Microbiological quality of fresh, minimally-processed fruit and vegetables, and sprouts from retail establishments

A survey of fresh and minimally-processed fruit and vegetables, and sprouts was conducted in several retail establishments in the Lleida area (Catalonia, Spain) during 2005-2006 to determine whether microbial contamination, and in particular potentially pathogenic bacteria, was present under these commodities. A total of 300 samples--including 21 ready-to-eat fruits, 28 whole fresh vegetables, 15 sprout samples and 237 ready-to-eat salads containing from one to six vegetables--were purchased from 4 supermarkets. They were tested for mesophilic and psychrotrophic aerobic counts, yeasts and moulds, lactic acid bacteria, Enterobacteriaceae, presumptive E. coli and Listeria monocytogenes counts as well as for the presence of Salmonella, E. coli O157:H7, Yersinia enterocolitica and thermotolerant Campylobacter. Results for the fresh-cut vegetables that we analyzed showed that, in general, the highest microorganism counts were associated with grated carrot, arugula and spinach (7.8, 7.5 and 7.4 log cfu g(-1) of aerobic mesophilic microorganisms; 6.1, 5.8 and 5.2 log cfu g(-1) of yeast and moulds; 5.9, 4.0 and 5.1 log cfu g(-1) lactic acid bacteria and 6.2, 5.3 and 6.0 log cfu g(-1) of Enterobacteriaceae). The lowest counts were generally associated with fresh-cut endive and lettuce (6.2 and 6.3 log cfu g(-1) of aerobic mesophilic microorganisms; 4.4 and 4.6 log cfu g(-1) of yeast and moulds; 2.7 and 3.8 log cfu g(-1) lactic acid bacteria and 4.8 and 4.4 log cfu g(-1) of Enterobacteriaceae). Counts of psychrotrophic microorganisms were as high as those of mesophilic microorganisms. Microbiological counts for fresh-cut fruit were very low. Sprouts were highly contaminated with mesophilic (7.9 log cfu g(-1)), psychrotrophic microorganisms (7.3 log cfu g(-1)) and Enterobacteriaceae (7.2 log cfu g(-1)) and showed a high incidence of E. coli (40% of samples). Of the samples analyzed, four (1.3%) were Salmonella positive and two (0.7%) harboured L. monocytogenes. None of the samples was positive for E. coli O157:H7, pathogenic Y. enterocolitica or thermotolerant Campylobacter.     

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。     

智能传感技术及在新鲜果蔬品质检测中的应用

人的感官评定和理化性质检测是评价食品品质的传统方法,存在评价标准具有主观干扰、误差较大及工作效率低等缺点。人们期望机器可以承担需要人类智能才能完成的工作,在此背景下,智能传感技术应运而生。文中综述了智能传感技术的种类、在果蔬品质检测中的研究进展及其应用,并展望了智能传感技术的应用前景。     

超市生鲜蔬菜供应链特征及损耗控制

对目前超市生鲜蔬菜经营方式、供应途径及损耗原因的研究分析表明,超市蔬菜供应分为普通蔬菜供应链和无公害/有机蔬菜供应链两种模式。超市蔬菜的损耗主要分为由于生理、环境和微生物引起蔬菜新鲜度下降和腐烂变质所导致的自然损耗,以及由于员工操作和消费者挑选造成蔬菜损伤所导致的人为损耗,消费者挑选是人为损耗的主要原因。将食品科学与管理技术相结合,提出冷链保鲜和分类处理等措施可以降低自然损耗,有效的运营管理可以降低人为损耗。     

采后硅酸钠处理对杏果黑斑病的控制及品质的影响

研究了采后硅酸钠处理对杏果黑斑病的控制及品质的影响。结果表明:体外条件下不同浓度硅酸钠对黑斑病病原物Alternaria alternata的生长具有显著的抑制作用,其中以25mmol/L处理效果最好,抑菌率可达72.73%。50mmol/L硅酸钠浸泡可明显降低杏果损伤接种A.alternata的病斑直径,处理组病斑直径低于对照22%,且抑制效果可持续96h。50mmol/L硅酸钠处理还有效延缓了常温贮藏初期果实硬度的下降,维持了较高的可滴定酸和VC的含量,但对可溶性固形物含量无明显影响。由此表明,采后硅酸钠处理可通过直接抑菌和诱导果实抗性来控制杏果黑斑病,并在一定程度上维持果实的品质。     

加工前轻微热处理对鲜切砀山梨品质的影响

对贮后砀山梨进行轻微热处理,采用35、40和45℃热水中分别浸泡40、90和140min的9个处理条件,冷却风干,而后在2℃条件下冷藏24h,用锋利的刀去皮、去核,切分成1/4小瓣,于2℃条件下冷藏。对鲜切梨的品质进行测定,结果表明,40℃-90min和40℃-140min处理组对于抑制切面褐变和维持或增加鲜切砀山梨的硬度是很有效的,失重率、可溶性固形物含量和可滴定酸含量不存在显著性差异(P≤0.05)。因而40℃-90min和40℃-140min的热水浸泡是适合于鲜切砀山梨的轻微热处理条件。     

Effects of water stress on the post-harvest quality of two leafy vegetables,telfairia occidentalis and pterocarpus soyauxii during storage

The effect of water stress (excessive water loss) on the post-harvest quality of two leafy vegetables, Telfairia occidentalis and Pterocarpus soyauxii, at ambient (30–35°C) and low temperature (10°C) was investigated in south-eastern Nigeria. The effect of seal-packaging the vegetables in polyethylene and paper bags on quality decline of the leafy vegetables was also monitored. Unsealed leaves of T occidentalis and P soyauxii rapidly lost water during storage at either ambient or low temperature. There were decreases in the chlorophyll, protein and ascorbic acid contents in the stressed leaves. Packaging of the leaves in polyethylene bags alleviated these losses. Sealing of the leaves in polyethylene bags also alleviated water stress.     

Pesticide residues and estrogenic activity in fruit and vegetables sampled from major fresh produce markets in South Africa

Food is likely to be one of the major pathways through which people are exposed to endocrine-disrupting chemicals. With the exception of residual effects, there are concerns that a number of naturally occurring and synthetic chemicals exert adverse effects upon endocrine systems in wildlife and humans. The current study reports selected pesticide concentrations and the total estrogenic activity of fruit and vegetables using the recombinant yeast oestrogen screen (YES) and T47D-KBluc reporter gene assays. A total of 53 food samples (27 fruit and 26 vegetables) from Johannesburg and Tshwane fresh produce markets (in South Africa) were analysed. Of these, 17 contained one to three different pesticide residues with concentrations ranging between 0.01 and 0.68 mg kg^–1, whereas in the rest of the samples no residues were detected. All pesticides detected except in one sample were below the maximum residue level (MRL), but others were unauthorised for use in specified fruit and vegetables. Estrogenic activity was detected in 26.4% (14 samples) of the samples tested, and the estradiol equivalents ranged from 0.007 to 2 pg g^–1. Although the estrogenic activity was low, it may contribute to adverse health effects. Continuous monitoring for pesticides in fruit and vegetables is important in view of the unauthorised pesticides detected in produce from South Africa and the endocrine-disrupting chemical activity found.     

Contents of polyphenols in fruit and vegetables

The work is an attempt at a model presentation, using a new multi-criteria mathematical method called the analytical hierarchy process, of polyphenol supply to human organisms from fruit and vegetables. On this basis, plant raw materials which supply polyphenols to the organism to the greatest extent and thus contribute to an improvement in health state of people in Poland were identified.     

Analysis of the changes in quality in mandarin fruit,produced by deficit irrigation treatments

‘Clemenules’ mandarin citrus trees, grafted on Cleopatra and Carrizo rootstocks, were subjected to three irrigation treatments: the control (100% ETc), and phases II and III treatments (non-irrigation during phases II and III, respectively). The two deficit irrigation (DI) treatments affected in different ways some fruit quality parameters and these effects were also dependent on the rootstock. Although phase II treatment increased total soluble solids (TSS) and titratable acidity (TA), it delayed the maturation process. Phase II-stressed fruits on Carrizo had more fructose and glucose but less sucrose in relation to control fruits, thus increasing the reducing sugars. Phase II-stressed fruits on Cleopatra had more glucose, fructose and sucrose, for osmotic adjustment, also increasing the reducing sugars in these fruits. Phase III-stressed fruits had greater acidity, TSS, total phenolics, lycopene, glucose and sucrose than control fruits, but the same maturation state. In conclusion, DI in phase III improved fruit quality, by increasing the values of important quality parameters related to taste, flavour and nutritional benefits, but DI in phase II produced a drastic delay in the maturation process that made fruits non-commercial.     

拮抗酵母菌对果蔬采后病害生物防治的研究进展

简述了用于果蔬采后拮抗酵母菌的种类和特点、拮抗效果、拮抗机制,以及目前我国拮抗酵母菌应用中存在的问题、发展前景及未来研究方向.     

肠炎沙门氏菌在鲜切果蔬中的动态生长变化

研究了肠炎沙门氏菌(Salmonella enterica serovar Enteritidis,SE)在4、10、15、30℃的鲜切苹果、卷心菜、生菜中7d内的动态生长变化,验证ComBase数据库中的生长预测模型GP(Growth Predictor)的预测准确性。研究结果表明,SE在4℃的3种鲜切果蔬中生长受到抑制,但能存活。不同温度下,生长到最大菌落数的时间有一定差异,温度越高,所花时间越短。对比GP的预测值,SE在鲜切果蔬中生长的最大菌落数均不能达到GP的预测值。在10℃下,GP预测的SE在鲜切果蔬中的生长比实际生长速度慢,这在安全风险评估时并不可靠。     

Chemical and physical changes in the pulp during ripening and post-harvest storage of cocoa pods

Changes in the pulp during ripening and post-harvest storage of cocoa pods were determined during numerous harvests in Malaysia (1984 to 1987) and Ghana (1985 to 1986), in order to gain a basis for understanding the influence of ripening and storage on acid formation during subsequent fermentation. Changes in the pulp during ripening of fully grown pods were the same but less pronounced than those during dry storage of harvested pods: the percentage of water in the pulp was not changed significantly, but the amount of water and of dry matter per seed was strongly reduced (by 40–50%) due to water evaporation and respiration of sugars. Sucrose was inverted completely. The result of these changes was an equally strong reduction of the pulp volume per seed and increase of the pulp surface to pulp volume ratio. The reduction of acid formation during fermentation with beans from stored pods is ascribed predominantly to these changes rather than to the reduction in the amount of sugars, and is explained not only by the facilitated mass aeration but, above all, by the significant increase in respiration at the pulp surface over ethanol fermentation in the pulp when the pulp volume is reduced prior to fermentation. Ghanaian pods at similar stages of ripeness revealed more advanced stages of the pulp compared with Malaysian pods and consequently less significant change during storage. Water evaporation and respiration during pod storage were significantly higher in the pulp than in the husk.     

可食性膜在果蔬贮藏保鲜中的应用

主要介绍可食性膜的概念、特点、类型及其在果蔬保鲜中的应用。     

Influence of physical and biological variability and solution methods in fruit and vegetable quality nondestructive inspection by using imaging and near-infrared spectroscopy techniques: A review

Over the past decades, imaging and spectroscopy techniques have been rapidly developing and widely applied in nondestructive fruit and vegetable quality assessment. The physical properties (including size, shape, color, position, and temperature) and biological properties (including cultivar, season, maturity level and geographical origin) of fruits and vegetables vary from one to another. A great variety of physical and biological properties of agricultural products influence the optical propagation properties and interaction behaviors with incident light, thus decreasing the quality inspection accuracy. Many attempts have been made in image correction and spectral compensation methods to improve the inspection accuracy. This paper gives a detailed summary about influence of physical and biological variability, as well as the correction and compensation methods for eliminating or reducing the effects in fruit and vegetable quality nondestructive inspection by using imaging and spectroscopy techniques. The advantages and disadvantages of the solution methods are discussed and summarized. Additionally, the future challenges and potential trends are also reported.     

中国果蔬产业发展状况与预测

通过对中国果蔬产业近20年来的产量增长，品种分布，贮运加工技术的状况分析，预测中国果蔬产业的发展趋势和发展前景。     

化学物质对鲜切茭白品质及生理的影响

研究了化学物质单独或复合处理对鲜切茭白品质及生理的影响。结果显示,4-己基间苯二酚（4-HR）、氯化钙（CC）、抗坏血酸（AA）、N-乙酰-L-半胱氨酸（N-AC）和复合处理均显著抑制了鲜切茭白的褐变;贮藏15d后失重率分别为对照的95.6%、75.3%、74.5%、76.5%和57.9%;硬度分别为入贮时的66.1%、91.0%、80.4%、74.6%和86.7%,对照仅为63.6%;抗坏血酸保留率分别为70.5%、75.1%、89.2%、83.3%和82.6%,对照仅保留57.5%;还原糖含量维持在相对高的水平,呼吸速率、及O-2·产生速率和MDA含量维持在相对低的水平;PPO活力显著低于对照;POD活力分别为入贮时的3.07、1.95、1.73、2.01、1.35倍。以上结果表明,实验所选化学物质均能有效延缓鲜切茭白褐变和生理代谢,提高活性氧自由基清除能力,最终维持鲜切茭白较好的品质。由于复合处理表现出最好的效果,提示复合处理可用于商业上控制鲜切茭白褐变和维持其品质。     

贮藏温度对鲜切杏鲍菇呼吸强度和贮藏品质的影响

以鲜切杏鲍菇为试材,在不同贮藏温度(0、5、10℃和室温)下,通过测定呼吸强度、失重率、PPO活性、相对电导率、颜色L*含量变化,并结合感官变化研究了不同温度对鲜切杏鲍菇保鲜效果的影响。结果表明:低温0℃延迟了鲜切杏鲍菇的多酚氧化酶活性高峰的产生,抑制了相对电导率和失重率的升高,可以有效降低菇片的变色、腐烂及褐变,保持杏鲍菇的新鲜品质,延长货架期。     

Nonthermal physical technologies to decontaminate and extend the shelf-life of fruits and vegetables: Trends aiming at quality and safety

Minimally processed fruits and vegetables are one of the major growing sectors in food industry. This growing demand for healthy and convenient foods with fresh-like properties is accompanied by concerns surrounding efficacy of the available sanitizing methods to appropriately deal with food-borne diseases. In fact, chemical sanitizers do not provide an efficient microbial reduction, besides being perceived negatively by the consumers, dangerous for human health, and harmful to the environment, and the conventional thermal treatments may negatively affect physical, nutritional, or bioactive properties of these perishable foods. For these reasons, the industry is investigating alternative nonthermal physical technologies, namely innovative packaging systems, ionizing and ultraviolet radiation, pulsed light, high-power ultrasound, cold plasma, high hydrostatic pressure, and dense phase carbon dioxide, as well as possible combinations between them or with other preservation factors (hurdles). This review discusses the potential of these novel or emerging technologies for decontamination and shelf-life extension of fresh and minimally processed fruits and vegetables. Advantages, limitations, and challenges related to its use in this sector are also highlighted.