1 Factors to consider when ripening avocado Mary Lu Arpaia Univ. of CA Riverside, CA [email protected]Limitations to avocado postharvest handling v Time after harvest (fruit age) v Stage of ripeness – more difficult to handle “ripe” fruit v Mismanagement at any point in the handling chain v Fruit maturity 22 24 26 28 30 32 34 36 38 40 42 44 0 10 20 30 40 50 60 70 80 90 100 % Unsound fruit (5% threshold) Age when ripe (days) 2000 2001 2002 y = 0 + 0.02762*exp(days/5.203) r 2 = 0.82, n= 50, p<0.001 Dixon, Pak and Cutting Time after harvest influences the percentage of unsound fruit What we know about the avocado and why it responds to ethylene • A climacteric fruit showing an increase in respiration and ethylene production during ripening • Influenced by maturity, time after harvest, temperature and atmosphere 0 1 2 3 4 5 6 Days at 68F 0 50 100 150 0 100 200 300 400 Carbon Dioxide Ethylene ml CO 2 /kg/hr ul C 2 H 4 /kg/hr Adapted from Eaks (1978) for ‘Hass’
• Uniform heating and cooling is ABSOLUTELY ESSENTIAL• Refrigeration needs to control the heat (6000 BTU per
pallet)• Forced air ripening is critical (1000 cfm/pallet) • Venting (preferably flow through, keep CO2 below 1%)• Source of Ethylene – as low as possible; physiologically you
only need ~10 ppm but practically use 60 - 100ppm• Fruit needs to be easily accessible in ripening room for
monitoring; especially if fruit is of varying arrival condition or multiple lots of fruit
• Keep good records
Can I use a banana ripening
room for avocado ripening?
Some considerations
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Can I use a banana room….. With some practical modifications
Refrigeration during ripening and cooling of fruit likely to be insufficient in a banana room
– Hot spots within pallet– Uneven ripening
Do not to overload the room
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Ethylene dose considerations
• Ethylene concentration– >20 ppm; no more than 100 ppm
• Fruit Maturity– Less mature; longer treatment
• Time after Harvest– With increasing time after harvest;
shorter durations needed
How much to apply?
Short exposures to ethylene can trigger ripening; threshold is believed to be around 10 ppm
Commercial application of 60 -100 ppm is recommended
Source: I. L. Eaks, UC, Riverside
10, 100 ppm
1 ppm
0 ppm
Temperature Management
• Avocados have a VERY high rate of respiration during ripening = HEAT
• Efficient warming/cooling of fruit essential
• Airflow essential to maintain proper pulp temperature (20C)
Impact of high temperatures– Delayed/uneven ripening– Increased decay
The impact of Temperature (24 or 48 hours) on ripening performance of ‘Hass’ avocado
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§ High temperatures are DETRIMENTAL§ The outcome is delayed or inhibited
ripening and increased decay§ Keep temperatures below 21 C
No significant difference due to duration
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Ripening temperature influences final peel colorCox et al, 2004, PH Biol. Tech.
‘Hass’ AvocadoRipening Hass at different temperatures
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Ripening ManagementWhen do you turn off the gas?
• You don’t need the gas until ripe; a short duration treatment will “trigger” ripening
• Fruit may soften but may not color – maturity and other factors involved
• The best way to gauge the rate of softening is with a penetrometer…not your fingertips or buttons “popping”
• Fruit maturity is an important variable
The penetrometer is a tool to judge the relative stage of ripeness
How long can I hold ripe or partially ripe fruit?
• Fruit continue to soften in storage• Partially ripened fruit held at 50F
(10C) can develop pink staining especially if held longer than 1 week
• Fruit can be successfully held at 34F (1C) for up to a week
• Is there a difference in eating quality?
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Managing Ripe Fruit• Decay increases with increasing ripeness;
accelerates in “overripe” fruit• Don’t hold fruit for long periods of time that are
22.8%Taste and oil development during maturation of 'Fuerte'fruit grown at Irvine.
Sensory panel analysis
• Texture• Flavor• Overall acceptability
Avocado texture and acceptability
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Avocado flavor and acceptability
Sweet also associated with higher hedonic scores but at lower levels of response (30%)
Avocado season
Harvests taken throughout the season
Jan Sept
Analyzed samples from each harvest for sensory and quality attributesas well as aroma volatile content
What is the effect of maturity on flavor and what drives these flavor changes?
All samples were ripened to a similar firmness
Changes in key sensory attributes and “grassy” volatilecontent associated with increasing maturity
• Avocados were more liked with increasing maturity• This was associated with increased richness and creaminess and decreased grassiness• The decrease in grassiness paralleled a decline in volatiles with grassy aromas
Summary1. Avocados that were most liked by our sensory panelists were
described as having a creamy, smooth, buttery texture with richness, nuttiness and a minimum of grassy flavor.
2. Avocados contain aroma volatiles that likely help determine the flavor
3. Aldehydes, such as hexanal, were clearly associated with grassy flavor
4. Ripening led to a decline in soluble carbohydrates and in a number of aroma volatiles, hexanal being the most prominent
