Healthy fridge

Question 1

storage and distribution in the dark

Answer 1

-chlorophyll, protein and carbohydrates (starch,sugars) decrease -> PCD dark induced senescence

• other presumed health promoting compounds decrease
• glucosinolates (cabbage,kale), flavanoids, carotenoids, lycopene, anthocyanine
• vitamins (broccoli -> ascorbic acid decreases in dark)

Question 2

Effect of white light at room temperature on postharvest senescence of broccoli heads

Answer 2

With light at room temperature -> slowing down of senescence

Question 3

• Dark storage at low temperatures can be replenished by light storage with room temperature

Answer 3

• storage with light increases quality in post harvest even without cold temperature especially in green vegetables (fresh cut lettuce)
• dark storage with high temperature -> tissue disintegrated

Question 4

Effect of light on postharvest quality of fresh-cut lettuce (1/2)

Answer 4

• less browning on cut edged
• less senescence (more crisp) -> EC measurements for senescence
• longer shelf life

Question 5

Effect of light on postharvest quality of fresh-cut lettuce (2/2)

Answer 5

1. low light (5 μmol) preserves Vit C
   - > reverses the reaction of polyphenol oxidation -> less pinking & browning coloration
2. low light accumulates carbohydrates (more sweetness less bitterness)
   * carbohydrates go down in the dark!

Question 6

Light improves quality and shelf life

Answer 6

• light levels 5-30 μmol/m2/s improve visual quality and shelf life of fresh-cut lettuce
• all colors work (red,green,blue,white)
• increase in Vit C and sugars
• it works through photosynthesis

Question 7

Light photosynthesis and Vitamin C biosynthesis

Answer 7

Light brings the plastoquinone signalling in a different level which is responsible for the trasport of electrons & proteins in the lumen.
L-ascorbate supresses the browning in post harvest

Question 8

Light compensation Point (LCP)

Answer 8

• Definition: the amount of light required for the rate of photosynthesis to be equivalent to the rate of respiration.
• Light below LCP: Respiration is higher than photosynthesis (in darkness) so there is no photosynthetic sugar production.
• LCP lettuce under cultivation conditions is around 30-50μmol /m2/s

Question 9

Respiration and temperature

Answer 9

• Sugar accumulation depends on its production (through photosynthesis and its consumption (through respiration)
• In the cold respiration decreases to very low level whereas photosynthesis is not greatly affected
• lettuce in the dark has more sugars that may give more respiration which is not what we want

Question 10

Better leave the light on!!

Answer 10

• respiration is severely supressed at low temperature (5-7degress in the fridge)
• photosynthesis is still high, all light colors are effective
• this leads to sugar and vit C production
• because the product is harvested the nutrients accumulate
• better quality and healthier products