MODELING THE TRANSPORT OF LACTIC-ACID, SODIUM-CHLORIDE AND REDUCING SUGARS IN CARROT SLICES SUBMERGED IN BRINES .1. UNIVARIATE APPROACH

The transport phenomena pertaining to the independent diffusion of lac tic acid and sodium chloride from a brine into carrot slices submerged therein, and of reducing sugars in the opposite direction, were exper imentally studied at various temperatures and initial concentrations o f salt and acid in the brine. The data sets obtained at each combinati on of temperature and initial concentration of the brine were independ ently fit to three analytical models derived from first principles on three alternative mechanisms postulated for tire time-variation of the diffusivity. Incremental sum of squares analyses have shown that the diffusion of acid and salt into the carrots is well described by a con stant diffusivity, whereas the diffusion of reducing sugars out of the carrots is well described by a diffusivity undergoing a sigmoidal var iation with time. This sigmoidal variation may be explained by the ass umption that tile bursting of the carrot cells is simultaneously propo rtional to the fraction of intact cells and the fraction of burst cell s of the carrot material. The analysis developed is relevant because i t allows an approximate prediction of the rates of acid and salt intak e, as well as the release rates of reducing sugars, pertaining to brin ed carrot slices, the basic processes that occur during manufacture of lactic acid carrot pickles. (C) 1996 Elsevier Science Limited.