Comparative study on the effect of mild temperature conditions in fractionated sterilization of carrot juice on microbiological stability and sensory properties

Carrot juice is valued for its high vitamin and antioxidant content, necessitating gentle thermal processing to preserve these nutrients. Its slightly acidic pH value requires a two-step heating process, warranting optimization to enhance product quality and resource efficiency. This study investigated the impact of varying the first heating step between 100 and 130 °C on chemical, sensory, and microbiological parameters. While other chemical parameters remained stable, lactic acid content increased significantly from 55 to 1405 mg/L over downtimes, highlighting the influence of external factors that could not be influenced within the investigations. Lower heating temperatures compromised microbiological stability, with spore-forming bacteria (5 colony forming units per 20 mL) detected at just a 10 °C reduction. Sensory quality showed minimal change, with descriptive analysis identifying only 3 respectively 4 significantly different attributes out of 19 across the factors experimental parameter setting and technical repetition. The quality of raw materials had a more pronounced impact on sensory outcomes than the heating temperature. This study concludes that adjusting the first heating temperature has limited benefits for sensory quality but risks microbiological safety. Emphasis should therefore be placed on ensuring high-quality raw materials and consistent raw juice properties to maintain product quality.