Vegetable discoloration

Arsenicals Acid Unpleasant Meat vegetables discolored... 

Freshly cut surfaces of fruits and vegetables discolor when exposed to oxygen in the air. Cut three slices of a fruit or vegetable such as apple, potato, avocado, or banana. Leave one piece on the kitchen counter (uncovered). Wrap one piece in plastic wrap and leave it on the kitchen counter. Dip one piece in lemon juice and leave it uncovered. 

Sulphur dioxide Combustion of coal, oil and other sulphur-containing fuels Petroleum refining, metal smelting, paper-making Vegetation damage Sensory and respiratory irritation Corrosion Discoloration of buildings... 

Leafy vegetables and some fruits in particular are rich sources of chlorophylls. However, they are ranked among the most perishable post-harvest products and must be consumed within a few days after harvest or subjected to preservation methods to extend their freshness. Their typical green color is, if not the most important sensory attribute, an extremely important parameter of quality. Any discoloration can lead to rejection by consumers as the bright green color is intuitively linked with freshness. 

Munition grade agents typically consist of at least one malodorant agent (10-90%) and an odor intensifier (0.5-5%) dissolved in a liquid carrier. Solvents include volatile hydrocarbons, plant/vegetable oils, and water. Solvents typically pose minimal toxic hazards themselves. Compositions are typically colorless to yellow liquids. As the agent ages and decomposes it may discolor and become brown. 

Bad appearance. Turbidity is caused by suspended matter, which may contain disease-causing microorganisms. Discoloration that leaves stains can be caused by dissolved or colloidal iron, tannin, or humic acid from decaying vegetation, and excessive salt content. 

Sapium sebiferum (L.) Roxb. S. discolor Mueller-Arg. Wu Jiu Shan Jiu (Chinese tallow tree, Chinese vegetable tallow) (Leaf, root bark) Xanthoxylin, corilagin, sebiferic acid, lauric acid, margaric acid, palmitic acid.33-50 Antihypertensive activity, for constipation, poisoning, skin diseases. 

Many countries do not allow use of S02 or sulfite salts on meats, fish, piocessed meat and fish products, 01 flesh fruits and vegetables. Where permitted, sulfite is helpful in eliminating black spot formation in shrimp. End-use application of sulfite related compounds as. for example, to prevent discoloration of leafy vegetables on salad bars, is now subject to regulation in the United States. 

Food acidulants find their application, for the greater part, in beverages and in fruit and vegetable processing. Apart from pH lowering, acidulants provide buffer capacity, impair sourness and tartness, enhance the effect of preservatives, and for some acidulants such as citric acid, prevent discoloration caused by trace metals (Seifert, 1992). 

The relative resistance of wool to acids is of importance in freeing it from burrs picked up by the sheep. If they are not removed they may cause mechanical trouble in spinning and local discoloration in the finished cloth. There are some vegetable impurities which do not absorb wool dyes and may cause light-coloured spots after dyeing. The burrs, which are composed of cellulose, are destroyed by treatment with acid and heat under conditions harmless to the wool, but which will convert the cellulose to hydrocellulose which can he pulverized and shaken out. 

Anthocvanlns. Anthocyanlns are flavonoid, phenolic-based, water-soluble compounds located in the cell vacuole of the epidermal cells of many fruits and vegetables (371. They confer the characteristic red and blue colors of many flowers and fruits and as such are Important components of visual quality. The anthocyanins are pH indicators and are red at low pH, colorless at Intermediate pH and blue at higher pH. The blue colors at high pH are the result of copigmentation and metal chelation rather than a direct effect of pH. This can result in discoloration of fruits packed in metal containers or handled with metal implements (381. 

Oxidation of Phenolic Compounds. Phenolic compounds are widespread throughout the plant kingdom and are prevalent in fruits where they are important contributors to color and flavor (46). Phenolic compounds, particularly flavonoids and derivatives of chlorogenic acid, play a crucial role in the development of a number of postharvest disorders through their oxidation to brown compounds that discolor many fruits and vegetables and substantially reduce their quality. A number of enzymes catalyze the biosynthesis or oxidation of phenolic compounds, among them phenylalanine ammonia lyase (PAL), tyrosine ammonia lyase (TAL), cinnamic acid-4-hydroxylase (CA4H), polyphenol oxidase (PPO), and catechol oxidase (CAO). The chemistry... 

Discoloration of lightly processed fruits and vegetables is often the factor that determines their shelf-life. Enzyme catalyzed reactions which convert phenolic compounds to brown melanins are the main causes of discoloration of lightly processed fruits and vegetables. When products are peeled, cut, or otherwise injured, cellular compartmentation is lost, enzymes and substrates come in contact with each other, and discoloration occurs (10). The products of these reactions may also produce off-flavors, but the appearance is usually unacceptable at... 

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