C.-Y. Chang’s scientific contributions

The continuous frying process of gluten balls involved three consecutive deep frying pans. The effects of the temperatures of the first and the second deep frying pans on the quality indices of the obtained fried gluten balls, including expansion volume, expansion ratio, measured value of textural property, Hunter colour b value, and sensory evaluation score, were investigated using response surface methodology while fixing the temperature of the third deep frying pan at 195 +/- 3 degrees C. Based on the obtained sensory evaluation scores, the peak force and brittleness breakdown of textural properties, as well as Hunter colour b value of the fried gluten balls, it was found that the optimum temperature ranges for the first and the second deep frying pans were 130-143 degrees C and 155-161 degrees C, respectively. (C) 1998 SCI.

The alcohol-insoluble solids (AIS) of snap bean (Phaseolus vulgaris L.) pods after different cooking treatments were used as testing materials. The contents of calcium, magnesium ions and non-freezing water, which were analysed by differential scanning calorimetry, in the AIS were determined and compared with the firmness of the bean pod tissues after different cooking treatments. It was observed that the contents of calcium and magnesium ions in the AIS of the bean pods after direct cooking were lower than those of fresh and precooked bean pods, and were also lower than those of the bean pods after precooking followed by cooking. The contents of these metal ions were significantly and positively correlated to the tissue firmness (P<0.01). The degree of esterification (DE) of pectin in the tissue after precooking was 39.3%. The DE of of pectin in the tissue after precooking followed by cooking was 39.9%. These DE values were significantly lower (P<0.05) than that in the fresh tissue (46.0%) or that in the tissue after direct cooking (46.0%). Moreover, the amounts of non-freezing water in the AIS of fresh and precooked bean pods were larger than those of the bean pods after precooking followed by cooking and direct cooking. This also showed a significant and positive correlation to the tissue firmness (P<0.05). It was apparent that the linkages between the pectin molecules in the tissues of snap bean pods after precooking were changed. This change was caused by the action of pectinesterase in de-esterification of pectin molecules and subsequent formation of calcium or magnesium bridges between the free carboxyl groups of adjacent pectin molecules, which resulted in increases in the amounts of non-freezing water in the AIS and in the tissue firmness. These results can be taken as further supporting evidence for the theory of the firming effect of precooking treatment of vegetables.