Chemometric assessment of fermented dairy foods from bovine whey and goat milk

Agri-food systems are currently under increasing pressure to improve sustainability through the large-scale by-products recycling in line with circular economy and smart agri-food system principles. The main objective of this PhD project was to evaluate sustainable valorisation strategies for by-products originating from the dairy and winery supply chains, promoting their transformation from waste into high-value dairy fermented products.A main research topic focused on the recycling of (bovine) whey by the application of microparticulation followed by fermentation with the aim of developing a novel value-added fermented soft dairy cream. The effects of these bioprocesses were investigated using a multi-analytical approach, including gross chemical composition, fatty acid profile, supramolecular structural characterisation coupled with a multivariate statistical analysis. Microparticulated whey (MPW) and fermented MPW (FMPW) showed increased protein (0.7-8.8%) and fat (0.3-1.3%) concentration, and a change of colour tended to a brilliant yellowness. FMPW displayed a distinct fatty acid (FA) signature, with higher saturated fatty acid (SFA) and some selected polyunsaturated fatty acid (PUFA) such as C14:0, C18:1, C18:1 trans-11, C18:2 n-6, C18:3 n-6 identified as biomarkers of microparticulation and fermentative treatments. Despite unchanged protein profiles revealed by SDS-PAGE analytical method, supramolecular rearrangements into large aggregates were observed, resulting in a colloidal matrix with potential ball-bearing lubrication properties (Chapter 3).Furthermore, a non-targeted metabolomic assessment based on direct analysis in real time-high resolution mass spectrometry (DART-HRMS), combined with AIMS-based chemometric modelling, was applied to obtain a biochemical fingerprint and identify informative molecular biomarkers associated with whey recycling bioprocesses. Native whey and MPW showed elevated levels of hydroxyglutaric and malic acids, whereas FMPW resulted i a higher relative abundances of lactic acid, glucosamine, and histidyl-aspartic acid, together elevated levels of volatile compounds (tetradecanal, hexadecene and tetradecene) and fermentative end-products (diethyltartrate and histidyl-aspartic acid).Another main experimental issue explored the recycling of winery by-product through the inclusion of black grape pomace (BGP) in the diet of lactating Murciano-Granadina goats, and the related effects on milk and yogurt nutritional and rheological quality (Chapter 5). This strategy was evaluated as a smart recycling approach to reduce feeding costs while supporting the production of milk and suitable for yogurt manufacturing. The effects of diet replacement (12% on dry matter basis) of alfalfa hay with BGP was assessed on milk and yogurt gross composition, fatty acid profile, antioxidant capacity, microbiological quality and sensory characteristics. Moreover, the effect of refrigerated storage time was assessed to verify as the yogurt quality traits might changes during a 28-day period. Compared to the control diet, both in milk and yogurt, BGP significantly increased fat content and led to a decrease of the yellowness. The winery by-product affected yogurt FA profile given the increase of C18:1 trans-11 and total CLA isomers, and a decrease of PUFA n-3. An influence on yogurt sensory traits was also observed since BGP promoted a higher overall acceptance. The yogurt storage time did not affect any of the investigated quality traits. Summarizing, this PhD research highlighted that whey and black grape pomace can be effectively reintegrated into smart agri-food systems as nutrient-rich sources, supporting the claim that the tested whey bioprocessing and BGP recycling approach represents an affordable large-scale strategy for energy and nutrient recovery into fermented dairy products without compromising the perceived sensory quality of the final product.