Define Steps in the Development of Exchange List?
As mentioned above, when we group together similar food items so that each supplies a constant amount of a particular nutrient, we call the group a food exchange. Given herewith are the steps which when followed, will guide you in developing the exchange list. You will realize that developing an exchange list for Indian foods is a difficult task as our dishes defy any attempt at standardization.
1) An important first step in developing an exchange list is the standardization of serving or portion sizes. The portion sizes vary considerably in India. ldlis, dosas, chapattis and puris of different sizes in different states and in different households is a common scene. Despite this, some attempts have been made to define portion sizes.
2) The second step is to calculate the energy, carbohydrate, protein and fat content of one serving or portion size of the different dishes. This can be done by converting the cooked weight of one serving of a dish into raw weight of the T ingredients that have gone into it. Although allowances should be made for cooking losses, this has not been done. Future exchange lists must take care of this. From the raw weights of the ingredients in one serving and using the Indian Food Composition tables, the energy, carbohydrate, protein and fat content of one serving can be calculated.
3) The third step is to create an exchange list of different dishes in terms of standard portion sizes that would provide approximately the same energy or carbohydrate or fat as the case may be. Since foods contain widely varying amount of the macronutrients, serving or portion sizes are defined for a group of more or less homogeneous foods. For example, all cereals provide approximately the same number of calories, approximately 350 per 100 g raw weight and about the same amount of carbohydrates, about 70 g per 100 g raw m weight. Therefore, cereal exchanges are grouped together. Similarly, there are vegetable, fruits, milk and meat exchanges. Within each of these food groups, the composition of the different items in terms of carbohydrate, protein and fats remain similar.