& Animal Plant Fats & Oils aka Lipids
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Major food lipids
Triglycerides
Working definition: Organic compounds (CHO) that do not mix with Water
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We will use the term lipids "mostly"
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Fat soluble vitamins: A, D, E, K Cholesterol Some plant pigments like beta-carotene Flavor or volatile lipids (small molecules which are soluble in lipids)
Roles of lipids -- lecture topics
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Caloric Values
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Energy source Texture Essential fatty acids Fat soluble vitamins: A, D, E, K Cholesterol Some plant pigments like beta-carotene Flavor and flavorings Heat transfer ("frying")
Physicists! definition:
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1 calorie raises 1 gram of water 1C 1 kcal raises 1000 grams of water 1C
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(actually, modern physicists use Joules instead of calories, but most nutritionists still use nomenclature related to calories)
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Caloric Values
Carbohydrates Proteins Lipids 4 kcals/gram 4 kcals/gram 9 kcals/gram
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Caloric Values
Nutritionists use the term Calorie (big C) to imply kcal Or in Europe - welcome to the metric system! 4.2 joules = 1 calories or 4.2 kilojoule (kj) = 1 kcal = 1 Cal
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So we can say that Lipids have twice the amount of Kcalories as Carbohydrates* or Proteins. *digestible carbohydrates
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Recommendations for Fat Intake
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An example of `low fat' franks
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Recommendations of the USDA"Dietary Guidelines for Americans" ref: fats
Choose a diet low in fat, saturated fat, and cholesterol
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3% fat (by weight) 20% of calories from fat
Eat less than 30% of total calories from fats and oils
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Role of Fats
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Energy source Texture
Texture
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Roles of Fats
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Textural modification in foods (Shortens protein network in bread & cake doughs)
Smooth and moisten (baking) Crumbly textures
Energy source Texture
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Adipose tissue
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Coatings
Flavorful coatings Water resistant coatings
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E.g. Marbling of meat USDA grading is based on fat distribution
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Roles of Fats
Prime Choice Select ! ! !
Energy source Texture Essential fatty acids
Standard
Utility
Cutter
Essential fatty acids
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Roles of fats
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Are essential to proper metabolism Cannot be synthesized by the body
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Energy source Texture Essential fatty acids
Fat soluble vitamins: A, D, E, K Cholesterol
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(or at least in sufficient amounts)
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Linoleic ("6) Linolenic ("3)
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These topics are for nutrition classes...
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Sources of Cholesterol
! From foods we eat Cholesterol is found in animals or meat. Cholesterol does not occur in plants. ! Made in the body Related to genetics (the family tree) also related to the types of fatty acids consumed in our diet.
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Roles of fats
Energy source Texture Essential fatty acids
Fat soluble vitamins: A, D, E, K Cholesterol Beta carotene (plant pigments)
Roles of fats
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Roles of fats -- aroma
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Energy source Texture Adipose Essential fatty acids Fat soluble vitamins: A, D, E, K
Most aromas are lipids "compounds which are not water soluble" Natural, Cooked, and Synthetic chemicals Without fat - aroma is a problem FAT FREE - Flavor (aroma) Free
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Cholesterol
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Pigments
Flavor and flavorings
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Bad aromas from 1. free fatty acids (hydrolytic rancidity) 2. oxidation of fatty acids (oxidative rancidity)
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Roles of fats
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Roles of fats: heat transfer
Energy source Texture Adipose Essential fatty acids Fat soluble vitamins: A, D, E, K Flavor and flavorings Cholesterol Beta Carotene Flavor Heat transfer (also fat transfer!!!)
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Large molecules do not evaporate Can be heated to very high temperatures Heat transfer with hot fat is called: frying
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Important Lipids
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U.S. Domestic Disappearance of Fats & Oils Fats 1995 2000 2002 2004 2005
(billions of pounds)
Fats and oils are members of the Triglyceride family Oils are liquids at room temperature Fats are solids at room temperature
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Soybean Tallow Canola Corn Cottonseed Lard Palm Olive Sunflower
13.5 1.3 1.3 1.3 1.0 0.6 0.3 0.2 0.2
16.3 1.4 1.7 1.6 0.7 0.6 0.3 0.5 0.2
17.1 1.4 1.3 1.6 0.6 0.6 0.3 0.5 0.3
17.4 1.5 1.6 1.6 0.7 0.6 0.8 0.5 0.2
18.0 1.5 1.7 1.7 1.0 0.6 1.0 0.6 0.4
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Oil Refining
Most food oils are "refined" that is separated from the plant seeds with organic solvents (Chemical Means).
FROM A FRUIT...
Olive Oil is different from all other vegetable oils because it comes from a fruit (olives, the stone-fruit of olive trees) and not from seeds. This has some
The solvents are then boiled away leaving the oil and other plant compounds.
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important consequences.
MILD TECHNOLOGY, NATURALLY...
Because a fruit is rich in water, its oil can be extracted by purely mechanical means.
Virgin
The word "virgin" used by the legislation to describe olive oil means precisely this: "That the oil has been extracted from the olives using purely mechanical means."
After crushing of the fruit, water and oil can also be easily separated by centrifugation.
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THE IMPORTANCE OF THE "MINOR" CONSTITUENTS
Because fruits are living organs with an active metabolism, olives are rich in a large number of minor compounds. While the refining process of seed oils "with organic solvents" aims at eliminating all substances but the triglycerides, the extraction process of olive oil keeps minor components from the fruit's metabolism.
HEALTHY PROPERTIES...
The antioxidant components of virgin olive oil play a role in preventing chronic diseases, particularly those affecting the cardiovascular system.
THE SENSORY PROFILE...
The first sensory requirement of a good olive oil is the absence of sensory defects.
If a virgin olive oil has a detectable sensory defect it cannot be classified as extra virgin.
The second role of the minor from components the fruit's metabolism consists in the fact that they are responsible of the sensorial properties of the oil.
Defects come from rancidity or oxidation
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The second step of sensory evaluation and appreciation of an oil consists in defining its main sensory character or category
- the (taste) perception of bitterness, - the (irritation) perception of pungency or spicy (piquancy)
In order to facilitate consumers' choice, olive oil producers, classify olive oils in three main sensory categories:
mild round sharp
MYTHS, SYMBOLS AND BEAUTY...
MYTHS, SYMBOLS AND BEAUTY...
Its symbolic presence in paradise is described in the sacred texts of the Christian, Judaic and Islamic religions Since an olive branch was brought back by a dove to Noah's ark, the olive has been considered as a symbol of peace
The olive tree and olive oil are deeply linked to the Mediterranean culture
Mediterranean basic food triad
wheat-olive-vine bread-oil-wine
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OLIVE OIL FRAUD
Italian extra virgin olive oil has become so lucrative that adulterated olive oil has become the biggest source of agricultural fraud problems in the European Union. Some oil labeled "extra virgin" is diluted with cheaper olive oils or other vegetable oils. In some cases, lampante, or "lamp oil," which is made from spoiled olives fallen from trees, is used, even though it can't legally be sold as food. One fraud ring is accused of coloring lowgrade soy oil and canola oil with industrial chlorophyll, and flavoring it with beta-carotene. The FDA doesn't routinely test imported olive oil for adulteration, and some products are difficult to test.
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Common fats and oils The building blocks
OH OH
OH
Triglyceride
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Fatty Acids & Hydrolysis
To take off the fatty acids, one method is
Hydrolysis: treatment of fats to give free fatty acids
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Free fatty acids in food oils or fats make the lipid "rancid"
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Triglyceride hydrolysis
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Saturated and Unsaturated Fatty acids
For digestion, we also need to hydrolyze the fatty acids off the glycerol ! There!s that word hydrolysis again... We use enzymes called lipases Q: Why do we care? A: Only free fatty acids are absorbed
Normal hydrolysis of triglycerides breaking off the fatty acids (blue) by lipase (orange)
Fats, Double Bonds & Saturation (everything you were afraid to ask)
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The world!s shortest (and oversimplified) explanation of double bonds, saturation and unsaturation follows ...
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See McGee pp. 603-604
Physical Properties of Fatty Acids
Saturated fatty acids have high melting points ~ +65C (fat) Mono-Unsaturated fatty have low M.P.'s ~ +10C (oil) Poly-Unsaturated fatty acids have even lower M.P.'s ~ -10C (oil)
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Triglyceride Melting Points
S S S +70C S U S S S U +35C U U S U S U +20C
Triglycerides
Is the oil or fat from one source (beef or Is cocoa butter (chocolate) 100%
S U S +35C chocolate)made of only one triglyceride?
U U U
+5C
Fatty acids in Beef and Cocoa butter
Sat Beef 50% UnSat 50% 40%
The melting point of triglycerides
SSS SSU SUU UUU
(70C) (35C) (20C) (5C)
Beef Cocoa
30% 2%
50% 80%
20% 15%
2% 1%
Cocoa 60%
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"It melts in your Mouth"
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What's with the OMEGA numbers?
Nutritionists are interested in the end of the molecule farthest from the acid group So the "last carbon" is like the last letter of the Greek alphabet -- " They number in from the (omega) end until they come to the 1st double bond
"3 "9 "6
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Average Fatty Acid Composition of Fats & Oils
(% by wt)
Fats&Oils Soybean Canola Sunflower Corn Olive Palm Lard Tallow
16:0 18:0 18:1 18:2 11 4 6 13 10 44 27 27 4 2 5 3 2 4 11 7 22 56 20 31 78 40 44 48 53 26 69 52 7 10 11 2
18:3 8 10 1 1 -
Unsaturated fatty acids are unstable with oxygen
! Oxygen will attack the double bonds in an unsaturated fatty acid ! The reaction with oxygen will break a unsaturated fatty acid into smaller molecules which have more aroma (smell) than the original fatty acid. ! The more unsaturated the fatty acid is (that is the more double bonds): the more reactive it is with oxygen.
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Lipid Oxidation Paradox
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New York City passes trans fat ban
NYC to restaurants: No trans fat
NEW YORK - The Board of Health voted Tuesday to make New
Saturated fatty acids (no double bonds) Slow to oxidize (good) Increased risk of heart disease (bad) Polyunsaturated fatty acids (multiple double bonds) Rapidly oxidized (bad) Decreased risk of heart disease (good) Monounsaturated fatty acids good! (Oleic acid)
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York the nation's first city to ban artery-clogging artificial trans fats at restaurants -- from the corner pizzeria to high-end bakeries. Restaurants had to eliminate artificial trans fats from all of their foods by July 2008.
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Soy Bean Oil and Hydrogenation
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Hydrogenation
Soy bean oil contains a lot of polyunsaturated fatty acids (which makes it an oil) To make a fat out of soy bean oil, the number of double bonds must be reduced. That is: these unsaturated fatty acids should be saturated with hydrogen!
H C
H C
H
H C H
+ H2
Hydrogen Gas
C H
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Unsaturated
Saturated
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But we do need to know a little more about
Double Bonds
trans Fatty Acids are By-products of Hydrogenation
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A double bond can exist in two ways, commonly referred to as CIS & TRANS double bonds
H C
H C
H C C H
Unsaturated & trans-fatty acid By-product of Hydrogenation
Unsaturated & cis-fatty acid
Double Bonds
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Even more about...
Cis double bonds are formed in nature Trans double bonds are formed by synthetic chemistry processes called: Hydrogenation
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Trans fatty acids formed from "Hydrogenation" are " Artificial" "Synthetic" or "Un-Natural"
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