Goat milk powders enriched with grape pomace seed extract: Physical and techno-functional properties

This study aimed to evaluate the physical (particle size and zeta-potential) and techno-functional properties (emulsifying and foaming) of goat milk powders enriched with grape pomace seed extract (TME), as promising food ingredients in the formulation of functional food. Attenuated Total Reflectance Fourier Transform Infrared (ATR-FTIR) and Raman spectroscopies, along with advanced chemometric tools were employed as well as Scanning Electron Microscopy (SEM) for analyzing TME powders. All powders exhibited a unimodal particle size distribution and zeta-potential values more negative than-36 mV. ATR-FTIR and Raman spectroscopies combined with principal component analysis (PCA) demonstrated distinct separation among skimmed goat milk (M), thermally treated skimmed goat milk (TM), and TME powders in different spectral regions (amide I, II, III, and fingerprint region). This separation resulted from the applied thermal treatment, the presence of phenolic compounds and their complexes with goat milk proteins, and the formation of Maillard reaction products. SEM analysis confirmed the different morphology and shapes of M, TM and TME powders. The 0.1% solutions of M, TM and TME exhibited good emulsifying properties (emulsion activity index and emulsion stability index) but showed poor foaming properties, except for the M sample. Solution concentrations higher than 0.1% for all samples (0.5% and 1.0%) displayed poor techno-functional properties. In summary, a schematic representation of the arrangement of casein micelles in 0.1% M, TM and TME samples, on oil/water and air/water surfaces was provided. The production of TME powders represents an innovative strategy for waste recovery in the production of functional food ingredients with good emulsifying properties.