73C-3 |
Kinetic parameters of Alicyclobacillus acidoterrestris in cupuaçu (Theobroma grandiflorum) nectar for the design of thermal processing conditions |
M. C. VIEIRA1, A. A. Teixeira2, F. M. Silva3, N. Gaspar1, and C. L. M. Silva3. (1) Escola Superior de Tecnologia, Universidade do Algarve, Campus da Penha, Faro, 8000-0117, Portugal, (2) Agricultural and Biological Engineering Department, University of Florida, P.O. Box 110570, Gainsville, FL 32611-0570, (3) Escola Superior de Biotecnologia, Universidade Católica Portuguesa, Rua Dr. António Bernardino de Almeida, Porto, 4200-072, Portugal In order to design adequate thermal processing conditions for fruit nectars, a target for inactivation must be identified. Recently an acidophilic sporeformer (Alyciclobacillus acidoterrestris), very resistant to thermal treatment, was found to be the cause of several spoilage incidents in stored fruit juices. Therefore, the main objective of this research was the modelling and quantification of thermal inactivation kinetics of Alyciclobacillus acidoterrestris spores in a tropical fruit nectar [25% of Cupuaçu (Theobroma grandiflorum) pulp and 15% of sugar]. The kinetic parameters were determined by the Isothermal Method (IM), under batch heating, and by the Paired Equivalent Isothermal Exposures (PEIE) method, under non isothermal continuous conditions. The Isothermal experiments were repeated three times, every 4 months, with the same spore solution, which was kept frozen between experiments. The aging of spores, due to the frozen storage, was observed by a notorious increase in the z value from experiment to experiment: 1) (z=7.8°±2.6°C, D95ºC=5.29±0.96 min), 2) (z=21.6±2.6°C, D95ºC=5.99±0.63min) and 3) (z=29±10°C, D95ºC=3.82±0.48min). Evaluation of the kinetic parameters by the PEIE method was performed in parallel with Experiment 3 and the results (z=30.7±5.6°C, D95ºC=5.5±1.2 min) are similar. The PEIE method is able to evaluate the reduction parameters of a sporeforming microorganism, and in a more realistic way, since the continuous system seems to be less lethal then the batch system. The design and optimization of the thermal processing conditions, considering a 5D reduction in Alicyclobacillus acidoterrestris spores, indicated that if a pasteurization process is considered, the conditions that ensure safety (9 min at 98°C) only allow a 55% retention of ascorbic acid. If sterilization is considered, 8 seconds at 115°C will ensure a 98.5% retention of ascorbic acid.
Session 73C, Food Engineering: Transport Processes and Kinetics
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