AGEN2002 Lecture Notes - Lecture 4: Agronomy, Vacuole, Pollination

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4. Postharvest management of fruit & veg
Pre-harvest factor affecting quality
Genetics (cultivars, from selective breeding, taste different)
Climate (e.g. cold temp slows fruit filling in bananas, abnormal shapes)
Crop nutrition (e.g. salt increases sweetness in tomatoes, high N increase acidity in citrus)
Agronomy (e.g. high planting density reduces photosynthate)
Pollination (e.g. fruit shape)
Pest & disease
Postharvest temperature management
Immediately remove field heat after harvest: Hydro-cooling, vacuum cooling, forced-air cooling
(should be maintained at lowest safe temp)
Suppresses enzymatic degradation (softening) & respiratory activity
Slow-inhibit water loss (wilting)
Slow/inhibit growth of decay-producing micro-organisms (moulds & bacteria)
Reduce production of ethylene (a ripening agent)/ minimize the commodity’s reaction to
ethylene
Cold chain (temp controlled supply chain)
Transport
o Refrigerated loading area
o Cooling truck before loading
o Loading pallets towards
centre
o Avoiding delays
o Monitor product temp
Handling & storage
o Refrigerated unloading area
o Monitor product temp
o Quick transfer to proper
storage
o Refrigerated distribution &
retail
o Inventory management
Chilling injury in F&V
TCA (trichloroacetic acid) in F&V stored in vacuole (where pH is much lower than cytoplasm)
o If tonoplast (vacuolar membrane) damage = leakage of acids (damages the cell)
Phenolic oxidising enyzymes = 97% in vacuole
o Causes ‘cut-edge’ browning, enzymatic oxidative browning
o Physical injuries, chilling injury, challenge for ‘fresh-cut’
o Can use citric & ascorbic acid, lemon or pineapple juice to prevent browning (low pH
reduces enzymic activity)
Optimum storage temp
Banana, ginger, mature-green mango & tomato, sweet potato 13’C
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Document Summary

Cold chain (temp controlled supply chain: transport, handling & storage, refrigerated loading area, cooling truck before loading, loading pallets towards centre, avoiding delays, monitor product temp. Chilling injury in f&v: refrigerated unloading area, monitor product temp, quick transfer to proper storage, refrigerated distribution & retail. Inventory management: tca (trichloroacetic acid) in f&v stored in vacuole (where ph is much lower than cytoplasm) Ripening occurs because of ethylene: a natural plant hormone synthesized by all cells during normal cell development & growth, produced during ripening to cause rise in respiration rate (reduces shelf life) = climacteric". Climacteric fruit = increase ethylene, increase respiration (e. g. apple, avo, banana, fig, kiwi) Non-climacteric fruit = ripens without ethylene & respiration bursts (e. g. blueberry, cherry, citrus, cucumber) Low temperature (0"c depending on fruit: ca storage (high co2, low o2, hypobaric storage (reduced pressure) Ethylene inhibitors: 1-mcp (1-methylcyclopropene) gas that blocks ethylene receptors.

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