紫外线处理对鲜切菜生理的影响

将紫外线照射引入鲜切菜的鲜切加工过程,通过研究紫外线不同照射时间对维生素C、呼吸强度、失重率和可溶性蛋白的影响,得出鲜切菜合适的杀菌方法和保藏措施。实验表明：当照射40rain时,Vc的保存率高、呼吸强度降低、失重率较小、可溶性蛋白含量高。     

Effect of hydrogen peroxide on quality of fresh-cut tomato

ABSTRACT:  The effect of hydrogen peroxide (H₂O₂; 0, 0.1, 0.2, and 0.4 M) on selected nutritional quality of fresh-cut tomato was investigated. Microbial population of tomato slices stored at 10 °C and treated with H₂O₂ was lower than the control by 1-(0.2 and 0.4 M) and 5-log (0.4 M), 3 and 7 d after processing, respectively. Dipping fresh-cut tomato into H₂O₂ resulted in reduced phenolic and antioxidant levels after 7 d in storage by at least 5% and 20%, respectively, and produced an initial decline in vitamin C and lycopene. Change in color values in the H₂O₂ treatments were associated with reduced carotenoid content. Our results confirmed antimicrobial benefits of H₂O₂ but revealed a compromise in antioxidant and carotenoid contents of fresh-cut tomatoes.     

化学保鲜在国外鲜切果蔬上的应用进展

近年来,随着收入水平提高和生活节奏加快,鲜切果蔬为越来越多的人所接受。在介绍鲜切果蔬定义的基础上,着重介绍了鲜切果蔬化学保鲜剂包括消毒清洗剂、生理调节剂、钙类保鲜剂、抗褐变剂和抗菌剂5种保鲜剂对鲜切果蔬的影响及作用机理,同时就保鲜剂的使用方法进行了阐述。最后,对鲜切果蔬的发展前景及注意事项提出了几点看法。     

鲜切果蔬微冻技术的研究进展

鲜切果蔬具有天然、便利、营养、保健以及口感清脆爽口等优点,深受国内外快餐业、旅游业、零售业等行业青睐。但鲜切果蔬贮藏品质损耗严重,保鲜期限短,一直是困扰其工业化发展的瓶颈因素之一。目前,国内外研究者试图采用各种物理、化学方法改善果蔬的贮藏品质问题。虽然这些方法在杀菌或在改善质量方面取得一定成效,但在满足人们对果蔬天然、高营养、安全、较长的保鲜期限等综合品质的需求方面存在局限。微冻技术以其突出的保鲜效果,成为低温保鲜领域的研究热点。而关于微冻技术在果蔬保鲜上应用效果的报道还很少。基于此现状,本文从果蔬保鲜技术的研究现状、微冻保鲜作用效果及组织损伤机制3方面,探究了微冻技术在鲜切果蔬上的应用前景。     

Flavor quality of fruits and vegetables

Fruits and vegetables are important sources of vitamins, minerals, dietary fiber, and antioxidants. The relative contribution of each commodity to human health and wellness depends upon its nutritive value and per capita consumption; the latter is greatly influenced by consumer preferences and degree of satisfaction from eating the fruit or vegetable. Flavor quality of fruits and vegetables is influenced by genetic, preharvest, harvesting, and postharvest factors. The longer the time between harvest and eating, the greater the losses of characteristic flavor (taste and aroma) and the development of off‐flavors in most fruits and vegetables. Postharvest life based on flavor and nutritional quality is shorter than that based on appearance and textural quality. Thus, it is essential that good flavor quality be emphasized in the future by selecting the best‐tasting genotypes to produce, by using an integrated crop management system and harvesting at the maturity or ripeness stage that will optimize eating quality at the time of consumption, and by using the postharvest handling procedures that will maintain optimal flavor and nutritional quality of fruits and vegetables between harvest and consumption. Copyright © 2008 Society of Chemical Industry     

Using antibrowning agents to enhance quality and safety of fresh-cut avocado treated with intense light pulses

The effect of antibrowning compounds on the color and firmness of fresh-cut avocado treated with intense light pulses (ILP), as well as their impact on the survival of Listeria innocua, was investigated in this study. Dipping solutions containing 2% (w/v) L-cysteine without ascorbic acid and combined with 1% (w/v) citric acid and 1% w/v calcium lactate most effectively preserved the initial color and texture of ILP-treated fresh-cut avocado. On the other hand, ILP treatments caused a reduction of more than 3 log cycles in the populations of L. innocua inoculated on fresh-cut avocado. Log reduction levels increased when antibrowning agents were combined with ILP treatments. In conclusion, the use of quality-stabilizing agents is a good option to guarantee both the microbiological safety of fresh-cut avocado treated with ILP as well as to improve its physical and chemical quality. PRACTICAL APPLICATION: Intense light pulses (ILP) have received considerable attention during the last years after its approval by the U.S. Food and Drug Administration (FDA) in 1996 as a decontamination method for food or food surfaces. This article presents relevant information regarding the effect of ILP treatments combined with quality-stabilizing compounds as a feasible alternative to improve the physical and chemical quality of fresh-cut avocado as well as to guarantee its microbiological safety.     

净菜商品化处理中品质变化及其控制的研究

净菜的生产和消费已成为现代社会发展的趋势,但其具有特殊的加工特点,品质维护难度很大,对净菜商品化处理过程中品质变化及其控制措施进行了论述。     

Plant metabolites and nutritional quality of vegetables

ABSTRACT:  Vegetables are an important part of the human diet and a major source of biologically active substances such as vitamins, dietary fiber, antioxidants, and cholesterol-lowering compounds. Despite a large amount of information on this topic, the nutritional quality of vegetables has not been defined. Historically, the value of many plant nutrients and health-promoting compounds was discovered by trial and error. By the turn of the century, the application of chromatography, mass spectrometry, infrared spectrometry, and nuclear magnetic resonance allowed quantitative and qualitative measurements of a large number of plant metabolites. Approximately 50000 metabolites have been elucidated in plants, and it is predicted that the final number will exceed 200000. Most of them have unknown function. Metabolites such as carbohydrates, organic and amino acids, vitamins, hormones, flavonoids, phenolics, and glucosinolates are essential for plant growth, development, stress adaptation, and defense. Besides the importance for the plant itself, such metabolites determine the nutritional quality of food, color, taste, smell, antioxidative, anticarcinogenic, antihypertension, anti-inflammatory, antimicrobial, immunostimulating, and cholesterol-lowering properties. This review is focused on major plant metabolites that characterize the nutritional quality of vegetables, and methods of their analysis.     

Nanoemulsion as advanced edible coatings to preserve the quality of fresh-cut fruits and vegetables: a review

The increasing consumer's demand regarding the healthy diet has promoted the research towards novel approaches for preserving minimally processed fruits and vegetables without the necessity of using preservatives. Emulsion-based edible coatings technology is considered a valuable alternative to improve fresh-cut fruit and vegetable quality. This review discusses some recent advances for the preservation of the quality and safety of fresh-cut fruits and vegetables with respect to the use of nanoemulsion-based edible coatings as carrier of functional compounds such as antimicrobial agents, antioxidants and texture enhancers. It focuses especially on the use of natural functional compounds in food preservation as an alternative to synthetic additives. Moreover, the preparation and characterisation of nanoemulsion are also reviewed.     

Alginate coating as carrier of oligofructose and inulin and to maintain the quality of fresh-cut apples

The aim of this study was to apply an edible coating containing prebiotics such as oligofructose and inulin to fresh-cut apple wedges. An assessment of the quality, sensory, polyphenol, and volatile attributes of coated and uncoated fresh-cut apple wedges was also undertaken. Fructan analysis showed that all prebiotics remained stable over the 14-d storage period and an intake of 100 g of apple supplies 1 to 3 g of prebiotics. Browning index, firmness, acidity remained stable throughout the 14 d compared to the control while applying prebiotic coatings resulted in an increase in soluble solids. Sensory and visual assessment indicated acceptable quality of apple wedges coated with prebiotics. HPLC analysis showed that levels of polyphenolic compounds were more stable in coated apple wedges (without prebiotic inclusions) than in uncoated control apples. No difference was found between O(2) and CO(2) headspace concentration of coated and uncoated samples. Significant differences (P < 0.001) were found for headspace volatile production between the samples. Most coated samples showed lower volatile production in the headspace than uncoated samples.     

Radiation processing of minimally processed sprouts (dew gram and chick pea): effect on sensory,nutritional and microbiological quality

Sprouts have become an important part of the diet because of their nutritive value and low‐calorie content. The effect of radiation processing (1 and 2 kGy dose) on minimally processed dew gram and chick pea sprouts with respect to different quality parameters was studied over a storage period of 16 days at 8 °C. Radiation treatment and storage period did not have any significant effect on the sensory as well as nutritional qualities of irradiated dew gram and chick pea sprout. No significant change (P > 0.05) was observed in the colour and firmness of irradiated sprouts as compared to control samples. However, radiation processing resulted in significant reduction in aerobic plate counts (APC), coliform counts (CC), yeast and mould count (YMC) and staphylococci counts (SC). Radiation processing of dew gram and chick pea sprouts at 1 and 2 kGy extends the shelf life without affecting sensory and nutritional qualities.     

鲜切果蔬病原微生物侵染及其生物控制的研究进展

病原微生物的侵染不但影响鲜切果蔬的质量安全,还会危害人类健康。本文概述了新型鲜活农产品-鲜切果蔬病原微生物的种类、污染源、感染率、生长特点及影响因素等研究进展,并介绍了这些病原微生物的生物控制的研究概况。      

Effect of ionizing radiation on furan formation in fresh-cut fruits and vegetables

ABSTRACT:  Furan, a possible carcinogen, is commonly induced by thermal processing in a wide variety of foods. The possible formation of furan from fresh-cut fruits and vegetables due to irradiation was studied. Nineteen fresh-cut fruits and vegetables were irradiated by 5 kGy gamma rays at 4 °C. Furan was analyzed from the irradiated samples using a number of preparation methods. The results showed that almost all tested fruits and vegetables, upon irradiation, produced nondetectable levels, or less than 1 ng/g of furan. Irradiation induced low ng/g levels of furan only in grape and pineapple. Dipping apple slices into calcium ascorbate before irradiation did not increase furan formation. The pH and the amount of simple sugars in fresh fruits and vegetables had a role in furan formation. Low levels of furan were induced by irradiation only in those fruits that had a high amount of simple sugars and low pH.     

Efficacy of different sanitizing agents and their combination on microbe population and quality of fresh-cut Chinese chives

The objective of this study was to evaluate the efficacy of individual sanitizing agents (sodium hypochlorite, SH; peracetic acid, PA; chlorine dioxide, CD) and the combination of CD and PA on reducing the total aerobic bacteria, coliforms as well as their effects on ascorbic acid (Vc), chlorophyll, and a* value of Chinese chives. All sanitizing treatments significantly (P < 0.05) reduced microorganisms compared to the control. After treatment with single SH, PA, and CD, the reduction of the total aerobic bacteria on Chinese chives was <1.0 log CFU/g (where colony-forming units is CFU), approximately 1.68 to 2.22 log CFU/g, and approximately 0.99 to 2.85 log CFU/g, respectively. The greatest reduction of total aerobic bacteria achieved by the combination of 40 ppm CD, 150 ppm PA for 8 min, was 2.45 log CFU/g. This treatment had a slight discoloration effect as indicated by a* value and chlorophyll content; and is therefore the optimal combination for reducing microorganisms on Chinese chives. PRACTICAL APPLICATION: Fresh-cut vegetables are known to be susceptible to contamination; and subsequent growth of microorganisms result in quality concerns. Chinese chive leaves are hollow, cylindrical, and are more inclined to accumulate microbes. Currently, there is limited information on the decontamination of Chinese chives. This research focused on the evaluation of sanitation options for fresh-cut Chinese chives; and the information obtained should be applicable and useful in other fresh-cut vegetables.     

Effect of UV‐C radiation on quality of minimally processed spinach leaves

BACKGROUND: The fresh‐cut vegetable industry commonly uses sodium hypochlorite (NaOCl) for disinfection. However, certain problems with NaOCl usage have led to the investigation of alternative sanitisation treatments. In this respect, UV‐C radiation could be of interest. RESULTS: The effect of four pre‐packaging UV‐C radiation doses (0, 4.54, 7.94 and 11.35 kJ m^?2) and two storage temperatures (5 and 8 °C) on the quality of minimally processed spinach (Spinacia oleracea L.) leaves was studied over a period of 13 days. UV‐C radiation decreased mesophilic and psychrophilic counts just after its application compared with conventional sanitisation washing (150 mg L^?1 NaOCl). However, UV‐C had no residual effect on microbial growth from 6 to 13 days at 5 and 8 °C. During shelf‐life a slight loss of lightness was found, probably related to superficial tissue damage induced particularly in higher‐UV‐C treated leaves. Total antioxidant activity and polyphenol content decreased gradually throughout storage, being more evident in higher‐UV‐C treated leaves stored at 8 °C. The general trend was to maintain the initial chlorophyll content during shelf‐life. CONCLUSION: Low to moderate UV‐C radiation can be an effective alternative to chlorine for sanitising minimally processed spinach leaves and preserving their quality. Copyright © 2008 Society of Chemical Industry     

植物精油的抑菌活性及在鲜切果蔬中的应用

鲜切果蔬由于具有营养、新鲜、方便等优点,受到越来越多消费者的喜爱。鲜切果蔬中致病菌和致腐菌是影响鲜切果蔬品质的重要因素,植物精油作为天然来源的抑菌物质,对鲜切果蔬产品具有防腐保鲜、维持品质等作用。本文介绍了植物精油的抑菌活性及作用机理,并综述植物精油对鲜切果蔬产品防腐、品质控制等方面的研究进展,同时对其在鲜切果蔬应用中存在的问题和应用前景进行了展望,为植物精油保鲜剂的开发提供了理论依据。      

Influence of commercial freezing and storage on vitamin C content of some vegetables

Vitamin C levels of commercially frozen okra, potatoes, green beans, broccoli, spinach and peas, including the impact of processing and storage, were studied. Depending on the vegetable type, prefreezing operations caused a 19.1–51.5% decrease in the initial vitamin C levels. The freezing process alone did not influence the vitamin levels except in the cases of green beans and spinach. Total losses (%) were between 27.6 and 57.9 for the vegetables at the end of commercial frozen storage (6 months). All the data obtained from this study confirmed that, depending on the vegetable type, prefreezing operations have a major impact on the vitamin C contents and this influence persists in the frozen storage.     

Biochemical changes of fresh-cut pineapple slices treated with antibrowning agents

The effectiveness of ascorbic acid (AA), isoascorbic acid (IAA) and N‐acetyl‐cysteine (AC) in inhibiting browning of fresh‐cut pineapple slices that were stored for up to 14 days at 10 °C, were studied. Slices treated with IAA and AA maintained higher levels of sugars and vitamin C than AC and controls. A low reduction of total phenolic content in treated slices was correlated with a lower polyphenol oxidase activity. IAA and AA slowed the degradation rates of sugars, vitamin C, and phenolic content, whereas AC was less effective in affecting these processes. A higher content of AA and IAA was associated with better compositional quality parameters and appearance of the pineapple slices during the storage period.     

不同贮藏方式对果蔬营养品质影响的研究进展

果蔬是人体获得维生素和矿物质等营养物质的主要来源,但是果蔬采后依然进行活跃的新陈代谢,导致营养物质的损失,其损失程度和速率主要受到果蔬不同贮藏方式的影响。本文阐述了不同贮藏方式对果蔬营养品质的影响及其研究进展,并从保持营养的角度对不同贮藏方式的应用前景进行了展望,以期为果蔬贮藏保鲜提供有价值的参考。