果蔬酶促褐变与抑制

果蔬褐变是指水果和蔬菜加工及其制品在贮藏过程中,产生果蔬组织颜色变得晦暗或变成褐色的现象。褐变不仅影响果蔬食品原有的色泽,而且影响其风味和营养价值。随着人们生活水平的不断改善,对食品的感官标准提出了愈来愈高的要求,大多数情况下,褐变是不希望出现的变化,由此,褐变的产生与抑制受到食品加工行业的重视。 果蔬褐变的产生,有因酶的作用而变褐的     

淮山褐变机理及其控制技术研究进展

淮山是一种营养价值极高的药食同源食品。褐变是淮山加工贮藏过程中影响其品质的主要问题之一,有效控制淮山褐变,保持其色泽和营养特性,提高其货架贮藏期,对保障淮山品质和提高消费者接受性具有重要意义。在已有研究的基础上,本文阐述了淮山酶促褐变与非酶褐变的相关机理,围绕酚类底物、酶及氧气等酶促褐变三要素阐述了淮山酶促褐变机理,并对淮山加工及贮藏中的美拉德反应和焦糖化非酶褐变机理进行了介绍;综述了不同褐变控制技术对淮山褐变的控制效果,分析现有问题,并对未来前景进行了展望,以期为淮山褐变控制技术的研究和应用发展提供参考。     

果蔬采后色素物质代谢调控研究进展

色泽是果蔬采后主要的感官品质之一,它是消费者判断果蔬成熟度、新鲜度、商品可接受度及营养价值的重要参数。决定果蔬采后色泽的主要色素有叶绿素、类胡萝卜素和花色苷,它们的代谢使果蔬呈现红、橙、黄、绿、蓝、紫等多种颜色。果蔬采后常发生的褪绿、褐变、黄化和白化等转色现象,也与果蔬色素代谢过程密切相关。研究果蔬采后色素代谢及其调控具有重要意义。本文综述了物理因子、化学因子和生物技术等在调控果蔬采后色素代谢方面的作用和机理,旨在为采后果蔬色泽的有效调控提供一定的理论参考。     

果蔬的褐变及其控制方法

果蔬贮藏和加工过程中的褐变是影响其品质的一个重要因素.褐变产生的因素较多,其中酶促褐变是果蔬褐变的最主要原因,也是果蔬贮藏和加工品质保证的主要障碍.概述褐变产生的原因及其控制的方法.     

果蔬制品的非酶褐变与控制途径

食品的非酶褐变作用,广泛存在于加工和贮藏过程中。其中有些食品,如果对非酶褐变控制的适当,将会产生有利于食品色泽、风味的化合物。但也有些食品,常常由于非酶褐变作用的结果,严重地影响制品的外观和风味,因此,对于果蔬制品,这种非酶褐变反应是十分不利的,     

果蔬茶贮藏与加工过程品质调控研究现状及趋势

果蔬茶产业是我国现代农业产业体系和国民经济的重要组成部分,然而存在产后损失大,产品附加值低,综合利用水平不高等问题,制约了产业的高质量发展。实现果蔬茶贮藏加工过程的品质调控,是减损增值的关键。本文综述果蔬茶贮藏加工过程中颜色、香气、滋味、质构和营养品质调控研究现状,提出未来研究的关键科学问题为果蔬茶品质劣变的贮藏生物学基础,绿色贮藏加工技术对果蔬茶品质调控的基础理论,果蔬茶营养物质生物利用度提升和健康效应机理等3个方面,指出多维度解析品质调控机制,绿色加工技术集成创新,多学科交叉与智能化的新方向、新理念、新趋势。本文将为果蔬茶贮藏加工品质调控相关研究和产业高质量发展提供重要理论依据。     

影响百合色泽变化因素的研究

百合在采后贮藏过程中会发生明显的褐变和紫红色变。根据影响果蔬色泽变化的主要因素:酶褐变、非酶褐变和色素变化,研究了百合采后贮藏过程中褐变度、还原糖、蛋白质、酸度以及多酚氧化酶(PPO)、过氧化物酶(POD)活性等参数的变化规律及与百合色变的影响关系。研究结果表明:PPO和POD参与了百合酶促褐变过程并起着重要的作用;还原糖和蛋白质发生羰氨反应可能是引起百合的非酶褐变的原因;百合的紫红色变可能是由于无色花色素氧化转变成呈色花色素引起的。     

褐变反应对果蔬加工与贮藏的影响

在果蔬加工与其制品的贮藏过程中,可能会产生果蔬组织颜色变得晦暗或变成褐色,不同品种的果蔬制品,由于糖原料、加工和贮藏条件的改变,有时甚至会产生伴有杂色的褐变现象,影响了果蔬固有的令人喜爱的外观。这种褐变反应对于果蔬加工、贮藏是一个不利的化学反应,长期以来受到食品加工者的童视。     

副食品酿造过程中的褐变

褐变(Browning)普遍存在于食品加工贮藏过程中,它不仅是色泽的变化,而且食品的风味及营养成分也会有相应的改变。在一些食品中,如水果、蔬菜褐变是有害的,会使食品外观变差,营养成分降低;而在另一些食品中,适当的褐变是形成良好风味和色泽的必要条件。如生产酱油、红茶、可可豆以及面包在焙烤过程中生成的焦黄色和香气同样都是褐变作用的结果。因此,我们弄清楚褐变作用的机理和发生条件,根据具体需要对褐变加以控制,有着十分重要的实践意义。     

食品的酶促褐变及其控制

褐变是食品比较普遍存在的一种变色现象。食品在加工或贮藏过程中,原有的颜色变深,或者变成褐色,就称为褐变。褐变对某些食品是有益的,如酱油、咖啡、红茶、啤酒以及面包和糕点等,褐变形成了良好的风味和色泽,这是人们希望的。但是,许多食品,特别是水果和蔬菜,褐变不受人们的欢迎,褐变不仅影响食品的外观和风味,而且降低食品的营养价值。因此,了解食品的褐变机理,寻找抑制或控制褐变的途径,在食品工业中具有重要意义。     

加工和贮藏对果蔬营养成分变化及抗氧化活性影响的研究进展

水果和蔬菜是维生素、非维生素植物化学物质和抗氧化活性的重要来源,因此膳食指南推荐人们摄入足够多的水果和蔬菜,但是这里并没有区分是新鲜果蔬还是加工过的果蔬。然而,人们消费的大部分果蔬都是加工过的,与同样的新鲜果蔬相比,它们的营养物质、功能性成分和抗氧化活性或许不同。讨论了不同罐装、烹调、常温和低温贮藏以及冻藏等贮藏和加工方式对果蔬中维生素、非维生素植物化学物质和抗氧化活性的影响。大量研究表明,加工和贮藏造成了大多数种类果蔬植物化学物质和抗氧化活性的损失。这些信息将有助于指导人们使用贮藏和加工过的水果和蔬菜。     

Effects of storage condition and domestic cooking on the quality and nutrient content of African leafy vegetables (Cassia tora and Corchorus tridens)

BACKGROUND: The main objective of this research was to determine changes in nutrient content of two African leafy vegetables, Cassia tora and Corchorus tridens, on cooking and storage under different temperature conditions, i.e. room storage (20 °C), refrigerated storage (4 °C) and frozen storage (?18 °C). RESULTS: The leafy vegetables were analysed for moisture, colour (Hunter L, a, b), texture, total chlorophyll, ascorbic acid, dehydroascorbic acid and total phenolics. Results indicated that the degradation of ascorbic acid was highest as a result of frozen storage, followed by room temperature storage. The dehydroascorbic acid content was correspondingly high in frozen stored leafy vegetables, whereas it was undetectable in the room temperature and refrigerated stored materials. The total phenolic content of the leaves increased with storage time while the total chlorophyll content decreased under all storage conditions. Domestic cooking resulted in significant additional losses of ascorbic acid following storage under all temperature conditions, with only 1–10% retention in the leaves and 50–60% retention in the cooking water. The green colour of the leafy vegetables was retained best under refrigerated and frozen storage, while the peak force and toughness of the leaves increased upon storage under all conditions. The moisture content of the leafy vegetables did not show any significant difference on storage. CONCLUSION: This study is one of few to report nutrient content changes on the same raw material stored under various temperature conditions and cooked domestically. Refrigerated storage resulted in the highest retention of ascorbic acid and green colour in the leafy vegetables. Copyright © 2009 Society of Chemical Industry     

Effects of pretreatments on quality attributes of long-term deep frozen storage of vegetables: a review

As one of the essential parts in human diet, vegetables are important in health keeping and their consumption increases continuously. Due to their highly perishable nature, the shelf life of fresh vegetables is considerably short, due to cellular respiration, microorganism, enzyme reaction, oxidation and so on. Therefore, short- and long-term storages of vegetables are required and various methods and technologies are applied for different commercial goals. For long-term storage, deep frozen storage is one of the most widespread used preservation methods for vegetables, as under temperatures low enough, the rate of most deteriorative reactions and microbial activities are significantly reduced. This review provides a critical comprehensive summary of long-term storage (≥6 months) vegetables under low temperatures (≤??18?°C), and effects of the storage methods on various quality attributes of vegetables, such as texture, colour, contents of ascorbic acid, chlorophyll and carotenoids. Besides, the impacts of common pretreatments prior to freezing on the subsequent frozen storage are also briefly discussed. The current review shows that although some important biochemical attributes are more or less deteriorated and the quality loss of them is inevitable, a substantial portion of quality attributes appear to be stable during long-term deep frozen storage especially the physical parameters. Meanwhile, pretreatments prior to freezing, such as blanching process, also show significant influence on quality preservation in subsequent storage. Therefore long-term deep frozen storage can be applied as an effective storage method under proper conditions of pretreatments and storage.     

Factors influencing levels of phytochemicals in selected fruit and vegetables during pre- and post-harvest food processing operations

Phytochemicals are important natural bioactive compounds of fruit and vegetables and are widely recognised for their nutraceutical effects and health benefits. This review analyses different factors influencing the level of phytochemicals in selected fruit and vegetables at different processing stages in the production chain. The level of phytochemicals present in fruit and vegetables may vary within and across cultivars. Available literature correlates the level of phytochemicals with many factors including cultivar type, environmental and agronomic conditions, harvest and food processing operations, and storage factors. The optimisation of food processing and storage factors is an essential step to reduce the degradation of phytochemicals for potential health benefits. Cultivar selection and maturity at harvest may be critical for food processors to maintain high levels of phytochemicals in fruit and vegetables.     

绿色蔬菜的脱色机理及护色方法

绿色蔬菜在加工过程中易脱去绿色 ,从而影响其感官品质。本文对脱色机理进行初步探讨 ,对不同的护色方法进行比较 ,结果证明 ,采用 Cu2 或 Zn2 溶液浸泡处理效果好。实验最佳 [Cu2 ]为 30 0 mg/kg,[Zn2 ]为 50 0 mg/kg,浸泡时间为 2 4 h     

钙在果蔬生产加工应用中的研究进展

钙是构成植物细胞壁的重要元素,也是构成质膜的重要成分,它不仅影响果实品质,而且在延缓果蔬的衰老方面有较好抑制的效果。在生产加工中可以通过采前喷施钙肥或采后浸钙来提高果蔬品质,增加产量,另外在延长果蔬贮藏期的同时,还可保持好的品质,减少果蔬采后的损耗量。文章综述果实细胞中的钙的存在形式及钙在果蔬加工中的应用进展,以期为钙在果蔬加工中的合理利用提供理论参考。     

Impact of the industrial freezing process on selected vegetables -Part II. Colour and bioactive compounds

In the present study, the impact of the different steps (i.e. blanching, freezing, storage following the industrial freezing process and the final cooking prior to consumption) of the industrial freezing process was evaluated on colour, chlorophylls, lutein, polyphenols and ascorbic acid content of asparagus, green beans and zucchini. In addition, the domestic boiling of raw samples was compared with the boiling of frozen storage vegetables.Results showed that the blanching treatment retained phytochemicals in all studied green vegetables and the frozen storage up to 2 months did not negatively affected phytochemicals, in particular lutein and flavonoids in almost all samples. On the contrary, colour significantly changed during blanching and frozen storage. The changes of b* (yellowness) and the shift of H° (hue angle) were not coherent with the increase of pheophytin. In addition, the greenness (− a*) was found to increase with the exception of boiled samples in all vegetables. Generally, in boiled frozen vegetables there was a better or comparable retention of bioactive compounds with respect to raw ones, and this was especially true for green beans and zucchini. Colour changes after cooking did not exhibit the same trends among vegetables, being more remarkable for frozen asparagus in comparison with those boiled from raw, but overall comparable for green beans and zucchini.In conclusion, the overall results of the present study suggest that, when the industrial freezing process is well performed, the boiled frozen vegetables do not have a lower nutritional value than the fresh ones.     

Effects of pre‐freezing,puree content and pasteurisation regime on colour stability of strawberry nectar made from puree

BACKGROUND: Heat treatment during processing of strawberry products has been proposed to negatively affect colour stability. Moreover, the role of enzymes with respect to colour stability is ambiguous when consulting the existing literature. The aim of the present study was to investigate the impact of various processing parameters (pre‐freezing, puree content, pasteurisation temperature and heating time) on the colour stability and anthocyanin monomer and L ‐ascorbic acid contents of strawberry nectars made from puree. In addition, the effect of different enzyme activities on colour stability during storage of strawberry nectars was investigated. RESULTS: Pre‐freezing of strawberries before processing had a significant positive effect on the colour stability of nectars made from puree. No significant effect on colour stability was found for higher puree contents. Increasing both the pasteurisation temperature and the heating time had a significant positive effect on colour stability. Results showed that colour degradation during storage was mainly due to residual enzyme activities. The shelf‐life of strawberry nectar could be extended about fivefold by adding an enzyme inhibitor. CONCLUSION: The colour stability of strawberry nectar made from fresh puree may be improved to some extent by an appropriate pasteurisation regime. Enzymes play an important role in colour degradation during storage of the nectar. Inactivation of these enzyme activities, however, could not be achieved even after a heat treatment at 90 °C for 60 min. Copyright © 2008 Society of Chemical Industry     

基于叶绿素的果蔬护绿方法研究进展

叶绿素是存在于绿色植物中的一种独特而重要的营养物质,在果蔬贮藏与加工过程中,如何保护叶绿素是一大难题.本文对叶绿素的性质、叶绿素稳定性的影响因素及果蔬护绿技术等进行了综述.     

Effects of high hydrostatic pressure processing and subsequent storage on phenolic contents and antioxidant activity in fruit and vegetable products

Fresh fruits and vegetables have been reported to possess a variety of bioactivities partly due to their high abundance of phenolics. However, traditional thermal pasteurisation during fruit and vegetable processing typically induces a pronounced loss of phenolic compounds. In contrast, nonthermal pasteurisation techniques, especially high hydrostatic pressure (HHP) processing, are beneficial to the retention of phenolics. In addition to more effectively keeping original freshness, flavour and colour of fruit and vegetable products to the greatest extent, in most cases, HHP processing and subsequent storage more effectively sustain the levels of phenolic compounds and antioxidant activity in fruit and vegetable products compared with thermal pasteurisation. Therefore, HHP processing has a huge potential to preserve fruit and vegetable products rich in phenolic compounds.