THE RAPID MEASUREMENT

OF EGGSHELL STRENGTH*by

Peter W. Voisey and G. D. RobertsonEngineering Research Service

Research Branch, Canada Department of AgricultureOttawa

INTRODUCTION

The study of eggshell quality requires a means of measuring shellstrength to predict its ability to survive processes used in production,transportation and marketing. Because the variation in shell strengthis high, large numbers of eggs mustbe tested to obtain reliable data.Thus any method used must requireminimum labor.

It has been shown that shellstrength can be measured by compressing the egg between flat platesand that such a test yields a linearforce-deformation curve. The fractureforce (F) and total deformation (D)may be used to calculate shell stiff-

F

ness, S = —, and energy absorbedD

FD

up to fracture, E = . Fracture2

force, stiffness and energy are highlyintercorrelated (2, 5, 7, 8). The relation of shell stiffness to fracture forcehas been studied in non-destructive(4, 6) and destructive tests (1, 2, 5,7).

In the non-destructive test shelldeformation is measured under afixed load and is thus inversely proportional to stiffness. The apparatus(6) developed for this purpose hasseveral disadvantages. Shell deformation is small (< 0.035mm) and resolution of measurement is limited bythe dial gauge used. The force isapplied to the shell manually andthe rate of compression, which affects shell behavior (11), is not controlled. Friction at the plunger applying force to the shell is not takeninto acount. The effect of these factors was observed by Hunlon" usingthe apparatus developed by Schoorl

*Contribution No. 154 from EngineeringResearch Service, Research Branch, Canada Department of Agriculture, Ottawa.

and Boersma (6). It was necessaryto load the egg several times, untilshell deformation was the same intwo successive measurements. Thistechnique is therefore time consuming.

Apparatus used for destructivetests (2,7) have used strip-charts torecord force applied and shell deformation during compression tofailure. Considerable labor is required to take data from the charts.

The relationships among fractureforce, deformation and energy absorbed suggest a method by whichthe operating efficiency of eggshelltests can be increased. The energyused to compress the shell can be recorded by an electronic integrator,and the force at fracture by a peakforce amplifier. Deformation andstiffness can then be derived fromtheir relationships to energy absorbedand fracture force. The commonlyused physical shell properties canthus be obtained without using strip-charts and the data stored directlyon punched tape for computer analysis. The purpose of the work here isto demonstrate these techniques,compared with strip-chart recordingmethods, and to determine the relationship between non-destructive anddestructive measurements on thesame egg.

EXPERIMENTAL METHODSAND APPARATUS

It should be noted that the apparatus used in this experiment wasassembled from equipment on hand.The many alternative arrangementsand sources of equipment are notdiscussed.

A compression machine (ModelTM-M, Instron Canada Limited,Clarkson, Ontario) was used for theexperiment (figure 1A). The egg was

*Private Communication — Shaver PoultryBreeding Farms Limited, Gait, Ontario.

compressed between flat parallelstainless steel plates whose surfacefinish was 0.8M. The bottom surfacewas supported by a 100kg load cell(B, figure 2) attached to the baseof the machine (A) and the top surface by a 50kg load cell (D) attachedto the moving crosshead (E). Theegg (C) was compressed betweenthe two load cells (figure IB) andtwo equal output signals proportional to force on the shell wereavailable.

The top load cell (D) was connected to the recorder (F), suppliedwith the compression machine, whichwas calibrated so the full scale (0.25sec. response time) equalled 1kg.The "built in" load control circuitwas adjusted so that when the forceon the egg reached 0.5kg ± 0.5%,the crosshead was automatically re-reversed. An electronic integrator(G) (Instron, Model G-90-21) wasalso connected to the upper load cellto record the energy used in compressing the shell. Shell deformationwas determined using the relationship between the compression andrecorder chart (200 cm/min) speeds.

The bottom load cell (B) was connected to a strain-gage amplifier (H)(Model 300D-80, Daytronic Corp.,Dayton, Ohio) which was equippedwith a peak memory output module(M) (Model M, Daytronic Corp.).The output of the amplifier was connected to a potentiometric strip-chartrecorder (J) whose full scale (5.0kg)response time was 0.2 sec. (ModelE1101S Esterline Angus Inst. Co.,Indianapolis, Indiana) and a digitalintegrator (K) (Model CRS10X, In-fotronics Corp., Houston, Texas).The output of the peak memory module (M) was connected to a digitalvoltmeter (N). Two tape punches(L) were used to record the outputsof the integrator and digital voltmeter. Force and deformation couldthus be recorded throughout compression as well as the energy ab-

CANADIAN AGRICULTURAL ENGINEERING, VOL. 11, No. 1, MAY 1969

Figure I. A. The experimental apparatus B. An egg compressed between the two load cells

sorbed up to failure and the fractureforce.

Each recording instrument wascalibrated so that the relationship between force on the load cell and itsoutput was linear and repeatablewithin ± 0.5%. A single compressionspeed of 0.05 cm/min was selectedfor the test to eliminate variationsfrom this source (11). This speed wasused to ensure that the response timeof the different recording apparatuswas not exceeded (10).

Eggs were collected from a commercial type flock and defectiveshells discarded. Each egg was placedon the bottom load cell so that forcewas applied at the equator and compressed until the force applied was0.5kg, automatically unloaded usingthe system connected to the top loadcell and then compressed to failureusing the system connected to thebottom load cell. This procedure wasused to test 200 eggs and the following data noted or derived.

Where: ndc

i

v

non-destructivedestructivechartintegratordigital voltmeter.

Non-destructive test.

1. Non-destructive deformation Dnc.

2. Energy absorbed Eniin compress

ing the egg an amount Dn{;.

3. Energy absorbed Encin compress

ing the egg an amount Dncderived

from 0.5 D .

4. Shell stiffness S derived fromnc

0.5

Dnc5. Non-destructive deformation D„;

derived from 2 •0.5

Destructive test.

1. Force at fracture Fdc"

2. Force at fracture Fdy.

3. Deformation at fracture Dd<;.

4. Energy used to fracture the shellE , derived from Fdc Ddc

dc —-

5. Energy used to fracture the shellEdi-

6. Shell stiffness Sdc derived fromFdcDdc

7. Deformation at fracture Ddiv de-

Erived from 2

di

dv

For the purpose of this experimentit was assumed that shell deforma

tion could be measured from the

CANADIAN AGRICULTURAL ENGINEERING, VOL. 11, No. 1, MAY 1969

chart. This neglected the maximumestimated error of 2.5% due to deformation of the load cells (11).

RESULTS AND OBSERVATIONS

In all measurements made in eitherthe destructive or non-destructivetests the mean, range and coefficientof variation of the same traits weresimilar, (Table 1), thus it can beassumed that there is no loss of ac-

c-

--—Av\vaW

H - M

| > N

1 I 1K

L

Figure 2. Schematic diagram of apparatus.A. Base of test machine; B. 100kg loadcell; C. egg undergoing compression; D.50kg load cell; E. moving crosshead of testmachine; F. strip-chart recorder; G. digitalintegrator; H. transducer amplifier; J. strip-chart recorder; K. digital integrator; L.tape punch; M. peak force detector; andN. digital voltmeter.

TABLE I. MEAN, RANGE COEFFICIENT OF VARIATION (OV.)AND SIMPLE CORRELATION COEFFICIENTS FOR ALL VARIABLES

Variable :Fdc Fdv dcELdc Edi Sdc D

nc& •

ms

ncE

ncD .

ax div

Units: g g cm cmg cmg kg/cm cm cmg kg/cm cmg cm cm

2Mean 2720 2687 0.0172 23.6 25.0 158.5 0.0033 0.803 154.1 0.827 0.0032 0.0184

Maximum 4400 4345 0.0239 45.6 47.0 237.0 0.0054 1.370 238.1 1.350 0.0055 0.0262

Minimum 1640 1585 0.0131 12.6 14.0 100.6 0.0021 0.500 92.6 0.525 0.0020 0.0135

C.V. % 16.8 17.0 10.3 23.7 23.1 14.7 14.4 15.9 13-9 14.4 15.9 9.7

Fdv 0.994

dc0.499 0.514

\c 0.924 0.927 0.785

di0.925 0.928 0.767 0.992

dc 0.793 0.775 -0.x23 0.502 0.518

Dnc

-0.718 -0.700 0.088 -0.466 -O.U80 -0.888

E .m

-0.729 -0.713 0.095 -0.471 ^).490 -0.907 0.967

Snc

0.720 0.699 -0.106 0.456 0.473 0.907 -0.970 -0.931

Enc

-0.718 -0.700 0.088 -O.466 -0.480 -0.888 1.000 0.967 -0.970

D .ru

-0.729 -0.713 0.095 -0.471 -0.490 -0.907 0.967 1.000 -0.931 0.967

div 0.416 0.407 0.876 0.667 0.688 -0.127 0.089 0.088 -0.094 0.089 0.088

1. See text for identification.

2. 200 samples.

curacy or precision in using digitalrecording techniques. The small differences that occurred can be attributed to the errors introduced byneglecting deformation of the loadcells and assuming that force islinearly related to deformation (9).Correlation coefficients betweenmeasurements from the digital recorders and those derived from thestrip charts, 0.876 (Ddc:Ddiv) 0.967

(D^D,,,), 0.992 (Edc:Edi), 0.994

(F,^:Fdv) substantiate this conclu

sion.

Correlation between stiffness determined destructively (Sdc) and

non-destructively (Snc) was 0.907.

This and the high correlation coefficients between other non-destructive

measurements and fracture forceagree with previous work and indicate that shell strength can be estimated non-destructively.

Correlation coefficients betweenfracture force (Fdc) and all energy

measurements were high and comparable to the correlation betweenforce and shell stiffness or non-destructive deformation. Thus it can beassumed that' energy measurementscan be used in destructive or nondestructive tests in place of forceand deformation measurements without loss of accuracy. This is substantiated by the fact that correlation coefficients between fractureforce and other traits were approximately the same for chart, digitaland derived data.

served that tests could be conductedat rates up to 150 eggs/hr dependingon the dexterity of the operator.

CONCLUSION

Eggshell strength can be estimatednon-destructively or destructively byrecording the energy used to compress the egg. Since this can be accomplished by electronic integrators,recording on punched tape, testingefficiency is increased.

SUMMARY

Systems are described for recording the energy and force required todeform eggshells in destructive ornon-destructive tests used to estimateshell strength. Shell deformation andstiffness can be derived from thesemeasurements.

During the experiment it was ob- continued on page 11

CANADIAN AGRCULTURAL ENGINEERING, VOL. 11, No. 1, MAY 1969

REFERENCES

1. Foster, G. H. Moisture ChangesDuring Aeration of Grain. A.S.A.E.Paper No. 65-921, Presented atChicago, Illinois, December, 1965.

2. Hall, C. W. Drying Farm Crops.Chapter 2. Agricultural Consulting Associates, Inc., Ann Arbor,Michigan, 1957.

3. McKenzie, B. et al. Dryeration —Better Corn Quality With HighSpeed Drying. Publication AE-72.Cooperative Extension Service,Purdue University, Lafayette, Indiana, 1968.

4. Shedd, C. K. Resistance of Grainsand Seeds to Air Flow. Agricultural Engineering, Vol. 34: September, 1953.

5. Thompson, R. A. and Foster, G. H.Dryeration — High Speed DryingWith Delayed Aeration Cooling.A.S.A.E. Paper No. 67-843, Presented at Detroit, Michigan, December, 1967.

According to Foster (1), coolingair with a relative humidity aboveequilibrium results in higher finalgrain temperatures and slightly lessmoisture removal. Figure 2 showsthe air temperature and relative humidity for equilibrium moisture content of shelled corn (2). If the airtemperature is 40°F. the equilibriumrelative humidity is 60% for 14%moisture corn. However, during theharvest period in 1967 night-timerelative humidities exceeded 90% 34nights out of 41 at Blenheim, Ontario.

To allow safe storage when goodaeration equipment is available thecorn should be cooled to an averagetemperature of 70°F. before beingtransferred. In deep corn beds, 30 to40 foot corn columns, the temperature of the lower corn layers approaches incoming air temperaturewhen a 70°F. average is reached.Some rewetting occurs but this hasnot been a serious problem if all thecorn is removed from the temperingbin.

SUMMARY

Dryeration is working satisfactorily for users with volumes largeenough to justify independent tempering bins and multiple elevatingfacilities. Research is continuing atPurdue University to find a satisfactory means of utilizing storagebins as tempering bins. Downwardair flow shows promising results (3).

To make dryeration successful, thedryeration system must be well designed and the management of thesystem must be well planned.

A source of heat to reduce highrelative humidities during coolingmay be necessary to make dryerationa dependable means of removingcorn moisture when adverse weather

conditions prevail.

Reducing the fines in corn makesconventional drying, dryeration andaeration more successful. All of these

processes require air movementthrough the corn mass, and restriction caused by fines can create serious problems when the air distribution is not uniform.

THE RAPID MEASUREMENT . . .

continued from page 8

An electronic integrator and apeak force amplifier are used to record the data on punched tapeeUminating the tedious work oftaking the data from strip-charts.Testing efficiency is increased andthe chances of human errors reduced.

An evaluation of the system indicates that shell strength can be predicted non-destructively from theenergy used to deform the shell.

REFERENCES

1. Brooks, J. and Hale, H. P.Strength of the shell of the hen'segg. Nature, 1955. 175, 848.

2. Hunt, J. R. and Voisey, P. W.Physical properties of eggshells.1. Relationship of resistance tocompression and force at failureof eggshells. Poul. Sci. 1966.45(6)1398.

3. Hunton, P. The measurement ofeggshell strength a comparisonof different methods. Brit. Poul.Sci. 1969 (in press).

4. Rauch, Von W. Die elastischeverformung con Huhnereiern als

CANADIAN AGRICULTURAL ENGINEERING, VOL. 11, No. 1, MAY 1969

masstab fur die beurteihmg derschalenstabilitat. Arch. Gefliigelk.1965. 29, 467.

5. Richards, J. F. and Staley, L. M.The relationships between crushing strength, deformation andother physical measurements ofthe hen's egg. Poul. Sci. 1967.46(2)430.

6. Schoorl, P. and Boersma, H. Y.Research on the quality of theeggshell. 12th World's Poul.Cong. 1962. 432.

7. Tung, M. A. Studies on physicalproperties of eggshells. Unpub.Msc. Thesis. 1967. Univ. Brit.Columbia.

8. Tung, M. A., Staley, L. M. andRichards, J. F. Studies on eggshell strength, shell stiffness, shellquantity, egg size and shape.Brit. Poul. Sci. 1968. 9(3):221.

9. Voisey, P. W. and Hunt, J. R.Relationship between appliedforce, deformation of eggshellsand fracture force. J. Agric.Engng. Res. 1967. 12(1)1.

10. Voisey, P. W. and Hansen, H. Ashear apparatus for meat tenderness evaluation. Food Technol.1967. 21(3A):37A.

11. Voisey, P. W. and Hunt, J. R.The efect of compression speedon the behaviour of eggshells.J. Agric. Engng. Res. (in press).

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