Abstract
Seven kinds of starch gels were selected as model samples for the fundamental pulse NMR study to evaluate the quality of foods. Three kinds of samples were prepared: as-prepared, stored in chilled room at about 0℃ for 7 days, stored in refrigeration room at -18℃ for 7 days. The measurement of relaxation time T2 was carried out using CPMG method. The T2 values varied from 20〜184 ms and 24〜153 ms in 0℃ and -18℃ samples, respectively, at PS = 0.04 ms. The CPMG decaying curves were approximated by a simple exponential function for wheat, corn, non-glutinous rice, glutinous rice, and buck wheat suggesting that the water molecules in these gels were rather homogeneous. On the other hand, the CPMG curves were approximated by a sum of two exponential functions for kudzu and potatoes. The relation between T2 and gelatinization degree that is a typical measure of the quality of starch foods showed good linear relation except for kudzu and potato. The linear relationship suggests that T2 has a potential ability for a measure of the quality of starch foods. The observed T2 had an order of "as-prepared" > "-18℃ sample" > "0℃ sample" corresponding to the degradation of foods during refrigeration except for potato.
