Irradiation of raw portuguese sausages and meat based ready-to-eat meals

Portuguese 'chorizo', traditionally processed, contains a high load of a mixed microbial population, including some food-borne pathogenic bacteria. However, commercially manufactured 'chorizo' undergoes a technological process based on hot smoking, which eliminates most microbial flora present. In such conditions it is not justifiable to use irradiation. On the contrary, home-made 'chorizo' is smoked at low temperatures and produced on a small scale in small premises spread over the country. In this case, irradiation is justifiable and economically feasible if the chorizo is collectively sent to irradiation centres for treatment. The use of irradiated meals is justified for preservation of their natural organoleptic properties when full botulinum cooking is not affordable. In irradiated 'chorizo', a total aerobic count was dominant, faecal streptococci were low in number while coliforms, E. coli and Staphylococcus aureus were absent from the control samples. Faecal streptococci showed more sensitivity to irradiation than aerobic microflora which can be explained by the presence of endospore-forming bacteria. Faecal streptococci survived an irradiation dose of 2 kGy dose but not 4 kGy. An 8 kGy dose was not sufficient to destroy all the spores of sulphite-reducing clostridia present. The D10 determined for faecal streptococci was 1.25 kGy. In ready-to-eat meals, the microbial contamination of control dishes of 'stewed veal with onions and carrots' cooked in the laboratory was lower than in samples of commercially refrigerated meat based meals. The reduction of microbial flora was found to be proportional to irradiation dose. A reduction of 2 logs in the total aerobic microflora was achieved with a 4 kGy dose. Approximately 107 vegetative and viable spores of Clostridium sporogenes per gram were suspended in 'stewed veal with onions and carrots' meal and irradiated at -30 deg. C. The irradiation D10 value for vegetative and spore formers was 4.67 kGy. The D10 value for viable spores of the same microorganism was 5.58 kGy. (author)