Thermal Characteristics of Ohmically Heated Rice Starch and Rice Flours

Abstract

Thermal properties of conventionally and ohmically heated rice starch and rice flours at various frequencies and voltages were studied. There was an increase in gelatinization temperature for conventionally heated rice starches since they were pregelatinized and became more rigid due to starch-chain interactions. In addition, there was a decrease in enthalpy (energy needed) for conventionally and ohmically heated starches during gelatinization; thus, the samples required less energy for gelatinization during DSC analysis. Ohmically heated commercial starch showed the greatest decrease in enthalpy probably because of the greatest extent of pregelatinization through ohmic heating. Brown rice flour showed the greatest gelatinization temperature resulting from the delay of starch granule swelling by lipid and protein. Enthalpy of ohmically heated starches at 20 V/cm was the lowest, which was most likely due to the lower voltage resulting in a more complete pregelatinization from a longer heating time required to reach 100 degrees C. Ohmic treatment at 70 V/cm decreased onset gelatinization temperature of white flour; therefore, it produced rice flour that swelled faster, whereas the conventionally heated sample showed a better thermal resistance.

Physicochemical, Cooking Characteristics and Textural Properties of TOX 3145 Milled Rice

“…This finding in our study is not surprising because the parboiling protocol for these two samples involve soaking temperature of 80 ºC. Some previous studies had reported significant lower enthalpy among gelatinized samples in comparison to raw samples due to the less energy needed for DSC analysis in fully gelatinized starch (An & King, 2007;Wang & Sastry, 1997). The study by An and King (2007) demonstrated the greatest decrease in enthalpy in rice sample with greatest extent of pregelatinization.…”

“…Some previous studies had reported significant lower enthalpy among gelatinized samples in comparison to raw samples due to the less energy needed for DSC analysis in fully gelatinized starch (An & King, 2007;Wang & Sastry, 1997). The study by An and King (2007) demonstrated the greatest decrease in enthalpy in rice sample with greatest extent of pregelatinization. The color parameters in our study is comparable with values reported in previous study (Singh et al, 2011).…”

Caracterización fisicoquímica, funcional y química de harinas nixtamalizadas de maíz obtenidas por calentamiento óhmico y proceso tradicional

“…Las diferencias encontradas en la HCO procesada con humedad de 450 g agua/kg maı´z y 908C pueden ser debidas a la electroporacio´n de la membrana del almido´n, ocasionando una mayor lixiviacio´n de los componentes del gra´nulo principalmente de amilosa. Esto podrı´a ser deberse a un tiempo prolongado al campo ele´ctrico con poco agua (An & King, 2007;Camargo et al, 2010;Lima & Sastry, 1999;Palaniappan & Sastry 1991); sin embargo habrı´a que realizar un estudio ma´s profundo al respecto.…”

Diffusion mechanisms during the osmotic dehydration of Granny Smith apples subjected to a moderate electric field

“…When applied, an electric field can cause changes in the permeability of cell membranes of plant tissue at lower temperatures at which these membranes are permeabilized by thermal effects, a phenomenon known as electroporation (An and King, 2007;Lima and Sastry, 1999). The resulting effect is that the diffusion process increases, the electrical conductivity changes and the moisture more easily migrates out of the plant tissue (Leizerson and Shimoni, 2005).…”