DETERMINATION OF DIFFUSION COEFFICIENTS OF FOOD ADDITIVES IN DIFFERENT MEDIA AT 25˚C

Abstract

Food additives play a vital role in today’s bountiful and nutritious food supply and their transportation in water is a diffusion process governed by Fickian diffusion laws. The study looks into the rate of diffusion of ascorbic acid, citric acid, sodium nitrite, sodium citrate, and L-(+) - tartaric acid at 25˚C in water, HCl and NaOH solutions of different concentrations. The objective of this work was to determine the diffusion coefficients of each food additive using spectrophotometric and moving boundary methods and to compare the diffusion coefficients obtained with those calculated from limiting ionic conductance at infinite dilution. The absorbance at different height levels (𝑥) were measured at a given time and at specific wavelength. The boundary heights (𝑥) at a time t and concentration were also recorded. The diffusion coefficients were obtained from and square-root relationship respectively. The spectrophotometric diffusion coefficient ranged from -4.06798 x 10-05 to -1.82441 x 10-05 cm2/sec, -3.87546 x 10-05 to -6.4791 x 10-06 cm2/sec, -5.60548 x 10-05 to -1.59965 x 10-05 cm2/sec, -3.09157 x 10-05 to -1.01433 x 10-05 cm2/sec and -2.5445 x 10-05 to -7.96674 x 10-06 cm2/sec and for moving boundary/indicator method were 1.1500 x 10-04 to 6.3728 x 10-05 cm2/sec, 1.2250 x 10-04 to 7.4908 x 10-05 cm2/sec, 1.3500 x 10-04 to 1.0286 x 10-04 cm2/sec, 1.5652 x 10-04 to 1.2746 x 10-04 cm2/sec and 1.2974 x 10-04 to 7.4908 x 10-05 cm2/sec for ascorbic acid, citric acid, sodium nitrite, sodium citrate, and L-(+) - tartaric acid, respectively. Spectrophotometric diffusion coefficients were in close agreement with the expected Do values unlike moving boundary/indicator method. This method is also cheap, accurate and applicable method, under ordinary laboratory conditions and within a short experimental time. This study will provide a set of reference data of diffusion coefficients of food additives and can be used for routine food safety analysis.