Food Technology Flashcards
define food technology
Food technology is the study of how different foods can be used and made into food products from production to consumption
Define health
Our optimum physical an mental function
Give 5 criteria that food must fulfill
Safe to eat Good taste Easy to use well packed Good price
Describe Food Chain Management
Involves the management of all activities involved in the production, transformation, storage, distribution and the holistic farm to table approach.
What is the main purpose of food preservation?
The main aim of food preservation is to minimize the growth of microorganisms during the storage period, thus promoting longer shelf life and reduced hazard from eating the food.
Describe food processing
Food processing is the set of methods or techniques used to transform raw materials into food.
Give four intrinsic factors that control in microbial action on food
The nutrient content of food
The pH change and its ability to resist pH change (buffering capacity)
The oxidation reduction potential (Eh) of the food and its ability to resist redox change (poising capacity)
The water activity of the food (αw)
What 5 factors do microorganisms require to grow and function normally in food?
Water (higher requirement for moulds) Source of energy (sugars, alcohols and amino acids) Source of nitrogen (e.g. amino acids) Vitamins Minerals
Describe three natural antimicrobials
Essential oils in some plant species e.g. eugenol in cloves and allicin in garlic
Cows milk (lactoferrin etc)
Lysozyme in eggs and also milk
Describe the buffering of food
Meat buffered better than vegetables due to high protein content
Describe Eh in relation to food
The O/R potential of a substrate may be defined generally as the ease with which the substrate loses or gains electrons:
Looses electrons – Oxidised.
Gains electrons – Reduced.
Aerobic microorganisms require positive Eh values (oxidized) for growth, whereas anaerobes require negative Eh values (reduced).
What determines O/R
The characteristic O/R potential of the original food.
The poising capacity; that is, the resistance to change in potential of the food.
The oxygen tension of the atmosphere around the food.
The access that the atmosphere has to the food.
Microorganisms affect the Eh of their environments during growth just as they do pH.
Define water activity
Water activity is a measure of how efficiently the water present can take part in a chemical (physical) reaction.
How is water activity involved in microbial growth?
Reducing the amount of water available for microbial growth is an extremely important and very ancient way of preserving foods
Give four extrinsic factors involved in microbial growth
Temperature.
Gaseous atmosphere surrounding the food.
Relative humidity of the atmosphere surrounding the food.
Time.
Describe D value
D value (decimal reduction time) is the time taken for the population to pass through a log cycle (90% of the population is killed) at a certain temperature.
D121 – the time requires to kill 90% of a population of microorganisms at 121ºC.
Describe the scale of thermal processing with D Values
Thermal processing of 1D causes a 90% reduction of the original population.
Thermal processing of 2D causes a 99% reduction of the original population.
Thermal processing of 3D causes a 99.9% reduction of the original population.
Thermal processing of 4D causes a 99.99% reduction of the original population.
How do you work out a the number of spores left after heat treatment using D values?
Treatment Time/D value = x log cycles
10(pow of)original colony -x = no. of spores remaining
Define Z value
The Z value is the temperature change that is required to change the D value by a factor of 10.
What is MAP in relation to food preservation?
Modified Atmosphere Packaging - uses CO2 to control microorganism growth
Define spoiled food
A spoiled food is simply a food that is unacceptable to a consumer for reasons of smell, taste, appearance, texture or the presence of foreign bodies.
What is an organoleptic change
Organoleptic changes brought about by the growth of microorganisms is by far the most important and common source of food spoilage.
(include yeast in yogurt - safe to eat)
Describe a chemical change in food spoilage
Chemical oxidation of fats producing rancidity (oxidative rancidity).
Browning of fruits and vegetables in contact with air.
Describe why meat is rejected as spoiled due to colour change
Meat is rejected as spoiled due to colour change:
Oxygenation of myoglobin (Mb) and formation of oxymyoglobin (MbO2) - dark red
Oxidation of myoglobin and formation of MetMb (metmyoglobin) - brown
Describe freezer burn
A frozen food is loosing moisture due to poor packaging/wrapping:
The molecules migrate from the steak to the coldest place they can find, which is often the side of the freezer. The loss of these water molecules causes the food (i.e. steak) to become dehydrated.
Describe staling and how it could be avoided/made to take longer
A chemical and physical process in bread and other foods that reduces their palatability: Loss of water. - Reduced By - Check recipe. Increase water level. Reduce resting time. Increase baking temperature. Reduce baking time.
What is added to fermented sausages and why?
- Nitrite and/or nitrate
(Suppresses natural Gram- flora
Promotes the growth of streptococci, micrococci)
Sugar content
Only 0.1% glucose as fermentable carbohydrate in raw meat
-Lactic acid also decreases the water binding capacity of the meat protein. (Assists the drying process)
What controls the rate of fermentation in fermented sausages?
The speed of the fermentation depends on the level of carbohydrate used.
Low level of carbohydrates give slow rate of fermentation.
Name three commonly used organisms as starter cultures for fermented sausages
Lactobacillus plantarum.
Pediococcus acidilacti.
Yeasts can also be used
(micrococcus - if nitrate and not nitrite)
Why is nitrite essential in fermented sausages?
To prevent decolourization of the meat.
To prevent oxidative rancidity
Describe ripening of fermented sausages
Protein is hydrolysed by microbial proteinases to give amino acids and other breakdown products
What creates the stability and safety of fermented sausages
Low pH - Lactic acid
Reduced water activity - addition of salt and drying
What is the minimum heat process required for canning meat?
The minimum heat process applied to low acid canned foods is a process that gives a 12 decimal reductions of C. botulinium.
At 121 oC D value is 0.21 minutes (12 x 0.21 = 2.52 minutes).
Give four reasons for spoilage of canned foods
Underfilling.
Quality of the can seam.
Improper handling.
Hygiene of the can transport system.
Describe how smoking can be used to reduce
microorganism growth in food
Wood smoke contains a number of substances that have antimicrobial activity.
Formaldehyde and higher aldehydes, phenols and methanol.
Highly inhibitory to miroorganisms.
Describe the biochemical process that produces yoghurt
Yoghurt is a product of bacterial fermentation of milk
Lactose is converted by the bacteria into lactic acid.
Name two factors that will affect yoghurt production
Milk for yogurt production needs to be free from antibiotic residues
The culture will not multiply in the presence of antibiotics, the pH will not drop and the yoghurt will not set
Yogurt will also not set if the culture is destroyed by bacteriophages
Describe three microbial problems with cheese
Blowing (Early due to coliforms. Late due to gas producing Clostridia) - production of gas producing cracks and holes
Mould growth.
Bacteriophages attacking starter.
Describe the four stages of risk assessment
Hazard identification
Hazard characterization
Exposure assessment
Risk characterization
Describe the microbial criteria (important in purchase agreements)
A statement of the microorganisms and/or their toxins of concern to the food.
The methods to be used for their detection and/or enumeration.
A sampling plan.
The microbiological limits to be used in assessing the results
Guidance for interpreting the results.
Number of sample units that should conform to the limits.
Describe a sampling plan
A sampling plan is a statement of the criteria of acceptance applied to a lot based on appropriate examinations of a required number of sample units by specified methods
Describe a two class sampling plan
For presence/absence tests
n = number of sample units that must be tested per lot
c = maximum acceptable number hat can exceed the microbiological critrion
m= maximum number of relevant bacteria per gram
Describe a three class sampling plan
For count and concentration plan
n = number of sample units that must be tested per lot
c = maximum acceptable number hat can exceed the microbiological critrion
m= maximum number of relevant bacteria per gram
M = quantity used to separate marginally acceptable quality from unacceptable quality
Which regulation covers the microbiological criteria for foods
EC 2073/2005
Describe a shelf life evaluation
A variety of parameters are used to determine the shelf life of a product:
Deterioration in specific organoleptic qualities (flavour, aroma, appearance, texture).
Microbial growth (bacterial pathogens, bacterial indicator organisms and spoilage organisms.
Shelf life evaluation of perishable chilled products usually involves storage of finished products at ‘specified’ and at abuse temperatures.
Describe challenge testing
During challenge testing varying levels of the organism in concern e.g. Listeria monocytogenes, are inoculated into pack of the food under consideration.
Food is then stored together with un-inoculated control pack, under controlled temperature and conditions.
Examination at various intervals to determine:
Growth
Death or
Survival
