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1.
The effects of salt and pH on copper-catalyzed lipid oxidation in structured lipid-based emulsions were evaluated. Ten percent oil-in-water emulsions were formulated with a canola oil/caprylic acid structured lipid and stabilized with 0.5% whey protein isolate. alpha-Tocopherol and citric acid were added to the emulsions to determine how changes in pH or the addition of NaCl affected their antioxidant activity. The peroxide values and anisidine values of emulsions stored at 50 degrees C were measured over an 8-day period. Increased lipid oxidation occurred in the pH 7.0 emulsions and when 0.5 M NaCl was added to the pH 3.0 samples. Adding alpha-tocopherol, citric acid, or a combination of the two compounds slowed the formation of hydroperoxides and their subsequent decomposition products in pH 3.0 emulsions.  相似文献   

2.
Light-induced oxidation in Havarti cheese (38% fat) stored in the dark and exposed to fluorescent light was evaluated by an array of chemical, physical, and spectroscopic methods. Light-induced changes were noticeable already after short exposure times (<12 h). A clear differentiation between samples stored in the dark and samples exposed to 1000 lx fluorescent light was obtained by means of the following methods: color measurements (a values), peroxide value determinations, and evaluations of volatile oxidation products by solid-phase microextraction gas chromatography (SPME-GC). The expected changes in peroxide values in relation to storage time were not evident. Measuring free radicals by electron spin resonance spectrometry could not be done to distinguish between samples, possibly due to the conversion of radicals during sample preparation. However, significant light-exposure effects on secondary oxidation products, detected by SPME-GC, were noted for 1-pentanol, 1-hexanol, nonanal, and benzaldehyde.  相似文献   

3.
The effects of drying methods, gamma-irradiation, and storage on the carotenoids (capsanthin, capsorubin, zeaxanthin, capsolutein, violaxanthin, beta-carotene, and beta-cryptoxanthin) of paprika were investigated. Sun-dried and dehydrated paprika samples were irradiated in a (60)Co gamma-irradiator at five doses (0, 2.5, 5.0, 7.5, and 10 kGy) in polyethylene bags and stored for 10 months at ambient temperature. Individual carotenoid analyses were carried out on the paprika and fresh red pepper during a 2 month period using the reverse phase HPLC technique. The concentrations of capsanthin and capsorubin, which are responsible for the attractive red color of sun-dried paprika, were higher than those of dehydrated paprika. Higher irradiation doses and a longer storage period resulted in a significant (P < 0.01) reduction of all the carotenoids, except capsorubin. There was no significant (P < 0.05) effect of irradiation dose on capsorubin destruction. The decrease of red carotenoids, for all irradiation treatments, was less than that of the storage period. Even the highest irradiation dose, 10 kGy, caused a 11.1% capsanthin reduction; however, 10 months of storage at the ambient temperature caused a 42.1% reduction of capsanthin. Yellow pigments of paprika (zeaxanthin, capsolutein, violaxanthin, beta-carotene, and beta-cryptoxanthin) were significantly (P < 0.01) decreased by all treatments. These yellow pigments were also found to be at high levels in those sun-dried samples with red pigments. This difference could be caused by the contribution of pigment biosynthesis during the sun-drying period. The most significant pigment reduction was realized in the processing and storage conditions of paprika, rather than in the irradiation process.  相似文献   

4.
A study was conducted to investigate the change in quality attributes of red pepper (paprika) (Capsicum annuum L. var. Km-622) as a function of ripening and some technological factors. Of quality attributes, carotenoids and bioantioxidants (ascorbic acid and tocopherols) have been studied. It was found that the dynamics of fruit ripening with regard to carotenoids and bioantioxidants was influenced to a considerable extent by weather conditions of the production season. A rainy and cool season yielded fruits with more beta-carotene but less diesters of red xanthophylls as compared to those produced in a relatively dry and warm season. The ripening stage at harvest was found to affect the quality of paprika. Harvest at unripe stages (color break or faint red) resulted in a high accumulation of dehydroascorbic acid in the overripe fruits, whereas de novo biosynthesis of carotenoids and tocopherols was partially retarded. Application of pre-drying centrifugation resulted in a marked loss of ascorbic acid, and as a consequence, carotenoid stability was impaired during the storage of ground paprika. Sugar caramelization caused dry pods and ground paprika to retain more pigments and tocopherol as compared to those from control or centrifuged red pepper samples. During the storage of ground paprika, color stability was improved by grinding the seeds with the pericarp.  相似文献   

5.
Dietary conjugated linoleic acid (CLA; 0-2.0%) increased CLA concentrations in liver microsomes and skeletal muscle homogenates from rats. Dietary CLA decreased oleic and arachadonic acid concentrations in both liver microsomes and skeletal muscle. The presence of CLA in liver microsomes had no impact on linoleic acid, arachadonic acid, and alpha-tocopherol oxidation rates. Dietary CLA (2.0%) also did not alter alpha-tocopherol oxidation rates in liver microsomes or muscle homogenates. Formation of malonaldehyde (MDA) in oxidizing liver microsomes decreased with increasing CLA concentration as determined by measurement of thiobarbituric acid-MDA complexes by HPLC. The ability of CLA to decrease MDA formation without impacting other lipid oxidation markers such as the disappearance of fatty acid and alpha-tocopherol suggests that decreased MDA concentration was the result of CLA's ability to lower polyenoic fatty acids such as arachadonic acid. While CLA does not appear to act as an antioxidant, its ability to decrease polyenoic fatty acid concentrations could decrease the formation of highly cytotoxic lipid oxidation products such as MDA.  相似文献   

6.
Changes occurring in the concentrations of alpha-tocopherol, total phenols, and complex phenols linked to 3,4-dihydroxyphenylethanol (fractions FII and FIV) and p-hydroxyphenylethanol (FIII) during storage of virgin olive oil under environmental conditions were studied. Under diffused light, alpha-tocopherol was decomposed by 79% in 4 months, whereas <45% of the phenols were lost during the same period. Among the phenols, FII showed the least stability, and decreased by 72% in 6 months. Total phenols, FIII, and FIV recorded reductions in the range of 57-63% in 6 months. When the oil was stored in the dark, alpha-tocopherol, total phenols, FIII, and FIV exhibited similar profiles of degradation, reducing by 39-45% in the first 6 months and 50-62% in 12 months. FII was the least stable compound in the dark and recorded a loss of 64% in 6 months and 79% in 12 months. The levels of the above antioxidants were further related to peroxide formation. Remaining levels of these compounds at PV = 20 meq/kg ranged between 50 and 73% under diffused light and between 40 and 62% in the dark.  相似文献   

7.
The color of fresh meat is one of the most important quality criteria of raw muscle foods. This red color is principally due to the presence of oxymyoglobin. The present study was undertaken to examine the effect of a diet rich in polyunsaturated fatty acids (PUFA), the addition of NaCl, and the influence of dietary supplementation with vitamin E on calf muscle oxymyoglobin oxidation (color) and lipid peroxidation. Vitamin E was added to the feed at a concentration of 4000 mg/day for 90 days before slaughter. This diet increased the alpha-tocopherol concentration in muscle membrane from 2.6-2.8 to 6.5-7.0 microg/g of fresh weight. It was found that the diet rich in PUFA and, especially, the addition of NaCl increased muscle lipid peroxidation and oxymyoglobin oxidation as indicated by the contents of thiobarbituric acid-reactive substances and substances that impaired color value readings during storage at 4 degrees C. Both undesirable reactions during storage were controlled very efficiently by the presence of a critically high concentration of alpha-tocopherol in the muscle tissues. The findings concerning the antioxidant activity of alpha-tocopherol in this study form additional evidence of its efficient protection against oxidative reactions during storage of muscle tissues and its potential to maintain a high nutritional value in them.  相似文献   

8.
The antioxidant activity of an extract from Teaw (Cratoxylum formosum Dyer) leaves was studied in soybean oil and soybean oil-in-water emulsions. Samples containing the extract or reference antioxidants including chlorogenic acid, which comprises 60% of the Teaw extract, were stored at 60 degrees C and analyzed periodically for peroxide value (PV) and thiobarbituric acid reactive substances (TBARS) to allow both hydroperoxides and hydroperoxide degradation products to be monitored. Chlorogenic acid and the Teaw extract were more effective than alpha-tocopherol in inhibiting lipid oxidation in bulk oil but were less effective in an oil-in-water emulsion in accordance with the polar paradox. The PV/TBARS ratio for oil samples containing chlorogenic acid was higher than for alpha-tocopherol and BHT because chlorogenic acid inhibits both hydroperoxide formation by radical scavenging and hydroperoxide decomposition by metal chelation. The importance of the metal-chelating activity in retarding hydroperoxide decomposition was confirmed by studying the decomposition of oil samples containing added ferric ions. The PV/TBARS ratio was higher for citric acid than for alpha-tocopherol in the presence of added ferric chloride, but the order was reversed in samples lacking ferric chloride. Samples containing added chlorogenic acid gave the highest PV/TBARS ratios both in the presence and absence of ferric ions. The PV/TBARS ratios for the samples containing antioxidants fell rapidly to lower values in a soybean oil-in-water emulsion than in the soybean oil. This was due to increased hydroperoxide decomposition in the emulsion at the same PV. The Teaw extract contained 12% oil-soluble components, which contributed to a slightly higher oil-water partition coefficient than that of chlorogenic acid. The antioxidant activity of the aqueous phase of the Teaw extract was reduced more than that of chlorogenic acid by partitioning of the oil-soluble components into oil, which showed that the less-polar components contributed to the antioxidant activity of the Teaw extract in aqueous media.  相似文献   

9.
Effects of lipoxygenase I-B (LOX)-catalyzed oxidation of linoleic acid on soybean proteins was evaluated by electron spin resonance (ESR) and fluorescence spectroscopy in different model systems in the presence or absence of antioxidants. A strong central singlet signal was detected by ESR spectroscopy and identified as the carbon radical (g value range 2.0041-2.0054). A downfield shoulder attributed to the sulfur radical (g value 2.019-2.028) was also observed. The changes in soybean proteins were accompanied by an increase in fluorescence, indicating the formation of cross-links. Natural antioxidants such as ascorbic acid and alpha-tocopherol as well as synthetic antioxidants butyl hydroxytoluene (BHT) inhibited the development of both the free radical signal and the fluorescence when added to soybean proteins prior to incubation with linoleic acid and lipoxygenase I-B; the central singlet signal attributed to the carbon radical was reduced by 35-65%. This paper clearly indicates direct free radical transfer from oxidizing linoleic acid catalyzed by LOX to soybean proteins.  相似文献   

10.
Various pigment colors were produced by Monascus fermentations with separate addition of 20 amino acids. The color characteristics and structures of the pigment derivatives were investigated. When each amino acid was added to the fermentation broth as a precursor, pigment extracts with different hue and chroma values were obtained depending on the content ratios of yellow, orange, and red colors in the fermentation broth. The yellow and orange pigments were identical regardless of amino acid addition. The red compounds varied on the basis of the type of amino acid added. LC-MS and (1)H and (13)C NMR structural analyses confirmed that the derivative pigments contained the moieties of the added amino acids. L, a, and b values of the CIELAB color system for the derivative pigments were measured. Values of hue and chroma were then calculated. The colors of the derivative pigments were in the range of orangish red to violet red. The hydrophilicities/hydrophobicities of the derivative pigments could be predicted from their log P values, which were estimated using computer programs.  相似文献   

11.
The antioxidant properties of water extracts from Cassia tora L. (WECT) prepared under different degrees of roasting were investigated. The water extracts of unroasted C. tora L. (WEUCT) showed 94% inhibition of peroxidation of linoleic acid at a dose of 0.2 mg/mL, which was higher than that of alpha-tocopherol (82%). Water extracts prepared from C. tora L. roasted at 175 degrees C for 5 min and at 200 degrees C for 5 min exhibited 83% and 82%, respectively, inhibition of linoleic acid peroxidation. This result indicated that the antioxidant activities of WECT decreased with longer roasting time or higher roasting temperature. The IC(50) of WEUCT in liposome oxidation induced by the Fenton reaction was 0.41 mg/mL, which was higher than that of alpha-tocopherol (IC(50) = 0.55 mg/mL). WEUCT also exhibited good antioxidant activity in enzymatic and nonenzymatic microsome oxidative systems. The water extracts of roasted C. tora L. increased in the degree of browning and produced chemiluminescence when compared with the unroasted sample. However, the total polyphenolic compounds of WECT decreased after the roasting process finished. In conclusion, the decrease in the antioxidant activity of water extracts from roasted C. tora L. might have been due to the degradation of Maillard reaction products and the decrease of polyphenolic compounds.  相似文献   

12.
Glutathione was assessed individually, and in combination with ascorbic acid, for its ability to act as an antioxidant with respect to color development in an oxidizing model white wine system. Glutathione was utilized at concentrations normally found in wine (30 mg/L), as well as at concentrations 20-fold higher (860 mg/L), the latter to afford ascorbic acid (500 mg/L) to glutathione ratios of 1:1. The model wine systems were stored at 45 °C without sulfur dioxide and at saturated oxygen levels, thereby in conditions highly conducive to oxidation. Under these conditions the results demonstrated the higher concentration of glutathione could initially provide protection against oxidative coloration, but eventually induced color formation. In the period during which glutathione offered a protective effect, the production of xanthylium cation pigment precursors and o-quinone-derived phenolic compounds was limited. When glutathione induced coloration, polymeric pigments were formed, but these were different from those found in model wine solutions without glutathione. In the presence of ascorbic acid, high concentrations of glutathione were able to delay the decay in ascorbic acid and inhibit the reaction of ascorbic acid degradation products with the wine flavanol compound (+)-catechin. However, on depletion, the glutathione again induced the production of a range of different polymeric pigments. These results highlight new mechanisms through which glutathione can offer both protection and spoilage during the oxidative coloration of a model wine.  相似文献   

13.
Radical scavenging activities of extracts and constituents in Cornus capitata adventitious root cultures were evaluated by using 1,1-diphenyl-2-pycrylhydrazyl (DPPH) and superoxide anion radicals. Inhibitory activity against peroxidation of linoleic acid was assayed by using the thiobarbituric acid (TBA) method. Ethyl acetate and aqueous fractions were prepared from adventitious roots cultured in Murashige-Skoog liquid medium with 0.1 microM Cu(2+) (0.1CuMS) or 10 microM Cu(2+) (10CuMS). The highest scavenging activities on DPPH and superoxide anion radicals were observed in the ethyl acetate fraction from 0.1CuMS. In the inhibitory activity against linoleic acid oxidation, the ethyl acetate fraction from 10CuMS was highest among the fractions tested. The ethyl acetate fraction of adventitious roots cultured in 0.1CuMS contained mainly galloylglucoses (1,2,3,6-tetragalloylglucose and 1,2,3,4,6-pentagalloylglucose). The ethyl acetate fraction of adventitious roots cultured in 10CuMS contained mainly ellagic acid derivatives [3,3'-di-O-methylellagic acid 4-(5"-acetyl)-alpha-L-arabinofuranoside and stenophyllin H1]. Aqueous fractions prepared from both media contained iridoid glycosides (dihydrocornin and cornin). Tetra- and pentagalloylglucoses showed strong inhibitory activities (61.9 and 85.2%, respectively) against linoleic acid oxidation relative to those of butylated hydroxytoluene (BHT) (91.1%) or alpha-tocopherol (49.5%) at 50 microM concentration. Although both ellagic acid derivatives had weak activities (<50%) on DPPH and superoxide anion radical scavenging, 3,3'-di-O-methylellagic acid 4-(5"-acetyl)-alpha-L-arabinofuranoside was stronger (74.7%) than alpha-tocopherol (49.5%) in inhibiting linoleic acid oxidation at 50 microM concentration. Iridoid glycosides exhibited little activity against DPPH and superoxide anion radicals or against oxidation of linoleic acid.  相似文献   

14.
Virgin olive oil samples with similar oxidative stabilities and fatty acid compositions were stored for 24 months. Changes in the lipid substrate were followed by peroxide value and K(232) measurements. HPLC was used to evaluate changes in the alpha-tocopherol, pigment, and squalene contents. Total polar phenol content was measured colorimetrically. The loss of alpha-tocopherol and carotenoids was comparable with that of polar phenol content, suggesting an active participation in autoxidation. The limited role of squalene in autoxidation was further confirmed using an olive oil model and in the presence of alpha-tocopherol. Pheophytin a degradation was high, although spectrometric estimation of chlorophyll content did not indicate so. Evaluation of pheophytin a activity at three different levels of addition on the oil model indicated a concentration-dependent antioxidant role more pronounced at elevated temperatures, which could be partially due to the activity of certain degradation products.  相似文献   

15.
The levels of cholesterol oxidation derivatives (OxChol) in eight commercial species of meat products were examined. These products contained more than 1 mg/100 g of OxChol, and 7beta-hydroxycholesterol + 5beta-epoxycholesterol (111-1092 microg/100 g), 5alpha-epoxycholesterol (80-712 microg/100 g), cholestanetriol (0-368 microg/100 g), and 7-ketocholesterol (708-1204 microg/100 g) were detected. To know the interaction of sodium nitrite supplementation against cholesterol oxidation in meat products, sausage was produced with or without varying levels of sodium nitrite and stored in the refrigerator for 15 days. As a result, cholesterol oxidation in sausage was inhibited by addition of sodium nitrite in a dose-dependent manner. This observation may be associated with inactivation of O(2)(-) radical and stabilization of polyunsaturated fatty acids (PUFAs). In fact, the levels of OxChol in sausage increased, accompanying the decrease of coexisting linoleic acid when sodium nitrite was not added to sausage meat. Thus, cholesterol oxidation in meat products seems to be considarably promoted by the oxidation of coexisting PUFAs. On the other hand, additive apple polyphenol also inhibited linoleic acid oxidation in sausage and then suppressed cholesterol oxidation through its radical scavenging effects. Therefore, apple polyphenol, having a large amount of an oligomer of catechin, may interfere with cholesterol oxidation in meat processing or storage of meat products through its antioxidative action and be useful as a new antioxitant for meat products when it is added to the original meat before processing.  相似文献   

16.
Changes in the concentration of tocopherol, monophenols, o-diphenols, squalene, and polyunsaturated fatty acids in olive oil were evaluated during 1 year at various storage conditions. Samples of two different extra virgin olive oil (EOO), produced in Calabria (Italy), were stored in dark and in colorless bottles, filled up completely or to half, in order to simulate the domestic storage conditions. The extent of oxidation or photooxidation was monitored by periodic measurements of peroxide values and the rate of degradation of alpha-tocopherol, o-diphenols, squalene, and polyunsaturated fatty acids. The quantitative analysis of the constituents has been performed by HPLC-DAD, HPLC-MS, and GC-MS. The main changes in the concentrations of the analyzed compounds were associated with the major oxygen level in the half-empty glass bottles. alpha-Tocopherol was the first molecule to be oxidized (-20% after 2 months, -92% after 12 months). Squalene and o-diphenols were protected in the first months by the presence of alpha-tocopherol, and their content decreased significantly only after 6 and 8 months, respectively, in the half-empty bottles. The concentration of polyunsaturated fatty acids remained almost constant during 8 months for all four different storage conditions; their oxidation started when the level of the antioxidants decreased.  相似文献   

17.
6-O-Palmitoyl L-ascorbate was added to linoleic acid at various molar ratios of the ascorbate to the acid, the mixtures were emulsified with a maltodextrin or gum arabic solution, and the emulsions were spray-dried to produce microcapsules. At higher molar ratios, the oil droplets in the emulsions were smaller, and the oxidative stabilities of the encapsulated linoleic acid were higher for both the maltodextrin- and gum arabic-based microcapsules. 6-O-Capryloyl, caproyl, and lauroyl L-ascorbates, which were synthesized through lipase-catalyzed condensation in acetone, were also used for the microencapsulation of linoleic acid. Except for capryloyl L-ascorbate, the addition of a saturated acyl ascorbate, especially caproyl ascorbate, to linoleic acid was effective for preparing oil droplets of small particle diameter and for suppressing the oxidation of the encapsulated linoleic acid.  相似文献   

18.
A factorial design was used to study the effect of dietary oxidized sunflower oils (fresh, heated at low temperatures, and heated at high temperatures), DL-alpha-tocopheryl acetate (0 or 100 mg/kg), and Zn supplementation (0 or 600 mg/kg) on the composition, oxidative stability, and sensory quality of dark chicken meat with skin from animals fed with a Se supplement (Se-enriched yeast, 0.6 mg of Se/kg). The positional and geometrical isomers of linoleic acid were increased in raw meat from chickens fed oils oxidized at high temperatures. In addition, supplementation with alpha-tocopheryl acetate increased the alpha-tocopherol content, whereas 2-thiobarbituric acid (TBA) values and lipid hydroperoxide content were reduced. Likewise, TBA values, rancid aroma, and rancid flavor also decreased in cooked dark meat. However, none of the dietary factors studied affected consumer acceptability scores of cooked meat. Furthermore, Zn supplementation increased the Se content in raw meat.  相似文献   

19.
Off-flavor and discoloration of meat products result from lipid oxidation and myoglobin (Mb) oxidation, respectively, and these two processes appear to be interrelated. The objective of this study was to investigate their potential interaction in mitochondria and the effects of mitochondrial alpha-tocopherol concentrations on lipid oxidation and metmyoglobin (MetMb) formation in vitro. The addition of ascorbic acid and ferric chloride (AA-Fe(3+)) increased ovine and bovine mitochondrial lipid oxidation when compared with their controls (p < 0.05); MetMb formation also increased with increased lipid oxidation relative to controls (p < 0.05). Reactions containing Mb and mitochondria with greater alpha-tocopherol concentrations demonstrated less lipid oxidation and MetMb formation than mitochondria with lower alpha-tocopherol concentrations. Greater mitochondrial alpha-tocopherol concentration was also correlated with increased mitochondrial oxygen consumption in vitro and with a more pronounced effect at pH 7.2 than at pH 5.6. Relative to controls, succinate addition to bovine mitochondria resulted in increased concentrations of ubiquinol 10 and alpha-tocopherol and decreased lipid and Mb oxidation (p < 0.05). Mitochondrial lipid oxidation was closely related to MetMb formation; both processes were inhibited by alpha-tocopherol in a concentration-dependent manner.  相似文献   

20.
The use of washed cod light muscle minces in mechanistic studies of hemoglobin (Hb)-mediated fish lipid oxidation has largely increased in the past 5 years. Although cod light muscle has a low level of intrinsic lipid oxidation catalysts, a prerequisite for a good oxidation model system, we believe it cannot fully mimic the oxidation kinetics taking place in other fish species being more susceptible to lipid oxidation. The aim of this study was to systematically investigate whether washed mince model systems useful in Hb-mediated oxidation studies could be prepared also from herring (Clupea harengus) and salmon (Salmo salar) light muscles. The kinetics of oxidation in the washed models was measured during ice storage (+/-Hb), and the results were related to compositional differences. Minces from cod, herring, and salmon light muscles were washed 3 times with 3 volumes of water and buffer. A 20 microM portion of Hb and 200 ppm streptomycin was then added, followed by adjustment of pH and moisture to 6.3 and 86%, respectively. Samples with or without Hb were then stored on ice, and oxidation was followed as peroxide value (PV), rancid odor, redness (a*) loss and yellowness (b*). Prior to storage, all minces and models were also analyzed for total lipids, fatty acids, alpha-tocopherol, proteins, Hb, Fe, Cu, and Zn. Hb-mediated lipid oxidation appeared within 2 days on ice in all models. Small differences in the oxidation rates ranked the models as herring > cod > salmon. These differences were ascribed to more preformed peroxides and trace elements in the herring model, and more antioxidants in the salmon model. Controls, without Hb, stayed stable in all cases except herring, where a very slight oxidation appeared, especially if the herring raw material had been prefrozen. In conclusion, fattier fish like dark muscle species and salmonoids are useful for making washed mince model systems and would be a better choice than cod if there is an interest in the oxidation kinetics of such species.  相似文献   

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