Effects of the high pressure of homogenization on some spoiling micro-organisms, representative of fruit juice microflora, inoculated in saline solution.

AIMS: This study was aimed to investigate the effects of a high-pressure homogenization (HPH) treatment on some micro-organisms, involved in the spoilage of fruit juices. METHODS AND
RESULTS: Lactobacillus plantarum, Lactobacillus brevis, Bacillus coagulans cells, Saccharomyces bayanus, Pichia membranaefaciens and Rhodotorula bacarum were separately inoculated in a saline solution (0.9% NaCl); the initial inoculum was ca. 5 log CFU ml(-1). Then, the samples were processed through a homogenizer at 10-150 MPa for 1, 2 or 3 times. Yeasts were completely inactivated at 50-110 MPa with a single pass treatment, while lactic acid bacteria counts were reduced to approximately 1 log CFU ml(-1) after a three-steps HPH processing.
CONCLUSIONS: Yeasts were the most sensitive micro-organisms, followed by B. coagulans. On the other hand, lactic acid bacteria appeared resistant to HPH. SIGNIFICANCE AND IMPACT OF THE STUDY: The results of this study provided some useful information on the susceptibility of microflora of juices to homogenization; moreover, they suggested that HPH could be used successfully to inactivate yeasts.