Food Microstructure Flashcards
What are the 8 structures of food?
Plant Cell Wall Meat Fibre Emulsions Particles Crystals Gels Foams And Mixtures of Above
What part of the plant do we eat?
We eat the fleshy tissue cell.
It is a source of dietary fibre and some sources even have starch.
What type of structure does the fleshy plant cells and their walls have?
They have an open cellular structure.
Whereas the walls have a lamella (sandwich) structure
What are the parts of a lamella plant cell wall?
A lamella cell wall has a plasma membrane, a lamella and a primary cell wall.
What is the plant cell walls made from?
Cellulose
Hemicellulose
Pectin
These three molecules are good examples of fibre to be introduced into the diet.
What is Cellulose?
It is a Biopolymer/macromolecule which is a polymer of D-glucose connected by Beta(1-4) linkages.
What is Hemicellulose?
It is a long change biopolymer containing different sugar monomers including Xylose, mannose, galactose rhamnose and arabinose.
This makes it way more complicated molecule than cellulose!
What are the two components of starch?
Amylose - D-Glucose alpha(1-4) glycosidic bonds
Amylopectin- D-Glucose but becomes branched due to alpha(1-6) glycosidic bonds
Where are the crystalline and amorphous regions on amylopectin?
The branching point (alpha 1-6 linkage) is the amorphous structure due to the chaos.
The crystalline structure occurs where the straight forks line up side by side (alpha 1-4 linkage).
What are the three levels of fractal muscle
1) muscle tissue is fascicles surrounded by epimysium
2) fascicles are muscle fibres surrounded by perimysium
3) muscle fibres are myofibrils surrounded by sarcolemmas
What is the connective tissue surrounding muscle fibres + fascicles made from?
Collagen and Elastin
Elastin is more for ligaments.
What type of structure does collagen have?
It has a fibrous fractal structure like meat.
What are the main amino acids of collagen?
Glycine, proline and hydroxyproline.
What are sarcomeres?
They are the units that make up myofribrils,
They consist of a thin part and a thick part.
The thin part is made from actin, troponin or topomyosin
The thick part is made from myosin
What are the structures of Actin, Troponin and Tropomyosin?
Actin is a family of globular multi-functional proteins
Tropomyosin is a two stranded alpha-helical coiled protein.
Troponin is a trimeric proetin composed of troponin subunits.
What is the thick myosin structure made from?
A super family of proteins, they have both filamentous and globular structures with the chain components being amino acids.
What is Pectin?
It is a polymer of D-galacturanic acid residues which are largely esterified by methoxy groups.
What are some reason for using structuring agents?
- Introduce texture
- Stabilise food structure
- Enhance shelf life
- To structure water or other liquids so that they don’t “move”
What are some common polysaccharide based food structuring agents?
- Plant and Plant cell wall based: Starch, cellulose
- Seed and Sap based: Guar Gum and Gum Arabica
- Seaweed based: Agar and carrageenan
- Bacterially produced: Xantham gum
What is the structural application of starch?
It is a secondary gelling agent, it also works as a stabiliser and a thickener.
What sources do we get starch from? what are the benefits for using it?
We get starch from wheat, potato, rice, corn and tapioca. We use it because it is very cost effective.
What sources do we get cellulose from?
Plant cell wall material
What are the structural applications of cellulose?
It can be used as a thickener, suspending aid(emulsions), lubricant and film former.
It also inhibits the production of ice crystals.
what are the sources of pectin?
The are derived from the cell wall of elevated plants and fruit, particularly orchard fruit. eg orange skin.
What are the structural applications of pectin? what two forms can it appear in?
Pectin can either be high methoxyl (highly esterified) or low methoxyl (Low esterification).
The high methoxyl pectin gels in the presence of high sugar
The low methoxyl gels within the presence of cations (Ca2+)
How is starch bonded?
Amylose is alpha D-Glucose (1-4) glycosidic linkages
Amylopectin is Alpha D-glucose (1-6) glycosidic linkages
How is cellulose bonded?
It is Beta D-Glucose (1-4) glycosidic linkages
How is Pectin bonded?
It is a linear polymer of partially esterified alpha -(1-4) Galacturonic acid and mannuronic acid
What are the structural applications of guar gum?
It is typically used as a gel or thickener for products such as pastries, yoghurt and sweet desserts.
What is the source of guar gum?
It is extracted from the endosperm guar plant.
What is the application of gum arabica?
It is used in things like hard candy and chewing gum.
What is the source of gum arabica?
It from the sap taken from acacia trees.
What is the application of locust bean gum.
It is used in gelling applications such as the production of ice cream,
What is the source of locust bean gum?
it is extracted from the seeds of the carob tree.
What is the structural application of agar?
It is a vegetarian gelatin substitute, but it is more brittle.
What is the source of agar?
it comes from red algae and seaweed.
What is the structural application of carrageenan?
It is a gelling agent that serves to immobilise cells. it gels with cations as they contain negatively charge sulfonyl groups.
What is the source of carrageenan?
Red seaweed.
What is the structural application of alginates?
They form jellies, they gel with cations, they are good for emulsification stabilisation, thickener.
Non-melting gel.
What is the source of alginates?
They come from brown seaweed.
What is the structural purpose of Xantham gum.
It stabilises colloidal oil and solid components against creaming by acting as a emulsifier.
low concentrations result in significant thickening effect.
What is the source of Xantham gum?
It is a bacterial polysaccharide formed by the fermentation of glucose or sucrose.
What are some common protein based food structuring agents?
Animal Derived: Gelatin, whey and egg proteins
Plant Derived: Soy protein and zein
What is the structural purpose of gelatin?
It is a gelling agent, or a foam stabiliser.
What is the source of gelatin?
It is sourced from the skin and bones of animals.
It is high in glycine, proline and hydroxyproline.
What is the structural purpose of whey?
Gelling agent and thickener.
What are the sources of whey?
acid or sweet dairy whey
What is the structural purpose of egg proteins? and what is the major protein of use?
Gelling and thickening agent for confectionery products
The major protein is Albumen (globular proteins)
What is the structural purpose of soya protein?
It is used as a heat set gel. that is sourced from soy beans.
What is a food colloid?
It is a mixture in which one substance is a microscopically dispersed particles suspended throughout another substance.
Where do we find food colloids?
There are many of these in food - they are called multiphase systems. These include emulsions, suspensions, gels, foams and crystals.
What are the two parts of a multi-phase food system.
The dispersed phase and the continuous phase, the continuous phase is the large medium in which the dispersed phase is subjected to.
What is a food particle suspension?
It is a dispersion of microscopic solid particles in a liquid.
What are some example of food particle suspensions?>
Milk: Casein suspended in milk
Fat crystals are suspended in oil
Juices contain solid cell particles
What are the three main important characteristics of the solid particles?
Particle size distribution
Volume fraction of the dispersed phase
Particle deformability.
What are the four main components required to make a suspension or paste?
- Particle
- Liquid
- Stabiliser
- Mechanical energy
What is the particle dispersion process?
Particle wetting
Separation
Stabilisation. (may need a dispersant)
What is flocculation and gelling?
It is when the particles is an suspension start sticking to themselves, when this occurs at a significant level gelling starts to occur. This happens when an emulsifier isn’t used.
What is suspension destabilisation?
It is when particles descend out of suspension and form a sediment - this occurs whether the suspension is flocculated or not.
In terms of suspension destabilisation what is the difference between a viscofying agent and a steric stabiliser?
A viscofying agent prevents sedimentation
A steric stabiliser prevents flocculation.
What are stabilisers?
Also known as surfactants
They create a barrier between particles one one of two ways
1. Electrostatic - repulsion
2. Steric - use long chain molecules to prevent intermolecular interactions.
What is suspension stability?
It is the resistance to change in the dispersed state.
The higher the energy barrier, the more stable the system.
What is an emulsions?
An emulsion is when both disperse phase and continuous phase are liquids.
What are the two common emulsions
Oil in water O/W or Water in Oil W/O
What are the four components of emulsions?
- Oil
- Water
3 Emulsifier - Mechanical Energy
What are some ways emulsions can become unstable?
Sedimentation
Inversion (O/W to W/O)
Ostwald Ripening (Change in diffusion sizes)
Flocculation
Creaming
All these lead to coalescence then phase separation
What are the two types of emulsifiers in food?
- Polymers
2. Small amphiphillic molecules.
What is a amphiphillic emulsifier
These emulsifiers have a lipophillic end and a hydrophillic end.
What is bancrofts rule?
Surfactants must be soluble in continuous phase
Why are proteins often chosen for emulsifiers?
Edible
Surface active
Water soluble
Coalescence resistant.
What is a pickering emulsions?
It is where the emulsifier is a solid particles that surround the droplet to prevent coalescence
What are crystals in food?
They are solids in which the atoms, ion or molecules are tightly packed in regularly ordered repeating patterns.
What are the two arrangements lipids take when forming crystals?
Chair arrangement
Tuning fork arrangement
What is the structure of a Gel?
It is a biopolymer/macromolecule network system which is formed and encapsulates fluid.
What are Gels typically made from?
Proteins or Polysaccharides
What are the two thermal gelation methods?
Cold-set Gelation: Macromolecules is dissolved in heated water, then cooled to gel.
Heat-set gelation: Macromolecule is dissolved in hot water and gels whilst hot.
What is Diffusion setting ionotropic gelation?
It is when negatively charged biopolymers are cross linked with cations, typically by direct mixing.
Product inhomogenous structure.
What is Internal ionotropic gelation?
It is when negatively charged biopolymers are cross linked with cations, however the cations do not instigate the formation of gel. After mixing, the pH is changed and the entire system is gelatinised by activating the cation.
What are foam food structures?
The are biopolymer/macromolecule network systems that enclose gas. Gas is dispersed, liquid network is continuous
What are the two methods of forming a foam?
Supersaturating - supersaturating the liquid with gas, either by dissolving gas under pressure and releasing pressure or by letting gas develop in situ.
Mechanical Means - injection or beating
What is the size hierarchy of food structures?
Atom/Element
What are the three types of microscopy?
Optical (light)
Electron
Scanning probe
