Theses and dissertations (Applied Sciences)
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Item Effects of processing on the characteristics of flour and protein isolates produced from Lablab purpureus(2020) Naiker, Tremayne Sheldon; Mellem, John Jason; Amonsou, Eric Oscar; Baijnath, HimansuThe utilization of legumes by food industries has grown considerably in intermediate forms other than whole grains. Thus, continuous work is focused on modifying legume-based raw materials for improving its techno-functional properties whilst preserving its nutritive value. The study conducted was aimed at analyzing the effects of processing treatments on the characteristics of flour and protein isolates produced from Lablab purpureus (L.) Sweet (hyacinth bean). Flour was produced from legume grains subjected to steaming (S+A) and dehydration (S+A+D) treatments, following soaking (S). Protein isolates were produced from respective flour fractions using isoelectric precipitation. Samples produced from steaming and dehydration was found useful for potential application as functional food ingredients for nutritional intervention. The respective flour samples contained improved resistant starch (23.44 g/100 g dry starch) content. Swelling and solubility indices were found to be greater at lower temperatures mainly attributed to the pre-gelatinization of starch granules. Thus, they may be potentially suitable for ingredient application in texture modified foods. Protein isolates produced displayed traits typical of high-quality proteins and demonstrated exceptional functionality. The rapid increase in predicted biological values observed suggested improved protein digestibility potential. Samples contained significant concentrations of branched chain and aromatic amino acids highlighting potential health benefits. Protein nanoparticles were produced using Ca2+-induced aggregation (0.00-6.50 mM) from hyacinth bean protein isolate (2% m/v, pH 7). This was to examine its potential for development as food- grade Pickering emulsion stabilizers. Protein solutions containing high Ca2+ concentrations resulted in higher dynamic viscosities (mPa.s). Protein nanoparticles (~172.38 nm) were formed at 3.50 mM Ca2+. The z-average diameter of aggregates was dependent on Ca2+ concentration. Results satisfied certain criteria for nanoparticles to potentially function as Pickering stabilizers. However, nanoparticles were susceptible to 4 M Urea and emulsion creaming became more apparent as storage progressed. The study conducted provides valuable information on how processing could be useful for obtaining value-added legume grain ingredients for potential food applications. Such approach could diversify the use of hyacinth bean and help improve the competitiveness of the legume grain sector.Item Characterisation and application of bambara protein-polysaccharide complex coacervates in encapsulation of bioactive compounds(2019) Busu, Nyasha M.; Amonsou, Eric OscarBambara groundnut (Vigna subterranea) is a leguminous crop that is indigenous to Africa. In South Africa, the legume is cultivated in KZN, Limpopo and Mpumalanga where it is considered a traditional food. Bambara groundnut is a good source of protein (15 – 28 %) and contains substantial amounts of starch. The legume thrives well in areas of low agricultural input. Despite its good protein content, bambara groundnut is mostly cultivated in rural areas for by subsistence farmers. In recent years, there has been increased interest in bambara groundnut protein as an alternative protein source. The purpose of this study is to investigate the complexation behavior of bambara protein with gum Arabic and test the application of the formed complexes in encapsulation and delivery of bioactive compounds. In the first part of this study, four protein fractions extracted at different pH including the salt-solubilisation method were complexed with gum Arabic. The protein content as well as physicochemical properties (SDS-PAGE, FTIR, Zeta potential, SEM) of the protein fractions and resulting bambara protein-gum Arabic (BPI-GA) complexes were then investigated. In subsequent parts of the study, bambara protein extracted by the salt-solubilisation method was complexed with gum Arabic. The influence of ionic strength and biopolymer mixing ratio on complex formation was investigated. Subsequently, the emulsification properties, foaming properties, encapsulation efficiency and release properties of the formed complexes were also investigated under simulated gastric and intestinal pH conditions. The salt-soluble fraction showed the highest protein content (82%) whilst the lowest protein content (76%) was recorded at pH 2. The FTIR analyses revealed an increase in β-sheet content with decrease in pH of extraction. Complexation of the protein fractions with GA resulted in the optimal pHs of interaction shifting towards acidic regions (pHopt: 4.8 to 2.9) as pH of protein extraction became more acidic. Upon complexation, protein fractions produced coacervate yields ranging between 41 - 68%, with the pH 2 fraction recording the lowest (41%) yield. Further, addition of gum arabic seemed to broaden the turbidity profiles. When assessed by SEM, the particles appeared as spherical and aggregated structures between 100-200 nm.