Water is one of the main components of food and its presence is related to the rate of deterioration of foods. Thus, control of the water activity (a w ) is a fundamental feature of food technology. The methods currently used for determining a w of foods mostly use the relative vapor pressure of the product to quantify the a w at constant temperature. This last factor limits evaluation of the a w because the instrument used is not capable of determining the a w at temperatures lower than 25 °C and/or at negative temperatures. In this study, the potential of the biospeckle laser for a w measurement was evaluated. Contrast analysis using the biospeckle laser technique provided statistically significant differences in the concentrations and a w for lithium chloride solutions and model solutions of pectin and sucrose at temperatures of 0, 5, 10, 15, 20, and 25 °C, as well as at freezing temperatures. After calibration of the biospeckle laser with the lithium chloride solutions, a w of corn starch, oatmeal, and wheat flour was determined at different temperatures, with errors lower than 20%. This achievement provides a platform for developing protocols to measure the a w of foods at different temperatures using the biospeckle laser.
Journal of Food Measurement and Characterization – Springer Journals
Published: May 30, 2018
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