CLASSIFICATION OF MICROBIAL DEFECTS IN MILK USING A DYNAMIC HEADSPACEGAS-CHROMATOGRAPH AND COMPUTER-AIDED DATA-PROCESSING .1. PRINCIPAL COMPONENT SIMILARITY ANALYSIS

There is a need for reliable objective tests for the detection of off- flavors of milk, some of which are caused by bacteriological growth. T he objective of the study was to distinguish abnormal from normal milk samples using a low-cost headspace gas chromatograph and principal co mponent similarity analysis. UHT-sterilized milk was inoculated with P seudomonas fragi, Pseudomonas fluorescens, Bacillus subtilis, Enteroba ctor aerogenes, Lactococcus Lactis, and a mixed culture (P. fragi:E. a erogenes:L. lactis = 1:1:1) to approximately 4.0 log(10) CFU mL(-1). T he samples were stored at 4 degrees C for 10 days for P. fragi and P. fluorescens and 30 degrees C for 24 h for the remaining bacteria. A ne w multiavariate analysis technique, principal component similarity ana lysis, was capable of distinguishing milk samples inoculated with P. f ragi, P. fluorescnes, L. lactis, E. aerogenes, and a mixed culture fro m uninoculated samples.