Antimicrobial Treatments for Minimally Processed Cantaloupe Melon

ABSTRACT: Efficacy of decontamination treatments in reducing endogenous microbial populations on cantaloupe and in extending fresh-cut shelf-life were investigated. Composite rind plug samples were washed with water or solutions of sodium hypochlorite, H₂O₂, commercial detergent formulations containing dodecylbenzene sulfonic acid and phosphoric acid, or trisodium phosphate, and surviving microbial populations determined. Fresh-cut cubes were prepared aseptically from whole melons given similar treatments, and their visual appearance and bacterial population determined during storage at 4 °C. Population reductions on washed rind plugs were < 1 log with water, 1 to 2 logs with washing and sanitizing agents applied individually, and 3 logs with some sequential treatments with H₂O₂. H₂O₂ applied at 50 °C was superior to other whole-melon treatments, yielding a fresh-cut shelf-life of > 2 weeks.     

Shelf-Life Extension of Fresh Mushrooms (Agaricus bisporus) By Application of Hydrogen Peroxide and Browning Inhibitors

ABSTRACT: An experimental washing process for fresh mushrooms entailing immersion in 5% H₂O₂, followed by application of a sodium erythorbate-based browning inhibitor, was optimized, scaled up, and made continuous. The laboratory process described previously was modified by adding a pre-wash step using 0.5% to 1% H₂O₂, increasing the wash solution H₂O₂ concentration from 3% to 5%, and substituting 4% sodium erythorbate + 0.1% NaCl for the more complex browning inhibitor formulation used previously. A continuous, commercial-scale washing facility was built to test the new process. Mushrooms washed by this process were free of adhering soil, less subject to brown blotch than conventionally washed mushrooms, and at least as resistant to enzymatic browning as unwashed mushrooms during storage at 4 °C. Storage at 10 °C accelerated development of brown blotch and browning.     

Control of Enzymatic Browning in Processed Mushrooms (Agaricus bisporus)

Control of polyphenol oxidase (E.C. 1.14.18) activity by the use of citric acid was investigated. The enzyme was inactivated at pH 4.0 and was stable to 10 min exposures at 25°C in the pH range 4.0–8.0. At pH 6.5 the enzyme was active at 45°C but not at 70°C and thermal inactivation followed pseudo first-order kientics. At pH 6.5 the activation energy (E_a) for enzyme inactivation was 41.1 Kcal/mole while at pH 3.5 two rate constants and hence two values for E_a were observed. Between 0–5 min E_a for inactivation of polyphenol oxidase was 8.7 Kcal/mole and >5 min Ea was 21.8 Kcal/mole.     

Color of Minimally Processed Potatoes as Affected by Modified Atmosphere Packaging and Antibrowning Agents

Minimal processing of potatoes was studied by using different treatments of cut potatoes in combination with modified atmosphere packaging. Different packaging materials and peeling methods were evaluated. An L-cysteine (0.5%) and citric acid (2%) mixture prevented browning of potatoes effectively. Active modification of the atmosphere inside the package was necessary to achieve extended shelf-life. Nitrogen flushing was more effective than other gas treatments with a highly permeable multilayered polyolefin packaging material. Hand peeling and lye peeling resulted in better quality, but abrasion peeling was undesirable for fresh potatoes. The shelf-life of the minimally processed products could be extended to nearly 3 wk under refrigerated storage.     

Browning Inhibition in Fresh-Cut Pears

Treatments to control browning and maintain quality of fresh-cut pears were evaluated. Pear wedges were dipped in solutions containing sodium erythorbate, CaCl₂ and 4-hexylresorcinol; packed in air or with a modified atmosphere (MAP); and stored at 4°C. Samples were evaluated for browning, microbial spoilage, and presence of off-flavors or loss of firmness. For treatments to be successful, pears had to be above a minimum firmness of 4 kg (d'Anjou) or 5 kg (Bartlett) when treated. Inhibitor treatments, in conjunction with MAP, controlled browning and maintained quality of fresh-cut Bartlett and d'Anjou (but not Bosc pears) for 12–14 days.     

烟草酶促棕色化反应及调控技术研究进展

由多酚氧化酶(PPO)介导的酶促棕色化反应是烟草调制、醇化过程中普遍存在的问题,严重影响烟叶质量。本文介绍了影响酶促棕色化反应的因素,对农学、物理、化学和生物学等酶促棕色化反应调控技术进行了综述,探讨了各种调控方法的优缺点。     

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.     

固载二氧化氯对最小加工竹笋品质和生理的影响

采用固体二氧化氯处理最小加工竹笋,于4 ℃贮藏12 d。以呼吸强度、颜色、硬度、苯丙氨酸解氨酶（PAL）、多酚氧化酶（PPO）、过氧化氢酶（CAT）、抗坏血酸过氧化物酶（APX）和谷胱甘肽还原酶（GR）活性、超氧阴离子自由基生成速率、总抗氧化能力和菌落总数等为指标,研究0.50 mg/L二氧化氯对最小加工竹笋品质和生理的影响。结果表明：用0.50 mg/L的二氧化氯处理,可降低最小加工竹笋呼吸强度,抑制竹笋贮藏期间硬度的上升;延缓PAL、PPO活性的增加;提高CAT、APX和GR的活性,降低超氧阴离子自由基的生成速率,提高总抗氧化能力。     

切分蔬菜保鲜工艺研究

通过测定切分蔬菜加工贮藏过程中营养成分和褐变度的变化以及感官评定 ,探讨切分蔬菜品质保持技术。试验结果表明 ,影响切分蔬菜品质的因素有切分大小、清洗、脱水、包装形式以及保存温度和时间等。     

Tyrosinase, Laccase, and Peroxidase in Mushrooms (Agaricus, Crimini, Oyster, and Shiitake)

Enzyme assays and electrophoresis were used to monitor the activity of tyrosinase, laccase, and peroxidase in Agaricus bisporus (common cultivated button mushrooms and Crimini mushrooms), Oyster, and Shiitake mushrooms. The three enzymes could be differentiated using specific substrates and inhibitors. Tyrosinase seemed to be the major phenol oxidase in the Agaricus strains, while Oyster and Shiitake mushrooms had much lower levels. Peroxidase activity was low or undetectable in all types examined. Control of enzymatic browning in different mushroom types may depend upon the distribution of different oxidases within any given type.     

枇杷果实酶促褐变控制研究

枇杷果实在贮藏及加工过程中极易产生酶促褐变。本文采用分光光度法,研究了几种因素对枇杷果实多酚氧化酶活性的影响。结果表明:多酚氧化酶的最适 pH 为 6.3,抗坏血酸、L-半胱氨酸、柠檬酸、草酸、柠檬酸-抗坏血酸混合物可明显抑制该酶活性。     

柠檬酸和异抗坏血酸钠处理对冷藏鲜切菠萝质量的影响

采用响应面方法,研究柠檬酸、异抗坏血酸钠处理和冷藏时间对鲜切菠萝颜色、硬度、失重和包装内气体组成的影响。新鲜菠萝片分别用0%～1.0%的柠檬酸和异抗坏血酸钠处理3min,然后装在塑料泡沫碟中,用PVC薄膜密封,在5℃冷库中贮藏0～14d。结果表明,异抗坏血酸钠显著地减缓L、a、b、失重(p≤0.001)和硬度(p≤0.1)的变化,但对包装内O2和CO2含量没有影响。柠檬酸对L、硬度和失重有影响(p≤0.1)。所有考察的指标在贮藏过程中均显著变化(p≤0.01)。建立的回归模型可充分预测柠檬酸、异抗坏血酸钠处理和冷藏时间对鲜切菠萝质量的影响。     

双孢蘑菇酶促褐变特性及褐变的控制

为有效控制双孢蘑菇褐变,研究pH值、温度、底物浓度以及抑制剂对双孢蘑菇的多酚氧化酶(polyphenol oxidase,PPO)活性的影响。结果表明：以邻苯二酚为底物,双孢蘑菇PPO最适反应pH6.8,最适反应温度20℃,最适反应底物浓度为0.06mol/L,米氏常数Km为0.1072mol/L。采用计算机图像处理技术对双孢蘑菇褐变程度进行定量检测,得出对双孢蘑菇贮藏保鲜效果较好的褐变抑制剂及其最佳配比为0.30mmol/L半胱氨酸、0.06％抗坏血酸、0.05%乙酸。     

果酒发酵中褐变机理及其控制的研究进展

在果酒的发酵过程中,褐变现象导致了果酒的色泽、香味发生变化,降低了产品的感官特性,严重影响了果酒的品质,是果酒生产中长期存在的棘手问题。因此,探究果酒褐变的机理,并同时寻求能够有效控制果酒褐变的方法有着重要的意义。本文对近些年来该领域的研究情况进行了报道,并从果酒褐变的机理和褐变现象的控制两个方面作一综述,以期为果酒行业的发展提供有益参考。     

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。     

酶解法提取龙虾废弃物中蛋白质的工艺研究

采用酶解法对龙虾加工废弃物提取蛋白质的工艺进行了研究.通试验获取酶解提取蛋白质最优工艺条件为:选用碱性蛋白酶为提取剂,酶解时间3h,加酶量1.5%,pH值8.0,酶解温度50℃,液料比为3:1(m/V),此条件下蛋白质提取率为45.76%.     

Enzymatic Browning Inhibition in Cloudy Apple Juice by Electrodialysis

Cloudy apple juice (pH 3.8) was acidified to pH 2.7, at 16–24°C and at a constant current density of 40 mA/cm², in an electrodialysis (ED) unit composed of an AB electrocell with three compartments, a bipolar membrane (Neosepta BP-1) and two ion-exchange membranes (anion- and cation-exchange). The treatment inhibited 81% of the activity of polyphenoloxidase and slowed enzymatic browning, indicated by a decrease in indice “a” and an increase in “L” on the Hunter Lab colorimeter scale. During ED treatments, conductivity and K⁺ concentration in apple juice decreased by, respectively, 21% and 86%.     

Phenoloxidases in Portabella Mushrooms

Tyrosinase, laccase, and peroxidase activities were detected in crude extracts from commercial Portabella mushrooms. Tyrosinase was present in larger amounts than either laccase or peroxidase. Catechol showed the greatest activity as a substrate for tyrosinase while diaminobenzidine was found to be a good substrate for estimating laccase and peroxidase activity. Two tyrosinase and three laccase isoforms were detected after native electrophoresis. At least 10 tyrosinase isoforms were observed after isoelectric focusing. The distribution of these forms varied in different tissues. Browning reactions in Portabella mushrooms are a result of tyrosinase rather than laccase or peroxidase.     

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.     

翠冠梨贮藏过程中酶促褐变及生理生化的变化

酶促褐变是一种严重影响梨采后贮藏品质的生理病害。本文以翠冠梨为试材，对其在A、室温贮藏；B．冷藏(0℃)；C．冷藏(0℃) 0．04mm聚乙烯薄膜袋(PEF)贮藏过程中酶促褐变和生理生化变化进行了研究。试验结果表明，(1)A、B和C处理的翠冠梨在贮后16d，好果率分别为25．12％、87．27％、98．64％。低温处理(0℃)能提高超氧化物歧化(SOD)活性，抑制活性氧(O2^.1)、丙二醛(MDA)的生成速率，延缓果实衰老软化。(2)翠冠梨在贮藏期间先进行酚类物质合成，然后发生降解，多酚氧化酶(PPO)活性呈先升后降趋势，酚类物质的减少和褐变同时发生，PPO促进酚类物质氧化，结果导致褐变。