73C-7 |
Effect of aw, temperature and vacuum package on fluidized bed dried brewer’s yeast (Saccharomyces cerevisiae) viability during storage |
M. A. SALGADO1, F. J. Gabino, M. A. Garcia, and G. C. Rodriguez. (1) Food Engineering Department, Instituto tecnologico de Veracruz, P.O. Box. 1420, Veracruz, Ver., 91860, Mexico The conservation of brewer’s yeast by drying represents an alternative to replace yeast cream. Yeast cream has 80 % humidity being difficult to handle and easy to contaminate. Besides, storage space and transport cost are bigger. The aim of this work was to evaluate the stability of the dehydrated yeast during storage under different aw, temperatures and vacuum package. Brewer’s yeast cream with a viability of 1.2 x 10 9 cfu/g was filtered in order to obtain a paste with 65 % of humidity. Corn starch was added to this paste at 20 % w/w in d.b. The paste was extruded for obtaining cylinders of 1 mm of diameter. The yeast was dried by fluidized bed at 30 °C at different drying times, in order to obtain yeast with aw of 0.4, 0.5 and 0.6. They were packed in aluminum bags with a vacuum of 0.6 atm and without vacuum (air). They were stored at 5, 25 and 35 °C. The experimental results showed that an increase of the storage temperature produces a detrimental for the conservation of the yeast viability. However, storage at three temperatures didn’t show significant difference at aw 0.5 and 0.6. Vacuum storage maintains to twice the viability of under all treatments tested. The best treatment was at 5 °C, vacuum packaging and aw of 0.4, where the loss of viability was only 0.07 logarithmic cycles in 180 days. An empirical mathematical model for relating a viability at a given time as a function of aw and temperature was obtained. This work showed the effect of three variables on brewer’s yeast viability during storage. The mathematical model obtained can be used for shelf life predictions of dried brewer’s yeast.
Session 73C, Food Engineering: Transport Processes and Kinetics
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