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Food processing exam Flashcards

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1
Q

describe what fermentation is

A

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

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2
Q

list factors affecting microbial growth in fermentation

A
  • Availability of nutrients
  • pH
  • temperature
  • water activity
  • anaerobic/aerobic conditions
  • population size
  • competing microorganisms
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3
Q

what are inoculation techniques

A

Natural/uncontrolled fermentation

Implants bacteria/microbes to stimulate fermentation

Not heated before fermentation

can be naturally occuring microbial flora

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4
Q

what is starter mediated fermentation

A

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

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5
Q

what are starter cultures

A

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

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6
Q

what is the difference between homofermenters and heterofermenters

A

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

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7
Q

list some different types of food fermentations

A
  • Organic acids
  • Alcohol
  • Alkaline
  • Fungal
  • Enzymatic
  • Liquid fermentations
  • Solid state fermentations
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8
Q

describe lactic acid fermentation

A

Anaerobic conditions

Produced from pyruvate

Microbial groups:
o Lactobacillus spp.
o Leuconostoc spp.
o Pediococcus spp.
o Streptococcus sp.

Used in: Sauerkraut, Kimchi, Lassi

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9
Q

what is alcoholic fermentation

A

Anaerobic conditions

Sugars to alcohol

Mono and disaccharides to ethanol and carbon dioxide

Principal fermentation of yeast

E.g. Sake, Beer, Bai-jiu

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10
Q

what is alkaline fermentation

A

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

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11
Q

what is fungal fermentation

A

Uses filamentous fungi

Enhances nutrition

Affects flavour

E.g. Tou-shi, Gochujang, Angkak red rice

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12
Q

what are some benefits of fermentation

A

Cost effective

Unique food and sensory characteristics

Increase food safety

Maintain or increase nutritional value (proteins hydrolysed into peptides)

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13
Q

what are some disadvantages of fermentation

A

using low quality ingredients

not following precise conditions (toxins could be produced e.g. histamine, methanol)

longer fermentation time required e.g. miso

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14
Q

what are the 4 different types of wheat grain

A

Soft

Mixed

Hard

Durum (highest 14% protein)

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15
Q

what are the 5 wheat processing stages

A

receive and storage

cleaning

tempering

milling

break purification reduction

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16
Q

describe the tempering stage in wheat processing

A

Water coat outer bran layer – easier separation

Endosperm softened

Types of wheat blended to make specific flours

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17
Q

describe the process of milling during wheat processing

A

Rollers break wheat into coarse particles

Grain opens up

Bran is removed

Grinds endosperm to flour

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18
Q

describe the process of break purification reduction during wheat processing

A

Flour sifted and purified – separation of particle size

Bleaching

Enriched with nutrients

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19
Q

describe the structure of a wheat grain

A

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

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20
Q

compare 2 different types of mills for wheat processing

A

Stone mills

Roller milling
 Principle machine
 Break reduction and sieving

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21
Q

describe the main features of pan bread

A

High Protein content – 11 – 12.5%

Hard wheat with high water absorption

Extensible dough

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22
Q

describe the features of a good noodle

A
  • 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
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23
Q

describe the features of good pasta

A
  • Durum wheat
  • 14% protein
  • Bright yellow
  • Clean
  • Uniform colour
  • Maintain shape when cooking
  • Non sticky surface
  • Cooking water free of starch
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24
Q

how is food quality monitored

A

o Physical – texture
o Chemical/nutritional
o Microbiological
o Sensory

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25
Q

what is texture

A

Physical attribute

Involves touch, sight, sound, kinaesthetic

Arises from food microstructure (bond interactions)

How surface feel is affected during eating

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26
Q

what is rheology

A

Study of deformation and flow of matter

Distance, time and mass

Deformation: materials that are solid

Flow: fluid like materials

Viscoelastic properties

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27
Q

what are the 5 factors that affect viscosity

A
  1. temperature
  2. solute concentration and size
  3. density
  4. molecular weight
  5. pressure
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28
Q

explain the difference between laminar and turbulent flow

A

Turbulent
* Fluid flow
* Viscosity varies in magnitude and direction
* Erratic
* E.g. milk pasteurisation

Laminar = even streamline flow

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29
Q

how can texture be measured

A

Force – puncture, crushing, snapping, etc.

Distance – length, area, volume

Time

Energy (force and distance)

30
Q

what are some instruments used to measure texture

A

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

31
Q

what are the 3 food texture classifications

A
  1. Critical e.g. potato chips, cornflakes
  2. Important e.g. fruits and veg, cheese, bread
  3. Minor – e.g. thin soups, beverages
32
Q

what is food colour

A

First quality evaluated by consumers

Relevant to purchasing decisions

Sensation transference

Lightness, hue and saturation

Humans see wavelength between 380 – 780nm

33
Q

what are the factors affecting food colour

A

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)

34
Q

what is gloss

A

Reflection of light at 45˚

Influenced by
- particle size
- Water content
- Crystal size

35
Q

what are the 3 types of sustainability in a sustainable food system

A
  1. Economic
  2. Social
  3. Environmental
36
Q

describe what a sustainable food system is

A

Resource efficiency – water/energy efficiency

Minimising environmental impact – reduce greenhouse gas

Ethical and social responsibility

Innovation in packaging

Circular economy – reuse/recycle

37
Q

what are some things that contribute toward consumer sustainability

A

o Authentic commitment
o Transparency
o Informed buying decisions
o Growing awareness of waste
o Animal welfare
o Worker welfare

38
Q

explain the role of water in food processing

A

Used in:
o Heating and cooling
o cleansing and sanitising
o Medium for transport
o ingredient

Agriculture accounts for 70% of freshwater withdrawals

39
Q

how does changing climate affect the livestock sector

A

Decreased food production and quality

Increased pests, weeds and diseases

Higher animal mortality rates

Less adaptable breeds

Money loss

40
Q

what are the dominant greenhouse gas emissions from the agriculture industry

A

o Methane – fermentation
o Nitrous oxide – N fertiliser
o CO2 – on farm fossil fuel use

LIVESTOCK contributes 18% anthropogenic emmissions

41
Q

what are 3 things climate smart agriculture needs to enable

A
  1. Sustainably increase productivity of livestock production
  2. Reduce GG emissions and environmental impact
  3. Enhance resilience and adaptability of farmers
42
Q

describe the composition of milk

A
  1. Milk solids

Fat
Milk solids: Lactose, Minerals, Proteins (casein, whey)

  1. Water
43
Q

list some tests used to evaluate milk quality

A

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

44
Q

what happens during the process of cream separation during milk processing

A

centrifuge separation

fat has lower density than milk plasma

fat subject to less centrifugal force

fat moves toward axis of rotation

45
Q

what are some factors affecting cream separation in milk processing

A

fat globule size

milk temp

flow rate (high flow - less separation)

magnitude of rotation

position of cream screw

46
Q

what is milk standardisation

A
  • Pearson square method
  • Calculates simple mass balance in mixtures
47
Q

what is the purpose of homogenisation in milk processing

A

Disrupts gat globules to smaller ones

Produces more stable emulsion

Prevents creaming during storage

Improve viscosity and mouthfeel

48
Q

explain the process of homogenisation during milk processing

A

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

49
Q

what is LTLT during the heat treatment/pasteurisation of milk

A

o 63˚
o 30 min
o Used for cheese

50
Q

what is HTST during the heat treatment/pasteurisation of milk

A

o 72˚
o 15 sec
o Kills pathogens but NOT all microorganisms
o Most common

51
Q

what is UHT during the heat treatment/pasteurisation of milk

A

o 130 – 145˚
o Few seconds
o Kills all microbes

52
Q

what are the 2 tests used to test the heat treatment of milk

A
  1. Phosphatase test
    * Phosphatase destroyed by heat (>72˚)
    * Positive result means milk not heated above 72˚
  2. Peroxidase test
    * Peroxidase destroyed at 85˚
    * Positive result = milk not heated >85˚
53
Q

what are some changes that happen to milk during heat treatment

A

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

54
Q

what is the purpose of packaging milk

A

Protects and preserves
o Recontamination
o Light
o flavour

Has consumer information

Convenience of handling

aseptic cartons for sterilised milk

55
Q

what are some changes that can occur to milk during storage

A
  • microbial growth
  • colour change (browning)
  • fat oxidation
  • lipolysis
  • protein oxidation
56
Q

what is the difference between condensed and evaporated milk

A

Condensed
* added cane sugar
* milk concentration done
* from full cream milk

Evaporated
* unsweetened
* milk concentration done
* from full cream milk

57
Q

describe the features of cultured milk products

A

prepared by inoculation with starter culture

part of lactose –> lactic acid

low pH

lactic acid acts as preservative

low pH reduced harmful microorganism growth

58
Q

what are the classifications of yoghurt

A
  • chemical (low fat)
  • physical (set, stirred)
  • flavour
  • other (fortified)
59
Q

what are some unique features of fruit and vegetables

A

Derive from ovary/embryo

High in water content

Low fat content

High in dietary fibre, vitamin C, b-carotene

Can contain cyanides (toxic)

60
Q

explain the difference between climacteric and non-climacteric fruits

A

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

61
Q

what are the 5 physiological changes that occur during the life cycle of a fruit/veg

A

germination

cell growth

maturation

ripening

senescence

62
Q

what occurs to a fruit during its ripening stage

A

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

63
Q

how is fruit quality assessed

A

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

64
Q

what are some factors affecting fruit quality during the PRE HARVEST stage

A
  • genotype
  • climate/glasshouse
  • cultural practices: pesticides, fertiliser, water
  • plant population
65
Q

what are some factors affecting quality during the POST HARVEST stage

A
  • Time of harvest (early morning/night)
  • Hand or machine
  • Maturity
  • Post harvest handling
66
Q

what are factors affecting the rate of respiration in fruits/vegetables

A

Highest respiration = rapidly growing
Low respiration = dormant

  1. Influences by temp, O2 availability and carbohydrates
  2. Age and condition of cells and tissues
67
Q

how can we minimise quality change in fruits/vegetables

A
  1. Control transportation e.g. misting fruits/veg
  2. Low humidity/high air temp e.g. storage climate. INCREASE HUMIDITY
  3. Air movement = increase
  4. Reduced size = increase water loss (e.g. cut fruit)
68
Q

How is the effects of O2, Co2, ethylene and water controlled for fruit and vegetables

A
  • Fruit wrapping
  • Packaging material
  • Air movement
  • Air pressure (low pressure = significant loss)
69
Q

how is citrus quality analysed

A

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

70
Q

What are the 3 values used in thermal inactivation

A

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.

71
Q

What is a lifecycle assessment

A
  • 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
72
Q

What are the 4main stages of a life cycle assessment

A
  1. Goal and scope: Establishing system boundaries
  2. 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
  3. 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
  4. interpretation

Food processing (2 decks)

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