浓缩苹果汁的褐变与控制措施

褐变是影响我国浓缩苹果汁出口的主要问题之一，通过分析浓缩苹果汁产生酶促褐变与非酶褐变的原因，阐述了目前防止苹果汁褐变的主要措施。基本上消除了浓缩苹果汁的褐变。     

浓缩苹果汁生产中褐变因素及其控制措施的探讨

通过分析浓缩苹果汁的生产工艺,阐明了目前苹果汁生产中防止褐变的基本措施以及引起果汁后期贮藏发生褐变的原因。浓缩苹果汁的生产工艺基本消除了果汁贮藏期的酶促褐变,在贮藏期的褐变限于非酶促褐变,主要是Maillard反应和焦糖化反应。     

混浊苹果汁加工过程中的酶促褐变及其防止的研究

将几种可用于食品的防褐变剂在苹果破碎时加入,考察了它们对苹果浆和苹果鲜榨汁的防褐变效果及它们之间的协同作用。半胱氨酸、抗坏血酸、曲酸、氯化钠和氯化钙都是较好的防褐变剂。在所测试条件下,抗褐变的能力（褐变抑制率）为:0.1％的抗坏血酸>0.1％的偏重亚硫酸钠>0.1％的曲酸>0.1％的氯化钙>0.005％半胱氨酸>0.1％氯化钠。它们抗褐变能力都表现为浓度依赖型,特别是抗坏血酸。柠檬酸在所测试条件下没有抗褐变效果。0.044％NaCl+0.0125％Vc的组合较经济且可使果汁40min不变色。果浆脱气可减缓其褐变;减小果汁及果浆与空气的接触面也可防止褐变。      

混浊苹果汁加工过程中的的酶促褐变及其防止的研究

将几种可用于食品的防褐变剂在苹果破碎时加入,考察了它们对苹果浆和苹果鲜榨汁的防褐变效果及它们之间的协同作用.半胱氨酸、抗坏血酸、曲酸、氯化钠和氯化钙都是较好的防褐变剂.在所测试条件下,抗褐变的能力(褐变抑制率)为0.1%的抗坏血酸＞0.1%的偏重亚硫酸钠＞0.1%的曲酸＞0.1%的氯化钙＞0.005%半胱氨酸＞0.1%氯化钠.它们抗褐变能力都表现为浓度依赖型,特别是抗坏血酸.柠檬酸在所测试条件下没有抗褐变效果.0.044%NaCl+0.0125%Vc的组合较经济且可使果汁40min不变色.果浆脱气可减缓其褐变;减小果汁及果浆与空气的接触面也可防止褐变.     

Kinetic modelling of non-enzymatic browning of apple juice concentrates differing in water activity under isothermal and dynamic heating conditions

The kinetics of non-enzymatic browning in apple juice concentrates were investigated. The effect of a_w (in the range of 0.74–0.99) and/or reactant concentration on brown pigment formation was monitored under isothermal heat treatment at four temperatures (60, 70, 80 and 90 °C) in apple juice solutions having either the same or different concentrations of reactant solutes. The extent of the Maillard reaction was evaluated by spectrophotometric measurements at 420 nm (A₄₂₀). The absorbance–time curves were fitted to five different kinetic models (zero and first order, weibull, logistic and the parabolic model) and estimates of browning rate constants and other model parameters were obtained. Regression analysis revealed that the logistic model was the most appropriate for describing browning in apple juice. The initial reactant concentration, but not water activity, had a significant effect on the colour change of apple juice. The processing temperature also had a strong impact on browning kinetics. Secondary models, expressing the dependence of the best fitted primary model parameters on temperature and a_w, were further developed and validated by comparing the predicted model parameters with the values observed in independent isothermal experiments. Finally, the derived model was further evaluated against the observed browning responses of apple juice under dynamic heating conditions, underlining the applicability of the developed model as a practical prediction tool for the study of non-enzymatic browning.     

Factors influencing the clarification of apple juice with honey

Six apple cultivars were studied to determine the effect of pH, degree of browning and polyphenol composition on clarification of apple juice by addition of honey. The optimum pH for all apple cultivars was about 3·5. Only browned apple juices, those prepared with no ascorbic acid, flocculated with the honey and consequently clarified. The flocculation time was inversely related to the degree of browning of all apple cultivars except Golden Delicious. The clarification rate did not correlate well with the different phenolic groups present in the juices.     

Polyphenoloxidase activity and total phenolic content as related to browning of minimally processed ‘Jonagored’ apple

Phenolic content, polyphenoloxidase (PPO) activity and browning have been reported by different authors to vary in different ways, depending on cultivar, picking maturity, storage conditions, etc. Numerous authors have attempted to correlate browning results with the phenolic content and/or enzymatic activity of apples, but data published in the literature are divergent as to which of the two factors, ie the enzyme or the substrate, plays the decisive role in the overall phenomenon of enzymatic browning. The aim of this work was to follow the PPO activity and phenolic content of minimally processed apple (cv ‘Jonagored’) during cold storage and to establish a potential relationship with enzymatic browning. Increasing storage time of minimally processed apple seemed to result in an increase in PPO activity. No changes (P > 0.05) in total phenolic content were observed during storage. Colour degradation of apple cubes, as indicated by changes in colour parameters, was found to be highly correlated with PPO activity. Browning of ‘Jonagored’ apple cubes during storage was found to be moderately correlated with PPO activity. No correlation was found between the browning index and the total phenolic content. © 2001 Society of Chemical Industry     

苹果酱加工中褐变利用研究与探讨

根据苹果果肉在加工中褐变程度不同,其色泽不同的现象,研究了利用褐变对苹果酱加工色泽控制的新方法,探讨了利用酶褐变与色泽变化规律进行水果蔬菜加工色泽控制的途径,为果蔬加工品的色泽控制提供了全新的思路与可行的研究方法。     

间歇式中小型苹果真空打浆机设计

针对中小型苹果打浆机工作过程中存在的苹果氧化褐变而影响果浆的外观和口感问题,设计了一种间歇式中小型苹果真空打浆机装置。根据苹果打浆工艺特点,研究了真空打浆机的工作原理与基本结构;阐述了苹果真空打浆机工作运行过程及真空脱气保障。验证实验表明:试验设计的间歇式中小型苹果真空打浆机可有效遏制苹果褐变,提高果浆质量。     

Efficacy of phytic acid as an inhibitor of enzymatic and non-enzymatic browning in apple juice

Browning decreases the commercial value of apple juice, and therefore colour preservation during processing and storage is the main objective of manufacturers. In this study, the efficacy of phytic acid as a browning inhibitor for use on apple juice was investigated. Browning of apple juice treated with phytic acid was monitored during processing and storage. 0.1 mM Phytic acid inhibited the polyphenol oxidase (PPO) from the apple juice by 99.2%. Consequently, the apple juice treated with phytic acid had significantly lower browning formation during processing and after 6 months of storage at room temperature compared with the control (p<0.05). Results indicate that this is a promising way to inhibit browning in apple juice.     

苹果原浆抗氧化防褐变及稳定性试验

新鲜苹果加工成果汁，由于酶促褐变或非酶促褐变常变色，呈褐色，内色或黑色。加入一定量的Vc或L－cys会抑制其褐变，在新鲜汁中加入不同的增稠剂，会提高其稳定性。     

Non-enzymatic browning in clarified cashew apple juice during thermal treatment: Kinetics and process control

The effect of thermal treatment on clarified cashew apple juice was studied at temperatures from 88 to 121 °C. Changes in colour measured with colorimetric parameters (reflectance spectra, colour difference and CIELAB), and the variation in ascorbic acid, 5-hydroxymethylfurfural (5-HMF) and sugar content were used to evaluate non-enzymatic browning. Kinetic models were applied to the changes in reflectance spectra, ascorbic acid and 5-HMF. The effect of temperature on kinetic constants was described by an Arrhenius type equation. The sugar content remained constant during thermal treatment and did not affect non-enzymatic browning, which was mainly affected by degradation of ascorbic acid. The kinetic models were used to optimise and control the thermal treatment for clarified cashew apple juice.     

包装材料对苹果浓缩汁贮藏期非酶褐变的影响

研究了苹果浓缩汁贮藏过程中,3种包装材料对褐变指数(A420)、氨基态氮、还原糖和5-羟甲基糠醛含量的影响。结果表明,3种包装材料对苹果浓缩汁的非酶褐变阻遏作用玻璃瓶最佳;20d内,PE/TIE/PA/TIE/PE5层共挤蒸煮袋>PE(聚乙烯)袋;20d后,PE袋>蒸煮袋。     

Phenolic profiling reveals the metabolite basis of flesh colour and fresh-cut browning in apple fruit

Flesh colour, which is affected by cultivars and browning, can largely impact consumer acceptance in fresh-cut apples. The study profiled phenolic metabolites from apple flesh of twenty-three cultivars by widely targeted metabolomics. Comparison among white- and yellow-fleshed cultivars showed fifteen phenolics, mainly quercetin 3-O-glucoside, hyperoside, hesperetin 5-O-glucoside and cymaroside, in white-fleshed apples were significantly higher than those in yellow-fleshed apples. It may indicate a metabolite basis of yellow and white flesh colour, and better potential nutrition in white-fleshed apples. In addition, ten phenolic metabolites including five cyanidin glycosides showed significant differences between the highest and the lowest browning groups, indicating them may be crucial in browning of fresh-cut apple. This work elucidates the differences of phenolic profiles among apple cultivars with different flesh colour and provides useful data to evaluate the suitability of apple for fresh-cut processing.     

Quality and antioxidant capacity of fresh‐cut apple wedges enriched with honey by vacuum impregnation

The effect of vacuum impregnation (VI) of fresh‐cut apple wedges with honey, in presence and absence of a browning inhibitor on physicochemical, sensory and antioxidant properties over 7 days of storage at 2–4 °C was studied. Infusion of wedges with honey resulted in very little weight change indicating loss of internal water and ingress of honey carbohydrates into the wedges, hence the correlation coefficients with soluble solids content (r = ?0.91) and dry matter (r = ?0.77). Water infused samples showed the highest water uptake resulting in an increase in weight of 30%. Browning (P < 0.001) and firmness (P < 0.001) of apple wedges were the quality parameters most affected by VI. Samples dipped in browning inhibitor prior AS1 showed slightly better performance than undipped wedges with regard to browning and firmness. Total phenol content and antioxidant activity were significantly (P < 0.001) lower for honey infused apple wedges.     

苹果汁中重金属检测方法研究进展

我国是苹果生产大国,其生产和消费规模均占全球50%以上。苹果汁作为苹果加工的主要形式,其营养丰富,味道鲜美。然而由于原料、技术与管理等问题,致使苹果汁经常出现褐变、农药残留、棒曲霉素、耐热菌超标、重金属污染等问题。随着人们对果汁安全性要求的不断提高,重金属超标问题越来越引起人们重视,故对重金属检测技术的开发成为重要的研究方向。针对苹果汁中重金属污染问题,本文综述了近年来重金属离子的检测方法,并对重金属检测技术的发展趋势进行了展望。     

浓缩苹果汁酶促褐变及其控制

酶促褐变是引起苹果浓缩汁色值降低、品质劣变的主要原因之一 ,本文介绍了浓缩苹果汁酶促褐变的三个必要生化条件 :酚类物质、多酚氧化酶 (PPO)和氧气 ,并综述了浓缩苹果汁生产中酶促褐变的控制方法 ,如加热钝化酶、调节pH值、添加酶或底物的抑制剂、使用膜技术、添加漆酶等 ,均能有效控制浓缩苹果汁的酶促褐变 ,提高果汁的品质     

苹果多酚组分及其生理功能研究进展

在前人研究的成果基础上,简要介绍了苹果多酚的含量分布、影响含量的因素及分子结构和生物合成途径,总结了苹果在加工过程中发生的褐变及抗氧化剂和多酚的关系,重点描述了苹果多酚的生理功能及影响这些功能的因素,概述了苹果多酚在各领域的应用概况。      

Pre-drying treatment of plant related tissues using plasma processed air: Impact on enzyme activity and quality attributes of cut apple and potato

During post-harvest processing of fresh cut and dried fruits and vegetables, polyphenol oxidase (PPO) and peroxidase (POD) need to be inactivated or inhibited in order to avoid undesirable browning reactions and loss of sensorial or nutritional quality. To meet this goal, the application of plasma processed air (PPA) offers a promising “gentle” alternative to traditional methods, such as pasteurization or the addition of anti-browning compounds. Using ambient air as process gas instead of an expensive noble gas, such as argon, exhibits a substantial improvement for the development of large-scale plasmas at ambient pressure and allows the indirect treatment of larger goods within a remote exposure reactor. In this study the ability of PPA to inactivate PPO and POD in complex food matrices and its impact on quality parameters, such as color, texture and cell integrity directly after freshly cutting and during storage of warm air dried and freeze dried produce was evaluated.The study evidently shows that PPA processing is capable of reducing the activity of PPO and POD in the freshly cut tissue from both apple and potato. Following exposure to PPA for 10 min the PPO activity was reduced by about 62% and 77% in fresh cut apple and potato tissue, respectively. POD, as the more temperature-stable enzyme, was even less stable upon PPA treatment for 10 min and was reduced by about 65% and 89% in fresh cut apple and potato tissue, respectively. Blackening of the potato tissue could be completely prevented by plasma treatment while a browning different from the habitual nature of enzymatic browning occurred upon exposure of the apple tissue to PPA. In both cases, the pH value on the tissue surface dropped to 1.5 while cell integrity and dry matter content were not significantly affected.Industrial relevanceThe quality and shelf life of freshly cut and dried fruits and vegetables greatly depend on the activity of naturally occurring enzymes which catalyze browning reactions at cut surfaces. This study shows that the application of PPA, as a promising nonthermal “pasteurization” technology, enables the inactivation of PPO and POD in complex food matrices. It further describes the impact of the PPA treatment on quality parameters of the freshly cut tissue from apple and potato and goes beyond on evaluating color, texture and enzyme activity in warm air dried and freeze dried tissue over a storage time of three weeks. The results contribute to the understanding and product-specificity of PPA-induced effects on quality and shelf life of fresh cut and dried fruit and vegetable produce and could be a basis for a possible industrial implementation.     

树脂法生产无色浓缩苹果汁的初步研究

采用吸附树脂除去苹果汁中的色素,脱去果汁的颜色,同时用离子交换树脂除去苹果汁中的氨基酸,从而基本控制了果汁的褐变,保持了果汁高的色值。