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Food Engineering


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Sam Oxley


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[Front]


Triacylglcerols (TAGs)
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Ester derived from glycerol and three fatty acids making of 90% of dietary fats

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Food Engineering - Marcador

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Food Engineering - Detalles

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Triacylglcerols (TAGs)
Ester derived from glycerol and three fatty acids making of 90% of dietary fats
Food irradiation
Uses x-rays, gamma irradiation sources and electron beams. Gamma irradiation does not increase temperature. Can be carried out on packaged food, fresh food, frozen foods and in the absence of chemical additives. Uses radiation to kill germs. Shorter the wavelength, higher the penetrating power. Dose is important. Can maintain food properties
Differential Scanning Calorimetry
Used to show melting profiles of fats
NA
NA
CBE
Cocoa butter equivalent. Plant-based fat, not dairy
Food irradiation
Uses x-rays, gamma irradiation sources and electron beams. Gamma irradiation does not increase temperature. Can be carried out on packaged food, fresh food, frozen foods and in the absence of chemical additives. Uses radiation to kill germs. Shorter the wavelength, higher the penetrating power. Dose is important. Can maintain food properties
SFC
Solid fat content
Food irradiation
Uses x-rays, gamma irradiation sources and electron beams. Gamma irradiation does not increase temperature. Can be carried out on packaged food, fresh food, frozen foods and in the absence of chemical additives. Uses radiation to kill germs. Shorter the wavelength, higher the penetrating power. Dose is important. Can maintain food properties
Hydrogenation
Addition of hydrogen, forms desired product by eliminating double bonds in TAGs. Also, forms undesirable products forming a trans molecule which has some health issues. This process is easy to control
Food irradiation
Uses x-rays, gamma irradiation sources and electron beams. Gamma irradiation does not increase temperature. Can be carried out on packaged food, fresh food, frozen foods and in the absence of chemical additives. Uses radiation to kill germs. Shorter the wavelength, higher the penetrating power. Dose is important. Can maintain food properties
LDL
Low-density lipoprotien
Food irradiation
Uses x-rays, gamma irradiation sources and electron beams. Gamma irradiation does not increase temperature. Can be carried out on packaged food, fresh food, frozen foods and in the absence of chemical additives. Uses radiation to kill germs. Shorter the wavelength, higher the penetrating power. Dose is important. Can maintain food properties
HDL
High-density lipoprotien
Food irradiation
Uses x-rays, gamma irradiation sources and electron beams. Gamma irradiation does not increase temperature. Can be carried out on packaged food, fresh food, frozen foods and in the absence of chemical additives. Uses radiation to kill germs. Shorter the wavelength, higher the penetrating power. Dose is important. Can maintain food properties
Interestification
Does not change fatty acid composition of an oil. Instead, rearranges fatty acids on glycerol to create new TAGs
Food irradiation
Uses x-rays, gamma irradiation sources and electron beams. Gamma irradiation does not increase temperature. Can be carried out on packaged food, fresh food, frozen foods and in the absence of chemical additives. Uses radiation to kill germs. Shorter the wavelength, higher the penetrating power. Dose is important. Can maintain food properties
Polysaccharides (PS)
Natural polymer formed of repeating sub units. Degree of polymerisation depends on molecular weight of chain
Food irradiation
Uses x-rays, gamma irradiation sources and electron beams. Gamma irradiation does not increase temperature. Can be carried out on packaged food, fresh food, frozen foods and in the absence of chemical additives. Uses radiation to kill germs. Shorter the wavelength, higher the penetrating power. Dose is important. Can maintain food properties
Water structuring polysaccharides
Hydrogen bonding between water molecules and polymer backbone allows small amounts of polymer to structure large amounts of water
Food irradiation
Uses x-rays, gamma irradiation sources and electron beams. Gamma irradiation does not increase temperature. Can be carried out on packaged food, fresh food, frozen foods and in the absence of chemical additives. Uses radiation to kill germs. Shorter the wavelength, higher the penetrating power. Dose is important. Can maintain food properties
Hydrodynamic volume
Volume a polymer occupies in a solution, dontated as radius r_h
Food irradiation
Uses x-rays, gamma irradiation sources and electron beams. Gamma irradiation does not increase temperature. Can be carried out on packaged food, fresh food, frozen foods and in the absence of chemical additives. Uses radiation to kill germs. Shorter the wavelength, higher the penetrating power. Dose is important. Can maintain food properties
Amino Acid
Alpha (central) carbon atom linked to an amino group or carboxy group
Food irradiation
Uses x-rays, gamma irradiation sources and electron beams. Gamma irradiation does not increase temperature. Can be carried out on packaged food, fresh food, frozen foods and in the absence of chemical additives. Uses radiation to kill germs. Shorter the wavelength, higher the penetrating power. Dose is important. Can maintain food properties
Food irradiation
Uses x-rays, gamma irradiation sources and electron beams. Gamma irradiation does not increase temperature. Can be carried out on packaged food, fresh food, frozen foods and in the absence of chemical additives. Uses radiation to kill germs. Shorter the wavelength, higher the penetrating power. Dose is important. Can maintain food properties
Gelatine
Protein derived through hydrolysis from collagen taken from animal body parts. It is brittle when dry and rubbery when moist
Food irradiation
Uses x-rays, gamma irradiation sources and electron beams. Gamma irradiation does not increase temperature. Can be carried out on packaged food, fresh food, frozen foods and in the absence of chemical additives. Uses radiation to kill germs. Shorter the wavelength, higher the penetrating power. Dose is important. Can maintain food properties
Gelatine Solution
Behave as non-Newtonian fluids. Gels upon cooling roughly 25 degree Celsius, where the temperature range depends on source and cooling rate
Gelatine Gels
Melt around body temperature into a Newtonian fluid, providing unique food textures mouthfeel and flavour release properties
Primary homogenous nucleation
Small cluster of water molecules from the basis of crystal-initiating nuclei. Rate of nucleation increases with degree of supercooling, though precautions need to be taken
Secondary heterogenous nucleation
Induced by presence of a surface acting as nucleus. Reduced supercooling/supersaturation on conditions are requried
Secondary nucleation
Starting nuclei are seeds, greater than critical ones, thus stable and thermodynamically favoured to grow. Seeds come from the breakage of bigger crystals or are added to the system intentionally. Seeds can be added to promote crystallisation
Diffusion Theory
Matter is deposited continuously on a crystal face at a rate proportional to the difference in concentration between point of deposition and the bulk of solution
Amorphous power
Obtained by rapid supercooling or rapid removal of solvent
Particle morphology
Shape, size, surface morphology (e.g. surface roughness)
Water activity
Ratio between vapour pressure of water at food surface (P) and vapour pressure of pure water at same temperature (P*). Quantity of water available for chemical and biological reactions, thus an indication of food stability
Freeze drying
Based on dehydration by sublimation of a frozen product
Freezing
Can take place using an outside freezer or directly in freeze dryer chamber by decreasing the shelf temperatures. Slow freezing = formulation of large ice crystals, though rapid freezing promotes intensive nucleation and formation of small ice crystals
Primary drying
After ice crystals form, rapid sublimation is accomplished by controlling the vacuum level in the freeze dryer and through careful heat input. Heat is supplied by conduction and radiation. Ice starts sublimating in the frozen product from the surfaces in contact with the heating source, leaving a porous dry cake. Water vapour is removed by mass transfer through the dried product. Primary drying only decreases moisture content to a certain value
Secondary drying
Carried out at warmer temperatures to remove bound water. The drying rate is slower since moisture loss only occurs by diffusion
Spray drying
Used for preparation of dry stable additives, instant food powders, functional ingredients and flavours. Uses a spray drying chamber and a cyclone. Can be operated co-current, counter-current or a mixture. Heat and mass transfer induced by the movement of air in the chamber. High pressure nozzles centrifugal atomizers are used. Rapid drying due to small size of liquid droplets. Residence time is 5-100 seconds
Cyclone
Centrifugal force causes particles to segregate from the air. Air flows out the top while particles are removed from the bottom
Textile or bag filter
Powdered air passes through a fabric filter before being exhausted into the atmosphere. Fine particles are trapped by the filter
Stages of spray drying
Initial heating, constant-rate period, falling-rate period
Roller/ drum drying
Liquid is applied in a thin layer and maintained as a thin film of rotating steam heated drum. Dried film is scrapped off after 3/4 complete rotations of the drum surface. Used for small volumes. Number of drums may vary, along with operating pressure, type of feed and construction material
Spray freeze drying
Three step process combining spray drying and freeze drying. Methods; spray freeze into vapour or into vapour over liquid or into liquid
Convective freeze drying
Collected frozen droplets are transferred to pre-chilled shelves for subsequent drying
Atmospheric freeze drying
Cold gas is used as water removal and heat transfer medium to cause sublimation at or near atmospheric pressure
Thermal Processing
Pasteurizing and sterilising foods to increase shelf life
D-value
Decimal reduction time. Heating time resulting in reducing microorganisms by a factor of 10, or one log factor
Z-value
The increase in temperature necessary to cause a 90% reduction in the D-value. Describes the influence of temperature on the D-value
Thermal death time
Minimum time to accomplish a total destruction
Thermal resistance of microorganisms
Place an inoculated suspension in a container and subjecting it to heat treatment . Instantaneous heating/cooling. Heat treatment is based off most resistant microorganisms that causes a health hazard or spillage
Retort
Heat treatment device. Uses steam to heat product to kill microorganisms
Commercial sterilisation
Attain a degree of sterility in product being processed so it does not undergo spoilage and become a health hazard
F-value
Number of minutes required to destroy a given number of organisms at a given temperature
Blanching
Quickly heat up food in boiling liquid and then cool down
Pasteurisation
Sterilising a product to make it safe to consume
HTST
High temperature short time method
LTLT
Low temperature long time method
Sterile product
No viable microorganisms are present. Prime concern is sterilisation processes is inactivation of spores
Steam retort
Steam condenses on container wall and latent heat of condensation transfers through container wall into product. This is unsteady-state
Amphiphilic
Both hydrophilic and hydrophobic parts
Emulsion
Mixture of one liquid with another which it cannot normally combine smoothly. A fine dispersion of minute droplets of one liquid in another in which it is not soluble or miscible
Dispersed phase
Small droplets
Bloom
If chocolate is stored at too high a temperature, surface may appear dull of white
HLB
Hydrophilic lipophilic balance. Predicts behaviour of emulsifiers related to their solubility. 1-20 scale. 1 = hydrophobic, 20 = hydrophilic
Bancroft rule
Hydrophobic emulsifiers stabilise water-in-oil emulsions. Hydrophilic emulsifiers stabilise oil-in-water emulsions
Foam stabilisation
Polymeric emulsifier tends to be better foam stabilisers than small molecular surfactants
Two building blocks of starch
Amylose (straight chain polymer) and Amylopectin (branched chain polymer)
Scanning electron microscope (SEM)
Can be used to observe starch granules
Gelatinisation
Describes the disruption of molecular orderliness within the starch granule. Water into granule-granule swells - loss of some polymer
Pasting
Summarises continuing starch transformation at temperatures exceeding gelatinisation temperature
Osmotic dehydration
Increase the shelf life of fruit and vegetables. Removal of water from lower concentration or higher concentration through a semi-permeable membrane. Greater temp. increases rate. Not on a molecular level
Salting
Draws water out of food, preventing bacteria growing and spoiling food. Reduces water activity. Impacts food properties. Salt plays an important role in cheese texture and stickiness of bread dough
Food irradiation
Uses x-rays, gamma irradiation sources and electron beams. Gamma irradiation does not increase temperature. Can be carried out on packaged food, fresh food, frozen foods and in the absence of chemical additives. Uses radiation to kill germs. Shorter the wavelength, higher the penetrating power. Dose is important. Can maintain food properties
What is the process for manufacturing expanded extruded snacks
Raw ingredient -> Extrusion -> Die cut -> Drying -> Oil & Flavouring -> Packaging
How does the extrusion process work
Raw material -> add water -> heat mixture -> hydrate, shear and cook -> pushed out at high pressure -> steam expands product -> product becomes glass -> extrudate is then cut with rotating blade
What parameters can be controlled for an extruder
Screw (speed, shape and dimensions), temperature, screw fill (more full means a higher shear and higher starch damage) and water & ingredients
What are the three different screw configurations
Single, twin (tangential) and twin (intermeshing). Single screw is normally cheaper
Define specific mechanical energy (SME)
How much energy we put into the extruder
What are the four types of parameters that can be changed in an extruder
Process, system, structure (reactions of different ingredients i.e. gelatinisation of starch etc) and product
What can be used instead of steam in the process and why is it better
Carbon dioxide, and used at lower temperature giving different textures
What is the main processing differences between pellet extruded snacks and direct extruded snacks
Usually lower temperatures and pressure forming a sheet to be cut and dried. Shear also tends to be lower
What is the process for manufacturing pellet extruded snacks
Raw ingredient -> extrusion -> shear and cut -> drying -> frying -> flavouring -> packing After drying, normally takes place at another location
What is the manufacturing process for potato starch
Potatoes from farm -> dry cleaning -> rotary wet cleaning -> mechanical rasping -> centrifuge sieve -> fibre sieve -> hydro cyclones -> vacuum dryer -> flash dryer -> packaging. CONDENSED PROCESS: clean -> break up -> remove cell debris -> remove water
What is the process for gelatinisation of starch
Raw starch -> heating -> swelling -> rupturing -> gelatinisation/pasting -> imploding
Define pasting
Second stage swelling occurs when starch is heated above gelatinisation temperature to obtain max viscosity. More amylose is leached out and eventually gels
Define glass
Hard and relatively brittle
What are steps 1-6 for direct and pellet extrusion
DIRECT: 1) raw ingredient 2) mix with water and heat 3) glass -> rubber then gelatinisation and melting 4) exit extruder and water nucleation 5) rapid expansion and boil off water 6) dry product PELLET: 1) raw ingredient 2) extrusion heating and gelatinisation 3) drying pellet becoming glassy 4) heating and expansion 5) pellet leaves fryer and cools down 6) solid glass brittle structure
What are some imaging techniques for potato starch
Scanning electron microscope (SEM), x-ray tomography and stained microscopy. Smaller cell walls = harder product
What are some overall plant considerations
Keep well maintained, flour and improver needs to be matched, optimise recipe, mix size, set the divider/final mould/panner and regular maintenance
What is the Chorleywood 'Bread' Process (CBP)
Method in which the majority of wrapped, sliced industrial loaves are made in Britain