Introduction & Heat Removal
What is precooling?
- Removal of field heat asap after harvesting
Mention the ingredients for making ice slurry
crushed ice, water, salt
What is chilling injury?
crops develop abnormalities (temperature associated physiological disorders) when exposed to temperatures above those which would cause them to (about to) freeze
Mention 2 advantages of precooling
Inhibition of the growth of decay causing MO
Restriction of enzyme activities
Reduction of water loss from harvested products (due to respiration)
Reduction in rate of respiration and ethylene
Prolonged longer shelf life
2 considerations to select proper cooling method
•Volume of product
•Compatibility of the method with the commodities to be cooled
•Subsequent storage
•Shipping condition
•Fix/ variable cost of the system
What is the consequence of chilling injury?
susceptible to MO --> low quality --> short shelf life
Mention 2 factors affecting precooling
–Accessibility of product to the refrigerating medium
–Difference between T° crops and T° medium (storage)
–Velocity of refrigerating medium
–Type of the cooling medium
–Heat transfer from crop to cooling medium
3 methods of hydrocooling
flooding, spraying, complete immersion
Mention 3 symptoms of chilling injury
–Surface lesions
–Discoloration
–Internal breakdown
–Failure to ripen in climatic fruits
–Different forms of external abnormalities
–Susceptibility to microbial infection
–Wilting
–Loss of flavor
–Decay, shorten shelf life
Mention 2 crops that require curing instead of precooling
onion, garlic, yam,
Ideal arrangement for the crops if we want to place it in room cooling
to leave some spaces (~2.5 cm) in order for produce to cool more quickly. Produce in vented boxes will cool much faster than produce packed in un-vented containers.
Mention 3 factors of chilling injury
–Exposure time
–Cultivar
–Environment conditions in which the crop was grown (temperature, precooling, chemical treatment, hormonal regulation, controlled atmosphere storage)
Example of application of conduction in precooling fruits/ vegetables
top ice --> ice in contact directly with the fruits/ veggies. Plate in the refrigerator in contact directly with the fruits/ veggies
3 drawbacks of vacuum cooling
water loss --> reduce weight, quality (shrinkage), less appearance
What cause mealiness in peach?
•Accumulation of pectin in intercellular space
•Low temperature lead to degradation and separation of parenkim mesocarp in plant-cellà filled by pectin