Natural Antioxidants in Food Preservation: Sources, Mechanisms, and Applications in Lipid-Rich Foods

Natural antioxidants have become indispensable in the food industry for mitigating oxidative deterioration, extending shelf life, and enhancing nutritional profiles of lipid-rich foods such as oils, meats, and dairy products. Derived primarily from plant sources like herbs, spices, fruits, and vegetables, these compounds include polyphenols, flavonoids, carotenoids, and tocopherols, which scavenge free radicals through hydrogen atom transfer (HAT), single electron transfer (SET), or sequential proton loss electron transfer (SPLET) mechanisms. In lipid-rich matrices, oxidative stress initiates via autoxidation, where polyunsaturated fatty acids (PUFAs) form hydroperoxides, leading to rancidity and off-flavors; antioxidants interrupt this chain by donating electrons to peroxyl radicals, stabilizing them as non-reactive species. Extraction techniques for natural antioxidants range from conventional solvent methods using ethanol or acetone to advanced green technologies like supercritical fluid extraction (SFE) with CO۲, which yields high-purity extracts with minimal solvent residues, achieving recoveries up to ۹۵% for phenolic compounds from rosemary or oregano. Characterization involves high-performance liquid chromatography (HPLC) coupled with mass spectrometry (MS) for structural elucidation, alongside assays like DPPH, ABTS, or ORAC to quantify radical scavenging capacity, often expressed as Trolox equivalents (TE). In applications, natural antioxidants are incorporated into edible oils to prevent peroxide value (PV) escalation, with tocopherol-rich extracts from wheat germ reducing PV by ۵۰% in sunflower oil stored at ۶۰°C. In meat products, phenolic-rich grape seed extracts inhibit thiobarbituric acid reactive substances (TBARS) formation, extending color stability in patties by ۷-۱۰ days under refrigeration. Dairy formulations benefit from carotenoid infusions from annatto, countering lipid oxidation in cheeses exposed to light, maintaining sensory scores above ۷/۱۰ over ۳ months. Synergistic effects amplify efficacy; combining ascorbic acid with tocopherols regenerates the latter, enhancing overall antioxidant networks in emulsions. Nanoencapsulation using cyclodextrins or liposomes improves bioavailability and stability, protecting sensitive compounds like curcumin from thermal degradation during baking or frying, with release kinetics following Fickian diffusion in gastrointestinal models. Regulatory frameworks, including FDA GRAS listings for botanicals like green tea catechins, mandate safety assessments via LD۵۰ and NOAEL in rodent studies, confirming no genotoxicity at doses up to ۵۰۰ mg/kg. Consumer trends toward clean-label products drive market growth, projected at $۵.۲ billion by ۲۰۲۸, emphasizing sustainable sourcing from agro-wastes like pomegranate peels, which yield ellagic acid with IC۵۰ values below ۱۰ μM against superoxide radicals. Challenges include variability in antioxidant potency due to geographical origins and processing, addressed through standardized cultivars and optimized extraction parameters. Future innovations involve biotechnological enhancements, such as microbial fermentation to boost flavonoid glycosides in soy extracts, and omics approaches for metabolomic profiling to tailor antioxidants for specific food matrices. In the Iranian context, indigenous sources like saffron crocin or pistachio hulls offer potent alternatives, with crocin demonstrating superior singlet oxygen quenching compared to ẞ-carotene. This review synthesizes mechanistic insights, source diversity, and practical integrations, underscoring natural antioxidants' role in sustainable food preservation and health promotion. Overall, the shift from synthetic preservatives like BHT to natural counterparts not only aligns with health-conscious demands but also mitigates environmental impacts, fostering a resilient food supply chain resilient to oxidative threats.