抗坏血酸的亚硝酸盐清除能力的研究

文章对抗坏血酸的亚硝酸盐清除能力进行了研究.结果表明,溶液pH、抗坏血酸浓度、丙氨酸和氨基葡萄糖盐酸盐等对抗坏血酸的亚硝酸盐清除能力有显著的影响.在酸性条件下,抗坏血酸表现出较高的亚硝酸盐清除能力.抗坏血酸的浓度愈高,其亚硝酸盐清除能力也愈高.丙氨酸和氨基葡萄糖盐酸盐可明显提高抗坏血酸的亚硝酸盐清除能力.     

催化动力学光度法测定抗坏血酸的研究

在硝酸介质中,利用抗坏血酸对重铬酸钾氧化罗丹明B褪色有强烈的活化作用,建立了催化动力学光度法测定抗坏血酸新方法,方法的线性范围为0.20～4.0μg/ml,方法的检测限为0.050μg/ml,本法用于水果和果汁中抗坏血酸含量的测定,结果满意。     

抗坏血酸对猴头菇β-葡聚糖表观黏度及结构特征的影响

采用碱提醇沉法制备猴头菇β-葡聚糖(Hericium erinaceus alkali-extracted polysaccharide,HEAEP),系统研究了不同条件(抗坏血酸浓度、金属离子、温度、pH值等)下抗坏血酸对HEAEP表观黏度的影响,并深入分析了抗坏血酸对HEAEP结构特征的影响。研究结果表明:猴头菇β-葡聚糖表观黏度与抗坏血酸浓度存在依赖性,当抗坏血酸质量分数超过0.10000%时,抗坏血酸浓度越高,降解效果越差;金属离子(Cu²⁺、Fe²⁺)的加入会进一步促进抗坏血酸对HEAEP表观黏度的降解作用;而温度的影响相对较小;pH值和作用时间也有一定影响,当pH值为4,作用时间为12 h时,抗坏血酸对HEAEP降解效果最好。此外,抗坏血酸能降低HEAEP分子质量,但对HEAEP糖苷键类型及比例、单糖组成和特征官能团等结构特征影响较小。抗坏血酸降低猴头菇β-葡聚糖表观黏度的效果受到多重因素的影响,其中抗坏血酸浓度、Cu²⁺、Fe²⁺等影响较大,但作用前后的多糖主要结构特征变化相对较小。研究结果旨在为抗坏血酸与β-葡聚糖共存食品的生产提供理论参考。     

油脂包埋L-抗坏血酸对面包品质改良的研究

研究了四种不同熔点油脂所包埋的L-抗坏血酸对面团的氧化特性,以及对面包品质改良的影响,通过正交试验研究了包埋L-抗坏血酸的最佳配比。结果显示,包埋用的油脂熔点以及面团醒发温度对面团的延伸率以及拉伸特性有影响,即用油脂包埋的L-抗坏血酸可以在相对应的面团温度下释放出来,因此可利用不同熔点的油脂包埋L-抗坏血酸,使其在醒发后期和烘烤前期释放出来再起作用,延长L-抗坏血酸的氧化作用时间。正交实验得到四种样品最佳配比为:牛油包埋的L-抗坏血酸0.025g/kg面粉,棕榈油包埋的L-抗坏血酸0.025g/kg面粉,氢化棕榈油包埋的L-抗坏血酸0.05g/kg面粉,棕榈油硬脂包埋的L-抗坏血酸0.075g/kg面粉。     

Ascorbic acid and white wine production: a review of beneficial versus detrimental impacts

We review the use of ascorbic acid in winemaking and the benefits as well as the detrimental outcomes associated with its use. Initial discussion focuses on the antioxidant activity of ascorbic acid. The impact of the wine matrix and wine production practices, especially storage in bottle and oxygen ingress, on its antioxidant efficiency is discussed. The complementary roles of the antioxidant pair, ascorbic acid and sulfur dioxide, are presented. Thereafter, the ability of ascorbic acid to contribute to spoilage processes is covered. This includes both pro‐oxidant and non‐oxidative mechanisms induced by ascorbic acid that may lead to a reduced shelf life of white wine. Based on this review of scientific literature, the conditions most conducive to the beneficial impacts of ascorbic acid in wine are highlighted. Areas where lack of chemical knowledge still exists are identified for future research.     

抗坏血酸改性大豆7S球蛋白物化特性研究

研究了抗坏血酸改性大豆7S球蛋白对体系粘度、发泡性、发泡稳定性、乳化性、乳化稳定性的影响。结果表明：7S球蛋白的感官质量优于大豆分离蛋白；0．8％的抗坏血酸改性7％的7S球蛋白，其粘度最大，达到39．5MPa．s；7S球蛋白溶液浓度为5％、加入0．4％的抗坏血酸改性，其体系的发泡性能最佳，泡沫体积达到515mL；7S球蛋白溶液浓度为7％、加入0．4％的抗坏血酸改性，其体系的发泡稳定性最佳，达到68．9％；7％的7S球蛋白溶液采用0．8％的抗坏血酸改性，体系的乳化性能和乳化稳定性均最强。     

Ascorbate Oxidase in Mature Orange Peel

Evidence of the occurrence of ascorbic acid oxidase in the peel of mature orange is presented. The enzyme was found to be insoluble and located in albedo only. It is specific for ascorbic acid but not for catechol and is oxygen-dependent, with pH optimal activity of 6.5. The ascorbic acid oxidase acitivity was inhibited by high temperature, a pH below 3.5, and copper-chelates such as sodium azide and sodium dithiocarbamate. Blanching and decreasing the pH of the peel to 3.5 are recommended to achieve maximum stability of ascorbic acid in orange peel.     

Assay of ascorbic phosphates and in-vitro availability assay of ascorbic mono-and polyphosphates

A method was devised to assay ascorbic phosphate esters in biological materials by potassium bromoxide hydrolysis followed by determination of the liberated ascorbic acid. For the differential measurement of ascorbic acid and ascorbic phosphate, a spectrophotometric method was employed to screen out the interfering substances based on studies of absorbance curves of 2,4-dinitrophenyl hydrazine derivatives. A variety of vertebrate tissues were examined for phosphatase activity on ascorbic phosphate esters. The results suggest that pigeon kidney, rat liver and several tissues of fishes readily hydrolyse ascorbic monophosphate but not ascorbic polyphosphate. Hydrolysis of ascorbic monophosphate is completed by both phosphatases of intestine, kidney and liver acting at neutral pH and phosphatase of stomach acting at acid pH. Thus, ascorbic monophosphate has the potential to be a source of available vitamin C in vivo, and this explains its antiscorbutic activity in scurvy-prone animals.     

Stability of patulin in a juice-like aqueous model system in the presence of ascorbic acid

In the present study, the stability of patulin in an aqueous juice-like model system was investigated. At acidic pH, the presence of ascorbic acid reduced the stability of patulin. After 34 days, patulin was reduced to 30% of its initial concentration in the presence of ascorbic acid compared to 68–71% in samples without ascorbic acid. Conditions during storage (presence of light, oxygen and/or metal ions) influenced the stability of patulin. Furthermore, it was possible to induce degradation of patulin by either generating hydroxyl radicals or by adding the rather stable radical diphenyl-1-picrylhydrazyl (DPPH). Data from the present study indicate that patulin is decomposed by free radicals generated by oxidation of ascorbic acid to dehydroascorbic acid. Rapid oxidation of ascorbic acid in the presence of oxygen, catalysed by free metal ions, resulted in a decrease of patulin. After complete oxidation of ascorbic acid, no further patulin degradation was observed. In contrast, slow oxidation of ascorbic acid in the presence of metal-chelators induced a continuous, slow oxidation of patulin. Due to low oxygen content in the headspace of a food package, addition of ascorbic acid to products such as apple juice, prior to filling, cannot be considered as an effective decontamination strategy.     

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.     

Oxidation of methionine: Effect of ascorbic acid autoxidation

Free methionine is oxidised in solutions containing ascorbic acid. For this oxidation to take place, molecular oxygen is required and trace amounts of metal ions catalyse the reaction. Our results indicate that ascorbic acid must autoxidise before reacting with methionine. Catalase, histidine and scavengers of hydroxyl radical (benzoic acid and ethanol) inhibit the reaction. The superoxide anion is not involved in the reaction as superoxide dismutase did not affect the oxidation rate. Dehydroascorbic acid also oxidises methionine, but at a much slower rate than ascorbic acid. In the presence of ascorbic acid, the main product in the reaction is methionine sulphoxide, but other products are also formed. Peptide-bound methionine is oxidised to a much lesser extent than free methionine.     

APPLICATION AND ADVANTAGES OF THE ENZYMATIC METHOD FOR THE ASSAY OF ASCORBIC AND DEHYDROASCORBIC ACIDS AND REDUCTONES Determination in Fresh and Canned Spinach

A new enzymatic method based on the reaction ascorbic acid +½O₂→ dehydroascorbic acid + H₂O permits assaying for ascorbic and dehydroascorbic acids in vegetable extracts. The method is carried out using a Clark's electrode which determines the oxygen uptake during the above reaction. The method applied to both fresh and canned spinach is specific and reproducible. Some interfering substances may reduce the specificity and precision of the method, but the addition of chelating agents or acetaldehyde eliminates these interferences. On adding boric acid, only the interfering reductic acid is assayed. The ascorbic and dehydroascorbic acid values for fresh spinach range between 528–919 mg/100g for ascorbic acid and from 21–81 mg/100g for dehydroascorbic acid. For canned spinach the ascorbic acid values ranged from 119–202 mg/100g and the dehydroascorbic acid values from 25–110 mg/100g. The method is easy and rapid and can be utilized advantageously for routine analyses.     

Impact of ascorbic acid on the oxidative colouration and associated reactions of a model wine solution containing (+)−catechin,caffeic acid and iron

Background and Aims: The aim of this study was to examine the oxidative reactions and associated colouration changes relevant to white wine in a synthetic wine system consisting of different combinations of 200 mg/L caffeic acid, 150 mg/L (+)?catechin and 1000 mg/L ascorbic acid, in the presence of 1.5 mg/L iron(II). Method and Results: Reactions were monitored by UV/VIS, CIELab, LC‐DAD and LC‐MS techniques. When ascorbic acid was less than 90% depleted in samples, it induced yellow/green colouration but prevented brown colouration that would otherwise result from catechin‐ and caffeic acid‐derived yellow and red pigments. However, during the loss of ascorbic acid, in the presence of either catechin and/or caffeic acid, reactions were still occurring to ‘prime’ the system for rapid colour formation. When the ascorbic acid was more than 90% depleted, the samples with catechin and/or caffeic acid had an increased rate of brown colouration compared with those to which ascorbic acid was not added. Conclusions: This study demonstrates that ascorbic acid is an effective anti‐browning agent provided it persists in the wine after bottling, but if depleted, serious brown colouration ensues. Significance of the Study: Findings detailed in this report will provide useful guidelines for the more effective use of ascorbic acid as an anti‐browning agent in bottled wine.     

Effect of ascorbic acid on the odours of cloudy apple juice

Ascorbic acid is used in apple juice as an antibrowning agent. This study investigated the effect of ascorbic acid (0.0–0.2% w/v) on the odours of cloudy apple juice using sensory evaluation and gas chromatography (GC). The increase in ascorbic acid concentration in the apple juice resulted in increases in green and unnatural odours and decreases in fresh, fruity and apple-like odours. In the GC determination, 23 volatile compounds were detected in apple juice. Aroma value, which showed the relative importance of volatile compounds, was used to elucidate the changes in odours of apple juice due to the addition of ascorbic acid. The aroma values of hexanal and trans-2-hexenal in the apple juice with 0.2% w/v ascorbic acid increased about 4 and 5-fold from those in the ascorbic acid-free apple juice, respectively. On the other hand, the aroma values of esters insignificantly changed in the apple juice with ascorbic acid. The increases in aroma values of aldehydes corresponded well with the increase in green odour in the apple juice with ascorbic acid.     

不同品种大豆发芽过程中抗坏血酸合成积累的比较研究

测定了鲁豆2号、淮豆l号、吉林3号和楚秀等4种不同品种大豆发芽过程中抗坏血酸含量的变化情况，结果表明供试大豆在发芽过程中抗坏血酸含量均显著增加，说明大豆发芽过程中开始了抗坏血酸的合成代谢。发芽4天后的鲁豆2号和淮豆l号的抗坏血酸含量高于相同发芽条件下的吉林3号和楚秀，表明不同品种发芽大豆中抗坏血酸的合成能力不同。在4种发芽大豆中均检出半乳糖酸内酯脱氢酶(GLDH)，其活性受光照条件的影响，蓝光、白光、紫外光对GLDH活性具有促进作用，紫外光的促进作用最显著。在相同光强和相同时间的紫外光照射下，楚秀和吉林3号的抗坏血酸增加量高于鲁豆2号和淮豆1号，表明不同大豆品种对紫外光的敏感性不同。     

Ascorbic Acid: Microencapsulation Techniques and Trends—A Review

Developments in nutritional sciences have increased the functional significance of ascorbic acid (vitamin C) as a food component in the human diet for health promotion and disease prevention. This has motivated food researchers to develop ascorbic acid–fortified food products to deliver appropriate levels of this vital food ingredient. Unfortunately, the highly unstable nature of ascorbic acid has posed technological challenges for its incorporation into different food systems. Microencapsulation is a promising approach to ensure the stability of ascorbic acid and to improve consumer acceptability towards the carrier food. The most commonly used techniques for ascorbic acid (water soluble) encapsulation, including spray drying, spray cooling, spray chilling, fluidized bed coating, liposomes, and extrusion, are reviewed and discussed with respect to technical hurdles and potential benefits.     

Role of ascorbic acid in promoting follicle integrity and survival in intact mouse ovarian follicles in vitro

Ascorbic acid has three known functions: it is necessary for collagen synthesis, promotes steroidogenesis and acts as an antioxidant. Within the ovary, most studies have concentrated on the role of ascorbic acid in luteal formation and regression and little is known about the function of this vitamin in follicular growth and development. Follicular growth and development were investigated in this study using an individual follicle culture system that allows the growth of follicles from the late preantral stage to Graafian morphology. Follicles were isolated from prepubertal mice and cultured for 6 days. Control media contained serum and human recombinant FSH. Further groups of follicles were cultured in the same media but with the addition of ascorbic acid at concentrations of either 28 or 280 micromol l(-1). Addition of ascorbic acid at the higher concentration significantly increased the percentage of follicles that maintained basement membrane integrity throughout culture (P < 0.001). Ascorbic acid had no effect on the growth of the follicles or on oestradiol production. Metalloproteinase 2 activity tended to increase at the higher concentration of ascorbic acid and there was a significant concomitant increase in the activity of tissue inhibitor of metalloproteinase 1 (P < 0.01). Follicles cultured without the addition of serum but with FSH and selenium in the culture media underwent apoptosis. Addition of ascorbic acid to follicles cultured under serum-free conditions significantly reduced apoptosis (P < 0.05). From these data it is concluded that ascorbic acid is necessary for remodelling the basement membrane during follicular growth and that the ability of follicles to uptake ascorbic acid confers an advantage in terms of granulosa cell survival.     

Effect of ascorbic acid on the stability of beta-carotene and capsanthin in paprika (Capsicum annuum) powder

The effect of ascorbic acid, light, and storage on the stability of the pigments beta-carotene and capsanthin in red pepper (Capsicum annuum) powder has been elucidated by determining the amount of pigment in samples treated by various concentrations of ascorbic acid. Determination of pigment concentration has been performed after different storage times using high-performance liquid chromatography. The dependence of the concentration of pigments on the concentration of ascorbic acid, presence of light and the storage time has been assessed by stepwise regression analysis. The concentration of pigments decreased at longer storage time and increased at higher concentration of ascorbic acid, beta-carotene being more sensitive towards storage time and concentration of ascorbic acid than capsanthin. Interaction between the effects of light and storage time, and light and concentration of ascorbic acid has been established.     

Partial replacement of NaCl by KCl in salted mackerel (Scomber japonicus) fillet products: effect on sensory acceptance and lipid oxidation

Mackerel fillets were salted with NaCl and/or KCl to determine the most acceptable level by sensory evaluation. Additionally, the effects of ascorbic acid, vacuum packaging, and cold storages on lipid oxidation were determined for the salted mackerel fillets. Appropriate level of NaCl was ≤2%. Fifty percent replacement of NaCl by KCl reduced NaCl level with minimal impact on sensory quality. The higher the level of ascorbic acid (0–0.5%, weight basis), the higher the antioxidant effect observed with thiobarbituric acid value and peroxide value. There was no significant difference in sourness (α = 0.05) between the salted mackerel samples treated with and without ascorbic acid (0.25%). Vacuum packaging and storage at ?18 °C along with ascorbic acid was most effective in retarding lipid oxidation in the salted mackerel. Vacuum‐packaged sample with ascorbic acid stored at 2 °C was least oxidised, followed by vacuum packaging without ascorbic acid and then ascorbic acid without vacuum.     

Ascorbic acid contribution to ORAC values in berry extracts: An evaluation by the ORAC-pyrogallol red methodology

An oxygen radical absorbance capacity (ORAC) method based on pyrogallol red bleaching (ORAC-PGR) was used to evaluate the scavenging activity of berry extracts (blackberry, blueberry, and raspberry). Among berry extracts, only raspberry protected pyrogallol red through a clear induction time, related exclusively to ascorbic acid. The lag time allowed an estimation of the ascorbic acid concentration and its contribution to the total ORAC value, estimating that 66% of the ORAC-PGR value of raspberry is related to ascorbic acid. Also, from the induction time, an ascorbic acid concentration of 36 mg per 100 g of fresh weight was estimated for raspberry samples. The ORAC-PGR procedure could be considered as a fast and specific methodology for an estimation of ascorbic acid concentrations in complex samples.