Comparative analysis of high-protein and lactose-reduced semi-skim yogurt production at different scales: Effects on lactic fermentation metabolites, physicochemical, microbiological and physical properties, and sensory characteristics

Abstract

Protein increase in yogurt is a topic of current interest in the dairy industry, in order to obtain products with better nutritional and sensory characteristics. The development of prototypes at laboratory scale allows experimentation to achieve the desired characteristics, but it is necessary to adapt manufacturing conditions at larger scales to corroborate the feasibility of the process and the maintenance of the features proposed in the design. In this work, physicochemical aspects (pH, titratable acidity, and global composition), lactic fermentation metabolites (lactic acid and volatile compounds) and physical properties (whey holding capacity, rheology, texture and microstructure), of a high-protein and lactose-reduced semi-skim yogurt manufactured at laboratory scale (LS) and pilot scale (PS), were compared. Also, a sensory analysis was performed on PS yogurt. Yogurt formula comprised semi-skim milk, skim milk powder and whey protein concentrate 35 %. A commercial β-galactosidase was used for lactose hydrolysis and added along with the starter culture. Protein (∼6.3 g 100 g⁻¹), lactose (1.4–1.8 g 100 g⁻¹), and lactic acid (1.3–1.7 g 100 g⁻¹) were similar for both LS and PS. The main differences in volatile compounds were detected for minority compound groups (aldehydes and esters). Some differences were found between LS and PS physical properties, attributed to differences in cooling/stirring conditions between manufacturing scales. A trained sensory panel detected high scores for yogurt's descriptors. The consumer sensory test revealed high acceptance and intention of purchasing of the product. Scaling up affected some yogurt parameters, and contributing factors were identified. Notably, the final product had improved nutritional properties and acceptable sensory qualities.