Effects of pigment removal on the physicochemical properties of Hibiscus Sabdariffa extracts and on the sensory quality of reformulated Zobo drink

Abstract

Various forms of drinks exist in varying sensory and organoleptic properties owing to slight modifications in their processing. Zobo drink is a formulation of extract from red fleshy calyces of H. sabdariffa that gained popularity in virtually all local areas in Nigeria. Red Sorrel “Zobo” has been reported to have acidic nature and blood-red colour, which give the drink its coarse texture, and hinder its acceptability in the global market. In this study, the extract of the Roselle was slightly de-pigmented with a natural adsorbent to reduce the acidity found in the plant material and to improve on the colour and sensory quality of the local drink. Physicochemical properties, pH variation over a period of five days and UV-Visible absorption of the original and slightly de-pigmented extracts were compared. There were large differences in the physical parameter values of these extracts. Pigment removal reduced the; acidity @25 ^oC with pH 2.8 to 3.5, temperature 23.2 ^oC to 22.9 ^oC, conductivity (μS/cm) 4790 to 3410; TDS (mg/L) 3114 to 2217 and turbidity (NTU) 17650 to 5050. It also reduced the; total hardness (mg/L) 2700 to 1900, total alkalinity (mg/L) 3100 to 2400, chlorides (mg/L) 1300 to 1000 except the PO₄²- (mg/L) which increased from 30.9 to 39.1 and Na⁺ (mg/L) 46.1 & 88.1; while K⁺ (mg/L) remains constant 655. Large difference was also observed in the electromagnetic light absorption (3.501 to 2.001) at λ_max 500 nm. Consumer acceptability test of the drinks attested that the slightly de-pigmented drink surpassed the original local drink in all sensory qualities and consumers’ acceptance. In conclusion, the adsorption of sparingly soluble pigment particles on natural adsorbent altered the pH values, total dissolved solids, particle sizes, colour and other sensory properties.