Effect of the encapsulation method on the mechanical strength of pomegranate beads

Pectin is a hydrocolloid commonly used as a wall material for encapsulation, meantime using a filler such as starch can improve the retention in the matrix and control the release in specific places. The mechanical strength (MS) of beads is a determining technological parameter in food processing and also impacts sensory characteristics. This study aimed at producing pectin-starch hydrogel beads by ionic gelation process to carry pomegranate extract (PE), increase its stability, and protect the polyphenols. The encapsulation techniques were performed using pectin-starch solutions (solids content of 2.85%) with 20% of PE and different concentrations of PE from the external environment (0 and 20%). For the adsorption method (100% of PE) were used blank pectin-starch beads. After that, aiming to control the release of polyphenols, all beads were coated with chitosan. The total phenolic content (TPC) was determined by the Folin–Ciocalteu method and the compression measurements were performed using a universal texturometer. The highest polyphenol content was for beads obtained by adsorption (2960.26±26.92 mg/100 g of sample), while for the conventional method (without PE in the external medium) the value was about 7 times smaller (408.08±17.54 mg/100 g of sample). Despite being widely used to improve the phenolic compounds release control, during the coating, there was a loss of phenolic by leaching, reducing TPC in all samples. The increase in the PE concentration in the external environment resulted in a larger MS of the beads (4.65±0.18 N to conventional beads and 13.78±1.01 N to beads produced by adsorption), while the use of coating caused a reduction in this parameter. The higher TPC is proportional to the amount of extract available for incorporation into the biopolymer matrix and the degree of complexation with the phenolic compounds in the extract may have resulted in the formation of a more rigid and cohesive structure, demonstrated by the increasing values of MS. The adsorption technique proved to be more advantageous and controlled release studies, as well as its application in a food matrix, may prove its usage viability.