ABSTRACT

Objective: Sorrel (Hibiscus sabdariffa) and citrus (Citrus sinensis) are widely utilised in the local beverage industry. By-products from this industry are mainly utilised as fodder and fertiliser but may be of commercial value. Phytochemical analyses were therefore performed on extracts from by-products of this industry. Extracts were evaluated for their antioxidant activity, total phenolics, fatty acid, crude fibre, pectin, ash and zinc content.

Methods: Antioxidant activity and total phenolics were evaluated by a spectrophotometric assay. Lipids were Soxhlet extracted and characterised by nuclear magnetic resonance spectroscopy and gas chromatography/mass spectrometry. Zinc content was determined by atomic absorption spectroscopy. Crude fibre, pectin and ash were determined gravimetrically.

Results: Extracts showed antioxidant activity with methanolic extracts containing higher levels of phenolics than ethyl acetate extracts. Lipids were a source of omega 6 and omega 9 fatty acids. Palmitoleic acid was also identified in citrus extracts. Palmitic acid is the major saturated fatty acid present. Based on the predicted iodine value, citrus lipid extracts are expected to be more stable to oxidation compared to sorrel extracts. Zinc analysis by atomic absorption spectroscopy revealed that sorrel extracts had higher levels of zinc (367.3 ppm) compared to citrus extracts (Zn 5.0 ppm). Extracts were a minor source of pectin and crude fibre.

Conclusion: By-products from the local beverage industry may be considered for the use in food and nutraceutical applications. They are a source of antioxidants, essential fatty acids, zinc and crude fibre.