STUDY OF THE EFFECT OF THERMAL PASTEURIZATION AND HIGH HYDROSTATIC PRESSURE IN THE VIABILITY OF ZYGOSACCHAROMYCES ROUXII POPULATION IN CONCENTRATED GRAPE JUICES

ROJO MARÍA CECILIA; CRISTIANI MIRNA; SZERMAN N; LERENA MARÍA CECILIA; VARGAS TRINIDAD ANDREA SUSANA; MERCADO LAURA ANALÍA; COMBINA MARIANA

San Carlos de Bariloche

Congreso; 34 International Specialized Symposium on Yeasts (ISSY); 2018

The process of juice concentration involves the elimination of water until aconcentration of sugars and osmotic pressure capable of inhibiting the microbialdevelopment is reached. However, these products are not free of microbiologicalspoilage problems, being Zygosaccharomyces rouxii the most frequent spoilagemicroorganism. Many efforts have been done in the industry to avoid yeast spoilageusing a non-chemical approach, where pasteurization and high hydrostatic pressure(HHP) could be suitable technologies. The aim of this work was to find the conditions ofthermal pasteurization and HHP necessary to reach the inactivation of Z. rouxii and theextension of the shelf-life of concentrated grape juice. Different Z. rouxii wereinoculated in concentrated grape juice at 107 CFU/g. The samples were submitted topasteurization using different temperature (70, 75, 80 and 85 °C) and times (5, 10, 20,30, 45, 60, 75 and 85 seconds); and to HHP using different pressures (300, 400, 500and 600 MPa) and times (2, 3 and 5 minutes). Pasteurization at 70 °C was not lethal forZ. rouxii in any of the times evaluated, while a reduction of 7 logarithms was obtainedat 75 and 80°C for 90 seconds, and at 85°C for 5 seconds. The application of HHP at300 MPa was not lethal for Z. rouxii in none of the evaluated conditions. A significantreduction in viable populations of Z. rouxii was observed at 400 MPa, although a slowlyrecovery of the cells was observed, resulting in spoilage after 14 days of storage at 28°C. Treatments with pressures over 500 MPa resulted in a significant reduction in thepopulation and an extension of the shelf life of the stored product was observed. Ourstudies suggest that both technologies; HHP and pasteurization; could be applied toincrease the microbial stability of concentrated grape juices.