W7, Postharvest pathogens and management, INCOMPLETE

Question 1

What is the difference between climacteric and non-climacteric fruit?

Answer 1

Climacteric:

• Produce lots of ethylene
• Respire quite a lot
• Have a respiration climax once they’re harvested
• Go off quickly unless controlled appropriately
• e.g. bananas, apples, avocados, tomatoes, peaches, etc.

Non-climacteric:

• Not too bothered when they get removed from the mother plant, they just slowly die.
• e.g. cherries, cucumbers, grapes, lemons, strawberries, etc

The main differences are the amount of respiration and ethylene production. Non-climacteric fruit don’t produce ethylene (or, at least, not anywhere near as much as climacteric fruit), nor do they have an increase in respiration during the ripening stage. Climacteric fruit have both, shown in the graph below.

Question 2

True or False?

Climacteric fruit should be separated from eachother when being transported or stored.

Answer 2

True.

The production of ethylene gas by climacteric fruit will hasten the ripening of other fruit nearby.

Question 3

True or False?

Most postharvest pathogens are biotrophs.

What does this mean for postharvest management?

Answer 3

False.

(Most postharvest pathogens are necrotrophic).

This means that all you have to do is keep the product alive (i.e. reduce respiration) and you’ll stop most of the pathogens from getting in.

Question 4

True or False?

Most postharvest pathogens are fungi.

Answer 4

True.

Question 5

How can the respiration rate of fruit be managed (reduced) postharvest?

Answer 5

• Chilling
  
  • ↓ temp = ↓ respiration rate
  • hydrocooling (cold water bath)
  • cool room
• ↑ [CO2] and ↓ [O2]
  
  • controlled atmosphere
  • wax coating (e.g. apples)
  • need to be careful
    
    • if [O2] too low, can cause anaerobic fermentation
    • if [CO2] too high it may cause wounding from toxicity issues
  • ↑ [CO2] will control fungal diseases more so than bacterial diseases