Factors to consider when ripening avocado Mary Lu Arpaia Univ. of CA Riverside, CA mlarpaia@ucanr.edu Why Ripen Avocados? Untreated, fruit ripening may range from a few days to even weeks within a carton Increase Uniformity Decrease Checkerboarding 1
History of commercial ripening J. Biale first described avocado ripening process (1941) I. Eaks outlined proper ripening protocols (1966) Lee and Coggins outline feasibility of commercial ripening and enhanced purchasing (1982) Henry Avocado and V. Tokar begin first large scale CA avocado ripening program (1983) US consumption climbs from < 1. lb/person (198) to 4.5 lb/person (211) 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 15 Carbon Dioxide Ethylene 4 Adapted from Eaks (1978) for Hass ml CO 2 /kg/hr 1 5 1 2 3 4 5 6 Days at 68F 3 2 1 ul C 2 H 4 /kg/hr 2
Relationship between dry matter (maturity) and final peel color Final Peel Color = 3.6261-.264DW +.2DW 2 where DW = Dry weight R 2 =.621 *** 6. 5.5 5. 4.5 Peel Color 4. 3.5 3. 2.5 Actual Final Color 2. Predicted Final Color 1.5 1. 1. 22.8 Dry Matter (%) Maturity and days to ripe 1 ppm propylene 18 no yes 16 14 12 1 8 6 4 1 2 3 4 5 6 7 8 9 1 11 12 13 14 15 16 17 Average Days to Eating Ripeness (<1.5 lbf) in response to 24 hour treatment of 4 ppm ethylene. 15 1 5 Days RAIN Ethylene NO YES Oil Content (%) Eaks, 198, JASHS (Harvest August - June) 1/25/ 3/7/ 4/18/ 6/1/ 7/11/ 8/22/ Harvest Date Ethylene hastens ripening regardless of stage of maturity 3
Time after harvest Ethylene has maximum benefit within 1-2 weeks of harvest Imported fruit if conventional shipment will need less time (24 hours or less) Imported fruit if CA shipped or 1-MCP treated may need longer treatment times Time after harvest 15 1 Days to <1.5 lbf 5 hr 24 hr 48 hr Time after harvest decreases the impact of ethylene days 7 days 14 days 28 days Days at 5C California Hass ; average of 3 harvests; 3 grower lots per harvest, 26 4
Note the affect of maturity, storage (3 wks @ 5C) and ethylene (5ppm) on the amount of days to ripe to <1.5 lbf at 2C as well as the variability of the data (checkerboarding) 25 California Hass 2 Days to Ripe 15 1 5 * g = ethylene treatment g* 3 3g g 3 3g g 3 3g g 3 3g g 3 3g g 3 3g Jan 27 Mar 7 Apr 18 Jun 1 Jul 11 Aug 24 LH2-25 fruit; San Diego fruit Harvest Date/Storage/Ethylene Even within lots of fruit there is variability in ripening a way to control this is sorting by degree of ripeness into different categories g33g 5
Suggested treatment times for California Hass avocados Early season fruit (November February) 36 72 hours Mid-season fruit (March June) 24 36 hours Late season fruit (July October) 8-24 hours +/- ethylene Management Issues Temperature Ventilation/Air exchanges Careful Monitoring Prompt Movement of fruit What is the proper stage of ripeness? Where do you ripen the fruit? 6
Factors under your control Educate yourself about the potential differences between varying sources of fruit there are differences Pre-ripening inspection Ripening management Postripening management Ripening Management Uniform heating and cooling is ABSOLUTELY ESSENTIAL Refrigeration needs to control the heat (6 BTU per pallet) Forced air ripening is critical (1 cfm/pallet) Venting (preferably flow through, keep CO 2 below 1%) Source of Ethylene as low as possible; physiologically you only need ~1 ppm but practically use 1ppm 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 7
Can I use a banana ripening room for avocado ripening? Some considerations Peak Respiration (mg/kg-hr) Refrigeration Load (BTU/T-day) 35 7 3 6 25 5 2 4 15 3 1 2 5 1 Banana at 14C Banana at 18C Avocado at 2C Banana at 14C Banana at 18C Avocado at 2C 8
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 Ethylene dose considerations Ethylene concentration >2 ppm; no more than 1 ppm Fruit Maturity Less mature; longer treatment Time after Harvest With increasing time after harvest; shorter durations needed 9
How much to apply? 1 ppm 1, 1 ppm ppm Short exposures to ethylene can trigger ripening; threshold is believed to be around 1 ppm Commercial application of 2-1 ppm is recommended Source: I. L. Eaks, UC, Riverside 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 (2C) Impact of high temperatures Delayed/uneven ripening Increased decay 1
The impact of Temperature (24 or 48 hours) on ripening performance of Hass avocado Days to Ripe 16 14 12 1 8 6 4 2 d c a b 5 The outcome is delayed or 2inhibited 25 3 35 Temperature (C) during 24 or 48 hr Holding Keep temperatures below 25 21 C 2 25 3 35 Temperature (C) during 24 or 48 hr Holding Stem End Rot (%) Body Rot (%) 35 3 25 2 15 1 2 15 1 5 c a ab bc High temperatures are DETRIMENTAL ripening and increased decay ab b b a 2 25 3 35 Temperature (C) during 24 or 48 hr Holding No significant difference due to duration Hass Avocado Ripening temperature influences final peel color Cox et al, 24, PH Biol. Tech. 11
Ripening Hass at different temperatures Days to Ripe 9 8 7 6 5 4 3 2 1 Days to Ripe Hue angle 15⁰C 18⁰C 2⁰C 23⁰C 25⁰C Ripening Temperature 85 83 81 79 77 75 73 71 69 67 65 Hue Angle Ripening Management When 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 12
Ripening Management What should you do with ripe fruit? Cool immediately; ideally within ripening room How long can you hold the fruit? Depends on the stage of ripeness Ripe fruit (<2 lbf) can be held at lower temperature generally than unripe/partially ripe fruit; minimize peel damage Fruit will continue to soften in storage but has minimal impact on fruit flavor Risk of decay increases with longer holding periods Managing Ripe Fruit Decay increases with increasing ripeness; accelerates in overripe fruit Don t hold fruit for long periods of time that are partially ripe increased chilling injury Bruising increases with advancing ripeness Protect fruit Peel color at slicing or guacamole ripe does not necessarily mean the fruit needs to be completely black! These are issues wherever fruit are ripened 13
The outcome of ripe fruit Ripe fruit at retail level has greatly increased consumption, HOWEVER.. Greater challenge in temperature management Fruit sensitivity to damage greatly enhanced Problems at retail 14
Example of fruit shriveling Example of an overripe fruit with stem end rot, body rot and internal bruising Example of a stem end rot Example of body rots A. B. A. Fruit with no bruising under the peel. B. Fruit which is very overripe and is exhibiting bruising under the peel. A. C. B. A. Very ripe fruit compressed by other fruit on display. B. Example of internal bruising. C. Very ripe fruit showing severe internal damage. 15
Considerations for successful avocado ripening Temperature management is CRITICAL Too high; ripening inhibited and increased decay Too low; ripening is slowed and lose benefit Fruit Maturity More mature; less time Time after Harvest After storage; less time Avoids delays in marketing Minimize fruit handling Checklist Know the history of the fruit Quality; don t use stressed fruit Standardize fruit size and maturity Uniform warming and cooling Careful monitoring; don t overripen CONSUMER/MARKET Education Additional information Contact me mlarpaia@ucanr.edu UC Davis Postharvest Center website http://postharvest.ucdavis.edu/ California Avocado Commission website http://www.californiaavocado.com/ripening-andhandling/ General information on avocados www.avocadosource.com 16