Studies in concentration and preservation of sorrel extract

Abstract

The popular sorrel (zobo) juices drink which is about 99% water is known to be easily susceptible to microbial spoilage. The need thus arises to standardize its production to give quality product of compact packing and adequate shelf life. In this work attempts were made to study thermal
concentration of the juice extract and its chemical preservation. Concentrating the juice to about 17% solid was found to improve its life on open shelf from one -and-a-half to three days while reducing the ascorbic acid content by 50%. Addition of sodium benzoate was found to improve the storage of the exposed juice substantially without noticeable change in vitamin C content. The 15% reduction in mass achieved with thermal concentration consumed 20.05, 15.91 and 14.14 MJ per kg juice treated at 60, 80 and 90°C respectively. These correspond respectively to 5.571, 4.420 and 3.929 kWh of energy expenditure per kg of the extract.

Key words: Sorrel drinks, Hibiscus sabdariffa, concentrate, preservative, sterilization, heat of vaporization.