Lecture 11: Fats & Oils Flashcards
Definition of lipids
- Aka fats & oils
- Organic compounds (CHO) that don’t mix with water
Most common lipid?
Triglycerides (3 fatty acids attached to glycerol)
calorie
1 calories raises 1 gram of water 1 C
kcal
1 kcal raises 1000 grams of water 1 C
-aka Calorie or Big Calorie
Caloric value of carbohydrates
4 kcals/gram
Caloric value of proteins
4 kcals/gram
Caloric value of fats
9 kcals/gram
USDA recommendations for fat intake
- Diet low in fat, saturated fat, cholesterol, trans fat
- Eat less than 35% of total calories from fats & oils (keep it between 20-35%)
Lipases
- Enzymes that break down lipids so that the free fatty acids can be absorbed
- Take part in triglyceride hydrolysis
Vegetable oil
Triglyceride extracted from a plant
From what are edible oils extracted from
Plant seeds
What is the largest quantity of all vegetable oil produced worldwide?
Palm oil
What is the largest quantity of edible vegetable oil produced worldwide?
Soybean oil
Mechanical extraction
Older method of crushing or pressing to produce the more traditional oils (olive, palm)
Solvent extraction
- Used for most of the “newer” industrial oils (soybean, corn)
- Most common solvent is petroleum-derived hexane
Centrifugation
After extraction, this process separates water and oil
Virgin olive oil
Oil that is extracted from olives using purely mechanical means
Difference between fats and oils
- Fats are semi-solids at room temp
- Oils are liquid at room temp
How does the food industry label fats in foods
- Percent by weight
- Like to tell you how much fat isn’t there
- “95% fat free” as opposed to “5% fat”
How does diluting food with water change fat content?
-Percentage of fat by weight will go down, but the percent of calories from fat will not change
Simplesse
- Made from dairy and egg proteins
- Can be formulated as a powder
- May have problems with heating
- 1 cal vs. 9 cal (regular fats)
- Manufactures recommend food label is “dairy protein”
Olestra
- Chemically bonds fatty acids onto sugar molecules
- So large that they’re indigestible
Controversy over Olestra as a fat substitute
-Olestra claimed to be able to reduce people’s caloric intake & help w/ weight loss
PROBLEMS:
-Quantity of intake doesn’t change or increases —> no weight loss
-People’s different biological reactions to Olestra —> doesn’t work for everyone
-Higher quantities interfere w/ absorption of some vitamins derived from fatty acids
Melting point of saturated fatty acids
~ 65 C
Melting point of mono-unsaturated fatty acids
~ +10 C
Melting point of poly-unsaturated fatty acids
~ -10 C
Why are unsaturated fatty acids not a straight carbon chain like saturated fatty acids?
The carbons don’t hold hydrogens as well, so C makes double bonds to make up for it –> double bonds cause the “bend” in the structure
Polymorphism
More than one form of a substance
- different shapes & ways to be packed together
- different melting poinds
Which crystal form of cocoa butter is the “nicest” for making chocolate?
Type V
How do you make all cocoa butter crystals type V?
Controlled heating and cooling
Temeperin
Describes controlled crystal formation in chocolate
Role of fat in meats
USDA grading is based on fat distribution (marbling of meat)
-More fat = more prime
Essential fatty acids
- Essential to proper metabolism
- Cannot be synthesized by the body (in sufficient amounts)
- Ex) Omega 3, 6
Role of fats in flavor
-Storage of flavor compounds specific for a product that give foods distinct texture/flavor
Role of fats in heat transfer
-Large molecules don’t evaporate and can be heated to very high temps
Frying
Heat transfer with hot fat
List meat grades from least to greatest amount of marbling
- Cutter
- Utility
- Standard
- Select
- Choice
- Prime
