Survival kinetics of Alicyclobacillus acidoterrestris spores in thermally processed pineapple-mango blend juice

The presence of Alicyclobacillus acidoterrestris (AAT) spores in pineapple and mango juices has been reported in the industry. Thermal resistance of AAT spores to pasteurisation treatment poses a serious threat to the tropical juice industry. This study investigates the influence of formulation (pineapple, mango, 70% mango-30% pineapple and 50% mango-50% pineapple), total soluble solid (10 - 15°Bx), and pH (3.58-3.70) on AAT (ATCC®49025TM) spores’ survivor after processing at 85 - 95°C. As the temperature rises to 85℃ and 90℃, 1 log reduction of the spores was observed after treatment for 5 mins. Spore concentration for each juice showed a sharp decrease when the temperature reached 95℃, which resulted in a significant reduction (P<0.05) of 3 to 4 log CFU/mL. Significant reductions in pH and total soluble solids of juice samples were noticed in all formulations and D-values of AAT spores heated at 85°C (14.1 - 16.6 mins) were significantly reduced by double when heated at 90°C (5.8 - 6.7 mins) (P<0.05). Weibull’s model shows a good fit to AAT spores thermal inactivation behaviour in pineapple-mango juice blends tested in this study with the lowest value of Mean Squared Error (MSE) and Accuracy Factor (Af) close to unity (0.07 ≤ MSE ≤ 0.48; 0.88 ≤ Af ≤ 1.19) compared to first-order model (0.17 ≤ MSE ≤ 3.41; 1.07 ≤ Af ≤ 2.34).