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Food, Nutrition and Wellness

 
 

Subject Areas

 
 

What is the Effect of Climate on Citrus Fruit?

 
It has long been established that fruit grown in humid areas has a thinner peel than those grown in desert areas such as California and Arizon In general, fruit produced in hot, desert climates are thicker peeled and less juicy than those grown in the hot, wet climate such as Florid High night temperatures such as are received in Florida, Texas and other tropical regions of the world result in low acid fruit, while fruit produced in such areas as California and Arizona, when night temperatures are low, is highly acid. This is why there is very little grapefruit produced in California and a great deal of grapefruit produced in Florida and Texas. Sweet oranges, on the other hand, are so low in acid in hot tropical areas that they are insipid. Sweet oranges need relatively cool night temperatures to develop the acidity and total soluble solids needed for good quality. The juice quality of sweet oranges in all regions of the United States ultimately becomes very good as the fruit matures. The climate will greatly affect the date of legal maturity.

What influence does temperature have on peel color?

Sweet oranges require low night temperatures (below 55º F.) Before they will color well. Thus, early maturing oranges in Florida must be treated with ethylene gas and sometimes color added (dyed orange). None of this affects fruit quality. Yield color is not related to fruit quality except co-incidentally. One will notice sweet oranges coloring "almost overnight" in Florida once there are sharp drops in temperature below 55º F.

What effect does freezing have on the composition of citrus fruit?

The formation of ice crystals in citrus fruit causes disorganization of the cell structure. Fruit harvested immediately may be little changed in composition but fruit remaining on the tree may show shrinkage and desiccation. Fruit, if actually frozen, definitely dries on the tree. Such fruit can be used for processing but not for fresh market.

What effect does storage temperature have on the retention of ascorbic acid in canned juices?

Studies on canned orange and grapefruit juice have shown a marked difference in the retention of ascorbic acid relating to temperature. Juice stored at 40º F., lost 6 percent or less ascorbic acid in 18 months. There appeared to be an initial loss of about 20 percent after six months of storage. Loss occurred at a slightly slower rate between 12 and 18 months. Flavor retention was also better in cold storage than when kept at 76º F.

Does citrus ripen after it is picked?

Citrus does not ripen off the tree like apples and peas do. Citrus has no starchy reserves that are converted to sugar in storage. Losses in soluble solid, acidity and a slight loss of vitamin C does take place. The fruit respires off the tree and "burns up" or utilizes some of the sugar and acid in the respiration process. Citrus fruit stored at temperatures that are too low, but well above freezing may suffer chilling injury. Brown sunken areas develop on the peel as a result of chilling injury.

What effect does "regreening" of the rind have on the composition of oranges?

There may be a slight difference in quality of regreened fruit but these differences are generally not very meaningful.

Does sunlight effect vitamin content?


Studies show that the highest values of ascorbic acid have been found in oranges in the southern aspect of the tree where they received the most sunlight.

What is in citrus fruit (composition and structure)?

Citrus fruits are a primary source of our daily requirement of vitamin C. In addition, supplementary nutritional value is obtained from amino acids, inorganic salts, carbohydrates and folates. The color of the fruit comes from carotenoid pigments, chlorophyll, and possibly flavonoids. The characteristic aroma is obtained from volatile essential oils, found in the peel. All these chemical constituents are subject to the influence of genetics. Physical, chemical, biological environments to which citrus fruits are subject during growth and after harvest.

Structure

Citrus fruits are covered with a rind or peel to protect the pulp or edible portion of the fruit.

  • The flavedo, or thin outer covering, contains numerous oil sacs or glands filled with an aromatic essential oil.
  • A white spongy portion known as the albedo, lies directly beneath the flavedo. This layer contains about 20 percent of pectinous substances which can be recovered in the form of citrus pectin.
  • The inner pulp, or flesh of the fruit consists of segments, separated by a membrane of thin epidermal tissue and containing numerous spindle-shaped juice sacs, vesicles, and seeds.
  • The Proteins in citrus are relatively insoluble, and are found to be associated with the solid portions of the fruit. Such as the seeds, flavedo, albedo, and pulp.