Okara flour: its physicochemical, microscopical and functional properties

Abstract

Purpose Okara, which is the residue of hydrosoluble extract from soybean obtained after soymilk and tofu production, has high nutritional value and can be used for ingredient in specific food products. This study aims to evaluate the production and properties (physicochemical, microscopical and functional ones) of okara flour (OF) obtained from okara as a by-product of soymilk and tofu production. Design/methodology/approach Wet okara resulted from the soymilk process underwent convective drying up to reach mass stability (60°C for 12 h). OF properties were analyzed by official methods by AOAC, i.e. mineral composition was evaluated by atomic absorption equipment; color; water absorption index (WAI); milk absorption index (MAI); oil absorption capacity (OAC); and foam capacity (FC) required mixtures with water, milk and oil, separation and gravimetry, respectively; and microstructure was determined by a scanning electron microscope. Findings Results showed the potential OF has as a source of protein (24.74 g/100 g) and dietary fiber (58.27 g/100 g). Regarding its color after the drying process, OF was markedly yellow (b* parameter 20.16). Its WAI was 3.62 g/g, MAI was 4.33 g/g, OAC was 3.68 g/g and FC was 1.32 per cent. The microscopic analysis of OF showed that both loose and agglomerated particles had irregular structures and indefinite forms. Originality/value Production of flour from wet okara can be an alternative use of this by-product. This study showed important characteristics of OF and its possible application to the food industry. Thus, OF was shown as a potential ingredient with high nutritional value.

Bioactive components, in vitro digestibility, microstructure and application of soybean residue (okara): a review

“…SEM is a useful technique for determining the microstructure of food products by evaluating the arrangement of starch granules within the protein matrix (Kamble et al, ). Santos et al () conducted a study to examine the microstructure of okara flour particles by means of an SEM (Figure ). The results showed that flour components were either loose or agglomerated; that is, a heterogeneous composition was observed in the micrograph.…”

“…Although okara flour is considered as a depreciated product from wet okara, it has low storage volume and greater storage stability as the product's moisture content is low after drying. It may therefore be an alternative to the use of this by‐product as a whole (Santos et al, ). Advanced and hygienic large‐scale production techniques must be applied efficiently to ensure high‐quality and sustainable products (i.e., quick removal of moisture to produce a dry solid product of >94% with a low water activity [ a w ] confirming its storage stability; Schved & Hassidov, ).…”

“…A maximum drop in GI was observed in pasta containing 50% okara flour (12.38). Protein digestibility of various okara-based food formulations has been investigated earlier (Espinosa-Martos & Rupérez, 2009; F I G U R E 3 Microstructure examination of dried okara (adapted fromPorcel et al, 2017, Voss et al, 2018, and Santos et al, 2019…”

Improving Diet Quality for Chronic Disease Prevention With Okara “Food Waste”

“…Dried okara consists of about 57-59% dietary fibers (42-57% insoluble, 2-17% soluble), 15-34% protein, 6-16% fat, as well as a considerable amount of mineral elements such as calcium, potassium, iron, and antioxidant substances, including isoflavones. 8-12 Because of the high nutritional value, okara has numerous health benefits such as improving glucose tolerance and hypolipidemic effects. Therefore, it may help prevent diabetes, cardiovascular disease, obesity, as well as improving intestinal health through prebiotic functions.…”

“…Okara has been produced worldwide including Asian countries such as Japan, Korea, China, Singapore, 23,24 and has a huge potential to become an alternative flour. 10 As long as soy products such as soy milk or tofu are produced, okara will be continuously produced. Although okara has high nutritional value, it is often used as animal feed and mostly disposed through incineration.…”