Lipid Oxidative Stability, Antioxidant Capacity, and Protein Quality of Direct-Expanded Chickpea-Sorghum Snacks

Abstract

A chickpea and sorghum blend was used for production of direct-expanded snacks to increase the protein content and quality of such products, which are well known to and consumed by people of various ages due to their texture and convenience. The use of whole grain chickpea and sorghum also would provide other nutritional benefits. However, chickpea has a relatively high fat content (3-10%, dry weight basis) compared to most other pulses which increases the susceptibility to oxidation and reduces the shelf-life of direct-expanded products containing chickpea. In addition, the fat content of whole grain sorghum (2-6%, dry weight basis) is significant compared to that of milled sorghum or corn. Expanded snacks are highly susceptible to lipid oxidation due to their expanded surface area and low water activity. Since lipid oxidation affects sensory quality and nutrient content, determining the lipid oxidative stability and shelf-life of direct-expanded chickpea-sorghum snacks was important. Related to this, examining the total phenolics content and antioxidant capacity of chickpea-sorghum snacks and their contribution to oxidative stability also was worthwhile. Ultimately, it was important to determine the protein quality of the direct-expanded chickpea-sorghum snacks. Hence, the overall purpose of the study was to investigate the use of a whole-grain chickpea-whole grain sorghum blend for production of direct-expanded snacks from oxidative stability, shelf-life and protein quality perspectives. Direct-expanded snacks were prepared from blends of whole-grain chickpea and whole-grain sorghum (70:30, 60:40 and 50:50 chickpea:sorghum, w/w) using a twin-screw extruder at barrel temperatures of 1200C, 1400C and 1600C and moisture contents of 16%, 18% and 20%, as well as at the determined optimal expansion point, 1690C barrel temperature and 15% moisture content. Chickpea and sorghum flours also were extruded at the maximal expansion point. An oxidative stability study (p-anisidine value and peroxide value) was carried out on snacks produced at the maximal expansion point. The oxidative stability of the 50:50 chickpea-sorghum snack was found to be higher (P<0.05) than that of the 60:40 and 70:30 chickpea-sorghum by both sensory and chemical analysis. Similarly, the shelf-life was higher (P<0.05) with a lower proportion of chickpea in the blend. A higher proportion of sorghum in the blend, extrusion and an increase in barrel temperature were associated with an increase (P<0.05) in antioxidant capacity, total phenolics content and in vitro protein digestibility, whereas an increase in moisture content decreased (P<0.05) these measurements. A higher proportion of chickpea in the blend and extrusion increased the in vitro protein digestibility corrected amino acid score (IVPDCAAS) of chickpea-sorghum snacks. The protein quality of the 70:30 chickpea-sorghum snack produced at the maximal point was found to be higher (P<0.05) than that of the 60:40 or the 50:50 chickpea-sorghum snacks with minimal loss of available lysine. The study demonstrated that whole-grain chickpea and whole-grain sorghum can be used in the production of direct-expanded snacks having acceptable shelf-life and protein nutritional quality, hence chickpea-sorghum snacks could play a role in addressing protein-energy malnutrition in sub-Saharan Africa.