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Nondestructive Quality Measurement of Horticultural Crops

David Slaughter

Biological & Agricultural Engineering

UC Davis

Additional information available at:

Technologies for Nondestructive Quality Evaluation of Fruits and Vegetables.

Abbott J.A. et al., Horticultural Reviews Vol. 20, 1997.

Quality measurements

Many quality measurement techniques have been developed to mimic the human senses sight, smell, sound, touch and taste

Others are measures of harvest, storage, and handling characteristics that affect quality. Bruise susceptibility

Non-destructive measurements allow 100% sampling Allows sorting into uniform subunits, removal of

substandard items, and identification of premium pieces.

Non-destructive measurements also allow monitoring of quality over time.

Quality measurements

External Properties Size & Shape

Mass, Volume & Density

Appearance, Color &

Visible Blemishes

Composition, Flavor & Aroma

Texture, Firmness, Crispness, Mealiness

Internal Defects, Decay, Insect Damage

Internal PropertiesNon-destructive technologies for fruit and vegetable size determination – a review

G.P. Moreda, J. Ortiz-Cañavate, F.J. García-Ramos, M. Ruiz-Altisent. 2009.

Journal of Food Engineering 92 :119–136

Machine Vision On-line vision systems

examine multiple views of each fruit as they travel on a conveyor. Provide measures of

size shape and volume

4 imagesscanned at eachlocation

size, shape and volume.

External blemishes can be detected with a high degree of reliability.

When combined with fruit weight, the density can be an indicator of internal quality.

Fruit rotates as it travels to expose all sides

Traditionally a Destructive Method

Magness-Taylor Penetrometer

Invented in 1925 Invented in 1925.

Records the Maximum Force Required to Penetrate the Fruit.

Manually Operated.

Penetrometer

Fruit Firmness Methods

Destructive Maximum Force to

Penetrate a Known Distance into Fruit.

ce

FMAX

Measures tissue t th

Deformation

For

c

Non-Destructive Force Required to

“Squeeze” Fruit.

Measure of elastic tissue properties.

strength.

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Durometer Portable instrument used to

determine the ‘Shore A’ hardness of rubber.

Handheld (or stand mounted).

Use 5mm wide ‘E’ tip for peaches or pears.p p

Uses a calibrated spring to measure the resistance to deformation.

Will bruise soft fruit.

$800 - $1200

A durometer consists of:

Principle of Operation

0 percent

40

CalibratedSpring

A calibrated spring,

A tip displacement gage, and

A retractable tip

Pear

0 100

Tip extends2.5 mm

Principle of Operation

0 percent

40

DurometerDisplays

100 percent

40

Pear

0 100 0 100

Pear

Tip extends0.1 inches

A very hard pear can press 100% of the tip into the probe

Principle of Operation

0 percent

40 40

40 percent100 percent

40

Pear

0 100

Pear

0 1000 100

Pear

A softer pear can only press the tip partially into the probe

Bartlett Pear

y = 0.5525x - 2.5

r2 = 0.77

40

45

50

55

ss (

Sin

clai

r) R2 = 0.77

Durometer measurement of Bartlett Pears

20

25

30

35

40 50 60 70 80 90 100

'E' Durometer (%)

Imp

act

Fir

mn

es

Durometer measurement of Bartlett Pears

80

90

100

Sco

re

logarithmic regression using all data:y = 14.174Ln(x) + 47.45, R2 = 0.9028

40

50

60

70

0 5 10 15 20 25

Penetrometer Firmness (lbs)

linear regression using penetrometer firmness > 10lbs:y=0.99(x) + 70.7, R2=0.50

Du

rom

eter

S

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Low-mass impact methods are widely available for measuring firmness on-line. Spherical tip gently taps the fruit

Accelerometer on impacting arm senses tissue elasticity

Principle of Operation

A

Firmness Index

t

A

PeaktoTime

onAcceleratiPeakC

t

Principle of Operation

AFirmness Index

AonAcceleratiPeakC

t

A

t

tPeaktoTimeC

Monitoring Impact FirmnessDuring Ripening of Mango

ratio

n

CDay1=275

Source: I. ShmulevichSource: I. Shmulevich

time

acce

le

CDay7=65

UC Davis handheld nondestructive firmness sensor for orchard use.

Sinclair Nondestructive firmness tester. “Gently” taps the fruit and provides a Sinclair iQ firmness

value.

OnlineModel

Bench Top model

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Clingstone Peaches

Comparison of Penetrometer Firmness vs Impact Firmness

R2 = 0.6

Acoustic Firmness Measurement Aweta/Autoline on-line acoustic firmness sensor

“Gently” taps fruit and “listens” with a microphone.

Uses Fourier analysis to determine the natural frequency of the fruit.

Firmness = f2 * m2/3

Bench top

On-line model

Bench top model

Acoustic Firmness Principle

Natural frequency and firmness Acoustic Firmness =f2 m2/3

where :f - first resonant frequencyq y

m - fruit’s mass.

Acoustic Firmness sensor

10000

3

22 mf

S

Acoustic Firmness sensor

Good

Acoustic impact can also detect internal cavities in melons.

Hollow

B. Diezma-Iglesias, M. Ruiz-Altisent, & P. Barreiro. 2004

NondestructiveOn-line Firmness sensor

AWETA online firmness sensor Acoustic & Impact

sensors

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Impact vs. Acoustic Firmness

Acoustic Method Global

Measurement Resonance of

Impact Method Local spot

measurement Elastic properties of

fwhole fruit is measured.

Some internal defects can be sensed

Works better on firm fruit

exterior flesh is measured.

Cannot sense internal defects

Works better on soft fruit

Automatic Fruit QualityGrading in Cherry

Stem Width

FirmnessFruit WidthColor

Pulp Temperature

Optical Firmness Principle

Researchers are attempting to develop light scattering models to predict firmness.

Yankun Peng, Renfu Lu. 2007. Journal of Food Engineering 82:142–152

Volatile Sensing

Electronic nose 32 co-polymer sensors

Classify volatiles using artificial neural network.

Detecting freeze damage in oranges

32 co-polymer sensors

Headspace Ethanol measurement for Freeze Damage Oranges are placed in one quart plastic bags.

Ethanol predicts freeze damage with 80% to 90% accuracy in 7 fruit batches.

Slightly damaged (<15%) fruit are not detected.

• VolatilesVolatiles accumulate for 1/2 hr at room temp. (Not suited for on-line use.)

• $800 Etoh

Sensor.

Electromagnetic Spectrum

X-RAY

ULTRA-VIOLET

INFRAREDRADIOWAVE

MICROWAVE

FREQUENCY (Hz)NIR

VISIBLE

108 109 1010 1011 1012 1013 1014 1015 1016 1017

1010 109 108 107 106 105 104 103 102 10 1

WAVELENGTH (nm)

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Material/Light Interactions

Light interacts with produce in 3 ways: Reflectance, Transmittance, and Absorption

L*, a*, b* color system Color can be used in

many crops as an index of maturity or ripeness.

Instruments to measure the peel color of fruits and vegetables are gavailable from several manufacturers.

L* represents luminous intensity

a* represents the red - green content

b* represents the blue - yellow content

a* b* Chromaticity Diagram

a*= red to green axis

b*= yellow to blue axis

Hue = name of color (e.g., yellow, green)

Measured in degrees Measured in degrees

Clingstone Peach Maturity

45

90

80

Gardner ‘a’ value or CIE hue angle have been demonstrated to be good indices of clingstone peach maturity.

Peaches with a flesh

CIE hue angle

0

270

180

Peaches with a flesh hue angle below 80 degrees are mature

Infrared Spectroscopy

All organic and inorganic molecules, except homonuclear molecules (e.g., O2), absorb light in the infrared region.

The light absorptions in the infrared typically cause vibrations in a molecule.

C = LOG10[1 / T]L

• Beer-Lambert Law

SymmeticStretch

In-planeScissoring

• Allows optical measurements of chemical constituents in the sample.

Absorbance Spectra Below is a picture of a cup of water

What color would the water appear in the infrared?

Black

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Absorbance Spectra NIR Applications in Food

Moisture Grains, Forages, Fruits,

Meat, Milk, Cheese, Seeds, Soil.

Protein Grains, Forages, Meat,

S d

Carbohydrates Grains, Breakfast

Cereals, Seeds.

Starch Grains, Seeds, Kiwifruit.

FiberSeeds.

Soil Nitrogen Ethanol Beer, Wine.

Fat Oil seeds, Milk, Meat,

Cheese, Snack Foods, Human Triceps.

Grains, Forages.

Amino Acids Grains

Defects Bruising, Contaminants.

On-line Near Infrared (NIR) Measurements

High light source power (150 - 300 Watts) allows transmission measurement of intact citrus in the NIR. NIR On-line

Sugar sensor

Miller & Zude−Sasse (2004)

NIR on-line testred grapefruit (20 oC)

On-line NIR Evaluation Study

Miller & Zude−Sasse (2004) Evaluated on-line NIR SSC sorter (Mitsui Qscope) 5.5 fruit/second belt speed Red & white grapefruit were studied

Results: Fruit temperature during sorting must match

temperature during calibration. Measurements on smaller fruit were more accurate

than on larger fruit.

Brix Sorting Test Results (2 categories)

Classification accuracy: 79% (76% - 100%)

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NIR Applications Recently some

commercial, handheld NIR instruments have become available.

Experience at UC Davis: “closed” type instruments are

calibrated at the factory andcalibrated at the factory, and the calibration has not performed well in California.

Good success obtained with “open” type instruments, which allow on-site calibration. NIRVANA

SACMI

Nondestructive measurement of fruit and vegetable quality by means of NIR spectroscopy: A reviewPostharvest Biology and Technology 46 (2007) 99–118Nicolai, B.M, K. Beullens, E. Bobelyn, A. Peirs, W. Saeys, K.I. Theron, J. Lammertyn

New commercial handheld instruments have been recently developed for measurement of i l li h

Handheld Instrument for Nondestructive Determination of Internal Quality

internal quality parameters such as oBrix.

• One instrument, called the NIRVana, shows particular promise because it is an “open” instrument, which allows model optimization for local cultivars and production practices.

Identification of Immature Green Tomatoes at the Time of Harvest

Immature

Tomato Spectrum

Results

Results show that the handheld instrument can correctly identify 70% of immature tomatoes.

Measurement of Fresh Fruit Spectrum using ‘Nirvana’ Spectrometer

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Peach Spectrum (Flesh Color)Results

Measurement of Soluble Solids in Peaches

Measurement of Flesh Color in Peaches

Results

External Validation of Developed Spectral Model with ‘Loadel’ Peach Variety

Results

Measurement of Internal Quality (Soluble Solids) of Mandarins

Measurement of Internal Quality (BrimA score) of Mandarins

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Fluorescence Some molecules can

re-release absorbed optical energy as a lower energy photon.

http://probes.invitrogen.com

(vibration or heat)

Example: Using citrus peel oil fluorescence to determine fruit quality

Tangeretin a nonvolatile, neutral flavone.

fluoresces an orange color under long wave UV (S ift 1967)wave UV (Swift, 1967).

High levels in peel oil of orange, grapefruit and some tangerines, low levels in lemon (Manthey & Grohmann, 2001).

Events that cause peel oil release can be detected using UV fluorescence.

Peel Oil under Blacklight

grapefruitlemon

grapefruitlemon

lime

orange

lime

orange

tangerine

Viewed under blacklight

tangerine

Low level off d

Freeze Damaged Oranges Fluoresce

Relationship to flesh damage Varies with both freezing &

thawing conditions.

freeze damage

Moderate to severe freeze

damage

• Agreement between the USDA and UV methods ranged from 35% to 85% in lab. and field studies in 2006 & 2007

Thrip Damage

Thrip damage is also visible under blacklight

Fluorescence due to extensive thrip damage Blasco et al. (2007)

Appearance of decay lesions under UV light

Note that the infected lemon does not fluoresce

Smilanick, 2008

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75

50

Initial

After 3 weeks

%

Quality (% choice or higher) of navel oranges Initially and After 3 weeks storage at 60F

0 2 31

25

0

%

Fluorescence classNONE VERY HIGH

GoodFruit

Smilanick2008

Grove Inspection using UV flashlights

Fecal Contamination Fluorescence

Fruit surfaces contaminated with fecal matter can be detected with UV fluorescence.

Dilute fecal matter was applied in a grid pattern

Fluorescence Images

Moon S. Kim, Alan M. Lefcourt, Yud-Ren Chen, Yang Tao. 2005

Nuclear Magnetic Resonance (NMR)

Hydrogen atoms in a biological material act like magnetic dipoles

N

Proton

MagneticDipole

Hydrogen

magnetic dipoles due to the rotation of the electron around the proton. S

Electron

Nuclear Magnetic Resonance (NMR)

Under normal conditions the magnetic dipoles point in random directions.

Nuclear Magnetic Resonance (NMR)

The material is placed inside a powerful electro-electro-magnet.

This causes the dipoles to align with the magnetic field.

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Nuclear Magnetic Resonance (NMR)

A radio frequency (RF) pulse is then used to “knock” the atoms out of alignment.

Nuclear Magnetic Resonance

When the RF pulse stops, the atoms spiral back into alignment with the magnetic field.

The time it takes for realignment is called gthe relaxation time (usually within milliseconds).

The realignment process creates its own radio frequency signal that is detected by the system.

NMR measurement of Avocado Quality

NMR - Data Analysis

NMR - Example Applications

Seed/pit detection

Worm damage

Bruises

Water core

Magnetic Resonant Image of Partially

Frozen Orange

Freeze damage

Freeze Damaged Tissue

Healthy Tissue

Portable MR System

Magnet

Permanent magnet NMR sensor(Quantum Magnetics Corporation, San Diego,CA)

ElectronicsFruit

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Behavior of non-metallic materials when placed inside an alternating electric field. Moisture of dates and other “dry” fruits or nuts.

Dielectric measurements

Metal Plate + Positive Charge +

Before Energizing

Metal Plate

Dielectric Material

- Negative Charge -

+ +

-

+ +

-

+ +

-

+ +

-

+ +

-

+ +

-

After Energizing

Dielectric Moisture Meter

Empty Walnut Drying Bin Bin Sides are a Capacitor with Walnuts as the Dielectric Material

X-Ray & Gamma-Ray

Maturity of lettuce heads

Defect detection Freeze damage in citrus -

online

Olive, showing fruit fly entrance hole

Split pits in peach

Hollow heart in potato -online

Bruises in apple

X-ray image showing tunnels.

R. Haff