Evaluation of Citric Acid Production Potentials of Food Processing Wastes

Abstract

Objective: To evaluate citric acid production potentials of food processing wastes. Materials and Methods: Samples of domestic wastes generated from peels of Yam (YP), Cassava (CP), red cocoyam (RCP), white cocoyam (WCP), ripe plantain (RP), unripe plantain (UPP) and garri processing chaff (GPC) were washed, oven-dried, pulverized and analysed for their biochemical constituents alongside characterization of their sugar contents. Samples were also reconstituted in mineralized media fortified with glucose at 5.0%(w/v), then autoclaved (121°C/15min), cooled and inoculated at 5.0%(v/v) with Aspergillus niger. The samples were incubated at 30°C for 14 days and evaluated at intervals of 2 days for citric acid yields and residual sugar contents. Results: The total carbohydrate contents of the samples ranged from 67.24-76.42% while the starch contents ranged from 0.84-10.48% and the cellulose contents from 3.14-19.70%. No significant differences (p>.0.05) were observed in the carbohydrate contents of CP, RCP, WCP, RPP, UPP and GPC. Glucose, maltose, and sucrose were the predominant sugars characterize in the samples. Highest citric acid yields were obtained in RPP (108.0mg/l and GPC (103.-mg/l) on the 8 th day of fermentation. Lowest residual sugar contents were obtained in GPC on days 6-10 followed by RPP. Conclusion: Maximum acid development in the samples (96.09 – 108.0mg/l) was obtained from 6-8 days of fermentation. The residual sugar contents of the samples vary with the sample types and decreased significantly (p<0.05) with increasing fermentation periods. Keyword: Food processing wastes, citric acid, A. niger, fermentation, residual sugar.