14.1) Ground beef has a dry matter content of 30%. The dry matter is composed of

Question

14.1) Ground beef has a dry matter content of 30%. The dry matter is composed of 66% protein, 1% carbohydrates and 27% lipids. How many kCal are there in a 0.25 lb. hamburger (pre-cooked weight)? Please recall the heat of combustion for carbohydrates is 4.2 kCal/g; lipids, 9.4 kCal/g; and proteins, 5.65 kCal/g.

14.2) Wheat bread is 69% dry matter. The dry matter portion includes 16% protein, 3% lipids and 70% carbohydrates. What temperature change (oC) would you expect to see in the water portion (5 L) of a bomb calorimeter for a 10 g dry bread sample?

14.3) A 150 lb. man will burn 430 kCal/h while running at a rate of 4.0 mi/h. A McDonald’s ¼ lb. hamburger with cheese has a caloric content of 510 kCal. How far would this person need to run to burn off the caloric content of the hamburger?

Explanation / Answer

a.

1 pound = 453.6 g.

0.25 lb = 113.4

30% 0f 113.4 gm = 34.02 g dry matter is present in the ground beef.

66% of 34.02 = 22.45 g of protein is present. The energy yielded is 22.45 X 5.65 = 126.84 kcal

carbohydrates = 15 0f 34.02 = 0.3402. Energy is 0.3402 X 4.2 = 1.43 kcal

Lipids = 27% = 9.2 g. Energy content = 9.2 X 9.4 = 86.48

The total energy content of dry matter of ground beef = 214.75 kcal.

b.

Protein present in dry bread = 16% = 1.6 gm. Energy = 1.6 X 5.65 = 9.04 kcal

Lipid = 3% = 0.3 gm. Energy = 2.82 kcal

Carbohydrates = 70% = 7 gm. Energy = 29.40 k cal

Total energy = 41.26kcal = 41260 cal

In bomb calorimeter, 1 cal will raise the temperature of 1 gm of water to 1o C.

41260 cal will increase the temperature of 5000 g (5 l) of water by 29o C

c.

The man needs to run 4.74 miles to burn off the caloric content.

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