Microencapsulation of Saffron Aqueous Extract by Two Methods of Spray Drying and Freeze Drying with the Aim of Using in Drinks

Nowadays, according to the growing concerns of using synthetic colors in food, the use of natural pigments is of particular importance. Saffron crocin is one of the valuable natural coloring compounds with favorable coloring properties, which is subjected to decomposition and destruction more than other water-soluble carotenoid pigments due to its high degree of unsaturation. For the purpose of oxidative stability of compounds such as crocin, methods such as encapsulation are important to preserve it during processing. Due to its high solubility and low viscosity, maltodextrin is one of the most important and widely used carrier compounds used in the drying process of fruit and vegetable extracts. In this research, maltodextrin was used as a carrier for encapsulation of the effective compounds of saffron by spray drying and freeze-drying methods, and the physicochemical characteristics of both types of powder obtained were compared with the control sample.
 
Sargol saffron was purchased from Mashhad market and maltodextrin (DE = 18-20) was obtained from Sigma company. For extraction, ground saffron was mixed with distilled water in a shaker incubator for 16 hours, and then the mixture was placed in a rotary evaporator at 55 degrees Celsius for concentration. In order to prepare encapsulated samples, 10% maltodextrin was first prepared and mixed well with 250 ml of aqueous saffron extract. Then, the prepared solutions were dried with a spray dryer at an inlet air temperature of 180 degrees Celsius and a feeding pump speed of 10 ml/min, and once again using freeze dryer. The control sample without maltodextrin coating was also freeze-dried. After preparing the treatments, moisture, water activity, mass density, determination of effective saffron compounds, solubility, total anthocyanin content was performed on them and finally, saffron syrup was prepared with the formula of 1% powder of each sample and 4% sugar for sensory evaluation by the method of 5 hedonic points.
 
The results showed that the amount of moisture and water activity of the powders prepared by freeze drying method was significantly lower and was 2% and 0.15 respectively (P<0.05). Also, the effective ingredients of the control sample were more than the encapsulated samples by spray drying and freeze-drying methods, and the freezing samples retained higher crocin and picrocrocin than safranal. On the other hand, the higher density (202 kg/m3) of the control sample and its lower solubility (85%) were significantly evident among the treatments. The amount of total anthocyanin in the control sample was the highest (172 mg/100gr), and the encapsulated sample using the freeze-drying method retained higher anthocyanin than the spray drying method. The sensory evaluation of the prepared syrups also indicated a better general acceptance of the syrup prepared with frozen sample compared to the syrup prepared sprayed sample.
 
In general, in this research, the amount of moisture in the samples dried by spraying and freezing methods was significantly reduced compared to the control sample. Also, the amount of moisture and water activity in the freeze dryer's samples was lower than the spray dryer. The effect of the encapsulation method on the bulk density was significant, so that with the addition of maltodextrin, the bulk density decreased in both samples, and this reduction was greater in the frozen sample than in the sprayed sample. The amount of solubility in the samples dried by both methods was almost the same. The amount of anthocyanin in the freeze-dried sample was higher than that of the spraying method, and this difference was significant. Finally, the sensory evaluation results showed that in all parameters, evaluators gave a higher score to the drink sample with powder dried in a freeze dryer. In general, it can be said that in this study, the encapsulated samples obtained by freeze drying method had more suitable characteristics than the samples obtained by spray drying method.