Food Technology Flashcards
What is food technology?
The study of how different foods can be used snd made into food products from production to consumption
What is the aim of food technology?
To minimise growth of micro-organisms during storage
(promote longer shelf-life)
(reduce hazards from eating food)
Role of vet in food technology
Inspection of animal origin food establishments (Abattoirs)
Microbiological testing
Legislation
Intrinsic factors affecting microbial behaviour in foods
Nutrient content
Natural antimicrobial substances
pH and buffering capacity
O/R potential
Water activity
Mechanical barriers e.g. skin
Extrinsic factors affecting microbial behaviour in foods
Temperature
Relative humidity
Atmospheric gases
Time
How nutrient content affect microbial activity in food
Water is required for all microorganisms
*Higher requirement of water for moulds
Need a source of energy
* Sugars, alcohols, amino acids, starch, cellulose, fats
Source of nitrogen
* Amino acids
Natural antimicrobial substances in foods
Essential oils in some plant spp.
* Eugenol in cloves
* Allicin in garlic
Cows milk contains:
* Lactoferrin
* Conglutinin
* Lactoperoxidase
Lysozyme in eggs and milk
pH change and buffering capacity
Most microorganisms grow around pH 7.0
Very few grow < 4.5
Buffered foods resist changes in pH
* Meats are more buffered than veg
Moulds and yeasts can grow at lowest pH
Redox Potential
Ease of which the substrate gains of loses e-
(OiL RiG)
Potential difference is expressed as mV
Aerobic organisms require oxidation (+ve Eh values)
Anaerobic organisms require reduction (-ve Eh values)
What determines O/R
Redox potential of original food
Poising capacity
Oxygen tension of atmosphere
Water activity
How efficiently water can take part in chemical reactions
Reducing available water can preserve food
Most pathogens stop growing at 0.9aw
Psychrotroph temperatures
Can grow <7
Optimum is 20-30
Psychrophile temperatures
Optimum < 15
Mesophile temperatures
Can grow 20-45
Optimum 30-40
Thermophile temperatures
Can grow >45
Optimum 55-65
What is the D value?
Decimal Reduction Time
Time for population to deplete by 90% at a specific temperature
E.g. D121 - Time required to kill 90% of population at 121 degrees
1D = ?
2D = ?
3D = ?
90% of original population
99% of original population
99.9% of original population
What is the Z value?
Temperature change required for D value to change by a factor of 10
What is the most important gas for microbial activity in food?
CO2
Ozone is also important - strong oxidising agent
How does ozone affect high lipid food?
Increases rancidity due to fat oxidisation
How doe relative humidity affect microbial behaviour?
High temp = Low RH
Low temp = High RH
Foods that undergo spoilage from moulds and yeasts should be stored in low RH
Reasons for rejecting food as spoiled
Organoleptic changes
Chemical changes
Physical damage
Freezer burn
Staling
Ripening foreign bodies
Chemical contamination - often cleaning chemicals
Organoleptic changes
Most common cause of spoilage
Acts on sensory organs
Causes unacceptable changes in:
Taste
Texture
Odour
Appearance
Yoghurt is a spoiled food that is safe to eat
Chemical changes
Rancidity from chemical oxidation of fats
Browning of fruits and veg in air
Meat rejected due to colour change
* Dark colour due to further oxidation from myoglobin to oxymyoglobin to metmyoglobin
Physical damage
Caused by improper handling of goods
could be related to biological risk
Freezer burn
Caused by poor wrapping during freezing
Leads to loss of moisture
Staling
Process by which bread reduces in palatability by loss of water
In what products does over ripening occur?
Fermented meats
Fruits and veg
Cheeses
