Food Chemistry: Lipids

Definition of Lipids

wide variety of natural products including fatty acids and their derivatives, steroids, terpenes, carotenoids and bile acids, which have in common a ready solubility in organic solvents such as diethyl ether, hexane, benzene, chloroform or methanol.

Lipids are

- insoluble in water

- are present in or derived from living organisms

- Contain more stored energy than any other type of organic compound (9 kcal/gram)

Classification of lipid structures

- based on physical properties at room temperature

- their essentiality for humans

- Structure

Physical Properties at Room Temp

oils are liquid and fats are solid

Essentiality for humans

essential and nonessential fatty acids

Difference Between Fats and Oils

- Fats usually come from animal sources

- Oil, on the other hand is usually a purified form of the fat and usually come from plant sources

Similarity between fats and oils

Both fats and oils form a part of a well defined dietary plan

Lipid classes

- fatty acids,

- triacylglycerols, (triglycerides)

- phospholipids

- steroids

Saturated Fatty Acids

- Contain more C-H bonds

- Solid at room temperature

- Synthesized in animals

- Saturated fats and cholesterols increase risk of atherosclerosis (fatty plaque)

- maximum possible number of hydrogen atoms attached to every carbon atom.

Examples of Saturated FA

beef tallow and butter

Unsaturated Fatty Acids

- Contain less C-H bonds

- Liquid at room temp

- Synthesized in plants

Examples of unsaturated FA

Corn oil, olive oil, and safflower oil

STEARIC ACID

saturated fatty acid with an 18-carbon chain

OLEIC ACID

- Omega 9

- monounsaturated fatty acid

There are three main types of fatty acids

saturated, monounsaturated and polyunsaturated

Trans Fatty Acids

- industrially produced partially hydrogenated fat

- preponderance (most) of trans fatty acids in our diets are derived from the hydrogenation process

- ruminant fat in dairy and meat products (present naturally)

Hydrogenation

- Hydrogenation bubbles Hydrogen gas into a liquid oil (unsaturated) to become saturated

- Increased stability against rancidity

- And a higher melting point

- lose the health benefits associated with PUFA's.

Examples where hydrogenation occurs

breakfast cereals,, cookies, potato chips, crackers and other processed foods they are used to lengthen shelf life.

Trans free Label

if they contain up to half a gram of trans fats per serving

Margarine

- Vegetable oils chemically changed into saturated fats by adding H atoms

- But not all margarines are created equal — some margarines contain trans fat. In general, the more solid the margarine, the more trans fat it contains. So stick margarines usually have more trans fat than tub margarines do

Butterfat

66% Saturated Fat

Palm Kernel Oil

- 86% Sat. Fat

- Tropical Oil

Include: palm oil, palm kernel oil, and fractionated palm kernel oil.

Coconut Oil

- 92% Sat fat

- Tropical Oil

- Though most of the fatty acids in tropical oils are saturated, not all saturated fats are harmful

Comparison of fatty acids

Everything is a combination

Tropical Oils

- Products with this are more resistant to rancidity

- Have longer shelf lives

- Creamy texture

- US diet (3.8 g /day)

- Adding tropical oils in the context of a healthy diet is unlikely to affect blood cholesterol significantly

Benefits of Tropical Oils

- no cholesterol

- No lactose

- Kosher

Palm oil, from the palm fruit

50 percent saturated fat

Palm kernel oil, from the palm seed

It is more saturated (about 80 percent)

Fractionated palm kernel oil

by further processing palm kernel oil to remove the liquid portion, leaving behind even more saturated solids

Palmitic acid (Palm oil main FA)

no effect on cholesterol

Lauric acid (Coconut oil main FA)

may even have some health benefits.

Phosphoglycerides (Phospholipids)

- Phospholipids form the membrane that make up the outer layer of all human cells

- They play a key role in determining what enters and exits every cell.

- When present in food, phospholipids allow fat and water to mix, in turn allowing fats to become part of your blood and move in and out of cells and vessels.

- Derived from soy, canola, sunflower or egg, these natural lipids are essential to healthy cell function

Lecithin (phospholipid)

- Egg yolks, liver, wheat germ and peanuts contain the phospholipid lecithin.

- Your body can only synthesize lecithin if you have sufficient choline in your diet.

- Derived from soybean

Uses of Lecithin

include salad dressings (emulsifiers), baked goods and chocolate

Where can you find phospholipids

soy, milk and lightly cooked meats

Emulsifiers

- molecules with one water-loving (hydrophilic) and one oil-loving (hydrophobic) end

-They make it possible for water and oil to become finely dispersed in each other, creating a stable, homogenous, smooth emulsion.

Common applications of emulsifiers

- bread

- Ice cream

- Chocolate

- Margarine

- Processed Meat

Chocolate emulsifiers

- to provide the right consistency of the chocolate

- If the chocolate has been stored at too high temperatures, its surface may appear dull or white. This is called 'bloom'

Bread emulsifiers

enhanced volume, a softer crumb structure and a longer shelf-life.

Ice-cream emulsifiers

- to promote a smoother texture and ensure the ice-cream does not melt rapidly after serving.

- freeze thaw stability

Margarine emulsifiers

- the required stability, texture and taste.

- the water droplets are finely dispersed in the oil phase

Processed Meat emulsifiers

- meat proteins, fat and water, which are bound together in a stable emulsion

- distribute the fat finely throughout the product.

-Taste

Triacylglycerols

most abundant storage form of fat in animals and plants, and hence the most important dietary lipid

Plant stanols and sterols

- looks like cholesterol

- they travel through your digestive tract, they get in the way

- can prevent real cholesterol from being absorbed into your bloodstream in the small intestine. Instead of clogging up your arteries, the cholesterol just goes out with the waste.

- The compounds lower levels of LDL cholesterol but have little or no effect on "good" HDL cholesterol or triglycerides

- While plant sterols are healthy, extra calories are not

FDA and plant stanols and sterols

- Gave these products the status of a "health claim." This means that experts widely agree (science behind it) on the cholesterol-lowering benefits of stanols and sterols. It also allows manufacturers to advertise the heart-healthy benefits on labels.

Phytosterols (in steroids)

Plant sterols and stanols that inhibit the absorption of cholesterol from the small intestine and, in effect, lower low-density lipoprotein cholesterol in humans.

Sources of phytosterols

- some cooking oils

- salad dressings

- milk

- yogurt

- snack bars

- juices

National Heart, Lung and Blood Institute reports

that adding 2 grams of plant sterols to your daily diet may lower cholesterol by 5 to 15 percent

1-tablespoon serving of sesame oil, corn oil and canola oil has how much phytosterols

92 to 118 milligrams

Examples of Plant Sterols and Stanols

Things that are fortified

Palmitic acid (Palm oil main FA)

no effect on cholesterol