Evaluation of color quality and stability in celeriac slices dried by hot-air and vacuum using multivariate analysis

Physicochemical changes occurring during drying, especially affecting color attributes, structural integrity, and nutrient stability, remain critical factors influencing the final food quality. Although many drying studies focus on various vegetables, limited information exists regarding color alterations in celery, a plant with aromatic, medicinal, and functional food properties, under different drying conditions. This study was conducted to comparatively evaluate the effects of hot-air drying at 65 °C and vacuum drying (hot-air at 65 °C combined at 100 mm Hg) on the color parameters and visual quality of celeriac samples. Additionally, Principal Component Analysis (PCA) and Soft Independent Modeling of Class Analogy (SIMCA) analyses were conducted using color models. The results demonstrated that significant differences in L*, a*, b*, C*, and h values between fresh and dried samples depending on the drying method (p < 0.05). Hot-air drying led to a pronounced decrease in L*and b* values and noticeable darkening of the food due to oxidation reactions. In contrast, vacuum drying effectively minimized oxygen exposure and thermal damage, thereby preserving color quality at levels close to that of the fresh sample. The negative a* values observed in both fresh and vacuum-dried samples reflected the naturally light tones of celeriac, while the positive shift in a* values after hot-air drying indicated pigment degradation. Vacuum drying provided better preservation of color pigments. PCA, applied using the L*a*b*, L*Ch, and L*a*b*Ch color models, successfully distinguished the samples according to drying methods. PCA explained more than 95% of the variance, demonstrating its effectiveness in differentiating the effects of drying on color parameters. Furthermore, the SIMCA analysis revealed that celery slices obtained through different drying methods could be classified based on their color data with 100% accuracy. Present study highlights the superiority of vacuum drying in preserving the color quality of celeriac and offers valuable insights for the food industry in maintaining sensory and functional quality during drying processes.