Green processing of sour cherry (Prunus cerasus L.) pomace: process optimization for the modification of dietary fibers and property measurements

Commercial processing of sour cherries generates a large quantity of pomace as an industrial waste, which can suitably be converted into value-added fiber-rich products by employing appropriate extraction techniques. In this work, an array of techniques [microwave (MW), high-pressure (HP), enzymatic and thermal treatments] was employed to improve the yield of soluble dietary fiber (SDF) in sour cherry pomace (SCP) by breaking down the insoluble dietary fiber into a soluble form, and characterizes by total phenolic content, antioxidant capacity and other property measurements. It was found that a combination of MW (850 W/60 s) and HP treatment (600 MPa/15 min) resulted in the maximum yield of SDF (63%). However, individually the MW-heating (44.6%) had an edge on extraction over the HP-treatment (21.9%). Micrographs of MW-HP-600 treated samples exhibited an array of disordered smaller particle fragments spread over the larger particles. HP treatment improved the water holding capacity from 10.12 to 11.76 g/g after 600 MPa treatment. The peak values of the solubility index (46.9 to 49.6%) achieved in the sample containing elevated SDF content (the combination of either MW and HP, or MW, EH, and HP). The optimized process produced the maximum total phenolic (5.39 mg GAE/g d.b.) and DPPH (9.94 mmol DPPH/100 g d.b.) contents in the treated pomace. The combination of microwave, enzymatic hydrolysis and high-pressure treatments can loosen the surface structure of SCP-DF, enhance hydration properties by exposing hydrophilic groups more, extract a higher amount of phenolic compounds providing antioxidant activity improvement besides increasing SDF ratio in SCP