Using grape pomace powder as a pectin replacer to prepare low water activity bake-stable fruit filling

Grape pomace is the main by-product of grape processing industries which is a good source of hydrocolloids such as pectin and fibers. The possibility of substitution of pectin with the grape pomace powder (GPP) in a fruit filling was evaluated. In terms of rheological point of view, the more GPP content, the more elastic and viscose modulus, loss tangent and the complex viscosity were observed. The closest treatment to the Control sample (0.5 g high-methoxyl pectin), statistically (p < 0.05) was seen to be T3 (7.5 g GPP). The obtained results from confocal laser scanning microscopy (CLSM) and the fluorescence microscopy assays were in agreement with the rheological tests. Moreover, the outcomes of the extrusion test revealed that not only increasing the amount of GPP has a direct correlation with the force and total work, but also, after the exposure of filling to heat, Control, T3 and T4 (10 g GPP) showed bake stability features and their physical characteristics before baking had no significant difference (p < 0.05) with their features after baking.