Mass transfer phenomena for erythrosine and red gardenia dyes in cherries (Prunus avium): influence of temperature on effective diffusion coefficients

GONZÁLES PACHECO JUAN IGNACIO; MARIELA B. MALDONADO

Buenos Aires

Congreso; 11th World Congress of Chemical Engineering (WCCE11); 2023

UBA

Objectives: The study focuses on the quantification of the diffusion phenomenon of the artificial and natural colorant, erythrosine, and red gardenia, respectively, in cherries, at different temperatures, by means of the calculation of the diffusion coefficients, using a mathematical model based on Fick's second law. Materials and methods: CIELAB colour space parameters were measured in triplicate, with a Konica Minolta CR-400 colorimeter device, illuminant D65, in approximately 5 kilograms of calibrated, pitted, and desulfited cherries for 24 h, through immersion in water baths, prior to the candying process. A method of multiple impregnations called "Slow or French Method" was adopted, using a 35 Bx hypertonic solution concentration to confit the food [1]. Moreover, cherries were stained with erythrosine and red gardenia at 238 ppm and the process performed at 40, 50 and 60°C. The sampling of cherries was carried out at different frequencies, as the colouration phenomenon progressed, 2 cherries were randomly extracted from different parts of the container. Subsequently, employing a knife they were cut in half, to dispose cross section and proceed with the measurement of the colour space parameters, thus detecting colour changes during pigment diffusion. Additionally, during the cherry staining, effective diffusion coefficients in skin and flesh were calculated, adjusting a hollow sphere diffusion model to experimental values. On the other hand, the results were analysed by analysis of variance (ANOVA), followed by the multiple comparison Tukey-Kramer HSD test, as well as the Scheffe test, with a significance level of 0.05 to determine the statistical difference in the mean of the coefficients.Results: The effective diffusion coefficients for erythrosine in skin and flesh were on average 2.12 10-11 m2/s and 1.25 10-10 m2/s, whilst for red gardenia were 2.70 10-11 m2/s and 1.59 10-10 m2/s, respectively. Further, no significant differences were observed (p>0.05) between the treatments. Conclusions: Considering the adjustment of temperatures, superior coefficients were appreciated according as the temperature increased, indicating that this could accelerate the diffusion of dyes. Moreover, during the first hour of started the process, the main molecular movement for the entry of the dyes was reported. Erythrosine and red gardenia's effective diffusion coefficients in cherry skin were between 1 and 2 orders of magnitude lower compared to those in cherry flesh, probably due to the barrier effect provided by the cherry skin [2]. Furthermore, when the colorants saturated the cherry flesh, all the effective diffusion coefficients, for both pigments, decreased as the colouration progressed.