L23 - CA and MAP

Question 1

Respiration rate depends on

Answer 1

● the product type
● the storage temperature
● the processing

Question 2

Most important material properties for fresh product?

Answer 2

● Oxygen permeability (OTR)
● Carbon dioxide permeability (CTR)
● Water vapour transmission rate (WVTR)

Question 3

Diffusion depends on?

Answer 3

 Type of plastic
 Thickness
 Film area
 Temperature
 Pressure difference of the gases

Question 4

What are the main protective packaging technologies?

Answer 4

1. Modified Humidity Packaging:
   ● Control of moisture loss
2. Modified Atmosphere Packaging:
   ● Control of gas composition
3. Equilibrium Modified Atmosphere Packaging E-MAP
   ● Use product activity to reach optimal modified atmosphere
   ● Additionally protective against cutting discoloration

Question 5

Modified Humidity Packaging (MHP)

Answer 5

 Reduce the water loss to avoid loss of texture, but avoid fungal infection
 No free water
 antifog coating
 No effect on O2 and CO2 contents inside packaging headspace

Question 6

Modified Atmosphere Packaging (MAP)

Answer 6

 Pack the product directly at desired modified atmosphere
 Only suitable for “inactive” product: ready-to eat meals, meat, cheese
 Main goals:
● Prevent discoloration-Slow down spoilage/pathogen microbial growth

Question 7

Equilibrium-Modified Atmosphere Packaging (E-MAP)

Answer 7

 Suitable for product with respiration rate (fruit, vegetables, ornamentals)
 Use respiration rate of fresh product to create MAP
 Slow down activity of product -> extend self life
 BUT avoid fermentation

Question 8

Passive E-MAP packaging

Answer 8

 Start with atmospheric gas conditions

 Use product activity to reach equilibrium

Question 9

Active E-MAP packaging

Answer 9

 Flush with gas mixture during packing
● Faster slow down product activity
● Avoid abuse CO2content in packages once equilibrium reached

Question 10

How do acids in the packaging affect the product?

Answer 10

Adding acids to the bags destroys quality

Leuconostoc, Lactococcusand Lactobacillusbecome dominant species (due to the anaerobic environment).
These species are known to produce organic acids such as acetic acid (very volatile&raquo_space; smell) and lactic acid (much less volatile)

Question 11

How to achieve maximum shelf life?

Answer 11

 Control temperature in the chain (< 7°C)
 Use hurdles to control microbiological load and maintain sensorial quality parameters (washing and sorting processes…)
 Adapt packaging to vegetables requirements
 OTR, CTR and WVTR optimized to activity of produce
 Do not mix vegetables with different activities and gas requirements
 Reduce the length of the chain
 Better overview of initial quality

Question 12

CA (Controlled Atmosphere). What conditions?

Answer 12

• Ultra low fixed levels of O2 <1,5% (not too low, beware of fermentation)
• Lowest possible Temperature
• Fixed CO2 concentration

Question 13

What is achieved by CA?

Answer 13

Brings down:

• Respiration
• Moisture loss
• Ripening
• Microbial growth

Up to year round storage

Question 14

CA conditioning should be optimized for..

Answer 14

• Species of crop
• Cultivar
• T, % of O2 and CO2
• Harvest maturity/ripeness stage
• Growing conditions/climate

Question 15

CA storage, example of apples

Answer 15

• Start to remove field heat within 12h after harvest
• Prevent build-up of CO2
• Cool down until T set point, PRODUCT temperature
• Pulldown O2 level to 4-5% (usually within 1-2 weeks)
• Let product respiration lower O2 level and increase CO2 level to desired set-points.

Question 16

CA advantages

Answer 16

 Storage extension
 Retardation of senescence: softening, yellowing
 Better retention of health promoting compounds
 Reduction of both production and sensitivity to ethylene
 Inhibition fungal growth (>10 %CO2)
 Alleviation of physiological disorders: Chilling injury, Bitter pit, scald

Question 17

CA disadvantages

Answer 17

 Initiation of disorders
- Physiological: e.g. skin or flesh browning
- Microbial: mainly due to increased storage period
 Ripening issues
 Off-flavours (fermentation)

Question 18

How CA inhibits Chilling injury?

Answer 18

 CI is an induced oxidative response
 Low oxygen storage reduces oxidative stress by lowering ROS levels and by maintaining higher levels of antioxidants such as ascorbic acid

Question 19

Dynamic CA. What it means, what are the main effects

Answer 19

• Means to find the optimal (=lowest) oxygen level for a specific room/batch based on stress response signals from stored products
• O2 level is steadily lowered until fruit stress response from the fruits in store is detected
• Stress markers used:
  Ethanol
  Skin chlorophyll Fluorescence
  Respiratory Quotient

Main effects:

1. Optimal firmness and colour retention
2. Reduction of specific disorders