Effects of enzymatic modification of pea and soy protein on the pasting and rheological profile of corn starch-protein systems

PD RIBOTTA; CM ROSELL

Madrid, España

Congreso; 13th ICC Cereal and Bread Congress. Cereals in the 21st century: present and future; 2008

ICC

Reformulation of traditional food systems to introduce new ingredients may change their structure and perceived texture, since products result from interactions between different components. Interactions between proteins and starch during processing can markedly influence starch gel network structure and rheological profile. Soy proteins, due to good nutritional value and abundant availability as by-products of oil processing, have received considerable attention for the replacement of expensive animal proteins in conventional foods. Pea is a widely consumed legume seed with high-nutritional value proteins, but protein-based ingredients of pea are not yet well utilized in food applications. The present work aimed to study the effects of pea and soy protein enzymatic modification on the pasting and rheological profile of corn starch and on the resulting network structure. Pea protein isolate (PPI) and soybean protein isolate (SPI) were used as source of plant proteins. Protein isolates were incubated with endopeptidase (Alcalase 2.4 L) or microbial transglutaminase (TG). Pasting and rheological behaviour, water retention capacity and structure of protein-corn starch gels were analyzed. Protein solubility and SDS-PAGE profile were also determined. Protein incorporation increased the viscosity of starch suspension during and after heating. Enzyme-modified proteins changed starch pasting in a different way: SPI-modified proteins increased peak viscosity and PPI-modified proteins decreased it. Only the structural modifications brought by TG on SPI increased the final viscosity during starch pasting. Storage modulus (G’) of the gelled systems decreased with the addition of alcalase-treated protein isolates. When SPI was used, TG treatment increased gel G’, but the opposite effect was observed when TG-modified PPI was incorporated. Enzymatic treatment changed protein solubility and structure. Light and fluorescence microscopy showed that SPI formed a continuous phase, like a network, in the gelled system. However PPI seemed to remain as isolates particles. Different network structures and rheological properties can be obtained when different enzyme-treated protein isolates are combined with corn starch, which may be very useful for designing new food products.