Dehydration Kinetics and Changes of Bioactive Compounds of Tulip and Poppy Petals as a Natural Colorant under Vacuum and Oven Conditions

The aim of this study was to investigate the drying kinetics and thermal degradation of anthocyanin and other phenolic compounds of tulip and poppy petals, as potential source of natural colorant, under both oven and vacuum drying processes at 45, 55 and 65C. The novelty of the study is to be the first attempt on the anthocyanin degradation and drying characteristic of tulip and poppy petals during drying process. Drying rate in vacuum drying was greater than that of oven drying. Drying characteristic of the petals was described by selected six thin layer models. Midilli–Kucuk model was found to be the best model (R² > 0.99). Vacuum drying at 55C was the best suitable drying condition for the preservation of anthocyanin content. Total color differences (ΔE) significantly changed, depending on the drying temperature. Lowest ΔE values were obtained in samples dried at 45C for tulip petals and at 65C for poppy petals. PRACTICAL APPLICATIONS: Color is one of the most important food quality parameters in the food industry, and both natural and synthetic food colorants are used in the food industry. In recent years, trend for use of natural food colorant has increased due to the negative effects of synthetic colorants on health. Because tulip and poppy flowers are rich in anthocyanin and antioxidant compounds, they have potential use as a natural food colorant. However, these plants are perishable and should be dried immediately in order to prevent fungal deterioration. The stability of anthocyanin and the color of these plants are affected by several factors such as temperature, oxygen, and enzymatic and nonenzymatic reactions during the drying process. Therefore, selection of the most favorable drying condition may be crucial in terms of decreasing loss of the anthocyanin during the drying process.