effect of type and concentration of wall material on microencapsulated saffron color compounds by freeze drying

saffron is an important spice values for its color, aroma and flavor in the food industry. a significant proportion of saffron compound is lost during processing and storage because of its volatility and sensitivity to oxidation. thepresent research microencapsulated saffron color compounds (crocin) by freeze drying. the freeze-dried aqueous saffron effective compound extract was first prepared and then solutions of 5%, 10% and 15% polyvinylpyrrolidone (pvp40) and maltodextrin (mdx, dextrose equivalent: 16.5-19.5) containing 250 mg of the freeze-dried aqueous saffron extract were prepared. the solutions were dried in a freeze dryer. the characteristics of the microcapsules (yield of microencapsulation, color remaining, bulk density, glass transition, microstructure, release speed of color compound) were evaluated at 75% humidity at room temperature (25°c) after 45 d of storage. the results showed that the crocin content of microcapsules prepared with pvp40 were higher than for those prepared with mdx. the color of the saffron compounds decreased as the wall concentrations increased from 5% to 15%. the glass transition for all samples was greater than ambient temperature. the glass transition of pvp40 was greater than that of mdx. the structure of the microcapsules was laminated and flaked. after 45 d of storage, the crocin content decreased, but the microcapsules with pvp40 had 10% higher preserved color than the other samples.