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PHSC June 2012 19-Jun-11
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Introduction to….. Impact of Preharvest Factors Affecting Quality and Safety
of Horticultural Foods
UC Postharvest Technology of Horticultural CropsJune 13, 2011
T. Suslow Dept. Plant [email protected]
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Impact of Preharvest Factors Affecting Quality and Safety
of Horticultural Foods
Factors that impact condition or quality
Brief look a microbial food safety: Preharvest
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Intrinsic quality cannot be improvedduring postharvest management
GOAL - optimal postharvest quality
• visual • sensory • nutritive attributes• achieving storage potential
Reaching your goal is determined or greatly influenced by plant variety selection, preharvest management, and
seasonal or weather-related events
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Our topic focus….Quality factors that cannot typically be avoided, graded, or scored at harvest
Preharvest infection shows up during storage
Preharvest internal defect; poor irrigation management or excessive rainfall
Sunscald becomes more apparent with ripening of MG tomato
Diverse Internal Defect Detection
In-line technologies and handheld units
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Sun injury (sunburn) May be hard to see until fruit ripen
Credit M. Cantwell UCD
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Preharvest Factors Affecting QualityPrinciples underlying our expectations
• The interaction between variety, location, and season should not be underestimated
• These outcomes cannot always be predicted
• Fertility management can greatly impact postharvest quality - directly and indirectly
• Fertility management impacts postharvest decay susceptibility - directly and indirectly
• Crop water status can significantly determine postharvest quality and phytonutrient content
• Plant canopy and microclimate manipulations affects postharvest quality
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Variety Selection:Genetics Plays a Huge Role in Postharvest Quality
Breeding and selection strategies include; Best overall performance in all regions Best performer within region or season Time to maturity within a region+season Uniformity of maturity – vegetative; flower; fruit
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Cultivar Shrivel * % weight loss
Ahern 299 3.5 13.2
Amsterdam 3.2 15.2
Harris LI-34 4.6 15.6
Hazera 1319 4.3 18.0
Rotterdam 2.4 11.8
TC 1260 3.6 14.9LSD.05 0.6 1.5
*Shrivel score -1-5 scale, 1=none, 2=slight, 3=moderate, 4=moderately severe, 5=severe
Role of cultivar in postharvest quality loss Example: Grape tomatoes and weight loss
Cantwell, 20041 2 3 4 5
12days 20C 50%RH
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Carrot varieties have been genetically bred for mechanical harvest and uniform internal color
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CARROT CRACKING- Variety is very important- Temperature is a minor factor- Cracking is increased by high N fertilization
Cantwell, UC Davis
I. ImperatorD. DominatorC. CellobunchN. Nantes
12Temperature
Cra
ckin
g In
dex
(Tot
al %
car
rots
cra
cked
/hei
ght
wh
en
drop
ped
2, 3
, 4 a
nd 5
feet
)
0
10
20
30
40
50
60
70
80
90
100
110
2.5°C36°F
12.5°C(55°F)
20°C (68°F)
Effect of Carrot Variety and Temperature on Cracking
CultivarImperator Dominator
Cellobunch
Nantes
Cantwell, UC Davis
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Impact of Soil Quality and Seed Bed Preparation on Market and Sensory Quality
Green Core & Green Shoulders
Predisposing factors• Compacted soil• Sub-surface hardpan• Poor foliar disease management
Consequences• Visual – green core• Non-visual – bitter, soapy flavor• High harvest losses
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Environmental factors: Impact on sensory and nutrient content
Examples
Soil type, texture, pH Air temperature Soil temperature Light availability Light quality Field vs. glasshouse Air pollution Altitude
Genetics + environment generally determine outcome
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Microclimate management
Leaf removal within canopy reduces RH and lowers Botrytis incidence and sporulation
Gray Mold (Botrytis cinerea)
Impact of Environment on Postharvest Disorders and Disease
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Den Outer, R.W. and W.H.L. Van Veenendaal, 1988. Gold specks in tomato fruits(Lycopersicon esculentum Mill.). J. Hort. Sci., 63: 645–649
Impact of Environment on Postharvest Disorders and Disease
Photo credit: J. Bartz UFL 2011
• High temperature and humidity• High nitrates and PO4• Leads to calcium oxalate crystals• Pierce cells; apparent on ripening
Load Incidences > 50%Can lead to rapid decay
Gold Speckles
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a. Impact bruiseb. Compression bruisec. Calcium deficiency (Blossom-end Rot)d. Preharvest flower infection
What caused this quality defect that showed up on >30% of packed fruit 10 days after harvest ?
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Preharvest infections may form quiescent infections that remain dormant until ripening
• Reduction of inhibitory compounds• Cell wall disassembly – release of activators and
nutrients
High RH and cool temperatures promote floral infections after pollination
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Blossom scarBlossom scar
Infection TraceInfection Trace
Alternaria spp.
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Plant health under the soil surface is the root of many postharvest disorders
Calcium disorders Thin fruit wall Browning potential Hollow-heart Pith decline Blotchy-ripening Sunscald
Examples:
Good Root:Shoot Ratio Poor Root:Shoot Ratio
Soil Texture Triangle
Soil texture is considered a fixed basic property
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Water availability according to soil texture
Pith Breakdown of Celery a Preharvest and Postharvest Disorder
Transplant Quality - Root Health Irrigation and Micronutrient Management Climate Interactions – cold or hot Non-uniform maturity – harvest timing decision
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Irrigation and Fertilization
NITROGEN FERTILIZATION
• High N associated with excess vegetative growth
• High N associated with high leaf protein and pigment concentrations (chlorophyll, carotenoids)
• High N associated with reduced postharvest life due to increased susceptibility to decay, mechanical damage and physiological disorders
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Tomato fruit that develop during K+ stress conditions can be puffy, soft, low in acidity, irregular shaped, blotchy ripening, and susceptible to ripening-related decays
Example:
Excess Nitrogen Applications Interfere with Potassium Uptake
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Wall-thickness is important for shipping qualityPrevents high rates of water loss/softening
Good wall thickness is inhibited by Irregular irrigation Excessive N and high temperatures Heavy fruit set (less problem with hybrids)
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High Nitrogen Reduces Cuticle Density and Increases Water-loss Softening
NITROGEN FERTILIZATION (lbs/ac)
0 175 325
CU
TIC
LE
DE
NS
ITY
(µ
g/m
m2 )
9
10
11
12
RA
TE
OF
WA
TE
R L
OS
S(%
F.W
./day
)
0.16
0.17
0.18
0.19
0.20
0.21
0.22
Cuticle Density
Water Loss
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Lower NitrogenLower Nitrogen Higher NitrogenHigher Nitrogen
Cuticle Thickness Influences Brown Rot Susceptibility
Differences Observed in Cuticle Roughness due to N-dose
250ppm total N75ppm total N
Roughness HydrophobicityE. Gutierrez et al. 2012
Leaf “Wet-ability” increases with loss of cuticle roughness
Greater surface‐tension o more rounded droplet o water beading
Less surface‐tensiono droplet collapseo water spreadingo Increased internalization
Photos from E. Gutierrez, UCD 2011
• Many leaf surface bacteria produce surfactants• Movement to leaf exudate nutrients• Entry to stomata and hydathodes• Increases preharvest and postharvest decay• Survival and internalization by human pathogens
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Boron deficiency malformation of stone fruitscorking of apples, apricots, pearslumpy rind of citrusmarking face in olivescracking of apricots
Calcium deficiency bitter pit of applesblossom end rot of tomatoes, peppers and watermelonscork spot in apples and pearsblack-end in pearsbrown discoloration of apple tissuered blotch of lemon
(from Kader, 1996)
FRUIT DISORDERS CAUSED BY MINERAL DEFICIENCIES OR EXCESSES
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Physiological Role of CalciumCalcium is an important mineral
determining quality and decay resistance.Examples of impacts of low Ca concentration Internal breakdown Accelerated senescence Increased rate of softening of fruit Increased decay potential, especially at wounds More susceptible to physiological disorders
Blossom end rot in tomato & pepperBitter pit in apples
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Fertility Management and Phytonutrients
The effects of mineral nutrition on plant phytonutrients minimally depends on
1) the nutrient
2) the nutrient form
3) the phytonutrient
4) inherent levels determined by genetics
5) irrigation practices
6) may be elevated or reduced by stress factors
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1. Maximum postharvest quality can be achieved only by understanding and managing the various roles that preharvest factors play in postharvest quality
2. Preharvest factors impact phytonutrientcontent and sensory volatiles
Summary Points
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Impact of Preharvest Factors Affecting Quality and Safety
of Horticultural Foods
Factors that impact condition or quality
Brief look a microbial food safety: Preharvest
Commodity-Specific GAPs and Food Safety Audit Checklists
• Melon• Tomato• Stone fruit• Mushroom• Lettuce & Leafy Greens• Culinary Herbs• Green Onions• Sprouts• Almond• Citrus• Strawberry• Watermelon• Blueberries • Asparagus
FOOD SAFETY PROGRAMGood Agricultural Practices: Growing the World’s Safest Strawberries
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Available data from many labs and outbreak investigations points towards
HIGH RISK POTENTIAL
The general conclusion is ……
Environmental, Biological, and Control Measures create natural and applied hurdles that result in a
VERY LOW RISK EXPOSURE
Understanding and Enhancing Hurdles to the Consequences of Contamination
Preharvest Postharvest
Produce Food Safety Begins with a Complete Preharvest Hazard Analysis
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Site selection Animal influences Fertility inputsWater inputs Irrigation mode Foliar sprays HarvestWorker hygiene Field Sanitation Equipment Sanitation
Oso Ranch1Block 2
WildlifeIntrusion
Pest Control
Irrigation
LandPrep
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Take Home Lesson:
Remember the Five P’s
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Preharvest
Planning
Prevents
Postharvest
Problems
