Optimization of extraction and microencapsulation of anthocyanin pigments extracted from red onion peel and red cabbage

Anthocyanins are very useful and they can be considered as a proper option for using as a food dye in production of various foods due to the wide range of colors and antioxidant properties. In this study, the effect of parameters such as solvent (acidic ethanol with Hcl 1.5N, ETHANOL 80%), solvent/solid ratio (10, 15, 20), temperature (30, 40, 50), time and (dark/light) on anthocyanin extraction from the peel of red onion and red cabbage were investigated using solvent method. FFD model was used to determine the optimum extraction conditions. The results indicate that the maximum amount of extraction from the peel of red onion and red cabbage are respectively in operating conditions such as acidic ethanol with HCL 1.5 normal (15:85), 80% ethanol and temperate of 31.58, 35.88 °c and the time of 18.32, 3.4 hours, and the solvent/solid ratio equal to 18.65, 18.04 (volume/mass) in a dark environment. In order to increase the stability of produced liquid color against environmental factors, microencapsulation was done through freeze drying method with Arabic gum and maltodextrin. According to the results of TGA test and DSC tests, Arabic gum has more resistance against the heat so that the initial decomposition temperature of encapsulated powders with this coating material for the peel of red onion and red cabbage are increased from 63.82 to 250.87 centigrade degree and from 81.03 to 263.64 centigrade degree respectively. The average of particle size of encapsulated powders are smaller with maltodextrin and equal to 6.1 and 21.5 micrometers respectively. X-ray diffraction indicates that the structure of encapsulated powder is amorphous.