Postbiotics: the route from whey fermentation to functional beverages and food packaging materials

Fermented whey beverages are increasingly recognized as promising functional foods due to the presence of fermentation-derived bioactive compounds and, where appropriately processed, postbiotic preparations. Historically, whey was treated as a dairy waste stream and an environmental burden. However, it is a nutrient-rich cheese by-product containing lactose, proteins, vitamins, minerals, and other nutrients, and is therefore an excellent fermentation substrate. Consequently, whey can be effectively valorized for the development of value-added products, supporting circular-economy approaches through the sustainable utilization of dairy by-products. During controlled fermentation, selected microorganisms, such as Lacticaseibacillus , Lactiplantibacillus , Limosilactobacillus , Lactococcus , and Bifidobacterium , metabolize whey constituents and generate extracellular metabolites and bioactive compounds, while microbial biomass accumulates. When a postbiotic preparation is intended, the biomass is subsequently subjected to a defined inactivation step, with optional cell disruption to expose or recover microbial components, yielding a characterized postbiotic preparation. Fermentation-derived bioactive compounds include enzymes, teichoic acids, organic acids, bioactive peptides, bacteriocins, extracellular polysaccharides, and other substances, which enhance the functional benefits of fermented whey beverages. Although their properties are similar to those of probiotics, postbiotics exhibit improved stability, safety, and efficiency, making them more convenient for food applications. Evidence indicates that postbiotics derived from fermented whey exhibit antioxidant, antimicrobial, and anti-inflammatory properties, as well as the ability to modulate gut health. This review provides a cohesive overview of the formation, composition, and potential biological effects of postbiotic preparations generated from whey through controlled fermentation and subsequent inactivation and processing. It also examines the potential applications of whey-derived postbiotic preparations and fermentation-derived bioactive compounds in active food packaging systems. By summarizing the current knowledge and highlighting research gaps, this review emphasizes the potential value of fermented whey as a postbiotic-rich sustainable resource for the development of novel functional foods and active food packaging systems.