ABSTRACT
This study aims to evaluate the effect of pepsin and SO2 treatments on the yield and physicochemical-, functional-, and color properties of starches isolated from Tabat and Wad-baco sorghum cultivars. Results revealed that starch yield from treatments B (steeping for 7 h; 3 h in distilled water, 4 h in 0.1 M sodium acetate buffer, pH 4.5), BE (steeping for 7 h; 3 h in distilled water, 4 h in 0.1 M sodium acetate buffer, pH (4-4.5) with 250 mg pepsin), BES (steeping for 7 h; 3 h in distilled water, 4 h in 0.1 M sodium acetate buffer, pH 4.5 with 250 mg pepsin and 0.2% SO2), and S (steeping for 7 h; 3 h in distilled water, 4 h in 0.2% SO2) were significantly higher than that from the control (A; steeping for 24 h in 0.2% SO2) in both cultivars. The combination of pepsin and SO2 treatment (BES) produced an increased starch yield of 78.90% and 85.56% from Tabat and Wad-baco, respectively. Micrographs showed hydrolysis of the protein matrix attached to the starch by pepsin, which created holes on the surface of starch granule. Gelatinization temperature decreased in the treated starches from both cultivars compared to control. Water- and fat- absorption capacities were higher in the starch from all treatments compared to control. Generally, enzyme treatment improved the yield and functional properties of starches from both cultivars.
ABSTRACT
Furundu, a meat substitute, is traditionally prepared by cooking the karkade (Hibiscus sabdariffa L.) seed and then fermenting it for 9 days. Physicochemical and functional properties of raw and cooked seed and of furundu ferments were analyzed. Furundu preparation resulted in significant changes in karkade seed major nutrients. Total polyphenols and phytic acid were also reduced. The increase in total acidity and fat acidity coupled with a decrease in pH indicates microbial hydrolysis of the major nutrients; proteins, carbohydrates, and fats. In vitro digestibility of the seed proteins reached the maximum value (82.7%) at the sixth day of fermentation, but thereafter it significantly decreased. The effect of furundu preparation on N solubility profiles and functional properties, such as emulsification and foaming properties and other related parameters, is investigated in water and in 1 M NaCl extracts from defatted flour samples. The results show that cooking followed by fermentation affects proteins solubility in water and 1 M NaCl. The foaming capacity (FC) from the flour of raw seed decreased as a result of cooking. Fermentation for 9 days significantly increased the FC of the cooked seed, restoring the inherent value. Foam from fermented samples collapsed more rapidly during a period of 120 min as compared to the foam from raw and cooked karkade seeds; stability in 1 M NaCl was lower as compared to those in water. In water, the emulsion stability (ES) from the fermented samples was significantly higher than that of the raw seed flour. Addition of 1 M NaCl significantly decreased the ES of the fermented samples.