**4. Conclusions**

In this study, the phenolic content, flavonoid content, and the lipid-soluble antioxidant capacity of 14 byproducts obtained in the vegetable oil industry were measured. Results confirm that the byproducts analyzed are a good source of many biological functional substances having considerable amounts of total phenolic content.

For determining the antioxidant activity, DPPH, ABTS, FRAP, and CUPRAC methods were used. The ACL method was used for determining the antioxidant capacity. The samples showed varied antioxidant capacities depending on the seed origin. In all methods performed, the highest antioxidant capacity was for the grape seed flour. Walnut flour, sunflower meals, and rapeseed meals are an excellent source of antioxidant substances with high antioxidant capacity. The polyphenol content and the antioxidant capacity of the byproducts from the vegetable oil industry are influenced by the variety and the method of obtaining the waste. The flour of the analyzed byproducts has a higher antioxidant activity than meals and groats. Photochemiluminescence analysis and DPPH, ABTS, FRAP, and CUPRAC assays were fully applicable to the evaluation of the antioxidant capacity of lipophilic fraction of byproducts obtained in vegetable oil industry samples, with correlation coefficients of 0.9952, 0.9735, 0.9874, and 0.9930, respectively. The results indicate that byproducts obtained from the vegetable oil industry (flour, meal, and groats) could be an inexhaustible source of phenolic compounds, especially flavonoids, with antioxidant properties as valuable functional ingredients with beneficial effects on human health. The byproducts obtained from the vegetable oil industry can be used as ingredients for new bakery products to improve their nutritional properties and antioxidant quality. Further studies are needed to determine the optimal concentration of the byproducts' addition into wheat flour in order to achieve an improvement in the nutritional and sensory properties and to increase the antioxidant capacity of the bakery products.

**Author Contributions:** Conceptualization, N.B.; methodology, M.M. and I.C.M.; software, M.M. and I.C.M.; validation, M.M. and I.C.M.; formal analysis, M.M., I.C.M. and I.E.S.; investigation, M.M., I.C.M. and I.E.S.; resources, N.B.; data curation, N.B. and M.M.; writing—original draft preparation, M.M. and I.C.M.; writing—review and editing, N.B.; visualization, M.M. and N.B.; supervision, N.B.; project administration, N.B.; funding acquisition, N.B. All authors have read and agreed to the published version of the manuscript.

**Funding:** This work was supported by a gran<sup>t</sup> of the Romanian National Authority for Scientific Research and Innovation, CCDI-UEFISCDI, project number ERANET-COREORGANIC&SUSFOOD-PROVIDE-1, within PNCDI III.

**Informed Consent Statement:** Not applicable.

**Data Availability Statement:** The data presented in this study are available on request from the corresponding author. The data are not publicly available due to privacy or ethical restrictions.

**Conflicts of Interest:** The authors declare no conflict of interest.
