Comparison of total phenolic content in organic and conventional carrot under different drying conditions using non-destructive analysis techniques

Abstract

Current evidence indicates that the higher nutritional value of organic foods, compared to their conventional counterparts, significantly impacts consumer demand. However, the application of thermal processes during processing may lead to a loss of nutritional values, including total phenolics and antioxidants, thereby failing to meet consumer expectations. Phenolics, known as some of the most potent natural antioxidants and are typically assessed through biochemical tests based on the concentration and reactivity of antioxidant compounds. However, the extraction methods can affect the accuracy of phenolic content measurement. In this study, the total phenolic (TP) (mg/100 g) capacity of fresh, hot air (HA)-dried, and intermittent microwave (IMW)-dried organic and conventional black carrots were compared, and the detectability of these compounds using a colorimeter and FT-NIRS was evaluated. PLSR models developed for estimating the TP content using FT-NIRS resulted in successful outcomes (IMW: R²_val = 0.78, RMSEP = 51.4 mg/100 g; HA: R²_val = 0.70, RMSEP = 63.0 mg/100 g). The highest prediction accuracy was achieved with drying treatments at 300 W (R²_val = 0.95, RMSEP = 5.1 mg/100 g) and 450 W (R²_val = 0.83, RMSEP = 50.7 mg/100 g), as well as at 80 °C (R²_val = 0.90, RMSEP = 21.0 mg/100 g). The drying methods significantly influenced the TP content and the accuracy of TP prediction in samples. Additionally, organic carrots contained a higher level of total phenolic compared to conventional.