## 4 Conclusions  
Apple pomace powder from cider by-products has proven to be a feasible ingredient for gluten-free bread manufacture, as results of physicochemical quality parameters were concurrent with those described previously in the literature. Moreover, apple pomace powder could make a remarkable contribution to the nutritional quality of gluten-free breads, providing higher amounts of certain micronutrients, which are key factors within a gluten-free diet. These conclusions could be extrapolated to other apple varieties used for cider or juice production elsewhere, if they hold similar raw characteristics. Adjusting the water content of apple-pomace-containing formulations has been confirmed as a necessary step when adding fiber sources to gluten-free formulations. This made it possible to achieve GF breads with 8% APP content, which is higher compared to those judged as optimum previously (at around 5%). Values in key physicochemical characteristics may suggest good acceptability (specific volume \(\geq\) 2.5 cm\({}^{3}\)/g, cohesiveness 0.538 \(\pm\) 0.030, springiness 0.751 \(\pm\) 0.033 and resilience 0.378 \(\pm\) 0.015). Further studies along this research line should entail sensory analysis to assess consumer acceptance and market analysis involving local producers in order to guarantee that a sustainable circular economy net is established.  
The following supporting information can be downloaded at: [[https://www.mdpi.com/article/10.3390/app12125934/s1](https://www.mdpi.com/article/10.3390/app12125934/s1)]([https://www.mdpi.com/article/10.3390/app12125934/s1](https://www.mdpi.com/article/10.3390/app12125934/s1)), Table S1: Pearson Correlation analysis results (correlation coefficients and \(p\) value) between APP or protein content, physicochemical and instrumental sensory attributes (color and texture).  
**Author Contributions:** Conceptualization, J.S., M.d.P.F.-G., M.A.B., V.N., E.S. and O.M.; methodology, J.M., I.L, V.N. and O.M.; formal analysis, L.C., J.M., I.L., M.d.P.F.-G., M.A.B., S.M. and O.M.; investigation, L.C., J.S., I.L. and O.M.; resources, M.A.B., V.N., E.S. and O.M.; writing--original draft preparation, L.C.; writing--review and editing, L.C., J.S., J.M., I.L., M.A.B., V.N. and O.M.; supervision, J.S., M.d.P.F.-G., E.S. and O.M.; project administration, E.S.; funding acquisition, J.S. and J.M. All authors have read and agreed to the published version of the manuscript.  
**Funding:** This research was developed within a project funded by the Department of Food Quality and Food Industries of the Basque Government (00025-IDA2019-38) and was possible thanks to a grant received for labor costs by the Department of Economic Development, Sustainability and Environment of the same institution.  
**Institutional Review Board Statement:** Not applicable.  
**Informed Consent Statement:** Not applicable.  
**Data Availability Statement:** Data available on request.  
**Acknowledgments:** The authors thank all the members and students at the GLUTEN3S research group who helped, in one way or another, with this work. We thank the Analytic Chemistry laboratory at the Central Service of Analysis in Araba-SGIker of UPV/EHU, as well, for technical and human support provided.  
**Conflicts of Interest:** The authors declare no conflict of interest. The funders had no role in the design of the study; in the collection, analyses, or interpretation of data; in the writing of the manuscript, or in the decision to publish the results.