Starters as Finishers: Starter Properties Relevant to Cheese Ripening

Although the properties of starters relevant to cheese manufacture have been extensively studied and reviewed, there is little detailed information available on the contribution of starters to cheese ripening. Using extensive reference to in-vitro and in-situ studies on ripening which are currently being carried out in the authors' laboratories, this review concentrates on the roles of mesophilic starters in Cheddar cheese ripening and gives examples of data pertinent to the concepts under consideration. Particular attention is paid to the hydrolytic production of peptides, amino acids,. free fatty acids and glycerol through primary ripening processes and to the production of ammonia through secondary ripening reactions. The general lack of information on the significance of starters to secondary ripening reactions important. for the production of flavour compounds is highlighted. Enzymological, chemical and physiological factors involved in ripening are discussed, including concepts of starter strain variation in the activities, specificities, stabilities, concentrations and compartmentalisation of enzymes involved in ripening. The effects of the cheese environment on enzyme Junction and microbial physiology, including variations in the resistance of starter cells to lysis, are also discussed. The validity of using the parameter of colon),. forming units/g cheese (i.e. viable cell densities recovered) as a reference for comparison of levels of ripening enzyme levels is examined, as is the relationship between cell density, cell mass and enzyme concentrations.