Cold

Cold

1. freezing damage

   • inter/intra cellular ice formation
     • Tissues burst
   • sugar content affects freezing temp

2. chilling injury

   • skin imperfections/can spread into crop
     • pitting
     • browning
     • spots
     • darkening
     • skin streaks
   • above freezing
   • below 15C
     • more noticeable when moved to warm conditions

3. south and central America crops prefer 10-15C

   • potato
   • tomato
   • banana
   • mango

4. North Europe crops don't mind it colder 0-1C

   • swede
   • carrot
   • cabbage

5. 7/8ths cooling time

   • time taken to remove 7/8ths of the heat
     • affected by...
       • rate of heat transfer
         • size/area
       • temperature differential
         • bigger the difference quicker it cools
       • nature of cooling medium
         • heat energy coming out makes it cold
           • water takes more heat than air
       • thermal conductivity of cooling medium
         • solid is better, high mc% is better
       • uniformity of cooling

6. field heat 20-40C

   • pre-cool 0-10C
     • chilled storage 0-10C
     • 5C within 4hrs
       • M&S
     • systems
       • room cooling
       • forced air
       • hydrocooling
       • icing
       • vacuum
         • can be destructive