The apple by-product is the remaining solid obtained after fruit processing, mainly constituted by insoluble dietary fiber. However, soluble dietary fiber would be more desirable due to its positive health effects. The simultaneous application of high hydrostatic pressure (HHP), namely at 200, 400, and 600 MPa, for 15 and 30 min holding time, and the commercial enzyme Celluclast® (92 EGU) allowed a high molecular weight carbohydrates solubilisation achieving therefore, a safe soluble dietary fiber-rich product. HHP facilitated the cell wall accessibility, as it was observed by scanning electron microscopy which revealed a considerable cell wall disruption; whereas, the food-grade enzyme activity led to a decrease of the soluble polysaccharides molecular weight (MW), mainly in the major MW polysaccharide, i.e. HHP-sample: 6.13*104 kDa; HHP + enzyme-sample: 4.26*104 kDa. The solubilisation is at the cost of the augmentation (p < 0.05) of mainly, glucose, uronic acids and arabinose. The soluble dietary fiber-rich product present greater water retention capacity, oil holding capacity, and emulsion activity, which increased more than eight times as compared to the control. These results support an enhancement of apple by-product technological and nutritional qualities, hence it could be utilised as a safe and effective functional ingredient.

This work has been carried out thanks to project “APHENZ” (AGL2016-77056-R) of the Spanish Ministry of Economy and Competitiveness (co-financed by AEI, FEDER EU fund). The technical help of D. Gómez (SEM) and R. Dominguez (HHP) is acknowledged. Rocío Teresa Jiménez de la Peña Armada is grateful to Rafael Folch Foundation for her PhD grant (2020/E02).

Peer reviewed