Integration of Annurca apple peels into wheat crackers through the co-formulation with lemon fibres: focus on physical quality and phenolic recovery

Apple peels are an underutilized by-product and a rich source of dietary fibres and phenolic compounds, thus enhancing as a dried ingredient the nutritional profile of baked goods. However, phenolic compounds, on baking, can degrade and lose their potential health benefits. Remarkably, the interaction between dietary fibres and phenolic compounds is well documented. In this sense, the binary combination within bakery formulation of apple peels and different sources of dietary fibres could represent an effective strategy to mitigate polyphenol thermal degradation. The present research investigates how co-incorporating Annurca peel powder (APP) and different lemon polysaccharides (as a source of soluble and insoluble fibres) may affect the nutritional and physical properties of low-moisture bakery products, such as crackers. It examines how lemon polysaccharides influence the recovery of apple peel polyphenols during baking, potentially improving their retention in crackers. APP inclusion did not affect the texture of the crackers, whereas insoluble lemon fibres increased the breaking force as opposed to pectin. A non-targeted analysis of the phenolic profile of APP via UHPLC-ESI-QTOF-MS/MS revealed 59 compounds, with flavonols being the most abundant. Baking led to anthocyanin loss but increased the recovery of hydroxybenzoic acids. Notably, co-formulating with lemon polysaccharides (both soluble and insoluble) helped preserve flavonols. Dihydrochalcone, hydroxycinnamic acids, and flavan-3-ols recovery improved with pectin addition, while proanthocyanidin content decreased with either lemon insoluble polysaccharides or pectin addition. This study demonstrates that it is possible to achieve greater stability of apple phenolic compounds in low-moisture baked goods through co-formulation with lemon polysaccharides.