II European Short Course QUALITY & INNOVATION OF .... texture, 3. flavor 4. and nutritional quality (sugars, acids, vitamins and phytonutrients). Tissue browning, which can be a major

Cultivar selection and preCultivar selection and pre--harvest factors on the quality of freshharvest factors on the quality of fresh--cut cut vegetablesvegetables

MarMaríía Isabel Gil a Isabel Gil

Research Group in Quality, Safety and Bioactivity of Fruits and Vegetables CEBAS- CSIC, Murcia Spain

II European Short CourseII European Short CourseQUALITY & INNOVATION OF FRESHQUALITY & INNOVATION OF FRESH--CUT PRODUCECUT PRODUCE

Cordoba, March 10Cordoba, March 10--12, 200812, 2008

1.1. Examples of freshExamples of fresh--cut vegetables include shredded lettuce and cabbage, mixed lettucut vegetables include shredded lettuce and cabbage, mixed lettuce ce salads, peeled and sliced potato, washed and trimmed spinach, pesalads, peeled and sliced potato, washed and trimmed spinach, peeled eled ‘‘babybaby’’ carrots, carrots, cauliflower and broccoli florets, and cleaned and diced onions.cauliflower and broccoli florets, and cleaned and diced onions.

2.2. These products are expected to have a shelf life of 10 to 14 dayThese products are expected to have a shelf life of 10 to 14 days and represent about s and represent about 70% of the total volume of fresh70% of the total volume of fresh--cut items available commercially.cut items available commercially.

3.3. Other important vegetable items include peeled garlic, fresh dipOther important vegetable items include peeled garlic, fresh dips, sliced mushrooms, s, sliced mushrooms, sliced tomatoes and peppers and fresh microwavable vegetable trasliced tomatoes and peppers and fresh microwavable vegetable trays. ys.

4.4. More recent freshMore recent fresh--cut vegetable products include salad meals or cut vegetable products include salad meals or ‘‘home replacement home replacement mealsmeals’’, which contain meat and other food items., which contain meat and other food items.

FreshFresh--cut vegetablescut vegetables

FreshFresh--cut vegetablescut vegetables have grown rapidly during the past 20 years, extending from thehave grown rapidly during the past 20 years, extending from the food service sector to the retail shelffood service sector to the retail shelf

Minimal processingMinimal processing

Whereas most food processing techniques stabilize the product anWhereas most food processing techniques stabilize the product and lengthen their d lengthen their storage and shelf life, minimal processing of vegetables increasstorage and shelf life, minimal processing of vegetables increases their perishabilityes their perishability

The industry soon recognized that highThe industry soon recognized that high--quality raw material was required quality raw material was required because of the increased perishability caused by product preparabecause of the increased perishability caused by product preparationtion

Quality for freshQuality for fresh--cut vegetablescut vegetables

1.1. color, color, 2.2. taste, taste, 3.3. texture,texture,4.4. long shelf life,long shelf life,5.5. high content of healthhigh content of health--

promoting constituents.promoting constituents.

These quality attributes need to These quality attributes need to be maintainedbe maintained and and be consistentbe consistent all yearall year

The most important characteristics for freshThe most important characteristics for fresh--cut cut vegetables are:vegetables are:

The physical damage or wounding caused by preparation increases The physical damage or wounding caused by preparation increases ::

respirationrespirationethylene production ethylene production

BrowningBrowning

With associated increases in rates of other biochemical reactionWith associated increases in rates of other biochemical reactions responsible for s responsible for changes in:changes in:

1.1. color including browning, color including browning, 2. texture, 2. texture, 3. flavor 3. flavor 4. and nutritional quality (sugars, acids, vitamins and 4. and nutritional quality (sugars, acids, vitamins and phytonutrientsphytonutrients).).

Tissue browning, which can be a major defect of freshTissue browning, which can be a major defect of fresh--cut vegetables, depends on:cut vegetables, depends on:

1.1. concentration of concentration of phenolicphenolic compounds,compounds,2.2. activity of activity of polyphenolpolyphenol oxidaseoxidase (PPO), (PPO), 3.3. concentration of antioxidants in the tissue.concentration of antioxidants in the tissue.

O

O O

HOOH

COOH

OH

O

OCytoplasmCytoplasm

H

HO

OO

HOOH

COOH

OH

CloroplastCloroplast

VacuoleVacuole

oo--quinonequinone

diphenoldiphenol

PPOPPOOO22

MelaninsMelanins

BrowningBrowning

WoundWound--induced loss of cellular compartimentation between:induced loss of cellular compartimentation between:phenolic compoundsphenolic compounds mainly in the vacuole.mainly in the vacuole.and and PPOPPO in the cytoplasm.in the cytoplasm.

Result in Result in tissue browningtissue browning at a rate that increases with temperature and water stress:at a rate that increases with temperature and water stress:

BrowningBrowning

Commodities with constitutive Commodities with constitutive high levels of high levels of phenolicphenolic compoundscompounds, like artichoke and potato, brown , like artichoke and potato, brown easily when wounded tissue is exposed to the Oeasily when wounded tissue is exposed to the O22 in air. The exclusion of Oin air. The exclusion of O22 or the application of or the application of antioxidant controls browning in these commodities. antioxidant controls browning in these commodities.

In contrast, other commodities, like lettuce and celery, have In contrast, other commodities, like lettuce and celery, have low levels of naturally occurring low levels of naturally occurring phenolicphenolic compoundscompounds. Wounding stimulates . Wounding stimulates phenylpropanoidphenylpropanoid metabolism and the accumulation of metabolism and the accumulation of phenolicphenolic compounds leads to browning. compounds leads to browning.

While many modifications of the wound response could be implemenWhile many modifications of the wound response could be implemented through genetic ted through genetic engineering, the vigor of the resultant plant may be diminished engineering, the vigor of the resultant plant may be diminished because of its inability to respond because of its inability to respond to the many natural stresses during growth. to the many natural stresses during growth.

BrowningBrowning

Browning of freshBrowning of fresh--cut lettuce can be partially controlled by:cut lettuce can be partially controlled by:

a.a.-- rapid cooling and storage at 0rapid cooling and storage at 0ººC to minimize woundC to minimize wound--induced changes in induced changes in

phenylpropanoidphenylpropanoid metabolism. metabolism.

b.b.-- storage under low Ostorage under low O22 and high COand high CO22 controlled or modified atmosphere is also controlled or modified atmosphere is also

effective in reducing the synthesis, accumulation, and browning effective in reducing the synthesis, accumulation, and browning of of phenolicphenolic compounds. compounds.

c.c.-- induction of other metabolic pathways that are naturally antagoinduction of other metabolic pathways that are naturally antagonistic to wound nistic to wound

responses which could also protect against browning.responses which could also protect against browning.

Quality of the intact vegetable depends on:Quality of the intact vegetable depends on:

1.1. cultivar, cultivar,

2.2. preharvest cultural practices and climatic conditions, preharvest cultural practices and climatic conditions,

3.3. maturity at harvest, maturity at harvest,

4.4. harvesting method,harvesting method,

5.5. handling procedures, conditions, and time between harvest and prhandling procedures, conditions, and time between harvest and preparation as a eparation as a

freshfresh--cut product.cut product.

Quality of raw materialQuality of raw material

All these factors have major impact on quality All these factors have major impact on quality of intact vegetables and consequently, on of intact vegetables and consequently, on

quality of freshquality of fresh--cut productscut products..

Cantwell, M.I., Suslow, T.V. 2002. Postharvest handling systems: fresh-cut fruits and vegetables. In: Kader, A.A. (Editor), Postharvest Technology of Horticultural Crops. University of California, Oakland, pp. 445-463.

Iceberg lettuceIceberg lettuce can be stored for 1 week can be stored for 1 week but not more than 2 weeks before there but not more than 2 weeks before there are significant differences in browning are significant differences in browning rate of the salad product.rate of the salad product.

Romaine lettuceRomaine lettuce, cannot be stored for , cannot be stored for more then 1 week without reducing the more then 1 week without reducing the quality of the salad product.quality of the salad product.

Quality of raw materialQuality of raw material

Many freshMany fresh--cut vegetables are handled in an cut vegetables are handled in an ‘‘interrupted chaininterrupted chain’’ in which the product may be in which the product may be stored before processing or may be processed to different degreestored before processing or may be processed to different degrees at different locations.s at different locations.

Because of this variation in time and point of processing, the qBecause of this variation in time and point of processing, the quality of raw material and the shelf uality of raw material and the shelf life of the processed product could be affected. life of the processed product could be affected.

Preharvest factors often interact in complex ways and depend on Preharvest factors often interact in complex ways and depend on specific cultivar specific cultivar characteristics and growth stage sensitivities.characteristics and growth stage sensitivities.

Maximum postharvest quality for any cultivar can only be achieveMaximum postharvest quality for any cultivar can only be achieved by understanding and d by understanding and managing the various roles that preharvest factors play in posthmanaging the various roles that preharvest factors play in postharvest quality.arvest quality.

Before freshBefore fresh--cut attained its present importance, cut attained its present importance, generic productiongeneric production was often used. was often used.

In the past, freshIn the past, fresh--cut lettuce operations often salvaged lettuce remaining in the fcut lettuce operations often salvaged lettuce remaining in the fields after ields after harvesting for fresh market.harvesting for fresh market.

Preharvest factorsPreharvest factors

However, because of the differential responses of individual culHowever, because of the differential responses of individual cultivars to freshtivars to fresh--cut processing, cut processing, selecting a cultivar with minimal unwanted wound responses is esselecting a cultivar with minimal unwanted wound responses is especially critical with vegetables pecially critical with vegetables

destined for the freshdestined for the fresh--cut market. cut market.

MONALISAMONALISA SPUNTASPUNTA

AGATAAGATA AGRIAAGRIA CARACARA FRANCELINEFRANCELINE JAERLAJAERLA

LISETALISETA MANONMANON

Cultivar selectionCultivar selection

Days of storage at 4ºC0 1 2 3 4 5 6

0

3

6

9

LisetaAgria Cara MonalisaSpunta

Bro

wni

ng

Browning is an unwanted wound response Browning is an unwanted wound response especially critical for freshespecially critical for fresh--cut vegetablescut vegetables


Cultivar has an important role in determining the quality, tasteCultivar has an important role in determining the quality, taste, nutrient composition and , nutrient composition and postharvest life of vegetables. postharvest life of vegetables.


Iceberg

Romaine

Continen

talRed

oak le

afLollo

ross

oEsc

arole

Antioxidant Capacity

TEAC

100

g-1

f.w

.

0

200

400

600

800

Iceberg

Romaine

Continen

talRed

oak le

afLollo

ross

oEsc

arole

Vitamin C

mg

100

g-1 f.

w.

0

5

10

15

20

25


IcebergRomaineContinentalRed oak leafLollo rossoEscarole

Total phenolics

mg

100

g-1

f.w.

0

200

400

600

Nutritional quality particularly Nutritional quality particularly phytonutrientsphytonutrients and some antioxidant vitamins and some antioxidant vitamins may also vary greatly according to cultivar may also vary greatly according to cultivar

FreshFresh--cut products generally have higher respiration rates than the cocut products generally have higher respiration rates than the corresponding rresponding intact product.intact product.

Cantwell, M. 1996. Fresh-cut biology and requirements. In: Fresh-cut Products: Maintaining Quality and Safety; Postharvest Horticulture Series; Postharvest Outreach Program, Department of Pomology, University of California: Davis, CA, Vol. 10, pp 7.2-7.7.


The respiration rates of shredded The respiration rates of shredded lettuce and shredded cabbage lettuce and shredded cabbage are 200 to 300% greater than are 200 to 300% greater than those of the intact heads.those of the intact heads.

Higher respiration rates indicate a Higher respiration rates indicate a more active metabolism and more active metabolism and usually a faster deterioration rate. usually a faster deterioration rate.

In mixed salads, it is important to ensure that components incluIn mixed salads, it is important to ensure that components included for their ded for their color or flavor qualities are as fresh as possible and similar icolor or flavor qualities are as fresh as possible and similar in shelf life to the n shelf life to the

major salad component major salad component

The quality of an entire freshThe quality of an entire fresh--cut item is cut item is only as good as that of its most only as good as that of its most perishable component.perishable component.


The incidence of browning can be The incidence of browning can be reduced by choosing the correct reduced by choosing the correct genotype for given environmental genotype for given environmental conditions.conditions.

A trained panel evaluated the sensory characteristics including A trained panel evaluated the sensory characteristics including leaf surface and edge browning, leaf surface and edge browning, crunchy aspect, freshness, overall visual quality and the rejectcrunchy aspect, freshness, overall visual quality and the rejection or acceptance of the cultivars.ion or acceptance of the cultivars.


Adult leaves:Adult leaves:Blonde oak leavesBlonde oak leavesButter head leavesButter head leavesCosCos lettucelettuceMinicosMinicos lettucelettuceEscaroleEscaroleFriseeFriseeThin Thin friseefriseeIceberg lettuceIceberg lettuceLolloLollo biondabiondaLolloLollo rossarossaRead oak leafRead oak leafWebb lettuceWebb lettuce

Young leaves:Young leaves:Green Green coscos lettucelettuceRed Red coscos lettucelettuceGreen oak leafGreen oak leafLolloLollo rossarossaRed chardRed chardRocketRocketSpinachSpinachThin Thin friseefriseeWatercressWatercressTat Tat soisoi

As an exampleAs an example: selection of different lettuce cultivars for fresh: selection of different lettuce cultivars for fresh--cut based on the shelf life. The purpose was cut based on the shelf life. The purpose was to sort out 60 varieties supplied by local growers cultivated unto sort out 60 varieties supplied by local growers cultivated under the same environmental conditions der the same environmental conditions

harvested between January and May.harvested between January and May.


Shelf life of different cultivars of Iceberg lettuceShelf life of different cultivars of Iceberg lettuce

Within each cultivar, there is a range of genotypic variation inWithin each cultivar, there is a range of genotypic variation in composition, quality and composition, quality and postharvest life potential postharvest life potential



Plant breeders have been successful in selecting:Plant breeders have been successful in selecting:1.1. carrots and tomato cultivars with much higher carotenoids and carrots and tomato cultivars with much higher carotenoids and

vitamin A content vitamin A content 2.2. melon cultivars with higher sugar content and firmer flesh. melon cultivars with higher sugar content and firmer flesh.

Breeding programs are constantly creating new Breeding programs are constantly creating new cultivars with improved qualitycultivars with improved quality

Today special cultivars are grown, especially for theToday special cultivars are grown, especially for thefreshfresh--cut market. cut market.

carrots carrots tomatoes tomatoes melonsmelons

Maturity index = A/B*100

MaturityMaturity

Influence of maturity on browning:Influence of maturity on browning:

Lettuce from the first harvest results in better quality Lettuce from the first harvest results in better quality while mature lettuce browns more after cutting. while mature lettuce browns more after cutting.

B

A

Young leaf tissue have higher respiration rates than mature fullYoung leaf tissue have higher respiration rates than mature fully developed leavesy developed leaves

MaturityMaturity

Respiration rate (Respiration rate (mLmL CO2 CO2 ·· kgkg--1 1 ··hh--1) of leaves of 1) of leaves of kale store at various temperatures for 5 dayskale store at various temperatures for 5 days

42

33

2114SmallSmall leavesleaves

29

57

1288FullFull--sizedsized leavesleaves

1010ººCC 1515ººCC55ººCC00ººCC

Different parts of a vegetable may have very different respiratiDifferent parts of a vegetable may have very different respiration rates, as illustrated by on rates, as illustrated by data from broccoli. data from broccoli.

MaturityMaturity

These differences in respiration rates have implications for These differences in respiration rates have implications for the quality and shelf life of mixed vegetables. the quality and shelf life of mixed vegetables.

The differences in leaf age may yield a mixed product of variablThe differences in leaf age may yield a mixed product of variable perishabilitye perishability

Three different growth stages:Three different growth stages:Stage I: Stage I: ≤≤ 8 cm8 cm,,Stage II: 8Stage II: 8--12 cm12 cmStage III: Stage III: ≥≥ 12 cm12 cm

MaturityMaturity

MaturityMaturity

In both watermelon and tomato, In both watermelon and tomato, lycopenelycopene reaches maximum levels in mature fruit. reaches maximum levels in mature fruit.

Fruit harvested before maturity contain Fruit harvested before maturity contain lower lower lycopenelycopene concentrations, while overconcentrations, while over-- mature fruit also has lower concentrations mature fruit also has lower concentrations due to degradation of the compound.due to degradation of the compound.

For most immatureFor most immature--fruitfruit--vegetables (e.g. cucumbers, summer squash, sweet corn, green vegetables (e.g. cucumbers, summer squash, sweet corn, green beans, and sweet peas) the optimum eating quality is reached befbeans, and sweet peas) the optimum eating quality is reached before full maturity. ore full maturity. In these vegetable, the most frequent problem is delayed harvestIn these vegetable, the most frequent problem is delayed harvest, which results in lower , which results in lower quality at harvest and faster deterioration after harvest.quality at harvest and faster deterioration after harvest.

In peppers, maturity stage was also found to impact on flavonoidIn peppers, maturity stage was also found to impact on flavonoids, carotenoids and s, carotenoids and ascorbic acid concentrations. ascorbic acid concentrations.

Carotenoids were found to increase in mature fruit compared to nCarotenoids were found to increase in mature fruit compared to no detectable levels in o detectable levels in immature, green fruit. immature, green fruit. Vitamin C content also increases substantially in peppers with mVitamin C content also increases substantially in peppers with maturity while flavonoids aturity while flavonoids decrease. decrease.

MarMaríínn, A., , A., FerreresFerreres, F., , F., TomTomááss--BarberBarberáánn, F.A, Gil, M.I. 2004. Characterization and , F.A, Gil, M.I. 2004. Characterization and quantitationquantitation of antioxidant constituents of sweet pepper (Capsicum of antioxidant constituents of sweet pepper (Capsicum annuumannuum L.). L.). J. Agric. J. Agric. Food ChemFood Chem., 52, 3861., 52, 3861--3869.3869.

TurningTurning RedRedGreenGreenImmature greenImmature green

3.2 2.54.020.2FlavonoidsFlavonoids

63.0 93.054.342.3VitaminVitamin CC

9.5 45.64.95.15.1CarotenoidsCarotenoids

MeansMeans in in mgmg/100 g FW/100 g FW

MaturityMaturity

Influence of maturity stage on flavonoids, carotenoids and vitamInfluence of maturity stage on flavonoids, carotenoids and vitamin C of peppersin C of peppers

In other study, some cultivars had higher concentrations of antiIn other study, some cultivars had higher concentrations of antioxidants in mature fruit, oxidants in mature fruit, while some had higher concentrations in immature fruit due to gewhile some had higher concentrations in immature fruit due to genetic variation. netic variation.

MaturityMaturity

Pepper lines which contain equally high levels at both maturity Pepper lines which contain equally high levels at both maturity stages would be ideal for stages would be ideal for commercial producers, since both green and red fruit are used. commercial producers, since both green and red fruit are used.

These examples demonstrate that different beneficial These examples demonstrate that different beneficial phytochemicalsphytochemicals tend to reach optimal tend to reach optimal levels around peak harvest maturity stage for diverse vegetableslevels around peak harvest maturity stage for diverse vegetables. Some flexibility exists for . Some flexibility exists for growers to harvest within a window of opportunity, but it seems growers to harvest within a window of opportunity, but it seems evident that immature and evident that immature and over mature vegetables will contain lower concentrations of someover mature vegetables will contain lower concentrations of some important important phytochemicalsphytochemicals or unacceptable quality. or unacceptable quality.

MaturityMaturity

InsectsInsectsTemperatureTemperature

Responses of plants to oxidative stressesResponses of plants to oxidative stresses

UVUV-- lightlight

ChemicalsChemicalsWater stressWater stress

Accumulation of reactive oxygen species (ROS)Accumulation of reactive oxygen species (ROS)

OO··singlet oxygensinglet oxygen

OO22 −−

superoxidesuperoxideOHOH··

hydroxyl radicalhydroxyl radicalHH22 OO22

hydrogen peroxidehydrogen peroxide

Oxidative stress can cause oxidative damage to proteins, DNA, liOxidative stress can cause oxidative damage to proteins, DNA, lipids..pids..

Environmental factorsEnvironmental factors

The majority of the human healthThe majority of the human health--promoting compounds are associated with plant defense promoting compounds are associated with plant defense against adverse environmental conditions including biotic and against adverse environmental conditions including biotic and abioticabiotic stresses that currently stresses that currently

limit crop yield and quality. limit crop yield and quality.

One of the earliest responses of plants to these stresses is theOne of the earliest responses of plants to these stresses is the accumulation of reactive oxygen species accumulation of reactive oxygen species (ROS)(ROS)

GlutationeGlutationeSuperoxideSuperoxide dismutasedismutase

Antioxidant systemsAntioxidant systems

AscorbateAscorbate

PhytonutrientsPhytonutrientsEnzymesEnzymes

Plants with elevated levels of these antioxidants seem to toleraPlants with elevated levels of these antioxidants seem to tolerate stresses better than those with low levels. te stresses better than those with low levels.


Plants have evolved various antioxidant systems and processes toPlants have evolved various antioxidant systems and processes to scavenge ROSscavenge ROS

Avoid harmful effects of environmental stressAvoid harmful effects of environmental stress

The interaction of genotype and environment often has a profoundThe interaction of genotype and environment often has a profound impact on quality and impact on quality and phytochemicalphytochemical content of vegetables. content of vegetables.


Environmental factors that have a strong influence in relation tEnvironmental factors that have a strong influence in relation to yield and o yield and quality include:quality include:

1.1. temperature, temperature, 2.2. light intensity and light quality, light intensity and light quality, 3.3. altitude, altitude, 4.4. soil pH, soil pH, 5.5. soil type, soil type, 6.6. fertilizers, fertilizers, 7.7. production practices (organic versus conventional, production practices (organic versus conventional,

and field versus green house), and field versus green house), 8.8. irrigation, irrigation, 9.9. rainfall. rainfall.

33-- Low temperatures increase ascorbic acid concentrations Low temperatures increase ascorbic acid concentrations because degradation is reduced.because degradation is reduced.

44-- CarotenoidCarotenoid synthesis is even more temperature dependent synthesis is even more temperature dependent andand crop specific. crop specific.


The influence of temperature on The influence of temperature on phytonutrientsphytonutrients is crop specific.is crop specific.

11-- Most leafy vegetables grown at low temperatures have higher ascMost leafy vegetables grown at low temperatures have higher ascorbic acid orbic acid concentrations than those grown at high temperature (30concentrations than those grown at high temperature (30ººC). C).

22-- An increase or decrease in air temperature of 4An increase or decrease in air temperature of 4ººC, 4 to 5 d before harvest, has the C, 4 to 5 d before harvest, has the greatest impact on postharvest ascorbic acid concentrations.greatest impact on postharvest ascorbic acid concentrations.

Ascorbic acid declines with increasing temperature, while Ascorbic acid declines with increasing temperature, while lycopenelycopene increases from low increases from low to medium temperature, then drastically declines as temperaturesto medium temperature, then drastically declines as temperatures increases from increases from medium to high.medium to high.

Lester, G.E. Environmental regulation of human health nutrients Lester, G.E. Environmental regulation of human health nutrients (ascorbic acid, (ascorbic acid, ββ--carotene, and folic acid) in fruits and vegetables. carotene, and folic acid) in fruits and vegetables. HortScienceHortScience, 2006, 41, 59, 2006, 41, 59--64.64.


Temperature Temperature

A dramatic difference in the synthesis of carotenoids was shown A dramatic difference in the synthesis of carotenoids was shown when carrots were when carrots were exposed to 15, 20 or 25 exposed to 15, 20 or 25 ººC temperatures 2 weeks before harvest. Total carotenoids C temperatures 2 weeks before harvest. Total carotenoids increased with an increase in temperature, but the orange color increased with an increase in temperature, but the orange color decreased.decreased.



Temperature Temperature

Light intensityLight intensity

11-- Reduced light intensity reduces ascorbic acid concentration,Reduced light intensity reduces ascorbic acid concentration,

22-- Reducing light intensity reduces leaf temperature, which is favReducing light intensity reduces leaf temperature, which is favorable orable for for ββ--carotene synthesis,carotene synthesis,

33-- Increased Increased ββ--carotene content increases chlorophyll concentration.carotene content increases chlorophyll concentration.

Light qualityLight quality

11-- UVUV--B radiation decreases both ascorbic acid and B radiation decreases both ascorbic acid and ββ--carotene,carotene,

22-- Red light greatly stimulates Red light greatly stimulates lycopenelycopene synthesis in tomato. synthesis in tomato.

Light intensity and light quality are extremely influential in rLight intensity and light quality are extremely influential in regulating fruit and vegetable egulating fruit and vegetable vitamin and vitamin and phytonutrientphytonutrient contentcontent


Light intensity Light intensity

Mustard greens grown under full sunlight versus 50% sunlight werMustard greens grown under full sunlight versus 50% sunlight were significantly lower in e significantly lower in ascorbic acid concentration, and significantly higher in total cascorbic acid concentration, and significantly higher in total carotene and total chlorophyll arotene and total chlorophyll concentrations.concentrations.



Soil typeSoil type

Sand, loam, clay, and organic matter content have a significant Sand, loam, clay, and organic matter content have a significant effect on the vitamin and effect on the vitamin and

mineral concentrations in vegetables due to higher mineral concemineral concentrations in vegetables due to higher mineral concentration in the more ionic ntration in the more ionic

exchangeable soils.exchangeable soils.

Soil pHSoil pHPlants grown at acid pH levels have low carotene concentrations Plants grown at acid pH levels have low carotene concentrations whereas plant grown at whereas plant grown at alkaline pH levels have low ascorbic acid concentrations.alkaline pH levels have low ascorbic acid concentrations.

Soil mineral contentSoil mineral content

11-- Ascorbic acid decreases with increasing level of N,Ascorbic acid decreases with increasing level of N,

22-- Ascorbic acid increases with increasing levels of P, KAscorbic acid increases with increasing levels of P, K……

33-- ββ--carotene increases with increasing levels of N, K, carotene increases with increasing levels of N, K, ……


The effect of fertilizers on the vitamin content of vegetables iThe effect of fertilizers on the vitamin content of vegetables is less important than the s less important than the effect of genotype and climate conditions, but their influence oeffect of genotype and climate conditions, but their influence on mineral n mineral

composition is more significant.composition is more significant.

FertilizersFertilizers

To date, fertilization recommendations for vegetables have been To date, fertilization recommendations for vegetables have been established primarily for established primarily for productivity goals, not as diagnostics for good flavor quality aproductivity goals, not as diagnostics for good flavor quality and optimal postharvest lifend optimal postharvest life

NitrogenNitrogen is the nutrient with the single greatest effect on quality. is the nutrient with the single greatest effect on quality.

High rates of N fertilization are usually associated with high rHigh rates of N fertilization are usually associated with high rates of vegetative growth, and ates of vegetative growth, and increased leaf protein and pigment contents. increased leaf protein and pigment contents.

Chlorophyll and Chlorophyll and carotenoidcarotenoid concentrations are positively correlated with plant N status. Hconcentrations are positively correlated with plant N status. High N igh N content is often associated with shorter postharvest life due tocontent is often associated with shorter postharvest life due to increased susceptibility to increased susceptibility to mechanical damage, physiological disorders, and decay.mechanical damage, physiological disorders, and decay.

FertilizersFertilizers

CalciumCalcium (Ca) is involved in numerous biochemical and morphological proc(Ca) is involved in numerous biochemical and morphological processes and has been esses and has been implicated in many disorders in the production and postharvest qimplicated in many disorders in the production and postharvest quality of vegetables.uality of vegetables.

tip burn of lettuce is caused by lack of mobility of calcium in tip burn of lettuce is caused by lack of mobility of calcium in the heads during warm weather and the heads during warm weather and rapid growing conditions, there is currently no preharvest contrrapid growing conditions, there is currently no preharvest control practice. Tip burn on lettuce ol practice. Tip burn on lettuce can reduce the quality of the processed product because the cut can reduce the quality of the processed product because the cut defective brown tissue will be defective brown tissue will be distributed throughout the processed product. distributed throughout the processed product.

PotassiumPotassium (K) is a vital element playing an important role in the synthes(K) is a vital element playing an important role in the synthesis and accumulation of is and accumulation of phytochemicalsphytochemicals in plants. in plants.

K seems to improve plant tolerance of various environmental streK seems to improve plant tolerance of various environmental stresses such as drought, low sses such as drought, low temperature or salinity. temperature or salinity.

SulfurSulfur (S) and (S) and seleniumselenium (Se) fertilization influence the (Se) fertilization influence the phytochemicalphytochemical content in content in alliumallium such as such as onions and garlic and crucifers such as broccoli and radish.onions and garlic and crucifers such as broccoli and radish.

Numerous investigations have shown a strong positive correlationNumerous investigations have shown a strong positive correlation between the level of S fertility between the level of S fertility and and organosulfurorganosulfur compounds in onions but it result in increased onion pungency, compounds in onions but it result in increased onion pungency, a negative a negative consumer preference trait.consumer preference trait.


Organic versus mineralOrganic versus mineral

Cultural practicesCultural practices

Limited studies support the popular belief that organic (manure)Limited studies support the popular belief that organic (manure) fertilizer is superior to fertilizer is superior to conventional synthetic (mineral) fertilization in achieving a moconventional synthetic (mineral) fertilization in achieving a more nutritious vegetable.re nutritious vegetable.

Examples of such studies show that cabbage, lettuce and spinach Examples of such studies show that cabbage, lettuce and spinach fertilized with manure fertilized with manure either alone or in combination with the mineral forms of N, P aneither alone or in combination with the mineral forms of N, P and K had significantly higher d K had significantly higher levels of ascorbic acid.levels of ascorbic acid.


There is evidence that the use of plastic mulches can increase pThere is evidence that the use of plastic mulches can increase postharvest losses from ostharvest losses from decay. The impacts of cover cropdecay. The impacts of cover crop--derived mulches on postharvest quality have not derived mulches on postharvest quality have not

been well evaluated for vegetable cropsbeen well evaluated for vegetable crops


Plastic mulchesPlastic mulches

Lower light intensities in the greenhouse lower the synthesis ofLower light intensities in the greenhouse lower the synthesis of glucose, therefore glucose, therefore lowering the synthesis of ascorbic acid,lowering the synthesis of ascorbic acid,

Higher temperatures in the greenhouse lower or inhibit the produHigher temperatures in the greenhouse lower or inhibit the production of ction of ββ--carotene synthesis, especially in cool season plants.carotene synthesis, especially in cool season plants.


Greenhouse Greenhouse vsvs field productionfield production

Greenhouse grown plants, due to the combined effects of higher tGreenhouse grown plants, due to the combined effects of higher temperatures and lower emperatures and lower light intensities, have lower levels of most phytonutrients.light intensities, have lower levels of most phytonutrients.

In a tomato study fruit from all four cultivars had significantlIn a tomato study fruit from all four cultivars had significantly lower ascorbic acid levels y lower ascorbic acid levels when grown in the greenhouse compared to field production.when grown in the greenhouse compared to field production.



A deficiency or excess of water may influence postharvest qualitA deficiency or excess of water may influence postharvest quality. y.

Extreme water stress reduces yield and quality; Extreme water stress reduces yield and quality; Mild water stress reduces crop yield but may improve some qualitMild water stress reduces crop yield but may improve some quality attributes y attributes No water stress increases yield but may reduce postharvest qualiNo water stress increases yield but may reduce postharvest quality.ty.

IrrigationIrrigation

Selecting the proper irrigation system and reducing the number oSelecting the proper irrigation system and reducing the number of irrigations f irrigations applied can help preventing storage lossesapplied can help preventing storage losses

Management of water frequency presents a dilemma between yield aManagement of water frequency presents a dilemma between yield and postharvest quality nd postharvest quality

There is considerable evidence that water stress at the end of tThere is considerable evidence that water stress at the end of the season, which may be he season, which may be achieved by irrigation cut off or deficit irrigation may markedlachieved by irrigation cut off or deficit irrigation may markedly improve the quality of some y improve the quality of some

commodities.commodities.

Irrigation or rainfall effects are due to primarily to a combinaIrrigation or rainfall effects are due to primarily to a combination of light and temperature. tion of light and temperature. Rainy, cloudy, cool conditions decrease ascorbic acid and Rainy, cloudy, cool conditions decrease ascorbic acid and ββ--carotene levels in most produce.carotene levels in most produce.

Furrow irrigated lettuce had more ascorbic acid than lettuce irrFurrow irrigated lettuce had more ascorbic acid than lettuce irrigated by sprinklers, igated by sprinklers, presumably because sprinklers system reduce the light intensity.presumably because sprinklers system reduce the light intensity.

Also, lettuce irrigated by sprinklers had colder leaves, produciAlso, lettuce irrigated by sprinklers had colder leaves, producing 14% less ng 14% less ββ--carotene.carotene.

IrrigationIrrigation

Irrigation and rainfall Irrigation and rainfall

NNot many cultivars have been developed specifically to address geot many cultivars have been developed specifically to address genotype by environment notype by environment interaction effects on quality and postinteraction effects on quality and post--cutting shelf life.cutting shelf life.

The The CICYT CICYT project project (AGL2007(AGL2007--65056)65056) ‘‘Identification of pre and postharvest factors involved Identification of pre and postharvest factors involved en enzymatic browning of freshen enzymatic browning of fresh--cut lettuce and escarolecut lettuce and escarole’’ developed by our group at developed by our group at CEBASCEBAS--CSIC. CSIC.

The main preharvest factors that are studied in the project are:The main preharvest factors that are studied in the project are:

--identification of the influence of environmental conditionsidentification of the influence of environmental conditions-- location of the growing arealocation of the growing area-- fertilizationfertilization-- irrigation: type, frequency and dosesirrigation: type, frequency and doses-- water salinitywater salinity

CicytCicyt projectproject

Replicated trials for several seasons will be collected within aReplicated trials for several seasons will be collected within as short a period as possible from s short a period as possible from the time of harvest, with simulation of commercial handling procthe time of harvest, with simulation of commercial handling procedures.edures.

Basic requirements for preparation of freshBasic requirements for preparation of fresh--cut vegetablescut vegetables

HighHigh--quality raw materialquality raw materialCultivar selectionCultivar selectionSpecific production practicesSpecific production practicesHarvest and storage conditions for freshHarvest and storage conditions for fresh--cutcut

RequirementsRequirements

More emphasis should be placed on flavor and other sensory charaMore emphasis should be placed on flavor and other sensory characteristics as well cteristics as well as on the nutritional qualities of freshas on the nutritional qualities of fresh--cut products. cut products.

Until now, cultivars for fresh market have been evaluated for thUntil now, cultivars for fresh market have been evaluated for their potential usefulness in eir potential usefulness in freshfresh--cut operations. cut operations.

cultivars with low browning potential (lettuce and potato),cultivars with low browning potential (lettuce and potato),cultivars that facilitate harvesting, cleaning, trimming, and ccultivars that facilitate harvesting, cleaning, trimming, and cutting operations, utting operations, cultivars with desirable characteristics of consistently high qcultivars with desirable characteristics of consistently high quality throughout the year. uality throughout the year.

Future trendsFuture trends

But there are specific requirements for freshBut there are specific requirements for fresh--cut cultivars that need to be met: cut cultivars that need to be met:

Documents

II European Short Course QUALITY & INNOVATION OF .... texture, 3. flavor 4. and nutritional quality (sugars, acids, vitamins and phytonutrients). Tissue browning, which can be a major