The impact of ultra-high pressure homogenization (UHPH) (175 and 300 MPa, 1 and 4 passes) on the structure of egg yolk granule was evaluated to improve the techno-functional properties of the proteins. The UHPH treatment destabilized and modified the structure of egg yolk granule proteins, which was validated by protein profiles from gel electrophoresis. A decrease of free thiol and an increase of disulfide bond content was correlated with a decrease of the surface hydrophobicity, specifically at 300 MPa with 4 passes. The structural modifications induced by UHPH, mainly at 300 MPa (1 and 4 passes), improved the water and oil binding capacities of egg yolk granules with values ranging from 1.30 to 1.55 gwater/ggranule and 3.34 to 3.73 goil/ggranule, respectively as well as their stability index. However, egg yolk granule solubility was not impacted by the application of UHPH. These new insights are key to supporting the development of new egg yolk granule-based ingredients for the food industry.

Ultra-high pressure homogenization (UHPH) is a promising method for destabilizing and potentially improving the techno-functionality of the egg yolk granule. This study's objectives were to determine the impact of pressure level (50, 175 and 300 MPa) and number of passes (1 and 4) on the physico-chemical and structural properties of egg yolk granule and its subsequent fractions. UHPH induced restructuration of the granule through the formation of a large protein network, without impacting the proximate composition and protein profile in a single pass of up to 300 MPa. In addition, UHPH reduced the particle size distribution up to 175 MPa, to eventually form larger particles through enhanced protein-protein interactions at 300 MPa. Phosvitin, apovitellenin and apolipoprotein-B were specifically involved in these interactions. Overall, egg yolk granule remains highly stable during UHPH treatment. However, more investigations are needed to characterize the resulting protein network and to evaluate the techno-functional properties of UHPH-treated granule.

The effect of RO concentration on microbial ecosystem changes and the chemical composition of white wastewaters (WW; dairy effluents generated during the hydraulic flush of dairy processes), recovered from two dairy plants (A and B), was evaluated. The WW of dairy plant A was dominated by psychrotrophic bacteria, but no increase of the total number of 16S rRNA genes in the retentate throughout RO was obtained. A thermotolerant lactic acid bacteria genus, Streptococcus, was the most abundant genus in the initial samples of WW from dairy plant B. During WW recirculation in the RO system, the total number of 16S gene copies in the retentates generated by plant B increased significantly after 15 h. An adapted RO treatment with specific parameters is proposed to limit the growth of problematic bacterial genera, so promoting revalorization and reducing the environmental impact of WW dairy effluents.

The dairy industry produces large amounts of wastewater, including white and cleaning wastewater originating principally from rinsing and cleaning-in-place procedures. Their valorization into process water and non-fat milk solids, in the case of white wastewater, or the renewal of cleaning solutions could be achieved using pressure-driven membrane processes. However, it is crucial to determine the intrinsic characteristics of wastewaters, such as proximate composition and bacterial composition, to optimize their potential for valorization. Consequently, white and cleaning wastewaters were sampled from industrial-scale pasteurizers located in two different Canadian dairy processing plants. Bacterial profiles of dairy wastewaters were compared to those of tap waters, pasteurized skim milk and unused cleaning solutions. The results showed that the physicochemical characteristics as well as non-fat milk solids contents differed drastically between the two dairy plants due to different processing conditions. A molecular approach combining quantitative real-time polymerase chain reaction (qPCR) and metabarcoding was used to characterize the bacteria present in these solutions. The cleaning solutions did not contain sufficient genomic DNA for sequencing. In white wastewater, the bacterial contamination differed depending on the dairy plant (6.91 and 7.21 log10 16S gene copies/mL). Psychrotrophic Psychrobacter genus (50%) dominated white wastewater from plant A, whereas thermophilic Anoxybacillus genus (56%) was predominant in plant B wastewater. The use of cold or warm temperatures during the pasteurizer rinsing step in each dairy plant might explain this difference. The detailed characterization of dairy wastewaters described in this study is important for the dairy sector to clearly identify the challenges in implementing strategies for wastewater valorization.