摘要：Thermal treatment of milk is widely used to reduce milk contamination, while CO2 can be used to prevent bacterial growth and maintain milk quality during storage. These treatments applied before or during cheese manufacture could alter the metabolic activity of starter cultures. Changes in gene expression can be evaluated by differential display methods, so that effects on bacterial metabolic activity can be estimated by variation in transcription profiles. The aim of this study was to develop fluorescent RNA arbitrarily primed-polymerase chain reaction (RAP-PCR) as a method to evaluate the influence of milk CO2 acidification as well as rennet and salt concentrations on starter gene expression. Comparison with reference conditions showed that gene transcription was influenced according to the extent of thermal treatment as well as by CO2 acidification followed by different neutralization procedures. Thus, simple acid neutralization after CO2 acidification was not sufficient to regain the reference transcriptome profile. Starter gene transcription profiles showed important modifications following an increase in NaCl concentration or a decrease in rennet activity from standard conditions used in Cheddar cheese making. Increasing rennet activity results in small changes in the starter RNA profile. Fluorescent RAP-PCR is a promising method for obtaining a better understanding of gene expression profiles of mixed cultures during cheese making.
