Abstract

This study was undertaken to optimise the extraction of ascorbic acid and investigate physicochemical properties of Adansonia digitata, Parinari curatellifolia, Strychnos cocculoides and Ziziphus mauritiana fruits. The factors assessed were: (i) Provenance, (ii) ripening stage (iii) harvesting time (iv) fruit tree maturity (v) storage condition and (vi) processing. The physicochemical properties [ascorbic acid (vitamin C), retinoic acid (vitamin A), reducing sugars, total soluble solids, dry matter and minerals] were determined by standard methods described in Association of Official Analytical Chemists (AOAC). Alternative extracting solvents to the most expensive metaphosphoric acid were investigated and used in the determination of ascorbic acid in this study. Different concentrations of metaphosphoric acid, orthophosphoric acid, acetic acid and their mixtures were evaluated in extracting ascorbic acid from fruit samples. The performance of a solvent system was determined by yield, percent recovery, and stability of the extracted ascorbic acid. The dilute solvent system (0.05 M H3PO4 + 0.025 M HOAc) extracted significantly higher ascorbic acid (p<0.05) from high ascorbic acid containing fruit (fruits with high level of vitamin C), A. digitata and gave higher recoveries (90.44 ± 4.19%) than the standard metaphosphoric acetic acid (0.38 M HPO3 +1.38 M HOAc) (83.08 ± 15.61%). Most of formulated blends performed poorly when low ascorbic acid containing fruits were used than the standard. To assess the effect of provenance, fresh fruits were collected from different geographical positions of Malawi. A. digitata fruit pulp from Chikwawa gave the highest (p <0.001) ascorbic acid (347.7 mg/100g) while Salima provenance the least (233.10 mg/100 g). The level of retinoic acid was highest (60.92 mg/kg) in the fruit pulp from Mangochi while Salima the least (29.86 mg/kg). Fresh P. curatellifolia fruits from Nkhata-Bay afforded significantly the highest (p<0.001) level of ascorbic acid (134.64 ± 6.59 mg/100 g). The level of ascorbic acid (88.1 mg/100 g) was highest in Z. mauritiana fruit pulp from Mangochi.

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School	: School of Natural and Applied Sciences
Issued Date	: 2008

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