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