Mitigating anthocyanins and color degradation in pasteurized cranberry juice fortified with vitamin C

Color degradation in cranberry juice during storage is the most common consumer complaint for this juice. To enhance nutritional quality, juice is typically fortified with vitamin C. Although vitamin C is an effective antioxidant, vitamin C fortification increases degradation of color in cranberry juice during storage. The color degradation is not only an appearance attribute, but also reflects the degradation of health beneficial components, anthocyanins (ACY), because ACY are natural pigments as well as antioxidant compounds. The overall goal of this study was to preserve endogenous ACY in cranberry juice with a feasible solution for the food industry. This study included two specific aims: 1) to evaluate the effectiveness of different antioxidants on ACY retention in cranberry juice and assess the effect on vitamin C retention, color intensity, and browning index (BI) during storage; and 2) to estimate the kinetic parameters and model predictive equations for color and ACY retention in cranberry juice during storage. Three natural phenolic compounds (hesperidin, catechin, and gallic acid) were tested for their protective effect against anthocyanins and color degradation. Cranberry juice was fortified with 40-80 mg/100 mL ascorbic acid and potential protective agents were added at different concentrations. The juice was then pasteurized at 85+/-2°C for 1 minute and stored in the dark at 23+/-2°C for 16 days. Juice ACY, vitamin C, color intensity, and BI were evaluated at 2-day intervals. Among the three phenolic compounds, gallic acid showed the most effective protection against ACY degradation. Addition of gallic acid significantly increased red color intensity (37%) (p < 0.01) and ACY concentration (41%) (p < 0.03) during storage, compared to control juice samples. At the end of 16-day storage, the BI of gallic acid-added juice was significantly lower than that of the control juice (0.80 vs 1.00), confirming the protective effect of gallic acid on juice color. Therefore, the experimental data with gallic acid addition were used for the kinetic study, in order to develop predictive equations for the parameters and the dependent variables. Measurements of total monomeric anthocyanins and red color intensity were used to determine degradation rate constants (k values) and order of reaction (n) of ACY and color. Due to high correlation, k and n could not be estimated simultaneously. To overcome this difficulty, both n and k were held at different constant values in separate analyses to allow accurate estimation of each. Parameters n and k were modeled empirically as functions of vitamin C, and of vitamin C and gallic acid, respectively. Reaction order n ranged from 1.2 to 4.4, and decreased with increasing vitamin C concentration. The final models offer an effective tool that could be used for predicting ACYs and color retention in cranberry juice during storage. The outcome of this research not only provided a potential solution of using gallic acid to address color degradation in commercial cranberry juice, but also proposed models for predicting color and ACY retention.