Valorization of Brewer’s Spent Grain Liquid Fraction for the Development of a Pasteurized Strawberry-Based Blend Juice

Brewer’s spent grain (BSG), a by-product of the brewing industry with 70–80% moisture, produces a liquid fraction during dewatering that can be combined with strawberry pulp (SP) to create a new food product. This study evaluated the use of BSG liquid fraction as a dilution medium for SP to develop a novel blend juice (BJ) and assess its shelf life after pasteurization. The optimal formulation consisted of 70% BSG liquid fraction and 30% SP, pasteurized at 95 °C for 5 min (BJ5) and 10 min (BJ10), and stored for 8 weeks at 25 °C. Pasteurization caused no significant (p > 0.05) changes in moisture, color, chemical composition, microbiological quality, or sensory properties. Both BJ5 and BJ10 showed sensory attributes, overall acceptance, and purchase intent comparable to two commercial Chilean blend juices. During storage, color, chemical, and microbiological parameters remained stable, though moisture, soluble solids, pH, and total polyphenol content were significantly affected (p < 0.05). Both pasteurization conditions ensured microbiological stability throughout the 8-week period. Overall, the pasteurized BSG–strawberry blend juice demonstrated good preservation, sensory quality, and consumer acceptance, suggesting strong potential as a sustainable and appealing product for the food and gastronomy industries.