Chapter 7
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The energy content of a food can be considered as
The amount of energy that would be produced if the body converted it to CO2+H2O by aerobic metabolism
How the energy content of food is measured
The heat released is termed the heat of combustion and can be measured in a bomb calorimeter
What is one calorie
calorie = amount of heat required to increase the temperature of 1 gram of H 2 O by 1 C
What is the conversion betwen calories and joules
1 J = 0.239 cal 1 cal = 4.184 J)
Food calories are usually measured in ___
Kilocalories
Why measuring food by burning in a bomb calorimeter is not reliable and give the example
because it does not take into account digestibility .+ if you take apples, you will need to take seeds, because we usually do not eat them, as well as remove the peel maybe, etc. Combustion of 1 g of cellulose produces the same amount of heat as combustion of 1 g of starch whereas the human body completely hydrolyzes starch to its glucose subunits but cannot digest cellulose.
If the calorimeter is not the reliable source of info about caloric properties of food, so how it is measured
standard values for the heat of combustion of each class of macronutrients have been adopted. Accordingly, a common method is to use analytical chemistry to determine the amounts of each of the macronutrients in a food sample and then multiply each amount by the corresponding standard value.
Carbohydrates: calories and joules
4 kcal 16.7 kj/g
Protein: calories and joules
4 kcal/g 16.7 kj/g
Fat: calories and joules
9 kcal/g 37.7 kj/g
Alcohol: calories and joules
7 kcal/g 29.3 kcal/g
Organic acids :calories and joules
3 kcal/g 12.5 kj/g
Polyols(sugar alcohols):calories and joules
2.4 kcal/g 10 kj/g
Fiber : calories and joules and why it has calories if we day that we cannot digest it
2 kcal/g 8.4 kj/g calories due to organic acids that are going to be metabolized by bacteria
Polyols have calories, but we still them use as sucrose replacer, why?
1) The way how sugar alcohols metabolized in a different way in our body , so they wont be converted to fat 2) More sweet than sucrose
Why fat have so many calories
because it has a much higher number of carbon atoms per gram , and accordingly combustion to CO 2 involves reaction with a larger number of O 2 molecules In addition to their higher energy content, fats are a compact way to store energy because they are nonpolar and therefore not hydrated ;
The longer the fatty acid, ____ the caloric intake
higher
Calorie reduced foods are usually formulated by ___
( using alternative sweeteners to reduce calories derived from sugars or (ii) using carbohydrate or protein based fat replacers to mimic certain functional properties of fat
What are nutritive sweeteners
Sugar alcohols polyols ), e.g., xylitol, sorbitol, maltitol, mannitol, etc.: these are “ nutritive sweeteners ” because they contribute calories (1.5 3 kcal/g).
Similar properties of sugar and sugar alcohols
• Most the functional properties with fewer calories, like sugar alcohols, they bind water by hydrogen bonding, which contributes to the moistness of baked products.
What are non-nutritive sweeteners
are substances that do not contribute to the calorie content of the food. These very sweet substances are used to replace sugars as a sweetening agent but cannot provide other functional properties of sugars.
What sweetener have bitter aftertaste and 200X more sweet than sucrose
Acesulfame-K
Structure of aspartame
is the methyl ester of a dipeptide phenylalanine + aspartic acid
Does aspartame have caloric content
Yes, the same as proteins