Estudo reologico dos amidos de amaranto, de mandioca e de suas misturas, sob condições de acidez e tratamento termico / Rheological study of cassava and amaranth starches and their blends under heat treatment and acidity

AUTOR(ES)
DATA DE PUBLICAÇÃO

2008

RESUMO

Starch has been widely used as a thickener, stabilizer or gelling ingredients in the food like soups, sauces, snacks, canned and refrigerated food products. In this foods processing, starch dispersion are often heated, cooled and pumping at a wide range of shear rate. In many foods, sours substances (various acids) are added to foods as acidulents or preservatives. Important factors like texture, pasting properties, appearance and viscosity of starch pastes must be conserved when the starches are submit to stress conditions. But native starches present limitations that reduce their usefulness. A less costly alternative to modifications is the use of blends of native starches from different sources, which is keeping with current preferences for ?natural? products. Our objective is to investigate how acidity and heat treatment effects the granules and the rheological properties of starch blends (amaranth:cassava), amaranth and cassava starch pastes. The starch gels (5%w/v), natural and acid pH, with or without heat treatment (autoclaved 121oC/30 min.) are studies through microscopy, functional properties and rheological behavior. The blend of starch showed lower swelling than pure starches. The acidity decreased swelling of the amaranth and cassava starches, but did not influence the commercials starch. The gelatinization study by rheometer was influenced by acid that increased the elastic modulus of cassava, amaranth, blend and 9560 starch gels. The gelatinization study by DSC exhibited acid influence in the initial and peak temperatures of amaranth and cassava starches. The natural, acid and natural autoclaved gels exhibited tixotropy and pseudoplastic behavior. The natural gel rheological behavior of amaranth and blend were described by HB model, although gel behaviors of cassava, 9460 e 9560 were described by Law power model. Acid gel rheological behaviors were described by HB model, except 9560 gel, that exhibited Law Power model. Natural autoclaved gels exhibit a rheological behavior were described by HB model and acid autoclaved gels were described by Law Power with n values approximately 1. A general way, in the steady test, the blend gel behavior was similar to cassava starch gels. In dynamic test, the blend behavior was similar to amaranth gels. In dynamic test, natural, acid and autoclaved natural gels were classified like weak gels, except natural autoclaved cassava gel, that exhibit behavior like entanglement suspension. Autoclaved acid of amaranth, cassava and blend did not exhibit viscoelastic behavior. The acidity influenced the n e k values parameters to different temperature. The amaranth and commercials starch gels exhibited lower changes in elastic and viscous modulus during storage

ASSUNTO(S)

mandioca rheology starch amarantos reologia amido cassava amaranth misturas acidity blend heat treatment acidez tratamento termico

ACESSO AO ARTIGO

Documentos Relacionados