Physical processes to maximize milk cream hydrolysis: effect on fat structure and enzymatic hydrolysis

Milk fat shows high potential for the generation of aromatic compounds. Enzyme-catalyzed hydrolysis is effective to produce these compounds, however the substrate structure can limit the reaction. Physical processes can be applied to overcome these limitations. Thus, this study evaluated the enzymatic hydrolysis of cow milk cream (CMC) pre-processed by ultrasound (US), high-shear dispersing (HSD), stirring (ST), low- or high-pressure homogenization (LPH or HPH), as well as the effect on CMC structure after physical processes. CMC (20% fat) was processed at 50 °C by US (15 and 30 min, 20 kHz and 38.4 W/L), HSD (5 min for 12,500 and 25,000 rpm), ST (4 and 8 min, 1200 W) and low (15 MPa) and high (40 MPa) pressure homogenization. After the processes, the CMC structure was evaluated by creaming process in a spectrophotometer, emulsion stability index (ESI) and microstructure using an optical microscope. To evaluate the hydrolysis of pre-processed CMC, lipase was added, and the reactions were carried out in a thermostatic bath at 50 °C for 300 min. During hydrolysis, the fatty acids concentration (FAC) was determined and the data were modeled to obtain the hydrolysis rate and the final FAC. The pre-treatments promoted an increase in the hydrolysis rate (up to ~4.2 times) and in the final FAC (increase of up to 361%). In ascending order, US< ST< HSD< homogenization (LPH or HPH) showed the best results. In addition, these treatments also promoted changes in the CMC structure. Specifically, the HPH and HSD processes showed a lower emulsion destabilization, higher ESI and smaller fat globule size. Thus, the effects on structure favored the enzyme action and accelerated the hydrolysis degree. Therefore, the application of physical methods can be an interesting strategy to enhance the hydrolysis of CMC to generate compounds of industrial interest.