DAIRY FOODS Cheddar and Rheology'

M. H. TUNICK, E. J. NOLAN, J. J. SHIEH, J. J. BASCH, M. P. THOMPSON, B. E. MALEEFF, and V. H. HOLSINGER US Department of Agriculture, ARS Eastern Regional Research Center Philadelphia, PA 19118

ABSTRACT the cheddaring process (9). The resultant tex- Textural difEerences between Cheddar tural differences make rheological measure- and Cheshire were examined rhe- ments a logical choice for distinguishing the ologically to provide a means of distin- two cheeses. Some recent rheological work has guishing these two English cheeses. Body been repor&edon Cheddar (2, 3, 6) and Chesh- breakdown of a 6@wk Cheshire sample ire (3), but a comparison of the two for identifi- occurred at a lower strain than did a cation purposes has not been made. In this 20-wk sample, whereas a 60-wk Cheddar study, rheological and other analytical methods sample did not break down under the were compared in an attempt to differentiate same conditions. All cheeses followed the between English-made Cheddar and Cheshire Arrhenius equation, and the energy of cheeses. activation obtained varied with age and type of cheese. Other analytical tech- MATERIALS AND METHODS niques showed differences the between The cheese samples were manufactured in samples but were not suitable for distin- and purchased locally. The Cheshire guishing me of cheese from the type cheese was wk old when rheological tests other. 20 were first performed it wk old when (Key words: rheology, viscosity, cheese) on and 60 follow-up tests were made. The Cheddar was 60 wk old when examined rheologically. A INTRODUCTION 20-wk Cheddar was unavailable, since Cheddar Various cannot always be is usually imported from England after a year differentiated Using Stanbd analytical tech- of aging. Samples were tempered at room tem- niques. This presents a problem when the pos- perature for 5 h prior to rheological work sibility of mislabeling has to be investigated. The viscoelastic properties of the cheeses English Cheshire is usually sold between 2 wk were examined with a Rheometrics Dynamic and 10 mo after manufacture, and English Analyzer 700 (Rheometrics, Inc., Piscataway, Cheddar is often sold in the US after 1 yr of NJ), using a 0 to 200 gem torque transducer aging (7). Thus, an electrophoretic analysis of and parallel plates with a diameter of 2.50 cm. their proteins can be difficult because of differ- A cork borer was used to obtain a sample disk ent ages and levels of protein breakdown. Com- with a diameter of 2.5 cm and a height of 4 positional differences between Cheddar and mm. To prevent slippage, two drops of cyano- Cheshire are slight, because both typically con- acrylate bonding agent were spread evenly over tain 36 to 38% moisture, 23 to 25% protein, the lower plate, upon which the sample was and 30 to 33% fat (7). placed. Two drops of bonding agent were then Cheshire cheese is manufactured to keep the spread evenly over the cheese, and the upper curd particles separate, whereas Cheddar curd plate was lowered on top of it. The experiments particles are spread out and matted together in were carried out in an environmental chamber at 20'C, unless otherwise specified. The data obtained included the two components of the shear modulus G*:the elastic (storage modu- Received October 5,1989. lus) component G' and the viscous (loss modu- Accepted January 24,1990. lus) component G". Both were measured in 'Refnarce to firm or brand name. docs not constitate en- dorsanent by the. US Dcparlment of Agriculture. wes others dynes per square centimeter. The complex vis- of a similar nature not mentioned. cosity q* (in poises) and the fkquency o (in

1990 J Dairy Sci 73:1671-1675 1671 1672 mCKET AL. rads) were also measured. These parameters The relatively low percentage of %l-casein and are related as follows: Bcasein in the Cheddar, and the elevated per- centages of + %caseins, are indicative of (IG*1)2 = (G')2 + (G'')2 protein hydrolysis during ripening. The ages of the cheeses were confirmed by examining the and h*l = IG*l/w levels of casein breakdown, but electrophoretic information alone cannot distinguish the two With w set at 1.0 rads, values of G', G", types of cheese. and q* were obtained as the percentage of The specific heat values of the Cheshire at strain values were varied, resulting in a strain 20 and 60 wk were and .67 caVg sweep. .64 'K, Extracted and freaedn'ed cheese proteins respectively. The glycerides in cheese fat were dissolved in Tris-EDTA buffer and char- slowly crystallize with aging (8), and this prob- acterized by SDS-PAGE. Two methods were ably accounts for the increase in specific heat. used for preparing and developing the gels (1, The specific heat of Cheddar at 60 wk was .72 10). The relative amounts of protein in the caVg 'K, with the higher value being indicative resultant bands were measured with a Bio-Rad of a stronger cheese structure. Specific heat Model 620 (Bio-Rad Laboratories, Richmond, determinations can be useful in differentiating CA) densitometer. the cheeses, but more data would be needed to Specific heat at WC was measured with a prevent misidentification, since varying mois- Perkin-Elmer DSC-2 differential scanning calo- ture levels can affect the results. rimeter (Perkin-Elmer Gorp., Norwalk, (3"). Scanning electron micrographs of the two Duplicate samples weighing 2 to 5 mg were cheeses are shown in Figure 1. The Cheshire hermetically sealed in volatile sample pans, had a smooth continuous protein network sur- placed in the instrument at 37T, and heated to rounding irregular lipid inclusions ranging from 67'C at lO'C/min. The deflection from the 2 to 30 jm across. The lipid inclusions in the baseline at WC was divided by sample weight Cheddar were 1 to 5 jm across, and the protein and heating rate to obtain specific heat. matrix was denser. These results showed clear Scanning electron microscopy (SEM) was used to determine cheese microstructure. differences between the two types of cheese, Cheese pieces measuring 5 mm on a side were but the microstructures resemble those of some chemically stabilized with buffered glutaralde other cheeses. The microst~ctureof the Ched- hyde and osmium tetroxide and gradually dehy- dar, for instance, was similar to those of Moz- drated in increasing concentration of ethanol in zarella samples analyzed in an earlier study water. The samples were quick frozen in liquid (11). Therefore, SEM cannot be used by itself nitrogen and fractured with a scalpel to expose to tell Cheddar apart from Cheshire because of an uncut surface. Samples were finally dried by possible misidentification with other cheese va- the critical point method, mounted on SEM rieties. stubs with silver paint, and sputtercoated with The rheological measurements demonstrated 15 nm of gold-palladium. The prepared samples clear differences between the cheeses. The were examined with a JEOL JSM-WA SEM strain sweeps of the Cheshire cheeses after 20 operating at 5 kV. and 60 wk are shown in Figures 2 and 3. proteolysis during ripening results in decreased RESULTS AND DISCUSSION viscosity and elasticity of cheese (2,4), and this Percentages of the varieties of casein, as effect is demonstrated in the downward shift of determined by PAGE, are shown in Table 1. the G', G", and q* curves. Inflections are pre-

TABLE 1. Percentages of the various types of Cssein in 20-wk Cheshire aad 6Gwk Cheddar cheeses, as detmnined by densitometry of SDS-PAGE gels.

71 Para- r2+% sample %2 041 B Region K Region Cheshire 7.89 5.37 32.34 2.96 7.29 14.02 cheddar 2.23 1.65 22.05 1.93 6.45 28.86

Journal of Dairy Science Vol. 73, No. 7, 1990 CK-EESE RHEOLOGY 1673

pisare 1. Scanning elcctmn micrographs of Z&wk cbeahire cheese (top) and 6@wk Cheddar chetse.

Journal of Dairy ScimVol. 73, No. 7, 1990 1674 TUNICK ET AL.

TABLE 2. Values of complex Viscosity (log q*) at various temperalum.

1% ?+ Temperatore ('0 2Gwk CheJhire 60wk Cheshire Wwk Cheddar 20 6.05 5.94 6.19 25 5.90 5.71 5.74 30 5.64 5.50 5.40 35 5.24 5.23 5.00 40 4.91 4.96 4.60

sent in the curves at approximately 12% strain tained at various temperatures using a o of 1.0 in the younger cheese and at roughly 8% strain rad/s. The decrease in complex viscosity with in the older sample. The inflection suggests inmasing temperature is shown in Table 2. crumbliness resulting from body breakdown With each cheese, a plot of q* versus recipro- (8). The amount of stress the cheese can with- cal of absolute temperature (lm produced a stand before breakdown decreases during npen- straight line which followed the Anhenius ing (2, 8), which is evidenced by the shift with equation: age of the inflection point. The strain sweep of 60-wk does not show such an q* = AyiSc exp O%,dRV, inflection Figure 4). At 0% strain, the values of G', G", and q* of the Cheddar are almost where AVkc is the preexponential factor, &isc twice those of the 60-wk Cheshire. These find- is the activation energy, and R is the gas con- ings are consistent with Cheshire being the stant (1.987 caVC mol). By converting q* to crumblier of the two cheese types. loglo, E;Isc is equal to the slope of the line A linear region of G* was not present in any multiplied by 2.303R. The Anhenius equations of the strain sweeps, but quasilinear behavior and activation energies of the samples are (an essentially constant G*) was observed at shown in Table 3. The viscosity and energy of 2.5% strain in each of the samples. The values activation of the Cheshire decreased approxi- of q* for the cheeses at this strain were ob- mately 20% from 20 to 60 wk since the body of

lo "

10 10 20 10 20 % STRAIN % STRAIN figure 2. Strain sweep of 2Gwk Cheshke cheese, with Figure 3. Strain sweep of 6Gwk Cheshire cheese, with (a)= 1.0 IWS. ~lasticcomponent G' (dynlCm2). frequency (a)= 1.0 ra&. Elastic component G' (dy4az), viscous component G" (dy4an2), and complex Viscosity viscous component G" (dyn/aZ), and complex viscosity q* (poise) plotted versus percentage of strain. q* (poise) plotted versus pacentage of strain.

Journal of Dairy Science Vol. 73, No. 7, 1990 CHESE RHEOLQGY 1675

TABLE 3. Arrhenius equations and activation energies of the checses.

Sample Eqaationl %Sc2 (cal/mol) 20-wk Cheshire 1% q* = 5331fI’ - 12.05 %m 60-wk Cheshire 1% q* = 444m - 9.20 20.250 60-wk cheddar 1% q* = 7156fI’ - 18.24 32,750 $* = Complex viscosity 0% q*); T = temperam. 2Ev, = Slope x 2.303 R. the cheese was breaking down. The higher & guish the two cheeses. The expected decreases value for the Cheddar indicates that its body with age in viscosity, elasticity, and body breaks down less easily than that of Cheshire. strength were observed with Cheshire. Body In another study (6), a Cheddar sample of breakdown of Cheddar was not seen under the unknown age, but presumably less than 1 yr, same conditions, and its energy of activation had an EylW of 36,700 cal/mol using the same was much higher than that of Cheshire. Other conditions and instrumentation. Commercially analytical methods did not produce a reliable available Cheshire cheese appanmtly will have distinction between the two. an E,,& much lower than that of Cheddar. Rheological properties of cheese are affected by its composition. For instance, the elasticity REFERENCES and firmness Of With decreas- 1 Basch, J. J., P. W. Douglas, Jr., L. G. Procino, V.H. hg fat content, and a cheese Will become softer H~I~,and H. M. pane& Jr. 1985. Quantitation of if its moisture content is elevated (5). Composi- why ofproces~milks and whey tional variations and their effect on viscoelastic protein concentratw, application of gel electrophoresis, properties of cheese will be the subject of and mparison withHarland-~wortbprocedure. J. future research. Dairy Sci. 6823. 2Creamer. L. K.. and N. F. Olson. 1982. Rheolonical CONCLUSIONS evalnati& of &hniog Cheddar cheese. J. Food. ScL 47: 631. Measurements of rheological properties of 3 Dickinson, E., and I. C. Godding. 1980. Yield behaviour of ClUmMy English cheeses in compression. J. Texture Cheddar and Cheshire can be used to distin- Stud. 1151. 4 Lawrence, R. C., and J. Gilles. 1987. Page 27 in Cheese chemistxy, physics and microbiology. Vol. 2. Major cheese groups. P. F. Fox, ed. Elsevier Appl. Sci. Publ., LondcMb UK. 5 hyten, H. 1988. The rheological and fracture properties ofGoudacheese. Ph.D. Diss., WageningenAgric. Univ., Holland. 6Nolan, E. J., J. J. Shieh. and V. H. Holsinger. 1989. A comparison of some rheological properties of Cheddar and pasteluized process American cheese. Roc. 5th Int. Cangr. Eng. Food, Cologne, W. Gamany. 7 Posati, L. P., and M. L. Orr. 1976. Composition of foods. Dairy and egg products. Agric. Res. Serv., US Dep. Agric.. washington, Dc. EPrentice, J. H. 1987. Cheese rheology. Page 339 in Cheese chanisey, physics and microbiology. Vol. 1. Gendaspects. P. F. Fox, ed. Elsevier Appl. Sci. Publ., , , , , , , , London, UK. ; \7:;:-- 1 9 Scott, R 1986. Cheese making practice. 2nd ed. Elsevier Appl. Sci. Publ.. Lonndon, UK. 10 Thompson, M. P.. D. P. Browcr, and H. M. Farrell, Jr. 10 1987. Absence of detectable calmoddin in cow’s milk 0 10 20 K STRAIN by a modified gel electrophoresismethod. J. Dairy Sci. 701134. Figure 4. Strain sweep of 6@wk Cheddar cheese with 11 Mck,M. H., I. J. Basch. B. E. MaIeeff, J. F. Hanagan, frequency (01 = 1.0 rds. asti tic component G’ (dyn/cm2). and V. H. Holsinger. 1989. Characterization of natural viscous component G” (dyn/cm*), and complex viscosity and imitation Mozzar~lhcheeses by differential scBI1- q* (poise) plotted verms percentage of strain. nhg calorimetry. J. Dairy Sci. 721976.

Journal of Dairy Science Vol. 73, No. 7, 1990