Testes de desafio em morcelas de arroz, morcelas de arroz da Beira e de Monchique

Abstract

Morcela is a portuguese blood sausage made with pork meat, fat and blood, rice seasoned with cumin, garlic, onions, cloves, vinegar, red wine and salt. It is usually pasteurized and often smoked and dried for a short period of time. It has high gastronomic and economic value in Portuguese rural regions Nowadays it’s important to deliver safe products due to legal aspects, without losing its quality. It’s then necessary to identify the factors that contribute to that aspect. Scientific knowledge gathered throughout the years has led to the worrying of foodborne diseases caused by specific bacteria leading scientific investigation to understand the behavior of foodborne pathogenic bacteria responsible for food toxinfections, especially in ready-to-eat type foods. The aim of this work was to evaluate the behavior of relevant foodborne and spoilage microbiota in Beira rice morcela (MB) and Monchique rice morcela (MM) in relation to the industrial processing and storage. In order to understand the behavior of foodborne pathogens (Listeria monocytogenes, Salmonella spp., Escherichia coli O157:H7, Bacillus cereus, Clostridium perfringens and Clostridium sporogenes) in Beira rice morcela paste, two trials were designed. In the first it was studied the effect of thermal process (72°C in the thermal center), cooling rate (quick and slow) and storage temperature (4 and 15°C) in the behavior Listeria monocytogenes, Salmonella spp., E.coli O157:H7 and Bacillus cereus, previously grown in normal media and under designated stress conditions (modified media supplemented with 1% NaCl, 0,75 mg/L NaNO2 and 5% of glycerol). With Bacillus cereus, Clostridium perfringens and Clostridium sporogenes it was also studied the effect of high and low inoculum level. Enterococcus faecium was used in the same conditions to validate the thermal processing efficiency. The second trial, design as complementary to the first, it was evaluated the industrial process and recovery ability of Listeria monocytogenes, Salmonella spp. and E. coli O157:H7 survive and outgrown in MM produced under the same conditions as it is in a local industry. Generally, it was observed that the heat treatment used in the industry is enough to ensure a reduction of 5D in the population of non sporulated pathogens. The designated slow cooling rate (the more similar to that achieved in the industry) revealed to be more effective in the reduction of these pathogens. The sporulated pathogens tested revealed to have a poor ability to outgrowth in the morcela, probably due to the biological state of the spores when the heat treatment was applied. The spoilage microbiota of MM packaged in MAP60:40 was monitored during 49 days of storage in refrigeration temperature and under temperature abuse (15°C). LAB was the main v specific spoilage microorganism enumerated. Enterococcus spp. and coagulase negative Staphylococcus was also involved. Gram negative bacteria (Enterobacteriaceae and Pseudomonas spp.) associated to spoilage due to its catabolic activities and sensory negative impact decrease during the storage. Aiming to establishment the risk of growth of relevant foodborne pathogens in MB – a ready-to-eat product – a microbial challenge test was designed challenging of Listeria monocytogenes, Salmonella spp., E. coli O157:H7, Bacillus cereus and Clostridium perfringens. The challenge test was performed in morcela slices packaged (MAP60:40, vacuum and aerobic) and stored at refrigeration temperature (4°C) and under conditions of temperature abuse (15°C) during 35 days. Independently of the storage conditions the outgrowth of Listeria monocytogenes occurred in the early period of storage, resulting in a hazardous product. The hazard associated to the other pathogens challenged was generally only significative if the samples were stored under temperature abuse. The spoilage microbiota of slices of Monchique morcela was very abundant and composed mainly by LAB, but also by Enterobacteriaceae and Pseudomonas spp., that have important negative impact in the sensory characteristics of the product. The aerobic package was always the worst solution. Between vacuum and MAP, only slightly differences were observed Briefly, heat treated blood sausages are products potentially hazardous if highly accurate criteria are not applied to the control of processing and storage. The results of the present work demonstrate that the operations used by the industry, associated to a correct storage results in safe products for the consumer.