Impact of Pre-Acidification with Organic Acids on the Physicochemical, Microbiological, Rheological and Sensory Properties of Ras Cheese Made from Cow Ultrafiltered Milk

This study examined the impact of pre-acidification, aimed at reducing the high buffering capacity of ultrafiltered (UF) cow milk, on the quality of Ras cheese during a 90-day ripening period. Pre-acidification was achieved using food-grade lactic, acetic, and citric acids. Five treatments were produced: a control with fresh milk (C1), a UF milk control without acidification (C2), and three UF milk treatments acidified to pH 6.00 using lactic (T1), acetic (T2), or citric acid (T3). Comprehensive assessments were conducted for physicochemical, microbiological, textural, and sensory characteristics. Among the treatments, T1 (lactic acid) exhibited the most notable improvements, including higher moisture content, elevated protein levels, and an increased ratio of water-soluble nitrogen to total nitrogen (WSN/TN). Ras cheese treatments produced from acidified UF milk showed a marked pH reduction compared to controls, with T1 recording the lowest pH and highest free fatty acid (FFA) content, reflecting improved lipolysis and flavor development. Texture profile analysis confirmed that T1 exhibited superior textural properties, particularly in hardness and cohesiveness. Microbiological results revealed T1 had the highest lactic acid bacteria (LAB) counts and the lowest levels of spoilage organisms. Sensory evaluation revealed that T1 and T2 closely matched the control (C1) in flavor and overall acceptability, with no significant differences. These results highlight lactic acid pre-acidification as a promising strategy to improve UF Ras cheese quality.