The Impact of Cooling Rate on the Safety of Food Products as Affected by Food Containers

In recent decades, the demand for ready‐to‐eat (RTE) food items prepared by the food catering sector has increased together with the value of cook‐serve, cook‐chill, and cook‐freeze food products. The technologies by which foods are cooked, chilled, refrigerated for storage, and reheated before serving are of prime importance to maintain safety. Packaging materials and food containers play an important role in influencing the cooling rate of RTE foods. Food items that are prepared using improper technologies and inappropriate packaging materials may be contaminated with foodborne pathogens. Numerous research studies have shown the impact of deficient cooling technologies on the survival and growth of foodborne pathogens, which may subsequently pose a threat to public health. The operating temperatures and cooling rates of the cooling techniques applied must be appropriate to inhibit the growth of pathogens. Food items must be stored outside the temperature danger zone, which is between 5 and 60 °C, in order to inhibit the growth of these pathogens. The cooling techniques used to prepare potentially hazardous foods, such as cooked meat, rice, and pasta, must be properly applied and controlled to ensure food safety. This paper critically reviews the effects of cooling and its relationship to food containers on the safety of RTE foods produced and sold through the food service industry.     

真空冷却技术在熟肉制品工业化生产中的应用研究

真空冷却技术是依据较高温度的含水物料在密封环境中真空的条件下通过水分迅速蒸发使物料自身得到迅速降温冷却的原理,这项快速蒸发冷却技术过去仅局限应用在蔬菜和鲜花的冷却保鲜等领域中,本课题研究真空冷却技术应用在熟肉制品生产的冷却工艺中,实验结果表明:相同的熟肉产品从95℃冷却到20℃,真空冷却比传统自然冷却速度快20倍以上,该技术可有效防止微生物在产品中的污染和增殖,提高产品的质量和安全性,延长产品货架期。研究同时就真空冷却技术对产品失水率的影响作了探讨。     

Control of Listeria monocytogenes Contamination in Ready‐to‐Eat Meat Products

The ubiquitous nature of Listeria monocytogenes and its ability to grow at refrigerated temperature makes L. monocytogenes a significant threat to the safety of ready‐to‐eat (RTE) meat products. The contamination by L. monocytogenes in RTE meat primarily occurs during slicing and packaging after cooking. The effectiveness of post‐package decontamination technology such as in‐package thermal pasteurization, irradiation, and high‐pressure processing are discussed. Formulating meat products with antimicrobial additives is another common approach to control L. monocytogenes in RTE meat. Irradiation is an effective technology to eliminate L. monocytogenes but can influence the quality of RTE meat products significantly. The effect of irradiation or the combination of irradiation and antimicrobials on the survival of L. monocytogenes and the quality of RTE meat is discussed.     

食品加工业中极具应用潜力的真空冷却技术

真空冷却是在真空下水分快速蒸发的预冷技术 ,可用于食品尤其适于叶类蔬菜的冷却。本文介绍了真空冷却技术的原理、在食品加工中的优缺点及其在水果、蔬菜、肉制品、鱼制品、调味品和焙烤食品中的应用     

Modelling the growth parameters of lactic acid bacteria and total viable count in vacuum‐packaged Irish cooked sausages cooled by different methods

The growth kinetics of lactic acid bacteria (LAB) and total viable count (TVC) in cooled sausages as a function of storage time was studied. Cooked sausages were cooled either by commercial cooling or by immersion vacuum cooling (IVC), then vacuum‐packaged and stored for up to 71 days at 4 °C. Baranyi model was used to fit the growth of LAB and TVC. Growth curve, growth rate, lag time and initial and final cell concentrations for LAB and TVC were calculated through DMFit. The coefficient of determination and root‐mean‐squared error of the Baranyi models were used to evaluate its accuracy. Sausages cooled by IVC had a longer lag time and shelf life period than commercial cooled sausages. Accuracy analysis showed that the Baranyi model was adequate for representing the bacterial growth of vacuum‐packaged cooled sausages and had a potential for shelf life prediction.     

食品真空冷却技术研究进展

真空冷却是一种快速、清洁的食品冷却技术,已经被广泛地应用于蔬菜、水果、焙烤食品、黏性食品、海鲜、小块熟肉以及切花的冷处理。然而,与传统的冷却方式（例如风冷和水冷等）相比,真空冷却却有失重率大和初投资大等缺点。随着社会的快速发展,人们对食品的质量安全要求越来越高。真空冷却技术作为最具潜力的高温食品快速冷却技术之一,在食品安全方面扮演的角色越来越重要。为促进真空冷技术的进一步研究,本文综述了国内外近些年来的部分研究成果。     

Modeling the Transfer of Salmonella Enteritidis during Slicing of Ready‐to‐Eat Turkey Products Treated with Thyme Essential Oil

The increased demand for low‐sodium ready‐to‐eat (RTE) meat products highlights the need for new strategies to ensure food safety. The application of essential oils (EOs) as natural antimicrobials in the meat industry has been suggested to prevent or control cross‐contamination during meat processing operations. This work aims to quantify and model the transfer of Salmonella Enteritidis during the slicing procedure of RTE turkey products treated with thyme essential oil (TEO) at a concentration of 0.1% (v/w). Two products were subjected to the slicing procedure with slicer blades inoculated with S. Enteritidis at 10⁸ cfu/mL. The Weibull and modified Weibull predictive models were fitted to the transfer data. Twenty slices were sampled and showed positive with bacteria, indicating cross‐contamination. The number of cells transferred per slice decreased logarithmically during the assays. The transfer models, based on the Weibull model, were suitable to describe the bacterial transfer trend on slices in most cases. TEO treatment reduced the transfer of Salmonella on a preservative free RTE turkey product. The predictive models obtained in this study can help food‐quality staff and managers on the design and assessment of processes to guard RTE turkey products against Salmonella. This work supports the addition of EOs to reduce microbial risk in RTE meat products.     

Fresh‐Cut Onion: A Review on Processing,Health Benefits,and Shelf‐Life

The ready‐to‐eat produce market has grown rapidly because of the health benefits and convenience associated with these products. Onion is widely used as an ingredient in an extensive range of recipes from breakfast to dinner and in nearly every ethnic cuisine. However, cutting/chopping of onion is a nuisance to many consumers due to the lachrymatory properties of the volatiles generated that bring tears to eyes and leave a distinct odor on hands. As a result, there is now an increasing demand for fresh‐cut, value‐added, and ready‐to‐eat onion in households, as well as large‐scale uses in retail, food service, and various food industries, mainly due to the end‐use convenience. Despite these benefits, fresh‐cut onion products present considerable challenges due to tissue damage, resulting in chemical and physiological reactions that limit product shelf‐life. Intensive discoloration, microbial growth, softening, and off‐odor are the typical deteriorations that need to be controlled through the application of suitable preservation methods. This article reviews the literature related to the fresh‐cut onion, focusing on its constituents, nutritional and health benefits, production methods, quality changes throughout storage, and technologies available to increase product shelf‐life.     

Development of a long‐life vacuum‐packaged ready‐to‐eat meat product based on a traditional Portuguese seasoned meat

Carne do alguidar is a Portuguese traditional pork fried meat, usually manufactured for self‐consumption purposes. This study developed a ready‐to‐eat (RTE) meat product, to meet today's consumers’ convenience, manufactured at the industrial scale evaluating its quality and shelf life, assessing the effect of vacuum packaging and the use of an antioxidant (50 ppm BHT) to enhance oxidative stability. Physicochemical and microbiological parameters were assessed, and a sensory analysis was performed. Interestingly, no significant differences were recorded between control (non‐BHT) and antioxidant (BHT) samples. Microbiological counts remained at low levels throughout the storage period, ensuring the product's required microbiological quality. At later storage stages, higher values of thiobarbituric acid‐reactive substances arose and off flavours and aromas were perceived. Still, overall appreciation was not affected until 12 months of storage and a significant depreciation was perceived only after 15 months. Fibrousness and rising of off flavours were negatively correlated with overall appreciation.     

An innovative method of immersion vacuum cooling for cooked meat products: immersion vacuum cooling with ultrasonic assistance

In this paper, immersion vacuum cooling with ultrasonic assistance (IVCUA) is compared with immersion vacuum cooling alone (IVC) and vacuum cooling (VC) for cooling time, mass loss, colour, texture profile and water mobility and compartmentalization for cooked meat products. The results reveal that IVCUA clearly enhances the boiling intensity of impregnation liquid compared to IVC. The total cooling time using IVC (126.56 min) for samples from 72 to 4 °C was significantly longer (P < 0.05) than that of IVCUA (96.89 min) and VC (80.48 min). The cooling time of samples from 10 to 4 °C by IVC (46.26 min) was higher (P < 0.05) than that by IVCUA (28.55 min). There were no significant differences (P > 0.05) in mass loss, colour and texture profile among all samples. However, IVCUA had a higher transverse relation time of bulk water (T₂₄) and MRI proton densities (P < 0.05), as well as a more uniform water distribution compared to IVC.     

食品真空冷却技术及其设备的设计

食品真空冷却装置是一种冷却速度快,冷却效果均匀、卫生的新型熟制食品生产设备。通过分析真空冷却的机理,探讨了食品真空冷却装置的设计原理,介绍了该装置的组成、工艺过程、关键技术及主要优缺点。该项技术及设备已在熟制食品生产中得到了应用。     

Evaluating the Performance of a New Model for Predicting the Growth of Clostridium perfringens in Cooked,Uncured Meat and Poultry Products under Isothermal,Heating, and Dynamically Cooling Conditions

Clostridium perfringens type A is a significant public health threat and its spores may germinate, outgrow, and multiply during cooling of cooked meats. This study applies a new C. perfringens growth model in the USDA Integrated Pathogen Modeling Program‐Dynamic Prediction (IPMP Dynamic Prediction) Dynamic Prediction to predict the growth from spores of C. perfringens in cooked uncured meat and poultry products using isothermal, dynamic heating, and cooling data reported in the literature. The residual errors of predictions (observation–prediction) are analyzed, and the root‐mean‐square error (RMSE) calculated. For isothermal and heating profiles, each data point in growth curves is compared. The mean residual errors (MRE) of predictions range from –0.40 to 0.02 Log colony forming units (CFU)/g, with a RMSE of approximately 0.6 Log CFU/g. For cooling, the end point predictions are conservative in nature, with an MRE of –1.16 Log CFU/g for single‐rate cooling and –0.66 Log CFU/g for dual‐rate cooling. The RMSE is between 0.6 and 0.7 Log CFU/g. Compared with other models reported in the literature, this model makes more accurate and fail‐safe predictions. For cooling, the percentage for accurate and fail‐safe predictions is between 97.6% and 100%. Under criterion 1, the percentage of accurate predictions is 47.5% for single‐rate cooling and 66.7% for dual‐rate cooling, while the fail‐dangerous predictions are between 0% and 2.4%. This study demonstrates that IPMP Dynamic Prediction can be used by food processors and regulatory agencies as a tool to predict the growth of C. perfringens in uncured cooked meats and evaluate the safety of cooked or heat‐treated uncured meat and poultry products exposed to cooling deviations or to develop customized cooling schedules. This study also demonstrates the need for more accurate data collection during cooling.     

Developments of mathematical models for simulating vacuum cooling processes for food products – a review

Vacuum cooling is a rapid cooling method widely used in cooling some food products. Simulating the vacuum cooling process with mathematical models helps to acquire a more intuitive understanding and optimize the whole cooling process. However, there is no review summarizing the mathematical models of vacuum cooling. In this review, heat and mass transfer process during vacuum cooling, types of mathematical models for vacuum cooling, and numerical methods including finite difference method, finite element method and finite volume method used for process simulation are introduced in details. The food products used in numerical simulation study of vacuum cooling generally include liquid food, vegetables and cooked meat. The ranges of application of various numerical methods are also discussed. Moreover, heat and mass transfer coefficients have a great influence on the accuracy of the model, and are generally provided by the literature. The investigations presented in this review invariably demonstrate that mathematical modeling can provide good prediction of key information of vacuum cooling process, and has a great potential to improve vacuum cooling process in the food industry. However, more efforts are still needed to realize the industrial translation of laboratory results.     

Prevalence of Listeria species in food products in Isfahan, Iran

A total of 617 meat and meat products, diary, vegetables and ready to eat food samples were collected. Listeria spp. isolated by using USDA method of isolation and L. monocytogenes identified by biochemical and Polymerase Chain Reaction (PCR). The incidence of Listeria spp. was 4.6% in all food samples. L. monocytogenes was found in 1.2% of food samples. It was found that Listeria spp. was present in 6.7% of meat and meat product samples, 1.3% of diary samples, 1.2% of vegetable samples and 12% ready to eat samples. The results presented in this study indicate, the potential risk of eating ready to eat food or raw and undercooked foods.     

Effects of processing parameters on immersion vacuum cooling time and physico-chemical properties of pork hams

The effects of agitation (1002 rpm), different pressure reduction rates (60 and 100 mbar/min), as well as employing cold water with different initial temperatures (IWT: 7 and 20 °C) on immersion vacuum cooling (IVC) of cooked pork hams were experimentally investigated. Final pork ham core temperature, cooling time, cooling loss, texture properties, colour and chemical composition were evaluated. The application for the first time of agitation during IVC substantially reduced the cooling time (47.39%) to 4.6 °C, compared to IVC without agitation. For the different pressure drop rates, there was a trend that shorter IVC cooling times were achieved with lower cooling rate, although results were not statistically significant (P > 0.05). For both IWTs tested, the same trend was observed: shorter cooling time and lower cooling loss were obtained under lower linear pressure drop rate of 60 mbar/min (not statistically significant, P > 0.05). Compared to the reference cooling method (air blast cooling), IVC achieved higher cooling rates and better meat quality.     

不同冷却方式对熟制馄饨品质的影响

通过真空冷却、鼓风冷却以及自然冷却3种方式对熟制馄饨进行冷却处理,并在4℃的条件下对产品密封储藏,研究随储存时间的延长,3种不同冷却方式处理的馄饨产品品质的变化情况。结果表明:与常规冷却方式相比较,真空冷却的冷却速率高(P<0.05),冷却失重率大(P<0.05);真空冷却的产品L*值偏小,a*值偏大(P<0.05);硬度和咀嚼性较大、弹性较低(P<0.05),但粘结性、黏性、回复性方面3种冷却方式没有显著差异。随着储藏时间的延长,真空冷却能显著降低馄饨产品的菌落总数、TBA值和pH值(P<0.05),减缓产品品质的劣变。     

Effect of temperature–time pretreatments on the texture and microstructure of abalone (Haliotis discus hanai)

The effects of temperature/time pretreatments on the texture and microstructure of abalone (Haliotis discus hanai ) meat with the same myofibril extraction rate (60–66.7%) were investigated. The abalone samples were categorized into control and four treatment groups of different heating temperature/heating time combinations as 50°C/120 min, 60°C/10 min, 70°C/5 min, and 80°C/2 min, respectively. Compared to the control samples, the abalone samples heated at 60°C/10 min were the most tender (minimum shear force). It is clear that a sharp reduction in hardness was observed in heat treated abalone meat samples, compared to the raw samples. Nuclear magnetic resonance (NMR) showed that the water distribution pattern in abalone samples changed as they were experiencing different heat treatments. Particularly, the immobilized water components in samples heated at 60°C/10 min increased significantly. The textural properties of these samples evaluated after an 80 s‐reheating by microwave were of superior quality. It is concluded that the optimal condition for pretreatment abalone was 60°C/10 min, which could significantly improve the textural properties of preprocessed abalones.

Practical applications

Ready‐to‐eat foods can either be consumed directly, or further prepared according to consumers' preference. They are processed and packed following scientifically defined criteria to meet ready‐to‐eat requirements. For consumers, the quality of the food is one of the most important factors affecting purchasing decisions. Pretreatment through heating plays a key role in determining the eating quality of the product. Our study investigated the effects of pretreatment temperature and time on the food quality. These findings will establish optimal conditions for pretreating abalone to develop high‐quality ready‐to‐eat food products.

     

Diversity of Antibiotic Resistance Genes in Enterococcus Strains Isolated from Ready‐to‐Eat Meat Products

The objective of the study was to answer the question of whether the ready‐to‐eat meat products can pose indirect hazard for consumer health serving as reservoir of Enterococcus strains harboring tetracyclines, aminoglycosides, and macrolides resistance genes. A total of 390 samples of ready‐to‐eat meat products were investigated. Enterococcus strains were found in 74.1% of the samples. A total of 302 strains were classified as: Enterococcus faecalis (48.7%), Enterococcus faecium (39.7%), Enterococcus casseliflavus (4.3%), Enterococcus durans (3.0%), Enterococcus hirae (2.6%), and other Enterococcus spp. (1.7%). A high percentage of isolates were resistant to streptomycin high level (45%) followed by erythromycin (42.7%), fosfomycin (27.2%), rifampicin (19.2%), tetracycline (36.4%), tigecycline (19.9%). The ant(6′)‐Ia gene was the most frequently found gene (79.6%). Among the other genes that encode aminoglycosides‐modifying enzymes, the highest portion of the strains had the aac(6′)‐Ie‐aph(2′′)‐Ia (18.5%) and aph(3′′)‐IIIa (16.6%), but resistance of isolates from food is also an effect of the presence of aph(2′′)‐Ib, aph(2′′)‐Ic, aph(2′′)‐Id genes. Resistance to tetracyclines was associated with the presence of tetM (43.7%), tetL (32.1%), tetK (14.6%), tetW (0.7%), and tetO (0.3%) genes. The ermB and ermA genes were found in 33.8% and 18.9% of isolates, respectively. Nearly half of the isolates contained a conjugative transposon of the Tn916/Tn1545 family. Enterococci are widely present in retail ready‐to‐eat meat products. Many isolated strains (including such species as E. casseliflavus, E. durans, E. hirae, and Enterococcus gallinarum) are antibiotic resistant and carry transferable resistance genes.     

Evaluation of Bubbling Vacuum Cooling for the Small-Size Cooked Pork

Vacuum cooling has notable advantages including fast cooling rate, cleanness, and high energy efficiency. However, the weight loss of food after being vacuum cooled was unsatisfactory, especially for meat products. Immersion vacuum cooling can significantly reduce the weight loss of food compared with traditional vacuum cooling procedures, but the cooling rate is unacceptable. To overcome this problem, here, a novel vacuum cooler, bubbling vacuum cooler, was designed and evaluated for the small-size cubic cooked pork with a side length of 1.5 cm from about 60 to 4 °C. Experimental results indicated that bubbling vacuum cooling can reduce the weight loss (about ??2.3%) of food compared to both vacuum cooling (about 12.4%) and immersion vacuum cooling (about 0.5%) (P?<?0.05). Further, bubbling vacuum cooling can cool the sample with a slightly more rapid cooling rate (0.10 °C/s) contrasted with immersion vacuum cooling (0.07 °C/s) (P?>?0.05). For the chromatism value of sample, no significant difference was found between immersion vacuum cooling and bubbling vacuum cooling (P?>?0.05). The textural property of sample cooled by bubbling vacuum cooling was close to (for hardness, elasticity, chewiness, and shear force, P?>?0.05) and better (for cohesiveness, P?<?0.05) than that of immersion vacuum cooling. Thus, our experiment demonstrated that cooked pork cooled by bubbling vacuum cooling has a lower weight loss rate and a more rapid cooling rate than that of immersion cooling.     

采用真空制冷技术冷冻鲜羊肉的研究

真空制冷技术是目前降温速度最快的一门制冷技术。它是一种理想的冷却和冻结方法,它能使蔬菜、果品和鲜花等农产品以及肉类,烘焙类食品在真空状态下快速,均匀冷却甚至冻结,使产品的质量,鲜度和营养价值得到保证。因此,该技术已在众多食品处理加工领域得到了广泛的应用,而且已经成为发达国家果蔬入市前必须进行的标准化作业之一。本文在介绍真空制冷的机理的同时以鲜羊肉为原料进行了真空冻结试验并对试验过程进行分析。