Extraction of anthocyanin from carnation flowers and determination of its stability as a natural food colorant

The aim of this study was to investigate anthocyanin extraction from waste carnation flowers (Dianthus caryophyllus L.); stability and usage of obtained extract as a natural food colorant. On this aim, the anthocyanin contents of waste carnation cultivars named as "Osiris", "Radiant", "Euforia", "Hot Pink" and "Chateau", were determined. It was decided to use the purple-colored "Osiris" cultivar carnatian flower which was found to have a very high content (143.21 mg/kg dry flower) of total monomeric anthocyanin compared to the carnation flowers of the other cultivars. In order to obtain anthocyanin based colorant from carnation flower, an optimization study was carried out by forced convectional solid-liquid extraction and ultrasound assisted solid-liquid extraction methods. Anthocyanin was extracted from petals of waste carnation flowers by using ethanol, acidified with 0.1 N HCl. Optimization of extraction conditions were carried out by using response surface method according to Box-Behnken experimental design. Optimum conditions of extraction were determined by maximum total monomeric anthocyanin content. In this optimization study, none of the chosen variables and extraction methods showed any significant effect (p>0,05) on extraction yield. Thus, additional study was carried out and it was found that only variables showed significant effect on extraction efficiency were size reduction efficiency (p<0.001), ethanol ratio of solvent (p<0.05) and extraction time (p<0.001). Forced convectional solid-liquid extraction was selected as the extraction method and anthocyanins were extracted in a shaking water bath, set to 30 °C and 178 rpm. Optimum extraction conditions were determined as 1/20 solid-liquid ratio, 80% ethanol – 0.1 N HCl ratio, 3 times 5-second-Ultra-turrax treatment and 20 minutes extraction time. The extract, obtained by using optimum extraction conditions, was condensed to 10 °Bx via a rotary evaporator. It was determined that the amount of total monomeric anthocyanin content of the obtained extract was 404.13 mg cyanidin-3-glucoside/kg dry extract. Following that, wall material (maltodextrin-DE12) was added to the condensed extract to provide the final concentration of 20 °Bx. The final extract was then fed to spray dryer and freeze dryer to obtain powder food colorant. Some physical properties of the natural food colorants, obtained in liquid and powder form, were determined. For the spray-dried sample, powder yield was determined as 61.30% while water activity as 0.41, moisture content as 6.33%, solubility as 80.39%, bulk density as 244.19 kg/m3, turbidity as 14.85 NTU and colour values for L*, a*, b*, h° and C* as 55.38, 46.71, 6.28, 7.65 and 47.12, respectively. For the freeze-dried sample, powder yield was determined as 91.56% while water activity as 0.24, moisture content as 4.34%, solubility as 81.01%, bulk density as 500.10 kg/m3, turbidity as 14.95 NTU and colour values for L*, a*, b*, h° and C* as 47.07, 37.03, 5.66, 8.69 and 37.46, respectively. The stability of the natural food colorants, obtained in liquid and powder form, were investigated by using them in model food samples and compared to commercial anthocyanin-based liquid food colorant as a replacement. Sugar paste, ice-cream and carbonated beverage was prepared as model food sample with equal total monomeric anthocyanin content. It was determined that the values of total colour change were affected statistically by all sources of variation (colorant type, storage condition, storage time) and their interactions at the level of p<0.001. The sugar paste samples, prepared by liquid and powder colorant obtained from carnation flower, showed no significant difference among themselves while there was a significant difference between these two samples and the one prepared by anthocyanin based liquid food colorant. The values of total colour change of ice-cream samples showed significant difference at the level of p<0.05 depending on colorant type. The sugar paste samples, prepared by liquid and powder colorant obtained from carnation flower, showed no significant difference among themselves while there was a significant difference between these two samples and the one prepared by anthocyanin based liquid food colorant. Ice-cream samples prepared with liquid colorant obtained from carnation flower and anthocyanin based commercial food colorant showed no significant difference. Similarly, samples prepared with spray dried and freeze-dried powder colorants obtained from carnation showed no significant difference. However there was a significant difference between ice-cream samples prepared with liquid commercial food colorant and liquid colorant obtained from carnation flower.The values of total colour change of carbonated beverage samples were affected statistically by all sources of variation (colorant type, storage time) and their interactions at the level of p<0.001. The difference between carbonated beverage samples prepared with liquid colorant obtained from carnation flower and anthocyanin based commercial food colorant was significant. When added in suitable amounts, the liquid and powder colorants obtained from carnation flowers could be an alternative to anthocyanin based commercial liquid colorant for model foods. In addition, the degradation kinetic parameters of carnation flower anthocyanins were calculated. It has been determined that the temperature-dependent degradation of carnation flower anthocyanins occurs according to the first order reaction kinetics. The reaction rate constants (k) and half times (h) were determined for 70, 80, 90 and 100 °C as 0.42 x 10-3 min -1; 0.71 x 10-3 min-1; 1.68 x 10-3 min-1; 3.68 x 10-3 min-1 and 27.57 h; 16.31 h; 6.90 h; 3.14 h, respectively. The activation energy (Ea) of the reaction was determined as 78.37 kJ / mol.