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Food processing exam Flashcards

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
what is texture
Physical attribute Involves touch, sight, sound, kinaesthetic Arises from food microstructure (bond interactions) How surface feel is affected during eating
26
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
27
what are the 5 factors that affect viscosity
1. temperature 2. solute concentration and size 3. density 4. molecular weight 5. pressure
28
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
29
how can texture be measured
Force – puncture, crushing, snapping, etc. Distance – length, area, volume Time Energy (force and distance)
30
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
31
what are the 3 food texture classifications
1. Critical e.g. potato chips, cornflakes 2. Important e.g. fruits and veg, cheese, bread 3. Minor – e.g. thin soups, beverages
32
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
33
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)
34
what is gloss
Reflection of light at 45˚ Influenced by - particle size - Water content - Crystal size
35
what are the 3 types of sustainability in a sustainable food system
1. Economic 2. Social 3. Environmental
36
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
37
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
38
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
39
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
40
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
41
what are 3 things climate smart agriculture needs to enable
1. Sustainably increase productivity of livestock production 2. Reduce GG emissions and environmental impact 3. Enhance resilience and adaptability of farmers
42
describe the composition of milk
1. Milk solids Fat Milk solids: Lactose, Minerals, Proteins (casein, whey) 2. Water
43
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
44
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
45
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
46
what is milk standardisation
* Pearson square method * Calculates simple mass balance in mixtures
47
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
48
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
49
what is LTLT during the heat treatment/pasteurisation of milk
o 63˚ o 30 min o Used for cheese
50
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
51
what is UHT during the heat treatment/pasteurisation of milk
o 130 – 145˚ o Few seconds o Kills all microbes
52
what are the 2 tests used to test the heat treatment of milk
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
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
54
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
55
what are some changes that can occur to milk during storage
* microbial growth * colour change (browning) * fat oxidation * lipolysis * protein oxidation
56
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
57
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
58
what are the classifications of yoghurt
* chemical (low fat) * physical (set, stirred) * flavour * other (fortified)
59
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)
60
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
61
what are the 5 physiological changes that occur during the life cycle of a fruit/veg
germination cell growth maturation ripening senescence
62
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
63
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
64
what are some factors affecting fruit quality during the PRE HARVEST stage
* genotype * climate/glasshouse * cultural practices: pesticides, fertiliser, water * plant population
65
what are some factors affecting quality during the POST HARVEST stage
* Time of harvest (early morning/night) * Hand or machine * Maturity * Post harvest handling
66
what are factors affecting the rate of respiration in fruits/vegetables
Highest respiration = rapidly growing Low respiration = dormant 1. Influences by temp, O2 availability and carbohydrates 2. Age and condition of cells and tissues
67
how can we minimise quality change in fruits/vegetables
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
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)
69
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
70
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.
71
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
72
What are the 4main stages of a life cycle assessment
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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