Peter Adeoye Sopade

Pigeonpea is a potential raw material for the growing plant protein industry, and the food properties of six Australian genotypes (ICPLs 14425, 86022, 88039, 90048, 91039, and 98011) were investigated. In-vitro proteolysis was analysed with a pH drop. The genotypes, coloured cream to brown, differed (p ≤ 0.05) in their total (43.3–56.5), whiteness (40.2–53.4), yellowish (35.4–50.7), and browning (32.1–60.2) colour indices. Potassium, phosphorus, and sulphur were the major minerals. Approximating a sphere (mm, major [6.6] and minor [6.0] diameters, and thickness [5.3]), the genotypes differed in starch (20–32 g/100g solids) and protein (22–27 g/100g solids) contents. Although the genotypes revealed identical pasting (p > 0.05) temperatures (85 ± 2 ℃) and slightly-shear thinning behaviours (breakdown ratio = 0.8–0.9), their peak (124–371), trough (108–337), and final (213–520) viscosities (cP) differed. Essentially, the genotypes were heterogeneous in their physicochemical, colour, and pasting properties. However, their protein digestograms, analysed with the Sopade Objective Procedure (objective logarithm of slope), revealed a true monophasic digestion mode; homogeneous in-vitro proteolysis. Seven kinetic models for monophasic digestograms adequately (r2 > 0.78) described the digestograms, and the Peleg model was recommended. There were no genotypic differences (p > 0.05) in the protein hydrolysis index (HIPROTEIN = 17.4–24.7%) relative to reference casein, average in-vitro protein digestibility (IVPDAVG = 69–71%), rate of protein digestion (KPR = 0.09–0.24 min−1), and other protein digestion parameters. This study pioneers time-course protein digestion for pigeonpea, and with rates of food digestion valuable in future food labelling, a solid foundation for pigeonpea utilizations is presented.

Food digestibility is a major consideration in formulating, developing, and processing foods for health and nutrition. Lipid digestion is important for nutrient supplies, and with in vitro digestion procedures widely used, the results from which are described by kinetic models, there is a need for an in-depth understanding of these kinetic models. With more than 10 kinetic models reported for lipolysis, the relative computational characteristics of these models together are yet to be fully unwrapped along a detailed comparative approach. Kinetic models in amylolysis and proteolysis have been detailedly studied, and a study on kinetic models for lipolysis will complement the other macronutrients to better understand food digestion. A comprehensive review, in a follow-up study, is required to fill this research vacuum and guide researchers on kinetic models for lipolysis.

Summary: In vitro starch digestibility, chemical, pasting, and gelatinisation properties of 10 uncooked pigmented and non‐pigmented Thai white rice were studied. Differing in amylose and starch contents, the samples were also significantly (P ≤ 0.05) different in pasting and gelatinisation properties, maximum digestible starch (40–53 g/100 g dry starch), and rate of starch digestion (0.028–0.054 min⁻¹). The starch digestograms were adequately described (r² > 0.63; P ≤ 0.001) by objective logarithm of slope (Sopade Objective Procedure), modified first‐order kinetic, and two‐term exponential and non‐exponential models to be all truly monophasic. The estimated glycaemic index (g/100 g) ranged from 64 and 84, compared to 41–95 for their brown rice forms (International Journal of Food Science and Technology, 2022, 57, 6699), highlighting how bran and hull components influence starch digestion of polished and non‐polished rice. This study is foundational to detailedly understand starch digestibility when the rice is further treated.

Summary: In vitro starch digestibility of 10 Thai brown rice samples was investigated for foundational in‐depth understandings of treated/processed and untreated/non‐processed rice. The samples were uncooked pigmented, non‐pigmented and differed in amylose contents and chemical and functional properties. The starch digestograms were modelled using innovative techniques involving objective logarithm of slope (Sopade Objective Procedure) and one‐term and two‐term exponential and non‐exponential models. The samples significantly (P ≤ 0.05) revealed monophasic and biphasic starch digestograms, and the digestion parameters were sample‐dependent. Using the Sopade Objective Procedure, which better predicted the digestograms, the biphasic samples exhibited rapid‐slow and slow‐rapid in vitro starch digestion phenomena. The estimated glycaemic index (eGI) of the samples ranged from 41 to 95 g/100 g, and the sample with the slow‐rapid digestion pattern exhibited the lowest eGI. The results are discussed as baselines for follow‐up treatments that typify rice as a notable global food commodity.