91C-32 |
Optimization of the spray drying process of brewer’s yeast ( Saccharomyces cerevisiae) |
M. A. SALGADO-CERVANTES1, G. Luna-Solano, G. C. Rodríguez-Jimenes, and M. A. García-Alvarado. (1) UNIDA, Instituto Tecnológico de Veracruz, Av. Miguel Angel de Quevedo 2779, P.O. Box 1420, Veracruz, 91860, Mexico The utilization of dried yeast for brewing is a new alternative for mexican breweries. The researches showed that through the use of spray and fluidized bed drying, it's possible to obtain a brewery dried yeast with an efficient viability and fermentative ability, this avoid the propagation and fresh yeast transport. The spray drying process, however, requires large quantity of energy, which was not considered in previous studies. In this work the optimization of spray drying process for brewer's yeast was proposed. Experimental spray drying of brewer's yeast were at different air out temperature (60-70°C), rotor speed (16 600-25 000 r.p.m.) and grits concentration (1:1-0.5:1). The viable cell count was determined by the pour plate method. The amount of dried yeast obtained and energy required (kW·h) during drying were used in order to calculate the cost ($/kg of dried yeast) and the production (kg of dried yeast/h). The optimization was defined as the determination of the three process variables that yield the minimum cost subject to desired viability and moisture. The viability of the dried yeast was higher than 1 X 106 cfu/g in most of the treatments, which is a viability level accepted to fermentation in the mexican industry. Moisture content and water activity of these products ranged from 4-11.8 % (d.s.) and 0.32-0.69 respectively. The experimental results of viability, production and cost were used in order to fit a response surfaces model. The cost function was minimized with viability function as restriction by using a complex algorithm. The optimal state was 60 °C, 19 120 r.p.m., and 1:1. The result of this work suggests the process state in which one can obtain dried brewer's yeast at a given viability at minimal cost.
Session 91C, Food Engineering: Food process engineering
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