Correlação entre medidas do biospeckle laser e atividade de água de soluções em diferentes concentrações e temperaturas

Abstract

Directly linked to food stability the water activity (aw) has a great importance to estimate the useful life of a product. A high value of water activity implies that the product is more sensitive to deterioration. The search for new technologies for application in this area becomes important in order to make analysis of water activity faster. The biospeckle laser is a technology that employs an optical method that processes graphically or numerically the interference patterns formed when a biological material is illuminated by a coherent light, such as the laser. The objective of this work was to evaluate the potential of biospeckle laser application with the methodology of numerical contrast analysis to test new approaches to improve the technique of determination of water activity. In the present work it was demonstrated that the biospeckle laser technique through contrast analysis was statistically significant in distinguishing different concentrations and water activities from lithium chloride solutions and model solutions at temperatures of 0, 5, 10, 15, 20 and 25 °C. Through calibration of the biospeckle laser with the lithium chloride solutions the predicted values of the water activity of different foods were tested at the same temperatures, obtaining some correlations with water activity values lower than 20% in comparison to the real aw. Thus, the biospeckle laser technique can become a tool for direct reading of the concentration of solutes and, consequently, of water activity in foods.