The aim of this study was to optimize and compare the production of glucose syrups from starches isolated from Algerian white sorghum and imported corn in order to study the possibility to use sorghum starch as alternative for glucose syrups production. Two combinations (acid–enzyme and enzyme–enzyme) amylolysis of starch isolated and purified from white sorghum using alkaline method and commercial corn starch were tested. The optimal conditions of the two hydrolysis steps (liquefaction and saccharification) were determined. Concentrations of 30% and 35% (w/v) for white sorghum and corn starches, respectively, were used as substrate. Optimal saccharification process occurs at 60°C, pH of 4.5 during 72 hr, and 1% (w/v) of Rhizopus mold amyloglucosidase. Final values of DE 88.32% and 97.03% using enzymatic liquefaction and 83.81%, 94.68% using acid liquefaction were obtained for sorghum and corn starches, respectively. The results indicate that the enzyme–enzyme amylolysis is more advantageous due to a high glucose conversion yield. Practical applications The study has shown that starch of white sorghum cultivated in disadvantaged regions of Algerian Sahara can be used for glucose syrups production. Starch represents 74.82% of kernel (db) and has very interesting physicochemical properties which make it a potential source of glucose syrups industry. The enzymatic amylolysis led to get glucose syrups with DE of 88.32% and good sensory properties. This product is widely used in pharmaceutical industries and commercial food production as a sweetener, thickener, and moisture‐retaining agent. Further research will be planned to carry out for its applicability.

Chayote, Sechium edule (Jacq.) Sw., is anoverlooked food‎ plant despite its various ‎potentialities. This study investigated the characteristics of starch isolated from ‎chayote fruit cultivated in Algiers which is known for its Mediterranean ‎climate. The granules morphology, functional properties and amylose content of Algerian chayote fruit starch were examined. Spherical, oval and polygonal shapes and smooth surface were observed using three imaging techniques: a normal and polarized light microscopy with Lucia ‎software and Scanning Electron Microscopy (SEM).‎ Starch granules size was in the rang 3.56-‎‎37.24 μm, and for the chayote tubers, it‎ was 7-50 μm. The amylose content (‎20.36%‎) ‎‎is different from that of the chayote tubers (12.81%), but ‎close‎‎‎ to those of ‎conventional sources. The Algerian chayote fruit starch showed higher swelling strength and lower ‎melting ‎index.‎ The Rapid Visco Analyzer pasting profile revealed a lower peak ‎viscosity (2158.3 cP) than that from chayote tubers (14746 cP).‎ However, Differential Scanning Calorimetry analysis showed higher gelatinisation temperatures (66.89 °‎C) and ‎transition enthalpy (‎15.79‎ J/g)‎. X-ray diffraction profile showed B-type.‎ The digestibility (D∞), hydrolysis index, HI, and average glycemic index, (GI), were estimated at 50.66 %, 52.16% and 70.16 ‎%‎ respectively.‎ The results showed that starch has an ‎acceptable nutritional value with significant in vitro digestion properties and it is suitable for human health and nutrition.‎ The starch of Algerian chayote fruit showed interesting ‎functional characteristics which makes it suitable for relevant applications in both the field food and cosmetics industries. It can, also, be a raw material for starch processing.

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.