Food processing exam Flashcards
describe what fermentation is
Old technology of food preservation
Anaerobic metabolism and generation of energy
E.g. wine, vinegar, beer, mead
Mainly lactic acid bacteria, yeasts, molds
Needs adequately large number of metabolically active microorganisms:
o Anaerobic and aerobic conditions
o Production of acids or alcohol
o Enzyme activity
list factors affecting microbial growth in fermentation
- Availability of nutrients
- pH
- temperature
- water activity
- anaerobic/aerobic conditions
- population size
- competing microorganisms
what are inoculation techniques
Natural/uncontrolled fermentation
Implants bacteria/microbes to stimulate fermentation
Not heated before fermentation
can be naturally occuring microbial flora
what is starter mediated fermentation
Uses desirable starter cultures e.g.
o Natural enrichments
o Traditional multi/mixed strain starters
o Single strain starter
o Multiple strain starter (e.g. yoghurt)
Can isolate, purify, maintain microbial culture of importance
Sterilisation/pasteurisation may be applied
what are starter cultures
Used to inoculate raw materials –> fermentation
Need to propagate microorganisms
maintenance of identity, purity and molecular age
used to aid transportation form and packaging materials
what is the difference between homofermenters and heterofermenters
Homofermenters produce single main byproduct e.g. Lactococcus lactis lactic acid
Heterofermenters produce a mix of different byproducts lactobacillus spp. ethanol, ethanoic acid, lactic acid, CO2
list some different types of food fermentations
- Organic acids
- Alcohol
- Alkaline
- Fungal
- Enzymatic
- Liquid fermentations
- Solid state fermentations
describe lactic acid fermentation
Anaerobic conditions
Produced from pyruvate
Microbial groups:
o Lactobacillus spp.
o Leuconostoc spp.
o Pediococcus spp.
o Streptococcus sp.
Used in: Sauerkraut, Kimchi, Lassi
what is alcoholic fermentation
Anaerobic conditions
Sugars to alcohol
Mono and disaccharides to ethanol and carbon dioxide
Principal fermentation of yeast
E.g. Sake, Beer, Bai-jiu
what is alkaline fermentation
Increased pH during fermentation
Decrease organic acid as ammonia increases
Usually legumous seeds e..g soya bean
Groups used
o Aspergillus
o Bacillus
E.g. Natto, Kinema, Iru
what is fungal fermentation
Uses filamentous fungi
Enhances nutrition
Affects flavour
E.g. Tou-shi, Gochujang, Angkak red rice
what are some benefits of fermentation
Cost effective
Unique food and sensory characteristics
Increase food safety
Maintain or increase nutritional value (proteins hydrolysed into peptides)
what are some disadvantages of fermentation
using low quality ingredients
not following precise conditions (toxins could be produced e.g. histamine, methanol)
longer fermentation time required e.g. miso
what are the 4 different types of wheat grain
Soft
Mixed
Hard
Durum (highest 14% protein)
what are the 5 wheat processing stages
receive and storage
cleaning
tempering
milling
break purification reduction
describe the tempering stage in wheat processing
Water coat outer bran layer – easier separation
Endosperm softened
Types of wheat blended to make specific flours
describe the process of milling during wheat processing
Rollers break wheat into coarse particles
Grain opens up
Bran is removed
Grinds endosperm to flour
describe the process of break purification reduction during wheat processing
Flour sifted and purified – separation of particle size
Bleaching
Enriched with nutrients
describe the structure of a wheat grain
Bran: protection, dietary fibre and mineral rich.
Aleurone: thiamine, niacin and folate
Scutellum: stored food for embryo. Thiamine and phosphorus
Germ: unsaturated fatty acids and vitamin e. sucrose and raffinose
Endosperm:
o Cells packed with starch granules embed in protein matrix
o Protein and minerals decrease toward centre
compare 2 different types of mills for wheat processing
Stone mills
Roller milling
Principle machine
Break reduction and sieving
describe the main features of pan bread
High Protein content – 11 – 12.5%
Hard wheat with high water absorption
Extensible dough
describe the features of a good noodle
- soft wheat flour
- 10.5% wheat protein
- High swelling starch
- Low pasting viscosity
- Low ash content
- Dry crumbly dough
- Resting, sheeting, cutting
- Springiness and elastic
- Soft
- Creamy white colour
describe the features of good pasta
- Durum wheat
- 14% protein
- Bright yellow
- Clean
- Uniform colour
- Maintain shape when cooking
- Non sticky surface
- Cooking water free of starch
how is food quality monitored
o Physical – texture
o Chemical/nutritional
o Microbiological
o Sensory
what is texture
Physical attribute
Involves touch, sight, sound, kinaesthetic
Arises from food microstructure (bond interactions)
How surface feel is affected during eating
what is rheology
Study of deformation and flow of matter
Distance, time and mass
Deformation: materials that are solid
Flow: fluid like materials
Viscoelastic properties
what are the 5 factors that affect viscosity
- temperature
- solute concentration and size
- density
- molecular weight
- pressure
explain the difference between laminar and turbulent flow
Turbulent
* Fluid flow
* Viscosity varies in magnitude and direction
* Erratic
* E.g. milk pasteurisation
Laminar = even streamline flow
how can texture be measured
Force – puncture, crushing, snapping, etc.
Distance – length, area, volume
Time
Energy (force and distance)
what are some instruments used to measure texture
Warner Bratzler shear press: measures force
Hand held penetrometers: forces required to puncture
Bench penetrometer: distance through food e.e.g cheese slice
Bostwick consistometer
Brookfield viscometer
what are the 3 food texture classifications
- Critical e.g. potato chips, cornflakes
- Important e.g. fruits and veg, cheese, bread
- Minor – e.g. thin soups, beverages
what is food colour
First quality evaluated by consumers
Relevant to purchasing decisions
Sensation transference
Lightness, hue and saturation
Humans see wavelength between 380 – 780nm
what are the factors affecting food colour
Light source
o White light is dispersed by a prism into visible wavelengths
Reflectance of light
o Specular reflection (45˚ reflection gives gloss)
o Diffuse reflection (gives colour)
what is gloss
Reflection of light at 45˚
Influenced by
- particle size
- Water content
- Crystal size
what are the 3 types of sustainability in a sustainable food system
- Economic
- Social
- Environmental
describe what a sustainable food system is
Resource efficiency – water/energy efficiency
Minimising environmental impact – reduce greenhouse gas
Ethical and social responsibility
Innovation in packaging
Circular economy – reuse/recycle
what are some things that contribute toward consumer sustainability
o Authentic commitment
o Transparency
o Informed buying decisions
o Growing awareness of waste
o Animal welfare
o Worker welfare
explain the role of water in food processing
Used in:
o Heating and cooling
o cleansing and sanitising
o Medium for transport
o ingredient
Agriculture accounts for 70% of freshwater withdrawals
how does changing climate affect the livestock sector
Decreased food production and quality
Increased pests, weeds and diseases
Higher animal mortality rates
Less adaptable breeds
Money loss
what are the dominant greenhouse gas emissions from the agriculture industry
o Methane – fermentation
o Nitrous oxide – N fertiliser
o CO2 – on farm fossil fuel use
LIVESTOCK contributes 18% anthropogenic emmissions
what are 3 things climate smart agriculture needs to enable
- Sustainably increase productivity of livestock production
- Reduce GG emissions and environmental impact
- Enhance resilience and adaptability of farmers
describe the composition of milk
- Milk solids
Fat
Milk solids: Lactose, Minerals, Proteins (casein, whey)
- Water
list some tests used to evaluate milk quality
Temperature
pH
acidity
freezing point
alcohol test (addition of alcohol shouldn’t cause precipitate. Test protein quality to withstand UHT)
fat/protein/lactose content (fat determines milk price)
clot on boiling test
antibiotics
taste/smell/colour
what happens during the process of cream separation during milk processing
centrifuge separation
fat has lower density than milk plasma
fat subject to less centrifugal force
fat moves toward axis of rotation
what are some factors affecting cream separation in milk processing
fat globule size
milk temp
flow rate (high flow - less separation)
magnitude of rotation
position of cream screw
what is milk standardisation
- Pearson square method
- Calculates simple mass balance in mixtures
what is the purpose of homogenisation in milk processing
Disrupts gat globules to smaller ones
Produces more stable emulsion
Prevents creaming during storage
Improve viscosity and mouthfeel
explain the process of homogenisation during milk processing
High pressure pump (100 – 700 bar)
Liquid pumped through small gap - Physically breaks down droplet size
High pressure produces high liquid viscosity
Powerful shearing forces produced
Fat droplets in dispersed phase disrupted
Cavitation (air bubbles collapse) and impact reduce globule size
what is LTLT during the heat treatment/pasteurisation of milk
o 63˚
o 30 min
o Used for cheese
what is HTST during the heat treatment/pasteurisation of milk
o 72˚
o 15 sec
o Kills pathogens but NOT all microorganisms
o Most common
what is UHT during the heat treatment/pasteurisation of milk
o 130 – 145˚
o Few seconds
o Kills all microbes
what are the 2 tests used to test the heat treatment of milk
- Phosphatase test
* Phosphatase destroyed by heat (>72˚)
* Positive result means milk not heated above 72˚ - Peroxidase test
* Peroxidase destroyed at 85˚
* Positive result = milk not heated >85˚
what are some changes that happen to milk during heat treatment
Protein denaturation – whey at 65˚
Whey proteins form complex with casein proteins
Reduction in microbial count
Maillard and caramelisation browning
Loss of vitamins and amino acids
Enzyme inactivation
Flavour development
what is the purpose of packaging milk
Protects and preserves
o Recontamination
o Light
o flavour
Has consumer information
Convenience of handling
aseptic cartons for sterilised milk
what are some changes that can occur to milk during storage
- microbial growth
- colour change (browning)
- fat oxidation
- lipolysis
- protein oxidation
what is the difference between condensed and evaporated milk
Condensed
* added cane sugar
* milk concentration done
* from full cream milk
Evaporated
* unsweetened
* milk concentration done
* from full cream milk
describe the features of cultured milk products
prepared by inoculation with starter culture
part of lactose –> lactic acid
low pH
lactic acid acts as preservative
low pH reduced harmful microorganism growth
what are the classifications of yoghurt
- chemical (low fat)
- physical (set, stirred)
- flavour
- other (fortified)
what are some unique features of fruit and vegetables
Derive from ovary/embryo
High in water content
Low fat content
High in dietary fibre, vitamin C, b-carotene
Can contain cyanides (toxic)
explain the difference between climacteric and non-climacteric fruits
Climacteric and non climacteric differentiated by response to ethylene (ripening hormone)
ethylene triggers response on climacteric fruit (e.g. apple, banana, kiwi, guava)
Non climacteric = citrus, berries, grapes
Climacteric fruits show pronounces rise in respiration during ripening
Climacteric can be harvested when not fully mature
Non climacteric exhibit most of ripening changes, but occurs slowly
All vegetables are non-climacteric
what are the 5 physiological changes that occur during the life cycle of a fruit/veg
germination
cell growth
maturation
ripening
senescence
what occurs to a fruit during its ripening stage
Colour change
Respiration change for climacteric fruit (increase)
Change in ethylene production = abscission (loosening of fruit)
Increase permeability
Increase enzyme production (causes softness)
Change in carbohydrate composition (starch convert to sugars)
Produce flavour volatiles
Wax on skin
how is fruit quality assessed
Respiration (faster = more change). Control temperature
Weight loss (control transportation)
Firmness (control water loss and enzyme action)
total soluble solids – sugars (measured by refractometer)
titratable acidity
bioactive compounds
what are some factors affecting fruit quality during the PRE HARVEST stage
- genotype
- climate/glasshouse
- cultural practices: pesticides, fertiliser, water
- plant population
what are some factors affecting quality during the POST HARVEST stage
- Time of harvest (early morning/night)
- Hand or machine
- Maturity
- Post harvest handling
what are factors affecting the rate of respiration in fruits/vegetables
Highest respiration = rapidly growing
Low respiration = dormant
- Influences by temp, O2 availability and carbohydrates
- Age and condition of cells and tissues
how can we minimise quality change in fruits/vegetables
- Control transportation e.g. misting fruits/veg
- Low humidity/high air temp e.g. storage climate. INCREASE HUMIDITY
- Air movement = increase
- Reduced size = increase water loss (e.g. cut fruit)
How is the effects of O2, Co2, ethylene and water controlled for fruit and vegetables
- Fruit wrapping
- Packaging material
- Air movement
- Air pressure (low pressure = significant loss)
how is citrus quality analysed
Brix acid ratio
* Ratio of soluble sugars to acid
* Indicates ripeness – more ripeness = more sugar from starch breakdown, acid decreases
Total soluble solids
* Indicates sweetness
* Indicates ripeness – more ripeness = more sugar from starch breakdown
Minimum juice content
* Indicates ripeness – under OR over = less juice
What are the 3 values used in thermal inactivation
F value – number of minutes required to kill a known population of microorganisms
D value – time in minutes required to destroy 90% of target microorganism. measures heat resistance of a microorganism.
Z value – temperature change required to change D value by factor of 10. Temperature sensitivity of microorganisms.
What is a lifecycle assessment
- Way to quantify carbon footprint
- Holistic environmental management tool
- Accounts for all input, outputs and processes contributing to production of a product
- Quantifies carbon footprint across all stages of production/processing
- Goal in livestock industry to focus on quantifying carbon footprint of a process and identify hotspots in lifecycle
What are the 4main stages of a life cycle assessment
- Goal and scope: Establishing system boundaries
- Life cycle inventory
- Amount of input and output for all processes required to produce the product
- Considers pre farm and on farm production of emissions - Impact assessment
2 stages:
o Calculation of total gases produced in each process using emission factors
o Conversion of GH gas emissions into CO2 equivalent using global warming potential values
o Produced the total environmental impact of producing a product - interpretation
