Rapid enumeration of viable bacterial cells in processed soy products using an automated cell counting system

Abstract

A fluorescent filter method is an alternative culture-independent microbial test. The applicability of an automated cell counting system based on a fluorescent filter method was evaluated for processed soy products. To overcome the disadvantage of the filter method for colloidal and protein suspension samples such as soy milk and soy protein isolates, soy protein matrices were eliminated by isoelectric precipitation and bacterial cells in sample aliquots were enumerated using an automated cell counting system (Bioplorer). Bacterial counts with the Bioplorer method were well correlated with those obtained by the standard plate method. Coliform detection in soy products was possible within 7 h by this method, including 6 h required for culture enrichment, compared with more than 24 h required for confirmation by conventional plate methods. These results suggested that the Bioplorer method is a rapid and efficient method for the enumeration of viable bacterial cells in processed soy products.