Harvesting, Processing, and Cooking Influences on Vitamin C in Foods

Abstract

Vitamin C is considered the most labile of the vitamins in our food supply. Reduced ascorbic acid (RAA), which is the predominant form found in foods of plant origin, can be reversibly oxidized to dehydroascorbic acid (DHA). Further irreversible oxidation of RAA or DHA to diketogulonic acid or other products results in loss of biological activity. Oxidation can occur in the presence of metal catalysts, or plant oxidase enzymes, particularly following cell damage, or as a result of heat during food processing. Vitamin C is easily leached from foods during processing and is discarded with washing, soaking, or cooking water. Ascorbic acid losses begin with harvesting and continue through handling, industrial or home preparation, cooking, and storage of plant foods.

Radical-Scavenging Activity of Vegetables and the Effect of Coking on Their Activity.

“…Therefore, the antioxidant compounds of these vegetables were stable during heating, but were leached out into the cooking water during boiling. Erdman and Klein (1982) reported that when a large volume of water was used for boiling, a higher content of ASA was found in the cooking water, which emphasizes the importance of using a small volume of water in vegetable cookery.…”

“…Microwave heating has wellknown advantages over boiling, the conventional heating process, because foods are heated directly and rapidly without contact with hot surfaces (Young & Jolly, 1990). Many experiments have been carried out on the effect of processing and cooking on vitamin C content in vegetables (Erdman & Klein, 1982;Kiribuchi & Kawashima, 1987;Sako et al, 1996;Howard et al, 1999). It is generally believed that these steps result in significant loss of vitamin C. However, the effect of processing and cooking on the radical-scavenging activity of vegetables has not yet been fully approached.…”

Criteria and Recommendations for Vitamin C Intake

“…15,23,24 Estimates of vitamin C amounts in foods depend on season, transport of the food, shelf time prior to purchase, storage, and cooking practices. For example, supermarket broccoli compared with wholesaler broccoli can lose 33% of its vitamin C, and boiling vegetables can cause 50% to 80% loss.…”

“…Cooking vegetables with minimal water or in a microwave oven will decrease vitamin C losses. 23,24 As a supplement, ascorbate is available in tablet and powder forms, with a wide dose range. Ascorbate is part of many multivitamin formulations and is in supplements with selected vita- mins, commonly sold as antioxidant supplements.…”

Effect of slicing and controlled-atmosphere storage on the ascorbate content and quality of strawberries and persimmons

“…Oxidation also occurs on exposure to halides, such as hypochlorite (Bielski, 1982); due to concerns about the microbiological safety of freshcut produce, many products are washed in a solution of sodium hypochlorite. Ascorbate is oxidized by interaction with enzymes, such as ascorbate oxidase, polyphenol oxidase, cytochrome oxidase and peroxidase (Erdman and Klein, 1982). Cutting damages cells adjacent to the cut, resulting in the mixing of enzymes and substrates that would be compartmentalized in undamaged tissue (Watada et al, 1990).…”