Liquid Milk Products | Liquid Milk Products: Super-Pasteurized Milk (Extended Shelf-Life Milk)

Abstract

Extended shelf life (ESL) or superpasteurized milk refers to a fluid milk product that has a shelf life significantly greater than that of conventionally pasteurized milk (e.g., 45 days for ESL vs. 15 days for conventionally pasteurized), yet does not have pronounced cooked or scorched off-flavors typical of shelf-stable ultrahigh-temperature milk. ESL milk must be stored under refrigeration. The two- to threefold greater shelf life over conventional milk enables ESL milk to meet extended shipping and storage demands. Both direct and indirect systems are used to heat milk in ESL operations with typical heat treatments in the range of 125–145 °C for 2–4 s. ESL milk is packaged using aseptic filling technologies to control postprocess microbial contamination. Factors affecting the shelf life of ESL milk include the chemical, physical, and microbial quality of the raw milk, sanitation practices during processing, and the presence of thermoduric microflora or heat-stable enzymes such as plasmin. Typical forms of off-flavor development in ESL milk may include thermal degradation reactions, light- or metal-induced oxidative deterioration, gelation due to enzymatic or thermal alteration of the protein fraction, and microbial spoilage of lipid, protein, or lactose components.