Contents 3 Natural Antioxidants

Olive fruit has long been used as a food and as a source of edible oil for frying and salad dressings. The phenolic content in olive fruits is known to contribute to the natural bitterness and the final color of fruits (66), and to provide natural antioxidant activity in olive oil... 

Measuring the resistance to oxidation is one way of establishing oil quality inasmuch as this property determines storage and usage stability. The length of the stability period (viz. the interval between oil production and the oil becoming rancid) depends both on intrinsic features (e.g. the contents in fatty acids and natural antioxidants such as tocopherols and biophenols) and environmental conditions (temperature, light, air exposure, type and material of the container, trace metal content) and the time the oil is exposed to them. 

Several studies have confirmed that the seed oil from the North American variety of cranberry contains significant levels of a-linolenic acid. In a U.S. patent, Heeg et al. (4) reported the a-linolenic acid content of cranberry seed oil to be between 30% and 35% of total fatty acids. In 2003, Parker et al. (5) found 22.3% a-linolenic acid in the cold-pressed cranberry seed oil, and in 2004, Parry et al. (3) determined the oil to contain 32.0% a-linolenic acid from two different lots of the seed oil. The ratios of n-6 to n-3 fatty acids in all were low from 1.2 1 to 2 1. Also, all of the studies documented similar ratios among the rest of the common fatty acids found in cranberry seed oil, including, in order of higher amount present linoleic, oleic, palmitic, stearic, and eicosadienoic (20 2) acids (Table 1). In addition to a-linolenic acid, cranberry seed oil is rich in natural antioxidants (8). These antioxidants may directly react with free radicals and prevent lipid oxidation in human low-density lipoprotein. 

Excessive rain before harvest can increase chlorophyll content of the crude oil. There are two types of chlorophylls found in oUseed Chlorophyll-A and Chloro-phyll-B. Chlorophylls are oU soluble and produce green color in the oU. At normal concentrations, they are easily reduced in the bleaching process. It is very difficult to reduce the chlorophylls from the crude oil if it is obtained from seeds that are not mature or have developed higher chlorophylls because of excessive rain before the harvest. The normal practice is to use an excess amount of bleaching clay to reduce chlorophylls. This reduces the natural antioxidants in the oil, produces higher amounts of free radicals in the oil, and reduces its stability. 

The deodorization of cocoa butter is necessary to reduce free fatty acid content and to give a product that satisfies the present day requirement of a neutral bland flavor. Deodorization is a suitable method for partially eliminating chlorinated insecticides from cocoa butter. The normal deodorization temperatures are in the range 160-180°C. The oxidative stability of various cocoa butters listed in Table 4 shows extremely high values, and these are unaffected during the deodorization process. Stability against oxidation depends on natural antioxidants present in cocoa butters. The tocopherol composition in Table 5 shows a predominance of... 

Synthetic antioxidants effectively improve the stability of fats and oils with a low level of natural antioxidants, such as tocopherols, and with a low level of polyunsaturation. With oils that have a high content of polyunsaturated fatty acids and significant level of tocopherols, such as soybean oil, synthetic antioxidants... 

The quality of a refined oil is usually evaluated by traditional quality parameters such as a low residual FFA content, a high oxidative stability, a light color, and a neutral odor and taste. In addition, high-quality food oils should contain low transfatty acid (TEA) levels, high amounts of natural antioxidants and vitamins, low levels of polymeric and oxidized triacylglycerols, and no contaminants (pesticides, polycyclic aromatic hydrocarbons, dioxins and polychlorinated biphenyls, etc.) (Tables 5 and 6). 

The content of tocopherol, a natural antioxidant in canola, is comparable to those of peanut and palm oil. This is an important factor for oils with high linolenic acid content, which can reduce the shelf-life of the product, while the namral antioxidant, if present, can prevent oxidation during storage and processing. 

Many manufactured superfruit juices have been processed so extensively that the natural antioxidant ACE vitamins are completely absent, even if the product is advertised as an antioxidant superfruit juice. Double—or even triple—pasteurizing is the main reason for vitamin loss. Check the Nutrition Facts panel on such products to see if ACE vitamin contents are at good-to-high percentages of the daily values. 

Mixed tocopherols can be added dispersed in dry raw materials or suspended in water or mixed with ethanol as a carrier (O Brien and Robertson, 1993 Six, 1994). Typical usage levels are 150-450 pg/g. Partly, this large range of different addition levels is due to the large range of tocopherol and tocotrienol contents of the raw materials (Cort et al., 1983) and their susceptibility to oxidation. Often, tocopherols and tocotrienols are added mixed with other compounds such as ascorbic acid or chelating agents that enhance the effect of tocopherols as natural antioxidants (Six, 1994). 

The effectiveness of the two natural antioxidants rosemary and sage increases with the content of the active phenolic diterpenes [2-3]. New and improved extraction techniques based on supercritical C02-extraction (see chapter 2.1.2) resulted not only in concentrated and very active, but also in well desodourized and almost neutral tasting antioxidants. 

In this fraction, not only the fatty acid composition is important. Another important feature is the natural presence of a high amount of vitamin E (a-tocopherol), 0.59-2.6 mg/100 g in the seeds (Coulter and Lorenz, 1990 Ryan et al., 2007 USDA, 2005), which acts as a natural defense against lipid oxidation (Ng et al., 2007). This fact could lead to a very stable oil from QS, with vitamin E acting as a natural antioxidant. The (p + y)-tocopherol content in quinoa whole flour has been reported as 3.1-5.5 mg/100 g (Ruales and Nair, 1993 Ryan et al., 2007). The chemical stability of the lipids in quinoa flour was studied by Ng et al. (2007), who... 

The use of natural antioxidants in supplements can also exhibit pro-oxidant activity under certain conditions such as the concentration and nature of the polyphenolic compounds causing oxidative damage to important cellular components (48). Aqueous extracts and erode polyphenolic fractions of both traditional and green rooibos were evaluated for possible pro-oxidant activity using a Fenton reaction model system containing FeCb-EDTA and H2O2 for the generation of hydroxyl radicals. Pro-oxidant activity was shown for pure aspalathin while the dihydrochalcone and flavonoid contents of the enriched... 

M. oleifera seed oil is high in the natural antioxidants - tocopherols (128) with homologues (a- P, y-, and 8-tocopherol) (42). Extraction methods influence the quantities of tocopherols extracted (2). a-Tocopherol is the primary vitamer with biological activity, while the other vitamers have been shown to have decreased activity, y-tocopherol has 10% of the activity of a-tocopherol, and 5-tocopherol has 1% of the activity of a-tocopherol (38,115). a-tocopherol content of M. oleifera leaves averages 90.0 mg/kg. However, a-, y- and 5-tocopherols are detected up to levels of 105.0, 39.5 and 77.6 mg/kg of oil, respectively as shown in Table VII (2,82). 

Oryzanols are natural antioxidants having phenolic hydroxyl groups similar to tocopherols. The y-oryzanol content in the by-products is reported in Table 1. The highest amount of y-oryzanol (18 mg per g of rice bran oil, sample XI) was... 

LUGASi A, hovari J, GASZTONYi M N and DWORSCHAK E (1999), Flavonoid content and antioxidant properties of broccoli , in Kumpulainen J T and Salonen J T, Natural antioxidants and anticarcinogens in nutrition, health and disease, Cambridge Royal Society of Chemistry, 291-298. 

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