Development of functional protein microencapsulates by combining of milk protein ingredients aqueous solutions with blackcurrant concentrate, and encapsulating via spray-drying and freeze-drying, and the applications of microencapsulates in food products : A thesis submitted in partial fulfilment of the requirements for the Degree of Doctor of Philosophy at Lincoln University

Abstract

Whey protein and sodium caseinate play a vital role in many food systems and exhibit multifunctional properties in food processing which enhance physical and nutritional values. The main functional properties, such as water holding capacity, oil holding capacity, foaming, and emulsification, are important charicteristics in food development and production. Among all of the commercially avaliable protein ingredients, both whey protein isolate and sodium caseinate, which are sourced from bovine milk, are widely used as protein ingredients for industial production, such as yogurt and baking products. These milk protein ingredients are nutritious, used for the building and repairing of tissues, fighting against infections, and providing energy for metabolism. Whey protein is obtained from cheese processing by-product-whey. Broadening whey protein’s application is beneficial for dairy industry sustainability and the valorisation of whey protein as a functional ingredient. The functional properties of these proteins are based on their biomolecular structures, which can be modified by several compositional and processing factors. Blackcurrant is abundant in health beneficial phytochemicals, such as vitamin C, polyphenols, and anthocyanins. Due to the intense sour taste, fresh blackcurrant fruits are always processed into juice concentrate for further food application. The bioactive compounds in blackcurrant juice concentrate are unstable in a free form, especially when they undergo further food processing conditions, and also in the human digestive systems. This can contribute to a low bioaccessibility and bioavailability for its health benefit components, especially anthocyanins. The development of further applications for blackcurrant juice concentrate in a food system is of vital importance to aid the sustainable development of the blackcurrant crop industry, and bringing the goodness of this fruit to a wider population. Combinations of common protein ingredients with fruits and vegetables concentrates or extracts are regarded as an effective ingredient to create novel protein products, to explore the application of concentrates or extracts from fruits and vegetables. Many studies have focused on the modification of protein structures, and the alteration of protein functionalities under controlled conditions. However, few studies have focused on the development of novel protein ingredients in a food-compatible manner, and their further incorporation in real food system. Whey protein isolate and sodium caseinate have been commonly used as delivery systems for functional components due to their wide availability, nutritional values, and protective effects on sensitive bioactive components. In this study, blackcurrant juice concentrate was encapsulated via spray-drying and freeze-drying strategies by utilising whey protein isolate or sodium caseinate as the wall material without applying any food additives, obtaining four different kinds of novel protein ingredients (SWB, FWB, SNaB, FNaB) with different physicochemical, functional, and nutritional characteristics. The nutritional, physicochemical and functional properties of these ingredients were determined and defined. The results indicated that these ingredients could be used as natural colourants, protein enhancers, antioxidants, replacement of carbohydrate. The novel functional protein powders were then further incorporated into real food matrix-cookie at various levels (0%, 5%, 10%, 15%) to develop functional snack (cookie). Dough and cookie physicochemical properties, and cookie nutritional qualities were determined. The protein ingredients gave cookie products with different colour and texture, increased antioxidant power, and most importantly generated hypoglyceamic effects. Collectively, these results illustrate that blackcurrant concentrate health benefits can be delivered to food systems via milk protein ingredients-based encapsulates