2005 o’callaghan - cheese texture

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MOOREPARK FOOD RESEARCH CENTRE

END OF PROJECT REPORT 2005 MFRC No.60

CHEESE TEXTURE

D.J. OCallaghan

Cheese texture is important for consumer acceptability and for determining the end use of the cheese. Cheese identity is associated with textural attributes in addition to cheese composition. The definitive assessment of cheese texture, i.e.using a trained panel of assessors, can be supplemented by rheological measurements and by online infrared spectroscopy which offer rapid, objective, non-destructive analyses of texture and composition.

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Process Improvements in Cheese Manufacture through RapidMeasurement of Moisture, Texture and Composition(Cheese Texture)

RMIS No. 5006

Project TeamMoorepark Food Research Centre Teagasc:

D.J. OCallaghan (Leader)T.P. GuineeV. Howard (MFRC)G. Downey (AFRC)

In Collaboration with:C.P. ODonnell and C.D. Everard, Biosystems Engineering Department,University College DublinC.M.Delahunty and E.M. Sheehan, Department of Nutritional Sciences,University College Cork

Funding was provided under the National Development Plan, through the Food Institutional Research Measure,administered by the Department of Agriculture and Food.

Moorepark Food Research CentreMoorepark, Fermoy, Co. Cork

ISBN: 1 84170 421 0MFRC No. 60 Teagasc, December 2005

Teagasc,Oak Park, Carlow

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SUMMARY AND CONCLUSIONS

Sensory and rheological techniques were used to assess natural and processed cheese texture. The influence of moisture and pH on texture characteristics of Cheddar cheese and processed cheese was investigated. A new technique was developed for measuring rheology of soft cheeses.Near infrared (NIR) spectroscopy was investigated for prediction of cheese texture and for monitoring moisture, pH and ripening of Cheddar cheese and composition of processed cheese.

The main findings were as follows:

* The firmness of Cheddar cheese decreased during maturation, as one might expect due to proteolysis.

* During the early ripening period, Cheddar cheese generally became less chewy and springy, increased in the sensory attributes crumbly and mass- formation and decreased in moist.

* During the later ripening period, cheeses generally became more adhesive and decreased in fracture stress and strain, cohesiveness,chewiness, firmness and springiness. Simultaneously, sensory testing of cheeses showed increases in rubbery and chewy and decreases incrumbly during later maturation.

* Mature cheese showed less variation in texture than young cheese.

* NIR spectra could be used to estimate the maturation of cheese with ahigh level of accuracy, provided a calibration is done using samples spanning the expected ages.

* Cheese with moisture around 37 - 38% was the most firm.* Lower moisture cheeses, which were more chewy at manufacture, lost much of their chewiness and became more like higher moisture cheeses during maturation, reflecting protein degradation.

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RESEARCH AND RESULTS

Estimation of maturity and sensory attributes in Cheddar cheeseusing near infrared (NIR) spectroscopy

Texture of Cheddar cheese was evaluated using rheological and sensorytechniques during maturation and to determine relationships betweeninstrumental (i.e. rheological) and sensory (i.e. by human panel)techniques. In parallel with this, NIR spectroscopy was investigated as atechnique for assessing the maturity and sensory attributes in Cheddar

cheese in the course of ripening.

Cheddar cheeses were manufactured using five different rennets(coagulants), derived from animal and microbial sources (chymosin,chymosin/pepsin blend, and individual proteinases from R hi z o muc o r miehei , Cryphonectria parasitica and Rhizomucor pusillus ). Descriptivesensory analysis of cheese texture was carried out in duplicate on all 24natural cheeses up to nine months maturation by a trained panel in UCC.

Fig. 1. Firmness of Cheddar cheese in the course of maturation for five enzyme types. (Std. Calf refers to standard calf rennet, which is a blend of chymosin and pepsin).

Chymosin

Rhizomucor pusillus

Rhizomucor miehei

Std. Calf

Cryphonectria parasitica

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The most rapid changes in texture were observed during the first twomonths of ripening, e.g. firmness, measured by compression on a textureanalyser, decreased rapidly during the first 2 months of ripening anddecreased more slowly thereafter, the type of enzyme not having anysignificant effect (Fig. 1). Fracture stress, likewise, fell rapidly during the first1 - 2 months of ripening and the enzyme type had a strong influence onfracture strain after two months of storage, but this influence became lesssignificant as the cheeses matured (Fig. 2). Fracture strain also decreasedduring ripening, but with different effects from the enzymes used; themicrobial enzymes produced cheeses with lower fracture strain (more brittle)

than the animal enzymes (Fig. 3).

After two months of ripening, the sensory panel described the cheeses asrubbery, fragmentable and greasy/oily, while at nine months the cheeses were described as having mouth-coating, melting and mass-formationattributes (Appendix 1). During the 9-month ripening process, the intensityof the rubbery attribute decreased, while that for crumbly increased.

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Fig. 2. Fracture stress of Cheddar cheese in the course of maturation by enzyme type.

Chymosin

R. pusillus

R. miehei

Std. Calf

C. parasitica

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Fig. 3. Fracture strain in the course of maturation by enzyme type.

Fig. 4. Reflectance spectra of Cheddar cheese samples, represented as mean ( ) and

standard deviation ( ), n = 100. The reflectance spectra are plotted as log (1/Reflectance),

a mathematical pre-treatment, commonly used for linearising reflectance data. The standard

deviation shows the parts of the spectrum with most variation between different samples,

and hence scope for differentiating between samples.

Chymosin

R. pusillus

R. miehei

Std. Calf

C. parasitica

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NIR reflectance spectra of Cheddar cheeses, described in Appendix 1,showed variations due to moisture and fat (Fig. 4) . NIR spectroscopy

estimated the age of cheeses, stored up to 9 months at 7C, with aprediction accuracy of 0.61 months (Fig. 5) . The prediction of sensoryattributes by NIR reflectance is illustrated by the prediction of crumbly andrubbery (Fig. 6) .

Influence of composition and ripening on rheology an d texture ofcheese

An experiment was undertaken to determine relationships between sensoryand rheological measurements of texture and to determine the influence of moisture and pH on texture development in Cheddar cheese during thecourse of ripening. Cheddar cheeses were selected from commercialproduction with a range of pH and moisture values, and subjected torheological and sensory texture analysis, and to NIR analysis, in the course

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Fig. 5 . Linear regression plots of predicted versus actual age of Cheddar cheese,where prediction was done by NIR reflectance.

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of maturation. The NIR technique was evaluated for its ability to predict

sensory properties of commercial Cheddar cheese. Note: pH varied from5.0 to 5.5 and moisture from 35.9% to 40.7%. The cheeses were vacuum wrapped and stored at 4C for one week and then at 7C for the remainder of the maturing period, according to normal commercial procedure.

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Fig. 6. Linear regression plots of predicted versus actual scores for the sensory attributes (a) crumbly and (b) rubbery, where prediction was done by NIR spectroscopy.

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Fig. 7. Influence of moisture and age of Cheddar cheese on a range of sensory

attribute scores and rheological parameters, namely (a) sensory firmness, (b)rubbery, (c) chewy, (d) fragmentable, (e) rheological firmness, and (f)springiness.

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Rheological parameters firmness, chewiness and springiness decreasedduring maturation (Figs. 7 and 8) . Similar trends were found forrheological and sensory measurements of texture for all cheeses.

Cheese manufacturers associate top quality cheese as being within adefined window of moisture content. The reasons for this, thoughcomplex, were demonstrated in this study. The influence of increasingmoisture content on cheese texture is illustrated by the associateddecreasing scores for sensory attributes, firmness, rubbery, chewy andfragmentable (Fig. 7) . The rheological parameters, firmness andspringiness, were more discriminating than sensory measurements inseparating the cheeses according to age and moisture and revealed

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Fig. 8. Changes in: (a) chewiness by texture profile analysis, and (b) scores for the sensory attribute chewy for Cheddar cheeses with respect to moisture content at different stages of maturation.

1-2 months

2-3 months

4-5 months

8-9 months

1-2 months

2-3 months

4-5 months

8-9 months

0

5

10

15

20

25

30

35

35 36 37 38 39 40 41

C h e w y

0

5

10

15

20

25

30

35

40

45

35 36 37 38 39 40 41

C h e w i n e s s

A

B

Moisture

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maxima around 38% moisture. Likewise, a comparison of (rheological)chewiness with (sensory) chewy shows that the rheological measurementdiscriminated the effects of ageing much more effectively, as one wouldexpect (Fig. 8) .

For some sensory texture attributes, the changes during early maturationreversed during later maturation, e.g. scores for crumbly increased andmoist decreased during the first four months of storage but these changes were reversed after 8 months storage (Fig. 9) .

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Fig. 9 . Effect of Cheddar cheese maturation on scores for sensory parameters moist and crumbly at three stages of maturation: (1) 2 - 3 months old; (2) 4 5 months old; (3) 8 9 months old.

Key for Cheddar cheeses:MMLP = medium moisture, low pH; LMLP = Low moisture, low pH; HMLP =high moisture, low pH; LMHP = low moisture, high pH; MMHP = mediummoisture, high pH.

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Effect of measuring temperature on texture profile

The effect of measuring temperature on the rheological texture of Cheddarcheese is illustrated by force-time and force-displacement curves atrefrigeration (4C) and room (20C) temperature, respectively. Firmnessdecreased with temperature, as would be expected. Cohesivenessincreased with temperature, probably due to greater structural flexibility(Table 1) . The intrinsic relationship between cohesiveness, firmness andchewiness is such that the observed increase in cohesiveness, combined with the decrease in firmness, resulted in no effect on chewiness.

The differing effects of temperature on different texture profile analysis(TPA) parameters illustrates the importance of specifying the temperature at which TPA measurements are carried out and the need to work at the sametemperature when making comparisons between different studies ordifferent products. A working temperature of 4C was used for rheologicalmeasurements throughout this study, unless stated otherwise.

Estimation of moisture and pH using near infrared (NIR)spectroscopy

NIR spectra were used to estimate moisture and pH in Cheddar cheese:

(a) NIR spectroscopy predicted moisture, in the range 35 40 (% w/w), to 0.75 accuracy (% w/w, standard error of prediction), and (b) NIRspectroscopy predicted pH, in the range 5.0 - 5.6 to 0.15 accuracy.

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Table 1. Effect of temperature on TPA parameters for mature Cheddar cheese compressed to a strain of 0.7 without any rest period between compression strokes.

Temperature Firmness Fracture Chewiness Adhesiveness Springiness CohesivenessC (N) stress (N) (N) (Nmm)

4 214 145 9.6 37.6 0.311 0.145

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Processed Cheese

New method fo r assessing thickness of molten cheese

The thickness, or viscosity, of molten cheese, i.e. processed cheese duringthe cooking stage, was assessed at 80C using a spreadability rig attachedto the texture analyser (Fig. 10) . The blend became more viscous duringcooking until it reached a maximum.

Influence of ingredient formulation on texture, moisture andmeltability of processed cheese

The influence of the composition of processed cheese on its texture wasinvestigated by producing a series of processed cheese samples with varyinglevels of fat, moisture and emulsifying salt (di-sodium phosphate, 1 - 3%)and sodium chloride.

Rheological properties of processed cheese were evaluated using themethod of texture profile analysis (TPA) (Table 2). Rheological texture

Table 2. Texture Profile Analysis (TPA) parameters and physical definitions.

Terminology Physical definition (TPA term) Units

Fracture stress Stress (or sometimes, force) to fracture point,H 1 (Fig. 17) Pa, kPa

Firmness a Stress (or sometimes, force) at a givendeformation Pa or kPa

Springiness Percentage of deformation which is recovered -(or elasticity) between the first and second bites

Cohesiveness Area of second bite over area of the first bite -(A 2 /A 1) in Fig. 17

Chewiness Hardness x Cohesiveness x Springiness Pa, kPa

Adhesiveness Work necessary to pull the plunger (compression plate) away from the sample(Area A3 in Fig. 17 ) J/m 3

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properties were well established when measured 2 weeks after manufacture,and generally did not change between 2 weeks and 4 weeks. Firmness waslow in reduced fat cheese (26%) with a low level of emulsifying salt (1%)and increased when either fat or emulsifying salt level was increased at theexpense of water. The low fat cheeses were softer and more spreadable with little tendency to fracture. When the water content was increased atthe expense of protein and fat, the processed cheeses became much lessfirm and yielded more easily. When moisture was increased from 42 to48% (protein falling from 21 - 18%, fat content falling from 30 to 27%, andemulsifying salt at 2%) cheese firmness decreased from ~150 N to < 50 N.

Sensory textural attributes, like their rheological counterparts, did notchange between 2 and 4 weeks storage. Cheeses manufactured with highmoisture and medium to low fat levels were described predominantly as

creamy and melting, whereas cheeses manufactured with lower moisture,high-medium fat and low emulsifying salt content were chiefly described asfirm and mouth-coating. Cheeses manufactured with medium moisture,medium-high fat, medium and high emulsifying salt content were describedas fragmentable and rubbery.

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Fig. 10. Spreadability rig (a), used for measuring rheology of soft cheeses;schematic illustrating start (b) and end (c) of test.

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Fig. 11. Linear regression plots of predicted versus actual texture-related rheological parameters: (a) adhesiveness, (b) chewiness, (c) cohesiveness, (d)springiness, (e) hardness and (f) meltability, based on prediction using NIR spectroscopy in the waveband 1100 - 2500 nm.

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Fig. 12. Linear regression plots of predicted versus actual sensory parameters: (a) fragmentable, (b)

firmness, (c) rubbery, (d) creamy,(e) chewy, (f) mouth-coating, (g)greasy-oily, (h) melting and (i) mass- forming, based on prediction using NIR spectroscopy in the waveband 1100 - 2500 nm.

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Use of near infrared (NIR) spectroscopy fo r assessment ofcomposition (moisture, fa t an d salt) an d texture in processed cheese

NIR spectroscopy was used to predict rheological and sensory texture.Prediction models were developed for rheological texture measurement(Fig. 11) . The accuracy of NIR in estimating sensory texture parameters isillustrated by regression plots (Fig. 12) .

NIR spectroscopy was also used to estimate moisture, fat and salt inprocessed cheeses with low, medium and high moisture contents as shown

in Figure 13 . This technique is based on the peaks and variations,

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Fig. 13. Linear regression plots of predicted versus actual values for: (a) fat (%

w/w), (b) moisture and (c) salt, based on prediction using NIR spectroscopy in the waveband 1100 - 2500 nm. The 2nd derivative of the raw spectral data was used. Accuracy of prediction, as standard error of cross-validation (SECV) = 0.45, 0.50 and 0.26 respectively. Correlation coefficients: R = 0.98, 0.99 and 0.90,respectively.

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associated with moisture and fat in the plots of visible / NIR reflectancespectra of processed cheeses (Fig. 14) . Dissolved salt does not producepeaks in the spectrum; however, salt content affects the location of moisturepeaks and the location and shape of fat peaks. All else being equal, NIR ispreferable to visible light because it avoids the confounding effects of colour.

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Fig. 14. NIR reflectance spectra of three processed cheese samples, differing inmoisture and fat level, with the same emulsifying salt level (2% w/w), illustrating the differences between spectra which are the basis of differentiation between samples.The reflectance spectra are plotted as log (1/Reflectance).

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Fig. 15. Schematic of compression test apparatus.

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Appendix 1. Techniques investigated

Quantitative descriptive sensory protocol

A quantitative descriptive sensory protocol was defined for cheese texturemeasurement, according to international standards (Delahunty and Drake,2004; ISO 8586, 1993). Descriptive sensory analysis was carried out inUniversity College Cork using a vocabulary of eleven texture termsspanning the phases of the chewing cycle (Table 3).

Each assessor was provided with a list of the defined vocabulary. Eachsample (a 5 g cube, labelled with a random 3-digit code) was equilibratedto room temperature (21C). Cheeses were scored for attributes onunstructured 100 mm line scales labelled at both ends with extremes of eachattribute. Cheese scores were averaged across assessors for each attribute.

Texture profile analysis (TPA)

The cheeses were cut into 25 mm cubes and stored at 4C. Each sample was subjected to a double-bite compression to 30% of original height, usinga texture analyser (model TA. HDi TM Stable Micro Systems) with a 75 mmcompression plate and a 100 kg load cell (Figs. 15 and 16) .

Firmness was measured as the force at maximum compression on the firstbite, i.e. at a strain of 0.7. Fracture stress was measured as the force per unitarea at the point of fracture on the first bite, i.e. the force required to causecomplete fracture of the sample, corresponding to breaking structural bonds within the sample (Fig. 17) .

Cohesiveness was computed as the ratio of the area of the second bite tothat of the first bite. Springiness was calculated as the fraction of deformation that is recovered between the first and second bites, andgenerally depends on the period of relaxation. Chewiness and adhesiveness were calculated as in Table 2 .

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Table 3. Attributes, their definitions and phase of the chewing cycle, used to evaluate texture of the cheese samples during ripening.

Attribute Definition Phase of the chewing cycle

Firmness The extent of the initial resistance Judged on the first

offered by the cheese. 1 chew using the front teeth.

Rubbery The extent to which the cheese Assessed during the

returns/springs to its initial form first 2-3 chews.

after biting. 2

Gritty / Grainy The amount of small hard grains or

bits that are in the cheese. 2

Moist The perceived moisture content of the

cheese. 3

Crumbly The extent to which the cheese structure

breaks up in the mouth. 2

Chewy The effort needed to break down the Judged in the middle

structure of the cheese. 2 phase of mastication.

Mouth-coating The extent to which the cheese clingsto the inside of the mouth (roof, teeth,

tongue, gums). 2

Fragmentable Breaks down to smaller versions Probably judged towards

of itself.2 the end of chewing.

Melting The extent to which the cheese melts

in the mouth. Smooth velvet fullness

in mouth. 2

Mass formation The extent to which the cheese forms a

bolus or mass in the mouth after

chewing. 2

Greasy/Oily The extent to which a greasy/oily residue Judged at the end

is deposited in the mouth after the cheese of the chewing sequence.

is broken down. 2

1 - Ranging from soft to firm; 2 - Ranging from a little to a lot; 3 - Ranging from dry to moist.

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Infrared spectroscopy

The sample presentation technique was based on reflectance from solidcheese cylinders. Spectroscopic data were collected in reflectance modebetween 400 and 2500 nm using a scanning monochromator (Model 6500FOSS NIR Systems). All samples were equilibrated to room temperature (20- 24C) prior to NIR analysis.

Three cylinders (30 mm height x 38 mm diameter) of cheese were removedfrom each sample with the aid of a cork borer. Each cylindrical sample was

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Fig. 16. Compression of cheese for measurement of TPA parameters, showing,(a) cube of Cheddar cheese before compression on TA. HDi TM, and (b) cheese sample after compression to 30% of original height (strain = 0.7).

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then placed in a standard circular reflectance cup and sliced to the cupdepth (10 mm) using a flexible cheese wire. Each of these three replicatesub-samples was scanned in triplicate with rotation of the sample cupthrough approximately 120 between successive scans of each sub-sample.

The average of all nine spectra of each cheese sample was subsequentlyused for calibration development and evaluation.

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Fig. 17. Stress-time curve in double-bite compression test, which is used to calculate TPA parameters (Table 2) . A1 and A2 represent the areas under the compression portions of the first and second bites, respectively, and the ratio between them is denoted cohesiveness. A3 represent the areas under the suction(or withdrawal) portion of the first bite and is denoted as adhesiveness. H 1represents the fracture stress.

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Selected Publications

Blazquez, C., Downey, G., ODonnell, C., OCallaghan, D. and Howard, V.(2004). Prediction of Moisture, Fat and Inorganic Salts in Processed Cheese byNear Infrared Reflectance Spectroscopy and Multivariate Data Analysis. Journal of Near Infrared Spectroscopy , 12: 149-158.

Delahunty, C.M. and Drake, M.A. (2004). Sensory character of cheese and itsevaluation. In: Cheese: Chemistry, Physics and Microbiology: General Aspects.3rd Ed. Vol.1 (Eds. Fox, P.F., McSweeney, P.L.H., Cogan, T.M. and Guinee,T.P.). Elsevier, London, 455-488.

OCallaghan, D.J. and Guinee, T.P. (2004). Rheology and texture of cheese. In:Cheese: Chemistry, Physics and Microbiology, 3rd Ed. Vol.1 (Eds. Fox, P.F.,McSweeney, P.L.H., Cogan, T.M. and Guinee, T.P.). Elsevier, London, 511-540.

Downey, G., Sheehan, E., Delahunty, C., OCallaghan, D., Guinee, T. andHoward, V. (2005). Prediction of maturity and sensory attributes of Cheddarcheese using near infrared spectroscopy. International Dairy Journal , 15 (6-9):701-709.

Everard, C.D., ODonnell, C.P., Sheehan, E.M., OCallaghan, D.J., Delahunty,C.M. and Fagan, C.C. (2005). Correlation between process cheese meltabilitydetermined by sensory analysis, computer vision method and Olson and Pricetest. International Journal of Food Properties , 8:267-275.

Fagan, C.C., Everard, C., ODonnell, C.P., Downey, G. and OCallaghan, D.J.(2005). Prediction of inorganic salt and moisture content of process cheese usingdielectric spectroscopy. International Journal of Food Properties, 8:543557.

Blazquez, C., Downey, G., OCallaghan, D., Howard, V., Delahunty, C.,Sheehan, L. and ODonnell, C. (2006). Modelling of sensory and instrumentaltexture parameters in processed cheese by near infrared reflectancespectroscopy. Journal of Dairy Research, 73 (1):58-69.

Everard, C.D., ODonnell, C.P., OCallaghan, D.J., Howard, T.V., Sheehan,

E.M. and Delahunty, C.M. (2006). Relationships between sensory andrheological measurements of texture in maturing commercial Cheddar cheeseover a range of moisture and pH at the point of manufacture. Journal of Texture Studies (in press).

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Figures in this Report - Source

Fig. 6: Downey, G., Sheehan, E., Delahunty, C., OCallaghan, D., Guinee, T.and Howard, V. Prediction of maturity and sensory attributes of Cheddar cheeseusing near infrared spectroscopy.I nternational Dairy Journal (2005) 15 :701709, Figs. 6a and b.

Figs. 11 and 12: Blazquez, C., Downey, G., OCallaghan, D., Howard, V.,Delahunty, C., Sheehan, L. and ODonnell, C. (2006). Modelling of sensory andinstrumental texture parameters in processed cheese by near infrared reflectance

spectroscopy.Journal of Dairy Research (2006) 73 :5869, Figs. 8 and 9.

Figs. 13 a, b and c: Blazquez, C., Downey, G., ODonnell, C., OCallaghan, D.and Howard, V. (2004). Prediction of Moisture, Fat and Inorganic Salts inProcessed Cheese by Near Infrared Reflectance Spectroscopy and MultivariateData Analysis.

Journal of Near Infrared Spectroscopy (2004) 12 :149-158, Figs. 3, 5 and 7.

For further information, please contact:

Dr. D.J. OCallaghan

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D.J. OCallaghan

MOOREPARK FOOD RESEARCH CENTRE

Moorepark, Fermoy, Co. Cork, IrelandTel: +353 (0) 25 42222 - Fax: +353 (0) 25 42340E-Mail: [email protected]

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2005 o’callaghan - cheese texture

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