Rheological and thermal behavior of amaranth starch-sodium caseinate systems: effect of sugar addition and acidification time

Author(s)

Angela Maria Gozzo

• Document type: Doctoral Thesis
• Press: Campinas, SP.
• Institution: Universidade Estadual de Campinas (UNICAMP). Faculdade de Engenharia de Alimentos
• Defense date: 2008-02-26

Examining board members

Florência Cecília Menegalli; Izabel Cristina Freitas Moraes; Alessandra Faria Baroni; Delia Rita Tapia Blácido; Angelo Luiz Fazani Cavallieri

• Advisor: Florência Cecília Menegalli; Rosiane Lopes da Cunha

Abstract

The starches are frequently added to the foods owed their properties and water retention, as colloidal emulsion-estabilizing agents. The amaranth is a low cost culture, and his starch, a new ingredient with potential industrial use. The caseinato of sodium is a salt derived of the casein thoroughly used as emulsion in foods. The study proteins and polysaccharide mixtures is of great interest, because such combinations can take the a wider interval of properties than the pure gels of protein or polysaccharide. In this work, the physiochemical characteristics of the starch and the interactions among amaranthus starch-sodium caseinate, added or not of sucrose, were studied in systems maintained at 10 °C and pH in the isoeletric point. These interactions were studied through thermal analyses, water holding capacity, syneresis, structural analysis and behavior rheologic of the biopolymers-sucrose mixture, during and after the gelation. Two acidification methods were compared, one performed at 10°C (slow) and other, at 90°C (fast). The sodium caseinate contributed to favor the elastic and viscous characteristic of the analyzed systems, mainly in the slow acidification, however, the rheologic behavior was governed mainly by the acidification speed, because the gels formed by the slow process presented G' and G" superiors to the systems formed by the fast acidification. Starch-caseínato gels formed structures low contained, with ramified chains, whose net was more structured with the increase of the polymeric concentration, and, the gels porosity formed by slow acidification was larger and more evenly distributed that of gels formed by fast acidification. The sucrose acted as an anti-retrogradation agent, and, this effect went more important for the sucrose- amylopectin interaction than for the sucroseamylose. In spite of delaying the aging, the sucrose didn't act strongly about the interactions, and the gels properties showed to be more strongly dependent of the biopolymers concentration and, mainly, of the acidification temperature. Samples containing larger starch caseinate concentrations presented larger water holding capacity (WHC) and smaller syneresis. The retrogradation of the amaranth starch was not elevated, however, values of DH increased with the sucrose concentration and time of storage and they decreased with the addition of sodium caseinate (AU)