Μελέτη των λειτουργικών ιδιοτήτων των πρωτεϊνών επιλεγμένων οσπρίων (Phaseolus vulgaris L. και Phaseolus coccineus L.)

Abstract

The aim of this study was the production of protein concentrates from two bean cultivars, Phaseolus vulgaris L. and Phaseolus coccineus L. and the investigation of their emulsifying and foaming properties, in order to asses their potential use as food ingredients. Protein concentrates were prepared by three different methods, and were studied for their composition, protein profile and solubility. The protein fraction of albumins was also prepared by two different methods and was also studied. The protein concentrates prepared by isoelectric precipitation and ultrafiltration were chosen for further study. Their surface activity was studied as it was affected by the protein concentration and the protein solution pH value. Their emulsification and foaming properties were also evaluated. The stability of o/w emulsion was studied with respect to protein concentration and pH value. At higher protein concentrations the emulsion stability was enhanced, while the pH values of the continuous phase seemed having an impact on the mean diameter of oil droplets. The addition of NaCl, for the concentrates prepared by isoelectric precipitation and ultrafiltration enhanced emulsion stability at a concentration of 0.1M and 0.05M respectively. For all the other concentrations studied the system was destabilized. The effect of the addition of polysaccharides (arabic gum, locust bean gum, xanthan gum and xanthan-locust bean gum mixture) was also investigated. Polysaccharides in general promoted stability, (which is even more pronounced for higher polysaccharide concentration and for xanthan and xanthan-locust bean mixture), due to the increase of the emulsion continuous phase viscosity. Foams were also prepared and studied. An increase in the protein concentration lead to an increase in relative overrun, but it did not have the same impact on foam stability. The pH of the continuous phase affected both foaming ability and stability. The addition of NaCl seemed to have the same effect as was observed for emulsions. Apart from one specific concentration for its concentrate, in general NaCl addition brought about deterioration of the system. When polysaccharides were added, both ability and stability were increased, with the more pronounced result observed in the case of xanthan gum and the xanthan-locust bean gum mixture. For the latter two polysaccharides at their higher concentration their positive effect on foam ability seemed to be restricted. There was a close parallelism between surface activity, emulsifying and foaming properties. Still differences were observed between concentrates and also between the two cultivars. Concentrates from isoelectric precipitation produced better emulsions and the concentrates from ultrafiltration exhibited better foaming activities. Generally the results of this study showed that Phaseolus bean proteins have good functional properties in order to be incorporated into food products.