Final answer:
Calorie values are derived from the Atwater system, with proteins and carbohydrates providing 4 calories per gram and fats providing 9 calories per gram. These values are important for counting Calories and understanding the energy content of foods.
Step-by-step explanation:
Calorie Values for Energy-Containing SubstancesThe calorie values for different energy-containing substances like proteins, carbohydrates, and fats are essential for understanding nutrition and energy intake. These values come from the Atwater system which uses averages obtained from bomb calorimetry tests of whole foods. Typically, proteins and carbohydrates have 4 calories per gram whereas fats contain 9 calories per gram, making them more energy-denseFor example, the total energy for a 228-g portion of food can be calculated with the following breakdown: (5 g protein x 4 Calories/g) + (31 g carb × 4 Calories/g) + (12 g fat × 9 Calories/g) = 252 Calories. This demonstrates how to use food labels to count Calories and determine energy content and energy efficiency ratio of food items.It's important to realize that Calories in the context of food are actually kilocalories; hence, 1 Calorie with a capital C is equivalent to 1 kilocalorie (kcal), or 1000 calories.
The calorie values for different energy-containing substances come from the caloric content of foods, which can be determined using bomb calorimetry. Bomb calorimetry involves burning the food and measuring the energy it contains. The caloric content of foods is determined by measuring the temperature change during the burning process and converting it into energy per gram of food.The total energy content of a food can be calculated by multiplying the quantities of protein, carbohydrate, and fat by their respective average calories per gram, and then summing the products. For example, a 228-g portion of food can have a total energy of 252 Calories, calculated as (5 g protein x 4 Calories/g) + (31 g carb x 4 Calories/g) + (12 g fat x 9 Calories/g). Food labels often provide the calorie values, which are derived using the Atwater system that uses the average caloric content of the different chemical constituents of food.