Alicyclobacillus acidoterrestris spores as a target for Cupuaçu Theobroma grandiflorum) nectar thermal processing: Kinetic parameters and experimental methods

• Autor(a) principal: Vieira, Margarida C.
• Data de Publicação: 2002
• Outros Autores: Teixeira, Arthur A., Silva, Filipa M., Gaspar, Nelma, Silva, Cristina L.M.
• Tipo de documento: Artigo
• Idioma: eng
• Título da fonte: Repositório Científico de Acesso Aberto de Portugal (Repositórios Cientìficos)
• Texto Completo: http://hdl.handle.net/10400.14/6802
• topic: Alicyciclobacillus acidoterrestris spores; Inactivation kinetics; PEIE method; Isothermal method; Cupuac u (Theobroma

The kinetic parameters of thermal inactivation of a spore former, Alicyclobacillus acidoterrestris, in a tropical fruit nectar [25% of Cupuac u (Theobroma grandiflorum) pulp and 15% sugar] 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 suspension kept frozen between experiments. The aging of spores, under frozen storage, seemed to produce a notorious increase in the z-value from experiment to experiment: Experiment 1 (z = 7.8F2.6 jC, D95 jC = 5.29F0.96 min), Experiment 2 (z=22F5 jC, D95 jC = 5.99F0.63 min), and Experiment 3 (z=29F10 jC, D95 jC = 3.82F0.48 min). The evaluation of the kinetic parameters by the PEIE method was carried out in parallel with Experiment 3, with the same aged spores, and the results (z=31F6 jC, D95 jC = 5.5F1.2 min) were close to the ones obtained in this experiment. From this work, it seems that the PEIE method can also be applied to evaluate the reduction parameters of a spore-forming microorganism, and in a more realistic way, since the continuous system eliminates the errors caused by come-up and cool-down times (CUT and CDT) that are unavoidable in isothermal experiments. Therefore, when designing a thermal process for a continuous system, the PEIE method should be used, or the chances are that the process would be underdesigned, risking that the desired level of spore inactivation would not be achieved. An optimization of the thermal processing conditions was next performed for Cupuac u nectar, considering a 5D reduction in A. acidoterrestris spores. If a pasteurization process is considered, the conditions that ensure safety (9 min at 98 jC) only allow a 55% retention of ascorbic acid (AA). If sterilization is considered, 8 s at 115 jC will ensure a safe product and retain 98.5% of the original ascorbic acid. Therefore, if A. acidoterrestris is considered as the target microorganism, the nectar should undergo an aseptic high temperature short time principle (HTST) process to achieve a 5D reduction in this acidophilus spore former. However, if the hot-fill-and-hold pasteurization process is preferred, the product should be fortified with ascorbic acid.