Effect of microbial transglutaminase on functional, rheological, and structural properties of lentil protein-casein binary gels

In recent years, various strategies have been introduced to partially substitute animal proteins with plant proteins. This study applied microbial transglutaminase (MTGase) to crosslink lentil protein isolate (LPI) and casein. The gel mixtures prepared using different LPI-casein ratios (4:0, 3:1, 2:2, 1:3, 0:4), and the structural, gelation characteristics of these hetero-mixtures were investigated. SDS-PAGE showed the bands of vicilins (∼50 kDa), and 11S acidic subunit (∼40 kDa) almost disappeared and partly 11S basic subunit (20 kDa) involved in the polymerization, whereas almost all the bonds of casein were involved in the MTGase-induced gelation process. With the increasing concentration of casein, LPI-casein binary gels presented enhanced mechanical textural properties (increased from 284.83 to 1128.33g of hardness), rheological properties (increased from 105.8 to 4405 Pa of storage modulus), water holding capacity (increased from 63.86 to 98.82%) and more homogeneous and compact microstructural properties (CLSM, SEM) as a result of homologous and heterologous crosslinking mediated by MTGase. Interestingly, gels prepared by partial casein replacement (by 25% LPI) had similar textural, water holding capacity, and microstructural properties to those prepared by casein-alone gels, demonstrating the possibility of successfully replacing casein with 25% LPI in MTGase induced system. This study presents a new interaction strategy mediated by MTGase for LPI and casein binary system to greatly enhance their gelation performance, as well as the potential of LPI in substitute dairy to formulate diversified food products.