Bacterial starter cultures, aging and fermentation effects on some characteristics of fermented beef sausages

Beef sausage mixes were inoculated with either Pediococcus acidilactici, Staphylococcus xylosus with P. acidilactici, or Staphylococcus carnosus with P. acidilactici, subdivided and then held for 0, 24, 48 or 72 hr at 8--10°C prior to fermentation. After holding (pre-fermentation), the mixes were fermented for 16 hr using a stepwise temperature program ending at 41°C. Moisture, protein and fat contents of all sausage mixes did not differ due to holding effects over all starter cultures. Prefermentation had no effect on NPN (nonprotein nitrogen as DeltaNPN) content among all cultures. After fermentation, however, sausages held 72 hr and inoculated with S. carnosus had higher NPN contents compared to P. acidilactici alone (p < 0.05) and S. xylosus (p < 0.10). Total amino acid concentrations after fermentation differed in the same way as DeltaNPN. The pH of mixes followed the same pattern for all mixes, declining (p < 0.05) from approximately 5.8 to pH 5.2--5.3 at 72 hr prefermentation and to 4.4--4.5 after fermentation. Total acidity followed an inverse relationship to pH, significantly increasing during fermentation although there was no effect due to type of starter culture. Final acidity ranged from 1.78--1.83% (as lactic acid).; Proteolytic activity of Pediococcus acidilactici, Lactobacillus sake, Lactobacillus curvatus, Streptomyces griseus, Staphylococcus xylosus and Staphylococcus carnosus in beef protein extracts incubated at 30°C for 0--96 hr showed that L. sake had greater (p < 0.05) proteolytic activity than any other culture. From highest to lowest activity, the other cultures ranked as follows: L. curvatus > S. carnosus > S. griseus > P. acidilactici > S. xylosus. All inoculated extracts showed a pH decline from 6.0 initially to 3.76--4.31 at 96 hr. L. sake and S. xylosus had bacterial counts less than their initial inoculation level after 96 hr which was likely related to their ability to greatly reduce pH of the extracts. The results provide evidence that several commercially available starter cultures for meat fermentation do possess significant proteolytic activity when tested using beef protein extracts.; Fermented beef sausages inoculated with L. curvatus, L. sake, P. acidilactici or S. griseus, held for 72-hr at 25°C, fermented to 41°C, dried and then heated to 60°C exhibited a pH decline during prefermentation and subsequent fermentation followed by a slight pH increase after drying. Sausages inoculated with S. griseus had higher (p < 0.05) pH values than those fermented with other cultures. Increases (p < 0.05) in the NPN fraction were found at various stages of processing, but type of starter culture had no major effect on NPN content. Concentrations of most free amino acids increased (p < 0.05) during fermentation and drying and culture type was found to affect the concentration of some individual free amino acids. Based on SDS-PAGE analyses of sarcoplasmic and myofibrillar protein fractions after fermentation and drying, myosin heavy and light chains, actin and troponin were degraded during processing. No observable effect of starter cultures on the SDS-PAGE protein patterns was detected. Volatile components of seasonings comprised the largest group of compounds present in GC-MS headspace analysis. The predominant volatile components appeared to result from carbohydrate metabolism, proteolysis and lipid oxidation after fermentation and drying.