Food processing

Question 1

what are some of the goals of food processing in the food industry today?

Answer 1

Extend shelf life: inhibit microbial activity

Enhance eating and sensory quality

Change form of food

Enhance nutritional quality

Income generation

Innovative ways to produce consumer desired foods e.g. vegan foods

Question 2

what are the 3 food processing classifications

Answer 2

1. Minimally processed (fruit)
2. Processed (canning/pasteurisation)
3. Ultra-processed (cake)

Question 3

what is the purpose of sanitary and phytosanitary measures in the food industry

Answer 3

Safeguards heath of animals, plants and people

Question 4

what is codex allimentarius

Answer 4

code relating to food and nutrition

Enables harmonization of standards

Facilitate world trade

Assist developing countries

Improve safety of global food supply

Question 5

what is a trained panel in sensory evaluation

Answer 5

Undergone discriminatory and descriptive tests

Measure type and extent of differences

Achieve objective results

Question 6

list some different tests used in food sensory evaluation

Answer 6

Forced choice (must pick an answer)

Duo trio test: 1 reference product, 2 different. Select similar to reference.

Descriptive analysis: complete sensory profile with trained panellists. High reliability and precision.

Threshold testing: investigates individuals sensitivity/threshold

Affective testing: indicate preference by selecting/ranking

Paired comparison: 2 diff samples, which one has the most sensory quality

Question 7

what is the purpose of heat treating food

Answer 7

Increase safety – kill pathogen microorganisms

Extend shelf life, reduce spoilage

Transform raw food –> palatable

Inactivates enzymes (prevent aesthetic changes)

Question 8

what are 3 factors affecting heat transfer

Answer 8

 Composition of product
 Thickness and area
 temperature

Question 9

what is HSTS heating

Answer 9

 UHT milk
 Ultra high temperature
 Ultra heat treatment
 Not less than 132˚ 3 – 5 sec

Question 10

what is commercial sterilisation

Answer 10

Objective to destroy all viable microbial cells, spores and enzymes for safety and shelf life

Not for complete sterility

High temperature long time

Shelf life >6 months room temp

Ultra high temperature aseptic processes: heated to 120 – 150 for a few seconds, filled into sterilised container

Question 11

what are some factors affecting sterilisation time length

Answer 11

Microorganisms heat resistance

Microbial numbers/concentration

Heating conditions

pH (low pH = higher heat)

size and shape of container

physical state of food

Question 12

what is pasting in starch gelatinisation

Answer 12

amylose leeched into dispersed phase (due to lower molecular weight)

granules gradually loose integrity

disruption of granule

forms paste

possible formation of gel when cooled

Question 13

what are 5 different ways we can modify starch

Answer 13

bleaching/oxidation

acid hydrolysis

enzyme hydrolysis

substitution

cross linking

Question 14

what is acid hydrolysis in starch modification

Answer 14

starch chain length reduced due to partial hydrolysis

reduced paste viscosity during cooking

rigid gels form when cool

increased gel strength and clarity

Question 15

what is substitution in starch modification

Answer 15

hydrogen atoms on hydroxyl groups replaced by substitute groups

prevents re-alignment of linear starch molecules – forms a blocking group

lowers retrogradation and syneresis

–> starch esters
–>starch ethers

Question 16

what is bleaching in starch modification

Answer 16

oxidise hydroxyl groups to COOH and carbonyl groups

reduce microbial counts

whiten starch

good film forming and binding properties

Question 17

what is cross linking in starch modification

Answer 17

2 starch chains covalently bonded to a larger one

Increases stability and granule integrity

Minimises rupture during cooking process

High viscosity

Question 18

what is the purpose of non-thermal food processing

Answer 18

Preserves nutrients

E.g. freezing
o Slows enzymatic activity
o Prevents microbial growth
o Reactants immobilisation
o Reduce chemical reactions

Question 19

what are the 3 major freezing processes

Answer 19

primary nucleation

secondary nucleation

crystal growth

Question 20

what is primary nucleation process in freezing

Answer 20

Homogenous: chance, orientation, a combination of water molecules at supersaturation level occurs without presence of a foreign phase

Heterogenous: formation of the nucleus around suspended particles or at a cell wall

Question 21

what is secondary nucleation process in freezing

Answer 21

crystal growth introduced with contact with other existing crystals – ‘seeds’

Question 22

what is crystal growth process in freezing

Answer 22

Continuous attachment of water molecules in the seed

Small uniform ice crystals desirable

Question 23

what are some negative effects of freezing on food

Answer 23

Damaged cells from dehydration

Minimal pigment and flavour change

Can destabilise food emulsions

Can cause proteins to precipitate

Starch retrogradation if slow freezing

Question 24

what is recrystallisation in freezing

Answer 24

Physical change to ice crystals after freezing

Migratory recrystallisation:
o Increase size of crystals
o Decrease number of crystals
o Due to ‘heat shock’ (constant high and low heat exposure)
o E.g. icecream

Question 25

what is drip loss

Answer 25

the water not reabsorbed during thawing

Question 26

what is moisture migration

Answer 26

Movement through osmotic mechanism

Difference in water activity

Ice formation inside package

Contributes to drip loss when thawed

Affects nutrients, appearance, texture

Question 27

what is irradiation

Answer 27

Preserves food by using ionising radiation

Inactivated microorganisms

Damages genetic material in microorganisms

Changes cell membrane structure

Non thermal

Primary: physical effects

Secondary: chemical effects