ePoster Presentations

Delnavaz Yazdansepas, MSc. Student; and Derick Rousseau, Professor, Chemistry and Biology, Ryerson University, Canada

Research on dietary proteins has shown that they are precursors of a variety of bioactive peptides that can improve human health and prevent chronic diseases by exerting positive effects on the body’s digestive, cardiovascular, immune and nervous systems. As a preliminary step to investigate the role of dairy peptides on metabolic syndrome, the aim of this study was to formulate fat-free, high protein content model yogurts with different ratios of casein and whey proteins. The second aim was to subject the whey proteins to a heat treatment prior to yoghurt preparation. Model yogurts were formulated with 10 wt% protein at 1:1 and 4:1 casein: whey protein ratios using micellar casein and whey protein isolate (WPI). Other than the protein, the starting dairy blends consisted of 75 wt% water, 14 wt% lactose, and 1 wt% bacterial culture. Differential scanning calorimetry showed that WPI was susceptible to denaturation at 60 ˚C and above. As a result, the 1:1 hydrated dairy solutions were heated at 70, 75, or 80 ˚C for 27, 16, and 5 minutes, respectively. The samples were then inoculated and incubated at 42 ˚C. The firmness and microstructure of the resulting yoghurts were analyzed with oscillatory rheology and confocal laser scanning microscopy, respectively. The thermal treatment at 80 ˚C resulted in a yogurt with a firmer gel structure and a smaller pore size, along with a shortened fermentation time. This study serves as the foundation for future in-vitro and in-vivo trials to investigate the effects of yoghurts with different protein compositions on possible mitigation of metabolic syndrome.

Kunal Kadiya, Postdoctoral Fellow, Department of Food and Bioproduct Sciences, University of Saskatchewan, Canada and Supratim Ghosh, Associate Professor, Department of Food and Bioproduct Sciences, University of Saskatchewan, Canada

Disperse-phase induced gelation in emulsions can be achieved through either random jamming or the formation of a network of aggregated droplets. In nanoemulsions, random jamming could be induced at a lower oil-volume fraction (ɸ) by decreasing the droplet size (r) and increasing the interfacial shell-layer thickness (δ). In this study, two different primary nanoemulsions were prepared using either a low molecular weight emulsifier (Citrem) or polymeric whey protein isolate (WPI) (average droplet diameter was 200 nm). To increase δ, the second layer of oppositely charged polysaccharide (chitosan or pectin) was deposited on the monolayer Citrem or WPI-stabilized nanodroplets using one-step versus two-step layer-by-layer (LbL) electrostatic deposition techniques, respectively. Using the one-step LbL method, a liquid-like Citrem-stabilized monolayer emulsion was transformed into repulsive Citrem-chitosan-coated bilayer weak nanoemulsions gel, with significantly lower gel strength than the WPI-pectin bilayer strong nanoemulsions gel prepared using the two-step LbL method. Interestingly, the gelation in the bilayer nanoemulsions was obtained at a lower ɸ (0.21) compared to the monolayer nanoemulsions, where electrostatic and steric repulsive forces (from polysaccharide) significantly contributed to elevating δ and effective oil volume fraction (ɸeff) of the nanodroplets. The deposition of the second layer, using the one-step and two-steps LbL method, also controlled lipase action during in vitro digestion leading to a significant reduction in lipid digestibility, compared to the monolayer nanoemulsions. Overall, the study showed that the dispersed-phase induced gelation at a lower ɸ and controlled digestion in bilayer compared to monolayer nanoemulsions were achieved by manipulating the interfacial composition and thickness using different LbL deposition methods. The fundamental knowledge developed from this research can be used to develop food-grade low-fat nanoemulsion gels with controlled digestion.