Food Chemicals: FATS
triesters of glycerol with the fatty acids: hence triglycerides
CH2
O-CO-long chain
CH
O-CO-long chain
CH2
CH2OH
water
O-CO-long chain
CHOH
acid or base
+ 3 RCOOH
CH2OH
Fat or triglyceride
glycerol
fatty acids
FATTY ACIDS (natural ones have even numbers of C’s, formed from
acetyl-CoA = CH3CO--- CoA and are cis)
18
15
12
9
7
COOH
3
1
18
15
12
#C’S
# DB'S
4/6
8/10
12/14/16
18
18
18
18
20
20
22
0
0
0
0
1
2
3
0
4
0
9
7
COOH
3
POSITIONS NAME
Butyric/caproic
Caprylic/capric
Lauric/myristic/palmitic
Stearic
9(-10) Oleic
9;12
Linoleic
9;12;15 Linolenic
Arachidic
5;8;11;14 Arachidonic
Behenic
1
SOURCE
Butter
Coconut
Palm
Beef fat
Olive Oil
Soy Bean
Fish/Liver
Peanut
Fish/Liver
Canola
(Rapeseed)
Systematic names:
Butyric acid
Caproic acid
Capric acid
Lauric acid
Palmitic acid
Stearic acid
Arachidic
Behenic
= butanoic acid
= hexanoic acid
= decanoic acid
= dodecanoic acid
= hexadecanoic acid
= octadecanoic acid
= eicosanoic acid
= docosanoic acid
4C
6C
10C
12C
16C
18C
20C
22C
butane
hexane
decane
dodecane
hexadecane
octadecane
eicosane
docosane
DHA = docosahexaenoic acid 22C – 6 C=C (at 4,7,10,13,16,19
positions) - found in fish oils, membranes of eyes, brain
Linoleic acid is essential in our diets (we can make the others)
Arachidonic acid: COX enzymes convert to prostaglandins, etc.
Iodine # = g I2 per 100g of oil (a measure of unsaturation)
OIL
% SATD
% MONO
% POLY
IODINE #
Coconut
Butter
Palm
Lard
Margarine
Olive
Peanut
CANOLA
Cottonseed
Corn
Fish
Soybean
Safflower
Sunflower
Linseed
93
6
1
57
44
36
46
7
10
15
21
7
26
14
73
49
61
22
29
12
30
32
52
57
14
10
11
24
14
19
62
76
70
8-10
25-40
37-54
45-70
80-85
75-95
85-100
~115
100-117
115-130
120-180
125-140
130-140
130-145
170-205
All natural fatty acids are all cis: but can be isomerized to trans
trans-isomers are higher melting than cis-isomers: solid fats vs. oils
Saturated fats (no double bonds): pack better, higher Mp = SOLIDS
Can increase mp of OIL by HYDROGENATION and/or
ISOMERIZATION to get solids = margarine
The more double bonds, THE HIGHER THE IODINE NUMBER
a) BUTTER has IN=30, mostly C4-C6-C8 short chain saturated acids:
IN varies with the milk source (diet of the cow)
b) SOYA OIL has IN=120-140, mostly C18 with 2-3 double bonds: part
hydrogenated, part isomerized to get Margarine, IN ~85
(NOTE: olive oil also has IN=90, but is all cis and thus is an OIL)
CANOLA OIL used to be mostly C22 but selective plant breeding has
produced modern Canola strains that are mostly C18:
7% satd; 61% mono unsaturated; 32% polyunsaturated
Now mostly (91%) C18:
C18-1 = Oleic (55%)
C18-2 = Linoleic (26%)
C18-3 = Linolenic (10%)
so 0.91 x 26% = 21% Linoleic in Canola
w-6 and w-3 oils
6
COOH
1st double bond at C-6 from end
= w-6
COOH
3
1st double bond at C-3 from end
w-6 FATTY ACID
w FATTY ACID
w
g-Linolenic acid
aLinolenic acid
Plant Oils
Fish oils
Modern diets are high in w-6, about 10x the w-3, while old diets were
about 1:1
Current theory is that w-3 gives lower blood triglyceride levels
PLUS 1g of w-3 per day has been shown to give a 20% reduction in
heart-related deaths
Lack of w-3 leads to heart disease, thrombosis, atherosclerosis
Modern Canola has about 11% w-3 while decreasing Erucic acid
C22-1(13-14) to <1%
Erucic acid was prevalent in old rapeseed oil and has been
implicated in heart lesions
As a matter of interest see: Monsanto vs. Schmeiser – a well-documented
court case where Monsanto sued Schmeiser for patent infringement when
he saved seeds from a Round-up Ready (a genetically modified Canola
strain) Canola that had blown into his field from neighbouring areas
Trans-fats (US and CAN require labelling)
Modern margarine has some cis-bonds isomerized to trans to
increase ‘solidity’:
Hard margarine
~12% trans-fats
Soft margarine
~5% trans-fats
Becel
0% trans-fat but still ~12% saturated fat
Current hypothesis:
trans fats increase LDL’s a few % = a small
increase in risk of heart attack
Ban on use of trans-fats in restaurants comes into effect in BC in
September ’09 (already adopted, then abandoned in Calgary)
DISADVANTAGES of unsaturated fats: easier to oxidise
-CH=CH-CH-CH=CH|
H
-CH=CH-CH-CH=CH•
Allylic hydrogen is easily oxidised to a free radical which further
reacts with oxygen to cleave the chain and produce SMELLY short
chain fatty acids (under-arm sweat and rancid butter smell)
An ANTIOXIDANT (usually ArOH) can supply a H• back to this free
radical and reform the fat, before it has had time to react with oxygen:
the resulting phenoxy radical ArO• is stable.
NOTE: Butylated hydroxytoluene (BHT) is 2-t-butyl-4-methylphenol
and it is commonly added to cereals for the same reasons (next page)
Hence need to protect fats with antioxidants:
OH
OH
O
HO
OMe
BHT
BHA
butylatedbutylatedhydroxytoluene hydroxyanisole
allowed at 0.01-0.02%
VITAMIN E
a-tocopherol
too expensive for food
Note: in these the ArO• is highly crowded which makes it less reactive
FLAVINOIDS
eg. epicatechin are found in green
and black teas, red wines and also
have antioxidant properties:
reduced heart disease?
OH
HO
O
OH
ANTHOCYANINS
R2, R5, R7 virtually always OH
and other R groups may be OH
Powerful anti-oxidants found
as pigments in berries, flowers,
vegetables, outer skins:
blueberries, blood oranges, jalapeno
peppers, purple onions, red apple skins, many others
OH
OILS: Vegetable oil production 80-100 Mtons/y mostly as
Soy, Palm, Canola (about ~20% each) plus minor amounts of
coconut and peanut oils
Soft margarine has
Low fat soft margarine has
80% fat
40%fat
16% water
56% water!!!
Fats don’t dissolve in water, so have to emulsify them
COO- Na+
-OOC
-OOC
COOCOO-
-OOC
-OOC
-OOC
COOCOO-
A piece of dirt (grease): hydrocarbon tails
embed in grease; water surrounds the COO- groups and the grease ‘dissolves’”
For fats can use phospholipids: eg. Lethicin (egg yolks)
C17H31COO-CH2
|
C17H31COO-CH
|
+
CH2OPO3CH2CH2NMe3
greasy end binds fat
Remember bile acids transport fats
thru the intestine for use
Cholic acid:
ionic end binds water
Similarly mono- or diglycerides bind fats to sugars:
C17H31COO-CH2
|
CH-OH
|
CH2-OH
greasy end binds fat this H-bonds to sugar -OH’s
so used in shortenings, cakes and cookies: can get up to 40%
sugar in a cake without it being ‘crunchy’; fats make cookies
more ‘crumbly’
FAT SUBSTITUTES
Some are ‘modified’ starches, have the texture of fat but 4 kcal/g
rather than 9 kcal/g
OLESTRA
CH2OH
H
O H
OHH
HO
O
H OH
CH2 O H
HO H HO CH2 OH
HO
each -OH of sucrose is
converted to a
-OCO(CH2)6,7,8CH3
H
the resulting molecule cannot pass through the intestine, so is not
absorbed: because it is so ‘greasy’ it can lubricate the intestines too
much so ‘anal leakage’ can occur carrying with it some fat soluble
vitamins
Natural Waxes are long chain acid / long chain alcohol esters:
CH3(CH2)24/26COO(CH2)29/31CH3 = beeswax
Carnauba wax (used for car polish and coatings on ‘no-mess’
candies like Smarties, M+M’s) contains some pendant
HO~~~~COOH that polymerize and give it its hardness
CANNOT DIGEST THESE
Jojoba oil is an unsaturated ‘wax’ that is not metabolised: under
study as a frying oil
CH3(CH2)7CH=CH(CH2)mCOO(CH2)nCH=CH(CH2)7CH3
m = 9,11; n=10,12 chain lengths vary
Used in cosmetics as a moisturizer and in many skin and hair care
products; also under investigation as a diesel oil
Cholesterol, Fats and Oils, Salt and Calories in Foods (per 100g)
Food
Cholesterol
Beef, raw
Chicken
Cheese (cheddar)
Corn oil
Eggs, whole
Hot dog, all beef
Milk, whole
Olive oil
Margarine (Becel)
Butter
Tuna (canned)
Salmon (canned)
Peanut butter (unsalted)
Yogurt (plain, skim milk)
Oil or Fat (grams)
Salt
mg
Satur Mono-un Poly-un
mg
91
85
105
0
548
51
14
0
0
215
63
35
0
6
2.7
1.3
21.1
12.7
3.4
12.7
2.3
13.5
10.0
50.5
0.2
1.0
9.7
1.0
54
70
615
0
142
1026
40
0
700
576
338
487
17*
77
2.7
1.5
9.4
24.2
4.5
14.8
1.1
73.7
30.0
23.4
0.1
1.8
23.3
0.4
0.5
1.0
0.9
58.7
1.4
1.2
0.1
8.4
40.0
3.0
0.2
2.7
15.2
0.04
Cal
152
165
400
884
143
296
60
884
700
720
116
140
588
56