Moisture Transfer Characteristics and Microbiological Stability of Fermented Pre-gelatinized Plantain and Soybean Based Complementary Food Flours

Abstract

The effect of gelatinization and fermentation on the moisture sorption characteristics and microbial stability of complementary foods from unripe plantain fruits and soybean seeds was evaluated. The plantain was heated to obtain 10%, 18%, 23%, 33%, 74% and 100% starch gelatinization. The samples were fermented, dried and ground to flour. Plantain and soybean flour were mixed by material balance to produce 16% protein complementary foods. Moisture sorption isotherms wereinvestigated at 10, 20, 30, and 40 ° C using the gravimetric method. The BET equation was fitted to the experimental sorption data, and the Clausius-Clapeyron equation was used to determine the isosteric heat of sorption. The microbial stability of the gruels was evaluated using the microbial challenge test with Staphylococcus aureus. With better results from fully gelatinized samples, gelatinization and fermentation reduced the hygroscopic properties of the dehydrated products, with the gelatinized fermented samples having the least equilibrium moisture contents, monolayer moisture values, surface area of sorbent, and net isosteric heats of sorption, an indication that these samples could be stored at temperatures as high as 40 ° C with extended shelf life. The microbiological stability of foods was enhanced by fermentation, since microbial growth was suppressed in fermented samples, offering perspectives for microbial stability of the products.