Vegetable ascorbic acid

Epidemiological Study of Colon Cancer Various Nutrients and Colon Cancer Aspirin and Colon Cancer Isothiocyanates Possible Anticancer Agents from Vegetables Ascorbic Acid Possible Anticancer Agent from Fruits and Vegetables Peroxynitrite A Form of Toxic Oxygen Chronic Exposure Theory Summary References Bibliography... 

Ascorbic Acid A six carbon compound related to glucose. It is found naturally in dtrus fruits and many vegetables. Ascorbic acid is an essential nutrient in human diets, and necessary to maintain connective tissue and bone. Its biologically active form, vitamin C, functions as a redudng agent and coenzyme in several metabolic pathways. Vitamin C is... 

Vegetable Ascorbic acid Thitunine Riboflavin Nicotinicacid Folacid a-Tocopherol P-Carotene ... 

Other Food Uses. Jellies, jams, and preserves use malic acid to balance flavor and adjust pH for pectin set. Canned fmits and vegetables employ malic acid in combination with ascorbic acid to produce a synergistic effect that aids in the reduction of browning. Wine and cider producers use malic acid in malolactic fermentation to provide bouquet and for pH adjustment. 

Inhibition of nitrosation is generally accompHshed by substances that compete effectively for the active nitrosating iatermediate. /V-Nitrosamine formation in vitro can be inhibited by ascorbic acid [50-81-7] (vitamin C) and a-tocopherol [59-02-9] (vitamin E) (61,62), as well as by several other classes of compounds including pyrroles, phenols, and a2iridines (63—65). Inhibition of iatragastric nitrosation ia humans by ascorbic acid and by foods such as fmit and vegetable juices or food extracts has been reported ia several instances (26,66,67). 

Salads. A combination of citric acid and ascorbic acid is used as an alternative to sulfites in prevention of enzymatic browning in fresh prepared vegetables (56). 

Thus, it is uncertain to what extent the apparent protective effects of fruit and vegetable consumption on risk of stomach cancer can be attributable to their phytoestrogen content. This appears not to have been studied directly, and other constituents such as ascorbic acid (vitamin C), a-tocopherol (vitamin E) and /1-carotene may be potentially protective. 

Vitamin C occurs as L-ascorbic acid and dihydroascorbic acid in fruits, vegetables and potatoes, as well as in processed foods to which it has been added as an antioxidant. The only wholly undisputed function of vitamin C is the prevention of scurvy. Although this is the physiological rationale for the currently recommended intake levels, there is growing evidence that vitamin C may provide additional protective effects against other diseases including cancer, and the recommended dietary allowance (RDA) may be increased in the near future. Scurvy develops in adults whose habitual intake of vitamin C falls below 1 mg/d, and under experimental conditions 10 mg/d is sufficient to prevent or alleviate symptoms (Bartley et al., 1953). The RDA is 60 mg per day in the USA, but plasma levels of ascorbate do not achieve saturation until daily intakes reach around 100 mg (Bates et al., 1979). Most of the ascorbate in human diets is derived from natural sources, and consumers who eat five portions, or about 400-500 g, of fruits and vegetables per day could obtain as much as 200 mg of ascorbate. 

Phytochemicals present in fruits and vegetables are very diverse, such as ascorbic acid, carotenoids, and phenolic compounds (Liu 2004 Percival and others 2006 Syngletary and others 2005 Yahia and others 2001a, 2001b). Plant polyphenols are ubiquitous in the diet, with rich sources being tea, wine, fruits, and vegetables they demonstrate considerable antioxidative activity in vitro, which can have important implications for health (Duthie and others 2000). 

Yahia EM, Soto G, Puga V and Steta M. 2001a. Hot air treatment effect on the postharvest quality and ascorbic acid content in tomato fruit. In Artes F, Gil MI and Conesa MA, editors. Improving Postharvest Technologies of Fruits, Vegetables and Ornamentals, Volume 2. Paris International Institute of Refrigeration, pp. 550-556. 

As has been explained in previous chapters, the antioxidant capacity of fruits and vegetables is a function of the amounts and types of phytochemicals that are present in the fresh tissues. However, the individual contribution to the total antioxidant capacity varies widely. Various studies have demonstrated that phenols and flavonoids contribute to a higher extent than ascorbic acid, carotenoids, and others to the antioxidant capacity of fmits and vegetables (Robles-Sanchez and others 2007). It has been observed that a given content of vitamin E in fruits contributes significantly more to the antioxidant capacity than the same content of ascorbic acid. 

Ascorbic acid retention in some fresh-cut produce is affected by the nature of the slicing method used (Lee and Kader 2000). Higher levels of ascorbic acid were retained in samples that had been prepared by manually tearing the lettuce into strips. Lettuce shredded using a sharp knife initially retained 18% less ascorbic acid than the torn samples. The retention of ascorbic acid in the products sliced by machine was 25-63% lower than that in lettuce shredded by manual tearing. Using a blunt machine blade resulted in 10% lower ascorbic acid levels than when a sharp blade was used (Barry-Ryan and O Beirne 1999). Losses in ascorbic acid occur when vegetables are severely cut or shredded (Lee and Kader 2000). 

Ascorbic acid is probably the most labile bioactive compound in fruit juices and fruit and vegetable pieces, as we described in the first part of this chapter. Retention of this phytochemical after the nonthermal treatments ranged from 47% to 100%, depending on the intensity of the applied treatment and the product. For example, the greatest losses of vitamin C were found in fresh-cut red lettuce and melon treated with IR and HHP (Fan and others 2008 Wolbang and others 2008), respectively. However, the use of gamma radiation in various vegetables retained 100% of their total ascorbic acid content (Fan and others 2008). 

Antioxidant capacity of fruits and vegetables depends on the total concentrations of phytochemicals, mainly ascorbic acid, phenolic compounds (including flavonoids), and carotenoids. However, as previously stated, the individual contribution of each compound to the total antioxidant capacity varies widely and is difficult to quantify in a whole food product. 

It may be concluded that PEF, HHP, and IR are adequate techniques for the retention of bioactive compounds in fruit and vegetable products and may even enhance bioactivity of juices, purees, and fresh-cut produce. A greater degradation of ascorbic acid in comparison with phenolics and carotenoids is usually observed. 

Howard LA, Wong AD, Perry AK and Klein. 1999. fi-Carotene and ascorbic acid retention in fresh and processed vegetables. J Food Sci 64(5) 929-936. 

For the group of fats and oils the antioxidants listed in Table 12.10 are used. For fish and fish products (including prawns and shrimps), fmit and vegetable products (including raw peeled potatoes) and meat and meat products (corned, cured, pickled or salted and cooked) only ascorbic acid, eiythorbic acid and their sodium salts may be used. 

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