Contribution of starch and protein to the mechanical properties of plant-based food.

Summary

In several processed foods, such as vegan cheese and meat analogues, proteins are used together with starch to obtain specific textural properties. From a physicochemical point of view, these systems can be considered composite gels. To be able to control the textural properties of these foods, it is important to know more about the behaviour of protein and starch and about the contribution of each of them to the properties of the end product. In this research, a series of maize starch (MS) gels with increasing pea protein isolate (PPI) content and one of PPI gels with increasing MS content were evaluated for thermal behaviour (DSC), water competition (NMR), microstructure (CLSM) and mechanical properties. Increasing PPI inhibited the degree of MS gelatinisation. Based on the water absorbed by PPI and MS, it was concluded that this component was not sufficient in any of the studied samples. NMR showed that starch and protein had the different water-binding capacity, which caused uneven water distribution. Water lack and uneven distribution resulted in partial gelatinization of MS, which affected the microstructure of the gels. CLSM micrographs showed that by varying the MS:PPI ratios the microstructure of the samples changed from filled gel to bi-continuous gel. With the increase of PPI content, the MS gels became stiffer and more brittle. The increase of MS in PPI gels led to an increase in stiffness and a decrease in the brittleness. These insights can help to develop guidelines to design the microstructure of plant-based food containing starch and protein, and therefore control and modulate their texture.