Investigation of non-enzymatic browning characteristics of Sardasht black grape juice concentrate using Response Surface Methodology

To study the effect of non-enzymatic browning reactions, quantification of 5-hydroxymethyl furfural (HMF) and on the browning index (BI) was done. In this study, the kinetics of BI in Sardasht black grape (Rasheh variety) juice concentrate was studied. Samples with different Brix's (60.5, 65.6 and 70.7) in three temperatures (5°C, 15°C, and 25°C) were kept for 85 days. In addition, the color analysis was also evaluated by a Hunter lab. Analysis of variance showed that all three factors (Brix, storage time and temperature) were effective in HMF content (P<0.05). They had a linear positive relation with HMF content in black grape juice concentrate. HMF content of concentrate was in the range of 0.57-50.6 (mg/kg). Also, all three factors had a significant effect on the BI (P<0.05) and its content was measured between1.054 - 1.373.