Comparison of Immobilized and Free Amyloglucosidase Process in Glucose SyrupsProduction from White Sorghum Starch.

Optimum conditions for glucose syrups production from white sorghum were studied through sequential liquefaction and saccharification processes. In the liquefaction process, a maximum dextrose equivalent (DE) of 10.98 % was achieved using 30 % (w/v) of starch and Termamyl ɑ-amylase from Bacillus licheniformis. Saccharification was performed by free and immobilized amyloglucosidase from Rhizopus mold at 1 % (w/v). DE values of 88.32 % and 79.95 % were obtained from 30 % (w/v) of starch with, respectively, free and immobilized enzyme. The immobilized Amyloglucosidase in calcium alginate beads showed reusable capacity for up to 6 cycles with 46 % of the original activity retained. The kinetic behaviour of immobilized and free enzyme gives Km value of 22.13 and 16.55 mg mL-1 and Vmax of 0.69 and 1.61 mg mL-1 min-1 , respectively. The hydrolysis yield using immobilized amyloglucosidase were lower than that of the free one. However, it is relevant to reuse enzyme without losing activity in order to trim down the overall costs of enzymatic bioprocesses as starch transformation into required products in industrial manufacturing. Hydrolysis of sorghum starch using immobilized amyloglucosidase represents a promising alternative towards the development of the glucose syrups production process and its utilization in various industries.

In vitro starch digestion in sorghum flour from Algerian cultivars.

This work aims to evaluate starch digestion in whole sorghum grains. Nine sorghum cultivars were sampled from the Sahara of Algeria. The structural characteristics of sorghum grains were measured. Total starch (TS) varied between 67.67% and 74.82%, digestible starch (DS) between 64.34% and 69.70%, and resistant starch (RS) ranged from 2.55% to 7.98%. The kinetic of starch digestion displayed first-order model. For all sorghum cultivars, starch were digested with different extents, DS at infinite time (D ∞) ranged from 52.58 to 102.13 g/100 g dry starch, while the hydrolysis index (HI) ranged from 41.55% to 76.93% and high average glycemic index (GIavg) ranged from 65.97 to 94.14. The results showed that there are differences in grain quality of Algerian sorghum cultivars. The starch fractions have acceptable nutritional value with good in vitro digestibility characteristics suitable for human health and nutrition.