HIGH-PRESSURE DESTRUCTION KINETICS OF SPOILAGE AND PATHOGENIC MICROORGANISMS IN MANGO JUICE

Abstract

ABSTRACT High-pressure (HP) destruction kinetics of three common spoilage microorganisms, Zygosaccharomyces bailii, Pichia membranaefaciens and Leuconostoc mesenteroides, and two pathogenic microorganisms, Escherichia coli O157:H7 and Listeria monocytogenes Scott A, were evaluated in processed mango juice at pressures ranging between 250 and 550 MPa and a hold time 0–60 min at 20–25C with genera-specific initial counts in the 106 to 108 cfu/mL range. Microbial destruction was evaluated based on (1) an initial kill which is due to a pressure pulse (pulse effect) and (2) a subsequent semi-logarithmic destruction during the pressure hold time. The decimal reduction times were genera-specific and decreased with an increase in pressure. Pressure sensitivity of microbial destruction rate was evaluated by a zP value. L. mesenteroides was found to be most resistant spoilage bacteria; yet its complete destruction was achieved by a 5-min treatment at 400 MPa. Pathogenic E. coli was the most resistant of all the bacterial strains tested. A six-log reduction in E. coli O157:H7 was observed at 400 MPa when treated for 10 min, while at 500 and 550 MPa, there were no survivors after the 1-min treatment. HP processes were established using a 6, 8 and 10D treatment based on E. coli O157:H7, and counts were monitored after treatment and during subsequent storage at 20, 12 and 4C for 28 days. Results showed that these processes were satisfactory because no growth of E. coli O157:H7 was observed during the entire storage time. PRACTICAL APPLICATIONS High-pressure (HP) processing is becoming a full commercial reality, and fruit-based HP processed products are appearing in the marketplace at a rapidly increasing pace. Successful use of HP processing relies on established processes based on scientifically evaluated destruction kinetics of spoilage and pathogenic microorganisms, and adequately verified process safety through microbial challenge studies. This study is based on such an approach for HP processing of mango juice demonstrating the technology to be feasible if the process is properly established. The study provides the scientific kinetic base line data for establishing HP process of mango juice, which is a well-recognized globally important exotic fruit crop.