Đậu phộng. Đậu phộng được trồng trên toàn cầu với Hoa Kỳ, Ấn Độ và Trung Quốc đang là các quốc gia sản xuất đậu phộng hàng đầu (Maiti và Wesche-Ebeling, 2002). Đậu phộng được trồng chủ yếu như một vụ thu hoạch dầu trong hầu hết thế giới nhưng được sử dụng chủ yếu để sản xuất bơ đậu phộng trong Hoa Kỳ Năm 2011, Hoa Kỳ sản xuất 3,64 tỷ bảng Anh của đậu phộng (lạc, đậu phộng người Mỹ đồng năm 2011). Các tác phẩm tiêu biểu của hạt đậu phộng là 40-50% chất béo, 20-30% đạm, 10-20% cacbohydrat và họ là một nguồn tốt của kali, phốt pho và magiê (Francisco và Resurreccion, 2008). Chúng cũng chứa các vitamin E, niacin, folate, canxi, natri, kẽm, sắt, riboflavin và Thiamin (Francisco và Resurreccion, 2008).Peanut Skins. Currently, the seed, which only represents 40% of the entire peanut plant, is the most economically important part of the peanut plant (Dean et al. 2008). The remaining parts of the peanut plant are typically regarded as waste products and presently have very limited uses. Peanut leaves, stems, and roots are most often plowed back into the soil after digging, with peanut leaves having some use as animal hay (Almazan and Begum 1996). During peanut processing, peanut hulls and skins are removed by shelling and blanching. These two components have been restricted to usage as animal feed or mulch. However, due to the high content of polyphenols in peanut skins (approximately 5-8%), peanut skins cannot be used in very high levels in animal feeds (Dean et al. 2008). The content of polyphenolics polymerize with dietary protein making it unavailable for absorption (Hill 2002; Sobolev and Cole 2003). Nepote et al. (2002) reported peanut skins contain ~150 mg of total polyphenols per gram of defatted dry skin. The main compounds are catechins, procyanidins and the flavonoids; 5, 7-dihydroxychromone, eriodictyol, and luteolin (Bolling et al. 2010). These natural antioxidants which are found in fruits, vegetables, grape seeds, grape skins and green tea and have been studied for their potential health benefits which includes cancer inhibition, reduction of cardiovascular disease risk and anti-inflammatory activities (Bolling et al. 2010; Kim et. al, 2004). Since the same active compounds found in certain fruits and vegetables are also found in peanut skins, it is logical to assume that peanut skins would have similar health promoting properties. Total antioxidant activities of skin extracts have been reported to be chemically higher in antioxidant potential than green tea (Yu et al. 2006; Wang et al. 2007). They have also been reported to be efficient free radical scavengers and metal chelators to prevent the Fenton reaction in muscle foods (Walgren et al. 2000; Wang et al. 2007). Metal-chelating activity is important in stabilizing food materials rich in metal ions such as muscle foods, which are prone to lipid oxidation (Decker and Welch, 1990). Van Ha et al. (2007) reported that the antioxidants that are present in skins can stabilize bound ferrous ions in muscle foods causing inhibition of lipid oxidation. The metal-chelating ability of these antioxidants is related to the presence of catechol or galloyl groups (Khokar and Apenten 2003; Moran et al. 1997). Flavonoids have been widely reported to possess metal chelation properties (Whitehead et al. 1995; Fuhrman et al. 1995; Middeton and Kondasmami 1992). However, since these compounds vary in structure, only some of these compounds have been reported to have this attribute (Perron and Brumaghim 2009). Compounds such as epicatechin, gallic acid and quercetin are well known and highly effective metal chelators (Elhabiri et al. 2007; Erdogan et al. 2005; Kipton et al. 1982). The compounds listed above have also been reported in peanut skins and would suggest that peanut skins would be great candidates for the stabilization of foods containing water and transient metal ions (Van Ha et al. 2007). Despite this, peanut skins have not been exploited for their underlying potential as a source of natural antioxidants (Sanders et al. 2000).
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