Stability of concentrated extracts of Hibiscus sabdarifa L. calyx during storage at different temperatures

Hibiscus sabdariffa L. (Malvaceae) calyx is a valuable food resource in Africa. This herb is rich in phenolic compounds and a good source of natural antioxidants. Concentrated extract prepared with Hibiscus sabdariffa L. calyx is commonly used in traditional African and Asian diets and medicines. However, the organoleptic properties of these extracts are degraded during storage. Therefore, the stability of these products is one of the problems faced by roselle calyx extracts users. Stabilization of the H. sabdariffa extract to prevent or reduce quality changes and to extend shelf-life of these products is a challenge to food processors. In this study, strategies for minimizing or eliminating these alterations were evaluated. Concentrated extract of hibiscus calyx (60 °Brix) was divided into three parts: control, pasteurized and addition of potassium sorbate. The samples were stored at 4, 30 or 45°C for three months. Reducing sugars, pH, titratable acidity and total anthocyanins were determined during 0, 15, 30, 45, 60, 75 and 90 days of storage. The results showed that hibiscus calyx extracts can be stored at 4°C for three months without any changes in organoleptic properties. Pasteurization and addition of potassium sorbate did not improve significantly, the stability of the concentrated extracts during storage periods at high temperature. However, these treatments extended the shelf-life at cooling temperature (4°C) without serious changes.   Key words: Hibiscus sabdariffa L., calyx extracts, stability, storage, temperature.