Food processing

Question 1

At what AW does a) microbe growth and b) deterioration stop?

Answer 1

a) ≤ 0.65 (RH=65%)
b) ≤ 0.3

Question 2

4 factors affect heat/liquid transfer in food, and therefore the rate of drying:

Answer 2

Surface area (+)
Temperature (+)
Humidity (-)
Atmospheric pressure (-)

Question 3

3 phases of the drying curve

Answer 3

Lag phase - Fast; water lost from surface
Constant (fast) rate - Dry layer on outside forms– insulation barrier; solute conc. increases
Falling rate - Reaching a normal equilibrium in RH

Question 4

Nutritive changes due to drying

Answer 4

Vitamin C
Thiamine (B1)
Protein quality
» all decreased

Pre-hydration steps (e.g. cooking, blanching); high temp; slow drying

Question 5

Sensory changes due to drying

Answer 5

Colour – browning reactions (enzymatic* & non-enzymatic)
Flavour – loss of volatile compounds
Taste – mostly intensified
Texture – altered in rehydrated products
*inactivate enzymes 1st by pasteurising/blanching

Question 6

Safety changes due to drying

Answer 6

Improved (linked to preservation)
But good hygiene is needed

Sun-drying – slower process & can  risk of bacterial spoilage
> Use of smoke/salt as further preservative agents evolved

Question 7

What humidity control is needed in fridges to avoid mould growth?

Answer 7

80-90%

Question 8

Conduction

Answer 8

Transfer by contact & molecules vibrating against one another
Reduces with density (solids>liquids>gases)
Thermal conductivity depends on type of material

Question 9

Convection

Answer 9

Transfer by movement of a heated fluid
Natural vs. forced (uses fan)

Question 10

Radiation

Answer 10

Occurs through empty space or via electromagnetic energy
Energy absorbed at particular wavelengths (e.g. microwave cooking)

Question 11

3 types of Thermal preservation

Answer 11

Blanching and pasteurisation (mild)
Sterilisation (severe)

Question 12

Blanching

Answer 12

Inactivated endogenous enzymes to avoid spoilage, e.g. Polyphenol oxidase (PPO) catalyses browning in peeled apples/potatoes
Useful before canning/freezing
Applied to: fruits & veg | Temp-time: 95oC, 5 min

Question 13

Pasteurisation

Answer 13

Destruction of pathogenic bacteria to remove health hazard; 3 temp-time combinations:
-Low temp 63oC, 30 min
-High temp-short time (HTST) 75oC, 15s
-Ultra-high temperature (UHT) 150oC, 1-3s

Applied to: liquid foods e.g. milk, beer, juices, sauces, liquid egg, marinades, soups

Question 14

Sterilisation

Answer 14

Complete destruction of microorganisms – objective to eliminate C botulinum spores

Applied to: canned/bottled foods
Temp-time: 121oC, 15-30 min

Question 15

D-Value

Answer 15

decimal reduction time (time to reduce bacteria by 10-fold) at specified temp
12D process = food safety
D-value @ 63°C  2.5 min (12*2.5) = 30 min

Question 16

Z-Value

Answer 16

temp requires to increase the D-Value by 10-fold

Question 17

4 types of non-thermal processing

Answer 17

• Modified Atmosphere Packaging (MAP)
• High Pressure Processing (HPP)
• Food Irradiation
• Chemical Preservatives

Question 18

Modified Atmosphere Packaging (MAP)

Answer 18

Definition: a one-time change in the atmosphere within a food package or storage area in order to extend shelf life

Uses gas mixtures for food preservation
MAP vs CAP = one time vs continual attempts
(Controlled Atmosphere Packaging)

Extends product shelf-life (x2-5 fold @ 1°C storage)
Preserve SNSS characteristics
Improve food supply chain distribution (↓ losses at POS)
Improves manufacturing efficiency by enabling longer production runs (↓ # deliveries)

Question 19

Effect of gas composition

Answer 19

Normal air = 78% N2, 21% O2, 0.035% CO2)
>30% CO2 for meat, poultry & seafood
~10% CO2 for fruits & vegetables

CO2 is antimicrobial agent:
Alters cell membrane & nutrient uptake
Inhibits food enzymes
Denatures protein
Changes pH inside cells

N2 is a passive filler (avoids package collapse)

Question 20

Food irradiation

Answer 20

Kills all pathogens, e.g. Lysteria monocytogenes, E. coli,
Leaves no residues
Low cost (~ 1-pence) / lb of food
Endorsed by WHO, IFT and American Medical Association
Moderate or no loss of nutrients at < 3kGray

1 gray (Gy) = 1J/ per kg of food material
Low dose applications (up to 1 kGy)
Sprout inhibition, delay fruit ripening, destroy insects
Medium dose applications (1 – 10 kGy)
Kill spoilage microbes in meat
Kill pathogenic microbes in fresh and frozen meat

Question 21

High Pressure Processing

Answer 21

Food is subjected to very high pressures
(liquid/solid foods)
100-200 MPa

Kills pathogens

Colours and nutrients retained
Mild SNSS changes

Question 22

Additives definiton

Answer 22

GENERAL STANDARD FOR FOOD ADDITIVES CODEX STAN 192-1995

any substance not normally consumed as a food by itself and not normally used as a typical ingredient of the food – whether or not it has nutritive value*
intentional addition to food for a technological (including organoleptic) purpose

Question 23

Additives labelling requirements

Answer 23

Food additives REGULATION (EU) No. 1333/2008Food labelling REGULATION (EU) No. 1169/2011

Must be named in list of ingredients
(main) functional class and specific name or E number
e.g. ‘Preservative: Sodium Nitrite’ or ‘Preservative: E250’
Additives for same function in a food can be grouped together

No requirement to label some additives not considered an ingredient
Carry-over from an ingredient (e.g. preservatives in fruit puree > yoghurt)
Processing aids (e.g. ascorbic acid to prevent discolouration of fruit > pie making, but has no effect in fruit pie - cooked off)
Other substances used in the quantities strictly necessary as solvents or media for additives or flavouring

Question 24

Antimicrobials - Weak Acids

Answer 24

Mostly weak acids that “short circuit” membrane H+ gradient, e.g.
Poly(3-hydroxybutyrate (PHB)
Sorbic Acid, Benzoic acids
Propionic, acetic acid
Sulphite, sulphur dioxide

Question 25

Anitmicrobials - Oxidising Agents

Answer 25

Disrupt redox balance of cells:
Chlorine water
Hydrogen peroxide
Hypochlorite

Question 26

Antioxidants - Chain Breaking

Answer 26

Free radical quenching/stabilisation:
Butylated hydroxytoluene (BHT)
Butylated hydroxyanisole (BHA)
Vitamin E

Question 27

Antioxidants - secondary antioxidants

Answer 27

Metal chelators (EDTA, citric acid, vit C)
Oxygen scrubbers (glucose oxidase)

Question 28

Brink et al

Answer 28

1964 - Events leading up to the legislation of pasteurization of all milk sold in Ontario… story marks a milestone in Canadian public health… great opportunities

Question 29

Monteiro et al

Answer 29

2010 - A new classification of foods based on the extent and purpose of their processing (NOVA)

Question 30

Dwyer et al

Answer 30

2012 - Ongoing efforts/challenges at the nutrition–food science–public health interface… processed F&V make important contributions to diet/nutr intake… addresses misinformation

Question 31

Snowdon et al

Answer 31

2013 - To develop a dataset (Pacific Islands) on nutrient composition of processed foods sold & their sources… labelling difficulties & consumer interpretation challenge

Question 32

Weaver et al

Answer 32

ASN Statement: nutritional impacts of processed foods… processed foods are nutritionally important to American diets (food & nutr security)… new tech & more education

Question 33

Gibney

Answer 33

2019 - UPF: Definitions and Policy Issues…debate – improving diet pattern from food processing rather than nutr intake