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.     

Role of sorbic acid in nonenzymic browning reactions in liquid and solid model food systems

Role of sorbic acid (SA) in browning development in model systems has been studied. In liquid model systems containing water-glycerol-glucose (WGG), water-glycerol-sucrose (WGS), 45% sucrose and 30% sucrose plus 15% glucose, SA degraded when stored at 37°C forming brown pigments. Addition of amino acids (glycine or lysine monohydrochloride) increased the rate of browning development while Cu²⁺ reduced SA degradation and browning development. In the absence of amino acids and SA, WGG and WGS systems did not brown appreciably.
In solid systems with SA adsorbed on microcrystalline cellulose, the maximum rate of browning occurred at 0.73 a_w , but maximum rate of SA loss was at 1.0 a_w . In all systems inclusion of amino acids reduced SA degradation but increased browning development. The rate of SA-induced browning was considerably higher than that caused by sugar-amino acid interactions.     

A factorial approach to identify reactive constituents and their interactions in multicomponent highly acidic model systems simulating lime juice concentrate (32°B)

The non-enzymic browning mechanism in a multicomponent food product such as lime juice concentrate (32°B) was investigated using synthetic model systems. A 2⁵ factorial experiment was designed and the statistically significant main effects and interactions isolated. Four interactions: (1) citric acid + ascorbic acid, (2) citric acid + fructose, (3) fructose + ascorbic acid and (4) citric acid + fructose + ascorbic acid; and three main effects: (1) citric acid, (2) fructose and (3) ascorbic acid, were found to be statistically significant at the 0·05 level. These are interpreted in the light of available literature on non-enzymic browning reactions.     

乳酸菌发酵对梨汁的护色作用

梨汁在加工过程中极易褐变,乳酸菌发酵能有效保护梨汁的色泽。本研究测定梨汁发酵及储藏过程中色泽、多酚氧化酶活性、酚类物质、抗坏血酸含量等指标的变化,并与未发酵梨汁和添加柠檬酸的调酸梨汁对比,探索乳酸菌发酵对果蔬汁的护色机理。30天储藏期内,未发酵梨汁褐变指数从0.073变化至0.310,显著高于发酵梨汁(0.134);乳酸菌发酵作用有效抑制了多酚氧化酶的活性,使得发酵梨汁中的酚类物质的保存率(43%)显著高于未发酵梨汁(16%);发酵梨汁中抗坏血酸稳定性更高,保存率(85%)较未发酵梨汁高(50%),减少了非酶褐变。乳酸菌通过在梨汁中发酵产酸,抑制多酚氧化酶的活性,保存酚类、抗坏血酸等物质,从而保护梨汁色泽。     

响应面优化速冻马铃薯条的护色工艺

马铃薯在加工过程中极易发生褐变,严重影响速冻马铃薯条的产品品质。研究了不同单一护色剂对多酚氧化酶的抑制作用,通过多种护色剂复配对马铃薯进行护色实验。结果表明,抗坏血酸,柠檬酸,氯化钙对PPO酶活性均表现出一定的抑制效果,其最佳质量分数分别为0．20％,0．40％,0．70％;经响应面优化,得出三种护色剂最佳的复配质量分数为抗坏血酸0．30％,柠檬酸0．50％,氯化钙0．76％,此时马铃薯条表面的褐变基本被抑制。     

Role of anthocyanins,polyphenol oxidase and phenols in lychee pericarp browning

Postharvest browning of lychee fruits is investigated in relation to anthocyanins, polyphenol oxidase (PPO) and phenols, using a purified PPO, anthocyanin extract and phenolic extract. Lychee PPO cannot oxidise the degradation of anthocyanins, but the presence of phenolic extract stimulates pigment degradation by PPO, leading to the development of brown pigments. The absorbance at 410 nm of the reaction solution is correlated well with the peel browning index. Pyrogallol, catechol and 4‐methylcatechol are good stimulators, but no action with chlorogenic acid, p‐cresol, resorcinol or tyrosine is observed. A decrease in the ascorbic acid content of lychee pericarp is associated with an increase in the peel browning index, and the addition of ascorbic acid to the reaction mixture exerts a preventive action on the anthocyanin degradation. Data here suggest that anthocyanins, PPO and phenols contribute to lychee pericarp browning involved in anthocyanin–PPO–phenol reactions. © 2000 Society of Chemical Industry     

POLYPHENOLOXIDASE ACTIVITY OF MINIMALLY PROCESSED 'JONAGORED' APPLES (MALUS DOMESTICA)

The influence of three chemical dips using ascorbic acid (AA), citric acid (CA) and calcium chloride (CC) on the polyphenoloxidase (PPO) activity and on the total phenolic content of minimally processed (MP) apple (Malus domestica, cv. Jonagored) during cold storage was evaluated and a potential relationship with enzymatic browning was investigated. An ascorbic acid dip (42.6 mM) of 5 min duration was the most efficient chemical treatment in reducing the PPO activity of apple cubes. A 92% inhibition was achieved after 7 days of storage at 4C. All treatments were advantageous in comparison to the control in reducing color changes. Color changes, determined by absorbance at 420 nm (soluble pigments) and lightness (L) (insoluble pigments) of apple cubes treated with ascorbic acid were correlated with total phenolic content. No correlation was observed between PPO activity and tristimulus color parameters, browning index or total phenolic content of AA‐treated apple cubes.     

The effect of ascorbic acid on oxidative browning of white wines and model wines

The effects of ascorbic acid addition to white wines and model wines were either anti-oxidative or pro-oxidative, and depended, inter alia , on the duration of storage. Soon after its addition, ascorbic acid decreased the redox potential and brown colour of model wines and white wines. However, with time, these effects were reversed, and redox potential, SO₂ consumption and browning were greater in samples with added ascorbic acid. The point at which the net effect of ascorbic acid addition was to increase browning occurred earlier at higher SO₂ levels. Under a variety of accelerated (45®), or prolonged (ranging from three months to five years) storage conditions, the browning of model wines and white wines was invariably enhanced by ascorbic acid addition, and this enhancement took place whether or not SO₂ was present. The addition of SO₂ alone, rather than ascorbic acid alone or SO₂ plus ascorbic acid, appears to be the most effective and least expensive way of protecting white wine from browning during bottle conservation.     

紫薯中多酚氧化酶活性的研究及褐变控制

研究紫薯组织中多酚氧化酶(PPO)的活性,最适pH值、最适温度等特性,并在此基础上,研究加热温度、加热时间、抗坏血酸和柠檬酸添加量对PPO褐变的抑制效果。结果表明：紫薯PPO最适pH值范围为5.5～7.5,最适温度为30℃。在较好的分离淀粉的前提下,最佳抑制褐变条件是：加热温度80℃、加热时间10min、抗坏血酸添加量0.9‰、柠檬酸添加量1.2g/L。     

雪莲果发酵酒的防褐变技术研究

在不影响雪莲果果酒发酵过程和品质的前提下,通过添加抗坏血酸、柠檬酸、蜂蜜、菠萝汁等抗褐变剂来解决雪莲果果酒生产中的褐变问题,得到营养成分损失少、风味佳、色泽鲜亮的雪莲果果酒。结果表明,抑制雪莲果褐变程度的先后顺序为柠檬酸>抗坏血酸>菠萝汁雪莲混合比,蜂蜜在雪莲果酒陈酿期会产生深色物质,不适宜作为雪莲果果酒的抗褐变剂。影响感官的顺序分别为菠萝汁雪莲混合比>抗坏血酸>柠檬酸,最后得出抑制雪莲果酒褐变的最佳组合为抗坏血酸的添加量1.00%,柠檬酸的添加量0.75%,菠萝雪莲混合比为1:4。     

响应曲面法优化花生芽菜护色剂配方

以花生芽菜为原料,选取三种护色剂氯化钠、柠檬酸及抗坏血酸进行护色试验。单因素试验结果表明三种护色剂均对花生芽菜具有良好的护色效果。在单因素试验基础上,采用响应曲面法,以褐变抑制率为评价指标,分析不同护色剂配方对花生芽菜褐变抑制率的影响。结果表明:三种护色剂对花生芽菜褐变抑制率的影响顺序为抗坏血酸>氯化钠>柠檬酸,最佳配方为氯化钠0.31g/100mL、柠檬酸0.93g/100mL、抗坏血酸0.57g/100mL,在此条件下褐变抑制率为73.13%。     

茶多酚在抑制板栗褐变中的应用

本研究比较了茶多酚同抗坏血酸和NaHSO3抑制板栗预煮褐变的效果．结果表明：茶多酚与柠檬酸和EDTA共用时，可以非常有效地抑制板栗预煮褐变，其效果明显优于抗坏血酸或NhHSO3与柠檬酸和EDTA共用的效果，并确定了预煮液的最佳配方为0.01％茶多酚 0.2％柠檬酸 0．2％EDTA．     

Effect of ascorbic acid and citric acid on the quality of salted Chinese cabbage during storage

Changes in color, browning indices, enzyme activity, and physical and chemical quality during the storage period were investigated to assess the effectiveness of storage period extension along with the addition of ascorbic acid (AA) and citric acid (CA) to salted Chinese cabbage. After 16 days of storage, the change in chromaticity value showed treatment with 0.5% CA showed the lowest change in the brown index during the storage period. The control showed the highest residual activity of polyphenol oxidase among control, AA, and CA-treated salted cabbage. AA and CA treatment effectively inhibited the initial populations of microorganisms including total aerobic bacteria, lactic acid bacteria, and yeast and molds in salted Chinese cabbage during storage. Further, the texture, i.e., hardness, chewability, and elasticity, tended to decrease with increasing storage. These results suggest that treatment with AA could help maintain the quality of salted Chinese cabbage during the storage period.     

新型凉果褐变抑制剂的研制

为解决广式凉果中二氧化硫超标的问题,本研究以苹果切片和青梅作为模型,进行单一因素和复配试验,通过测定白度、吸光度并结合感官评价,研发出新型的抑制凉果褐变添加剂.结果表明:鲜切苹果片腌制1d的抑制褐变效果最为理想;1.25 mg/gL-半胱氨酸盐酸盐、2 mg/g异抗坏血酸、5 mg/g柠檬酸和0.625 mg/g亚硫酸氢钠对苹果片(腌制1d)褐变均有较好抑制效果;由感官评价可知,L-半胱氨酸盐酸盐的抑制凉果褐变效果强于亚硫酸氢钠;用异抗坏血酸、柠檬酸、L-半胱氨酸盐酸盐进行复配试验,得出最佳配方:1.25 mg/gL半胱氨酸盐酸盐、5mg/g柠檬酸、1mg/g异抗坏血酸.试验表明:L-半胱氨酸盐酸盐及其复配可用于抑制凉果褐变.     

Prevention of enzymatic browning of apple cylinders using different solutions

Inhibition of enzymatic browning and decay on cut surfaces of Golden Delicious apple using ascorbic acid, cysteine, sodium chloride, calcium chloride, citric acid and sodium ascorbate alone or in combinations was investigated at 4 and 10 °C for a storage period of 0, 7 and 14 days, in an attempt to find the most effective treatment. Apple segments immersed in ascorbic acid and citric acid alone showed visual traces of browning after 7 days storage at 4 °C. After 14 days storage, only ascorbic acid and ascorbic acid plus sodium chloride had moderate browning, while all other treatments were severely affected. However, at 10 °C, only ascorbic acid was effective in reducing the level of browning, although its effect was minimal after 14 days storage. Browning was more severe at 10 °C than 4 °C in all solutions. The browning measurement (a* value) became increasingly positive from 7‐ to 14‐day storage. Microbial decay was absent in all treatments within 7 days at 4 and 10 °C. However, three test solutions showed microbial decay after 14 days storage at 10 °C in addition to the control solution, which showed decay at both 4 and 10 °C storage temperatures.     

Studies on non-enzymic browning in orange juice using a model system based on freshly squeezed orange juice

An orange juice based model system was set up wherein variables such as the addition of glucose, lysine, sorbitol and L -ascorbic acid and changes in pH and storage temperature were introduced to study their effects on L -ascorbic acid degradation and on browning. The addition of glucose, lysine and sorbitol did not have a significant effect on L -ascorbic acid degradation, whereas added L -ascorbic acid acted solely as a reserve material. In terms of browning, a change in pH and storage at elevated temperature produced a synergistic effect in the development of brown colour which was enhanced by the introduction of additives. Based on the results obtained, L -ascorbic acid appears to be the precursor in the non-enzymic browning occurring in this type of sample due to the formation of reactive carbonyl compounds produced upon its degradation which tend to polymerise, or to react with nitrogenous compounds, to give brown pigments.     

复合保鲜剂对鲜切莲藕贮期品质的影响

以二氧化氯预处理后的鲜切莲藕为材料,采用柠檬酸、乙二胺四乙酸二钠、L-半胱氨酸、抗坏血酸对藕片进行复合处理,通过测定藕片褐变度、可溶性固形物、感官品质等指标。结果表明:复合保鲜剂最佳组合为0.8%柠檬酸、0.25%乙二胺四乙酸二钠、0.2%L-半胱氨酸、0.35%抗坏血酸,可有效抑制莲藕褐变,提高贮藏期间产品品质。     

不同添加剂对香蕉褐变的抑制作用研究

选取柠檬酸、抗坏血酸、氯化钠、茶多酚、L-半胱氨酸、草酸作为香蕉褐变的抑制剂,研究其对香蕉经过切片打浆过程中酶促褐变的抑制作用.结合色差测定的定量分析,结果表明L-半胱氨酸是最有效的褐变抑制剂,而且与抗坏血酸具有协同作用.通过正交实验,得出最佳抑制剂复配处理为0.2%L-半胱氨酸和0.3%抗坏血酸复配,处理30min.结合最佳抑制剂处理,在微波功率495W处理30s可得到满意的护色效果.     

褐变抑制剂对干制香蕉片护色效果的影响

为了提高香蕉片干制后的颜色品质,获得最佳护色方法,以褐变度和L*值为考察指标,研究植酸、抗坏血酸、氯化钠、EDTA、柠檬酸5种褐变抑制剂对干制香蕉片颜色品质影响,并优选出提高干制香蕉片颜色品质的护色方法。结果表明:单一护色剂护色效果依次为植酸柠檬酸EDTA氯化钠抗坏血酸,将鲜切香蕉片放入植酸(质量分数为0.9%)和柠檬酸(质量分数为0.3%)组成的复合护色液中浸泡20 min,干制后的香蕉片L*值达65.93,褐变抑制率达84.4%。     

Purification of polyphenol oxidase and the browning control of litchi fruit by glutathione and citric acid

Polyphenol oxidase (PPO, EC 1.10.3.2) was purified to homogeneity from litchi peel yielding a single protein with a molecular weight of about 75.6 kD by Sephadex G‐100 gel filtration, and a 108‐fold purification of PPO achieved. The enzyme was determined to be composed of two similar subunits. Glutathione, L ‐cysteine and citric acid suppressed PPO activity markedly, whereas ascorbic acid and n‐propyl gallate showed a little inhibition. Moreover, the effect was enhanced by the addition of citric acid. On the basis of the inhibition of PPO activity in vitro, the use of 10 mmol l ⁻¹ glutathione and 100 mmol⁻¹ l citric acid was found to give good control of the browning of litchi fruit, and an 80–85% inhibition of PPO activity was observed. It is suggested that application of glutathione in combination with citric acid may slow down the browning of litchi fruit. © 1999 Society of Chemical Industry