1

Examples of products

Physiology of fresh-cut products

Preparation and handling

Quality aspects of fresh-cut products

Fresh-cut Products: Overview and Challenges

Marita Cantwellmicantwell@ucdavis.eduhttp://postharvest.ucdavis.edu

"Fresh-cut produce" is defined as any fresh fruit or vegetable or any combination thereof that has been physically altered from its original form, but remains in a fresh state. Regardless of commodity, it has been trimmed, peeled, washed and cut into 100% usable product that is subsequently bagged or prepackaged to offer consumers high nutrition, convenience and value while still maintaining freshness.

Fresh-cut Produce

• Minimally Processed

• Lightly Processed

• Partially Processed

• Preprepared

• Fresh Processed

• Pre-cut

• Value-added

IFPA/UFPA

Source: The Perishables Group -

The FreshFacts on Fresh Cut, 2006

Fresh-cut Produce Sales via Supermarket Channels,* 2005,

$6 Billion Total

Packaged salads

53%Veggies* 26%

Fruit 21%

Carrots=50% of vegetables

*Data for 59.2% of grocery ACV, projectedto total grocery over $2 million/store channel.

Fresh-cut Products References (Summaries on Specific Products)

• FRESH-CUT FRUITS (J. Beaulieu, J. Gorny)

• FRESH-CUT VEGETABLES (M.Barth, H. Zhuang, M. Saltveit)

USDA Agric. Handbook 66. 2004. Commercial Storage of Fruits, Vegetables & Ornamentals (K.Gross et al., eds.); http://www.ba.ars.usda.gov/hb66

• FRESH-CUT FRUITS AND VEGETABLES (M. Cantwell &T. Suslow). 2002. Postharvest Technology of Horticultural Crops, Ch. 36.

The Magazine for Value-Added Producehttp://www.freshcut.com/

International Fresh-cut Produce AssociationTechnical publications on food safety, packaging;technical seminars, annual conference & expo

UNITED FRESH PRODUCE ASSOCIATIONhttp://www.unitedfresh.org/

2006

FreshFresh--cut Vegetablescut Vegetables• Lettuces: cleaned, chopped, shredded• Spinach, leafy greens, washed & trimmed • Broccoli & cauliflower florets• Cabbage, shredded • Carrots, baby, sticks, shredded• Celery sticks• Onions, whole peeled, slices, diced• Potatoes & other roots: peeled, sliced, diced• Mushrooms sliced• Jicama, Squash, cucumber slices, dices• Garlic, fresh peeled, slices

2

Romaine; Caesar Salad

European style salads

Differentiation ofPrepared Salads; Salad Meals

Standard iceberg Plus “color”

Differentiation of Salads; Salad Meals

Standard iceberg Plus “color”About 1996

Salad kits, 2006

CARROT CHIPS™

CARROT DIPPERS™

CARROT SNACKSTM

for Horses!

http://www.grimmway.com

Food ServicePresentations

Sweetpotato for Food service

Strips taro, celeriac, sweetpotato

•Fresh Garlic •Whole Peeled Garlic Cloves •Roasted Garlic Cloves •Garlic Braids •Elephant Garlic •Jarred Garlic Products •Fresh Chopped Garlic •Chopped & Minced Garlic in Water

Resealable bags

Single serveSnack packs

Rigid containersand bowls

Biobased packagingPLA resin

Active packaging Intelligent/SmartPackaging

IFPA, 2004. Fresh-cut Produce Fuels an America on the go. 58 pp.

3

Immediate Physical Effects

Mechanical shock to tissueBruises, cracks, fractures in tissue

Removal of protective epidermal layerAlter gas diffusionProvide entry for contaminants

Cell fluids on cut surface Reduced gas diffusionProvides substrate for microbes

Exposure to contaminantsMicrobial ,Chemical

Abrasion peeling of carrots leads to fragmented cell walls that dry out and result in “white blush”;can rehydrate carrots.

Diagrams from Saltveit, UC Davis

New equipmentautomatically peelsand then cuts the carrots;have less problem with“white blush”

Physiological Effects of Fresh-cut Processing

• Increased respiration rates

• Altered ethylene production rates

• Increases in other biochemical reactions– Discoloration and Color

– Texture

– Aroma and Flavor

– Nutritional quality

Main strategy to minimize changes in physiology is low temperature

Respiration rates of Intact and Shredded Lettuce

Res

pira

tion

(µ

l CO

2. g

-1 h

-1)

0

5

10

15

20

Days storage

0 1 2 3 4 5 6 7 8 9

Res

pira

tion

(µ

l CO

2. g

-1 h

-1)

0

5

10

15

20

Shredded Lettuce

Intact Lettuce2.5°C (36°F)

5°C (41°F)

7.5°C (45°F)

10°C (50°F)

Shredding greatly increased respiration rates Temperature control is

extremely important

• Low temperature minimizes wound response

• Diced onions discolor, decay, soften and lose fluid more readily than whole peeled onions

Storage Temperature

Res

pir

atio

n

(µL

CO

2. g

-1 h

-1)

0

1

2

3

4

5

6

7

8

9

10

11

12 Yellow Onion

Intact

Peeled

Diced

0°C 5°C 10°C

Average Respiration Rates (µL CO2/g-h)

40.629.318.110°C

21.217.410.65°C

Compressed Compressed Air PeeledAir Peeled

Manually Manually PeeledPeeled

Unpeeled Unpeeled ClovesCloves 0

10

20

30

40

50

Days0 2 4 6 8 10 12 14 16 18 20

Re

spir

atio

n (

l CO

2/g-h

)

0

10

20

30

40

50

5ºC (41°F)

Unpeeled Manually peeled Compressed air peeled

10ºC (50°F)

Res

pira

tion

(l C

O2/g

-h)

Careful peeling causes a substantial increase in respiration rates. Mechanical compressed air peeling doubles rates. Rates are significantly less at 5°C. Quality best maintained at 0°C.

0°C

Commercially Peeled Garlic Stored 9 Days

5°C 10°C 15°C

4

Intact and Intact and FreshFresh--cut Kalecut Kale

Respiration rate (mL CO2 kg-1 h-1 )

Product 0ºC 5ºC 10ºC 15ºC

Full size leaves 8 12 29 33

Small leaves 14 21 42 57

Chopped (2 x 2 cm pieces full size leaves)

15 23 46 53

Shredded (0.3 cm pieces full size leaves)

17 28 59 68

Harvest Trim, core, defect removal Cool and/or MA Dump, mechanical cut Cooling, disinfection Drying, centrifugation Component blendingWeigh and package Metal detector, pack, palletize Temporary cold storage

Lettuce Salad Preparation

1. Harvest lettuce from first harvest results in better quality

trim outer leaves

2. Field-pack & local transport plastic bins or totes/ carton boxes or bins; avoid wood bins

transport on flatbed trucks; if distances far, transport in refrigerated trailer

3. Vacuum or forced-air cooling field temperatures and delay determine need to cool

vacuum and forced-air cooling most common

4. Reception, dump, trim and core revision and selection of heads on conveyer

further trimming outer leaves; removal of stem tissue with coring device

Preparation of Lettuce Salads

Often Done in the field

Preparation of Lettuce Salads, cont.

5. Chop/shred/tear continuous-feed cutter for salad pieces (3 x 3 cm) or shreds (<0.5 cm)

manual cutting for some lettuce types (romaine) very sharp knives reduce damage and subsequent browning

6. Wash and Cool Cold water containing disinfectant, usually chlorine

residence time form 15-30 sec; may use processing aides to reduce browning

7. Centrifugation or other drying technique vibration screens remove large volumes of water

centrifugation and air tunnels remove moisture so surface of product dry basket centrifuges of different sizes depending on product

8. Combine different products for salad mixes or “color” items may be added after washing and centrifuged together

In facility at low temperature 3-5°C

Preparation of Lettuce Salads, cont.

9. Package in plastic film bags centrifuged product dumped onto conveyor feeding filler

manual or automated form-fill-seal machines vacuum or gas-flushing with nitrogen

check for leakers in pressurized water chamber

10. Box, palletize and store temporarily Bags through a metal detector, conveyor to boxing and palletizing area

Temporary storage <5ºC (<41ºF); 0°C (32°F) is optimum

11. Transport to food service outlets and/or retail markets Pre-cooled clean trucks; thermostat at <5°C (41°F) Load at enclosed docks to maintain cold chain

5

Washing Disinfecting Rapid cooling Cut to 2 inch sections Mechanical Peeling Mechanical shaping Disinfection Cooling Computerized quality and color sorting Packaging (form, fill, seal)

Processing Baby Peeled Carrots

Onion ProcessingRaw material qualityPackaging and odorsPhysical damageTemperature control

Many large volume (lettuces) products are mechanically cut, but manual preparation generally results in superior quality

cutting romaine by hand; eliminate defects manually peeled garlic vs compressed air peeled broccoli and cauliflower florets manually trimmed manually trimmed and cut melons, pineapples

SANITARY PLANT DESIGNFocus: Implementation of GMP’s

Rudi Groppe; http://www.heinzen.com/products/

Design efficient, easy to clean & sanitize processing plants

Mobility of equipment 2-3 areas to separate production steps

Total Microorganisms at Different Steps Total Microorganisms at Different Steps of a Freshof a Fresh--cut Salad Process Linecut Salad Process Line

Bin Dump 92,000

Coring Belt 210

Cutter 2,290

Transfer Belt 40

Cooling Water 5

Centrifuge 10

Package Filler 3,350

Operation Number/Sq. Inch

Modified from Hurst, Univ. Georgia, 1990

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Fresh-cut Products

Food Safety Requirements

•• Meticulous cleanliness of equipment, Meticulous cleanliness of equipment, employees and productemployees and product

•• Rigid maintenance of refrigerated Rigid maintenance of refrigerated temperaturestemperatures

•• Complete integrity of packagesComplete integrity of packages

•• Strict adherence to product use by dates Strict adherence to product use by dates & handling instructions& handling instructions

“Best if used” by datesUSDA Inspection guidelines but no standards

Wounds induce Wounds induce phenolicphenolic metabolismmetabolismLeading to unsightly brown pigmentsLeading to unsightly brown pigments Enzymatic Browning

PALPhenylalanine cinnaminc acid other phenolics

PPO+ O2 (o-Diphenol oxidase)

(Laccase)

complex brown polymers quinones

PAL = phenylalanine ammonia-lyasePPO = polyphenol oxidase

5

4

3

2

1

Salad Lettuce Cut edge browningWound induction of PAL

and brown pigments Lettuce types and varieties

differ in PAL and browning

Days at 5°C (41°F)

0 1 2 3 4 5 6 7

PA

L

acti

vit

y (

µm

ol c

inn

am

ic a

cid

. g-1

. h-1

)

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0Green LeafRed LeafButterhead

IcebergRomaine

5% LSD

Days at 5°C (41°F)

1 2 3 4 5 6 7 8

Res

pira

tion

rate

(µ

L/g-

h)

0

3

6

9

12

15

18

21 A. Intact leavesHeart Young Midsize Full size

Days at 5°C (41°F)

1 2 3 4 5 6 7 8

B. Salad-cut leaves (2 x 2 cm)

Romaine lettuce: leaf position/age effect on respiration, discoloration and composition

Phenolics highest in outer leaves; browning highest in outer leaves Sugars highest in heart leaves Chlorophyll/carotenoids highest in outer leaves Vitamin C not much affected by leaf age or position

Ermen, Hong, Cantwell, 2006

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Control

1-MCP

Air CAcv Pic

Nov 2004, 1000ppb 1-MCP at 5°C; 8hr after harvest, CA=1%O2+9%CO2

4 days 5°C

Prevention of enzymatic/oxidative browning

• Refrigeration (slows enzymatic reactions)

• Exclusion of oxygen (CA, MAP, edible films)

• Inhibition of PAL (lettuces & vegs)

• Inhibition of PPO (fruits)

• Use of reducing agents (ascorbic acid, etc.)

• Other chemical agents

Packaged Salad Quality Study

• 4 salad products from 5 processors• 4 production dates, product purchased• Products stored at 5°C (41°F)• Components: Size, Color

• Visual Quality and defects: 0, 10, 15 & 20d

• Composition: Sugar, Vit C, EtOH, Acetald.

• Gas Analyses: O2, CO2, C2H4,every 5 days

• Microbiological Tests: APC, Coliforms (0, 10, 20d)

• Sensory: 18 panelists, 5 criteria (texture, aroma, flavor, visual, Buy), 0 & 10D

Flavor quality good to 10 days; shelf-life expected 14-16 days

%

0.00

0.05

0.10

0.15

0.20

Days

0 4 8 12 16 20 24

%

0

5

10

15

20

25

mm

ol/k

g

0.0

0.5

1.0

1.5

2.0

Days

0 4 8 12 16 20 24

mm

ol/k

g

0

10

20

30

40

50

60

Sco

re (

9=

exc

elle

nt)

1

2

3

4

5

6

7

8

9

Days

0 4 8 12 16 20 24

Sco

re (

5=

seve

re)

0

1

2

3

4

5

Oxygen

Carbon Dioxide Ethanol

Acetaldehyde Visual Quality

Off-Odors

Temperature Effects on Salad Products

0ºC10ºC

20ºC

Peiser & Cantwell

Total Vitamin C (AA+DHA)

Days

0 3 6 9 12 15

Tot

al V

it. C

(m

g/1

00g

fwt.

)

0

10

20

30

40

air

1% O2 + 10% CO2

air + 10% CO2

1% O2

Ascorbic acid (AA)

Days

0 3 6 9 12 15

Dehydroascorbic acid (DHAA)

Days

0 3 6 9 12 15

LSD = 4.2

Romaine Salad-cut lettuce Vitamin C content and modified atmospheres

H. Ermen, G. Hong, M. Cantwell 2006

High CO2 atmospheres result in decreased Vitamin CHigh CO2 also reduces crispiness of lettuce

Lettuce AlternativesIntact Baby sizeClean Whole leavesHearts

Rely on temperatureNo modified atmospheres

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There are many opportunities There are many opportunities for damage to spinach leaves for damage to spinach leaves HarvestHarvest Bin dump, sort areaBin dump, sort area Wash and centrifugeWash and centrifuge Packing Packing

Information courtesy of Dr. G.S. Mudahar, Salad Time Farms, Inc.

3

4

5

6

7

0 2 3 4 5 6 7 8 9 10Days

Te

mp

erat

ure

(°C

)

1

At plant

Retail Store Cooler

Retail Shelf

DistanceTransport

LocalDistribution

Fresh-cut produce Chill Chain Temperatures During Shipping, Distribution and Retail Display.

We can do better!!

Good Temperature Control throughout handling and distribution is a Necessity for Fresh-cut Products

9

Vegetable trays- want 18 day shelf-life

Products in tray and compatibility issues- raw material sourcing and handling before prepare - shelf-life of individual products in tray varies- temperature; 5°C too low for grape tomatoes- modified atmospheres—not good for all products in tray

FRUITSFRUITS

DaysVEGETABLESVEGETABLES

10-14Broccoli & cauliflower florets, shredded cabbage, lettuce and broccoli, celery & carrot sticks

4-9Pepper and tomato dices, cucumber slices, squash slices, mushroom slices, jicama sticks

>21Baby carrots, peeled onions, peeled garlic

2-9Strawberry slices, melon & mango cubes, citrus segments, peach & pear wedges, grape berries

10-14Apple wedges, pineapple chunks, pomegranate arils, kiwi slices

14-18Lettuce salads, lettuce separated leaves, lettuce mixes, spinach leaves, peeled potatoes

Potential post-cutting storage life at 2-5ºC (36-41ºF)

Products

Baby Carrots and Variety Selection

• Uniform, bright orange color

• Small or no core

• High sugars with no harshness/bitterness

• Smooth exterior to minimize peeling loss

• No green should or green core problems

• Strong tops for mechanical harvest

• Balance between juicy texture and resistance to shatter

Diced tomato: Example of variation in appearance of 5 cultivars

Fresh-cut tomato for food service

Stage of maturity/ripeness for cuttingColorTexture; slice integrityComposition-flavor

Brassicas have higher respiration rates than lettuces.Freshness of color and flavor ingredients.

High Quality Raw Material is Necessary

for High Quality Fresh-cut Product

10

Preprocessing StorageExample: Lettuce heads stored at 5°C (41°F)Longer heads are stored, greater browning on cut salad pieces

Days after processing

1=no

ne,

5=

seve

re

1

2

3

4

5

Days stored before processing

Days after processing

0

7

14

IcebergLettuce

Browning of Cut Edges

RomaineLettuce

4 8 12 4 8 12

Meal SolutionsProtein componentStarch component

Current Fresh-cut Challenges

Fresh-cut FruitsApplesMelonsPineappleCitrus

12% 1%2%

2%3%

3%

48%

9%8%

14%

ApplesOther MelonsWatermelonHoneydewsCitrusTropicalsPineappleCantaloupeMixedOtherSource: The Perishables Group

Supermarket Mix of Value-Added Fresh Fruit: Quantity Sold, 2004

64,000,000 Pounds64,000,000 Pounds

29,000,000 Kg29,000,000 Kg

1.5 Million/19Kg Boxes1.5 Million/19Kg Boxes

1.5% USA Apple 1.5% USA Apple SupplySupply

13,500 13,500 McDMcDRestaurantsRestaurants

FreshFresh--Cut Cut Apples

From Jim Gorny

Commercial Pomegranate Aril Extraction and Packaging

From Adel Kader

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Ripeness Stage

& Storage Temperature

Effects

Shelf-life

Enzymatic Browning

PALPhenylalanine cinnaminc acid other phenolics

PPO+ O2 (o-Diphenol oxidase)

(Laccase)

complex brown polymers quinones

PAL = phenylalanine ammonia-lyasePPO = polyphenol oxidase

Genotypic Differences in Browning Potential of Apples Challenges for Fresh-cut Melon products

• Maturity: sugars vs firmness

• Taste-life vs Shelf-life

• Color

• Texture

• Flavor

31.732.232.4Color (chroma) (0.7)

7.910.511.5Soluble Solids (%) (0.6)

6.39.310.7Firmness (N)* (LSD=0.3)

SunburnGround Spot

Good QualityParameter

Sunburn

Ground Spot

Good QualityMelon Defects

andInternal Quality

* 5 mm diameter probe

12

0°C 5°C 10°C 12d

10 days

7.5°C (45°F)

5°C (41°F)

2.5°C (36°F)

Relative Importance of Temperature and Modified Atmospheres for Fresh-cut melon

Air 1% O2 Air +10% CO2

1% O2 +10% CO2

Vis

ual

Qu

alit

y

1

2

3

4

5

6

7

8

9

Days

0 5 10 15

Off

-od

ors

1

2

3

4

5

Days

0 5 10 15

Air CA

Air CA

0°C 32°F2.5° 36°5° 41°7.5° 45°10° 50°

Fresh-cut Cantaloupe: Temperature and Atmosphere

CA 3%O2 +10%CO2 Cantwell, unpublished

Translucency not reduce firmnessCalcium chloride dips reduce translucency

10C (50F)

5C (41F)

Experimentally InducedTranslucency

BL=blunt blade SH = sharp blade

Translucency Defect• Differences among melon cultivars• Probably growing & nutrient conditions affect

A) Increased Technical & Managerial A) Increased Technical & Managerial SophisticationSophistication

B) Understand & Manage Fruit B) Understand & Manage Fruit Ripening Ripening

C) Overcome Sourcing IssuesC) Overcome Sourcing Issues

D) Reduce Labor CostsD) Reduce Labor Costs

E) Retain Flavor and AromaE) Retain Flavor and Aroma

The Successful FreshThe Successful Fresh--cut Fruit Processorcut Fruit Processor

Management of Ripening of Intact and Fresh-cut Fruits - Considerations

1. Stages of fruit developmentStages of fruit development

2.2. Fruits that must ripen on the plantFruits that must ripen on the plant

3.3. Fruits that can ripen on or off the Fruits that can ripen on or off the plantplant

4.4. Role of ethylene in fruit ripeningRole of ethylene in fruit ripening

5.5. Efficacy of 1Efficacy of 1--methylcyclopropene in methylcyclopropene in extending shelfextending shelf--life of freshlife of fresh--cut fruitscut fruits

13

Cut ripe pineapple cubes have a longer post-cutting life than those cut green

Adel Kader

Classification of fresh-cut fruit products according to their potential post-cutting-life at optimum handling conditions (0-5ºC and 90-95% RH)

Banana slices, citrus segments, grape berries, melon cubes, nectarine and peachwedges, papaya cubes, pear wedges, persimmon slices, strawberry slices

2-9 days

Apple wedges, kiwifruit slices, mango cubes, pineapple slices and wedges, pomegranate arils

10-14 days

Fresh-cut fruit productsPotential

storage-life

Fresh-cut FruitRoadblocks to Success

• Labor Intensive Production

• High Cost per pound-yields and price

• Fruit availability– Offshore

– Stage of ripeness

• Perishability of cut product

Adapted from Jim Gorny

A)A) Modes of Failure: Modes of Failure:

Browning, Softening, Microbes Browning, Softening, Microbes

B) CultivarB) Cultivar

C) Maturity at CuttingC) Maturity at Cutting

D) Storage HistoryD) Storage History

ShelfShelf--life Driverslife Drivers

Maintain Quality & Shelf-life of Fresh-cut

Vegetable Products Use highest quality raw material

Minimize mechanical damage; sharp knives

Rinse cut surfaces; remove excess water

Maintain strict sanitation; chlorinated water

Use appropriate package and atmosphere

Maintain product temperature at 1-2°C

Fresh-cut ProductsOpportunities and Challenges

• Packaging; MAP

• Nutritional Quality

• Sensory Quality

• Microbial Food Safety

• Temperature Control

• Raw Material Quality