Temperatures and storage conditions in domestic refrigerators - Slovenian scenario

Changes in Protein Levels during the Storage and Warming of Breast Milk in a Domestic Environment

Background/Objectives: Storage and warming can impact the protein concentration of breast milk (BM). This study aimed to explore the effects of routine BM handling, from storage to warming, on BM protein concentration. Methods: Forty BM samples were collected from 40 mothers with full-term infants. Fresh BM samples were analyzed within 24 h of expression as a baseline. Additional samples were stored in a refrigerator for up to 4 days and in either a freezer compartment of a refrigerator with a separate door (refrigerator freezers) or a deep freezer for up to 6 months. We compared four warming techniques: rapid thawing in water at 25 °C and 37 °C immediately after freezer removal, and slow thawing in a refrigerator for 12 h, followed by warming in water at 25 °C and 37 °C. The protein concentration was measured using the Lowry method. Results: No significant decrease in BM protein concentration was observed across all storage conditions compared to baseline. BM with a higher protein content benefited more from storage in deep freezers than in refrigerator freezers. Thawing immediately after removal from the freezer at 25 °C preserved significantly higher total protein levels compared to alternative heating techniques. Conclusions: Our findings support the recommendation for mothers to store BM in either type of freezer for up to 6 months. Our results suggest that rapid thawing at 25 °C is the most effective method for preserving protein levels compared to other thawing techniques used in our study.

A Microbiological and Sensory Evaluation of Modified Atmosphere-Packed (MAP) Chicken at Use-By Date and Beyond

Consumers are responsible for a large proportion of food waste, and food that has reached its use-by or best-before date is often discarded, even if edible. In this study on fresh chicken, the suitability of use-by dates currently used in the EU was evaluated by using microbial and sensory analyses. This was carried out by analyzing bacterial populations of chicken breast fillets (M. pectoralis major) at three different time points (use-by date, 2 days past use-by date, 4 days past use-by date) and two different storage temperatures (4 °C, 8 °C). A discrimination triangle test was performed to check for sensory differences between chicken breast fillets cooked at the three selected time points for both storage temperatures. A consumer preference test was also performed for chicken breast fillets that had been stored at the highest recommended temperature (4 °C) and after being cooked at the three time points. Changes in populations of total aerobic count (TAC), Enterobacteriaceae (EB), and lactic acid bacteria (LAB) were recorded over time. Despite large differences in bacterial counts at the selected time points, with TAC populations of approximately 6.5 and 8.0 log CFU/g at use-by date and four days after use-by date, respectively, storage for two or four extra days had no significant effect on the sensory parameters of cooked chicken compared with chicken consumed at its use-by date. Since the TAC populations were close to or above levels that are associated with spoilage, more work is needed to explore if shelf life can be extended.

Performance assessment of a refrigeration system with an integrated condenser under different environmental conditions

This paper presents a workable vapour compression system (VCS) for evaluating the performance of a refrigeration system with an integrated condenser that uses a long-term alternative refrigerant to halocarbon as a heat transfer medium (R600a). India's refrigeration system uses halocarbon refrigerants due to their excellent thermophysical and thermodynamic properties. Greenhouse gas emissions from halocarbon refrigerants and fossil fuel combustion contribute to global warming that engenders climate change and the deterioration of the ecosystem. The halocarbon refrigerant was discontinued based on high global warming potential. The system was investigated under various ambient temperatures of 16, 20, 24, and 28 °C (oC). The performance of the VCS was analyzed using the parameters of coefficient performance, compressor work, and pull-down time (PDT). The experimental result shows that the vapour compression system obtained its best PDT, enhanced coefficient of performance, and energy reduction when the ambient temperature was 20 °C.

Strain and serovar variants of Salmonella enterica exhibit diverse tolerance to food chain-related stress

Non-Typhoidal Salmonella (NTS) continues to be a leading cause of foodborne illness worldwide. Food manufacturers implement hurdle technology by combining more than one approach to control food safety and quality, including preservatives such as organic acids, refrigeration, and heating. We assessed the variation in survival in stresses of genotypically diverse isolates of Salmonella enterica to identify genotypes with potential elevated risk to sub-optimal processing or cooking. Sub-lethal heat treatment, survival in desiccated conditions and growth in the presence of NaCl or organic acids were investigated. S. Gallinarum strain 287/91 was most sensitive to all stress conditions. While none of the strains replicated in a food matrix at 4 °C, S. Infantis strain S1326/28 retained the greatest viability, and six strains exhibited a significantly reduced viability. A S. Kedougou strain exhibited the greatest resistance to incubation at 60 °C in a food matrix that was significantly greater than S. Typhimurium U288, S Heidelberg, S. Kentucky, S. Schwarzengrund and S. Gallinarum strains. Two isolates of monophasic S. Typhimurium, S04698-09 and B54Col9 exhibited the greatest tolerance to desiccation that was significantly more than for the S. Kentucky and S. Typhimurium U288 strains. In general, the presence of 12 mM acetic acid or 14 mM citric acid resulted in a similar pattern of decreased growth in broth, but this was not observed for S. Enteritidis, and S. Typhimurium strains ST4/74 and U288 S01960-05. Acetic acid had a moderately greater effect on growth despite the lower concentration tested. A similar pattern of decreased growth was observed in the presence of 6% NaCl, with the notable exception that S. Typhimurium strain U288 S01960-05 exhibited enhanced growth in elevated NaCl concentrations.

Effects of chlorine and peroxyacetic acid wash treatments on growth kinetics of Salmonella in fresh-cut lettuce

Fresh-cut produces are often consumed uncooked, thus proper sanitation is essential for preventing cross contamination. The reduction and subsequent growth of Salmonella enterica sv Thompson were studied in pre-cut iceberg lettuce washed with simulated wash water (SWW), sodium hypochlorite (SH, free chlorine 25 mg/L), and peroxyacetic acid (PAA, 80 mg/L) and stored for 9 days under modified atmosphere at 9, 13, and 18 °C. Differences in reduction between SH and PAA were non-existent. Overall, visual quality, dehydration, leaf edge and superficial browning and aroma during storage at 9 °C were similar among treatments, but negative effects increased with temperature. These results demonstrated that PAA can be used as an effective alternative to chlorine for the disinfection of Salmonella spp. in fresh-cut lettuce. The growth of Salmonella enterica sv Thompson was successfully described with the Baranyi and Roberts growth model in the studied storage temperature range, and after treatment with SWW, chlorine, and PAA. Subsequently, predictive secondary models were used to describe the relationship between growth rates and temperature based on the models' family described by Bělehrádek. Interestingly, the exposure to disinfectants biased growth kinetics of Salmonella during storage. Below 12 °C, growth rates in lettuce treated with disinfectant (0.010-0.011 log CFU/h at 9 °C) were lower than those in lettuce washed with water (0.016 log CFU/h at 9 °C); whereas at higher temperatures, the effect was the opposite. Thus, in this case, the growth rate values registered at 18 °C for lettuce treated with disinfectant were 0.048-0.054 log CFU/h compared to a value of 0.038 log CFU/h for lettuce treated with only water. The data and models developed in this study will be crucial to describing the wash-related dynamics of Salmonella in a risk assessment framework applied to fresh-cut produce, providing more complete and accurate risk estimates.

Consumer attitudes and perceptions towards chilled ready-to-eat foods: a multi-national study

Understanding consumers' behavior and their handling of high-risk foods at home is essential for reducing the number of foodborne illnesses. This study shows the results of a cross-national analysis of consumers' perception from nine countries, and the identification of customers' clusters and its characteristics in order to understand customers' behavior, and to build safe chilled ready-to-eat (RTE) foods prevention strategies. The cluster analysis resulted in two clusters: (1) "Precautious consumers" characterized by the orientation towards pre-packed RTE foods, with consumers mainly coming from Bosnia and Herzegovina, India, Poland, Portugal, Spain, and Turkey. Their attitudes and self-reported practices may be categorized as less risky in terms of food-borne illnesses connected with the consumption of RTE foods; (2) "Unconcerned consumers" preferred cutting and slicing RTE foods freshly at the point of purchase, usually sold at the delicatessen department in a supermarket or at open markets. Those consumers mostly came from Croatia, Serbia and Slovenia and their attitudes and self-reported practices were riskier. These results allow a better understating of what characterizes consumers of RTE foods in different countries.

Survey of Domestic Refrigerator Storage Temperatures in Poland for Use as a QMRA Tool for Exposure Assessment

In the framework of Quantitative Microbiological Risk Assessment, the estimation of the ingested dose of a hazard by the consumer is of paramount importance. This may be calculated by means of predictive modeling of growth/inactivation of the pathogen studied. For products that spend the majority of their shelf life in the domestic refrigerator, storage temperature will significantly impact the microbial population dynamics. To describe the variability of domestic storage temperatures in Poland, a survey including 77 participants, was carried out in Lodz, Poland. Participants were provided with temperature data loggers, which measured their refrigerator temperature for 24 h in 5-min intervals. The temperature-time profiles were used to calculate the mean working temperature, standard deviation, minimum and maximum values, and the data were statistically analyzed to find the best fitting probability distribution using R programming language. Out of the tested refrigerators, 49.35% had a mean working temperature of over 5 °C and 3.9% exceeded 10 °C. Distribution fitting scenarios were tested for goodness of fit, and the final selected distribution was a truncated normal distribution. This study can prove useful in Monte Carlo simulation analysis for stochastic quantitative food risk assessment in Poland.

Deterministic Approach and Monte Carlo Simulation to Predict Listeria monocytogenes Time to Grow on Refrigerated Ham: A Study Supporting Risk-based Decisions for Consumers' Health

This study assessed the growth of Listeria monocytogenes in ready-to-eat (RTE) ham during storage under conditions simulating domestic practices with the intention to offer support in the elaboration of food safety policies that should better protect consumers against food poisoning at home. RTE ham, artificially contaminated at either medium (10²-10³ CFU/g) or high (10⁴-10⁵ CFU/g) concentration, was stored at both isothermal (4℃ in a refrigerator able to maintain a relatively constant temperature and 5℃ and 7℃ in a refrigerator with fluctuating temperature) and dynamic (5℃ and 7℃ with intermittent exposure to ambient temperature, e.g. 25℃) conditions. Under isothermal conditions, the increasing storage temperature determined a significantly increased (p < 0.05) capacity of L. monocytogenes to grow. The kinetic growth parameters were derived by fitting the Baranyi and Roberts model to the experimental data and, based on the maximum specific growth rates, it was estimated the temperature dependence of L. monocytogenes growth in RTE ham. At medium contamination level, sanitary risk time calculation revealed that, unlike storage at 5℃ and 7℃, storage at 4℃ of the RTE ham extends the time period during which the product is safe for consumption by ∼40 and 52%, respectively. However, the real temperature fluctuations included in the Monte Carlo simulations at low L. monocytogenes counts (1, 5 and 10 CFU/g) have shortened the safety margins. Stochastic models also proved to be useful tools for describing the pathogen's behavior when refrigeration of the RTE ham alternates with periods of ham being kept at room temperature, considered dynamic conditions of growth.

Review of pork and pork products as a source for transmission of methicillin-resistant Staphylococcus aureus

Methicillin-resistant Staphylococcus aureus (MRSA) is an opportunistic bacterium that can cause infection in animals and humans. Recently, MRSA from food-producing or farm animals has been identified as livestock-associated MRSA (LA-MRSA). The spread of LA-MRSA is particularly found in pork and pork products because LA-MRSA has been widely known to infect pigs. The most common type of LA-MRSA identified in pork and pork products is the clonal complex LA-MRSA 398 (LA-MRSA CC398). The MRSA strains on the surface of pork carcasses can be spread during the handling and processing of pork and pork products through human hands, cutting tools, and any surface that comes into direct contact with pork. Food infection is the main risk of MRSA in pork and pork products consumed by humans. Antibiotics to treat food infection cases due to MRSA infection include vancomycin and tigecycline. The spread of MRSA in pork and pork products is preventable by appropriately cooking and cooling the pork and pork products at temperatures above 60°C and below 5°C, respectively. It is also necessary to take other preventive measures, such as having a clean meat processing area and disinfecting the equipment used for processing pork and pork products. This review aimed to explain epidemiology, transmission, risk factors, diagnosis, public health consequences, treatment of food poisoning, and preventing the spread of MRSA in pork and pork products.

A Multimethod Study on Kitchen Hygiene, Consumer Knowledge and Food Handling Practices at Home

The aim of the study was to identify consumers’ food safety knowledge, practices, and hygiene status in the observed home kitchens. The results provide the starting point for evaluating progress or regression in this area compared to the past statewide study. Food safety knowledge was analyzed among 380 consumers with an online questionnaire. Additionally, 16 consumers were observed during their preparation of specified foods. The hygiene conditions in the kitchens were microbiologically examined using contact agar plates, while the cleaning adequacy was determined by measuring the ATP bioluminescence. A lack of knowledge on certain topics regarding food safety was established; the consumers aged from 36 to 55 in general and women demonstrated the highest level of knowledge. In some cases, the observed consumers did not take proper action when preparing the food. Increased total bacteria, coliform bacteria, and Escherichia coli counts were detected in 12.7% of the consumers’ kitchens observed here. Eighty-three (74.1%) out of 112 surfaces examined with either hygiene test sheets or ATP swabs met the standards and were adequately or acceptably cleaned. The kitchen surfaces exceeded the recommended limits for 25% of consumers. Statistical differences in RLU and TCC levels on surfaces between older and younger consumers were not observed, although all (25%) inadequately cleaned kitchens belonged to older consumers. The greatest emphasis has to be put on the cleaning of home kitchens and personal hygiene. Even though consumers have some knowledge on food safety, they often fail to put that knowledge into daily practice.

Comparison of Effects of Storage at Different Temperatures in a Refrigerator, Upright Freezer on Top of Refrigerator, and Deep Freezer on the Immunoglobulin A Concentration and Lysozyme Activity of Human Milk

This study aimed to investigate the effects of storing expressed human milk (HM) at different domestic storage temperatures on the secretory immunoglobulin A (SIgA) concentration and lysozyme activity. Forty mothers of full-term infants aged one to six months provided milk samples. The fresh samples were examined within 24 h of expression, and the other samples were stored in a refrigerator for four days or in two types of freezers for six months. The SIgA concentrations and lysozyme activity in the milk samples were studied using enzyme-linked immunosorbent assay (ELISA) kits and fluorometric lysozyme activity assay kits, respectively. The pairwise comparisons of the SIgA concentration and lysozyme activity were carried out using one-way analysis of variance with Dunnett T3 or Kruskal-Wallis tests with Bonferroni correction, depending on the data distribution. The mean temperatures of the refrigerator, upright freezer on top of the refrigerator, and deep freezer (chest freezer) were 2.0, -16.7, and -22.3 °C, respectively. Our study results highlight that the SIgA concentration and lysozyme activity of HM stored in the refrigerator for four days and in freezers for six months were significantly lower than those of fresh HM (p < 0.001). During the first six months of storage in both types of freezers, the SIgA levels were stable, whereas the lysozyme activity significantly decreased (p < 0.001). HM stored in the deep freezer had a higher SIgA concentration and lysozyme activity than HM stored in the upright freezer on top of the refrigerator. Our data support the superiority of fresh human milk over stored HM. If HM is to be stored, then storage in a deep freezer is potentially a more effective method for the preservation of SIgA concentrations and lysozyme activity than storage by refrigeration for four days or in an upright freezer on top of a refrigerator for six months.

Food Safety Knowledge and Practices of Pregnant Women and Postpartum Mothers in Slovenia

Food safety during pregnancy and postpartum is important for preventing foodborne diseases, while pregnant women are considered vulnerable due to their immunomodulatory condition. The current study aimed to investigate the self-reported food safety knowledge and practices of pregnant women and postpartum mothers in Slovenia using an online questionnaire and to compare the results with nonpregnant women as a control group. The study was conducted with 426 women, of whom 145 were pregnant, 191 were not pregnant, and 90 were postpartum. The online questionnaire consisted of questions related to food safety risk perception, hand hygiene, food purchase, food storage, food preparation and handling of infant formula and breast milk. The results showed that women generally have basic knowledge of proper food handling and are aware of food safety, but some specific gaps were identified in food handling at home, especially concerning microbiological risks. However, the results showed that pregnant women performed better than the postpartum group, and both groups performed significantly better than the nonpregnant group. The media was most frequently cited as a source of food safety information, especially by the pregnant group. Trained health workers should also inform women on how to ensure food safety in the home environment.