Effects of Ultrasound Pretreatment Temperature on the Quality Evaluation of Dehydrated Soy Cheese Made from Soymilk

Soy cheese locally known as Beske is a protein-rich product made from soymilk but is highly perishable with limited shelf life. This study aimed to evaluate the effects of ultrasound pre-treatment on the quality of dehydrated soy cheese to improve its nutritional, functional, and storage properties. Soymilk was processed into soy cheese, pre-treated using ultrasound, and dehydrated at varying temperatures (50°C, 60°C, 70°C, and 80°C). The samples were analyzed for proximate composition, phytochemical content (phytate and oxalate), physicochemical properties (pH, colour), functional properties (water holding capacity, swelling index), microbial count, and sensory attributes. Results revealed that ultrasound pre-treatment significantly enhanced nutrient retention, reduced microbial load, improved functional properties, and preserved sensory quality of the dehydrated Beske across all drying temperatures, particularly sample U-DSC C (pretreated and dried at 50°C and 60°C) where samples showed lowest moisture content (51.07%) and retained the highest level of crude protein (18.99%) compared to untreated control sample. The U-DSC C showed high water holding capacity (2.50%) and swelling capacity (3.59%) which may attributed to ultrasound pretreatment and low drying temperature. U-DSC sample also showed low pH (6.14) indicating acidity, low phytochemical (oxalate 8.93mg/100g; phytate 12.34mg/100g), low microbial count at the end 192 hours (bacteria; 34cfu/g and fungi; 16.00cfu/g) and low peroxide value and free fatty acid at the end of 192 hours (P.V; 1.87% and FFA; 2.14%) compared to there counter parts. Sensory evaluation showed that ultrasound pretreated samples, particularly U-DSC C, were most preferred in term of appearance, taste, texture and overall acceptability. The study concludes that ultrasound pre-treatment is an effective non-thermal technique for enhancing the drying efficiency and overall quality of soy cheese. These findings provide a scientific basis for promoting dehydrated Beske as a shelf-stable, high-protein food product with improved consumer appeal and commercial viability.