Physicochemical characterisation of plant-based protein ingredients for the development of infant nutritional formulations

Abstract

This thesis describes novel research into the nutritional and techno-functional characteristics of plant-based protein ingredients, from pseudocereals and legumes, to scientifically underpin the development of innovative plant-based infant nutritional products. Developing a better understanding of the complex inter-relationships between process, composition and functionality of plant-based protein-rich ingredients was critically important in realising their application in infant nutritional products. The macronutrient composition differed significantly between pseudocereal and legume protein-rich ingredients, and such differences were mainly attributed to the processes used for protein enrichment. The protein-rich pseudocereal ingredients, obtained by dry fractionation, with protein content ranging from 20.5 to 38.6%, had higher contents of starch, fibre and fat, whereas legume-based protein isolate ingredients, obtained by wet fractionation, had higher protein content (85.13-93.7%) with lower levels of fibre, fat and had no starch. Protein profile analysis showed that both sources had common globulin proteins, the major protein fraction found in pseudocereals and legumes. Compared with their corresponding flours, protein-rich pseudocereal ingredients had impaired bulk handling properties, with higher cohesiveness associated with higher fat content. The starch and fibre components of the protein-rich pseudocereal ingredients influenced their rheological properties, contributing to high viscosity during thermal treatment. In contrast, legumebased protein-rich ingredients (i.e., lentil protein isolate), showed excellent emulsifying and thermal stability properties. Therefore, lentil protein isolate was investigated further as a novel protein source for the development of a concentrated (30% total solids) oil-inwater emulsion system as a base for infant formula manufacture and displayed high thermal (pH 6.8, 95-140°C) and mineral stability at <4 mM CaCl2. To achieve a regulatory-compliant, balanced amino acid profile in a model infant formulation, quinoa and lentil proteins were combined in different ratios and it was shown that a 60:40 mixture positively affected the physical stability of plant-based oil-in-water emulsions. All these new data from the earlier parts of the project were harnessed in development, at pilot scale, of a lentil protein-based model infant formula powder with similar reconstitution and colloidal properties to commercial plant-based infant formula (i.e., rice- and soybased). The new scientific findings presented in this thesis constitute a significant advancement in the understanding of functionality of plant proteins of relevance in the development of nutritionally complete formulated plant-based products.