Efeitos do tratamento hidrotérmico na formação de isoflavonas agliconadas e nas propriedades funcionais de isolado proteico de soja

Abstract

Soybeans may contain up to twelve types of isoflavones, of which only deconjugated s forms, daidzein, glycitein and genistein, are absorbed directly into the gastrointestinal tract. The other isoflavone forms must suffer of the enzyme β-glucosidase hydrolisys i the gut before being absorbed by the body, or processing conditions, such as soaking in soy beans are undertaken in order to activate the β-glucosidase enzyme, present in grains, and promote conversion of conjugated isoflavones in the grain, increasing the bioavailability of isoflavones. This study assessed the use of hydrothermal treatments performed in soybeans to promote increases the isoflavone aglycone content due to the activation of the enzyme β-glucosidase of the grain, and investigates these compounds in soy protein isolate. Soybeans were treated hydrothermically through soaking in water at a ratio of 1:5 (w/v, soy:water), at two temperatures (40 and 60°C) for 4, 8, 12 and 16 hours.The beans were dried to 13% moisture, milled and defatted, the resulting defatted flour (FD), was destinatedd to produce the soy protein isolate (IPS), the process generated two fractions: the insoluble residue (RS) and supernatant (SB). The FD, IPS, RS and SB were evaluated for isoflavone aglycone and chemical composition in order to check the maintenance of isoflavones in the IPS. The IPSs from grain treated hydrothermically were also evaluated for functional and nutricona characteristics and l through electrophoresis analysis, DSC, total phenolics, antioxidant activity, protein digestibility, solubility, water absorption capacity, foaming capacity and foam stability, colorimetry , texture profile analysis and scanning electron microscopy. It was concluded that hydrothermal treatments performed at 40°C promotes an increase in content of aglycones in the defatted flour (FD). In IPS, hydrothermal treatments increases its yield from extraction, total phenol content, digestibility, in foaming capacity and foam stability. The treatments at 60°C, although having lower extraction yields of IPSs, promoted selective isolation of proteins with greater ability to interact with isoflavones, producing IPSs with higher concentrations of aglycones per grams of product.