Asian Food Science Journal

The study evaluated the effect of sweet orange (Citrus sinensis) peel oil as a biopreservative for raffia palm wine and zobo drink. Gas chromatography-mass spectrometry (GC-MS) screening of the extract showed that limonene had a corresponding maximum percentage of 85.90. The wet-mount method indicated the presence of Aspergillus niger, Aspergillus flavus, Candida sp., Saccharomyces sp., Bacillus sp., Staphylococcus sp., and Micrococcus sp. The total heterotrophic bacterial count (THBC) decreased from 7.5 × 10⁶ to 1.0 × 10⁶ CFU/mL and from 6.5 × 10⁶ to 1.0 × 10⁶ CFU/mL, respectively. The total fungal plate count (TFPC) initially increased between 0 and 72 h of fermentation, from 4.5 × 10⁴ to 14.4 × 10⁵ CFU/mL and from 8.0 × 10⁴ to 28.5 × 10⁵ CFU/mL. After 72 h, the fungal counts gradually decreased from 13.9 × 10⁵ to 7.8 × 10⁵ CFU/mL and from 25.2 × 10⁵ to 16.9 × 10⁵ CFU/mL, respectively. As fermentation progressed, the oil inhibited bacterial activity. The analysis indicated that Citrus sinensis peel oil exhibited broad-spectrum antibacterial activity and reduced yeast activity in the beverages, thereby contributing to their preservation. However, the controls changed from 4.5 × 10⁶ to 4.7 × 10⁶ CFU/mL and from 3.0 × 10⁶ to 8.3 × 10⁶ CFU/mL for THBC, with TFPC values changing from 1.0 × 10⁵ to 11.4 × 10⁵ CFU/mL and from 5.0 × 10⁴ to 17.3 × 10⁵ CFU/mL, respectively. The lower counts in the treated samples suggest that oil extracted from discarded Citrus sinensis peel can inhibit microbial activity in raffia palm wine and zobo drink, thereby preserving the beverages and prolonging their shelf life. The oil may also improve the flavour of a wide range of foods.