Translating plant protein benefits to consumer products: physicochemical, technological and nutritional aspects of utilising plant protein ingredients for cereal food applications

Abstract

The way we currently produce and consume food puts both environmental sustainability and human health at great risk. A global shift to predominantly plant-based diets as part of a food system transformation promises remedies for environmental implications as well as rising diet-related disease risks. Nonetheless, a decreased consumption of animal-based foods and increased inclusion of plant-based protein in our diets entails challenges with regard to the development of plant-based protein-foods and their convenience, technological quality and nutritional quality, which were addressed in this thesis. A thorough physicochemical characterisation of plant-based high-protein ingredients (HPIs) is important to explore their full potential for human nutrition and to identify appropriate processing techniques. For example, the quantification of short-chain carbohydrates in plant-based HPIs is required when fermentation technology is applied. In a study comparing commonly used aqueous extraction methods for short-chain carbohydrates with alternative ethanolic extraction methods, ethanolic extraction was found to be superior. Due to high water absorption capacity and gelation, aqueous extraction is often not applicable to plant-based HPIs from a practical perspective. Furthermore, enzymatic activity causing conversion or degradation of short-chain carbohydrates can be minimised with ethanolic extraction. Cereal-based staple foods, like bread and pasta, represent promising matrices for the incorporation of plant-based HPIs (e.g. partial replacement of wheat flour or wheat semolina) and offer the opportunity to provide plant-based protein-foods in convenient formats with high consumer acceptance. In a fundamental bread application study, several plant-based HPIs (derived from cereals, potato, legumes) were screened for their baking performance in high-protein breads (> 20% of calories provided by protein). Based on the findings of this study, an optimised high-protein bread formulation (containing faba bean and carob HPIs) with technological quality and sensory attributes similar to regular wheat bread and improved nutritional profile was proposed. This high-protein hybrid bread was characterised by an isocaloric replacement of wheat starch by non-cereal protein (starch content - 21%, which indicates reduced glycaemic load) and an improved amino acid balance (lysine content based on protein + 65%). Also, a substantially improved nitrogen utilisation (+ 69%) and protein efficiency ratio (+ 88%) compared to regular wheat bread were found in in vivo nitrogen balance tests. Fermentation (utilising the strain Leuconostoc citreum TR116) was investigated as a tool to further improve HPIs’ baking performance and proven to successfully functionalise faba bean ingredients for bread applications, for example, by improving gluten-aggregation, bread volume (+ 19–22%) and crumb hardness (- 38–49%) in the presence of fermented (instead of unfermented) faba bean ingredients. For pasta applications, the combination of HPIs derived from pseudocereals (buckwheat) and legumes (lupin, faba bean) was particularly beneficial to achieve good technological quality since the HPIs were shown to compensate each others’ (positive and negative) effects on quality characteristics like cooking loss, stickiness and tensile strength. The improvement of the high-protein hybrid pasta’s nutritional quality (compared to regular wheat pasta) was also quantified and found to be similar to that observed for high-protein hybrid bread (compared to regular wheat bread).