Starter Cultures

Abstract

In this chapter, the various types of starters, viz., mesophilic, thermophilic, defined- and mixed-strain, natural cultures, etc. and the analysis of these cultures by molecular approaches are considered. Then, the taxonomy and phylogeny of the important species of Lactococcus, Streptococcus, Leuconostoc, Lactobacillus and Enterococcus found in different cultures are analysed. Proteolysis and transport of the amino acids and peptides produced from it are important for the growth of starters in milk. The important pathways used by different starters to transport and metabolise arginine, lactose and citrate are treated. Respiration can be undertaken by lactococci but not by streptococci or lactobacilli and could be important in retaining activity when growing cultures in cheese plants. Some details are given on exopolysaccaharide production, the importance of plasmids and genome sequences. Major consideration is given to the importance of phage in inhibiting cultures, the sources of phage and how they may be controlled in cheese factories, and phage-resistance mechanisms. The production and role of bacteriocins in controlling spoilage and pathogens, which are common in lactic acid bacteria is considered. Finally, the production of starters in cheese plants is detailed and a summary of the use of frozen cultures which can be added directly to the milk in the cheese vat is given.