Lipid Classification and Properties

• Lipids are classified by major and minor food lipid components, shorthand notations for structures, and the difference between saponifiable and unsaponifiable lipids

Solubility and Fractions

• Lipids are soluble in organic solvents but not in water.
• Lipids are categorized into saponifiable (97%) and unsaponifiable (3%) fractions.
• Saponifiable components possess an ester functional group that can be hydrolyzed with a base.

Saponifiable Fractions

• Mono, di, and triacylglycerols consist of esters of one, two, or three fatty acids and one glycerol.
• Waxes are esters of fatty acids and alcohols.
• Sterol esters are esters of fatty acids and sterols.
• Glycerophospholipids are esters of fatty acids, phosphoric acid, and glycerol.
• Glyceroglycolipids are esters of one or two fatty acids and glycerol, with one or more sugar units attached to the third position of the glycerol backbone via a glycosidic linkage.
• Saccharolipids are esters of fatty acids with a sugar backbone.
• Sphingolipids are esters of fatty acids and a long-chain base containing various components like phosphate and carbohydrate.

Unsaponifiable Fractions

• Free fatty acids and oxidation products include aldehydes and ketones
• Sterols include cholesterol
• Hydrocarbons include carotenoids and squalene.
• Fat-soluble vitamins include A, D, E, and K.

Fatty Acids (FA)

• Fatty acids are aliphatic carboxylic acids with 4 or more carbon atoms.
• FA are categorized by chain length: short (4-6C), medium (8-12C), and long chain (>14C).
• FA may be saturated, monounsaturated, or polyunsaturated.

Fatty Acid Nomenclature

• a-linolenic acid is a common name.
• 9,12,15-octadecatrienoic acid is a systematic name.
• The short-notation includes the number of carbons (e.g., C18:3), the number of double bonds, and the position of the first double bond from either the methyl (ω) or carboxy (Δ) group.

Fatty Acid Isomers

• Double bonds occur in cis or trans configurations.
• FA in nature occurs as cis-isomers.
• Industrial hydrogenation converts cis to trans isomers, increasing cardiovascular risk.
• Double bonds in polyunsaturated FA are separated by 3 carbons, forming a pentadiene structure.
• Linoleic acid and α-linoleic acid are essential FA obtained through diet.

Triacylglycerols (TAGs)

• TAGs consist of one glycerol esterified with 3 FAs.
• Simple TAGs contain 3 identical FAs, while mixed TAGs contain 2 or more different FAs.
• TAGs have 4 main isomeric forms.

TAG Isomers

• *sn-*positional isomers: contain same FAs but at different sn positions.
• Chain length isomers: contain the same amount of carbons but divided between different types of FAs.
• Double positional isomers: contain the same amount of double bonds but with at least one of them at a different position
• cis-trans conformational isomers: differ by the conformation of their double bond

Minor Lipid Components

• Mono- and diacylglycerols: glycerol backbones with 2 FAs, used as tracers or markers of lipolysis, also function as amphiphilic surfactants or emulsifiers.
• Phospholipids: glycerophosphate backbones with 2 FAs at the sn-1 and sn-2 positions, unsubstituted or substituted with ethanolamine, choline, serine, or inositol.
• Lecithin: a mixture of phospholipids derived from egg or soy, functions as an emulsifier because of its amphiphilic nature.
• Wax esters: FAs esterified with long-chain alcohols, mainly found in rape and corn oil, and causes a haze when stored at sub-ambient temperatures.

More Minor Lipid Components

• Sterols: are fat-soluble steroids, either animal-based (cholesterol) or plant-based (phytosterols.
• Hydrocarbons: tetraterpenoid compounds with antioxidant activity that provide yellow to red pigmentation, including alkanes, alkenes (carotenoids), and polycyclic aromatic hydrocarbons (PAHs).
• Fat-soluble vitamins: includes vitamins such as A (retinol), D (calciferol), K, and E (tocopherols and tocotrienols).

Tocopherols

• The most important natural antioxidants of phenolic nature
• Includes the forms: Tocopherols and Tocotrienols

Analysis of Lipid Composition

• Analysis important to determine nutritional value, stability, and techno-functionality.
• Most analysis requires extraction of lipids (e.g., Folch, Soxhlet extraction).

Degree of Unsaturation

• Iodide Value (IV): grams of iodine reacted with 100g of lipid, iodine reacts with C-C double bonds.
• Followed by solution of potassium iodide to reduce iodine , then a titration indicate by blue to colourless reduction
• The higher IV means a higher degree of unsaturation.

Fatty Acid Composition by GC

• FAs are converted to volatile fatty acid methyl esters (FAMEs) through transesterification.
• FAMEs are dissolved in organic solvent and injected into the GC coupled with flame ionization detector (FID) or mass spectrometer (MS).
• Retention time (r) of FAMEs in the GC depends on chain length, number, and position and configuration of double bonds.
• Shorter chains move faster, more unsaturated FAs have a longer rt, lower ω leads to longer rt and trans fatty acids elute faster than cis.

RP-LC for TAG and Phospholipid Analysis

• Reversed-phase liquid chromatography (RP-LC) can be coupled to evaporative light-scattering detector (ELSD), charged aerosol detector (CAD), or MS.
• Combining RP-LC with MS separates TAG positional isomers.

Lipid Oxidation Measurement

• Titration and spectrophotometric methods measure the degree of oxidation.
• LC-MS and nuclear magnetic resonance are examples of more advanced methods.

Physical Lipid Characteristics

• Food lipids are divided into fats (solid/semi-solid at room temperature) and oils (liquid at room temperature).

steps of Nucleation and Crystal Growth

• Supercooling material after it is melted, defined by desired crystallization temp
• Nucleation forms, by generation of nuclei, together towards crystal lattice
• Crystal growth, where stable nuclei form to grow

Nucleation type

• Primary homogenous in absence of imputities/fat crystals
• Primary heterogenous in presence of foreign surface
• Secondary heterogenous in presence fo crystals being crystallized

Polymorphism

• Polymorphism of fats refers to the arrangement of fats
• 3 most common polymorphisms observed in TAGSs

Polymorphism types

• Hexagonical subcell packing
• Orthorhombic - perpendicular packing
• Triclinic-parallel cell packing

Impact of Polymorphism

• arrangements can lead to different physical properties
• Higher temperature and longer crystallization times promote denser and more ordered packing, increasing crystal density.

Effect of TAG Composition on Crystallization

• Saturated FAs have higher melting point than unsaturated FA.
• Longer chain FAs have higher melting point than shorter chain FA.
• Double bond position and configuration (cis/trans) can influence crystallization.
• TAGs with similar FA chains tend to form more stable crystals.

Solid Fat Content (SFC)

• Corresponds to solid mass fraction (%) at a certain temperature.
• Tm of a sample is the temperature at which SFC reaches 0.
• SFC is measured with low-resolution pNMR by tracking energy release of solid and liquid fat molecules.

Differential Scanning Calorimetry (DSC)

• Used to assess crystallization and melting behaviors of fats and oils.
• DSC has chambers (sample and reference) for comparison.

DSC Findings

• Melting is endothermic; crystallization is exothermic.
• Broad peaks suggest blends of TAGs; narrow peaks suggest purity.
• Onset T : T deviate from baseline
• Offset T: T returns to baseline

Lipid Oxidation overview

• Three main reactions can occur: autoxidation, photooxidation and enzymatic oxidation
• Focus is on autoxidation

Autoxidation Reactions

• Initation begins with abstraction of H atom creating ALkyl Lipid Radical
• Propagation- Alkyl radical reacts with oxygen to form peroxyl radical.
• LOO acts a lipid oxidizer and creates new alkyl radical
• LOOH is formed via hydroperoxiding/decomposes
• Termination, with combination of 2 radical forming a non-radical

Alternative reaction outcomes

• Formation of epoxides that contribute to oxidation
• Cyclization of peroxyl radical into epidioxides
• Addition of alkoxyl radical LO that produces the formation of alkoxyl radical

Sources of Oils and Fats

• Vegetable oil: soybean and palm, canola (rapeseed) sunflowers
• Animal fats: milk, lard, tallow, and fatty fish
• Extracted from seeds(seed oils)or surrounding fruity flesh(pupil oils)

Pulp vs Seed extraction

• Oil is present in droplet or oil bodies for both
• Differ in low-high H2O
• size and coating of oil bodies

Methods for extracting oil for seed

• Cleaning, removal of impurities
• Dehulling removal of hulls
• Conditioning to bring seeding to optimum conditions
• Flaking reduction to obtain flakes to maximise oil liberation

Pressing

• Removal of oil by application of increasing pressure
• Pre is low, with residual oil
• Direct is high leading to low residual oil
• Cold pressing used with high virgin olive oil

Solvent Extraction

• Oil extracted by mass transfer through organic solvent
• Solvents are highly oil-soluble
• During, oil bodies form micella with solvent
• Distallation of micella to remove solvent
• Desolventization agitation to remove solvent

Pulp oil Extraction

• Sterilization, stripping, and digesting oil in palm
• Cruding, drying and separate nuts via pneumatic column

Olive oil extraction

• Removal and crushing of water through aid of temp and time
• Extraction via phase separation via decanters generating lost of AOs

Animal Fat/Marine Oil Extraction

• Animal fats is extracted through a process that disintegrates raw materials to release the oil through mechanical processing
• Heat used to melt fat
• Wet and Dry rendering
• Dry rendering is considerably less effluent

Removal of fats and oils

• Removal of non-TAGs, with preservativing TAGS, Antioxidants and Vits
• Physical vs Chem removal

Degumming

• Aim:removal of phospholipds insoluble in oil
• Leads to oil discolouration
• Emulisifying property can interact with refining processes
• H2O degumming removes hydratable
• Acid removes non-hydratable

Neutralisation

• Removal of Free fatty acids due to acidity
• Addition of alkali
• Creates soaps that should be removed

Dewaxing

• aim is removale of waxes
• done by siw cooling and filtration

Bleaching

• Removal of colour pigment
• Addition of adsorbent
• Rxn under vaccup pressure
• Removal of adsorbent

Deodorizaiton

• Removal of volitile compounds/residual acids
• Process through deaeration and heating
• Stripping with inert gas
• Cooling
• Components removed-fatty acids, sterols, tocopherols, pesticides, hydrocarbons, carotenoids

Hydrogenation

• Aim:reduce degree of unsaturation to improve oxidative stability/modify physical state
• H2 helps with catalyst rxns
• Insufficient hydrogen can creat positional isomers and catalyst before completion, it can remain in cis or convert to trans
• Sufficient creates Saturation
• Selevtivity targets ceratin double bone in hydrogen
• High selectivity helps minimize unwanted side effetcs while maximization increase temp, preesuerm catalyst and nixign
• Speead helps hrdrogention at expense of low selectivity

Interesterification

• Redistribute FAs on glycerol backbone of TAG
• Chemical reactions need sodium methoxide
• Leads homogeneous composition of TAG

Fractionation

• Separate fats to factions
• Separates higher melting faction stearin
• and Melting Liquid Olein
• Dry fractionation
  • Melt the fat completly
  • stir slowly to encourage temprature
  • Pros helps aid processing
• Solvent used organic matter Pro reduced viscocity con; Cost and use of solvents

Blending

• Combination of fractionation, hydrogenation and interesterification
• Process helps with liquidity
• the agitation should be effective with no dragin to air Significant time for homogenisation