What is the purpose of grading agricultural products?

In the field of agriculture, marketing is sort of a complex system. Marketing is supplying people with goods and services-what people want, in the form they want it, and when they want it. In agriculture, marketing involves moving a wide range of products-food crops, animal products, fiber crops, flowers, wood, and so on.
Marketing links the producer with the consumer. All of the processes and infrastructure involved-harvesting equipment, storage and transportation facilities-all of these processes and infrastructure come under the broad heading of "agricultural marketing technology." The focus of agricultural marketing technology is on meeting consumer demand.
A lot has to be done before farm products are ready for the consumer. The typical North American consumer can’t deal with live chickens or cattle, unshelled wheat, or raw logs. Typical North American consumers want their food ready to cook, their clothes ready to wear, their wood products in sizes ready to use, and so on.
Consumers also want certain products at certain times of the year. They expect to have roses at Valentine’s Day and poinsettias at Christmas. So, producers and marketing specialists have to make these special products available when consumers want them.
Getting products to consumers involves several processe- we call them marketing functions. These functions convert the product from its original form into the form that consumers want, and then transport it to the consumers. Functions such as harvesting, assembling, grading, transporting-these are just some of the important functions of agricultural marketing.
The first function, harvesting-this begins on the farm or ranch. Harvesting methods vary for different types of products. Some products are harvested by machine, while others have to be harvested by hand. Harvesting includes a wide variety of activities  for example, picking apples, picking cotton, digging potatoes, cutting wheat, cutting roses, cutting timber, shearing sheep, milking cows, and so on.
A very important function that comes after harvesting is assembling. Assembling is the delivery of a product to a central location, like a packing shed, grain elevator, cotton gin, or processing plant. Assembling is gathering large quantities together to make marketing more efficient. Marketing professionals want to deal with large volumes, and some farms don’t have large enough volumes, so they have to combine their product with the product of other farms.
Another function is grading, which means sorting products for uniformity. Grading can take place during or after assembling. Grading involves dividing up the product on the basis of several factors-for example, size, color, variety, or the presence of defects. When people buy eggs, they kind of want a uniform size, not a mixture of small, medium, and large eggs. Various standards are used in grading products. Sometimes the government sets the standards. Sometimes the standards are set by an association of producers, or even by the processing plant or supermarket.
A very important marketing function is transporting, moving the product from one place to another. Milk is moved from the dairy farm to a processing plant. Freshly picked tomatoes are moved to the packing shed or cannery. Wheat is moved to the grain elevator. Logs are moved to the sawmill. Agricultural products are transported in various kinds of vehicles: wagons, trucks, barges, airplanes, and railroad cars.
In order to market products, certain facilities must be available-what we call marketing infrastructure-the vehicles, roads, railroads, assembling and processing plants, storage facilities, and so on. All of these facilities are necessary infrastructure for marketing agricultural goods.