Gentle heating and extending shelf-life: Customized phase treatment for shelf-stable whole milk combining microfiltration with microwave and indirect ultra-high temperature heating

This study adapts the customized phase treatment (CPT) process to whole milk (3.5 g fat 100 g −1 ). The process aims for gentle heating with an extended storage stability of the CPT milk. Through microfiltration (0.1 μm pore size), heat-sensitive ingredients like whey proteins pass into the permeate. Ingredients that limit shelf-life like bacteria, spores, and plasmin remain in the retentate. For CPT whole milk, raw milk was separated into cream and skim milk which were pasteurized separately. Skim milk was microfiltered and the permeate was microwave heated ( ϑ = 120 °C, t = 4 s) to minimize the loss of valuable ingredients. The retentate was standardized (≈ 9 g fat 100 g −1 ) with pasteurized cream and homogenized before long preheating ( ϑ = 95 °C, t = 128 s) and indirect ultra-high temperature (UHT) heating ( ϑ = 140 °C, t = 4 s). CPT whole milk was compared to directly and indirectly UHT heated whole milk (3.5 g fat 100 g −1 ). Whey protein denaturation of CPT milk ranged between the two milk types. Directly UHT heated milk showed increased particle size and viscosity due to elevated proteolytic activity while CPT and indirectly UHT heated milk remained stable during 24 weeks of storage at 20 and 30 °C. There was no fat destabilization, increase in the free fatty acid content, or rancid off-flavor over storage that would indicate fat degradation. Therefore, the CPT process is a feasible alternative to UHT heating to produce shelf-stable whole milk.