Optimization of encapsulation and spouted bed drying of saffron petal extract and evaluation of its thermal stability in natural pomegranate juice

Saffron petals, a by-product containing anthocyanin pigments, can serve as a natural food colorant. This study aimed to optimize the drying of encapsulated saffron petal extract (ESPE) using a spouted bed dryer (SBD). Then, the thermal stability and durability of the optimal ESPE powder were examined in natural pomegranate juice with a slight red color (SRPJ) or with a low level of total monomeric anthocyanin content (TMAC). The extraction of phenolic compounds from saffron petals was carried out using an acidic ethanol solvent, followed by the concentration of the extracted solution using a vacuum rotary evaporator. The concentrated extract was mixed with wall materials (maltodextrin (MD) and gum Arabic (GA)) and dried in the SBD. Box–Behnken factorial design of response surface methodology (RSM) was used to optimize key parameters screened by Plackett–Burman design. The resulting ESPE powders were evaluated in terms of TMAC, color indices, and thermal stability. The findings revealed that the pH of the extracted solvent, drying temperature, and the ratio of wall materials significantly affected the TMAC and color indices of the powders. Under optimal conditions (pH of 2, temperature of 70 °C, and MD:GA of 85:15 w/w) the TMAC, L*, a*, and b* values were 864.78 mg/L, 66.09, 53.3, and − 6.31, respectively. The desirable stability of the anthocyanins and color indices of the ESPE powder in the model juice during heat treatment and storage periods underscores its potential application and highlights the need for further exploration of this by-product for use in various foodstuffs.