Effects of Processing on Proximate Composition of Hibiscus rosa-sinensis Leaf

Leaves of Hibiscus rosa-sinensis are processed using different methods depending on the intended application. Using three different processing methods, we investigated the effects of processing on the proximate constitution of the leaf. Result demonstrated that the fresh raw leaf had moisture content of 82.30 ± 0.42%, which were significantly (p<0.05) reduced by drying but not extraction and blanching. The protein content of the raw leaf was low (1.80 ± 0.10%). Extraction and blanching reduced the protein content, whereas drying increased the protein content significantly (p < 0.05) for raw dried leaf powder and blanched leaf products. The raw leaf contained vitamins A, B2, C and E, which were significantly reduced by extraction and blanching, but were concentrated by drying. Anti-nutrient contents of the raw leaf were low and were reduced to negligible levels by the processing techniques employed. Comparing the nutrient and chemical constituents with recommended dietary allowance (RDA) values; we found that the leaves contain an appreciable amount of nutrients, minerals, vitamins, proteins and phytochemicals and low degree of toxicants. These findings suggested that the treatment method employed in processing this leaf affected the proximate composition, and this should be considered in utilization of this leaf (and other leaves) product in various food and pharmaceutical formulations.