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.