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level: Exam 1 Revision

Questions and Answers List

level questions: Exam 1 Revision

QuestionAnswer
Triacylglcerols (TAGs)Ester derived from glycerol and three fatty acids making of 90% of dietary fats
Differential Scanning CalorimetryUsed to show melting profiles of fats
CBECocoa butter equivalent. Plant-based fat, not dairy
SFCSolid fat content
HydrogenationAddition 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
LDLLow-density lipoprotien
HDLHigh-density lipoprotien
InterestificationDoes not change fatty acid composition of an oil. Instead, rearranges fatty acids on glycerol to create new TAGs
Polysaccharides (PS)Natural polymer formed of repeating sub units. Degree of polymerisation depends on molecular weight of chain
Water structuring polysaccharidesHydrogen bonding between water molecules and polymer backbone allows small amounts of polymer to structure large amounts of water
Hydrodynamic volumeVolume a polymer occupies in a solution, dontated as radius r_h
Amino Acidalpha (central) carbon atom linked to an amino group or carboxy group
Formula of amino group and carboxyl group-NH2 and -COOH
Gelatineprotein derived through hydrolysis from collagen taken from animal body parts. It is brittle when dry and rubbery when moist
Gelatine Solutionbehave as non-Newtonian fluids. Gels upon cooling roughly 25 degree Celsius, where the temperature range depends on source and cooling rate
Gelatine GelsMelt around body temperature into a Newtonian fluid, providing unique food textures mouthfeel and flavour release properties
Primary homogenous nucleationSmall 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 nucleationInduced by presence of a surface acting as nucleus. Reduced supercooling/supersaturation on conditions are requried
Secondary nucleationStarting 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 Theorymatter 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 powerobtained by rapid supercooling or rapid removal of solvent
Particle morphologyShape, size, surface morphology (e.g. surface roughness)
Water activityRatio 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 dryingBased on dehydration by sublimation of a frozen product
FreezingCan 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 dryingAfter 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 dryingCarried out at warmer temperatures to remove bound water. The drying rate is slower since moisture loss only occurs by diffusion
Spray dryingUsed 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
CycloneCentrifugal force causes particles to segregate from the air. Air flows out the top while particles are removed from the bottom
Textile or bag filterPowdered air passes through a fabric filter before being exhausted into the atmosphere. Fine particles are trapped by the filter
Stages of spray dryingInitial heating, constant-rate period, falling-rate period
Roller/ drum dryingLiquid 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 dryingthree step process combining spray drying and freeze drying. Methods; spray freeze into vapour or into vapour over liquid or into liquid
Convective freeze dryingcollected frozen droplets are transferred to pre-chilled shelves for subsequent drying
Atmospheric freeze dryingcold gas is used as water removal and heat transfer medium to cause sublimation at or near atmospheric pressure
Thermal ProcessingPasteurizing and sterilising foods to increase shelf life
D-valueDecimal reduction time. Heating time resulting in reducing microorganisms by a factor of 10, or one log factor
Z-valueThe increase in temperature necessary to cause a 90% reduction in the D-value. Describes the influence of temperature on the D-value
Thermal death timeMinimum time to accomplish a total destruction
Thermal resistance of microorganismsPlace 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
RetortHeat treatment device. Uses steam to heat product to kill microorganisms
Commercial sterilisationAttain a degree of sterility in product being processed so it does not undergo spoilage and become a health hazard
F-valueNumber of minutes required to destroy a given number of organisms at a given temperature
BlanchingQuickly heat up food in boiling liquid and then cool down
PasteurisationSterilising a product to make it safe to consume
HTSTHigh temperature short time method
LTLTLow temperature long time method
Sterile productNo viable microorganisms are present. Prime concern is sterilisation processes is inactivation of spores
Steam retortSteam condenses on container wall and latent heat of condensation transfers through container wall into product. This is unsteady-state
Amphiphilicboth hydrophilic and hydrophobic parts
EmulsionMixture 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
Continuous phaseLiquid
Dispersed phaseSmall droplets
BloomIf chocolate is stored at too high a temperature, surface may appear dull of white
HLBHydrophilic lipophilic balance. Predicts behaviour of emulsifiers related to their solubility. 1-20 scale. 1 = hydrophobic, 20 = hydrophilic
Bancroft ruleHydrophobic emulsifiers stabilise water-in-oil emulsions. Hydrophilic emulsifiers stabilise oil-in-water emulsions
Foam stabilisationPolymeric emulsifier tends to be better foam stabilisers than small molecular surfactants
Two building blocks of starchAmylose (straight chain polymer) and Amylopectin (branched chain polymer)
Scanning electron microscope (SEM)Can be used to observe starch granules
GelatinisationDescribes the disruption of molecular orderliness within the starch granule. Water into granule-granule swells - loss of some polymer
PastingSummarises continuing starch transformation at temperatures exceeding gelatinisation temperature
Osmotic dehydrationincrease 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
SaltingDraws 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 irradiationUses 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