12 - Food Processing

Question 1

Which two sectors form the food industry?

Answer 1

Agriculture - provides fresh produce, minimally processed food or raw ingredients

Food production

Question 2

What is food processing?

Answer 2

The use of physical, chemical or biological means to convert raw food materials into consumable food products (ingredients or consumer products)

Question 3

What are the types of food processing methods?

Answer 3

Physical methods - size reduction and thermal treatments
Chemical methods - chemical preservatives
Biological methods - fermentation, enzyme treatment

Novel methods (physical) - high pressure, pulse electric field, irradiation

Question 4

What are the 3 main effects of food processing on food?

Answer 4

Microbial activity (extend shelf-life, but directly impact sensory quality and nutritive value of food)
Sensory quality (texture, smell, taste, appearance, can be desirable or not desirable)
Nutritive value (digestibility and availability of nutrients, can be desirable or not desirable)

Question 5

What are the desirable effects of food processing on nutritive value of food?

Answer 5

Improved nutritional quality of processed food - improved digestibility (moderately denatured proteins are more easily hydrolysed by digestive enzymes), bioavailability of nutrients (e.g., release of nutrients due to destruction of cell walls in plant materials)

Question 6

What are the undesirable effects of food processing on nutritive value of food?

Answer 6

Loss of certain nutrients, especially vitamin C and folate

Question 7

What are the physical methods of food processing?

Answer 7

Size reduction
Thermal treatments
- Mild heat - blanching, pasteurisation
- High heat - sterilisation, dehydration, baking and roasting, smoking
- Reduce temperature - chilling, freezing

Novel methods

• High pressure (non-thermal)
• Pulse electric field (non-thermal)
• Irradiation

Question 8

Physical food processes:

Size reduction affects which macro- and micro- nutrients?

Answer 8

All

All

Question 9

Physical food processes:

Blanching or pasteurisation affects which macro- and micro- nutrients?

Answer 9

None

Vit C and B complex

Question 10

Physical food processes:

Sterilisation affects which macro- and micro- nutrients?

Answer 10

All

Vit C and B complex

Question 11

Physical food processes:

Dehydration and baking, roasting affects which macro- and micro- nutrients?

Answer 11

Fats and proteins

Vit C and B complex

Question 12

Physical food processes:

Chilling, and freezing affects which macro- and micro- nutrients?

Answer 12

-

Vit C and B complex

Question 13

Thermal food processes:

What is the effect of freezing on microbial activity in food?

Answer 13

Cold

Decrease microbial growth

Reduce water activity

Question 14

Thermal food processes:

What is the effect of chilling on microbial activity in food?

Answer 14

Cold

Decrease microbial growth

Question 15

Thermal food processes:

What is the effect of pasteurisation or blanching on microbial activity in food?

Answer 15

Mild heat

Kills some microbes but require further processing e.g., chilling

Question 16

Thermal food processes:

What is the effect of sterilisation on microbial activity in food?

Answer 16

High heat

Kills all microbes

Question 17

Thermal food processes:

What is the effect of dehydration, baking, roasting, and smoking on microbial activity in food?

Answer 17

High heat + others

Kills all microbes

Reduce water activity

Question 18

Thermal food processes:

What is the effect of freezing and chilling on sensory quality in food?

Answer 18

No detectable changes

Question 19

Thermal food processes:

What is the effect of pasteurisation and blanching on sensory quality in food?

Answer 19

Slight or no detectable changes

Question 20

Thermal food processes:

What is the effect of sterilisation on sensory quality in food?

Answer 20

Large detectable changes, sometimes undesirable

Question 21

Thermal food processes:

What is the effect of dehydration, baking, roasting, and smoking on sensory quality in food?

Answer 21

Large detectable changes, desirable to create flavours

Question 22

Can a raw ingredient be converted to different products using different food processing methods (e.g., size reduction, thermal, biological)?

Answer 22

Yes

Furthermore, each type of food processing method - thermal or biological can produce more than 1 product from the same raw ingredient (e.g., thermal UHT milk, milk powder, pasteurised milk)

Question 23

What is the purpose of using food processing methods one after another?

Answer 23

To ensure food safety and product quality (e.g., homogenisation, pasteurisation, chilling)

Question 24

Novel food processes:
What is the effect of high hydrostatic pressure (HPP) on food?
Macro-nutrients
Micro-nutrients
Microbial activity
Sensory quality

Answer 24

Affects proteins

-

Reduces microbial activity with pressure

Retains most food quality and maintains natural freshness compared to other physical methods

Question 25

Novel food processes:
What is the effect of short pulses of a strong electric field (PEF) on food?
Macro-nutrients
Micro-nutrients
Microbial activity
Sensory quality

Answer 25

-

-

Reduces microbial activity with electricity

Minimal effect on sensory quality

Question 26

Novel food processes:
What is the effect of irradiation on food?
Macro-nutrients
Micro-nutrients
Microbial activity
Sensory quality

Answer 26

Affects fat and proteins

Affects vit B complex

Reduces microbial activity with irradiation

Minimal effect on sensory quality

Question 27

Are natural (unprocessed) foods safe, or safer than processed ones?

Answer 27

Some natural foods contain natural toxicants, and processing makes some natural food safer
(anti-nutritional factors, cyanogenic compounds, mycotoxins)

But some food processing methods generate toxicants too

Question 28

Process-generated toxicants:

What are the harmful effects of heterocyclic amines (HCA) and how are they generated?

Answer 28

Mutagens, carcinogens

Frying, grilling, roasting, BBQ of fish and meat

Question 29

Process-generated toxicants:

What are the harmful effects of trans fats and how are they generated?

Answer 29

Increased risk of coronary heart disease by increasing blood cholesterol levels

Fried foods and baked foods
Partially hydrogenated plant oils

Question 30

Process-generated toxicants:

What are the harmful effects of acrylamides and how are they generated?

Answer 30

Carcinogenic

Commonly found in fried, baked, roasted starchy foods
Temperature and time dependent

Mitigation - reducing cooking temp/time, no over-cooking, asparaginase (enzyme)