Effect of Surface Properties on Colloid Retention on Natural and Surrogate Produce Surfaces

Bacterial contamination of fresh produce is a growing concern in food industry. Pathogenic bacteria can attach to and colonize the surfaces of fresh produce and cause disease outbreaks among consumers. Surface properties of both bacteria and produce affect bacterial contamination; however, the effects of produce roughness, topography, and hydrophobicity on bacterial retention are still poorly understood. In this work, we used spherical polystyrene colloids as bacterial surrogates to investigate colloid retention on and removal (by rinsing) from fresh produce surfaces including tomato, orange, apple, lettuce, spinach, and cantaloupe, and from surrogate produce surface Sharklet (a micro‐patterned polymer). All investigated surfaces were characterized in terms of surface roughness and hydrophobicity (including contact angle and water retention area measurements). The results showed that there was no single parameter that dominated colloid retention on fresh produce, yet strong connection was found between colloid retention and water retention and distribution on all the surfaces investigated except apple. Rinsing was generally not efficient in removing colloids from produce surfaces, which suggests the need to modify current cleaning procedures and to develop novel contamination prevention strategies. This work offers a physicochemical approach to a food safety problem and improves understanding of mechanisms leading to produce contamination.     

On the epidemic of food waste: Idealized prototypes and the aversion to misshapen fruits and vegetables

Food waste is a significant problem and consumers’ tendency to reject misshapen produce has been identified as a key contributing factor. The current work investigates the implications of consumers incorporating aesthetic beauty into their prototypes—mental renderings—of fruits and vegetables. It is proposed that consumers have idealized prototypes for produce and this impacts the aversion to misshapen produce. The authors draw on prototype theory to predict that consumers’ personal experiences will influence the extent to which their prototypes for these foods have been biased towards aesthetic beauty and, consequently, how they respond to produce that is misshapen. Across three studies, the authors demonstrate that consumers who have direct experience with produce cultivation view produce that is low in aesthetic beauty as more prototypical, less disgusting, and more desirable. This work contributes to the food waste literature by offering novel insights into the psychological basis of the aversion to misshapen produce. These findings also present important implications for food policy.     

Factors affecting quality and safety of fresh-cut produce

The quality of fresh-cut fruit and vegetable products includes a combination of attributes, such as appearance, texture, and flavor, as well as nutritional and safety aspects that determine their value to the consumer. Nutritionally, fruit and vegetables represent a good source of vitamins, minerals, and dietary fiber, and fresh-cut produce satisfies consumer demand for freshly prepared, convenient, healthy food. However, fresh-cut produce deteriorates faster than corresponding intact produce, as a result of damage caused by minimal processing, which accelerates many physiological changes that lead to a reduction in produce quality and shelf-life. The symptoms of produce deterioration include discoloration, increased oxidative browning at cut surfaces, flaccidity as a result of loss of water, and decreased nutritional value. Damaged plant tissues also represent a better substrate for growth of microorganisms, including spoilage microorganisms and foodborne pathogens. The risk of pathogen contamination and growth is one of the main safety concerns associated with fresh-cut produce, as highlighted by the increasing number of produce-linked foodborne outbreaks in recent years. The pathogens of major concern in fresh-cut produce are Listeria monocytogenes, pathogenic Escherichia coli mainly O157:H7, and Salmonella spp. This article describes the quality of fresh-cut produce, factors affecting quality, and various techniques for evaluating quality. In addition, the microbiological safety of fresh-cut produce and factors affecting pathogen survival and growth on fresh-cut produce are discussed in detail.     

Process engineering variables in the spray washing of meat and produce.

Recently, much attention has been focused on the safety of fruits and vegetables. Washing is a fundamental operation in the processing of produce. Aqueous spray energy can be, and often is, used to remove mineral, chemical, or biological contaminants from produce. A few advantages of spray washing over washing by dipping, soaking, or gravity rinse are increased energy directed to contaminants, reduced volume of water use and wastewater generation, and reduced water uptake by produce. The kinetic energy of the spray droplets produces the cleaning action. Increased spray pressure increases energy. If the energy is too great, produce may be physically damaged. If the energy is too little, the surface may not be cleaned. Indeed, studies on meat have shown that water pressures ranging from 1,379 to 2,070 kPa (200 to 300 psi) are effective in reducing microbial contamination, and a water flow rate of 7.5 liters/min is recommended. Water temperature >70 degrees C has been found to reduce bacterial counts in carcass tissue by 2 to 3 log CFU/cm2. These levels are likely too high for the fragile produce; hence, the main function of spray washing in produce applications will probably shift to being a delivery system for antimicrobial agents. Several other equipment, process, and product variables are relevant to the optimization of such a system. Qualities of the spray, such as droplet spectrum, droplet velocity, angle of droplet impingement, number and orientation of nozzles, spray rate, and resident time of the produce in the sprayer, also can be manipulated to adjust the amount of energy directed to the surface. There is a need to scientifically investigate the effects of these processes and equipment parameters on the removal of microbiological contaminants on meats and produce. Such empirical investigations guided by the results from fundamental studies about produce surface characteristics and the mechanism of bacterial attachment to plant tissue surfaces would allow for the efficient development of spray washers that effectively decontaminate produce.     

Combined effect of calcium oxide and sonication to reduce foodborne pathogens on fresh produce

This study was conducted to investigate the antibacterial activity of calcium oxide (CaO), sonication, and their combination against foodborne pathogens on several fresh produce. The results showed that combined treatment inhibited Escherichia coli O157:H7, Listeria monocytogenes, and Salmonella Typhimurium on fresh produce. However, the effectiveness of treatments for reducing populations of foodborne pathogens varied depending on the types and condition of the fresh produce. This study demonstrated that the antibacterial potency of CaO and its application with sonication could be one of alternatives for controlling foodborne pathogens on fresh produce.     

Chlorine disinfection of produce to inactivate hepatitis A virus and coliphage MS2

Disinfection of produce is principally used to inactivate spoilage microbes and may also reduce the risk of consumer exposure to enteric pathogens. However, the rate and extent of enteric virus inactivation by free chlorine on produce has not been adequately characterized. Experiments were performed to determine the kinetics of free chlorine inactivation of hepatitis A virus (HAV) and the indicator virus coliphage MS2 on strawberries (SBs), cherry tomatoes (CTs), and head lettuce (HL). The oxidant demand of these produce items also was determined. When produce items were exposed to approximately 20 parts per million (ppm) solution of free chlorine for 5-10 min, HAV and MS2 were inactivated by 90-99% and in some cases virus inactivation was >/=99%. Exposure of strawberries to approximately 200 ppm free chlorine resulted in more rapid and extensive inactivation of both viruses. The produce items tested in this study exhibited a demand for chlorine which varied by produce type, and chlorine residuals declined over time. These results demonstrate the potential for chlorine to reduce the levels of infectious viruses on different produce types, but adequate contact time and chlorine residual are required to achieve maximum virus inactivation. The difference in chlorine demand between SBs, CTs, and HL suggests that varying disinfection practices are needed for the wide variety of processed fruits and vegetables. The inactivation kinetics of MS2 and HAV were similar, suggesting that MS2 and perhaps other similar bacterial viruses may be used as process indicators and surrogates for determining the disinfection efficacy of produce in the laboratory or in actual practice.     

废蜜的化学组成与生物制氢

利用甜菜制糖废蜜、废水作为底物进行连续流生物制氢，既可回收废物又能生产能源。着重阐述了甜菜废蜜中的主要成分及其在生物制氢反应中对微生物的作用。     

Influence of Heat Treatments on Quality Retention of Fresh and Fresh-Cut Produce

Postharvest decay and insect infestation are two major causes that contribute towards higher postharvest losses during the fresh produce supply chain. Although decay and pest infestation could be controlled successfully via pesticide applications, the use of chemicals at the postharvest stage is becoming limited due to the strict regulations regarding pesticide residue levels enforced by importing countries. Heat treatments are environmentally friendly and recommended as alternative treatments to replace pesticide applications, especially with regard to fresh produce. These treatments help to eradicate pathogens or pests that are present on the fruit surface while maintaining the overall quality of the fresh produce during the supply chain. Browning is regarded as an economically important physiological disorder that causes detrimental effects on the quality maintenance of fresh-cut produce. Contamination of fresh produce by foodborne pathogens could occur at any stage during the production, harvesting, postharvest chain, or processing, and heat treatments could be recommended as an antibrowning or disinfection treatment for the fresh-cut industry. In light of the above, this review summarizes the effects of postharvest heat treatments on postharvest decay, insect infestation, physiological disorders, fruit ripening, retention of color, and bioactive compounds.     

Minimal nitrogen and water use in horticulture: Effects on quality and content of selected nutrients

Horticultural production has primarily focused on increasing productivity through intensification of fertilizers and water, resulting in high environmental costs. Recent research indicates that high nitrogen applications can have significantly negative effects on produce quality as well as secondary plant metabolite and vitamin content within fruits and vegetables. Consumer awareness of both sustainable production practices and nutritional content within fruits and vegetables has risen dramatically in recent years, indicating that there is a likely market for produce grown with minimal nitrogen and water inputs. This review investigates the effects on produce quality of nitrogen and water applications in fruit and vegetable crops, with specific emphasis on the content of flavonoids, carotenoids, glucosinolates and ascorbic acid. The link between the nutritional quality of horticultural crops and the environmental and social sustainability of reducing nitrogen and water is considered and discussed.     

水溶性PVA纤维在产品设计开发上的应用

文章在分析水溶性PVA纤维性能特点基础上,探讨其在纱线和织物设计开发上的应用,利用PVA纤维与其它短纤混纺生产出各种细特纱,同时利用纯PVA纤维纱还可开发具有横条或纵条镂空等特殊效果的织物.文章以提花兔毛大衣呢织物的设计开发为例,在织物规格设计中应用PVA纤维纱,解决了生产上工艺和设备条件的限制等难题,开发出具有特殊效应的提花兔毛大衣呢,为产品设计提供了一条有效的途径.     

Microbial Risks Associated with Cabbage,Carrots, Celery,Onions, and Deli Salads Made with These Produce Items

Abstract: The microbiological safety of cabbage, carrots, celery, and onions/scallions as well as deli (mayonnaise‐based) salads that contain these items is the subject of this review. Between 2000 and 2007, the number of outbreaks in the United States associated with these raw produce items ranged from 6 (celery) to 18 (carrots). For cases with confirmed etiologies involving these 4 types of produce as well as coleslaw, chicken, seafood, and other vegetable‐based salads, more than 50% of the outbreaks were attributed to viral agents. In contrast, Salmonella spp. served as the major etiological agent in outbreaks associated with potato salad. Surveys conducted on these produce items within the United States and other developed countries found either an absence or infrequent contamination with foodborne pathogens. Despite this low prevalence, experimental studies have demonstrated the potential for preharvest contamination, and this event is more likely to occur when exposure is close to harvest. Postharvest contamination of these produce items has been documented in several cases with water, equipment, and incoming product serving as the principal cross‐contamination agent. Survival of contaminated product during subsequent storage is dependent on the storage temperature, produce type, and presence of mayonnaise. Chemical interventions may be relied on to reduce cross‐contamination during produce washing operations but are limited in their ability to inactivate pathogens on the produce surface. In contrast, irradiation at dosages (1.0 kGy) approved for use in the United States is an effective treatment for killing pathogenic bacteria in fresh‐cut cabbage, carrots, and celery.     

Dietitians' attitudes, perceptions, and usage patterns for fresh-cut fruit and vegetables.

PURPOSE: New fresh-cut fruit and vegetable products are being developed worldwide. Nutrition educators' perceptions of these products were studied. METHODS: Professional dietitians in Nova Scotia were asked to complete a questionnaire on their use of fresh-cut produce. The questionnaire also elicited their attitudes and perceptions about the convenience, taste/quality, nutrition/health benefits, cost, and safety of fresh-cut fruit and vegetables. RESULTS: Sixty-three percent of respondents reported eating five to six servings of fruit and vegetables a day. This group most frequently consumed fresh-cut fruit as snacks or dessert, and vegetables in stir-fry dishes or salads or cooked with meals. In general, fresh-cut fruit and vegetables were perceived as convenient, safe, and nutritious. While approximately 50% of participants felt fresh-cut produce did not differ in taste from whole fresh produce, almost the same number considered whole fresh produce superior in taste. CONCLUSIONS: Dietitians have a generally positive perception of fresh-cut products; however, there is uncertainty about the nutritional value, cost/benefit, and use of the products. Dietitians require more information on the nutrient value of these products and on suggested alternative uses. Attention should be paid to developing fresh-cut products that have good sensory quality.     

Most Common Foodborne Pathogens and Mycotoxins on Fresh Produce: A Review of Recent Outbreaks

Every year millions of people are affected and thousands of them die due to infections and intoxication as a result of foodborne outbreaks, which also cause billions of dollars' worth of damage, public health problems, and agricultural product loss. A considerable portion of these outbreaks is related to fresh produce and caused by foodborne pathogens on fresh produce and mycotoxins. Escherichia coli O104:H4 outbreak, occurred in Germany in 2011, has attracted a great attention on foodborne outbreaks caused by contaminated fresh produce, and especially the vulnerability and gaps in the early warning and notification networks in the surveillance systems in all around the world. In the frame of this paper, we reviewed the most common foodborne pathogens on fresh produce, traceback investigations of the outbreaks caused by these pathogens, and lastly international early warning and notification systems, including PulseNet International and Rapid Alert System for Food and Feed, aiming to detect foodborne outbreaks.     

甘蔗糖蜜酒精废液综合利用的探索与实践

用板式降膜蒸发器蒸发浓缩酒精废液的方法，经生产实践证明，已取得初步成功，本文着得成功了采用该方法生产浓缩液的主要工艺与设备，用浓缩液生产基质肥的方法。     

Production of biofilm and quorum sensing by Escherichia coli O157:H7 and its transfer from contact surfaces to meat,poultry, ready-to-eat deli,and produce products

Multistate outbreaks of Escherichia coli O157:H7 infections through consumption of contaminated foods including produce products have brought a great safety concern. The objectives of this study were to determine the effect of biofilm and quorum sensing production on the attachment of E. coli O157:H7 on food contact surfaces and to evaluate the transfer of the pathogen from the food contact to various food products. E. coli O157:H7 produced maximum levels of AI-2 signals in 12 h of incubation in tested meat, poultry, and produce broths and subsequently formed strong biofilm in 24 h of incubation. In general, E. coli O157:H7 formed stronger biofilm on stainless steel than glass. Furthermore, E. coli O157:H7 that had attached on the surface of stainless steel was able to transfer to meat, poultry, ready-to-eat deli, and produce products. Strong attachment of the transferred pathogen on produce products (cantaloupe, lettuce, carrot, and spinach) was detected (>10³ CFU/cm²) even after washing these products with water. Our findings suggest that biofilm formation by E. coli O157:H7 on food contact surfaces can be a concern for efficient control of the pathogen particularly in produce products that require no heating or cooking prior to consumption.     

The Use of Controlled Postharvest Abiotic Stresses as a Tool for Enhancing the Nutraceutical Content and Adding-Value of Fresh Fruits and Vegetables

This paper proposes a concept based on applying postharvest abiotic stresses to enhance the nutraceutical content of fresh fruits and vegetables. We hypothesize that selected abiotic stress treatments, such as wounding, phytohormones, temperature, ultraviolet light, altered gas composition, heat shock, and water stress, among others, will affect the secondary metabolism of fresh produce and increase the synthesis of phytochemicals with nutraceutical activity or reduce the synthesis of undesirable compounds. Controlled stresses may be used as tools by the fresh produce industry to enhance the health benefit properties of fresh‐cut or whole fresh produce and by the food processing and dietary supplement industries to obtain healthier processed products or enhance extractable nutraceutical yields.     

Quality of fresh‐cut products as affected by harvest and postharvest operations

There is a rising demand for fresh‐cut convenience products with high quality and nutritional standards that needs to be met by the fresh‐cut industry. It is well known that harvest and postharvest handling of fresh produce has a paramount impact on its quality and storage, although most of the existing literature has focused on these impacts related only to fresh produce that is destined for the final consumers. Indeed, current harvest methods and postharvest technologies have improved fruit and vegetable handling and distribution processes by slowing down physiological processes and senescence. Nonetheless, these technologies and methods may influence the quality of fresh produce as raw material for fresh‐cut processing as a result of the dynamic responses of fresh produce to handling procedures and treatments. Here, we review the existing literature on the challenges facing the fresh‐cut industry, focusing on the impact of harvest, maturity, and handling of fruit and vegetables on the quality of raw materials, as well as the implications for fresh‐cut products. The review also highlights areas for further research with the aim of enhancing the sensorial, nutritional and biochemical quality of such products. © 2018 Society of Chemical Industry     

A field study of the microbiological quality of fresh produce of domestic and Mexican origin

Produce is responsible for an increasingly larger proportion of foodborne disease outbreaks. In particular, the globalization of the food supply may introduce new food safety risks and allow widespread distribution of contaminated food, particularly produce. The objectives of this study were to: (i) compare the overall quality of domestic and Mexican produce throughout the packing process; (ii) examine changes in microbiological quality of both domestic and Mexican produce at each stage of production and processing; and (iii) evaluate the prevalence of select pathogens on fresh produce, including leafy green, herbs, melons, and vegetables. Furthermore, we also sought to characterize the antibiotic resistance profiles of Enterococcus faecium and Enterococcus faecalis strains isolated from fresh produce. A total of 466 produce and matching environmental swab samples was collected from various locations in packing sheds in the southern US from November 2002 through December 2003. These samples were assayed by enumerative tests for total aerobic bacteria (APC), total coliforms, total Enterococcus, and E. coli. Produce samples were also analyzed for the presence of Salmonella, Listeria monocytogenes, Shigella, and E. coli O157:H7. A total of 112 E. faecium and E. faecalis isolates were further screened for antibiotic resistance using a panel of seventeen antibiotics. Overall, the microbiological quality of fresh produce ranged from 4.0 to 7.9 log(10) CFU/g (APC); less than 1.0 log(10) to 4.5 log(10) CFU/g (coliforms); less than 1.0 log(10) to 4.0 log(10) CFU/g (E. coli); and less than 1.0 log(10) to 5.4 log(10) CFU/g (Enterococcus). No Salmonella, Shigella, or E. coli O157:H7 were detected from the 466 25-g produce samples tested. However, three domestic cabbage samples were found to be positive for L. monocytogenes. Of the Enterococcus isolates, E. faecium had a higher degree of resistance to antibiotics in general, while Enterococcus spp. isolated from Mexican produce had a higher degree of antibiotic resistance when compared to strains isolated from produce samples of domestic origin. Despite increased attention to the role of imported produce in foodborne disease, this study does not support the assumption that domestic produce is of higher microbial quality than Mexican produce.     

Comparison of sample preparation methods for recovering Salmonella from raw fruits, vegetables, and herbs

Methods for preparing raw fruits, vegetables, and herbs for enrichment or direct plating to determine the presence and populations of pathogenic bacteria vary greatly. A study was done to compare three sample processing methods (washing in 0.1% peptone, stomaching, and homogenizing) for their influence on recovery of Salmonella inoculated onto 26 types of raw produce. The mean numbers of Salmonella recovered from 10 fruits, 11 vegetables, and 5 herbs using all three processing methods were 7.17, 7.40, and 7.27 log10 CFU/sample, respectively. Considering all 26 types of produce and all processing methods, the number of Salmonella recovered ranged from 7.24 to 7.29 log10 CFU/sample, with no significant differences attributable to a particular sample processing method. Mean percent recoveries of Salmonella from washed, stomached, and homogenized produce were 39.4, 44.7, and 42.4%, respectively. Mean percent recoveries from fruits, vegetables, and herbs, regardless of sample preparation method, were 41.7, 50.1, and 25.9%, respectively. The number of Salmonella recovered from stomached and homogenized produce, but not washed produce, with pH < or = 4.53 was significantly less than the number recovered from produce with pH from 5.53 to 5.99, suggesting that the acidic environment in stomachates and homogenates was lethal to a portion of Salmonella. Reduced percent recoveries from herbs (pH 5.94 to 6.34) is attributed, in part, to antimicrobials released from plant cells during sample preparation. Overall, the type of processing method did not substantially affect the number of Salmonella recovered from the 26 types of raw produce representing a wide range of structural and morphological characteristics, composition, and pH. The influence of sample size, diluent composition, and processing time on efficiency of recovery of Salmonella and other pathogens needs to be evaluated before a method(s) for processing samples of raw produce can be recommended.     

Consumer sensory analysis of organically and conventionally grown vegetables

ABSTRACT:  Consumers of organically grown fruits and vegetables often believe that these products taste better than conventional produce. However, comparison of produce from supermarket shelves does not permit adequate assessment of this consumer perception, given potentially confounding cultivar and environmental effects. We used replicated side-by-side plots to produce organic and conventional vegetables for consumer sensory studies. In one test, red loose leaf lettuce, spinach, arugula, and mustard greens, grown organically and conventionally, were evaluated for overall liking as well as for intensity of flavor and bitterness. Another consumer test was conducted comparing organically and conventionally grown tomatoes, cucumbers, and onions. Overall, organically and conventionally grown vegetables did not show significant differences in consumer liking or consumer-perceived sensory quality. The only exception was in tomatoes where the conventionally produced tomato was rated as having significantly stronger flavor than the organically produced tomato. However, overall liking was the same for both organic and conventional samples. As conventional tomatoes also were scored marginally significantly higher in ripeness and a positive correlation was found between ratings of flavor intensity and ripeness, the flavor difference observed could not be simply ascribed to the contrasting growing conditions. Consumer panelists in both tests considered organic produce to be healthier (72%) and more environmentally friendly (51%) than conventional produce, while 28% considered organic produce to have better taste. Covariance analysis indicated that consumer demographics affected sensory comparisons of organic and conventional lettuce and cucumbers. Future study is needed to substantiate the influence of segmentation of consumers on their preference for organic food.