Antioxidant properties and shelf‐life extension of fresh‐cut tomatoes stored at different temperatures

BACKGROUND: The feasibility of using modified atmosphere packaging (5 kPa O₂ + 5 kPa CO₂) to maintain the antioxidant properties of fresh‐cut tomatoes during shelf‐life was assessed through storage at different temperatures (5, 10, 15 and 20 °C). Health‐related compounds, antioxidant capacity, microbiological counts, physicochemical parameters and in‐package atmosphere of tomato slices were determined. RESULTS: Initial lycopene, vitamin C and phenolic contents and physicochemical parameters of tomato slices were well maintained for 14 days at 5 °C. Lycopene and total phenolic contents were enhanced over time in tomato slices stored at 15 and 20 °C. However, this increase in antioxidant compounds of fresh‐cut tomatoes during storage may be associated with excessive amounts of CO₂ (R² = 0.5679–0.7328) in the packages due to microbial growth. Although keeping tomato slices at temperatures above 10 °C increased their antioxidant content, the shelf‐life of the product was reduced by up 4 days. CONCLUSIONS: A storage temperature of 5 °C is appropriate for maintaining the microbiological shelf‐life of fresh‐cut tomatoes for up to 14 days and also allows the antioxidant properties of tomato slices to be retained over this period, thus reducing wounding stress and deteriorative changes. Copyright © 2008 Society of Chemical Industry     

An Alternative Method for the Determination of Some of the Antioxidant Phenolics in Varietal Turkish Red Wines

The concentration of eight biologically important phenolic compounds (β‐coumaric acid, gallic acid, ferulic acid, caffeic acid, trans‐resveratrol, quercetin, (+)‐ catechin and (?)‐ epicatechin) of red wines produced on a pilot plant scale were determined using gas chromatography with mass spectrometric detection in the selective ion monitoring mode (GC/MS‐SIM). The procedure involved an easy fractionation and liquid‐liquid extraction method. For derivatization, BSA [N,O‐bis‐trimethylsilyl aceta‐mide] / TMCS was used. The results showed that the p‐coumaric acid, gallic acid, ferulic acid, caffeic acid, trans‐resveratrol, quercetin, (+)‐ catechin and (?)‐epicatechin levels in the wine samples ranged between 2.05 and 4.21 mg/L; 21.78 and 60.83 mg/L; 0.33 and 0.82 mg/L; 1.50 and 4.06 mg/L; 0.96 and 3.93 mg/L; 2.66 and 3.14 mg/L; 8.72 and 11.30 mg/L; 5.50 and 9.58 mg/L, respectively. Although the quercetin and trans‐resveratrol levels of Turkish red wines were similar to previously reported values, (+)‐ catechin and (?)‐ epicatechin levels were lower than the values of red wines originating from other countries.     

Selected bioactivities of Vaccinium berries and other fruit crops in relation to their phenolic contents

Antioxidant activity, urinary tract protective activity, and cardioprotective anti‐platelet effects are among the bioactivities associated with dietary phenolics. These bioactivities were measured in vitro in fruit extracts from seven Vaccinium species and five non‐Vaccinium species to determine their relationship to total phenolic content and to anthocyanin and proanthocyanidin content. Berries belonging to the genus Vaccinium were particularly high in antioxidant activity and urinary tract protective anti‐adhesion activity, while anti‐platelet activity varied among species. There was a positive relationship between antioxidant activity (using the oxygen radical absorbing capacity (ORAC) assay) and both the total phenolic (R² = 0.76) and anthocyanin content (R² = 0.43) of the fruit, although there was no relationship between ORAC and proanthocyanidin content. There were no relationships between anti‐adhesion activity and total phenolic content, anthocyanin content, or proanthocyanidin content. Likewise, no relationships were observed between anti‐platelet activity and total phenolic content, anthocyanin content, or proanthocyanidin content. These results suggest that while antioxidant properties are characteristic of all fruit phenolics, in vitro anti‐adhesion and anti‐platelet bioactivities may be due to less abundant phenolic subgroups. Copyright © 2007 Crown in the right of Canada and Society of Chemical Industry     

An improvised process of isolation,purification of steviosides from Stevia rebaudiana Bertoni leaves and its biological activity

The food industry has traditionally used sugar (sucrose) as a sweetening agent; however the dietary and health demands are continuing to expand the market for sweeteners as an alternative to sucrose. The leaves of Stevia rebaudiana are rich source of glycosides that have sweet taste with low calorific value. The study highlights extraction of steviosides from leaves using pressurised hot water extractor, followed by purification and concentration of the sweet glycosides through ultra (UF) and nano (NF) filtration membrane in obtaining high purity steviosides. After the final purification process the stevioside content was 9.05 g per 100 g and rebaudioside A 0.2 g per 100 g stevia leaf, with total purity of stevioside 97.66% by HPLC at total operation time of 7 h. This process also improved the potency of sweetness and palatability profile when compare with other commercially available steviosides. Thus, the methodology developed establishes simple, in‐expensive and eco‐friendly process in obtaining pure steviosides.     

Antioxidant activity and phenolic content of pressurised liquid and solid–liquid extracts from four Irish origin macroalgae

The efficiency of solid–liquid extraction (SLE) and pressurised liquid extraction (PLE) for the recovery of antioxidant and polyphenols from the Irish macroalgae, Fucus serratus, Laminaria digitata, Gracilaria gracilis and Codium fragile, was assessed using the 2,2‐diphenyl‐1‐picrylhydrazyl (DPPH) and ferric reducing antioxidant power (FRAP) assays and the Folin–Ciocalteu total phenol content (TPC) assay. Fucus serratus had TPC and antioxidant activities thirty times higher than the other species. Solid–liquid extraction cold water (CW_SLE) had the highest TPC (81.17 μg GAE mg^?1 sample) derived from F. serratus, compared with the TPC of 61.12 μg GAE mg^?1 sample for the corresponding PLE extract. For both SLE and PLE extracts, low TPC levels were observed in L. digitata, G. gracilis and C. fragile. The majority of SLE extracts possessed higher FRAP and DPPH activities compared with their PLE counterparts. This study indicates that the high temperatures and pressures in PLE did not enhance the antioxidant activities relative to conventional SLE extraction.     

Polyphenols,ascorbic acid and antioxidant capacity of commercial nutritional drinks,fruit juices,smoothies and teas

Polyphenols of plant origin have received special interest in the last decade because of their potential health benefits. Consequently, many beverages with words ‘antioxidant’ and ‘polyphenols’ have been developed. However, many of the claims are misleading because some beverages so labelled have either no or minimal levels of polyphenols. The objectives of this study were to quantify polyphenols (TPC) and ascorbic acid contents and antioxidant capacity (AOC) of different beverages; identify major polyphenols in beverages that showed higher TPC; correlate the claim on the label with TPC and AOC; and determine the impact of consumer refrigerated storage on TPC and AOC of aronia, blackcurrant and pomegranate juices which contained the most TPC and AOC. Major polyphenols identified from these juices included anthocyanins, myricetin and epicatechin. TPC of aronia, blackcurrant and pomegranate juices was relatively stable during consumer refrigerated storage, even when the juice had been intermittently exposed to air.     

Glucose tolerance and antioxidant activity of spent brewer's yeast hydrolysate with a high content of Cyclo-His-Pro (CHP)

To elevate the Cyclo-His-Pro (CHP) content in yeast, the yeast hydrolysate that was obtained from enzymatic hydrolysis was subjected to various treatments. Flavourzyme-treated hydrolysate showed the highest CHP content (674.0 μg/g) among the various proteases treatments. Ultrafiltration was selected as the best method for concentrating CHP in yeast hydrolysate, based on the yields and CHP contents. In addition, we evaluated the radical scavenge and glucose tolerance of yeast hydrolysate with a high content of CHP. Yeast hydrolysate showed intense scavenging abilities of both 1, 1-diphenyl-2-picrylhydrazyl (DPPH) and 2,2'-azino-bis(3-ethylbenzthiazoline-6-sulphonic acid) (ABTS) radicals. The IC(50) values of yeast hydrolysate on DPPH and ABTS radicals were 1.9 and 0.9 mg/mL, respectively. There were significant differences in glucose level between the diabetes-control and yeast hydrolysate group at 30, 60, 90, and 120 min after injection in a type 1 diabetes model (P < 0.01). Also, there were significant differences in blood glucose levels between the 2 groups at 30, 60, and 100 min after injection in the type 2 diabetes group (P < 0.05). Therefore, it is possible to use the yeast hydrolysate with high levels of CHP as an antioxidative and/or antidiabetic material for the preparation of functional foods. PRACTICAL APPLICATION: This study tried to develop a material containing a high content of CHP using yeast for possible applications of this cyclic dipeptide in the therapy of metabolic disorders. The yeast hydrolysate prepared with Flavourzyme showed a high level of CHP. The hydrolysate with a high content of CHP showed high levels of radical scavenging activities and oral glucose tolerance activity. Therefore, it is possible to use the yeast hydrolysate with high levels of CHP as an antioxidative and/or antidiabetic material for the preparation of functional foods.     

In vitro antioxidant synergism and antagonism between food extracts can lead to similar activities in H2O2‐induced cell death,caspase‐3 and MMP‐2 activities in H9c2 cells

BACKGROUND: The cardio‐health‐promoting activity of some foods may be due to their specific antioxidant content. The antioxidant activity of a mixture of plant extracts has been shown to differ from the activity of the individual extracts. As a result, the activity of the mixture can be described as synergistic, antagonistic or additive. This in vitro study evaluated the relationship between the in vitro antioxidant capacity of mixtures and their bioactivity when cardiomyocytes (H9c2) were challenged with H₂O₂. RESULTS: A mixture of raspberry and adzuki bean extracts produced a synergistic response and a mixture of broccoli and soybean extracts produced an antagonistic response in chemical‐based antioxidant assays. When these extracts were tested in cell cultures, individually and in mixtures, the mixture of raspberry and adzuki bean protected the cardiomyocytes from H₂O₂‐induced cell damage significantly better than the individual extracts. Conversely, the mixture of broccoli and soybean extracts was less effective in protecting H9c2 cells. The synergistic and antagonistic effects of the mixtures in protecting cell damage were brought about by enhanced or reduced ability in attenuating caspase‐3 and matrix metalloproteinase‐2 activities elevated by H₂O₂. CONCLUSION: Food mixtures with synergistic antioxidant activity and protective property against reactive oxygen species‐induced cell death can potentially be incorporated into novel functional foods or beverages with optimum health benefit. The antagonistic effect of food mixtures can be a health concern and thus should be avoided. Copyright © 2012 Society of Chemical Industry     

Oxidative behaviour of Blanquilla pears treated with 1‐methylcyclopropene during cold storage

The increasing use of 1‐methylcyclopropene (1‐MCP) to extend the commercial life of fruit constitutes an attractive way of improving packing house competitiveness. This compound prevents the effects of ethylene in a wide range of fruit and vegetables. However, despite the extensive literature relating to this action on ethylene, little is known about its other physiological effects. In this work, pears (Pyrus malus L cv Blanquilla) were treated with 100 ppb 1‐MCP immediately after harvest and stored in air for 5 months. Differences in oxidative stress and in antioxidant potential between controls and 1‐MCP‐treated fruits were established, determining the changes in the levels of hydrogen peroxide, ascorbate content and ionic leakage during storage. Activities of the H₂O₂‐generating enzyme superoxide dismutase (EC 1.15.11) and the H₂O₂‐scavenging enzymes catalase (EC 1.11.1.6), ascorbate peroxidase (EC 1.11.1.11) and unspecific peroxidase (EC 1.11.1.7) were also determined. 1‐MCP‐treated fruits exhibited lower levels of hydrogen peroxide, ascorbate and lower ionic leakage during storage. In accordance with this result, 1‐MCP‐treated fruits also exhibited higher enzymatic antioxidant potential. These results challenge the hypothesis that the beneficial effects of 1‐MCP on ripening were not exclusively due to its action on ethylene but also to an increase in antioxidant potential in pear. Copyright © 2004 Society of Chemical Industry     

Thermal oxidation studies on reduced folate, L-5-methyltetrahydrofolic acid (L-5-MTHF) and strategies for stabilization using food matrices

The thermal stability of L-5-methyltetrafolic acid (L-5-MTHF) was investigated in model/buffer systems and food systems. L-5-MTHF degradation followed first-order reaction kinetics with relatively greater (P < 0.01) stability at pH 4 compared to pH 6.8 in the buffer systems. This was confirmed using cyclic voltammetry. The stability (for example, k-values) of L-5-MTHF in an oxygen controlled environment improved (P < 0.001) proportionally when in the presence of increasing molar ratios of sodium ascorbate (NaAsc). The addition of NaAsc to L-5-MTHF after heat treatment was also effective at returning thermally oxidized L-5-MTHF back to its original form. A scheme was developed to explain the degradation and regeneration of L-5-MTHF. The importance of antioxidant protection of L-5-MTHF from thermal oxidation was extended using 2 distinct food systems; namely skim milk and soy milk, both with known antioxidant capacities. We conclude that the antioxidant activity of food components can enhance the stability of L-5-MTHF.     

The influence of selenium on the antioxidant activity of green tea

This study was aimed at determining the effects of selenium on the contents of vitamin C, amino acid, total water‐soluble solids and tea polyphenol, and whether the antioxidant activity of selenium‐enriched green tea is enhanced compared with regular green tea by linoleic acid oxidation and the lard oxidation method. The contents of selenium, vitamin C and tea polyphenol in green teas were greatly increased by foliar application of selenium‐enriched fertilizer. No significant differences of the contents of vitamin C, amino acid and tea polyphenol were observed between green tea treated with sodium selenite and that without selenium. The selenium‐enriched green tea exhibited significantly higher antioxidant activity than regular green tea, both in linoleic acid oxidation and in the lard oxidation system. These results suggest that the antioxidant activity of green tea is significantly enhanced by the combination of selenium and green tea constituents compared with that of regular green tea. Copyright © 2003 Society of Chemical Industry     

肉制品加工中使用的辅料——抗氧化剂

氧化是导致食品品质劣变的一个重要因素,也是影响肉及肉制品品质的一个重要因素,防止食品氧化可以通过向食品中添加抗氧化剂实现,食品抗氧化剂是防止或延缓食品氧化,提高食品稳定性和延长食品储藏期的食品添加剂。本文综述食品抗氧化剂的作用机理,抗氧化剂使用的注意事项及食品中常用的抗氧化剂,并简要介绍抗氧化剂活性的测定及对其发展前景进行展望。     

Comparative in vivo antioxidant capacity of DL-2-hydroxy-4-methylthiobutanoic acid (HMTBA) and DL-methionine in male mice fed a high-fat diet

BACKGROUND: In animal diets, methionine (Met) is considered to be the first limiting amino acid, and the activity of synthetic Met is typically added either as DL ‐methionine (DLM) or as DL ‐2‐hydroxy‐4‐methylthiobutanoic acid (HMTBA). It has been demonstrated that HMTBA exhibits a higher antioxidant capability in vitro as compared to DLM. However, the difference in antioxidant capability between DLM and HMTBA in vivo is unknown. METHODS: In the present study, 60 male C57BL/6 mice were randomly divided into six groups and fed either a normal diet (NFD, 5.37% fat) or a high‐fat diet (HFD, 19.7% fat) in conjunction with 0.2% DLM, 0.2% HMTBA or 0.1% DLM and 0.1% HMTBA for 4 weeks. RESULTS: HFD supplemented with 2% DLM and NFD with 2% HMTBA both induced adverse affects in relation to serum lipid parameters and depressed antioxidant defense systems in the digestive system. However, these changes were restored in the 0.2% HMTBA‐treated HFD group. Furthermore, no significant differences were found in the lipid parameters and antioxidant status in the NFD and HFD group supplemented with 0.1% DLM and 0.1% HMTBA. CONCLUSION: HMTBA restored oxidative redox status under OS conditions and its antioxidant properties were positively correlated with the dosage included in diet. Copyright © 2011 Society of Chemical Industry     

Chemical,antioxidant and sensory properties of tomato‐watermelon‐pineapple blends,and changes in their total antioxidant capacity during storage

A conductometric analysis of the effect of condensate of peroxides generated during lipid oxidation in an accelerated stability test was adapted to test the hypothesis that total antioxidant capacity of tomato products would sometimes increase during processing and in storage. Tomato pulp blends made from a mixture of tomato (Lycopersicon esculentum var Roma VF), watermelon (Citrullus vulgaris var Babylack) and pineapple (Ananas comosus var Smooth cayennes) were analysed for basic quality profiles of dry matter, Brix, titratable acidity (TTA) and pH, total reducing sugars, Component antioxidants phytochemicals and total antioxidant capacity. The lowest sensory score (overall impression) of 4.80 ± 2.59 was recorded for tomato juice while, blend TWP 111p had highest score of 6.20 ± 1.99. There was significant difference (P < 0.05) in the basic quality profile of the pulp blends except for TTA values (0.37 ± 0.02 to 0.45 ± 0.05) and 2‐Furfurals (2.47 ± 0.03 to 2.71 ± 0.01). The fresh blend of 50% tomato, 25% watermelon and 25% pineapple had the highest total antioxidant capacity of 3.69 ± 0.52 mg 100 mL^?1 catechin equivalent. The total antioxidant capacity of the stored pulp increased from 2.95 ± 0.13 to 6.22 ± 0.32 mg 100 mL^?1 catechin equivalent in pasteurised TWP 211p blend by 60 days when stored at 40 °C. Total antioxidant status of tomato‐based fruit mix increased during the first 80 days.