In vitro study on antioxidant activities of peanut protein hydrolysate

Peanut protein was hydrolysed with a commercial protease, Alcalase 2.4L, and the resulting hydrolysate was investigated for its antioxidant activities, including the ability to inhibit the autoxidation of linoleic acid, the scavenging effect on the 1,1‐diphenyl‐2‐picrylhydrazyl (DPPH) free radical, the reducing power and the inhibition of liver lipid oxidation. As compared with the peanut protein, peanut protein hydrolysate showed strong inhibition of the autoxidation of linoleic acid, to scavenge DPPH free radical and showed strong reducing power. Moreover, peanut protein hydrolysate also displayed noticeable inhibition of liver lipid autoxidation and lipid oxidation induced by H₂O₂ or Fe²⁺ in vitro. All these effects of the sample were concentration‐dependent. These results suggest that peanut protein hydrolysate could be a suitable natural antioxidant and may be a health food for humans. Copyright © 2006 Society of Chemical Industry     

Effects of NaCl Concentration and Potassium Chloride Substitutions on the Thermal Properties and Lipid Oxidation of Dry‐Cured Pork

The thermal properties of cured meat are important for determining storage life and nutritional quality. However, few studies have focused on the thermal properties of dry‐cured pork, particularly in relation to salt level and type. In order to study the thermal properties of dry‐cured pork, we used differential scanning calorimetry (DSC) to evaluate the net heat energy (enthalpy, ΔH), onset (T_onset), and maximum (T_max) temperatures of different pork cuts salted with mixtures of chloride (NaCl and KCl) salts within the curing and ripening temperature range. Within the curing temperature range (?5 to 20 °C), the T_onset, T_max, and ΔH of cured meat treated with different NaCl : KCl mixtures were generally lower than for fresh meat, which indicates that the addition of NaCl or KCl can reduce the melting of lipids and water (especially lipids), in different pork cuts. Within the ripening temperature range (5 to 50 °C), heat absorption peaks in belly and leg cuts were between 29 and 33 °C. However, no obvious heat absorption peak was found in loin cuts. Compared to non‐KCl substitutions, a slightly higher KCl substitution could significantly (P < 0.05) enhance ΔH values of dry‐cured belly and leg cuts. The likely cause of this phenomenon is that high KCl substitutions promote lipid oxidation (r = 0.98, for belly; r = 0.95, for leg cuts). Therefore, KCl substitution should be no more than 30% (wt/wt), especially for high lipid pork, to prevent excessive melting and oxidation of lipids during the dry‐curing process.     

Effects of Retail Style or Food Service Style Packaging Type and Storage Time on Sensory Characteristics of Bacon Manufactured from Commercially Sourced Pork Bellies

Objectives were to characterize differences in pork bellies that were stored frozen for different durations prior to processing and characterize sensory properties of the bacon derived from those bellies when stored in either retail or food service style packaging. Bellies (n = 102) were collected from 4 different time periods, fresh bellies (never frozen) and bellies frozen for 2, 5, or 7 mo, and manufactured into bacon under commercial conditions. Food service bacon was packaged in oxygen‐permeable polyvinyl lined boxes layered on wax‐covered lined paper and blast frozen (–33 °C) for 45 or 90 d after slicing. Retail bacon was vacuum‐packaged in retail packages and refrigerated (2 °C) in the dark for 60 or 120 d after slicing. At the end of respective storage times after slicing, bacon was analyzed for sensory attributes and lipid oxidation. Off‐flavor and oxidized odor of bacon increased (P < 0.01) with increasing storage time in both packaging types. Lipid oxidation increased (P < 0.01) as storage time increased from day 0 to day 45 in food service packaged bacon from frozen bellies, but was unchanged (P ≥ 0.07) with time in food service packaged bacon from fresh bellies. Lipid oxidation was also unchanged (P ≥ 0.21) over time in retail packaged bacon, with the exception of bellies frozen for 5 mo, which was increased from day 0 to day 90. Overall, off‐flavor, oxidized odor, and lipid oxidation increased as storage time after processing increased. Freezing bellies before processing may exacerbate lipid oxidation as storage time after processing was extended.     

Antioxidant and free radical scavenging potential of Achillea santolina extracts

The antioxidative activities of hydroalcoholic extract of Achillea santolina were investigated employing various established in vitro systems including total antioxidant activity in linoleic acid emulsion system, 1,1-diphenyl-2-picrylhydrazyl (DPPH), superoxide and hydroxyl radicals scavenging, reducing power, and inhibitory effect on protein oxidation as well as the inhibition of Fe²⁺/ascorbate induced lipid peroxidation in rat liver homogenate. Total phenolic and flavonoid content of A. santolina extract (ASE) was also determined by a colorimetric method. The results revealed that ASE has notable inhibitory activity on peroxides formation in linoleic acid emulsion system along with concentration-dependent quenching of DPPH and superoxide radicals. Furthermore, the extract showed both nonsite-specific (Fe²⁺ + H₂O₂ + EDTA) and site-specific (Fe²⁺ + H₂O₂) hydroxyl radical scavenging suggesting potent hydroxyl radical scavenging and chelating ability for iron ions in deoxyribose degradation model. A linear correlation between ASE and the reducing power was also observed (r² = 0.9981). ASE prevents thiobarbituric acid reactive substances formation in Fe²⁺/ascorbate induced lipid peroxidation in rat liver tissue in a dose-dependent manner. Moreover, free radical induced protein oxidation was suppressed significantly by the addition of ASE over a range of concentration. These results clearly demonstrated that A. santolina extract possess a marked antioxidant activity.     

强化高温风干成熟对中式培根脂质氧化和感官品质的影响

以猪五花肉为原料,采用强化高温风干成熟工艺制作中式培根,研究强化高温风干成熟工艺对中式培根脂质氧化和感官品质的影响。结果表明：采用65℃强化高温处理可以显著激活脂肪氧合酶活力(P＜0.05),产品的硫代巴比妥酸值(0.17mg MDA/kg)比对照组降低26.1%、过氧化值降低了45%(P＜0.01),感官评分提高14.0%,说明强化高温可以促进脂质氧化和风味物质积累,降低产品氧化指标;以硫代巴比妥酸值和感官评分为目标函数的综合回归优化工艺结果为强化温度65℃、风干成熟温度18～29.5℃(每天升高1.5℃)、风干相对湿度72%～68.5%(每天降低0.5%)、风干时间8d,此时产品的盐分与水分含量分别为3.56%、52.2%,与感官分析结果有良好的一致性。     

Salvianolic acid B inhibits low‐density lipoprotein oxidation and neointimal hyperplasia in endothelium‐denuded hypercholesterolaemic rabbits

BACKGROUND: Atherosclerosis and restenosis are inflammatory responses involving free radicals and lipid peroxidation and may be prevented/cured by antioxidant‐mediated lipid peroxidation inhibition. Salvianolic acid (Sal B), a water‐soluble antioxidant obtained from a Chinese medicinal herb, is believed to have multiple preventive and therapeutic effects against human vascular diseases. In this study the in vitro and in vivo inhibitory effects of Sal B on oxidative stress were determined. RESULTS: In human aortic endothelial cells (HAECs), Sal B reduced oxidative stress, inhibited low‐density lipoprotein (LDL) oxidation and reduced oxidised LDL‐induced cytotoxicity. Sal B inhibited Cu²⁺‐induced LDL oxidation in vitro (with a potency 16.3 times that of probucol) and attenuated HAEC‐mediated LDL oxidation as well as reactive oxygen species (ROS) production. In cholesterol‐fed New Zealand White rabbits (with probucol as positive control), Sal B intake reduced Cu²⁺‐induced LDL oxidation, lipid deposition in the thoracic aorta, intimal thickness of the aortic arch and thoracic aorta and neointimal formation in the abdominal aorta. CONCLUSION: The data obtained in this study suggest that Sal B protects HAECs from oxidative injury‐mediated cell death via inhibition of ROS production. The antioxidant activity of Sal B may help explain its efficacy in the treatment of vascular diseases. Copyright © 2010 Society of Chemical Industry     

Optimisation of antioxidant hydrolysate production from sweet potato protein and effect of in vitro gastrointestinal digestion

In this study, response surface methodology (RSM) was applied to optimise antioxidant hydrolysate production from sweet potato protein (SPP). The effects of enzyme‐to‐substrate ratio, pH value and reaction temperature on ·OH radical scavenging activity and Fe²⁺‐chelating activity of antioxidant hydrolysates from SPP were investigated. The maximum ·OH radical scavenging activity (40.10%) and Fe²⁺‐chelating activity (74.37%) of SPP hydrolysates (SPPH) were obtained at an enzyme‐to‐substrate ratio of 4%, pH value of 7.8 and reaction temperature of 57 °C, which was in agreement with the predicted value (40.11% and 74.83%, respectively) estimated by RSM. The simulated in vitro gastrointestinal digestion (GID) dramatically modified molecular weights distribution, increased peptide (<3 kDa) concentration and highly retained antioxidant activity of SPPH, indicating potentially utilisation of SPPH as a functional supplement in food system.     

Effectiveness of antioxidant‐impregnated film in retarding lipid oxidation

The effectiveness of an antioxidant‐impregnated film to retard autoxidation of a packaged model product containing linoleic acid, via an evaporation/sorption mechanism, was evaluated as a function of storage time and temperature. The rate of loss of antioxidant from the package film structure was described by a first‐order expression. The first‐order rate constants were dependent on the initial concentration of antioxidant in the film. The rate of loss of 3,5‐di‐tert‐butyl‐4‐hydroxytoluene (BHT) from the package film structure was found to be much higher than the rate of loss of α‐tocopherol at both storage conditions (23 and 45 °C, 50% relative humidity) studied. A freeze‐dried model food product system was developed as the source for the autoxidation of linoleic acid in storage stability studies. The storage stability of this model food system packaged with antioxidant‐impregnated film pouches was evaluated. Hexanal as an index of oxidation from the model product system was collected by a dynamic purge and trap system and quantified by a gas chromatography/mass spectrometry procedure. The BHT‐impregnated laminate pouch showed a notable effectiveness in retarding lipid oxidation of the model product at 45 °C as a function of storage time. The control (non‐antioxidant) and α‐tocopherol‐impregnated laminate pouch structures showed no effect on retarding lipid oxidation of the model product during storage at 45 °C. Copyright © 2004 Society of Chemical Industry     

Inhibition of methyl linoleate autoxidation by phenolics and other related compounds under mild oxidative conditions

Methyl linoleate (MeLo) is a commercially available substrate widely used for studying the inhibitory properties of pure compounds and plant extracts against lipid oxidation. In this paper, 13 phenolic (benzoic and cinnamic acids, aldehydes and derivatives, and flavonoids) and other related compounds (butylated hydroxyanisole, butylated hydroxytoluene and tocopherols) as well as nine complex mixtures rich in phenolics (wines) or tocopherols (soybean oil extracts) were assayed for their inhibitory activity against MeLo autoxidation under mild conditions (40 °C, darkness and atmospheric pressure). Samples were also assayed for their free radical‐scavenging capacity against 2,2‐diphenyl‐1‐picrylhydrazyl (DPPH^?). Protocatechuic aldehyde, a compound that has not been previously evaluated by either of the two methods, showed the highest antioxidant activity. Some variations in the antioxidant ranking for some compounds were found between our results and those obtained by other authors using accelerated conditions for MeLo oxidation. Antioxidant activity of wines and soybean oil extracts was related to their richness in phenolics and tocopherols respectively. Correlation between antioxidant capacity measured by the MeLo and DPPH^? methods was found for wines but not for the other samples studied. Therefore the measure of the free radical‐scavenging capacity of a compound is not always a reliable indicator of its lipid oxidation inhibitory ability. Copyright © 2004 Society of Chemical Industry     

Proteolysis,protein oxidation and protease activity in dry‐cured Xuanwei ham during the salting stages

Twenty‐four experimental dry‐cured Xuanwei hams were salted using a standard method for 90 days. The proteolysis, protein oxidation and protease activities in biceps femoris (BF) and semimembranoesus (SM) muscles of dry‐cured Xuanwei ham were investigated during the salting phase. At the end of salting, the salt content increased to 35.2 g kg^?1 muscle in BF and 54.2 g kg^?1 muscle in SM. During the salting stage, salt soluble proteins were degraded mainly into water soluble proteins that were further broken down to peptides with molecular weights mostly greater than 1 kDa. Although large amounts of smaller peptides and free amino acids were generated, especially when the hams were aged. The carbonyl contents were increased but lower than 1.57 nmol mg^?1 proteins in muscles during the salting stage. The cathepsin B, dipeptidyl peptidase I (DPP I), alanyl (AAP), arginyl (RAP) and leucyl (LAP) aminopeptidase all remained active while salt content strongly inhibited cathepsin L and DPP IV in the first 90 days. The results suggested that the salting process promoted the hydrolysis of proteins, and increased the muscle protein oxidation at a slower rate.     

Beneficial effect of the unsaponifiable matter from rice bran on oxidative stress in vitro compared with α‐tocopherol

Unsaponifiable matter (UM) was prepared from rice bran using n‐hexane extraction followed by removal of its fatty acid methyl ester with supercritical CO₂ under heat‐stable conditions. The UM was made up of 1% of vitamin E isomers, 28% of γ‐oryzanol and 71% of uncharacterized compounds. The aim of this study was to determine the antioxidant activities of the UM, using α‐tocopherol (α‐T) as a positive control, by measuring the Fe³⁺‐reducing antioxidant power (FRAP), 2,2‐diphenyl‐1‐picrylhydrazyl (DPPH^?) free‐radical‐scavenging property and lipid peroxidation in rat liver microsomes. In addition, the effects of the UM on the tert‐butyl hydroperoxide (t‐BOOH)‐induced cytotoxicity in cultured rat hepatocytes were also investigated. In FRAP assay and DPPH^? free‐radical‐scavenging assay, the results were expressed g^?1α‐T or g^?1 UM. The amount of UM used in lipid peroxidation assay and cytotoxicity assay was the amount required to have equal amounts of total vitamin E isomers in the sample and the control α‐T. The UM, as well as α‐T, exhibited significant antioxidant activities in FRAP, radical‐scavenging and membrane‐lipid oxidation. The FRAP value for total vitamin E isomers in the UM (TVEIUM) was 9.1 times higher than that for α‐T. In terms of their capacities to perform radical‐scavenging and lipid peroxidation, both TVEIUM and α‐T showed similar antioxidant activities. In experiments using cultured rat hepatocytes, the t‐BOOH‐induced lactate dehydrogenase release was significantly inhibited by the addition of 63.5 and 160 µg ml^?1 of TVEIUM treatments (84 and 89%, respectively), and that of 63.5 and 160 µg ml^?1 of α‐T treatment (88 and 93%, respectively). The antioxidant function against oxidative stress of the UM prepared from rice bran may extend its use to being a potential dietary supplement. Copyright © 2004 Society of Chemical Industry     

Optimisation of hydrolysis of purple sea urchin (Strongylocentrotus nudus) gonad by response surface methodology and evaluation of in vitro antioxidant activity of the hydrolysate

BACKGROUND: Hydrolysates prepared from sea urchin (Strongylocentrotus nudus) gonad by enzymatic treatment showed strong 1,1‐diphenyl‐2‐picrylhydrazyl radical scavenging activity and reducing power. RESULTS: Hydrolysis of S. nudus gonad by the commercial protease papain was optimised for maximum degree of hydrolysis (DH) and trichloroacetic acid‐soluble peptide index (TCA‐SPI) using response surface methodology. Results showed that the optimal conditions were the following: temperature of 48.83 °C, pH of 6.92, enzyme‐to‐substrate ratio of 3143 U g^?1, and substrate concentration of 83.5 g L^?1. Under these conditions, a DH of 27.96 ± 0.54% and a TCA‐SPI of 57.32 ± 0.63% were obtained. The hydrolysate prepared in the optimal conditions was fractionated by an ultra‐filtration system and the resultant fraction below 10 kDa was found to effectively scavenge hydroxyl radical (EC₅₀ = 13.29 ± 0.33 mg mL^?1) and hydrogen peroxide (EC₅₀ = 16.40 ± 0.37 mg mL^?1), inhibit lipid peroxidation (EC₅₀ = 11.05 ± 0.62 mg mL^?1), chelate Fe²⁺ (EC₅₀ = 7.26 ± 0.44 mg mL^?1), and protect mice macrophages against death induced by tert‐butyl hydroperoxide. CONCLUSION: Hydrolysates prepared from S. nudus gonad have the potential to be applied as natural antioxidant agents. Copyright © 2012 Society of Chemical Industry     

Effect of dietary olive leaves (Olea europaea L.) on lipid and protein oxidation of refrigerated stored n‐3‐enriched pork

The objective of this study was to evaluate the effect of dietary olive leaves versus α‐tocopheryl acetate on lipid and protein oxidation of raw and cooked longissimus dorsi muscle from pigs fed diets supplemented with fish oil. Enrichment of pork with the very long chain n‐3 fatty acids increased (P ≤ 0.05) lipid oxidation in both raw and cooked chops during refrigerated storage, and decreased (P ≤ 0.05) the sensory attributes of the cooked chops, but had no effect (P > 0.05) on protein oxidation of both raw and cooked chops. Dietary olive leaves or α‐tocopheryl acetate had no effect (P > 0.05) on the fatty acid composition but decreased (P ≤ 0.05) lipid oxidation while exerting no effect (P > 0.05) on protein oxidation in both raw and cooked chops during refrigerated storage. In addition, dietary olive leaves at 10 g kg^?1 feed and α‐tocopheryl acetate at 200 mg kg^?1 feed exerted (P ≤ 0.05) a beneficial effect on the sensory attributes of cooked n‐3‐enriched chops.     

KINETIC BEHAVIOR OF SOYBEAN LIPOXYGENASE: A COMPARATIVE STUDY OF THE FREE ENZYME AND THE ENZYME IMMOBILIZED IN AN ALGINATE SILICA SOL‐GEL MATRIX1

Lipoxygenase (LOX) is an enzyme that regioselectively introduces a hydroperoxide into polyunsaturated fatty acids (PUFA). We recently reported a procedure that immobilizes soybean LOX within an alginate sol‐gel matrix. In this study, the kinetic profile of free LOX was compared with that of the sol‐gel immobilized LOX. The temperature dependent activity profile of free LOX was optimal at 25C whereas immobilized LOX had optimal activity over the temperature range of 25–35C. Enzyme activity, measured in aqueous buffer, for both the free and immobilized LOX preparations had K_m values of 2.5 and 1.40 mmoles/L, respectively, and V_max values of 0.056 and 0.02 μmol/min, respectively. The relative rates of oxidation of linoleic acid and acylgfycerols containing linoleoyl residues catalyzed by free and immobilized LOX also were determined The results showed that both free and immobilized LOX favor linoleic acid as a substrate. Relative substrate preference for free LOX was linoleic acid >1‐monolinolein > 1,3‐dilinolein >trilinolein, and for immobilized LOX was linoleic acid >l, 3‐dilinolein >1‐monolinolein >trilinolein. In general, LOX immobilized in alginate silica sol‐gel matrix retained the physical and chemical characteristics of free LOX.     

Effect of caffeic acid on haemoglobin‐mediated lipid and protein oxidation in washed cod mince during ice and frozen storage

BACKGROUND: Little is known about the relation between haemoglobin (Hb)‐mediated lipid and protein oxidation in muscle foods and how these two reactions can be inhibited by naturally occurring antioxidants. This study was aimed at evaluating (1) lipid oxidation and protein oxidation induced by 20 µmol L^?1 Hb during chilled and frozen storage of washed cod mince and (2) the efficiency of 10–1000 ppm (0.063–6.3 mmol L^?1) caffeic acid in preventing these reactions. RESULTS: Addition of 20 µmol L^?1 Hb increased peroxide value (PV), rancid odour, protein carbonylation, protein insolubilisation, redness loss and α‐tocopherol loss in ice‐stored washed cod mince. Since both lipid and protein oxidation developed at the same time, it was not possible to conclude which reaction initiated the other. All studied reactions were efficiently inhibited by ≥ 50 ppm caffeic acid, which could be a result of α‐tocopherol regeneration, general radical scavenging, reduced formation of oxidised Hb forms and/or conformational changes in Hb structure. During frozen storage the only clear effect of Hb was increased PV, and here caffeic acid was less efficient as an antioxidant. CONCLUSION: Hb‐induced lipid and protein oxidation occurred quickly in ice‐stored washed cod mince, and the two reactions could not be separated in time. During frozen storage, Hb caused only limited lipid oxidation. Caffeic acid (≥50 ppm) was an efficient antioxidant during ice storage. Copyright © 2010 Society of Chemical Industry     

The effects of an iron-catalyzed oxidation system on lipids and proteins of dark muscle fish

The effects of a hydroxyl radical-generating system induced by iron catalyzed oxidation (Fe²⁺/H₂O₂) on lipids and proteins of sardine, Atlantic bonito, anchovy and bluefish were investigated. Thiobarbituric acid-reactive substances (TBARs, mg malonaldehyde/kg fish muscle) formation was used to evaluate oxidative damage of the lipid in dark muscle fish due to iron catalyzed oxidation. The amount of TBARs was observed to increase significantly in sardine and anchovy as the incubation time increased, while Atlantic bonito and bluefish reached their maximum values of TBARs within the first 3 h of incubation, and after that did not change (p < 0.05). Carbonyl contents (nmol carbonyl/mg protein) of all fish samples measured as an index of protein oxidation were affected differently by the iron-catalyzed oxidation system during incubation. However, significant increases in the carbonyl groups were detected in sardine, Atlantic bonito and bluefish, but not in anchovy as a result of the long incubation time (5 h) (p < 0.05). When comparing to increases Atlantic bonito showed the maximum increase protein carbonyl. The electrophoretic patterns in the presence and absence of β-mercaptoethanol showed that a loss of proteins generally occurred in all fish at the end of incubation, and the greatest alteration in protein bands was observed in anchovy during Fe²⁺-catalyzed oxidation. The bands above 50 kDa disappeared within the first 1 h of incubation. The loss of protein (both high and low molecular weight) may involve disulfide and non-disulfide covalent linking during the iron catalyzed incubation. These data suggest that an increase in TBARs and fragmentation, and a loss of proteins exposed to iron-catalyzed oxidation may explain the oxidative damage of lipids and proteins which causes quality loss and limits the storage life of dark muscle fish.     

Effect of intensifying high‐temperature ripening on proteolysis,lipolysis and flavor of Jinhua ham

BACKGROUND: The flavor quality of dry‐cured ham comes from proteolysis, lipolysis and lipid oxidation, Maillard reaction and Strecker amino acid degradation. Intense proteolysis, lipolysis and lipid oxidation make major contributions to flavor development of dry‐cured ham. Increasing the temperature in fermenting and ripening could promote these reactions and accelerate flavor development in dry‐cured hams. The specific aroma flavor of Jinhua ham is developed only during long‐time high‐temperature ripening in July and August. Our objective was to effectively shorten the process time by intense high‐temperature ripening based on the flavor and quality features of traditional Jinhua ham. RESULTS: Muscle dehydration rate of 80‐day ripened hams (29.43 ± 1.16%) was higher than that of the traditional process (P < 0.05). The total free fatty acids in ripened hams of 45–80 days were all higher than that of traditional hams (P < 0.05) and the level of TBARS was significantly lower (P < 0.01). The flavor profile of modern‐processed hams was different from that of the traditional Jinhua ham. The contents of carboxylic acids and aldehydes were obviously higher than those of the traditional products (P < 0.05). The results of organoleptic evaluation for flavor and quality showed that 80‐day ripened hams reached the first‐grade level of traditional Jinhua ham. CONCLUSION: Long‐time (25–30 days) intensifying high‐temperature ripening (35–37 °C) could accelerate the proteolysis, lipolysis, lipids oxidation, flavor development and effectively shorten the process time based on the traditional flavor and quality features of dry‐cured ham. Copyright © 2009 Society of Chemical Industry     

Effect of acid whey on physicochemical characteristics of dry‐cured organic pork loins without nitrite

The present study deals with the effect of acid whey (AW) on physicochemical properties of non‐nitrite organic dry‐cured pork loins. The loins were divided into three experimental batches: with the curing mixture (C), with sea salt (S) and with sea salt combined with AW (SW). The evolution of physicochemical properties, colour, fatty acid profile and microbiological quality were assessed at 0, 30 and 90 days of refrigerated storage. Physicochemical parameters of dry‐cured organic loins were significantly (P < 0.01) affected by treatment, storage time and the interaction between them. Sea salt in combination with AW was the most successful at reducing the browning reaction involved in the formation of dark colour in dry‐cured loins. Significant reduction in a* value (P < 0.05) caused by replacement of curing salt by sea salt has been less pronounced in sample with AW. Storage diminished (P < 0.01) initial differences in profile of SFA, MUFA and n‐3 induced by treatment method. AW added to uncured loins was able to protect PUFA against oxidation comparable to nitrite. The highest count of lactic acid bacteria (LAB) in dry‐cured loins with AW was accompanied by their lower pH (P < 0.05).     

Antioxidant activity of natural vitamin E extracted from soybean sludge as assessed by chemiluminescence

The antioxidant activity of natural vitamin E (VE) towards superoxide anion, hydroxyl radical and lipid free radicals was investigated using a chemiluminescence technique. VE was extracted from soybean sludge, where it was present at a concentration of 600 g kg^?1 as determined by HPLC. Superoxide anions, hydroxyl radicals and lipid free radicals were generated by the pyrogallol autoxidation system, the Fenton reaction system and the AAPH‐induced γ‐linolenic acid peroxidation system respectively. VE rapidly scavenged hydroxyl radicals and lipid free radicals. The efficient concentration (EC₅₀) of VE against both was 0.1 mg ml^?1. A reaction time of 6 s was adequate to scavenge hydroxyl radicals and a reaction time of 24 s was enough to scavenge lipid free radicals. However, VE scavenged superoxide anions at a relatively low rate, and the extent of scavenging was less than 20% even after 3 min at a VE concentration of 4.3 mg ml^?1. © 2001 Society of Chemical Industry