Food Biotechnology Dr. Kamal E. M. Elkahlout Food Biochemistry 5 Vitamins and minerals
Food Biotechnology Dr. Kamal E. M. Elkahlout Food Biochemistry 2 Lipids
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Transcript of Food Biotechnology Dr. Kamal E. M. Elkahlout Food Biochemistry 2 Lipids
Food BiotechnologyDr. Kamal E. M. Elkahlout
Food Biochemistry 2Lipids
Lipids: Fats & Oils
Characteristics of Lipids • Lipids are composed of C, H, O
– long hydrocarbon chain
• Do not form polymers– big molecules made of smaller subunits– not a continuing chain
fat
Fats store energy• Long HC chain
– polar or non-polar?– hydrophilic or hydrophobic?
• Function:– energy storage
• very rich• 2x carbohydrates
– cushion organs– insulates body
• think whale blubber!
Why do humanslike fatty foods?
ClassificationMany ways of classifying lipids:
Structural characteristics• Neutral fats – found in subcutaneous tissue and around organs
• Phospholipids – chief component of cell membranes
• Steroids – cholesterol, bile salts, vitamin D, sex hormones, and adrenal cortical hormones
• Fat-soluble vitamins – vitamins A, E, and K
• Eicosanoids – DHA (docosahexaenoic acid), EPA (eicosapentaenoic acid) (sources of omega 3,6 & 9)
• Waxes
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Fatty Acids
• Long-chain carboxylic acids• Insoluble in water• Typically 12-18 carbon atoms (even number)• Some contain double bonds
corn oil contains 86% unsaturated fatty acids and
14% saturated fatty acids
Fatty Acid Structure
• Carboxyl group (COOH) forms the acid.• “R” group is a hydrocarbon chain.
Fatty Acids
• The Length of the Carbon Chain– long-chain, medium-chain, short-chain
• The Degree of Unsaturation– saturated, unsaturated, monounsaturated,
polyunsaturated• The Location of Double Bonds
– omega-3 fatty acid, omega-6 fatty acid
The Length of the Carbon Chain
Short-chain Fatty Acid (less than 6 carbons)
Medium-chain Fatty Acid(6-10 carbons)
Long-chain Fatty Acid(12 or more carbons)
SaturatedFatty Acid
UnsaturatedFatty Acid
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Saturated and Unsaturated Fatty Acids
Saturated = C–C bondsUnsaturated = one or more C=C bonds
COOH
COOH
palmitoleic acid, an unsaturated fatty acid
palmitic acid, a saturated acid
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Properties of SaturatedFatty Acids
• Contain only single C–C bonds• Closely packed • Strong attractions between chains• High melting points• Solids at room temperature
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Properties of UnsaturatedFatty Acids
• Contain one or more double C=C bonds• Nonlinear chains do not allow molecules to
pack closely• Few interactions between chains• Low melting points• Liquids at room temperature
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Structures
Saturated fatty acids• Fit closely in regular pattern
Unsaturated fatty acids• Cis double bonds
COOHCOOHCOOH
C CH H
COOHcis double bond
Fatty Acids are Key Building Blocks
• Saturated Fatty Acid
• All single bonds between carbons
Monounsaturated Fatty Acid(MUFA)
One carbon-carbon double bond
Polyunsaturated Fatty Acid(PUFA)
More than one carbon-carbon double bond
Location of Double Bonds
• PUFA are identified by position of the double bond nearest the methyl end (CH3) of the carbon chain; this is described as a omega number;
• If PUFA has first double bond :– 3 carbons away from the methyl end=omega 3
FA– 6 carbons from methyl end=omega 6 FA
Omega-3
Omega-6
Degree of Unsaturation
• Firmness– saturated vs. unsaturated
• Stability– oxidation, antioxidants
• Hydrogenation– advantages, disadvantages
• Trans-Fatty Acids– from hydrogenation
Cis and Trans fats– isomerisation of cis to
trans occurs under extreme conditions of hydrogenation
– double bonds in fatty acids are almost always cis, which causes bends in the carbon chain.
– these bends do not allow the close packing and attractions of saturated fatty acids. Therefore, most unsaturated fatty acids are liquid at room temperature.
Cis-9-octadecenoic acid(Oleic acid)
Trans-9-octadecenoic acid(Elaidic acid)
Hydrogenation Process
• liquid hardens by hydrogenation (addition of hydrogen) – reduce the degree of
unsaturation
• briefly, oils are exposed to hydrogen gas at high tempt (2-10 atm, 160-220 0C) in the presence of 0.01-0.2% fine divided nicklel
Saturated vs. unsaturatedsaturated unsaturated
CLASSIFICATION OF FATTY ACIDS PRESENT AS GLYCERIDES IN FOOD FATS
I. Saturated Fatty Acids
Butyric Butanoic CH3(CH2)2COOH butterfat
Caproic Hexanoic CH3(CH2)4COOH butterfat, coconut and palm nut oils
Caprylic Octanoic CH3(CH2)6COOH coconut and palm nut oils, butterfat
Capric Decanoic CH3(CH2)8COOH coconut and palm nut oils, butterfat
Lauric Dodecanoic CH3(CH2)10COOH coconut and palm nut oils, butterfat
Myristic Tetradecanoic CH3(CH2)12COOH coconut and Palm nut oil, most animal and plant fats
Palmitic Hexadecanoic CH3(CH2)14COOH practically all animal and plant fats
Stearic Octadecanoic CH3(CH2)16COOH animal fats and minor component of plant fats
Arachidic Eicosanoic CH3(CH2)18COOH peanut oil
Common Name
Systematic Name
Formula Common source
Common Name
Systematic Name
Formula Common source
II. Unsaturated Fatty Acids A. Monoethenoic Acids
Oleic Cis 9-octadecenoic C17H33COOH plant and animal fats
Elaidic Trans 9-Octadecenoic C17H33COOH animal fats
B. Diethenoic AcidsLinoleic 9,12-Octadecadienoic C17H31COOH peanut, linseed, and
cottonseed oils C. Triethenoid Acids Linolenic 9,12,15-Octadecatrienoic C17H29COOH linseed and other seed
oilsEleostearic 9,11,13-Octadecatrienoic C17H29COOH peanut seed fats
D. Tetraethenoid Acids
Moroctic 4,8,12,15-Octadecatetraenoic C17H27COOH fish oils
Arachidonic 5,8,11,14-Eicosatetraenoic
C19H31COOH traces in animal fats
Common and Systematic Names of Fatty Acids
Common Name
Systematic Name
Formula Common source
A. Monoethenoic Acids
Oleic Cis 9-octadecenoic C17H33COOH plant and animal fats
Elaidic Trans 9-Octadecenoic C17H33COOH animal fats
B. Diethenoic AcidsLinoleic 9,12-Octadecadienoic C17H31COOH peanut, linseed, and
cottonseed oils C. Triethenoid Acids Linolenic 9,12,15-Octadecatrienoic C17H29COOH linseed and other seed
oilsEleostearic 9,11,13-Octadecatrienoic C17H29COOH peanut seed fats
D. Tetraethenoid Acids
Moroctic 4,8,12,15-Octadecatetraenoic C17H27COOH fish oils
Arachidonic 5,8,11,14-Eicosatetraenoic
C19H31COOH traces in animal fats
C4 - 8 -
C6 - 4 970
C8 16 75
C10 31 6
C12 44 0.55
C14 54 0.18
C16 63 0.08
Fatty Acids M.P.(0C) mg/100 ml Soluble in H2O
C18 70 0.04
CHARACTERISTICS OF FATTY ACIDS
Effects of Double Bonds on the Melting Points
16:0
6016:1 118:0 6318:1 1618:2 -518:3 -1120:0 75
F. A. M. P. (0C)
20:4 -50
Lipid Formation
Glycerol Fatty Acid
GLYCERIDES
Monoglyceridea Diglyceride
H2C OH
HC OH
H2C OOC (CH 2)16CH3
H2C O
HC OH
H2C OOC (CH 2)16CH3
C (CH 2)16CH3
O
Triglyceride
H2C O
HC O
H2C OOC (CH2)1 6CH3
C (CH2)1 6CH3
O
OC (CH2)1 4CH3
( C1 8)
(C1 6)
(C1 8)
Triglycerides• Structure
– Glycerol + 3 fatty acids• Functions
– Energy source• 9 kcals per gram• Form of stored energy in adipose
tissue– Insulation and protection– Carrier of fat-soluble vitamins– Sensory properties in food
FAT AND OILS Mostly Triglycerides:
Triglycerides• Food sources
– fats and oils• butter, margarine, meat, baked goods, snack
foods, salad dressings, dairy products, nuts, seeds
– Sources of omega-3 fatty acids• Soybean, canola, walnut, flaxseed oils• Salmon, tuna, mackerel
– Sources of omega-6 fatty acids• Vegetable oils
MELTING POINTS OF TRIGLYCERIDES
C6 -15
C12 15
C14 33
C16 45
C18 55
C18:1 (cis) -32
Triglyceride Melting Point (°C)
C18:1 (trans) 15
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Learning Check
How would the melting point of stearic acid compare to the melting points of oleic acid and linoleic acid? Assign the melting points of –17°C, 13°C, and 69°C to the correct fatty acid. Explain.
stearic acid (18 C) saturatedoleic acid (18 C) one double bondlinoleic acid (18 C) two double bonds
Phospholipids• Structure
– Glycerol + 2 fatty acids + phosphate group
• Functions– Component of cell membranes– Lipid transport as part of lipoproteins– Emulsifiers– Phosphatidylcholine
• Food sources– Egg yolks, liver, soybeans, peanuts
Phospholipids• Hydrophobic or hydrophilic?
– fatty acid tails = hydrophobic– PO4 = hydrophilic head– dual “personality”
interaction with H2O is complex & very important!
It likes water & also pushes it away!
A Phospholipid
Steroids
• ex: cholesterol, sex hormones• 4 fused C rings
– different steroids created by attaching different functional groups to rings
cholesterol
Sterols: Cholesterol• Functions
– Component of cell membranes– Precursor to other substances
• Sterol hormones• Vitamin D• Bile acids
• Synthesis– Made mainly in the liver
• Food sources– Found only in animal foods
WAXES Fatty acids + Long chain alcohol
Important in fruits:
1. Natural protective layer in fruits, vegetables, etc.
2. Added in some cases for appearance and protection.
Beeswax (myricyl palmitate)
FAT SOLUBLE VITAMINS (A,D,E,K)
Vitamin A: CH2OH
CH3 CH3
CH3
CH3H3C
1234
5
678
9
Vitamin D2:
Vitamin E:
Deterioration of Fats
Rancidity • Is the chemical deterioration of fats• Are of two types
– Oxidative rancidity– Hydrolytic rancidity
Oxidative rancidity
• A hydrogen on the fatty acid molecule is displaced by energy(heat or light) to give free radical.
• Molecular oxygen can unite with the carbon that carries the free radical and form a peroxide.
• The energy from this activated peroxide can displace a hydrogen from another unsaturated fatty acid.
• The displaced hydrogen unites with the activated peroxide to form a hydroxide.
• The hydro-peroxide is very unstable and can decompose into compounds with shorter carbon chains. These include ketones, aldehydes and fatty acids that are volatile and contribute to off flavoures.
Oxidative Rancidity
Catalysts– Salt and trace metals– Bacteria and molds– Water– Light
Prevention• Addition of chelators• Use of antioxidants• Air tight storage.
Hydrolytic Rancidity
• Is the reaction between a triglyceride and 3 water molecule to give a glycerol and 3 free fatty acids.
Catalysts :• Heat• Fat splitting enzymes called lipases.
Prevention• Keep moisture level low• Inert gas packaging• sterilization
Functional Properties of Lipids
• Flavour• Basting – add crispiness to product• Add moisture to foods• Assist in browning• Frying • Aerating• Prevents products from sticking