The effects of ascorbic and cinnamic acid addition and different pasteurization parameters on the inactivation of alicyclobacillus acidoterrestris in apple juice
In this study, thermal inactivation parameters (z-, F- and D-values) of Alicyclobacillus acidoterrestris DSM 2498 strain, is an acidophilic, spore-forming microorganism that can survive typical pasteurization conditions, and may spoil fruit juices by producing off-flavour, were determined in clear apple juice and cloudy apple nectar. The effects of ascorbic acid and cinnamic acid at different consantrations (250 and 500 mg/L) on thermal inactivation of A. acidoterrestris were also investigated. When acid consantrations used in research was increased a decline in the z-value of A. acidoterrestris was observed. It was determined that decrease in z-values were greater in the clear apple juice than apple nectar. The reason of this difference is thought to be the protective effect of particulles in the apple nectar. D-values of A. acidoterrestris in clear apple juice were determined between D 93°C 7.3 min. and D 99°C 1.5 min, while in apple nectar this values were changed between D 93°C 7.7 min. and D 99°C 1.9 min. z-values obtained from D values were compared with z-values which were found experimentally before and almost close results were detected. In the last part of study, 10 6 CFU/mL of A. acidoterrestris spores were added into clear apple juice samples which prepared from commercial concentrated apple juice and pasteurized at 96°C according to the thermal death times determined before. Afterwards pasteurized samples stored at refrigerator temperature (+4°C) for 0, 5 and 10 days and at room temperature (-20°C) for 1, 2, and 3 months. At the end of the storage period microbiological analyzes of clear apple juice samples were carried out by using membran filtration method. No bacterial development was observed in samples stored in case of three analogous. This result showed that adequate lethality was obtained using F-values which determined before at different times for 96°C.