AGGLUTINATION BEHAVIOR OF MESOPHILIC STARTER CULTURES AS A FUNCTION OF PROTEOLYSIS

Seven mesophilic starter cultures were grown separately in sterilized skim milk for 8 h at 25 degrees C. At the end of the incubation period , samples were analyzed for agglutination behavior by using microscopi c examination. Samples were also assayed for proteolytic activity by t he spectrophotometric o-phthaldialdehyde (OPA) and trinitrobenzenesulf onic acid (TNBS) methods. This experiment was replicated three times i n a randomized block design. Microscopic examination showed that some cultures existed as single cells, diplococci, or short chains; other c ultures tended to form long chains. Short-chain-forming cultures had h igh proteolytic activities, whereas long-chain-forming cultures had lo w proteolytic activities as measured by the TNBS and OPA methods. Prot eolysis measured by both methods ranked starter cultures in the same o rder (R-2 = 0.82). Low detectability values (obtained by dividing the standard error of the sample estimate for each method by its slope rat io) for OPA and TNBS methods indicated that the two assays do not diff er significantly (P > 0.05).