Lipids Part II

Physical Properties Energy value Phase Differences Solubility Melting / solidification points 2

Energy Energy is released when things react with oxygen (burning or combustion) Triglycerides react well with oxygen Store energy for long term use Contain more than twice as much energy as carbohydrates Digest more slowly than carbs, so they provide a slow steady release of energy 3

Phase Differences Fats that usually come from animals are saturated fats. They are denser than oils and in a solid phase at room temperature. Most plant oils are unsaturated. The bend in their chemical structures makes oils less compact, so they are liquid at room temperature. Exceptions include Coconut and Palm Oil, which are over 80% saturated fats.

Solubility Fats and oils don’t dissolve in water An emulsifier can be used to allow them to mix. 5

Melting / Solidification Fats have a temperature range for melting and solidifying Each fat is a collection of 3 fatty acids, all with different melting / solidification points. 6

Fats Used in Food Processing Hydrogenated Fats Partially Hydrogenated Fats Trans Fats

Which is healthier? The top margarine is better for you. It contains more total fat, but less unhealthy (saturated) fat than the bottom one. Remember, it is the saturated fat, not the total fat content, that matters most. Partially hydrogenated – a process of adding hydrogen to an unsaturated oil to make it partially saturated so it can solidify at room temp. Makes it more useful but less healthy

What is Hydrogenation? the process of adding hydrogen to an unsaturated fat makes the fat either partially or fully saturated allows liquid oils to be solidified at room temperature.

Why do we use partial hydrogenation? Very useful for creating things like margarine and shortening. Has a longer shelf-life than liquid oils Changes the texture of foods containing oils Heavy use by the fast-food industry. For example: many restaurant chains use blocks of shortening for deep-frying rather than liquid oil.

Hydrogenating vegetable oils results in the creation of trans fats! Traditionally, baked goods used lard (a saturated animal fat). However vegetable oils are much cheaper, so processors have switched from lard to partially hydrogenated vegetable oils. Hydrogenating vegetable oils results in the creation of trans fats!

Trans Fats – MAN MADE These kid of fats are found in fried foods, commercially baked goods, processed foods, and margarine. These fats elevate bad cholesterol and should be avoided! Most unhealthy type of fat – causes significant increase in risk of heart disease and other health issues As little as 1 gram of trans fat a day can double your risk of heart disease.

Cis vs. Trans Unsaturated fats are healthy because the double bond causes the shape of the molecule to bend. This bent shape is called a “cis” configuration. Fat molecules can’t easily stack. When an unsaturated fat is “hydrogenated” it is converted to a saturated fat. Trans fat is a by-product of hydrogenation. There is still a slight bend, but they are much more stackable than “cis” fats.

Legislation and Safety Many jurisdictions are banning or limiting trans fats Trans fat content is required on food labels in Canada. Government agencies say there is no safe level of trans fat consumption. New technologies are allowing for safer methods of partially hydrogenating oils Alternatively, some processors are switching back to natural saturated fats, like lard.

Triglyceride subgroups Fat on edge of meat and marbling throughout. Usually high in saturated fats (esp. red meats); some contain oleic acid Animal fats Cod liver oil Long chains of polyunsaturated fatty acids; some very high in vitamins A and D Fish oils Corn, peanut, sunflower, olive, and sesame oils Unsaturated; most common fat in North American diet Fats containing oleic or linoleic acids Cocoa butter Highly saturated Vegetable butters Soybean oil, wheat germ oil Highly unsaturated Fats containing linolenic acid Coconut palm oil / palm kernel oil Usually low in unsaturated fatty acids; high in saturated fatty acids Fats from the coconut palm Cow’s milk Contain some saturated fatty acids Milk fat Examples Description Triglyceride Subgroup

Functions of Fats in Foods Why do we use fats in foods? Tenderizing Aeration Emulsions Flavor

Tenderizing / Aeration Since water and fat don’t mix, the fats seal in moisture. Foods don’t dry out. Fats also form bubbles around air molecules. This helps baked goods rise and get fluffy.

Emulsions Emulsions – phospholipids (the 2nd category of lipids) can be used to mix oil and water. Mayonnaise (lecithin) Thin mints cookies (soy lecithin – this is in everything! )

Flavour Fats carry flavour Margarine, olive oil, bacon fat, etc Health concern – many low fat foods replace fat with added sugar or salt (Canadians should consume no more than 10% of their total calorie intake as added sugar – this is roughly 30-48 grams of added sugar). Hypertension / high blood pressure Diabetes

ISSUE - Spoilage and Rancidity Fats can spoil and become rancid over time Why are potato chip bags full of air? It’s not air! Chip bags contain pure nitrogen. Why? Oxygen reacts with fats to make them turn rancid over time. Vacuum sealing Bottling / canning

3. Sterols - Cholesterol Required for making vitamin D and some hormones Produced in the liver, from glucose and saturated fatty acids Body produces all you need; most dietary cholesterol is useless Too much dietary cholesterol leads to heart disease

LDL and HDL Low density lipoprotein High density lipoprotein Transport cholesterol and other molecules through the blood stream. LDL – allows cholesterol to build up more quickly and gather in arteries HDL – helps remove cholesterol from bloodstream

Omega-3 Fatty Acids Found in many fish (esp. cold water) Heart healthy Sardines, salmon, tuna, herring are highest Heart healthy Make it more difficult for fats to build up in arteries Links to better brain health Long term memory Less degeneration Fats are essential for the brain and nervous system