A modified agar medium for the screening of proteolytic activity of starter cultures for meat fermentation purposes.

An agar medium, used in the screening of proteolytic activity of dairy-related bacteria, was adapted for assessing the proteolytic capacity of bacteria which were of possible use in meat fermentations. Freeze dried myofibrils, extracted from pork muscle, were incorporated in the medium. The agar plates were inoculated with 20 microl of overnight cultures of different starter strains, and incubated at 30 degrees C for 48 h. After incubation, proteolytic bacteria produced clear zones. Coomassie brilliant blue stain was employed to facilitate the detection of these zones. Proteolytic activity was confirmed in an enzymatic test.

Pathogenic micro-organisms in slaughterhouse sludge--a survey.

During slaughtering of animals and subsequent meat processing the process water used becomes polluted with organic matter of animal origin (i.e. protein and fat). This organic sludge is, in principle, a product suitable for animal feeding. To investigate the microbiological contamination level of sludge, raw sludge was collected at pig (n = 8) and poultry (n = 5) slaughterhouses. Both flocculated and aerobically activated sludge was monitored. Slaughterhouse sludge was heavily contaminated with Enterobacteriaceae (6.3-10.0 in log10 N/gram dry matter) and enterococci (4.6-7.9). Clostridia were present in sludge at a level of 3.1-5.8 (in log10 N/g DM). Salmonella was present in the sludge from all slaughterhouses examined. Yersinia enterocolitica serotypes O:3 and O:9 were found in sludge from seven out of thirteen slaughterhouses. The prevalence of Campylobacter jejuni/coli was higher in flocculated poultry sludge than in both flocculated pig sludge and aerobically activated pig sludge. Obviously, decontamination of the sludge is mandatory when it is to be applied as a feed constituent, to prevent bacterial cycles from occurring in livestock, as well as the spread of human pathogenic zoonoses like campylobacter, salmonella and yersinia, to minimize loss of protein quality by the microbial breakdown of amino acids and the formation of possible toxic metabolites in sludge during storage.

Utilization of fermented flocculated poultry sludge as a feed constituent for pigs.

Flocculated poultry sludge was mixed with 3% molasses and was flow-therm pasteurized for 5 min at a core temperature of 95 C. The sludge was subsequently cooled to between 20 and 25 C and fermented with Lactobacillus plantarum as starter culture. Three groups of eight 8- to 10-wk-old, individually housed fattening pigs (Hypor) were fed according to a fixed scheme correlated with age. One control group received a restricted ration of commercial compound feed (Group A). The other control group was provided "nearly ad libitum" access to the same commercial compound feed (Group C). The experimental group received the same amount of commercial compound feed as Group A, but the diet was supplemented with fermented sludge, at an inclusion rate of 19 to 28% of the total ration (DM basis). The pigs fed the sludge-containing diet and those receiving the compound pig feed "nearly ad libitum" showed comparable growth results. It was concluded that the net energy (NEpig) level of .68 g DM of sludge was comparable to the NEpig level of 1 g compound pig feed (88% DM). A decrease in colony counts of Enterobacteriaceae in the intestinal tract of the pigs, was regarded as positive, as it might lower the risk of disturbance of the gut flora by enteropathogenic bacteria such as Escherichia coli and Salmonella. No adverse effects on health and performance were observed as a result of the feeding of pasteurized and subsequently fermented flocculated poultry sludge to fattening pigs. It is concluded that this sludge can serve as a valuable feed constituent as long as it is processed properly.

Proteolysis and amino acid breakdown of heated and irradiated poultry byproducts and muscle tissue.

As a result of intensification and centralization of poultry slaughtering, the amount of slaughter byproducts produced at a single location is increasing. These byproducts are rich in protein, fat, and vitamins and, therefore, constitute a potentially useful raw material for use as animal feed. To maintain the nutritive value of these byproducts they should be processed to minimize or eliminate degenerative changes that reduce the feed value of the product. In this paper amino acid breakdown in slaughter-fresh poultry viscera, heads, and breast meat is studied as a model. Initial amino acid breakdown in viscera was observed (also when bacterial growth was excluded by gamma-irradiation), which resulted in high levels of total volatile N and cadaverine. Putrescine was produced only in viscera after bacterial proliferation. In heads and breast meat, no production of metabolites of amino acid degradation was observed as a result of initial enzymatic activity. It is concluded that during preservation of poultry byproducts not only bacterial proliferation, but also enzymatic breakdown of amino acids, must be prevented.