CHEMICAL CHARACTERISATION OF HIBISCUS SABDARIFFA (ROSELLE) CALYCES AND EVALUATION OF ITS FUNCTIONAL POTENTIAL IN THE FOOD INDUSTRY

Abstract

Antioxidant capacity, phytochemicals, phyto-nutrients and bioactive compounds, have all become buzzwords in the growing market for natural health food-products and speciality juice drinks. The main objective of this study was to determine the bioactive compounds in the calyces of  Hibiscus sabdariffa  L. and evaluate its functional potential hence provide an incentive to production, processing and consumption of roselle in Kenya where it is not widely cultivated and utilized. Proximate composition was determined using established AOAC methods. Antioxidant activity (AA) color degradation index (CDI) and were carried using 1-1 diphenyl picryl hydrazyl radical (DPPH) and hunters color meter respectively. HPLC, UV-visible spectrophotometer and atomic absorption spectrophotometer (AAS) were used to determine water soluble vitamins (WSV), total polyphenolic content (TPC) and mineral composition respectively. Product formulations were done and their consumer acceptability determined based on a 9-point hedonic. It was  found that the properties of roselle extract before and after pasteurization included pH of 3.88 ± 0.00 and 3.42 ± 0.01, total acidity (as malic acid) of 2.24 ± 0.00 and 2.24 ± 0.03 %, total phenolic contents of 6.06 ± 0.18 and 5.82 ± 0.01 mg/g roselle extract, respectively. The antioxidant activities using DPPH assay with ascorbic acid standard, expressed as EC50 (Efficient Concentration) were 230.01 ± 2.40 and 235.34 ± 0.79 μg/ml, respectively. Iron and calcium were content was 8.59  ±  0.31 and 14.83  ±  0.60 mg/100g respectively. After sensory analysis, the pure roselle drink was generally more acceptable in taste, flavor, aroma, consistency and overall characteristics with an average overall score of 7.6 out of 9 in comparison with Rosela orange drink, rosella apple drink and rosella melon drink. These properties give roselle the potential as a functional ingredient in beverage manufacture and other applications such as utilisation in polymeric natural color development. Roselle can also be applied in the food industry for manufacture of red wine and roselle fruit flavored preserves, thus exhibiting great potential in commercial application in the food and pharmaceutical industry. More studies for in-vivo properties of Roselle extracts are however needed, to  further substantiate the health claims of roselle extract in human nutrition.