DEVELOPMENT OF FUNCTIONAL BEVERAGES FROM BLENDS OF HIBISCUS SABDARIFFA EXTRACT AND SELECTED FRUIT JUICES FOR OPTIMUM ANTIOXIDANT PROPERTIES

Abstract

Food choice is increasingly being controlled by taste, health benefit and functionality. Hibiscus Sabdariffa extracts (zobo drink) is popular, cheap and has numerous health benefits. Functional beverages include in their formulation, ingredients such as raw fruits and vegetables or herbs, vitamins and minerals which possess the potential to improve the health of consumers by reducing the risk from or delaying the onset of major degenerative diseases. This study was carried out to investigate the effects of blends of pineapple, orange, carrot juices and zobo and the optimal antioxidant level for the four- ingredient functional beverage using Response surface methodology. Investigations were carried out using 15 experimental points with 5 replicates for 4 independent variables (zobo 10–100%, pineapple 0-40%, carrot 0-30% and orange 0-40%). Responses of antioxidant and physicochemical properties [(1,1-diphenyl–2 picrylhydrazyl (DPPH) radical scavenging ability, 2, 2’-azino-bis (3-ethylbenzothiazoline-6-sulphonic acid) ABTS, Vitamin C, Total phenols, Ferric Reducing Antioxidant Potential (FRAP), Total carotenoids, Total titratable acidity (TTA), Total soluble solids (TSS), total solids (TS) and pH] were analysed. The pH, TTA, TSS, TS ranged from 2.6-3.6, 0.49-2.35%, 5-32oBrix and 90.61-124.03% respectively. The antioxidant properties with regards to ability to scavenge ABTS, Total carotenoids, % DPPH Inhibition, FRAP, Total phenols and Vitamin C of the juice blends ranged from 42-73mmolTEAC/g, 0.77-3.86mg/g, 33-73%, 61.59-247.82(μmol Fe2 SO4/g), 435.58-1496mgGAE/100g and 2.45- 8.89mg/g respectively. Response surface plots generated showed that formulations containing pineapple, carrot, orange and zobo of 40.0%, 16.49%, 17.20% and 26.3% respectively produced optimum antioxidant benefits. The predicted optimum beverage blend (POB) was subjected to sensory evaluation, mineral analysis and storage studies for 8 weeks, with and without preservatives. The POB contained Total phenols of 512.82mgGAE/100g, Vitamin C of 3.37mg/g, and % DPPH Inhibition of 51.34%. The acceptability of the optimized beverage was accessed to be 7.7 for aroma, 6.2 for taste, 6.9 for colour and 6.4 for overall acceptability on a 9 point Hedonic scale. There were no pathogenic microorganisms identified. Total aerobic plate count of microbial load of between 3.5x 104 and 7.4x 105 was recorded after six weeks of storage. Antioxidant properties: Total Phenols, DPPH and Vitamin C decreased at the end of the storage period. The 100% beverage without preservatives had a stable shelf life of 6 weeks, during which a loss in Vitamin C, total phenols, % DPPH of 43.34%, 10.89%, 26.48% was recorded respectively. The 100% juice with preservatives had a recorded loss in Vitamin C, total phenols and % DPPH of 40.06%, 5.61% and 23.2% respectively. All chemical compositions and microbial quality analysed were within the standard acceptable range when compared with the standard specification. Combination of pineapple, carrot and orange juices with zobo at blending ratio of 40.0%, 16.49%, 17.20% and 26.3% gave the optimum antioxidant properties and sensory quality.