In situ monitoring of starch gelatinization with limited water content using confocal laser scanning microscopy

Abstract

The gelatinization of starch is crucial for the production of bakery products. Therefore, the examination of the characteristics and the extent of this process are of fundamental importance for research and product development. Typical analysis methods for studying structural starch changes during heating are performed in excess of water. Considering that wheat dough is a complex system with reduced water content, an option to analyze starch gelatinization under actual product conditions is missing. Therefore, an in situ method in a confocal laser scanning microscope (CLSM) equipped with a heating system was developed to monitor the starch gelatinization in samples with different flour to water ratios [(m:v) 1:0.39, 0.49, 0.51, 0.53, 0.55, 0.57, 0.59, 0.98, 4.91, 5.63 and 7.14]. The new method was used to investigate the start of starch gelatinization temperature (T G) by using thresholds based on first derivatives with highest correlation between T G of CLSM and the onset temperature (T o) of differential scanning calorimetry. A highly significant linear correlation between T G of A-type granules and T o was observed (R 2 = 0.903). The size and shape of granules with a ratio of 1:0.98 show a clear impairment against samples with higher water content. The newly modified in situ method enables the measurement of starch gelatinization in different flour to water ratios independent of secondary factors. Consequently, it can be used for complex starch-based systems with reduced water content to investigate the actual starch granule structure disintegration.