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.     

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。     

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。     

特拉蒙及新红星杂交后代苹果PPO特性及褐变影响因素

以特拉蒙及新红星杂交后代苹果45号、54号、87号及富士为试材,对其褐变度、酚类物质含量、水溶性蛋白含量、SOD活性、POD活性及PPO特性等指标进行了分析。结果表明:各指标均存在明显差异,酚类物质含量、水溶性蛋白含量和PPO活性是影响杂交后代苹果褐变的主要因素。     

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。     

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.     

Nonenzymatic browning reactions of retro-aldol degradation products of carbohydrates

 Methylglyoxal and glyceraldehyde were used to demonstrate the involvement of retro-aldol degradation products of carbohydrates in browning (A ₄₂₀), the formation of hydroxymethylfurfural (HMF), and the extent to which the mechanism of browning proceeds by homolytic or heterolytic pathways in the caramelization and Maillard reactions of mono- and disaccharides. The amino component of Maillard systems is required for the retro-aldol cleavage of D-glucose. The short-chain α-dicarbonyl compounds so formed appear to dominate not only the formation of brown products but also the mechanism of the browning of D-glucose under these conditions, even if only small amounts are formed. Evidence is presented to link the formation of free radicals in the browning of glucose to reactions of the retro-aldol products. A novel reaction pathway is suggested for the formation of HMF from glyceraldehyde. Received: 9 October 1998 / Revised version: 15 December 1998     

微波法提取苹果渣中多酚的工艺研究

以乙醇作为提取溶剂,研究了微波法提取苹果渣中多酚的工艺条件。主要探讨了溶剂浓度、微波功率、提取时间、料液比、物料颗粒等因素对多酚提取的影响,结果表明,微波法从苹果渣中提取多酚的最佳工艺条件为乙醇浓度60%、物料颗粒40目、液料比1∶10、微波功率350W、提取时间90s,此条件下从苹果渣中提取的多酚浓度可达245.31mg/100g,明显优于回流提取法和超声波提取法。     

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.     

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。     

Non-enzymatic browning and estimated acrylamide in roots,tubers and plantain products

Acrylamide has been discovered in foods, especially high carbohydrate foods that are dry-cooked (baked, fried or roasted) at high temperatures which also create the conditions for non-enzymatic browning. Baking, frying and roasting are common food preparation methods in Ghana. Fifteen different high carbohydrate foods in Ghana, that undergo dry-cooking, have been investigated for non-enzymatic browning and acrylamide production. The products that showed notable non-enzymatic browning and acrylamide levels include fried sweet potato, plantain chips from the fresh produce, with their respective non-enzymatic browning and acrylamide values as 0.095 ± 0.006 optical density (OD), 1043 ± 47.6 parts per billion (ppb); 0.034 ± 0.03 OD, 568 ± 22.9 ppb. Roots and tuber products had relatively high non-enzymatic browning and acrylamide levels while plantain products showed low levels of non-enzymatic browning and acrylamide.     

苹果渣中多酚物质的福林法测定

以没食子酸为标准品研究了福林法测定苹果渣中多酚物质含量的适宜条件。结果表明,当福林试剂与10%Na2CO3体积之比1∶1,反应温度25℃,反应时间120min时,多酚含量在5～30μg范围内与吸光值呈良好的线性关系。测定方法的平均回收率为106.5%,RSD为0.49%,有较好的准确度和精密度。     

天然抗氧化剂——苹果多酚的研究与应用

苹果多酚是苹果中一种天然活性成分，具有很强的抗氧化能力和生理功能，可以广泛应用于食品和医药领域。本文主要介绍了苹果多酚的组成、性状、安全毒理、提取纯化方法、生理功能及其在食品中的应用等，并展望了其发展前景。     

Enzymatic Browning in Apple Pulps

Enzymatic browning in Golden Delicious apple pulp was studied as related to degree of ripeness and temperature (3.5–31°C). Green apple pulp showed the highest rate of browning. This was attributable to differences in ascorbic acid (AA) content and polyphenoloxidase activity in young fruits. The rate of browning determined by CIE L* measurements followed complex temperature dependent kinetics, represented by a multiple linear effects with log time. Equal changes in L* parameter yielded straight lines in a log temperature vs log time plot. Inhibition with AA caused an initial slow rate of browning and a well defined break point associated with exhaustion of antioxidant properties of the AA. The greater the AA concentration the longer the initial period.     

Enzymatic Browning Inhibited in Fresh and Dried Apple Rings by Pineapple Juice

Sliced apple rings were treated with water (control), canned pineapple juice, frozen pineapple juice, ion-exchanged pineapple juice, frozen orange juice, ascorbic acid, a commercial antibrowning preparation or sodium bisulfite. The rings were either left exposed to air, vacuum packaged, or dehydrated. Browning was measured calorimetrically and by visual examination over extended periods of time. Pineapple juice was an effective browning inhibitor in both fresh and dried apples. Pineapple juice was fractionated using various size and charge separation procedures. All fractions inhibited enzymatic browning of crude apple extracts by at least 26%. Results indicate that the inhibitor is a neutral compound of low molecular weight.     

Enzymatic browning in sliced and puréed avocado: A fractal kinetic study

Modelling of browning is essential to evaluate the effectiveness of the processes applied to obtain fresh-appearance foods and also to determine their shelf life. Computer vision and the fractal kinetic method were used to quantify browning in three avocado cultivars. Samples (avocado slices and purée) were stored at 4 °C and surface images were captured in the tiff format. Browning kinetic was derived from images using the L^∗ mean method and the fractal method. In another experiment, inhibitor kinetic was also quantified, using the polyphenol oxidase activity method (in purée samples) with 0.1%, 0.5% and 1% of sodium bisulfite. In the results for avocado slices, kinetic rate derived by the fractal kinetic method was higher than that obtained with the L^∗ mean method, but the opposite was observed when the avocado was pulping (avocado purée). Kinetic quantified by the fractal method was similarly inhibited by bisulfite, when compared with the L^∗ mean value or PPO activity value methods. In general, the fractal method can be used to record browning kinetic and to discriminate between avocado cultivars, initial structural state of the sample (slice or purée), or in experiments using browning inhibitors.     

Control of Enzymatic Browning in Pre-peeled Potatoes by Surface Digestion

Feasibility of lye digestion to remove surface tissues from peeled potatoes prior to treatment with browning inhibitors to extend shelf-life was investigated. Russet and round-white potatoes were digested in 14–20% NaOH at 35–55°C for 1–13 min. After removal of digested tissue, tubers were treated with ascorbic acid-based browning inhibitor. Browning was measured by tristimulus calorimetry. Digestion extended shelf-life of high pressure steam- and abrasion-peeled potatoes to 13–15 days at 4°C, compared to 3–11 days for undigested controls. Digestion resulted in weight losses of 12–26%, depending on treatment conditions. Lye digestion in conjunction with conventional browning inhibitors represents a viable alternative to sulfiting pre-peeled potatoes.     

曲酸对苹果汁酶促褐变抑制作用的研究

将几种护色剂在苹果破碎时加入,考察它们对苹果汁的防褐变作用。L-半胱氨酸、曲酸对苹果PPO的抑制作用最强,防褐变效果最好。曲酸是值得推广的防褐变剂。     

浑浊苹果汁加工中苹果PPO热失活条件的研究

研究了热处理苹果汁(加或不加防褐变剂)、苹果浆使其中的PPO完全及部分失活所需要的温度和时间。结果为:在90℃处理苹果汁15s可使其中的PPO完全失活,而对于苹果浆则需要90℃处理20s以上。加了防褐变剂的苹果汁经90℃处理10s可使其中的PPO完全失活;此外,经80℃处理30s以上虽不能使其中的PPO完全失活,但添加的防褐变剂及果汁自身的pH值可抑制残余的PPO从而防止酶促褐变的发生。70℃处理苹果汁40s不能防止其中的酶促褐变。