Upcycling cheese whey in dulce de leche: impact on product properties and technological challenges

Abstract

The dairy industry faces increasing pressure to adopt sustainable practices, including the valorization of by-products such as cheese whey. This study investigated the technological feasibility of producing dulce de leche (DL) by partially replacing milk with sweet cheese whey at levels of 0%, 20%, 40%, and 80% (v/v). The impact on process kinetics, physicochemical properties, Maillard browning, microstructure, and texture was evaluated. Results indicated that whey substitution significantly reduced process yield (from 34.2% to 23.3%) due to lower initial solids. While pH and water activity remained stable for microbial safety, the Maillard reaction was progressively inhibited, leading to a markedly lighter color (lower Browning Index) as substitution increased. Furthermore, high substitution levels promoted extensive lactose crystallization during storage at 4°C, resulting in a sandy texture. Instrumental texture analysis revealed that whey incorporation increased hardness and adhesiveness while decreasing the penetration area ratio, particularly at the 80% level. It is concluded that a 20% whey substitution level is technologically viable, yielding a product with acceptable stability and texture during the evaluated storage period, without requiring additional additives or complex processing steps. These findings suggest that the 20% formulation could represent a straightforward, low-cost alternative potentially adoptable by small-scale dairies for whey valorization, although further validation at pilot scale and with sensory consumer testing is needed. In contrast, substitution levels of 40% and above necessitate adjunct technologies such as enhanced lactose hydrolysis, incorporation of crystallization inhibitors (e.g., hydrocolloids), or optimized cooling regimes to mitigate defects.