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Nondestructive Quality Measurement of Horticultural Crops

David Slaughter

Biological & Agricultural Engineering

UC Davis

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Nondestructive Measurements Reference List Abbott J.A. et al., Technologies for nondestructive quality evaluation of fruits

and vegetables. Chapter 1 in Hort. Reviews Vol. 20, 1997.

Butz P., et al. Recent developments in noninvasive techniques for fresh fruit and vegetable internal quality analysis. J. Food. Sci. 70(9):R131-R141, 2005.

García-Ramos et al. Non-destructive fruit firmness sensors: a review. Spanish J. of Ag. Res. 3(1):61-73, 2005.

Harker, F.R. et al. Texture of fresh fruit. Chapter 2 in Hort. Reviews Vol. 20, 1997.

Nicolai B. et al. Nondestructive measurement of fruit and vegetable quality by means of NIR spectroscopy: A review. Postharv. Bio. & Tech. 46:99–118, 2007.

Ruiz-Altisent M. et al. Sensors for product characterization and quality of specialty crops. A review. Computers and Electronics in Ag. 74:176–194, 2010.

Slaughter & Abbott. Applications in analysis of fruits and vegetables. Chapter 14 in Near-Infrared Spectroscopy in Agriculture, Agronomy Monograph no. 44., 377-398, 2004.

Vanolia & Buccheri. Overview of the methods for assessing harvest maturity. Stewart Postharvest Review, 8(1):1-11, June 2012.

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Produce 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 quality assessment of all (100% sampling) items. This allows sorting into uniform subunits, removal of

substandard items, and identification of premium pieces.

Non-destructive measurements also allow monitoring of quality over time. 3

Produce 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 4

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.

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

4 imagesscanned at eachlocation

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Traditionally a Destructive Method

Magness-Taylor Penetrometer

Invented in 1925.

Records the Maximum Force Required to Penetrate the Fruit.

Manually Operated.

Penetrometer 6

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Fruit Firmness Methods

Destructive Maximum Force to

Penetrate a Known Distance into Fruit.

Deformation

For

ce

FMAX

Non-Destructive Force Required to

“Squeeze” Fruit.

Measure of elastic tissue properties.

Measures tissue 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.

Uses a calibrated spring to measure the resistance to deformation.

Nondestructive for firm fruit, but will bruise soft fruit.

$800 - $12008

A durometer consists of: A calibrated spring,

A tip displacement gage, and

A retractable tip

Principle of Operation

Pear

0 100

0 percent

40

Tip extends2.5 mm

CalibratedSpring

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Principle of Operation

Pear

0 100

0 percent

40

0 100

DurometerDisplays

100 percent

Pear

40

Tip extends0.1 inches

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

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Principle of Operation

Pear

0 100

0 percent

40

Pear

0 100

40

40 percent

0 100

100 percent

Pear

40

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

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Bartlett Pear

y = 0.5525x - 2.5

r2 = 0.77

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25

30

35

40

45

50

55

40 50 60 70 80 90 100

'E' Durometer (%)

Imp

act

Fir

mn

ess

(Sin

clai

r) R2 = 0.77

Durometer measurement of Bartlett Pears

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Durometer Measurement of Bartlett Pears

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

40

50

60

70

80

90

100

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

Sco

re

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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

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Principle of Operation

A

t

Firmness Index

t

A

PeaktoTime

onAcceleratiPeakC

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Principle of Operation

A

t

A

t

Firmness Index

t

A

PeaktoTime

onAcceleratiPeakC

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Monitoring Impact FirmnessDuring Ripening of Mango

Source: I. Shmulevich

time

acce

lera

tion

CDay1=275

CDay7=65

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UC Davis handheld nondestructive firmness sensor for orchard use.

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OnlineModel

Bench Top model

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

value.

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Clingstone Peaches

Comparison of Penetrometer Firmness vs Impact Firmness

R2 = 0.6

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

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

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

Firmness = f2 * m2/3 , where f = frequency & m = mass

On-line model

Bench top model

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Acoustic Firmness Principle

Natural frequency and firmness Acoustic Firmness =f2 m2/3

where :f - first resonant frequency

m - fruit’s mass.

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Acoustic Firmness sensor

10000

3

22 mf

S

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Acoustic Firmness sensor

Good

Hollow

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

Acoustic impact can also detect internal cavities in melons.

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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

whole fruit is measured.

Some internal defects can be sensed

Works better on firm fruit

Impact Method Local spot

measurement Elastic properties of

exterior flesh is measured.

Cannot sense internal defects

Works better on soft fruit

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Automatic Fruit QualityGrading in Cherry

Stem Width

FirmnessFruit WidthColor

Pulp Temperature

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Optical Firmness Principle

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

Yankun Peng, Renfu Lu. 2007. Journal of Food Engineering 82:142–15228

Volatile Sensing

Electronic nose 32 co-polymer sensors

Classify volatiles using artificial neural network.

Detecting freeze damage in oranges

32 co-polymer sensors29

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.

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

• $800 Etoh

Sensor.30

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Electromagnetic Spectrum

X-RAY

ULTRA-VIOLET

INFRAREDRADIOWAVE

MICROWAVE

108 109 1010 1011 1012 1013 1014 1015 1016 1017

1010 109 108 107 106 105 104 103 102 10 1

FREQUENCY (Hz)

WAVELENGTH (nm)

NIR

VISIBLE

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Material/Light Interactions

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

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Karl Ewald Hering(1834-1918)German Physiologist

When viewing a mixture of psychologically pure red and pure green lights,

• a person will see: red, green, or white,

• never yellow.

• Hering created a theory of color vision based on three opposing pairs:

• Red – Green

• Yellow – Blue, and

• Black - White

HumanEye

Afterimage Example Stare for ~30s at center, then switch

to white slide.

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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 available from several manufacturers.

L* represents luminous intensity

a* represents the red - green content

b* represents the blue - yellow content

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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

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Clingstone Peach Maturity

0

45

270

180

90

80

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

Peaches with a flesh hue angle below 80 degrees are mature

CIE hue angle

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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.

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Absorbance Spectra Below is a picture of a cup of water

What color would the water appear in the infrared?

Black 40

Absorbance Spectra

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NIR Applications in Food

Moisture Grains, Forages, Fruits,

Meat, Milk, Cheese, Seeds, Soil.

Protein Grains, Forages, Meat,

Seeds.

Soil Nitrogen Ethanol Beer, Wine.

Fat Oil seeds, Milk, Meat,

Cheese, Snack Foods, Human Triceps.

Carbohydrates Grains, Breakfast

Cereals, Seeds.

Starch Grains, Seeds, Kiwifruit.

Fiber Grains, Forages.

Amino Acids Grains

Defects Bruising, Contaminants.

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On-line Near Infrared (NIR) Measurements

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

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NIR On-lineSugar sensor

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Miller & Zude−Sasse (2004)

NIR on-line testred grapefruit (20 oC)

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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, 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

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New commercial handheld instruments have been recently developed for measurement of internal quality parameters such as oBrix.

Handheld Instrument for Nondestructive Determination of Internal Quality

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

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Immature

Identification of Immature Green Tomatoes at the Time of Harvest

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Tomato Spectrum

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

Results

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Measurement of Fresh Fruit Spectrum using ‘Nirvana’ Spectrometer

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Peach Spectrum (Flesh Color)

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Results Measurement of Soluble Solids in Peaches

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Measurement of Flesh Color in Peaches

Results

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

Results

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Measurement of Internal Quality (Soluble Solids) of Mandarins

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Measurement of Internal Quality (BrimA score) of Mandarins

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Fluorescence

(vibration or heat)

Some molecules can re-release absorbed optical energy as a lower energy photon.

http://probes.invitrogen.com

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Example: Using citrus peel oil fluorescence to determine fruit quality

Tangeretin a nonvolatile, neutral flavone.

fluoresces an orange color under long 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.

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Peel Oil under Blacklight

grapefruitlemon

lime

orange

tangerine

Viewed under blacklight

grapefruitlemon

lime

orange

tangerine

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Low level offreeze damage

Moderate to severe freeze

damage

Freeze Damaged Oranges Fluoresce

Relationship to flesh damage Varies with both freezing &

thawing conditions.

• Agreement between the USDA and UV methods ranged from 35% to 85% in lab. and field studies in 2006 & 2007 62

Thrip Damage

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

Thrip damage is also visible under blacklight

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Note that the infected lemon does not fluoresce

Appearance of decay lesions under UV light

Smilanick, 2008 64

0 2 31

75

50

25

0

Initial

After 3 weeks

%

Fluorescence classNONE VERY HIGH

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

GoodFruit

Smilanick2008 65

Grove Inspection using UV flashlights

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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. 200567

Hydrogen

Nuclear Magnetic Resonance (NMR)

Hydrogen atoms in a biological material act like magnetic dipoles due to the rotation of the electron around the proton. S

N

Electron

Proton

MagneticDipole

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Nuclear Magnetic Resonance (NMR)

Under normal conditions the magnetic dipoles point in random directions.

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Nuclear Magnetic Resonance (NMR)

The material is placed inside a powerful 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.

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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 the relaxation time (usually within milliseconds).

The realignment process creates its own radio frequency signal that is detected by the system. 72

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NMR measurement of Avocado Quality

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NMR - Data Analysis

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NMR - Example Applications

Seed/pit detection

Worm damage

Bruises

Water core

Freeze damage

Magnetic Resonant Image of Partially

Frozen Orange

Freeze Damaged Tissue

Healthy Tissue

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Portable MR System

Magnet

Electronics

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

Fruit

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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

Before Energizing

Metal Plate

Metal Plate

Dielectric Material

+ Positive Charge +

- Negative Charge -

+ +

-

+ +

-

+ +

-

+ +

-

+ +

-

+ +

-

After Energizing77

Dielectric Moisture Meter

Empty Walnut Drying Bin Bin Sides are a Capacitor with Walnuts as the Dielectric Material 78

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X-Ray & Gamma-Ray

Maturity of lettuce heads

Defect detection Freeze damage in citrus -

online

Split pits in peach

Hollow heart in potato -online

Bruises in apple

Olive, showing fruit fly entrance hole

X-ray image showing tunnels.

R. Haff79