Activated oxygen species and oxidation of food constituents.

Activated oxygen species which may be important in initiating oxidative changes in foods include singlet oxygen, hydroxyl radical, ozone, superoxide anion (perhydroxyl radical at low pH), and hydrogen peroxide. Chemical and enzymic reactions known to occur in biological materials can generate singlet oxygen, hydroxyl radical, superoxide anion, and hydrogen peroxide. Ozone is primarily a product of photoreactions in polluted air. Reactions involving singlet oxygen, hydroxyl radical, and ozone with food constituents can ultimately yield peroxides which decompose to initiate oxidative chain reactions. Superoxide anion and hydrogen peroxide are relatively inert toward organic molecules but can decompose to produce the more reactive singlet oxygen and hydroxyl radical. Inhibition of reactions initiated by reactive oxygen species in foods should be very important in preserving the oxidative stability of foods. The generation, detection, measurement, reaction, and inhibition of reactions of active oxygen species are surveyed in this review.     

Oxygen involvement in betanine degradation—Measurement of active oxygen species and oxidation reduction potentials

The possible involvement of active oxygen species in the degradation of betanine was investigated using a variety of chemical and enzymatic tests. Neither singlet oxygen nor superoxide anion were implicated in the oxidative degradation of betanine. Betanine was destroyed in solutions containing photosensitized riboflavin. Oxidation—reduction (redox) potentials were measured in solutions containing betanine or its aglycone, betanidin. The lower potential of betanidin, relative to betanine, coincided with a greater susceptibility of the aglycone to destruction by molecular oxygen.     

Predicting the impact of food processing on food constituents

With the advent of improved analytical techniques, statistical experiment design, computers and knowledge of food constituents, there have been significant advances in our knowledge of the impact of processing on food constituents. Unfortunately some of this information has not contributed significantly to our ability to predict the influence of processing or resulted in refined predictive equations. This paper reviews our current ability to predict the influence of processing on food constituents. Traditional and potential processes are examined and research needs are identified so that food quality quantification and prediction advances.     

Mechanistic model to couple oxygen transfer with ascorbic acid oxidation kinetics in model solid food

A mechanistic model was developed taking into account both oxygen and ascorbic acid transfer phenomena and oxidation reaction of ascorbic acid. Studied system was cylindrical agar gel initially spiked with ascorbic acid and exposed to air on one face. This model describes oxygen and ascorbic acid diffusion (using Fick’s law) and ascorbic acid oxidation rate. A sensitivity study showed that partial order of reaction with respect to oxygen was the critical factor in this model coupling transfer and reaction phenomena. This model has been validated at 20 °C using local measurements of ascorbic acid and oxygen contents in agar gels, and also using average ascorbic acid content, both type of data having been measured at different sampling times. It was shown that the reaction occurred at a significant extent only near from the interface air/gel, i.e. the part of the gel near from the interface air/gel contained high level of oxygen and low level of ascorbic acid, whilst the part near the other extremity of the gel contained high level of ascorbic acid and low level of oxygen. This model could be a useful tool to precisely locate the zone in a solid food submitted to oxidation, to determine which reactant and which phenomenon (diffusion and/or reaction) is rate limiting and consequently to assess better designs for strategies of protection against oxidation.     

Cell-wall constituents of some grass species and varieties

Structural carbohydrates and lignin were determined in two varieties each of perennial ryegrass, cocksfoot and timothy during first growth. Structural carbohydrates were extracted with N-sulphuric acid and with 72% sulphuric acid and partitioned by paper chromatography. The content of structural constituents increased and in vitro digestibility decreased as the grasses matured. When compared at the same growth stage, perennial ryegrass varieties were higher in digestibility and lower in lignin than the other grasses. When compared at the same level of dry matter digestibility cocksfoot varieties were lower in structural carbohydrates but higher in lignin than other grasses. Correlations between digestibility and the content of structural constituents including fibre were highly significant. The results are discussed with reference to the effect of varietal variation in structural constituents on digestibility and voluntary intake.     

小麦麸皮的功能组分及其在食品中的开发应用

本文介绍了小麦麸皮的营养成分、功能成分及近年来以小麦麸皮为原料的研究、开发中较为实用的生产工艺。通过对小麦麸皮食品的探讨,旨在引起消费者和食品厂商的关注,发展国内麦麸类食品。     

Sweet and bitter constituents of Wilbrandia species

Two novel cucurbitane glycosides, wilbrandisides A and B were isolated as sweet-taste substances from the root of Wilbrandia species (Cucurbitaceae) along with seven known cucurbitane glycosides. Their structures were determined by spectroscopic means, including two-dimensional NMR experiments. Their sweet-taste properties were evaluated by a human sensory panel test. Consequently, wilbrandiside A was shown to be 28 times sweeter than sucrose and was the compound having the most potent sweet taste of all the cucurbitane glycosides isolated from this plant.     

Relationship between oxygen sensitivity and oxygen metabolism of Bifidobacterium species.

Bifidobacteria, which are obligate anaerobes, were studied to determine the relationship between their sensitivity to oxygen and oxygen metabolism. Among the four species tested, Bifidobacterium infantis, Bifidobacterium breve, and Bifidobacterium longum differed from Bifidobacterium adolescentis in sensitivity to oxygen. The former three species showed marked growth under conditions of partial aeration, whereas the growth of B. adolescentis was suppressed by low concentrations of oxygen. Bifidobacteria express reduced NAD-oxidase and -peroxidase activities, which function in a pathway for two-electron reduction of molecular oxygen, producing hydrogen peroxide and, subsequently, water. Activities of reduced NAD-oxidase and -peroxidase were inversely correlated with their sensitivities to oxygen. Bifidobacterium adolescentis exhibited lowered activities of these two enzymes; the activities were 10 to 20% of those observed with B. infantis, B. breve, and B. longum. These observations are compatible with the hypothesis that reduced NAD-oxidase and reduced NAD-peroxidase in Bifidobacterium species play a role in prevention of oxygen toxicity. Superoxide dismutase activity was also detected in Bifidobacterium species. Superoxide dismutase is probably not involved in detoxification of oxygen, because the activity of this enzyme was extremely low, and the sensitivity to oxygen varied independently of superoxide dismutase activity.     

Fenton-mediated oxidation in the presence and absence of oxygen

The increased use of Fenton systems for the treatment of contaminated waters and wastewaters necessitates the development of kinetic models capable of accurately simulating key species concentrations in order to optimize system performance and efficiency. In this work a reaction mechanism in which the hydroxyl radical is nominated to be the active oxidant in Fenton systems is used to describe the oxidation of formic acid (HCOOH) under a variety of experimental conditions. A kinetic model based on this reaction mechanism is shown to adequately describe results of experiments in which starting concentrations of H202 and HCOOH varied over 1 and 4 orders of magnitude, respectively, under both air-saturated and deaerated conditions. The intermediate generated during HCOOH oxidation was observed to increase oxidation efficiency, especially at high initial organic concentrations [relative to Fe(II)], by assisting in the redox cycling of iron. In the presence of oxygen, however, such improvement was attenuated through competition for the organic intermediates. While mechanistic analysis and associated kinetic modeling is invaluable in optimization of Fenton systems, a clear understanding of reaction byproducts and their reactivity toward other species in the system is critical for accurate simulations.     

Rice bran and its constituents: Introduction and potential food uses

Rice bran (RB) is one of the by-products during the milling of rice. RB is underutilised due to its ease of susceptibility towards enzymatic activity. RB contains various bioactive compounds such as γ-oryzanol, phytosterols, tocols and squalene. High nutritional properties make RB, and its constituents play their different roles in the food industry, such as gluten flour substitutes, alternate shortening, organogelators, stabilisers and other types of additives. This review will briefly introduce the RB and its constituents and discuss their potential applications in the food industry.     

Lipid oxidation and antioxidant delivery systems in muscle food

Lipid oxidation accelerates quality deterioration in muscle-based foods (fish, red meat, and poultry), resulting in off-odors/flavors, color problems, texture defects, and safety concerns. Adding antioxidants is one approach to control lipid oxidation, and several delivery strategies have been applied, such as supplementing antioxidants to the feed, direct mixing into minces, or, for whole muscle pieces; spraying, glazing, and injection. However, some issues linked to these technologies hinder their wide utilization, such as low effectiveness, noncompatibility with clean label, and off-flavor. These shortcomings have promoted the development of new antioxidant delivery technologies. In this review, the main focus is on the principles, characteristics, and implementation of five novel antioxidant delivery methods in different types of muscle food products. Their advantages and drawbacks are also summarized, plus comments about future trends in this area. Among novel routes to deliver antioxidants to muscle foods are, for whole tissues, recyclable dipping solutions; for minces, encapsulation; and, for both minces and whole tissues, cross-processing with nonmuscle antioxidant-containing raw materials as well as applications of edible films/coatings and active packaging. Advantages of these technologies comprise, for example, low price, the possibility to control the antioxidant release rate, overcoming strong aromas from natural antioxidants, and allowing antioxidant-containing raw materials from the food industry to be valorized, providing an opportunity for more circular food production.     

Free radical oxidation and food antioxidants in allergic diseases

The article reviews experimental and clinical data that supports free radicals participation in allergic reactions development. Free radical reactions were shown to take place in activation of first and second order target cells, in cellular interactions participating in allergic inflammation; besides these free radicals initiate lipid peroxidation in target cells and produce shift in eicosanoid metabolism. The review discusses participation of free radicals in allergy pathogenesis and proposes the expedience of food antioxidants utilization in complex treatment and prophylactic of allergic diseases.     

海洋磷脂氧化及其对食品风味的影响

海洋磷脂因其独特的结构和生物活性引起人们的关注。海洋磷脂广泛存在于水产品中,由于多不饱和脂肪酸含量高,在加工和储运过程中易发生脂质氧化反应、非酶促褐变反应等,这一系列反应生成的产物一方面引起水产品的酸败,降低食品的品质;另一方面适当的磷脂氧化,提供了脂质来源的风味前体物质,是水产品特征香气物质产生的关键。在水产品的挥发性风味物质中已鉴定出醇、醛、2-戊基呋喃、苯甲醛等特征香气成分,此类风味物质的形成来源于脂质氧化以及非酶褐变等反应,受这些反应共同作用的影响,形成了食品独特诱人的品质和风味。该文综述了海洋磷脂氧化及其在食品风味中的作用,为深入理解食品特征风味物质形成提供参考。     

Effect of solvent and certain food constituents on different antioxidant capacity assays

The effect of the sample solvent in the antioxidant capacity of foods measured by the four most widely used procedures (ABTS, FRAP, DPPH and ORAC) has not been systematically studied. This was the aim of this work. The antioxidant capacity of catechin:gallic acid solutions in different solvents (water, methanol/water, methanol, acetone/water) were determined. Significant differences were found between the values obtained by the same method in different solvents, as well as between the ones obtained by the different method in the same solvent (ranging from 10,000 to 30,000 μmol Trolox/g dw). In addition, certain non-antioxidant food constituents, such as amino acids and uronic acids, also showed an interfering effect on these assays. ORAC was the assay in which all these factors had a greatest interfering effect. Antioxidant capacity values should only be compared when the measurements have been made by the same method in the same solvent.     

自由基、活性氧与疾病

该文主要介绍自由基、活性氧与疾病关系,并简要提出抑制自由基方法。     

Differential scanning calorimetric study of meals and constituents of some food grain Legumes

Two thermal transitions were observed in soya bean meal by differential scanning calorimetry (DSC) and on the basis of previous data were ascribed to the denaturation of the 11S globulin, glycinin, and the 7S globulin, β-conglycinin. Three DSC transitions were apparent in Vicia faba meal; one was associated with starch gelatinisation, and was absent from thermograms of soya bean because the latter stores oil rather than starch. The remaining two transitions were identified with the 11S globulin, legumin, and a 7S globulin, vicilin. The denaturation parameters of legumin and glycinin were very similar, in contrast to those of vicilin and β-conglycinin. From this it was concluded that legumin and glycinin probably represent homologous proteins, whereas the two 7S proteins possess intrinsically different structures to one another. Cowpeas (Vigna unguiculata) and dry beans (Phaseolus vulgaris) afforded two major transitions which were assigned to 7S globulins and starch. From its DSC profile, the 7S globulins of cowpea appeared heterogeneous, but nevertheless possessed denaturation characteristics similar to those of vicilin of V. faba. In contrast, the thermal behaviour of the 7S globulin of dry beans (glyco-protein II) was distinct from that of any of the other 7S globulins investigated. Three protein transitions were observed in the three lupin species examined. As in the case of soya bean, no starch transition was present. On the basis of the correspondence in transition temperature, one of the protein transitions was assigned to the 11S globulin component. Overall, this study indicates the potential of DSC as a means for obtaining data on seed protein homology from whole meals rather than the extracted proteins.