Heat survival of Clostridium difficile spores in ground meat during cooking process

Introduction: Clostridium difficile is a spore-forming pathogen considered as a major cause of enteric disease in humans, with faecal-oral route as the primary mode of transmission. However, recent studies have reported the occurrence of C. difficile in ground meats at retail stores, indicating that foods could be an additional source of infection in the community. Purpose: The objective of this study was to determine the resistance of C. difficile spores in contaminated ground meat during cooking process. Methods: Prior to testing, to obtain spores and to enhance heterogeneity, spores of two different strains were produced in two nutritious broths. C. difficile spores were experimentally inoculated in 45 g of ground meat (beef and pork) in order to obtain a final contamination of 4,500 ufc g-1. Six heating temperatures (70, 75, 80, 85, 90 and 95°C) were chosen. Samples were heating in a water bath with an integrated program for time-temperature. One sample without inoculum was used as control with a temperature probe placed inside. Once the desired temperature was research in the core of the sample, the heat treatment was prolonged for 10 min. Subsequently, all the samples were placed on the chilling room (4°C) before analyse. These experiments were conducted in duplicate with a spore enumeration in triplicate. Results: Heating contaminated ground meat at 70, 75 and 80°C for 10 min was not effective for C. difficile spores inhibition. However, 10 min of heat shock at 80°C was the only temperature that significantly reduced the number of countable colonies. Heat treatment at 85°C (or more) inhibits the germination of both of the strains tested. Significance: Ensure that ground meat, like burgers or sausages, is heated to more than 85°C would be an important measure to reduce the risk of C. difficile food transmission.ZooDif

Bacterial diversity and its evolution during storage of fresh beef from different origins under different atmosphere and temperature conditions

The purpose of this study was to evaluate the bacterial diversity and its evolution during storage of fresh beef, depending on its origin, packaging and storage temperature. Two batches of three vacuum packed striploins from United Kingdom and Belgium were obtained from a food wholesaler located in the Walloon Region. Fifteen days after slaughter, the striploins were sliced and individually kept under vacuum for 30 days: i) at −1 °C; ii) at +4 °C and iii) at −1 °C for 15 days and then at +4 °C for 15 days. The bacterial diversity was evaluated by metagenomic approach 15, 30 and 45 days after slaughter. Furthermore, each 15 days part of the vacuum packed striploin slices were repacked under modified atmosphere (70 % O2/30 % CO2), stored at +4 °C for 2 days and at +8 °C for 5 days, and then analyzed. Metagenomic analysis revealed a selection of the initial flora depending on atmosphere and temperature conditions. The development of Lactobacillus algidus was favored in samples preserved under vacuum at −1 °C, while a predominance of Lactococcus piscium was observed for samples stored at +4 °C. Moreover, storage under modified atmosphere favored the development of Leuconostoc gasicomitatum. These microorganisms have already been isolated from beef, but no study has evaluated their role in food conservation. The next step of this study will be to isolate and characterize strains of Lactobacillus algidus from meat and to assess their bioprotective potential.Conservation longue durée de la viande fraîche de bovins Blanc Bleu Belge : contraintes, évaluation et recommandations, Projet D31-127

Influence of temperature on conservability of chilled vacuum packed beef from different origins

peer reviewedaudience: researcher, professionalThe objective of this experiment was to study the conservability of chilled vacuum-packed meat depending on storage temperature (–1 °C vs. +4 °C) during the last third of their shelf life. Physicochemical parameters (pH and colour) and microbiological growth (total aerobic bacteria, lactic acid bacteria, Enterobacteriaceae, Pseudomonas spp. and Brochothrix thermosphacta) of Longissimus dorsi samples from different origins (United Kingdom and Ireland, Australia and Brazil) were measured at: i) 2/3 of their shelf life and ii) the end of their shelf life. Sample bacteria population growing on MRS was identified by API 50 CHL strips. Unlike Irish and British samples, pH of some Australian and Brazilian samples decreased during conservation. The colour of the samples remained stable and it did not seem to be influenced by temperature. All samples conserved at –1 °C presented a satisfactory microbiological quality at the end of their shelf life (British and Irish meat = 35~45 days; Australian meat = 140 days and Brazilian meat = 120 days). On Australian and Brazilian samples, temperature did not influence total aerobic bacteria growth, but conservation at +4 °C favoured lactic acid bacteria and Enterobacteriaceae growth. API 50 CHL strip identifications revealed the presence of bacteria like Lactobacillus brevis, Carnobacterium maltaromaticum and Lactobacillus fermentum, which occur naturally in fresh meat and are known for their bioprotective effect against other microorganisms. Further analyses are being carried out using molecular methods in order to study the initial bacteria population diversity and it evolution during storage.CONSBBB - Conservation longue durée de la viande fraîche de bovins Blanc-Bleu Belge : contraintes, évaluation et recommandation