Ch 3: Chemistry of Food Composition

Six key atoms of food

CHNOPS (carbon, hydrogen, nitrogen, oxygen, phosphorus, sulfur)

6 nutrient groups in food and people

carbs, proteins, lipids, water, minerals, vitamins

measuring heat energy

1 kcal equals the energy needed to raise 1kg of water by 1°C at normal pressure

specific heat of water

water requires more energy to heat compared to other substances (1 calorie heating 1 gram of water by 1°C

water freezes at

32 degrees F

heat of solidification

80kcal/gm

Adding solutes like sugar and salt

lowers freezing point of water (salt has twice the effect compared to sugar)

Latent heat

breaking/remaking of bonds to change

Boiling point

212 degrees F

heat of vaporization

heat required to convert a liquid to a gas (water 540 kcal/gm)

Heat of condensation

heat required to convert a gas to a liquid

For every 500 feet elevation increase (lower atmospheric pressure)=

1 degree F decrease of boiling point

unsaturated solution

a true solution that contains less solute than the solvent can dissolve at a given temperature

Saturated solution

a true solution that contains as much solute as can be dissolved at that temperature

supersaturated solution

a heated saturated solution cooled under carefully controlled conditions can keep more solute in solution than can be theoretically dissolved by the solvent at this cooler temperature

Colloidal dispersion

sol, gel, emulsion, foam

Emulsions

classified based on the type of liquid constituting each of the phases (oil-in-water or water-in-oil)

Ex: oil in water - oil is in dispersed phase, water is in continuous phase

coarse dispersion

suspension (corn starch in water, oatmeal flakes in milk)

Water activity—>bacteria

0.85-1.0

Water activity—>yeasts

0.87-0.91; 0.60-0.65

Water activity—>molds

0.80-0.87; 0.60-0.75

free water

water in food that can be easily obatined by change in composition (squeezing, pressing, cutting), oranges, lemons, peaches

bound water

water unable to function in typical ways due to being tightly held to other molecules, no flow properties, cannot serve as a solvent

3 common monosaccharides (hexoses)

glucose (predominant in blood; found in fruits/honey)

Fructose (sweetest, fruits/honey)

Galactose (part of lactose in milk)

3 disaccharides

sucrose (table sugar, glucose +fructose)

lactose (milk sugar, glucose + galactose)

Maltose (malt sugar, 2 glucose)

3 oligosaccharides

raffinose and stachyose (dried beans, poorly digested, produce gas)

Fructo-oligosaccharides (act as prebiotics, asparagus, bananas, chicory, garlic, onions)

2 polysaccharides

starch (amylose/amylopectin, stored energy for plants, digestible by humans)

glycogen (stored energy for animals, digestible, turned into lactic acid during slaughter)

fiber

polysaccharide, undigestible, only found in plant-originated food