Determination of formulation and processing factors affecting slowly digestible starch, protein digestibility and antioxidant capacity of extruded sorghum–maize composite flour

Abstract

Summary High‐temperature high‐pressure extrusion of sorghum–maize composite flour, of potential for healthy food manufacture, was investigated by factorial experimental design to determine the effect of level of sorghum in dry mix (15–60%); final barrel zone temperature (120–150 °C); total moisture in barrel (21.4–25.8%); total input rate (2.3–6.8 kg h−1); and screw speed (250–450 rpm) on extrudate slowly digestible starch (SDS), phenolic content, antioxidant capacity, protein digestibility, density and expansion ratio. Extrudate SDS increased with increasing sorghum level and decreased as the barrel temperature increased. Total phenolic content and antioxidant capacity were positively associated with sorghum level. Protein digestibility was associated negatively with sorghum level and positively with barrel temperature. Extrudate density was associated positively with total moisture and negatively with barrel temperature and input rate. Sorghum in dry mix, final barrel zone temperature and total moisture in barrel were the three most significant independent variables influencing extrudate dependant variables.

Sorghum: An Underutilized Cereal Whole Grain with the Potential to Assist in the Prevention of Chronic Disease

“…Factors such as the precise ratios of amylose to amylopectin, their arrangement within the starch granule, further degradation of other polymer molecules and post-processing conditions also influence the postprandial effects of a starchy food. (44) Recent publications report on the in vitro starch digestibility of different sorghum foods, including sorghum-refined maize snack-like extrudates, (45) wholegrain sorghum-refined wheat flour flat bread (46) and wholegrain sorghum-durum semolina pasta. (14) These in vitro studies confirm that sorghum foods can be formulated and processed to deliver slowly digested starch 1 Sorghum starch granules are densely packed in the corneous endosperm but exist in a more open structure in the floury endosperm of the grain caryopsis.…”

“…(54) In sorghum-consuming communities, where protein malnutrition is an issue, efforts to increase protein digestibility are imperative and lactic acid fermentation, decortication and extrusion have been shown to improve digestibility and consequent amino acid availability. (45,66,68) Sorghum grain also contains a broad range of bioactive peptides, recently reviewed by Lin et al (69) These are of current interest to researchers due to their potential biological role in human physiological processes including pathogenesis. The peptide bioactivities include antioxidant, antihypertensive, anticancer, antimicrobial, and opioid activities as well as immunomodulatory and cholesterol-lowering effects.…”

Coeliacs cannot live by gluten‐free bread alone – every once in awhile they need antioxidants

“…. Despite their nutritional benefits, the antioxidant supplementation with whole grain and rice bran(Capriles et al, 2016), germinated brown rice(Cornejo et al, 2015) or sorghum(Licata et al, 2014) flours presented certain technological limitations because these flours notably changed the appearance, colour, texture, aroma and taste of gluten-free products, which can easily impair consumer acceptability. Despite their nutritional benefits, the antioxidant supplementation with whole grain and rice bran(Capriles et al, 2016), germinated brown rice(Cornejo et al, 2015) or sorghum(Licata et al, 2014) flours presented certain technological limitations because these flours notably changed the appearance, colour, texture, aroma and taste of gluten-free products, which can easily impair consumer acceptability.…”

Perspective: the path to confirming and exploiting potential satiety-enhancing effects of sorghum-based foods for human diets

“…Researchers have formulated a variety of organolepticallyacceptable sorghum-based foods that deliver slowly digestible starches (flat bread, pasta, extruded snacks), identifying sorghum's potential as a viable food ingredient in the manufacture of new grain products (Yousif et al, 2012;Khan et al, 2013;Licata et al, 2014). Specific indications for effects have come from animal studies (Shen et al, 2015), but to date few human studies have been conducted.…”