Reproducing high mechanical load during industrial processing of ultra-high-temperature milk: Effect on frothing capacity.

In this study, possible reasons for an increased level of free fatty acids (FFA) in UHT-treated full-fat (3.5% wt/wt) milk and its effect on the frothing properties of milk were investigated. Lipolysis of raw milk from 2 different breeds of cattle (Holstein and Jersey) was induced by mechanical stress and kinetics of lipolysis were compared. Frothing capacity and foam stability of shelf-stable milk with different concentrations of FFA were determined, with a good to medium initial foam volume for up to 4 mEq FFA·(100 g of fat) fat and poor foam stability with >2 mEq FFA·(100 g of fat). A combination of mechanical stress and initial condition of fresh raw milk was found to trigger lipolysis and potential sources of mechanical stress during milk processing were identified.