Drying Characteristics of Bean Analog - A Sorghum Based Extruded Product

Abstract

Bean analog is a novel bean-like re-formed product made from the extrusion of three flour combinations (sorghum, wheat and soy). This product was evaluated under three drying conditions, namely oven, infrared and solar drying, and were fitted to empirical and semi-empirical models. Infrared drying produced the highest drying rate of all methods. Effective moisture diffusivity (EMD), which is an indication of drying rate, ranged from 6.8 × 10−10 to 1.74 × 10−9, 2.05 to 9.22 × 10−9 and 8.70 × 10−10 to 6.10 × 10−9 m2/s for the oven, infrared and solar dried bean analog, respectively. Low EMD for oven drying, against expectation, is attributed to low heat transfer due to limited air circulation. Page equation fitted the drying data better than Lewis, and Henderson and Pabis, with higher R2 values. Oven dried samples rehydrate better compared with others, which can be attributed to slower drying impact on structural changes. Practical Applications Re-formed foods are becoming avenue to substitute for or increase access to deficient nutrients in major staple foods, especially protein and micronutrients like vitamin A and iron. Bean analog is a newly developed navy bean like product made from extrusion of combined ingredients like sorghum, soybean and wheat, which are excellent sources of proteins. This study addressed the stability of the product for storage by evaluating the drying characteristics of the product under different drying methods, and using various empirical and semi-empirical models to fit the drying data.