Abstract
Background. Roselle seeds are waste that is left behind during processing of roselle for juices or other roselle related products. Disposing of waste is highly undesirable both economically and environmentally. Roselle seeds contain high amount of protein, crude fibers, fats, and carbohydrates. The objective of this study was to determine the effect of different processing techniques (roasting using oven/microwave, and boiling) on Indonesian roselle (Hibiscus radiates) seed constituents.
Methods. Three treatments were carried out to prepare the samples: The seeds were roasted at 130 and 150 degrees C for 30 min (HOR), microwave roasting for 10, 20 and 30 min HMR10, HMR20, HMR30 of roselle seeds. Hibiscus seeds (3x200 g) were put into boiling tap water (100 degrees C) (HB) in a 500 ml beaker on magnetic stirred hot plate at a ratio of 1:4 seed: water for 40 min until the pieces were well cooked and tender. Proximate chemical analysis was determined following the standard methods of the Association of Official Analytical Chemists. Hibiscus different samples were analysed in triplicate and the results were reported as means. Total carbohydrate content was calculated from the difference. The fatty acids of the oil samples were analysed using gas chromatography (Shimadzu, GC-2010A series, Shimadzu, Tokyo, Japan) equipped with a flame ionization detector and a BPX70 capillary column of 30 m x 0.32 mm i.d. (SGE, Melbourne, Australia). The tocopherol content of the oil samples was measured by HPLC (Cecil Instruments Ltd., Cambridge, England).
Results. Proximate composition of untreated, roasted and boiled hibiscus seeds showed that, roasting and boiling temperatures can increase fat and fiber content, microwave and boiling showed higher fat content when compared with oven roasting treatment. Protein content of HU was significantly lower (p < 0.05) than roasted and boiled Rossle seeds. Statistical results indicated that the protein of Roselle seeds increased in the order of HB > HMR > HOR. Protein content of HB, HMR and HOR increased significantly as compared with HU. The carbohydrate values of Indonesian Rossele treated seeds were significantly (p < 0.05) different from each other. The main fatty acids in all samples were palmitic and linolenic. These fatty acids did not change with roasting and boiling temperatures. Tocopherol concentration decreased during processing techniques as a result of heating temperature.