Identifying organic food

At first, organic food comprised mainly fresh vegetables. Early consumers interested in organic food would look for chemical-free, fresh or minimally processed food. They mostly had to buy directly from growers: "Know your farmer, know your food" was the motto. Personal definitions of what constituted "organic" were developed through firsthand experience: by talking to farmers, seeing farm conditions, and farming activities. Small farms grew vegetables (and raised livestock) using organic farming practices, with or without certification, and the individual consumer monitored.
Consumer demand for organic foods continues to increase, and high volume sales through mass outlets, like supermarkets, is rapidly replacing the direct farmer connection. For supermarket consumers, food production is not easily observable, and product labelling, like "certified organic", is relied on. Government regulations and third-party inspectors are looked to for assurance.
A "certified organic" label is usually the only way for consumers to know that a processed product is "organic".

[edit] Legal definition

The National Organic Program (run by the USDA) is in charge of the legal definition of organic in the United States and does organic certification. It administers the Organic Seal to products and producers that meet strict requirements.
Main article: Organic certification
To be certified organic, products must be grown and manufactured in a manner that adheres to standards set by the country they are sold in:
Australia: NASAA Organic Standard.
Britain: Organic Farmers and Growers Organic Standards and the Soil Association
Canada: Canada Gazette, Government of Canada.
Japan: JAS Standards.
United States: National Organic Program (NOP) Standards.
In the United States, the Organic Food Production Act of 1990 (7 U.S.C.A. § 6501-22) required that the USDA develop national standards for organic products.[9] The regulations (7 C.F.R. Part 205) are enforced by the USDA through the National Organic Program under this act. These laws essentially require that any product that claims to be organic must have been manufactured and handled according to specific NOP requirements. A USDA Organic seal identifies products with at least 95% organic ingredients.
Source : http://en.wikipedia.org/wiki/Organic_food .