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Saturday, October 22, 2011

Importance of fruit colour with reference to apple fruit and health

Importance of fruit colour                    

Colour in nature

The colour in nature, its manifestations in the organic world and the complex colour reactions between plants and animals is an interesting phenomenon. It traces the origin of the colour sense in insects to their visits to primeval flowers in order to feed upon the pollen and in birds to their seeking for fruits, whose seeds they dispersed and whose colours were developed to attract them. It shows that the very existence of most of the brilliant colours of the organic world is due to the influence of the colour sense in animals. Animals develop a taste for colour which arouses by the influence of flowers, fruits, or brilliant insects, their habitual food.

Hornbills preferred red and purple fruits over other colours and they preferred large, heavy fruits over smaller fruits. Colour likely provides the cue to ripeness. Silvereyes also preferred red artificial fruits when they were offered with white and yellow fruits against a green background. Red on green is one of the strongest hue contrasts to human eyes. It has often been suggested that red fruits are particularly conspicuous against a background of green leaves and that this may make them especially effective in attracting frugivores.

 Twenty-three avian species were observed interacting with Acacia ligulata diaspores as, seed dispersers, aril thieves, or seed predators. All three avian guilds had feeding biases among morphs. Seed disperser visited yellow and orange morphs. Aril thieves visited orange morphs. Seed predators visited yellow and orange morphs more.

 Consumer preferences

Consumers buy on impulse; that is, when one goes to the market to buy fresh produce, he/she will generally buy that which "catches their eye" best. Producers of fresh fruits and vegetables are keenly aware of this fact and know that the best appearing produce has a competitive edge in the market place. Perhaps, nowhere is this better observed as with apples where the consumer has developed the long-held stereotype that the perfect apple is big and red. Good colour is also important when grading the fruit (i.e., which apples will make U.S. Extra Fancy). For these reasons, apples which have the best colour command the better prices. Even varieties which do not colour very well (i.e., Gala and Fuji) are being bred to produce apples with deeper and deeper red.

The importance of colour in apples can not be overstated. Even in green varieties like Granny Smith, a deep green and sour taste is usually preferred by majority of green apple buyers. This is evident even though Granny Smith will become much sweeter and some what yellowish-green when fully ripe. Fuji is another example of a variety that sells very well as a yellow-orange fruit as long as it is the only one on the market. In general the attractiveness of fruits and vegetables to consumers is determined both by visible (e.g. colour) and invisible (e.g. healthiness) quality attributes. Among apple fruit characters, the red colouration of the fruit skin derived mainly from a class of flavonoids called anthocyanins, is of great importance. This fruit quality characteristic largely determines the consumer appeal and impacts significantly on the market value of the produce.

Colour and health

The human body is constantly under attack from the oxidants; both produced inside the body and from the environmental pollution, especially the air. There are several sources of reactive oxygen in the human body. Production of superoxide in mitochondria is a by-product of the function of the respiratory chain. The first known example of regulated generation of reactive oxygen species (ROS) in mammalian cells was through the respiratory burst of phagocytic cells by nicotinamide adenine dinucleotide phosphate (NADPH) oxidase. Air pollution - toxins, particulate matter and ozone; is the invader that can break down the body's defenses. Although, humans, and all animals, have complex antioxidant defense systems, but they are not perfect and oxidative damage will occur. A healthy, well-balanced diet, consisting of fruits and vegetables can help the body in fighting the oxidants by serving as antioxidants.

A major class of phytochemicals found commonly in fruits and vegetables are the flavonoids. Apples are a very significant source of flavonoids in people's diet. In the United States, twenty-two percent of the phenolics consumed from fruits are from apples making them the largest source of phenolics. In Finland, apples and onions are main sources of dietary flavonoids, while in the Netherlands apples rank third behind tea and onions as top sources of flavonoids.

Different phytochemicals have been found to possess a range of activities, which may help in protecting against chronic disease. For example, phytochemicals may inhibit cancer cell proliferation, regulate inflammatory and immune response, and protect against lipid oxidation. A major role of the phytochemicals is protection against oxidation. We live in a highly oxidative environment, and many processes involved in metabolism may result in the production of more oxidants.

In the United States among the commonly consumed fruits, apples had the second highest level of antioxidant activity. Apples also ranked the second for total concentration of phenolic compounds, and perhaps more importantly, apples had the highest portion of free phenolics when compared to other fruits. This means that these compounds are not bound to other compounds in the fruits, and the phenolics may be more available for eventual absorption into the bloodstream.


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