitosan as an edible invisible film for quality preservation of herring and atlantic cod

The effect of chitosan with different molecular weights as coatings for shelf-life extension of fresh fillets of Atlantic cod (Gadus morhua) and herring (Clupea harengus) was evaluated over a 12-day storage at refrigerated temperature (4 +/- 1 degrees C). Three chitosan preparations from snow crab (Chinoecetes opilio) processing wastes, differing in viscosities and molecular weights, were prepared; their apparent viscosities (360, 57, and 14 cP) depended on the deacetylation time (4, 10, and 20 h, respectively) of the chitin precursor. Upon coating with chitosans, a significant (p < or = 0.05) reduction in relative moisture losses of 37, 29, 29, 40, and 32% was observed for cod samples coated with 360 cP chitosan after 4, 6, 8, 10, and 12 days of storage, respectively. Chitosan coating significantly (p < or = 0.05) reduced lipid oxidation as displayed in peroxide value, conjugated dienes, 2-thiobarbituric acid reactive substances and headspace volatiles, chemical spoilage as reflected in total volatile basic nitrogen, trimethylamine, and hypoxanthine, and growth of microorganisms as reflected in total plate count in both fish model systems compared to uncoated samples. The preservative efficacy and the viscosity of chitosan were inter-related; the efficacy of chitosans with viscosities of 57 and 360 cP was superior to that of chitosan with a 14 cP viscosity. Thus, chitosan as edible coating would enhance the quality of seafoods during storage.     

Invertase storage stability and sucrose hydrolysis in solids as affected by water activity and glass transition

Research continues to differentiate the impact of water activity (a(W)) and the glass transition temperature (T(g)) on chemical reactions. Invertase with and without sucrose was incorporated into low and high molecular weight poly(vinylpyrrolidone) model systems (PVP-LMW and PVP-K30, respectively). Invertase activity and sucrose hydrolysis were monitored during storage at a(W) = 0.32-0.75 and 30 degrees C. Pseudo-first-order rate constants for activity loss in PVP-K30 were not different, regardless of the system being glassy or rubbery. In PVP-LMW, invertase stability decreased with increasing a(W). An a(W) > 0.62 was required for sucrose hydrolysis to occur in PVP-LMW. PVP molecular weight appeared to affect invertase stability and reactivity. No dramatic change around T(g) was found in either invertase stability or sucrose hydrolysis, suggesting that T(g)-dictated mobility has a minimal effect on these reactions in amorphous solids.     

Chemical composition, antioxidant properties, and thermal stability of a phytochemical enriched oil from Acai (Euterpe oleracea Mart.)

Phenolic compounds present in crude oil extracts from acai fruit ( Euterpe oleracea) were identified for the first time. The stability of acai oil that contained three concentrations of phenolics was evaluated under short- and long-term storage for lipid oxidation and phenolic retention impacting antioxidant capacity. Similar to acai fruit itself, acai oil isolates contained phenolic acids such as vanillic acid (1,616 +/- 94 mg/kg), syringic acid (1,073 +/- 62 mg/kg), p-hydroxybenzoic acid (892 +/- 52 mg/kg), protocatechuic acid (630 +/- 36 mg/kg), and ferulic acid (101 +/- 5.9 mg/kg) at highly enriched concentrations in relation to acai pulp as well as (+)-catechin (66.7 +/- 4.8 mg/kg) and numerous procyanidin oligomers (3,102 +/- 130 mg/kg). Phenolic acids experienced up to 16% loss after 10 weeks of storage at 20 or 30 degrees C and up to 33% loss at 40 degrees C. Procyanidin oligomers degraded more extensively (23% at 20 degrees C, 39% at 30 degrees C, and 74% at 40 degrees C), in both high- and low-phenolic acai oils. The hydrophilic antioxidant capacity of acai oil isolates with the highest phenolic concentration was 21.5 +/- 1.7 micromol Trolox equivalents/g, and the total soluble phenolic content was 1252 +/- 11 mg gallic acid equivalents/kg, and each decreased by up to 30 and 40%, respectively, during long-term storage. The short-term heating stability at 150 and 170 degrees C for up to 20 min exhibited only minor losses (<10%) in phenolics and antioxidant capacity. Because of its high phenolic content, the phytochemical-enriched acai oil from acai fruit offers a promising alternative to traditional tropical oils for food, supplements, and cosmetic applications.     

Interface characterization and aging of bovine serum albumin stabilized oil-in-water emulsions as revealed by front-surface fluorescence

This paper is devoted to the application of front-surface fluorescence to the study of aging and oxidation of oil-in-water emulsions. Emulsions with two oil droplet sizes were stabilized with bovine serum albumin (BSA) and stored at 37 or 47 degrees C. Lipid oxidation was demonstrated by measurement of hydroperoxides and headspace pentane. Front-surface fluorescence spectra (excitation wavelength = 355 nm) revealed gradual formation of oxidized lipid-protein adducts during the 4 weeks of storage. Fluorescence (excitation = 290 nm) of BSA tryptophanyl residues (Trp) declined during the first day of aging and then decreased slightly and linearly. Fourth-derivative Trp spectra exhibited peaks at 316 and 332 nm. Their evolution indicated that the ratio of Trp in hydrophobic environments to total Trp increased in small droplet emulsions. This suggests that, during lipid oxidation, the adsorbed and nonadsorbed protein underwent various degrees of Trp degradations, polymerization, and aggregation. Thus, front-surface fluorescence makes it possible to evaluate, noninvasively, protein modification and lipid oxidation end-products during processing and storage of food emulsions.     

Cooking effects on water distribution in potatoes using nuclear magnetic resonance relaxation

Continuous low-field (LF) (1)H NMR relaxometry was used to monitor the structural changes during cooking of potatoes with two different dry matter (DM) contents. A principal component analysis of the relaxation decay curves revealed major events related to water mobility during cooking, which occur at 53 and 60 degrees C for potatoes with medium and low DM contents, respectively. Exponential analysis of the relaxation decays reveals two major water populations in the potato: a slow-relaxing (assigned to water in cytoplasm and extracellular cavities) water component, T(22) ( approximately 350-550 ms), and a fast-relaxing component (primarily assigned to water associated with starch and cell walls), T(21) ( approximately 45-65 ms). Significant DM dependent shifts in both the T(21) and T(22) relaxation time constants were observed during cooking, indicating that starch gelatinizes between 53 and 70 degrees C with water exchanging with the hydroxyls of starch (transition in T(21)) and cells start to disrupt with an increase in diffusion volumes at approximately 60 degrees C (transition in T(22)). The study reveals that continuous LF NMR measurement is an excellent and highly sensitive method to study changes in water mobility and water populations during the cooking of potatoes.     

Fluorescence, browning index, and color in infant formulas during storage

Free and total fluorescent compounds, browning index, and color formation were measured in milk-based powdered infant formulas (IF) during 2 years of storage at 20 and 37 degrees C. The excitation spectra from 415 nm emission show three peaks (ex lambda1 = 270 nm, lambda2 = 325/315 nm, lambda3 = 350 nm) and from 347 nm excitation two emission peaks (415 and 520 nm), and no wavelength shifts were observed. Temperature and time of storage exert in general no significant effect on the development of fluorescence emission intensity and browning index. However, an important increase in pentodilysine was recorded-probably because of the iron and ascorbic acid contents of the samples-as well as in browning index in adapted IF. In both IF a color increase (deltaE) throughout storage was observed, this increase being greater in samples stored at 37 degrees C than in those stored at 20 degrees C. The increase in color with time fitted a linear regression model. Color appeared to be an indicator of sufficient sensitivity to measure the effect of temperature or storage time.     

Progress of the Maillard reaction and antioxidant action of Maillard reaction products in preheated model systems during storage

The progress of the Maillard reaction and the effect of Maillard reaction products (MRPs) on lipid oxidation in preheated model systems containing pregelatinized starch, glucose, lysine, and soybean oil have been studied during storage. The samples, either containing all components or excluding one or more of them, were heated at 100 degrees C for 90 min and then stored for up to 180 days at 25 degrees C. Browning indices and lipid oxidation were measured, and the results showed that, in samples containing oil, the Maillard reaction had a significant rate also at room temperature and confirmed the ability of MRPs to retard peroxide formation. Under the conditions adopted the rate of the Maillard reaction was increased by the presence of the oil and its oxidation products. The antioxidant action of the MRPs was also evaluated using a peroxide scavenging test based on crocin bleaching. The results demonstrated that antioxidant activity developed with increased browning of the samples.     

Influence of lipid physical state on the in vitro digestibility of emulsified lipids

The objective of this study was to investigate the influence of the physical state of emulsified lipids on their in vitro digestibility by pancreatic lipase. A 10 wt % tripalmitin oil-in-water emulsion stabilized by sodium dodecyl sulfate (0.9 wt % SDS) was prepared at a temperature (>70 degrees C) above the melting point of the lipid phase (T(m) approximately 60 degrees C). A portion of this emulsion was cooled to a temperature (0 degrees C for 15 min) well below the crystallization temperature of the emulsified lipid (T(c) approximately 22 degrees C) and then warmed to 37 degrees C so as to have completely solid lipid particles. Another portion of the emulsion was directly cooled from 70 to 37 degrees C (which is above the T(c)) to have completely liquid (supercooled) lipid particles. Pancreatic lipase (8 mg/mL) and bile extract (5.0 mg/mL) were then added to each emulsion at 37 degrees C, and the evolution of the particle charge, particle size, appearance, and free fatty acid release were measured over a period of 2 h. It was found that the rate and extent of lipid digestion were higher in the emulsion containing liquid particles but that appreciable lipid digestion still occurred in the emulsion containing solid particles (i.e., >35% lipid digestion after 2 h). These results may have important consequences for controlling the digestion rate of lipids or for developing solid lipid particle delivery systems for lipophilic functional components.