Abstract: Heat-induced gels were prepared by boiling ultrafine whole soybean flour in water and then adding magnesium chloride and glutamine transaminase (TGase) after cooking. This study aimed to investigate the effect of cooling temperature, magnesium chloride concentration and TGase concentration on texture, rheological and microstructural properties of heat-induced gels. The results showed that the strength and rupture distance of gels with both added magnesium chloride and TGase increased with decreasing the cooling temperature from 25 to 15 to 5 ℃, and were significantly affected by the different cooling temperatures. The gel strength reached the maximum value of 56.23 g when the temperature was cooled to 5 ℃ and 0.8% magnesium chloride and 1.2 U/g TGase were added. The rheological results showed that the storage modulus (G’) of gels with added TGase showed a rapid upward trend. And the G’ of gels with TGase addition after cooling to 5 and 15 ℃ was significantly larger than that of their counterparts without TGase. The lower the cooling temperature, the larger the G’ of the gel. The scanning electron microscopic (SEM) images showed that the network structure of the gels formed by adding magnesium chloride and TGase after cooling to 5 ℃ was more orderly and denser.

Key words: whole soybean flour; temperature; gel properties; microstructure