# Application of Natural Antioxidants from Fruits Waste for Improving Egg Quality Characteristics
## 4 Fruit Waste Bioactive Compounds and Antioxidant Potential  
Food waste is a significant global issue, and the production of waste from various fruits is vast, impacting both food security and environmental sustainability. The reports of the Food Agricultural Organization (FAO) [40] and European Commission on Agriculture [41] on the amounts of fruits' waste produced in different countries after their processing are massive. Fruit waste is an abundant and underutilized resource rich in bioactive compounds (Table 1) that have potent antioxidant properties, whose applications in poultry nutrition might benefit multiple parties. Figure 2 graphically represents the most abundant phytochemicals present in fruits' waste. Figure 2: Graphical representation of the phytochemicals reported in fruits’ waste. Among different worldwide cultivated types of fruits, citrus fruits are widely consumed and processed globally, resulting in a large amount of waste, particularly in the form of peels and pulp. The top producers of these fruits are Brazil and United States. According to the FAO [42], in 2020, the global production of citrus fruits exceeded 150 million tons, with around 20-30% being wasted during processing. The above-mentioned countries contribute notably to producing such food waste. Citrus waste contains 7% protein, 14% fiber, 2.5% fat, 24.4% total sugars, and 2.5% moisture, as reported by [PERSON] et al. [43]. Citrus peels are exceptionally rich in polyphenols (8.04 to 12.16 mg/g GAE), lutein and zeaxanthin (36.46 to 81.52 mg/kg), antioxidant capacity, and vitamin C [44; 45] compounds that exhibit strong antioxidant activities. Grape pomace, the residue left after wine production, consists of grape skins, seeds, and stems. Global grape production reaches over 77 million tons annually, with pomace waste making up around 20-25% of the total weight of processed grapes. According to the FAO, Europe, particularly Italy, Spain, and France, produces significant grape waste, as these are the largest wine producers [42]. Grape pomace is an excellent source of polyphenols, including flavonoids, resveratrol, and tannins, which are well known for their antioxidant properties [28; 46]. The recent review study by [PERSON] et al. [46] showed that grape waste also contains a significant content of proanthocyanidins and minerals as well as high amounts of ABTS and DPPH, which have been shown to possess high antioxidant potential. A by-product of juice and cider production is the apple waste accounting for up to 20-30% of the fruit weight. With over 87 million tons of apples produced worldwide each year, China, the United States, and Poland are among the top apple-producing nations contributing to this waste [47]. The nutritional composition consists of carbohydrates (33.77-45.1%), total phenolic content (1.1-289.1 mg/g GAE), moisture (4.4-10.5%), protein (2.91-4.7%), and ash (1.5-2.95%) [48]. Additionally, apple waste is a rich source of bioactive compounds with antioxidant potential, such as dietary fiber, pectin, and vitamins [49]. Rosenip and sea buckthorn waste are primarily used for oil extraction and food supplements, with considerable waste generated from seeds, skin, and pulp. The European Commission (Eurostat) on food waste [50] reported that the waste from these fruits is particularly significant in Eastern Europe and Scandinavia. Rosehips, the fruit of the wild rose plant, are known for their high vitamin C content and potent antioxidant properties. The nutritional composition of rosehip waste contains a significant amount of protein (10.53%), fat (4.84%), fiber (49.35%), total polyphenols, (60.23 mg/g), antioxidant capacity (23.87 mM Trolox), and flavonoids (12.18 mg eq. rutin/g) [20]. Sea buckthorn, a fruit known for its nutrient density and high antioxidant content, produces substantial waste after juice extraction, mainly in the form of skins and seeds [51].