Bioactive Peptide-Enriched Requeson: A Functional Dairy Product From Whey Fermentation

Requeson, a traditional Mexican whey cheese, represents a promising avenue for the valorization of dairy by-products. However, its functional potential remains underexplored. This study evaluated the enhancement of bioactive properties in Requeson cheese through lactic acid bacteria (LAB) fermentation, comparing two monocultures (Lactobacillus delbrueckii subsp. bulgaricus NCFB 2772 and Streptococcus thermophilus SY-102) and a co-culture of both strains, cultured in sweet whey. Fermented whey was used to produce Requeson cheese, and peptide-rich extracts were analyzed for antioxidant activity (DPPH and FRAP), mineral-chelating capacity (Fe²⁺, Ca²⁺, Mg²⁺), enzymatic inhibition (ACE-I, DPP-IV), and antimicrobial activity against E. coli, M. luteus, and L. innocua. Liquid chromatography-tandem mass spectrometry (LC-MS/MS) was employed to identify peptides, and their potential bioactivities were predicted using the UniDL4BioPep platform. The co-culture fermentation yielded significantly higher values across all assays, including antioxidant capacity (41.3 mg Trolox), ACE-I inhibition (31.8%), DPP-IV inhibition (14.2%), and antimicrobial activity. Several peptides with predicted antioxidant, antihypertensive, antidiabetic, and antimicrobial properties were exclusive to the co-culture formulation. These findings suggest that LAB co-culture fermentation of sweet whey is an effective strategy to develop peptide-enriched functional Requeson cheese with health-promoting properties. This approach supports the sustainable use of dairy by-products and contributes to the advancement of functional dairy products in the bioeconomy.