LECTURE 6 - ANIMALS AND VEGETABLE FATS, OILS, AND WAXES

Fats and oils

predominantly tri-esters
(triacylglycerols, triglycerides) of glycerol and
aliphatic fatty acids

Waxes

esters of long-chain fatty acids (24-28
carbon atoms) with long-chain primary alcohols
(16-36 carbon atoms) or alcohols of the steroid
group.

Lipids

Broad group of nonpolar chemical substances.

Nonpolar Lipids

Insoluble in water, soluble in organic solvents.

Polar/amphipathic lipids

Fatty acids, cholesterol,
sphingolipids, glycerophospholipids (mainly
lecithins)

Phospholipids

Include lecithins and sphingomyelins, essential for membranes.

"oil" or "fat"

typically selected based on the
material's physical condition and tradition.

Triacylglycerols

composed of glycerol (a
trihydric alcohol) and three fatty acids, account for more than
95% of the weight of the majority of extracted (visible) food
lipids.

Fatty Acids

Building blocks of triacylglycerols, have an even number of carbon atoms (4 to 24).

Trivial Names

Common names indicating original sources of fatty acids.

Butyric acid

A major component of butter flavor.

Caproic, caprylic, and capric acids

Called the "goaty acids"

because they impart characteristic flavors to goat and sheep

milk and cheese.

Oleic and stearic acids

The terms olein and stearin were
applied to the liquid and solid fractions, respectively, of tallow
separated by pressing during early margarine manufacturing.

Shorthand Notation

Specifies carbon atoms and double bonds in fatty acids.

IUPAC Names

Systematic naming based on carbon count and bonds.

Geometric Configuration

Cis and trans configurations affect physical properties.

Cis Configuration

Hydrogens on the same side, causing a bend.

Trans Configuration

Hydrogens on opposite sides, straighter chain.

acylglycerols (glycerides)

Esters formed from glycerol and fatty acids.

Monoacylglycerols (MAGs)

Glycerol esterified with one fatty acid, more polar.

Diacylglycerols (DAGs)

Glycerol esterified with two fatty acids, emulsifiers.

Triacylglycerols (TAGs)

TAGs are the main
form of stored energy in animals and plants and are the
predominant component of dietary fats.

Naming Conventions

naming of acylglycerols can vary based on the types of fatty acids
attached to the glycerol molecule.

Stereospecific Numbering (sn) System

Indicates position of fatty acids on glycerol.

Polarity

Increases as fatty acid number decreases.

Emulsification

Stabilizes mixtures of oil and water.

Nutritional Aspects

Triacylglycerols provide 9 kcal/g, aid vitamin absorption.

Melting Points

Depend on fatty acid composition and structure.

Saturated Fatty Acids

Higher melting points than unsaturated of same length.

Increasing Chain Length

Increasing length raises melting point of fatty acids.

Double Bonds

Presence and position significantly impact melting points.

Tristearin

Saturated triacylglycerol with high melting point.

Triolein

Unsaturated triacylglycerol with low melting point.

Polymorphism

Ability to exist in multiple crystalline forms.

Fats and oils can crystallize into several polymorphic forms,
primarily classified into 3 main types:

1. Alpha (α) Crystals
2. Beta Prime (β') Crystals
3. Beta (β) Crystals

Alpha Crystals

Least stable crystals with smallest size.

Beta Prime Crystals

More stable than alpha; larger size.

Beta Crystals

Most stable form; largest crystal size.

Factors Influencing Polymorphism

1. Cooling Rate
2. Fatty Acid Composition
3. Processing Conditions
4. Additives

Cooling Rate

Affects crystal formation; rapid favors alpha.

Fatty Acid Composition

Type of fatty acids influences crystallization.

Processing Conditions

Mechanical processes alter crystallization behavior.

Additives

Substances modifying crystallization and crystal types.

Importance of Polymorphism

Understanding polymorphism is essential for food scientists
and manufacturers because it affects texture and mouthfeel, shelf life and stability, and functional properties

Texture and Mouthfeel

Crystal structure influences food product texture.

Shelf Life and Stability

Different crystals impact stability and rancidity.

Functional Properties

Crystallization affects cooking and baking functionality.

Energy Content of Fats

Fats provide 9 kcal/g for energy intake.

Fat-Soluble Vitamins

Vitamins A, D, E, K require fats for absorption.

Essential Fatty Acids

Omega-3 and omega-6 cannot be synthesized by body.

Cell Membrane Structure

Dietary lipids maintain cell membrane integrity.

Health Implications

Unsaturated fats reduce cardiovascular disease risks.

Structure of waxes

consists of a long-chain fatty acid linked to a
long-chain alcohol through an ester bond.

Hydrophobicity

Waxes are largely insoluble in water.

High Melting Points

Long carbon chains lead to solid state.

Stability of Waxes

More resistant to oxidation than fats and oils.

Plants

Many plants secrete waxes on their surfaces
to reduce water loss. For example, the cuticle of
leaves is composed of cutin, a type of wax.

Animals

Beeswax is a well-known example of

animal-derived wax, produced by honeybees for

building honeycomb structures.

Microorganisms

Certain bacteria and fungi produce
waxes as part of their metabolic processes.

Sources of Waxes

Found in plants, animals, and microorganisms.

Terpenes

Organic compounds derived from isoprene units.

Monoterpenes

Composed of two isoprene units (C10).

Sesquiterpenes

Composed of three isoprene units (C15).

Diterpenes

Composed of four isoprene units (C20).

Carotenoids

Pigments responsible for red, orange, yellow colors.

Carotenes

Hydrocarbon carotenoids, precursors to vitamin A.

Fat-soluble vitamins

essential nutrients that dissolve in fats
and oils and are stored in the body's fatty tissues.

Primary fat-soluble vitamins

Vitamin A, D, E, K

Vitamin A

Important for vision, immune function, and skin
health. It is found in animal products (retinol) and as provitamin
A carotenoids in plant sources.

Vitamin D

Crucial for calcium absorption and bone health.

Vitamin E

An antioxidant that protects cell membranes from
oxidative damage. It is found in vegetable oils, nuts, and green
leafy vegetables.

Vitamin K

Essential for blood clotting and bone metabolism. It
is found in green leafy vegetables and fermented foods.

Steroids

A type of lipid characterized by a core structure consisting of four rings with various functional groups attached.

Key types of steroids

1. Cholesterol
2. Steroid Hormones
3. Bile Acids

Xanthophylls

Oxygen-containing carotenoids important for eye health.

Cholesterol

Component of membranes; precursor for steroid hormones.

Steroid Hormones

Regulate metabolism, immune response, reproductive functions.

Bile Acids

Essential for digestion and absorption of fats.

Global Vegetable Oil Production

Over 50% enters international trade.

Soybeans

Largest source of visible fats and oils.

Visible Fat Consumption

60% from meat and dairy; 40% from oils.

Vegetable Fats

Over 90% of visible fats by 1985.

Animal Fats

Fats derived from animal sources.

Oilseed

Seeds used for extracting oils.

Canola

Low erucic acid seed developed in Canada.

High-Oleic Acid Oils

Oils from sunflower and safflower seeds.

Flaxseed

Modified for reduced linolenic acid content.

Gossypol

Toxin reduced in glandless cottonseed.

Oil Palm Biotechnology

Investments by Palm Oil Research Institute.

Esterification

Process to modify fatty acids on glycerol.

Oilseed Extraction Capacity

Modern plants process 3,000-4,000 tons daily.

Seed Cleaning and Drying

Removes trash to prevent free fatty acids.

Seed Dehulling

Hull removal to reduce fiber in meals.

Seed Heating and Expansion

Heated to avoid maximum phospholipase activity.

Shallow Bed-Type Extractors

Percolate solvent through thin layer of flakes.

Deep Bed Extractors

Carousel design for oil extraction.

Screw Pressing

Pretreatment to make seed walls brittle.

Cold Pressing

Traditional method for extracting olive oil.

Centrifugation

Separates oil from solids using high speeds.

Solvent Extraction

Uses hexane for lower-grade oil extraction.