The efficacy of electrolysed oxidising water for inactivating spoilage microorganisms in process water and on minimally processed vegetables

The efficacy of Electrolysed Oxidising Water (EOW) for inactivating spoilage microorganisms in process water and on minimally processed vegetables was investigated. The direct effect of EOW on three important spoilage bacteria namely; Pseudomonas fluorescens, Pantoea agglomerans or Rahnella aquatilis was determined by inoculating tap water or "artificial process water" with approximately 8 log CFU/ml pure culture and electrolysing the resultant solutions. The three bacteria were each reduced to undetectable levels at low (0.5 A) and relatively higher levels (1.0 A) of current in tap water and "artificial process water", respectively. The residual effect of EOW on P. fluorescens, P. agglomerans or R. aquatilis was determined by incubating at room temperature 1 ml (approximately 9 log CFU/ml) pure culture suspensions in 9 ml of EOW-T (EOW produced from tap water), EOW-A (EOW produced from "artificial process water" supplemented with approximately 60.7 mg Cl(-)/l and 39.3 mg Na(+)/l) or deionised water (control) for 0, 15, 45 or 90 min. The bactericidal activity of both EOW-T and EOW-A increased with the concentration of free oxidants and incubation period and the three bacteria were completely reduced at free oxidants-incubation period combinations of 3.88 mg/l-45 min and 5.1 mg/l-90 min in EOW-T and EOW-A, respectively. Two types of industrial vegetable process water; salad-mix and soup process water, which had each a total psychrotrophic count of approximately 8 log CFU/ml were then electrolysed. Without any NaCl addition, only 1.2 and 2.1 log reductions of the psychrotrophs in soup and salad-mix process water was attained respectively. Supplementation of the process water with approximately 60.7 mg Cl(-)/l and 39.3 mg Na(+)/l afterwards resulted in complete reduction of the psychrotrophic count in both process waters, but soup process water required relatively higher levels of current compared to salad-mix water. Finally, fresh-cut lettuce was washed in EOW-T containing 3.62 mg free oxidants/l, EOW-IP (EOW produced from industrial process water) containing 2.8 mg free oxidants/l or tap water (control) for 1 or 5 min. Washing the vegetables for 1 min in EOW-T resulted in 1.9, 1.2, and 1.3 log reductions of psychrotrophs, lactic acid bacteria and Enterobacteriacae, respectively, which increased to 3.3, 2.6, and 1.9 log reductions after washing for 5 min instead. EOW-IP tested in this work had no bactericidal effect on the microflora of fresh-cut lettuce. Electrolysis could therefore be used to decontaminate process water for vegetable pre-washing and to sanitise tap water for final rinsing of vegetables, respectively.     

Consumption of raw vegetables and fruits: a risk factor for Campylobacter infections

The purpose of this study was to determine the prevalence of Campylobacter in fresh vegetables and fruits at retail level in the Netherlands, and to estimate its implications on the importance of vegetables and fruits as risk factor for campylobacteriosis.Thirteen of the 5640 vegetable and fruit samples were Campylobacter positive, resulting in a prevalence of 0.23% (95% confidence interval (Cl): 0.12-0.39%). The prevalence of packaged products (0.36%, 95% Cl: 0.17-0.66) was significantly higher than of unpackaged products (0.07; 95% Cl: 0.01-0.27). No statistical differences were found between seasons.Combining the mean prevalence found in this study with data on the consumption of vegetables and fruits, an exposure of 0.0048 campylobacters ingested per person per day in the Netherlands by transmission via vegetables and fruits, was calculated. This exposure, as input in a Beta-Poisson dose-response model, resulted in an estimated number of 5.3 × 10⁵ cases of infection with Campylobacter per year for the whole Dutch population. This constitutes the consumption of raw vegetables and fruits, especially when packaged, to be a risk factor for Campylobacter infections.     

Resistance of pathogenic bacteria on the surface of stainless steel depending on attachment form and efficacy of chemical sanitizers

Various bacteria including food spoilage bacteria and pathogens can form biofilms on different food processing surfaces, leading to potential food contamination or spoilage. Therefore, the survival of foodborne pathogens (Escherichia coli O157:H7, Listeria monocytogenes, Salmonella typhimurium, Staphylococcus aureus, Cronobacter sakazakii) in different forms (adhered cells, biofilm producing in TSB, biofilm producing at RH 100%) on the surface of stainless steel and stored at various relative humidities (RH 23%, 43%, 68%, 85%, and 100%) at room temperature for 5 days was investigated in this study. Additionally, the efficacy of chemical sanitizers (chlorine-based and alcohol-based commercial sanitizers) on inhibiting various types of biofilms of E. coli O157:H7 and S. aureus on the surface of stainless steel was investigated. The number of pathogens on the surface of stainless steel in TSB stored at 25 °C for 7 days or RH 100% at 25 °C for 7 days was significantly increased and resulted in the increase of 3 log₁₀ CFU/coupon after 1 day, and these levels were maintained for 7 days. When stainless steel coupons were stored at 25 °C for 5 days, the number of pathogens on the surface of stainless steel was significantly reduced after storage at RH 23%, 43%, 68%, and 85%, but not at 100%. When the bacteria formed biofilms on the surface of stainless steel in TSB after 6 days, the results were similar to those of the attached form. However, levels of S. aureus and C. sakazakii biofilms were more slowly reduced after storage at RH 23%, 43%, 68%, and 85% for 5 days than were those of the other pathogens. Formation of biofilms stored at RH 100% for 5 days displayed the highest levels of resistance to inactivation. Treatment with the alcohol sanitizer was very effective at inactivating attached pathogens or biofilms on the surface of stainless steel. Reduction levels of alcohol sanitizer treatment ranged from 1.91 to 4.77 log and from 4.35 to 5.35 log CFU/coupon in E. coli O157:H7 and S. aureus, respectively. From these results, the survival of pathogens contaminating the surfaces of food processing substrates such as stainless steel varied depending on RH and attachment form. Also, alcohol-based sanitizers can be used as a potential method to remove microbial contamination on the surfaces of utensils, cooking equipment, and other related substrates regardless of the microbial attached form.     

Development of a proposed standard method for assessing the efficacy of fresh produce sanitizers

A series of studies was done for the purpose of developing a proposed standard method to evaluate point-of-use home sanitizers for fresh produce. Preliminary experiments were done to determine the survival of Escherichia coli O157:H7, Salmonella, and Listeria monocytogenes after inoculation onto the surface of ripe tomatoes and drying for up to 24 h at 22 +/- 2 degrees C. Within 2 h, the initial population (6.88 log10 CFU/tomato) of E. coli O157:H7 was reduced by approximately 3 log10, while reductions in similar initial populations of Salmonella and L. monocytogenes were approximately 1 and 0.6 log10 CFU/tomato, respectively, after 40 min and 3 h. A pilot study evaluated treatment with 200 ppm free chlorine and a prototype Fit produce wash (Fit) for their efficacy in killing a five-serotype mixture of Salmonella or L. monocytogenes spot inoculated on tomatoes using the proposed inoculation and recovery procedures. Inoculated tomatoes were sprayed with chlorinated water, Fit, or sterile distilled water (control) and hand rubbed for 30 s. Each tomato was then placed in a plastic bag and rinsed with 200 ml of sterile water by vigorously agitating for 30 s to simulate a procedure consumers might use for sanitizing and rinsing produce in a home setting. Each tomato was transferred to a second bag, and 20 ml of sterile 0.1% peptone was added; tomatoes were rubbed by hand for 40 s. Populations of Salmonella or L. monocytogenes in the rinse water and the 0.1% peptone wash solution were determined. Treatment with 200 ppm chlorine and Fit resulted in > or = 3.07 and > 6.83 log10 reductions, respectively, in Salmonella. Treatment with 200 ppm chlorine and Fit reduced the number of L. monocytogenes by > or = 3.33 and > or = 4.96 log10 CFU/tomato, respectively. The proposed standard method for testing the efficacy of point-of-use produce sanitizers needs to be evaluated for reproducibility of results through a larger scale series of experiments.     

Occurrence of parasites on fruits and vegetables in Norway.

Between August 1999 and January 2001, samples of various fruits and vegetables obtained within Norway were analyzed by published methods for parasite contamination. Neither Cyclospora oocysts nor Ascaris (or other helminth) eggs were detected on any of the samples examined for these parasites. However, of the 475 samples examined for Cryptosporidium oocysts and Giardia cysts, 29 (6%) were found to be positive. No samples were positive for both parasites. Of the 19 Cryptosporidium-positive samples. 5 (26%) were in lettuce, and 14 (74%) in mung bean sprouts. Of the 10 Giardia-positive samples, 2 (20%) were in dill, 2 (20%) in lettuce, 3 (30%) in mung bean sprouts, 1 (10%) in radish sprouts, and 2 (20%) in strawberries. Mung bean sprouts were significantly more likely to be contaminated with Cryptosporidium oocysts or Giardia cysts than the other fruits and vegetables. Concentrations of Cryptosporidium and Giardia detected were generally low (mean of approximately 3 [oo]cysts per 100 g produce). Although some of the contaminated produce was imported (the majority, if sprouted seeds are excluded), there was no association between imported produce and detection of parasites. Crvptosporidium oocysts and Giardia cysts were also detected in water samples concerned with field irrigation and production of bean sprouts within Norway. This is the first time that parasites have been detected on vegetables and fruit obtained in a highly developed. wealthy country, without there being an outbreak situation. These findings may have important implications for global food safety.     

Development and validation of a front-face fluorescence spectroscopy-based method to determine casein in raw milk

A front-face fluorescence spectroscopy (FFFS)-based method for measuring casein in raw milk was developed and validated. Calibration samples (n_cal = 20) with different casein contents (0.36–3.7%) were prepared by mixing ultrafiltered retentate (2 × concentrate) and permeate at different ratios. A principal component regression model was developed using the calibration fluorescence spectra, showing a useful prediction power based on a residual prediction deviation of 3.1. The calibration model was independently validated using 20 raw milk samples. The FFFS-based method showed a root mean square error of prediction of 0.15% and 6.7% relative prediction error. A larger sample size should be included in the future to further validate the method and potentially implement it for routine measurement of casein levels in raw milk.     

辐照技术在果蔬保鲜中的应用研究进展

到目前为止,对新鲜食物中病菌病原体的控制,我们做的还不够,然而,最近有人报导可以采用电离辐照技术来消除苹果汁中的大肠杆菌O157：H7,本莓中的Toxoplamagondii和/或Cydospo-racayetanenis以及种子和芽中的大肠杆菌O157：H7及消门氏菌,一些国家正在寻找有效的方法来控制鲜果、果汁、生菜或色拉、嫩芽以及种子中的病菌病原体,电离辐射以及其它过程（如氯化作用）相结合似乎是一种特殊有前途的方法。     

Rapid method for the simultaneous GC quantitation of acids and sugars in fruits and vegetables.

Rapid methods of analysis for the simultaneous determination of acids and sugars in fruits and vegetables using trimethylsilylation and gas chromatography are reported. The methods have been shown to be generally applicable, rapid, simple and cheap. Typical applications are shown involving the determination of a range of organic acids and sugars in carrot, potato, cucumber, tomato, apple, pear, grape, strawberry and citrus fruits.     

Development of a quantitative real-time PCR method to enumerate total bacterial counts in ready-to-eat fruits and vegetables

A newly developed real-time PCR assay rapidly quantifies the total bacterial numbers in contaminated ready-to-eat vegetables and fruits compared with the standard plate count method. Primers targeting the rpoB gene, which encodes for the beta subunit of the bacterial RNA polymerase and which is common to most bacterial species, was used instead of the 16S rRNA gene, which has multiple copies and varies among bacterial species. A primer pair specific for rpoB was confirmed to amplify rpoB in a wide range of bacterial species after we assessed 49 strains isolated from five kinds of fruits and vegetables. We purchased fruits and vegetables from retail shops and enumerated the bacteria associated with them by use of real-time PCR and compared this to the number found by the culture method. We found a high correlation between the threshold PCR cycle number when compared with the plate count culture number. The real-time PCR assay developed in this study can enumerate the dominant bacterial species in ready-to-eat fruits and vegetables.     

蔬菜水果中腐霉利快速检测方法的优化

通过选购市场上常见的腐霉利胶体金免疫层析产品,优化主流腐霉利快检产品的前处理步骤,确定检测方法的性能指标,考察每种胶体金快检产品在果蔬基质样品检测中的灵敏度、特异性、假阳性率、假阴性率和交叉反应,建立一种蔬菜水果中腐霉利的胶体金免疫层析快速检测方法。结果表明,最优提取条件为提取液为Tris-盐酸-10%甲醇缓冲液,提取液pH值为9.0,提取液采用过滤的处理方式,该方法检出限为0.2 mg/kg,灵敏度为100%、特异性为100%、假阳性率为0、假阴性率为0,与10种农药无交叉反应,该方法与参比方法的阳性确证比率在95%的置信区间内无显著性差异,真实阳性样本两种方法检测结果均为阳性。该方法灵敏、快速、准确,可用于蔬菜水果中腐霉利残留的现场快速检测。     

蔬菜水果中菊酯类农药残留快速检测的方法研究

为研究一种蔬菜水果中菊酯类农药残留快速检测方法,通过选购市场上常见的胶体金免疫层析产品及菊酯类农药,对蔬菜水果中菊酯农残的快速检测进行前处理步骤的优化,并考察每种胶体金免疫层析产品在果蔬基质样品检测中的灵敏度、特异性、假阳性率、假阴性率和准确度,以实现胶体金免疫层析产品的整体性评价。结果表明,直接稀释法检测大白菜、韭菜和柑橘时,检测限较高,无法满足检测要求;直接提取法适用于大白菜、韭菜和柑橘的快速检测,检测限为2 mg/kg。方法学验证结果表明：以大白菜、韭菜和柑橘作为空白基质的检测限为2 mg/kg,灵敏度均为100%,特异性为100%,假阳性率为0,假阴性率为0。该方法快速准确、灵敏度高,可适用于蔬菜水果中菊酯类农药残留的快速检测。     

Evaluation of extraction method for the analysis of carotenoids in fruits and vegetables

This study evaluated a suitable extraction method for a wide range of sample matrices in carotenoid analysis. Using canned tomato juice as a representative sample, it is shown that two solvents of low biological hazard, ethanol and hexane are the most suitable for extracting carotenoids from the matrix. The use of double extraction, each with 35 ml of ethanol:hexane mixture (4:3, by volume), resulted in good recoveries of carotenoids (lycopene 96%, α-carotene 102% and β-carotene 93–100%). Coefficients of variation conducted on different days were: lycopene 5% and β-carotene 7%. An application of the established method to various kinds of fruit and vegetable matrices is also shown, using carrot and spinach as representative samples of root and leafy vegetables, for determining recoveries of added carotenoids. The average percent recoveries of added carotenoids from canned tomato juice, carrot and spinach were: 101, 99.8 and 101% for α-carotene (12.4, 24.8, 49.6 and 99.2 μg/10 ml of added α-carotene); and 98.1, 99.7 and 96.1 percent for β-carotene (25.5, 50.9, 101 and 201 μg/10 ml of added β-carotene). These similar recoveries over the explored concentration ranges confirm that the application of established extraction method is unaffected by differences in matrix composition of the samples.     

中草药提取液对几种果蔬采后病原真菌的离体抑制作用研究

为寻找天然果蔬防腐剂,在离体条件下,采用生长速率法研究了17种含有抗茵成分的中草药提取液对几种果蔬采后病原真菌的抑制效应.结果表明:17种中草药提取液对苹果轮纹病菌(Physalospora piricola)、链格孢茵(Alternaria alternata)、褐腐病菌(Monilinia fructicola)的抑制效果强弱不同,其中2号黄连对3种病原菌的抑制作用最好,抑制率达到85%以上;其次是8号黄柏、1号鹿蹄草、4号苦参,抑制率也达到60%以上.     

Antimicrobial efficacy of citron essential oil on spoilage and pathogenic microorganisms in fruit-based salads

The aim of this study was the evaluation of the effects of pure citral and citron essential oil on microbial spoilage and growth and survival of pathogenic microorganisms during storage. They were added in the syrup of industrial ready-to-eat fruit salads stored at 9 degrees C. Both citral (25 to 125 ppm) and citron essential oil (300, 600, 900 ppm) were able to prolong the microbial shelf life of the fruit-based salads. The essential oil gave excellent results, avoiding the undesirable effects attributable to the cytotoxicity of citral. Citron essential oil doubled the time needed for the wild microflora to reach concentrations able to produce a perceivable spoilage in condition of thermal abuse (9 degrees C). The same essential oil had reduced effects on the survival of Gram-negative species Salmonella Enteritidis and Escherichia coli, but showed a strong inhibition toward the Gram-positive pathogen Listeria monocytogenes.     

国内外生鲜牛肉食源性致病微生物标准限量比较研究

论述了我国生鲜牛肉中主要食源性致病微生物的危害及污染状况,指出我国生鲜牛肉存在着被各种食源性致病菌污染的情况和风险。通过对国外一些国家的食源性致病微生物限量标准进行比较分析,指出我国生鲜牛肉食源性致病微生物限量标准与国际标准存在一定的差距,以及我国建立生鲜牛肉食源性致病微生物限量标准的重要性和紧迫性,并对我国生鲜牛肉微生物限量标准制定提出几点建议和意见。     

Current concepts on the texture of fruits and vegetables

Recent research on the texture of fruits and vegetables is evaluated with regard to the relationship between the various facets of perceived texture such as cohesiveness, etc. and the geometrical, physical, and chemical properties of food. The role of polymeric materials such as pectin and cellulose, and their interaction with other components, receives special attention. Coming under consideration are the size of the cells, turgor and factors affecting it, the mechanical properties of cell walls and intercellular adhesion. The influences of storage, heat, chemicals, and enzymes on these characteristics provide insight into their fundamental contributions to texture. Further, the chemical composition and structural components of comminuted foods are related to their texture and rheology.     

Influence of preparation method on the hedonic response of preschoolers to raw,boiled or oven-baked vegetables

Aim of this study was to assess how different preparation methods influence the hedonic response to vegetables of preschoolers aged four to five. Children (n = 52) scored for liking on a 5-point non gender facial scale six vegetables (carrot, tomato, zucchini, spinach, fennel and Catalogna chicory) prepared in three different ways: raw, boiled and oven-baked.A trained sensory panel determined the sensory profile of vegetable dishes. Significant differences in liking (P < 0.001) were found across dishes. Vegetable liking depended significantly on the vegetable type, the method of preparation which modulates the effect of vegetable type, and the heterogeneity in individual children response. Suitability of preparation method was specific to individual vegetable and could not be generalized to all types of vegetables.Neophobia and familiarity with specific vegetable types had a significant effect (P < 0.001) on liking.Nearly one child out of two related vegetable acceptance to sensory characteristics of vegetables. For sensory oriented children, sweetness and original colour intensity affected positively vegetable acceptance while bitterness, brown colouring and tough texture lowered acceptance.These results help to optimize the sensory properties preferred by children through the selection of the most appealing preparation method for a given vegetable.     

Measurements of the antioxidant capacity of fruits and vegetables using the BR reaction method

The antioxidant capacity of aqueous extracts of 20 vegetables and 16 fruits have been determined using the Briggs-Rauscher (BR) reaction method. Like other methods, the BR reaction method is also based on the generation of free radicals in the reaction mixture. Antioxidant scavengers of free radicals added to an active oscillatory BR regime cause an immediate cessation of the oscillatory regime, an inhibition time that linearly depends on the amount of the antioxidant added, and subsequent regeneration of oscillations. The BR reaction method works at pHƺ, which is similar to that of the fluids in the human stomach. It is known that a vegetarian diet can reduce the risk of stomach cancer and it is therefore interesting to determine the activity of antioxidants at low pH values. Different plants were tested with the BR reaction method, recording potentiometrically the inhibition times produced by their extracts on an active BR mixture. The results concerning the order of the antioxidant activity of the examined plants are illustrated and discussed. A comparison with the ranking order obtained with other methods is also given.     

Validation study on a method for multiresidue analysis of pesticides in vegetables and fruits with supercritical fluid extraction

Supercritical fluid extraction (SFE) was applied to extraction of pesticides from vegetables and fruits. Residues were extracted from homogenized samples mixed with water-absorbent polymer with supercritical carbon dioxide in a stainless steel tube, followed by elution with acetone. Co-extractives were removed by means of mini-column clean-up. Measurement was performed by GC-MS/MS. Calibration was achieved by preparing matrix-matched calibration standards to counteract matrix effects. With the Japanese method validation guideline as a reference, the method was assessed in 5 agricultural products spiked with 334 pesticides at 0.01 and 0.1 μg/g. Compounds at each level were extracted from 2 samples on 5 separate days. The trueness of the method for 189 pesticides in all samples was 70-120%, and the repeatability and within-run reproducibility were also consistent with the guideline. The trueness of the method for the other 71 pesticides was in the range of 50-70%, though the repeatability and within-run reproducibility were satisfactory. This method is available as a multiresidue analysis method for vegetables and fruits.