Valorizing apple pomace as stabilizer of olive oil-water emulsion used for reduction of saturated fat in biscuits

The potential application of apple pomace emulsions (APEs) as saturated fat replacers in biscuits was investigated by employing olive oil/water (35/65) emulsions enriched with 12.5–20.0% apple pomace residue (AP) and exploring their rheological properties and microstructure. A selected APE (with 15% AP) was used as margarine replacer in biscuits at 50–100% substitution levels and the biscuits quality attributes were examined using a multi-instrumental analytical approach; a full-fat biscuit (30% margarine) was tested as control. Firmness and spreadability work of APE, evaluated by large deformation mechanical testing, increased with increasing AP content. The elasticity and viscosity of the control biscuit dough as determined by rheometry were higher than their reduced-fat counterparts with APE. With increasing APE substitution level, the moisture and water activity increased, and a lower biscuit color lightness was noted, whereas the thickness did not significantly differ among the tested product formulations. Moreover, fracture strength, total phenolic (3,4-dihydroxybenzoic acid being predominant) content and antioxidant activity were greater for the APE-fortified biscuits than the control. SPME/GC–MS analysis revealed the presence of AP-derived volatile compounds, providing pungent, rancid and fruity notes in the APE-fortified biscuits. Nevertheless, the 50% margarine substituted biscuit received acceptable ratings for flavor notes, hardness, fragility and overall acceptability upon sensory evaluation. Slower rates of lipolysis (on biscuit weight basis) were also observed for the APE-fortified biscuits using an in vitro intestinal enzymatic digestion protocol. Overall, the APE appeared as an effective solid fat substitute in biscuits that improves their nutritional characteristics, while maintaining acceptable quality attributes.