Effect of Heat Treatment on the Vitamin C Content of Freshly Squeezed Orange Juice in Oyo State

Orange juice is one of the most commercially significant fruit beverages in South West Nigeria, valued primarily for its vitamin C content and refreshing sensory attributes. Industrial heat treatment is widely applied for microbial stabilisation, but its effects on vitamin C in juice from locally grown varieties in Oyo State have not been systematically evaluated. This study investigates the effect of pasteurisation at 72 degrees Celsius for 15 seconds and sterilisation at 121 degrees Celsius for 5 minutes on the vitamin C content, pH, titratable acidity, total soluble solids, total phenolic content, and sensory quality of freshly squeezed juice from Pineapple sweet orange (Citrus sinensis) and Washington Navel orange, both sourced from orchards in Ibadan and Ogbomosho. Vitamin C was quantified by titrimetric and spectrophotometric methods. Results showed that pasteurisation at 72 degrees Celsius retained 82 percent of initial vitamin C in Pineapple sweet orange juice compared to 61 percent retention following sterilisation. Sensory panellists of 30 trained evaluators rated pasteurised juice significantly higher for colour, flavour, and overall acceptability compared to sterilised samples. The study engages with recent thermal processing literature on ascorbic acid degradation kinetics and contributes to the optimisation of heat treatment for small-scale orange juice processing in Oyo State. Keywords: orange juice, pasteurisation, vitamin C, thermal processing, Oyo State