Inactivation of Saccharomyces cerevisiae and Lactobacillus plantarum in orange juice using ultra high-pressure homogenisation

Yeasts and lactic acid bacteria are the usual contaminants in orange juice and responsible for decreasing the shelf life of the product. Ultra high-pressure homogenisation has been shown to be an alternative to the traditional thermal pasteurisation of pumpable foods. The product was pumped through a homogeniser valve at 100 MPa, 150 MPa, 200 MPa, 250 MPa and 300 MPa using two synchronized overlapped intensifiers at a flow rate of approximately 270 mL/min. The inlet temperature was kept at 10 degrees C, pH at 4.1 and soluble solids at 10.0 degrees Bx. After processing, the product was immediately cooled to 4 degrees C and the microbiological count was determined. The study showed that Lactobacillus plantarum and Saccharomyces cerevisiae are sensible to ultra high-pressure homogenisation treatment. The results indicated that pressures higher than 250 MPa were able to completely destroy initial loads of 1.2 x 107 UFC/mL of L. plantarum and 2.9 x 105 UFC/mL of S. cerevisiae in orange juice, making this technology a promising way to nonthermally process orange juices. (C) 2007 Elsevier Ltd. All rights reserved.