Optimization of Microencapsulation of Pomace Apple Extract and Evaluation of its Antimicrobial Properties in the Food Model (Oily Cake)

The present study was carried out with the aim of optimizing the use of apple pomace as an agricultural residue and apple juice factories. To achieve this, pomace apple extract was extracted using the subcritical water method (extraction temperature of 137 C, extraction time of 29.91 minutes, and water to pomace ratio of 31 ml/g), and the product was coated using different walls (maltodextrin with dextrose equivalents of 7 and 20, and pectin) and the freeze-drying method. The design of the wall composition was done using the software of the response surface and one-way network design with augmented axial points in mixture design(14 mixture walls). Evaluation of the physicochemical properties of microcapsules (moisture content, yield of microencapsulation, total phenolic compounds, strength of the antioxidant component) showed that using a mixture of maltodextrin and pectin walls at the central point of the triangular design (33.33 %) improved physicochemical properties more than the walls alone. Optimizing the concentration of different walls for microporous pomace apple extract using numerical optimization and optimization diagram showed that the optimal wall composition contains 33.41% of maltodextrin wall with dextrose equivalent 7, 35.84% of pectin and 30.75% of the maltodextrin wall with dextrose equivalent 20, dextrose. Also, the effects of free extract (with a concentration of 300 mg/l) and microcapsulated extracts with mixing the optimal walls (with concentrations of 3000 and 4500 mg/l) compared with the addition of synthetic preservative of potassium sorbate (100 mg/l) and the control sample (without any additive substance) on the sensory properties (aroma or taste, smell, and overall acceptance), total phenolic and microbial contamination (the total number of mould and yeast) of oily cakes were evaluated. The results showed that the pomace extract was able to control the growth of mould and yeast by maintaining the sensory and phenolic characteristics in the oily cakes, and the lowest growth of yeast and mould after 9 days of storage in environmental conditions was observed in samples containing 4500 mg/l microcapsulated extract that was approximately equivalent to the effect of the chemical preservative potassium sorbate (100 mg/l).