Efficacy of Combined Sous Vide‐Microwave Cooking for Foodborne Pathogen Inactivation in Ready‐to‐Eat Chicory Stems

There is a variety of different food processing methods, which can be used to prepare ready‐to‐eat foods. However, the need to preserve the freshness and nutritional qualities leads to the application of mild technologies which may be insufficient to inactivate microbial pathogens. In this work, fresh chicory stems were packed under a vacuum in films, which were transparent to microwaves. These were then exposed to microwaves for different periods of time. The application of sous vide microwave cooking (SV‐MW, 900 W, 2450 MHz), controlled naturally occurring mesophilic aerobic bacteria, yeasts and molds for up to 30 d when vacuum‐packed vegetables were stored at 4 °C. In addition, the process lethality of the SV‐MW 90 s cooking was experimentally validated. This treatment led to 6.07 ± 0.7 and 4.92 ± 0.65 log cfu/g reduction of Escherichia coli and Listeria monocytogenes inoculated over the chicory stems (100 g), respectively. With an initial load of 9 log cfu/g for both pathogens, less than 10 cfu/g of surviving cells were found after 90 s cooking. This shows that short‐time microwave cooking can be used to effectively pasteurize vacuum‐packed chicory stems, achieving >5 log cfu/g reduction of E. coli and L. monocytogenes.     

Suitability,efficiency and microbiological safety of novel physical technologies for the processing of ready‐to‐eat meals,meats and pumpable products

Consumer studies and market reports show an increase in consumption of ready‐to‐eat (RTE) foods. Although conventional processing technologies can in most cases produce safe products, they can also lead to the degradation of nutritional compounds and negatively affect quality characteristics. Consumers strongly prefer food that is minimally processed with the maximum amount of health‐promoting substances. Novel processing technologies as pre‐ or post‐treatment decontamination methods or as substitutes of conventional technologies have the potential to produce foods that are safe, rich in nutrient content and with superior organoleptic properties. Combining novel with conventional processes can eliminate potential drawbacks of novel technologies. This review examines available scientific information and critically evaluates the suitability and efficiency of various novel thermal and nonthermal technologies in terms of microbial safety, quality as well as nutrient content on the production of RTE meals, meats and pumpable products.     

Biogenic amine content in Chilean Gauda cheese: physico‐chemical and microbiological factors that may influence this content

The presence of four biogenic amines in Chilean Gauda cheese was studied, and the effect of certain factors may influence the production of those amines. Histamine, tyramine, putrescine and cadaverine were quantified with high‐performance liquid chromatography (HPLC), in cheeses from the three major Chilean cheese manufacturers. Multiple regression analysis revealed that water activity, free amino acid content and the Enterobacteriaceae count all favoured production of biogenic amines. The total amount of biogenic amines in the samples studied was between 47.9 and 150.5 mg/kg of cheese, much lower than that associated with a possible consumer health risk (1000 mg/kg).     

Microbiological,physical and chemical characteristics of freshwater prawns (Macrobrachium rosenbergii) in modified‐atmosphere packaging

This study evaluated the influence of packaging atmosphere (air versus 50% N₂/50% CO₂) on microbiological (mesophiles, psychrotrophs), physical (gas measurement) and chemical (pH, total volatile basic nitrogen [TVB‐N], NH₃, H₂S and biogenic amines) parameters in freshwater prawns during storage at 0 ± 1 °C for 240 h. To select the most appropriate packaging, 21 batches of each treatment were analysed. Both the packaging permeability and the combination of gases affected the shelf life, but the modified‐atmosphere packaging (MAP) was more efficient than air packaging, increasing the shelf life by 40 h. The parameters of pH and TVB‐N showed no statistical difference between the two atmosphere conditions all along the storage period. The biogenic amine agmatine showed potential for use as a quality indicator due to the increased concentration during storage. In further studies, this amine can be applied as an indicator for public health issue.     

Effect of y‐radiation on chives safety and quality

The effect of γ‐irradiation on the quality of chives was evaluated. The samples were irradiated at 1.0 and 2.0 kGy, stored at 4 °C for 10 days and used for microbiological (aerobic mesophilic, moulds and yeasts, E. coli and Salmonella sp), biochemical (vitamin C and lipoperoxide (MDA) contents and superoxide dismutase (SOD) and guaiacol peroxidase (POX) activity) and sensorial evaluation. For irradiated samples, the total counts of aerobic mesophilic and moulds and yeasts showed a reduction of 6 log cycles during storage, and colour analysis showed no significant difference (P > 0.05) for the b*‐value. The contents of vitamin C were not significantly affected by irradiation and storage time. The MDA contents and SOD activity changed insignificantly at both γ‐irradiation levels after storage, while POX was significantly increased (P ≤ 0.05) at 1 kGy. Samples irradiated at 2.0 kGy presented sensorial acceptance after the storage. These results show that γ‐irradiation increases the shelf life of chives without significant changes in their quality.     

Microbial Safety and Shelf Life of UV‐C Treated Freshly Squeezed White Grape Juice

The effects of UV‐C irradiation on the inactivation of Escherichia coli K‐12 (ATCC 25253), a surrogate of E. coli O157:H7, and on the shelf life of freshly squeezed turbid white grape juice (FSWGJ) were investigated. FSWGJ samples were processed at 0.90 mL/s for 32 min by circulating 8 times in an annular flow UV system. The UV exposure time was 244 s per cycle. The population of E. coli K‐12 was reduced by 5.34 log cycles after exposure to a total UV dosage of 9.92 J/cm² (1.24 J/cm² per cycle) at 0.90 mL/s flow rate. The microbial shelf life of UV‐C treated FSWGJ was extended up to 14 d at 4 °C. UV exposure was not found to alter pH, total soluble solid, and titratable acidity of juice. There was a significant effect (P < 0.05) on turbidity, absorbance coefficient, color, and ascorbic acid content. Furthermore, all physicochemical properties were altered during refrigerated storage. The microbial shelf life of FSWGJ was doubled after UV‐C treatment, whereas the quality of juice was adversely affected similarly observed in the control samples.     

Shelf‐life extension of vacuum‐packaged sea bream (Sparus aurata) fillets by combined γ‐irradiation and refrigeration: microbiological,chemical and sensory changes

The combined effect of γ‐irradiation and refrigeration on the shelf‐life of vacuum‐packaged sea bream (Sparus aurata) fillets was studied by monitoring the microbiological, chemical and sensory changes of non‐irradiated and irradiated fish samples using low‐dose irradiation doses of 1 and 3 kGy. Fish species such as sea bream and sea bass are very popular in the Mediterranean countries due to their high quality characteristics, and their preservation is a constant challenge given their extreme perishability. Irradiation (3 kGy) dramatically reduced populations of bacteria, namely, total viable counts (3 vs 7 log cfu g^?1) for the non‐irradiated samples, Pseudomonas spp (<2 vs 7.6 log cfu g^?1), H₂S‐producing bacteria typical of Shewanella putrefaciens (<2 vs 5.9 log cfu g^?1), Enterobacteriaceae (<2 vs 6.0 log cfu g^?1) and lactic acid bacteria (<2 vs 3.5 log cfu g^?1) after 10 days of storage. The effect was more pronounced at the higher dose (3 kGy). Lactic acid bacteria, Enterobacteriaceae and H₂S‐producing bacteria typical of Shewanella putrefaciens showed higher sensitivity to γ‐radiation than did the rest of the microbial species. Of the chemical indicators of spoilage, Trimethylamine (TMA) values of non‐irradiated sea bream increased very slowly, whereas for irradiated samples significantly lower values were obtained reaching a final value of 7.9 and 6.3 mg N per 100 g muscle at 1 and 3 kGy respectively (day 42). Total volatile basic nitrogen (TVB‐N) values increased slowly attaining a value of 67.3 mg N per 100 g for non‐irradiated sea bream during refrigerated storage, whereas for irradiated fish, lower values of 52.8 and 43.1 mg N per 100 g muscle were recorded (day 42). Thiobarbituric acid (TBA) values for irradiated sea bream samples were higher than respective non‐irradiated fish and increased slowly until day 21 of storage, reaching final values of 1.1 (non‐irradiated), 2.0 (1 kGy) and 2.2 mg malonaldehyde kg^?1 muscle (3 kGy), respectively (day 42). Sensory evaluation showed a good correlation with bacterial populations. On the basis of overall acceptability scores (sensory evaluation) a shelf‐life of 28 days (3 kGy) was obtained for vacuum‐packaged sea bream, compared with a shelf‐life of 9–10 days for the non‐irradiated sample. Copyright © 2004 Society of Chemical Industry     

Time–Temperature Management Along the Food Cold Chain: A Review of Recent Developments

The cold chain is responsible for the preservation and transportation of perishable foods in the proper temperature range to slow biological decay processes and deliver safe and high‐quality foods to consumers. Studies show that the efficiency of the cold chain is often less than ideal, as temperature abuses above or below the optimal product‐specific temperature range occur frequently, a situation that significantly increases food waste and endangers food safety. In this work, field studies on time–temperature conditions at each critical stage of the cold chain are reviewed to assess the current state of commercial cold chains. Precooling, ground operations during transportation, storage during display at retail and in domestic refrigerators, and commercial handling practices are identified and discussed as the major weaknesses in the modern cold chain. The improvement in efficiency achieved through the measurement, analysis, and management of time–temperature conditions is reviewed, along with the accompanying technical and practical challenges delaying the implementation of such methods. A combination of prospective experimental and modeling research on precooling uniformity, responsive food inventory management systems, and cold chains in developing countries is proposed for the improvement of the cold chain at the global scale.     

分子生物学技术在预测微生物学中的应用与展望

预测微生物学是食品微生物学的重要组成部分,其本质在于利用数学模型描述特定环境条件下微生物的生长和死亡规律。预测微生物模型既能应用于预测食品的货架期、控制腐败菌的滋生,又有助于完善食品微生物风险评估体系,减少致病菌的患病风险,对保障食品安全和改善公共卫生状况具有十分重要的意义。本文以综述的形式,概述预测微生物学的发展历史,并分析当前预测微生物学的研究热点。在此基础之上,着重介绍分子生物学技术在预测微生物学中应用的最新研究进展,阐述分子预测模型的概念和构建方法,并对其他分子生物学技术在预测微生物学中应用的可行性以及分子预测模型的应用前景进行展望,以期为全面推动预测微生物学这一学科的进步提供理论参考。     

我国部分地区2010年产谷物及其制品中多组分真菌毒素污染状况研究

目的 了解我国部分地区2010年产谷物及其制品中多组分真菌毒素污染状况.方法 2010年在安徽、云南、福建、甘肃、广西、海南、黑龙江、湖北、湖南、江西、山西和上海12个省(市/自治区)采集玉米及其制品、小麦粉、大米和花生共计650份样品,用超高效液相色谱-串联质谱(UPLC-MS/MS)方法检测14种真菌毒素.结果 玉米制品和小麦粉样品中污染的真菌毒素主要是B类单端孢霉烯族化合物和玉米赤霉烯酮(ZEN).215份玉米样品中有84.65％检出脱氧雪腐镰刀菌烯醇(DON),其中7份样品中的DON污染水平超过我国规定的1 000μg/kg限量标准,超标1.08 ～2.51倍(平均1.77倍);69.30％ (149/215)的玉米样品ZEN阳性,其中23份样品中的ZEN水平超过我国规定的60 μg/kg限量标准,超标1.06～19.19倍,平均4.32倍.53.02％的玉米样品还受到黄曲霉毒素的污染,其中有12份样品中AFB1含量超过了我国规定的20 μg/kg限量标准,尤以云南、广西样品受污染较重.125份小麦粉样品中,仅有1份来自湖北的样品其DON污染水平(1 016.80 μg/kg)超过我国规定的1 000 μg/kg限量标准.40.41％的花生样品不同程度地受到黄曲霉毒素的污染,其中有5份样品中的AFB1水平超过20 μg/kg的国家限量标准;大米受真菌毒素的污染较轻.结论 我国玉米制品和小麦粉受多种真菌毒素污染,且以B类单端孢霉烯族化合物和ZEN为主;玉米和花生不同程度地受到黄曲霉毒素的污染.     

Development of a Method for Evaluating Floor Dry‐Cleanability from Wheat Flour in the Food Industry

Many productive processes are characterized by inadequate protocols of sanitation that increase the possibility of proliferation of microbial contaminants, especially on surfaces. The use of this method for evaluating the degree of floor cleanability in agri‐food companies is important not only to reduce the risk of contamination of products, but also to provide companies with a tool to identify critical issues. The method is based on the usage of bicinchoninic acid assay (BCA) in a solution at a 1:50 ratio of Cu²⁺/BCA, which is ideal for detecting the amount of proteins contained in wheat flour residues on industrial flooring. Spectrophotometric analysis allowed identifying maximum absorbance values at 562 nm for different protein concentrations, although the construction of a regression function led to the definition of the intervals of evaluation corresponding to different degrees of cleanliness from residues of wheat flour. The results of the absorbance curves, obtained by applying the proposed evaluation method to 6 tiles commonly used in agri‐food buildings, showed the clear persistence of food material on 2 tiles with surface relief. In particular, such tiles showed a higher presence of proteins, with a level of contamination 440% higher. Furthermore, a robotic system was designed to standardize the cleaning method commonly employed in agri‐food companies to remove solid particles from flooring.     

A Comparative Study of Natural Antimicrobial Delivery Systems for Microbial Safety and Quality of Fresh‐Cut Lettuce

Nanoencapsulation can provide a means to effectively deliver antimicrobial compounds and enhance the safety of fresh produce. However, to date there are no studies which directly compares how different nanoencapsulation systems affect fresh produce safety and quality. This study compared the effects on quality and safety of fresh‐cut lettuce treated with free and nanoencapsulated natural antimicrobial, cinnamon bark extract (CBE). A challenge study compared antimicrobial efficacy of 3 different nanoencapsulated CBE systems. The most effective antimicrobial treatment against Listeria monocytogenes was chitosan‐co‐poly‐N‐isopropylacrylamide (chitosan‐PNIPAAM) encapsulated CBE, with a reduction on bacterial load up to 2 log₁₀ CFU/g (P < 0.05) compared to the other encapsulation systems when fresh‐cut lettuce was stored at 5 °C and 10 °C for 15 d. Subsequently, chitosan‐PNIPAAM‐CBE nanoparticles (20, 40, and 80 mg/mL) were compared to a control and free CBE (400, 800, and 1600 μg/mL) for its effects on fresh‐cut lettuce quality over 15 d at 5 °C. By the 10th day, the most effective antimicrobial concentration was 80 mg/mL for chitosan‐PNIPAAM‐CBE, up to 2 log₁₀ CFU/g reduction (P < 0.05), compared with the other treatments. There was no significant difference between control and treated samples up to day 10 for the quality attributes evaluated. Chitosan‐PNIPAAM‐CBE nanoparticles effectively inhibited spoilage microorganisms’ growth and extended fresh‐cut lettuce shelf‐life. Overall, nanoencapsulation provided a method to effectively deliver essential oil and enhanced produce safety, while creating little to no detrimental quality changes on the fresh‐cut lettuce.     

Application of nanoemulsion‐based approaches for improving the quality and safety of muscle foods: A comprehensive review

Recently, there has been growing interest in implementing innovative nanoscience‐based technologies to improve the health, safety, and quality of food products. A major thrust in this area has been to use nanoemulsions because they can easily be formulated with existing food ingredients and technologies. In particular, oil‐in‐water nanoemulsions, which consist of small oil droplets (<200 nm) dispersed in water, are being utilized as delivery systems for various hydrophobic substances in foods, including nutrients, nutraceuticals, antioxidants, antimicrobials, colors, and flavors. In this article, we focus on the application of nanoemulsion‐based delivery systems for improving the quality, safety, nutritional profile, and sensory attributes of muscle foods, such as meat and fish. The article also critically reviews the formulation and fabrication of food‐grade nanoemulsions, their potential benefits and limitations in muscle food systems.     

Low‐concentrated acidic electrolysed water treatment of pork: inactivation of surface microbiota and changes in product quality

The study analysed the effect of low‐concentrated acidic electrolysed water (LCAEW) treatment on meat. Microbiological analysis and colour and sensory quality testing during storage were performed on Longissimus thoracis. FT‐IR and FT‐Raman spectroscopy were used to detect eventual changes in the structure of meat after treatment. Meat samples were sprayed for 120 s with LCAEW (0.001%, 0.01% or 0.1% NaCl solution were electrolysed for 0, 5 or 10 min). The highest reduction in total number of micro‐organisms (3.25 log reduction), yeast and moulds (2.68 log reduction) and psychrotrophs (3.10 log reduction) was observed after spraying the meat samples with 0.1% NaCl electrolysed for 10 min. LCAEW caused a decrease in deoxymyoglobin and metmyoglobin concentration in unstored meat samples. The preliminary sensory studies proved that colour changes are not significant for consumers. The IR and Raman spectra indicate that the structure of compounds of meat tissues are not affected by chlorine and chlorine compounds (LCAEW components). LCAEW has no influence on denaturation of meat protein.     

Effects of tangential microfiltration and pasteurisation on the rheological,microbiological, physico‐chemical and sensory characteristics of sugar cane juice

The aim of this study was to determine the physico‐chemical, microbiological, rheological and sensory characteristics of sugar cane juice with passion fruit pulp (5% w/w) added and which had been submitted to microfiltration and pasteurisation (90 °C/30 s; 95 °C/30 s) processes. The results showed that the juices obtained after the microfiltration and pasteurisation processes had low microbial counts. The microfiltered juice showed a reduction in the soluble solids, acidity and vitamin C content (P = 0.05), while the pasteurised juice showed no change in these parameters (P > 0.05) in relation to the natural sugar cane juice, with the exception of vitamin C, which was not detected after the thermal treatment. In relation to the rheological properties, Newtonian behaviour was observed for both microfiltered and pasteurised juices. The sensory tests on a hedonic scale showed good acceptance of both juices (microfiltered and pasteurised).     

Influence of cultivation parameters on the composition of volatile compounds and physico‐chemical characteristics of kiwi fruit

BACKGROUND: The effect of four cultivation parameters (post‐maturity harvest date, storage period at 0 °C and input of nitrogen or potassium fertilisers) on the physico‐chemical characteristics and composition of volatile compounds in kiwi fruit (Actinidia deliciosa) were evaluated. Five physico‐chemical parameters were selected, namely, pH, total acidity, dry matter, conductivity and refractive index. To our knowledge, no published data are available concerning the influence of nitrogen or potassium fertilisers on the volatile compounds and physico‐chemical parameters in kiwi fruit. RESULTS: Except for total acidity, these parameters were only weakly influenced by cultivation parameters. The concentrations of five main volatile compounds [hexanal, (E)‐hex‐2‐enal, hexan‐2‐ol, ethyl butyrate and hexanol] were also measured using gas chromatography and gas chromatography‐mass spectrometry. This work showed that the total content of volatile compounds decreased with post‐maturity harvest date and storage period of 3 months. In contrast, the input levels of nitrogen and potassium had little effect on the concentrations of volatile components CONCLUSION: This study demonstrates a high degree of difference in the physiochemical parameters and volatile composition of kiwi fruit, depending on the harvest date, the time of storage and the input of fertilisers. © 2012 Society of Chemical Industry     

Influence of sorghum grain type on wort physico‐chemical and sensory quality in a whole‐grain and commercial enzyme mashing process

To determine the most suitable types of sorghum for whole‐grain adjunct in lager beer brewing, 14 cultivars of five different types: white tan‐plant, white non‐tan‐plant, red non‐tannin, white tannin (type II) and red tannin (type III) were evaluated. The effects of grain type on wort physico‐chemical and sensory quality with raw grain and malt plus commercial enzyme mashing were assessed. Tannin content correlated significantly and negatively with wort extract and fermentable sugars (p < 0.001) and free amino nitrogen (FAN; p < 0.1). This is attributable to inactivation of the exogenous enzymes by the tannins during the mashing process. However, the type II tannin sorghums had wort quality attributes closer to the non‐tannin sorghum types, probably owing to their relatively low tannin content (≤1%). Malting gave a great improvement in wort extract, fermentable sugars and FAN, but substantially influenced wort sensory properties in terms of higher sourness, bitterness and astringency, as well as the expected more malty flavour. Worts from raw red non‐tannin sorghums were similar to those of white tan‐plant sorghums in both physico‐chemical and sensory quality. Thus, red non‐tannin sorghums, in view of their better agronomic quality, have considerable potential as a whole‐grain adjunct in lager beer brewing. Copyright © 2013 The Institute of Brewing & Distilling