Study of functional properties of seed storage proteins from indigenous European legume crops (lupin, pea, broad bean) in admixture with polysaccharides

The production of plant protein isolates and especially legumes is of growing interest to industry, because of the increasing application of plant protein in food and non-food markets. The use of plant protein isolates in foods as functional ingredients to improve the texture, the nutritional quality of the product or for economical reasons is very extended. In spite of the relatively high cost of protein from meat, eggs and dairy products, they are consumed in an amount approximately 10 times greater than legume proteins, even though the later are abundant in protein. The objective of our investigation was to characterize some of the functional properties of legume seed protein isolates from lupin, pea and broad beans, prepared by isoelectric precipitation and ultrafiltration, by preparing emulsions, foams and gels. In our study we use native (as could be) protein isolates, as emulsifiers and stabilizers, in admixture with polysaccharides, in order to create a rigid and viscoelastic film around the oil or air droplets and/or for creation of network structure, with desirable texture for the benefits of the consumer. In all cases emulsions stabilized with proteins precipitated at their isoelectric point, even if they have similar initial droplet size distribution with the ultrafiltration ones illustrated greater stability throughout the storage time. The addition of incompatible xanthan gum enhances protein adsorption at a/w and o/w interfaces. In this case, emulsions and foams increase their stability. This may be due to xanthan gum's ability to increase the viscosity of the continuous phase, but also to its effect on protein adsorption at the interface. The emulsion stability for all isolates studied appeared more or less the same. The better foaming quality is exhibited by pea, followed by broad bean and lupin. The addition of NaCl leads to the destabilization of the systems, at the used concentrations. The presence of albumins in ultrafiltration isolates leads to a better foamability, but lowers slightly the stability. Lupin forms gels with the greater fracture properties among all three legumes, for all combinations studied. A strong gel (probably 'filled type') is established only with the addition of a mixture of polysaccharides and after 10 days of ageing. The desired texture of the final product will determine the preferred combination according to its profile analysis parameters.