Physio-chemical, mineral composition and antioxidant properties of Roselle (<i>Hibiscus sabdariffa</i> L.) extract blended with tropical fruit juices

Abstract

Different varieties of fruit juices and beverages are available globally and there has been an increased consumption of fruit juices and beverages due to consumer awareness of nutritional and health benefits. Juice extracts are produced from various parts of plants including leaves, fruits and  flowers. Hibiscus sabdiriffa (Roselle) is one such plant whose flowers are used to prepare juices. The roselle extract has a unique red colour, good flavour, low sugar and high acidic content. The acidity makes the juice sour hence the need for addition of sweetening products. A study was conducted on the formulation of roselle extract-tropical fruit blends aimed at  establishing its physiochemical, mineral and antioxidant composition. Dried roselle calyces at a ratio of 1:10 (dried roselle calyces: water) were  extracted at 50oC for 30 minutes. The roselle extracts were blended at various proportions of fruit (mango, papaya and guava) juices.  Physiochemical, mineral composition and antioxidant properties were  evaluated in all the roselle fruit juice blends The results for all roselle-fruit blends (80% roselle to 20% roselle) showed that pH ranged between  (2.35-3.32), total soluble solids (5.6-10.6o Brix), titratable acidity  (1.28-1.92 %), reducing sugars (2.95-5.55) mg/100g,. Calcium  (555.3-23.4 mg/100g DM), Magnesium (213.8-11.5 mg/100g DM),  Phosphorus (39.8-9.0 mg/100g DM), Sodium (2.3-5.47 mg/100g DM), Zinc (5.85-0.69 mg/100g DM), Iron (29.5-1.36 mg/100g DM), monomeric  anthocyanin (493.5-118.2 mg cyanidin-3-glucoside/100g), vitamin C  (40.0-86.5 mg/100g), total phenol (54.6-10.8 mg gallic acid/ 100 g) and antioxidant activity (1.80-1.37 mmol/L). Blending of tropical fruit juices with roselle extract have improved mineral composition and antioxidant  properties of fruit juices as roselle is a good source of calcium, magnesium and iron. Antioxidants acts as free radical scavengers inhibit lipid  peroxidation and other free radical mediated process, therefore,  consumption of roselle-fruit juices with high anthocyanin will protect human body from several diseases attributed to the reactions of free radicals.

Key words: Roselle, Fruit juice, Antioxidants, Minerals