Session Six Postharvest quality, outturn New Zealand and Australia Avocado Grower s s Conference 05 20-22 22 September 2005 Tauranga,, New Zealand
Avocado Postharvest Quality An Overview Mary Lu Arpaia University of California, Riverside
Limitations to avocado postharvest handling Preharvest Factors Postharvest Factors Fruit maturity and quality Storage duration Stage of ripeness
Susceptibility to low storage temperatures External Chilling Injury Internal Chilling Injury
Body Rot Postharvest Diseases Stem End Rot
Anthracnose Body Rot Alternaria Stem End Rot Dothiorella Stem End Rot
Relationship between fruit age and unsound fruit % Unsound fruit (5% threshold) 100 90 80 70 60 50 40 30 20 10 2000 2001 2002 y = 0 + 0.02762*exp(days/5.203) r 2 = 0.82, n= 50, p<0.001 0 22 24 26 28 30 32 34 36 38 40 42 44 Age when ripe (days) Dixon, Pak and Cutting
The continuum The most important thing to remember is that there is a continuum from the grower to the consumer The steps in the continuum Grower Packer Distribution - Consumer
Avocado Quality Attributes Can mean many things, depending at what point one is assessing the fruit How do you as a grower perceive quality? Appearance Factors Fruit size and shape, peel texture Freedom from defects such as insect scarring, wind damage, limb rub
Avocado Quality Attributes cont. Past the grower the Packinghouse Appearance to maximize packout of #1 fruit History of the grove STRESS, LOCATION Picking conditions HOT, DRY vs WET Delay from harvest to packer Time of season - MATURITY
Avocado Quality Attributes cont. Past the grower Distribution Source of fruit at certain times of the year - MATURITY Product Uniformity Ability to take ethylene in a predictable manner Have some storage life to adapt to marketing situations
Avocado Quality Attributes cont. Past the grower Consumer Source of fruit? Is there a difference between growing areas? Product Uniformity Ability to predict when ready to eat Freedom from defects Eating quality
Preharvest factors influencing fruit quality
Preharvest Factors Environmental Rootstock/Scion Spacing and Pruning Pest Management PGRs Irrigation Nutrition These factors are interactive and influence each other
How preharvest factors may influence fruit quality Development and maturation Physical effects on quality and packout Susceptibility to physiological and pathological breakdown
Climate and environment Temperature Wind Rainfall Fruit position on tree
Beware of discoloured stems Freeze Damage = Cold Stress Can see increased decay and low temperature damage after storage Effects could last for several weeks/months
Relationship between rainfall and peel damage rainfall (mm) 40 30 20 10 daily rainfall peel damage (severity) 0 10/08/01 30/08/01 19/09/01 9/10/01 29/10/01 18/11/01 8/12/01 28/12/01 pick date 80 75 70 65 60 55 50 45 40 35 30 25 20 15 10 5 0 Peel damage severity (%) Dixon, Mandemaker, Pak and Cutting
Body rots 10 severity (%) 8 6 4 2 Influence of rainfall prior to harvest on Decay 0 0 1-5 5-10 11-15 16-20 >20 rainfall (m m ) stem-end rots 60 50 incidence (%) 40 30 20 10 Dixon, Mandemaker, Pak and Cutting 0 0 1-5 5-10 11-15 16-20 >20 rainfall (m m )
Clonal Rootstocks Enhanced yield possible Control of root rot Rootstock and Variety Interactions 500 Cumulative yield per tree (kg) Years after Planting 2 3 4 5 6 7 8 9 10 400 300 200 100 0 Borchard Duke 7 Toro Canyon Topa Topa D9 G755A G755B G755C Clonal Rootstock
Nitrogen Nitrogen:Calcium Ratio Ratio 2.7 2 2.5 1.8 % dry weigh 2.3 2.1 1.9 G755C Duke 7 D9 Toro Canyon 1.6 1.4 1.2 1 G755C Duke 7 D9 Toro Canyon 1.7 0.8 1.5 1991 1992 1993 1994 1995 Year 0.6 1991 1992 1993 1994 1995 2.7 2.5 Calcium Calcium Rootstock can influence nutrient composition 2.3 % dry weigh 2.1 1.9 G755C Duke 7 D9 Toro Canyon Leaf analysis results 1.7 1.5 1991 1992 1993 1994 1995 Year
Rootstock and Variety Interactions Ca (g kg -1 DW ) 0.40 0.35 0.30 0.30 0.25 0.20 a ns b Fruit skin Fruit flesh a ab 1999 2000 Year b b c a a Seedling Velvick Clonal Velvick Clonal Duke 7 Rootstock influences Calcium levels in in the fruit
Fruit acceptability (%) 100 75 50 25 a b a b b a ns b b a SV CV CD Rootstock and Variety Interactions Results from Australia 20 yr-old trees 0 1999 2000 1999 2000 Diffuse discolouration Vascular browning 4 wks @ 5C Rootstocks affect Hass avocado fruit rots and physiological disorders Flesh volume (%) 40 SV CV D7 30 20 10 Seedling Velvick Clonal Velvick Duke 7 c b a a a b Marques, Hofman 2002 Non-stored Stored
Effect of long-term irrigation regimes on the browning potential of 'Fuerte' avocado after 30 days storage 1.4 1.2 1.0 0.8 0.6 0.4 0.2 0.0 PPO activity 35 kpa 55 kpa 80 kpa Irrigation Regime J.P. Bower, 1988 Irrigation effects on on fruit quality Increased browning potential following storage = mesocarp discoloration
Canopy Management/Pruning May have an effect on fruit quality Aim at fruit requirements not wood
% of flesh affected 1.8 1.6 1.4 1.2 1 0.8 0.6 0.4 0.2 0 Leonardi, Whiley, Hofman b Unpruned ab Pruned after harvest Increased vegetative vigor from pruning can result in in increased decay and physiological disorders % of flesh affected a Pruned again in summer 4 3 2 1 0 b Unpruned a Pruned after harvest 2001 2002 Diffuse discoloration a Pruned again in summer ab Pruned in summer + Sunny
Avocado Seasonal Calcium Concentration 10 Fruit Ca (mg/kg DW)(X1000) Vigorous 'Fuerte' Non-Vig 'Fuerte' 8 Vigorous 'Hass' Non-Vig 'Hass' 6 4 2 0 0 2 4 6 8 10 12 14 16 18 20 22 24 26 Weeks after Fruit Set G.W. Witney et al., 1990 Tree vigor influences calcium levels in in the fruit Calcium affects the rate of of ripening Regression of Days to Fruit Ripening and Calcium Concentration y = 0.0056x + 4.856, r = 0.92** Days to Ripen 16 14 12 10 8 6 0 500 1000 1500 2000 2500 Calcium (mg/kg DM) Witney et al., 1990
3 r = 0.83** 2 Diffuse discoloration (1-5) Calcium fruit levels influences susceptibility to physiological problems and decay 1 200 300 400 500 Calcium concentration (mg kg -1 ) Anthracnose severity (1-5) 4 3 2 r = 0.88** 1 200 300 400 500 Calcium concentration (mg kg -1 ) Hofman, Vuthapanich, Whiley, Klieber, Simmons 2001
PRE-HARVEST GROWING CONDITIONS WILL INFLUENCE POSTHARVEST QUALITY INTERACTION BETWEEN * orchard temperatures and rainfall mainly external defects/decay * vegetative growth/nutrient balance external and internal defects EXTENT OF PROBLEMS INFLUENCED BY * water stress * rootstock * canopy management strategies
Harvesting Operations Minimum Maturity Standards Harvesting Methods Delay between field and packer Harvesting conditions
Fruit quality to consumers is limited by harvest maturity: Immature watery, shriveling, inconsistent ripening, physiological disorders, susceptible to decay Overmature can be dry, rancid, seed germinating and more susceptible to decay
Physiological disorders accentuated with low maturity fruit External Chilling Injury Flesh Discoloration
Checkerboarding = Ripening Variability Difficult to predict time of ripeness; worse with low maturity Great variation in the days to ripe within a package even with ethylene treatment RESULT: Lack of ripe uniformity means more loss at point of purchase
Poor RIPE Skin Colouration
TASTE 2002-2003 Hass Maturity Project (Preliminary Results) ALL DATA Hedonic score vs. Dry weight California 2002-03 results with Ventura Co. Hass fruit 9.0 Average Hedonic Score 8.5 8.0 7.5 7.0 6.5 6.0 5.5 5.0 4.5 4.0 3.5 3.0 2.5 y = 0.1874x + 1.6404 R 2 = 0.6052 2.0 1.5 1.0 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 Percent Dry Weight Like moderately Like slightly Neither like or dislike Dislike slightly Dislike moderately Clearly at lower DW values, acceptability of fruit is marginal Data suggest that for a score of 6 the CA dry matter will be approximately 23%
Physical damage and chilling Skin spotting (Nodule damage) Discrete patches (chilling damage)
Physical damage and chilling
The importance of temperature management when harvesting From the grove onward
Protecting the fruit after harvest from high temperature has implications in the market place Temperature (F) 105 95 85 75 65 55 105 95 85 75 1100 1130 1200 1230 1300 1330 1400 1430 1500 1530 Time Air Uncovered Space Temperature (F) BOTTOM TOP During the course of the day, fruit in the TOP 12 of the bin with no protection can reach temperatures in EXCESS of 35C whereas covered bins or those held in the shade can maintain temperatures close to ambient Fruit at the BOTTOM of the bin stay cool during the day 65 55 1100 1130 1200 1230 1300 1330 1400 1430 1500 1530 Time Air Uncovered Space Source: Arpaia, M. L., 1994; Hass fruit harvested from Riverside county.
What is the outcome of high temperatures in the field after harvest? 40 % Decay 40 % Moderate/Severe Discoloration 30 30 20 20 10 10 0 Uncovered Space Blanket Uncovered Space Blanket 0 Uncovered Space Blanket Uncovered Space Blanket BOTTOM TOP BOTTOM TOP Fruit from the BOTTOM of the bin (lower temperatures) had lower decay and less chilling injury after storage at 5C and ripening. However, fruit from the TOP of the bin, which were warmer, had higher levels of both decay and chilling injury. This is especially true for the fruit which came from the uncovered bins. Source: Arpaia, M. L., 1994; storage was for 6 weeks at 5C.
Short Duration High Temperature Effects on on Hass Fruit Storage and Quality (Arpaia, 1994) Pulp temperature effects during delayed cooling on fruit quality following 4 weeks at 5C m/s chilling injury decay Pulp Temp Control 20C 30C 40C Delayed cooling effects on fruit quality following 4 weeks at 5C 0 2 4 6 8 Percent of Total Fruit m/s chilling injury decay Cooling delay 0 hr 6 hr 12 hr 24 hr 0 2 4 6 8 10 Percent of Total Fruit
Considerations in the grove Keep fruit in a cool place, out of the sun Handle the fruit gently Work with packinghouse to minimize delays from time of harvest to cooling Avoid picking when temperatures are high especially with late season fruit Avoid picking during or shortly after a rain event more decay Worker Safety; HAACP considerations for the future
Limitations to avocado postharvest handling Fruit maturity and quality at time of ripeness Immature watery; inconsistent ripening Overmature can be dry; seed germination and more susceptible to decay Time after harvest and how fruit are managed Increased risk of physiological disorders Stage of ripeness Ripe for tonight More difficult to handle ripe fruit
Market Fruit Quality Surveys Conducted in collaboration with CAC Merchandising Staff
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.
The average incidence of fruit quality problems judged to be either slight or moderate to severe. 100 90 80 Moderate to Sever e Slight 70 % of total fruit 60 50 40 30 20 10 0 Firmness Shrivel Internal Bruising Bruising under Peel Body Rot StemEnd Rot Observed Problem Market Survey, 2005
The link between the preharvest environment and fruit quality BOTTOM LINE: Quality does NOT improve after harvest Nutritional management N, Ca relationships Rootstocks/pollinizers what is their influence? Stress Cold, Salinity, Irrigation management Canopy management managing light and tree vigor Fruit handling prior to the packhouse All contribute to fruit quality; interact w/ each other Important to consider fruit maturity as well
Thank you!