**12. Conclusions**

The published literature has demonstrated the antioxidant properties of various naturally occurring compounds, such as quercetin, polyphenols, vitamins, and synthetic molecules including α-lipoic acid, N-acetyl cysteine, melatonin, gallic acid, lignin, captopril, taurine, and catechin; the free radical scavenging abilities predicted the potency of the antioxidants (hydrogen bonding within the ether O<sup>2</sup> atoms in peroxide radical) and the location of bulky tert-butyl functional groups. The extraction of antioxidants from agro-wastes generates high-quality phenolic antioxidants. On the downside, the benefits are offset by low yields and negative ecological effects, as well as synthesis-related tradeoffs between functionality, chemical stability, and biocompatibility. Other constraints are related to the chemical properties of the products—polyphenols exhibit poor membrane permeability, rapid metabolism, and poor bioavailability and UV degradation, despite free radical grafting [73], step growth, free radical, and enzyme-catalyzed reactions. A vast majority of research in antioxidant materials so far has been focused on the entrapment or encapsulation of low-molecular-weight and enzymatic antioxidant compounds in polymersomes, micelles, or nanoparticles that often exhibit poor long-term stability. The structural incorporation of antioxidant moieties in polymers or direct polymerization while maintaining their intrinsic antioxidant properties has been attracting increasing interest from the research community. Polymerized antioxidants can be produced through grafting or backbone incorporation, and offer the potential advantages of protecting the antioxidant from inactivation, delivering continuous antioxidant protection as long as the polymer exists, as well as a relatively high mass of antioxidant payload.

Potential industrial applications of antioxidants in the food production industry are diverse, especially in the forms of blends with bio-polyether (PEO), bio-polyester (PLA), and commercial starch-based polymer (Mater-Bi) for photo-stabilization. The blended products exhibit better tensile strength, photostability, and elongation at break and modulus of elasticity. Active polymer packaging is becoming increasingly important as an emerging technology [112] that can significantly improve the quality and stability of food, eliminating direct addition of chemicals and the need to make significant changes in production processes. If antioxidant polymers are brought into packaging systems, major improvements in maintaining the stability of oxidation-sensitive food products can be made. Antioxidant polymers have been proven to be scavengers that function by reducing the presence of reactive oxygen species, which act as initiators of oxidation processes. In this review, we have seen that antioxidant polymers can be specifically designed and optimized for each specific product or application and in brief, they can be implemented by the food industry as new emerging sustainable polymeric materials.

**Author Contributions:** C.M. writing—original draft preparation, I.S.B. review and editing, T.B. review and editing. All authors have read and agreed to the published version of the manuscript.

**Funding:** This research received no external funding.

**Institutional Review Board Statement:** Not applicable.

**Informed Consent Statement:** Not applicable.

**Data Availability Statement:** The data presented in this study are available on request from the corresponding author.

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