Optical rotation measurements in process control and engineering research in foods

Abstract

A system to measure optical rotation (OR) and transmitted light (TL) was built and tested by the Centro de Investigacion en Ciencia Aplicada y Tecnologia Avanzada (CICATA, Mexico). A similar system was built and tested by the Food Process Engineering Group (FPEG) at Oregon State University. OR and TL values, as a function of time and sample temperature, were recorded by a data acquisition system. Sucrose (1\% w/v) and distilled water were used to calibrate both instruments while sucrose solutions were used to determine sensitivity, linearity and stability. The OR of sucrose solutions was measured with less than 3\% (0.03 to 20 g/l 00 mL) and 2\% error (0.01 to 20 g/100 mL) for the FPEG and CICATA system, respectively. The instrument setup was tested at CICATA by monitoring sucrose hydrolysis and by comparing initial and final OR with published reference values. Application examples tested by FPEG were the characterization of hard candies and the fermentation monitoring of tepache, a prehispanic alcoholic beverage consumed in Mexico and some Latin American countries. These tests confirmed the instrument versatility and the advantages of building modular units with light sources and electronic components available today at low cost. This work showed, using specific applications, that modular units for well-established optical measurements such as OR and TL could have additional applications in food process control and engineering research.