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Composition and Quality of Cheddar Cheese
Can. Ins. Food Sei. Teehno!. J. Vo!. 22, No. I, pp. 75-79,1989
RESEARCH
Composition and Quality of Cheddar Cheese A.R. Hill Department of Food Science University of Guelph Guelph, Ontario NIG2WI and
L.K. Ferrier Department of Animal and Poultry Science University of Guelph Guelph, Ontario NIG2WI
directe faible (r = 0.57) mais significative (P <.0,001) fut observee entre la texture et la saveur. SM diminua avec I'augmentation de MNFS (p,OO), et MNFS fut correIe directement avec FDM. Les ratios mo-
Abstract Cheddar cheese samples aged 3-12 months were obtained from Ontario and Quebec cheese factories. A total of?3 samples were collected in two lots (38 samples collected in June, 1987 and 35 samples collected in July 1987), graded by an Agriculture Canada cheese grader using a 10 point scale and analyzed for pH, fat, moisture and salt contents. The second lot (35 samples) was also analyzed for calcium, phosphorus and nitrogen content. Mean compositional values (ClJo) and their respective coefficients of variation (CIJo) were: moisture 34,4,4.4; fat 33.5, 4.0; protein 24.2,3.4; salt 1.69, 10.1; calcium 0,76,11.8; phosphorus 0.51,7,8. Regression analysis was used to evaluate relationships between grade scores for both texture and flavour and the following parameters: cheese pH, moisture in the nonfat substance (MNFS), salt in the moisture (SM), fat in the dry matter (FDM) calcium and phosphorus, None of the models tested were useful predictors of cheese quality, There was a weak (r = 0.57) but significant (p <0,001) direct relationship between texture and f1avor scores, SM decreased with increasing MNFS (p <0.(01), and MNFS correlated directly with FDM, Molar ratios of calcium to phosphorus were inversely related to calcium content.
Introduction
Resume Des echantillons de from age cheddar ages de 3 a 12 mois furent obtenus de fromageries de l'Ontario et du Quebec, Un total de 73 echantillons furent rassembles en deux groupes (38 echantillons recueillis en juin 1987 et 35 echantillons recueillis en juillet 1987), classes par un classificateur de fromaged' Agriculture Canada d 'apres une echelle de 10 points et analyses pour le pH et les teneurs en matiere grasse, en humidite et en sels. Le deuxieme lot (35 echantillons) fut de plus analyse pour les teneurs en calcium, en phosphore et en azote. ~es valeurs de composition moyennes (CIJo) et leurs coefficients respect1fs de variation (CIJo) furent: humidite 34.4, 4.4; matiere grasse 33,5, 4,0; proteine 24.2,3.4; sels 1.69, 10,1; calcium 0,76, 11,8; phosphore 0.51,7,8. L'analyse de regression fut utilisee pour evaluerles rapports entre les notes de classification pour la texture et la saveur et les parametres suivants: pH du fromage, humidite de la fraction degraissee (~NFS), sel dans l'humidite (SM), matiere grasse dans la matiere seche (FDM), calcium et phosphore. Acun de ces modeles etudies s'est avere un predicteur utile de la qualite du fromage. Une relation
The flavor and texture of Cheddar cheese are mainly determined by its chemical composition and the temperature of curing (Lawrence et al., 1984; Lawrence et al., 1983; Lawrence and Gilles, 1980). Increases in both the scale and mechanization of Cheddar cheese manufacture and the need to produce cheese of uniform high quality have prompted interest in the possibility of predicting cheese quality from compositional parameters. In New Zealand all export Cheddar cheese has been graded by compositional analysis since 1978 (Lawrence et al., 1984). The current New Zealand standards for export Cheddar cheese are 50010 minimum FDM (fat in the dry matter), 56010 maximum MNFS (moisture in the non-fat substance), 3.7 - 6.3010 SM (salt in the cheese moisture) and pH 4.95 - 5.20 at 14 days after manufacture (Lawrence and Gilles, 1980). In addition, calcium content is well-recognised as an important factor in determining basic structure and texture of cheese (Lawrence et al., 1984; Adda et al., 1982). Soft ripened cheese such as Feta, Blue and Camembert have low calcium contents (2-2.4010 of non-fat solids) while hard-ripened cheese such as Cheddar (2-2.6010 of non-fat solids) and Swiss (2.63.0% of non-fat solids) have higher levels of calcium (Lawrence et al., 1984). The most important factor in determining calcium loss from cheese curd is the pH at the time of whey draining (Hill et al., 1985; Lawrence et al., 1984). Lawrence and Gilles (1980) suggest that calcium content of Cheddar cheese should be greater
Copyright iD 1989 Canadian Institute of Food Science and Technology
75
than 170mM/kg (0.68070) to ensure optimum firmness. Because phosphates act as calcium chelators and are also important to casein micelle structure (Le., basic cheese structure), the ratio of calcium to phosphorus is also important to cheese structure. Decreasing pH at the time of whey separation causes reduced levels of both calcium and phosphorus in the curd and reduced calcium/phosphorus ratios (Hill et al., 1985; van den Berg and de Vries, 1975; Wongetal., 1978). Whey separated at pH 6.5 had calcium and phosphorous contents of0.022 and 0.45070, respectively, while whey, separated at pH 4.8, had calcium and phosphorous contents of .099 and .074070, respectively (Hill et al., 1985). In Canada, the maximum moisture and minimum fat values for Cheddar cheese are 39070 and 30070, respectively (Canada Agricultural Products Standards Act, 1979), corresponding to MNFS and FDM levels of 56 and 49070. For MNFS, 56070 represents the maximum value for a cheese of legal fat and moisture content in Canada. FDM values can be increased above 49070 by standardizing cheese milk to higher fat contents or decreased by producing drier cheese. Many Canadian cheese manufacturers routinely measure cheese pH, fat, moisture and salt, and could therefore, use pH, FDM, MNFS and SM as quality control parameters if appropriate. The major objective of this investigation was to test the hypothesis that one or more of pH, FDM, MNFS, SM and calcium contents are useful predictors of Cheddar cheese quality.
Materials and Methods Cheddar cheese samples Cheddar cheese, aged 3-12 mo, was collected in 1or 2 kg consumer size packages. The total number of samples was 73, representing eight different cheese plants in Ontario and Quebec. Samples were collected on two separate occasions: 38 samples in the first group collected in June, 1987 and 35 samples in the second group collected in July, 1987. Subsamples for grading and analysis were taken by cutting complete cross sections of each sample. The first cross section (i.e., the end of the rectangular block) was discarded.
Analytical Sub-samples (about 250g cross sections) for compo_ sitional analysis were grated and stored in Whirl Pack bags. Total solids were determined by drying to constant weight in a forced air oven at 95°C for approximately 18 h. pH was measured using a Radiometer research pH meter (Model pH M84) and combination electrode (type GK240 1C). Grated cheese was packed around the electrode in a 30 mL beaker to ensure contact between the pH electrode and the moisture phase of the cheese. Nitrogen and phosphorus were measured after digestion (Thomas et al., 1967) using Technicon autoanalyzers with phosphate and ammonium molybdate indicators, respectively. Calcium and potassium were determined on the same digest with a Varian Model 125 atomic absorption spectrometer. Salt was determined by the Volhard procedure (AOAC, 1975). Mojonnier fat determinations (AOAC, 1975) were performed on 10 mL aliquots of cheese homogenates prepared by homogenizing about 40 g cheese in about 150 g of 7070 sodium citrate solution. Calcium, phosphorus and nitrogen values were obtained for the second group only (35 samples) while moisture, fat, salt and pH were determined on all samples.
Statistical analyses Relationships between each of flavor, texture and total grade scores vs pH, MNFS, FDM, SM and calcium were examined for significant correlations using xy plots and regression analyses. Regression analyses examined each independent variable individually (eg. Grade vs pH) as well as in multiple regression models. Because calcium values were only available for Group 2 data, two models were used as defined below. The
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Cheese grading was performed by an official Agriculture Canada cheese grader. The same official graded both groups of samples. A maximum of 5 points each was assigned to texture and flavor (5 representing excellent cheese and 1 representing poor cheese), giving a maximum total grade score of 10. No intermediate levels were defined by the investigators but the grader voluntarily chose a score of greater than about 2.5 for each of texture and flavor (or a total score of 5) to represent first grade cheese.
o~
76 / Hill and Ferrier
10
2
4 6 8 Grade Score
Fig. I. Percentage frequency distributions of grade scores for 73 samples of Cheddar cheese. Maximum score for flavor plus texture was 10.
J. Inst. Can. Sci. Technol. Aliment. Vol. 22. No. I, 1989
Table I.
Composition of Cheddar cheese produced in Ontario and Quebec. Sample (n)
Minimum
Maximum
Mean
s.d. 1
c.v. 2
(070)
(070)
(070)
(070 )
(070)
73 73 73 35 35 35 73 73 73 73
30.10 31.00 1.31 22.65 0.60 0.45 46.70 46.90 3.60 5.20
38.08 37.80 2.04 26.16 0.95 0.57 55.40 53.50 6.70 5.60
34.40 33.47 1.69 24.20 0.76 0.51 51.68 50.99 4.91 5.36
1.53 1.35 0.17 0.83 0.09 0.04 1.87 1.63 0.56 0.09
4.4 4.0 10.1 3.4 11.8 7.8 3.6 3.2 11.4 I.7
Moisture Fat salt Protein Calcium Phosphorus MNFS FDM SM pH 'standard deviation of variation
2coe fficient
first was applied to all the data (73 observations) and the second to Group 2 data only (35 observations). Response = Group pH MNFS FDM SM Response = pH MNFS SM Calcium 2 Regression analyses were performed by SAS program (SAS, 1985) which computed F-values based on Type 1 and Type III sums of squares.
-Results and Discussion Cheese grading The percentage frequency distribution of total grade scores (Figure 1) indicates that 75lrJo ofthe scores were in the range of 4 to 7. The grader reported that most cheese scored at 5 would have been graded first grade (i.e. 92 out of 100) by the official grading system. In the official system, total scores are given out _of 100 but in practice scores greater than 94 are never assigned, scores greater than 93 are rare and because ~heese scoring less than 92 is second grade, a score of :91 is never assigned to avoid controversy. Thus, in practice the official system limits the grader's ability to distinguish between first grade and higher quality levels of Cheddar cheese. Therefore, for this study the 30
o
30
32.
34 36 % Moisture
38
31
33
35 % Fat
grader was asked to use a 10 point scale. Considering that official scores greater than 93 are seldom assigned, it is interesting to note that given a ten point scale, the grader chose a score of about five to represent first grade cheese and readily distinguished quality levels ranging up to 8.5 Regression of flavor scores with texture scores indicated a significant linear relationship (p <0.001) but the correlation coefficient was not high (r = 0.57), indicating other sources of variation.
Cheese composition The range, mean, standard deviation and coefficient of variation for Cheddar cheese components are detailed in Table 1. Bar charts in Figures 2, 3 and 4 illustrate percentage distributions of Cheddar cheese components. Cheese composition data agreed with results obtained by Ng-Kwai-Hang et al. (1988) who reported mean moisture, fat, protein and salt contents of Quebec Cheddar cheese of 37.7, 32.3, 24.0 and 1.5lrJo respectively. It is interesting that we found a mean moisture content of less than 35lrJo considering that a maximum of 39lrJo moisture has been allowed in Canadian Cheddar cheese since 1979. Considerable variations occurred in fat and protein contents. Fat ranged up to 37.8lrJo although the required minimum is 30lrJo. Variation in FDM (c.v. = 3.2 vs4.03 for fat) indicates that variations in fat and protein content are not only due to differences in MNFS but also to incon20
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c: Q) :;, 10
0'
20
u.
10
~
~
1.5
1.7 1.9 % Salt
2.1
23
24 25 26 % Protein
Fig. 2. Percent frequency distributions of moisture, fat and salt contents in 73 samples of Cheddar cheese and protein content (N x 6.38) in 35 samples of Cheddar cheese. Can. Inst. Food Sci. Technol. J. Vol. 22, No. I. 1989
5
o .60
.70
.80
% Calcium
.90
.44
.48
.52
.56
% Phosphorus
Fig. 3. Frequency distributions of calcium and phosphorus contents in 35 samples of Cheddar cheese.
Hill and Ferrier / 77
40
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Cl> :::l
0Cl>
20
;!
10
0.95
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0.90 5.3
4.0
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5.0
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-...
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0.75
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0Cl>
0.70 5
.60 ~
W
~
M
~
g
W
~
MNFS
~
M
FOM
Fig. 4. Frequency distributions of pH, percent salt in the moisture (SM), percent moisture in the nonfat substance, (MNFS) and percent fat in the dry matter, FDM for 73 samples of Cheddar cheese.
sistent standardization of milk protein/fat ratios. This ,,:ould seem to indicate unnecessarily poor yield efficIency unless cheese makers are deliberately standardizing to low protein/fat ratios to enhance quality. Some variation in FDM could also be attributed to natural variation of the ratio of casein nitrogen to total nitrogen in the milk supply. Studies conducted at the Ontario Central Milk Testing Laboratory indicate a range of 59 to 82010 of casein nitrogen in total milk nitrogen for plant milk supplies (Szijarto, 1973). Salt c.ontents showed large variations (c. v. = 10.05) as prevIOusly noted by Kindstedt and Kosikowski (1988). Factors affecting cheese salt absorption have 0.57 • •
••
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Cl. III
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0.51
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Ca/P=1.32 - 0.58 Ca r=0.85, p<0.001
10
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0.49
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••
0.47 0.45
•
• .60
P=0.318 Ca + 0.268 r =0.82 p<0.01
•• .65
.70
.75
.80
.85
.90
.95
% Calcium (Ca) Fig. 5. Relationship between phosphorus and calcium contents for 35 samples of Cheddar cheese. Regression line, observed values and regression equation.
78 / Hill and Ferrier
.65
.70
.75
.80
.85
.90
.95
mM Calcium/kg Cheese Fig. 6. Regression of molar calcium phosphorus ratio (Ca/P) on mM calcium per kg for 35 samples of Cheddar cheese. Regression line, observed values and regression equation.
b~en described (Gilles, 1976; Sutherland, 1974) includmg MNFS and the acidity at salting. Mean calcium and phosphorus levels were 0.76 and 0.51 %,.respectively, withc.v. values of I I.8and 7.8%, respectIvely. The relationship between phosphorus and calcium contents was approximately linear (Figure 5). The molar ratio of calcium to phosphorus (Ca/P) decreased with increasing calcium content ranging from 0.74 at about 150 mM calcium per kg cheese (0.60%)toO.98 at about 240 mM calcium per kg cheese (0.96%) (Figure 6). This result is in agreement with calcium and phosphorus contents of Cheddar cheese from the midwestern U.S.A. reported by Kindstedt and Kosikowski (1988). It also confirms earlier reports that molar Ca/P ratios of cheese whey increased with increasing calcium content (Hill et al., 1985; Van den Berg and de Vries, 1975; Wong et al., 1978). MNFS was significantly correlated with FDM values (p
Cheese grade vs composition Regression analyses of tlavor, texture and grade scores vs pH, MNFS, FDM, SM and calcium showed little correlation between cheese composition and cheese quality. The effect of MNFS as indicated by Model 1 was marginally significant for flavor (p = 0.048 and 0.084 for Type I and Type III sums of squares, respectively) but its effect on total grade score was less significant (p = 0.075 and 0.178 for Type I J. Inst. Can. Sci. Technol. Aliment. Vo!. 22, No. I, 1989
and Type III sums of squares, respectively). Plots of grade scores vs compositional parameters confirmed the lack of correlation. The data also showed no correlation between cheese age (mild, medium or old) and grade score. . These results do not imply that the parameters studied are not important to cheese quality but only that ranges required to affect cheese quality are wider than occurred in our sample population. This range limit may negate the practical value of using composition as an indicator for cheese quality. Such wide ranges in some or all of these parameters may not be acceptable in other cheese. For example, some high moisture cheese such as American type Mozzarella are subject to gas formation in the packages and various off flavors as early as four weeks after manufacture. One likely contributing factor is that SM ratios in this cheese are frequently low «4.0010) due to its high moisture content. The difficulty is that the cheesemaker must control salt content within a narrow range ( <2.0010) to avoid a salty taste while still maintaining an adequate level of SM to control bacterial growth. In effect, he must find the right balance between MNFS and SM values. This relationship is illustrated by the current investigation where MNFS and SM values were correlated (p <0.001, r = 0.59). It also seems likely that calcium content is less critical in Cheddar cheese than in brine-salted cheese, especially in pastafilata and Swiss type cheese. For example, a correlation was observed between a softening defect in Mozzarella cheese and calcium content (unpublished data for commercial cheese; calcium values by atomic absorption, B. McDougal, personal communication). Mozzarella cheese having less than 0.8010 calcium tended to be soft and short in body after 3 to 6 w while cheese having more than 1.2010 calcium tended to be firm and corky. Because pH values in this study did not represent the pH of the cheese when young, it is not surprising that there was no relationship between pH and cheese quality. The pH of Cheddar cheese at 7 - 14 d represents the minimum pH which occurs before proteolysis begins to neutralize cheese acidity. The pH of young Cheddar cheese is determined by the acidity at salting, the SM ratio and the amount of residual lactose (Lawrence and Gilles, 1982; Thomas and Pearce, 1981; Turner and Thomas, 1980).
Conclusion Variations in MNFS, SM, FDM and calcium contents of Cheddar cheese samples selected from 8 cheese factories were large but insufficient to show a correlation with grade scores for cheese texture or flavor. Therefore, this study using samples from eight cheese factories indicates that compositional parameters are of little value in supplementing sensory cheese grading. More data over a longer time period would be required to evaluate the possibility that improved correlations between grade scores and compositional parameters may be realized using within-plant data.
Con. Inst. Food Sei. Teehnol. J. Vol. 22, No. I, 1989
Acknowledgements This work was supported by the Ontario Milk Marketing Board and the Ontario Ministry of Agriculture and Food. We appreciate the technical assistance of Mr. N. Giguere.
References Adda, J., Gripon, J .C. and Vassal, L. 1982. The chemistry of f1avor and texture gen'eration in cheese. Food Chem. 9:115. AOAC. 1975. Official methods of analysis. 12th ed. Association of Official Analytical Chemists, Washington, DC. Canada Agricultural Products Standards Act, 1979. Dairy Products Regulations. Canada Gazette Part 11, Vol. 113, No. 22, p.4260. Gilles, J. 1976. Control of salt in moisture levels in Cheddar cheese. N. Z. J. Dairy Sci. Technol. 11 :219. Hill, A.R., Bullock, D.H, and Irvine, D.M. 1985. Composition of cheese whey: effect of pH and temperature at dipping. Can. Inst. Food Sci. Technol. J. 18:53. Kindstedt, P.S. and Kosikowski, F.V. 1988. Calcium, phosphorus and sodium concentrations in Cheddar cheese. J. Dairy Sci.71:285. Lawrence, R.e., Heap, H.A. and Gilles, J,,1984. A controlled approach to cHeese technology. J: Dairy Sci. 67:1632. Lawrence, R.C. and Gilles, J. 1982. Factors that determine the pH of young Cheddar cheese. N. Z. J. Dairy Sci. Technol. 17: 1. Lawrence, R.C. and Gilles, J. 1980. The assessment of the potential quality of young Cheddar cheese. N. Z. J. Dairy Sci. Technol. 15: 1. Lawrence, R.C., GiBes, J. and Creamer, L.K. 1983. The relationship between cheese texture and f1avor. N.Z. J. Dairy Sci. Technol. 18: 175. Lelievre, J. 1983. Influence of the casein/fat ratio in milk on the moisture in nonfat substances in Cheddar cheese. J. Soc. Dairy Technol. 36:119. Ng-Kwai-Hang, K.F., Moxley, J.E. and Marziali, A.S. 1988. Cheddar cheese composition in some Quebec cheese factories. Can. Inst. FoodSci. Technol. J. 21:80. SAS, 1985. SAS/STAT Guide for Personal Computers. SAS Institute Inc. Box 800, Cary, Ne. Sutherland, B.J. 1974. Control of salt absorption and whey drainage in Cheddar cheese manufacture. Aust. J. Dairy Technol. June. p. 86. Szijarto, L.F. 1973. Variability of casein serum protein and nonprotein nitrogen in plant milk supplies in Ontario. J. Dairy Sci.56:46. Thomas, R.C., Sheard, R.W. and Moyer, J.P. 1967. Comparison of conventional and automatic procedures for nitrogen, phosphorus and potassium analysis of plant material using a single digestion. Agronomy J. 59:240. Thomas, T.D. and Pearce, K.N. 1981. Influence of salt on lactose fermentation and proteolysis in Cheddar cheese. N. Z. J. Dairy Sci. Technol. 16:253. Turner, K.W. and Thomas, T.D. 1980. Lactose fermentation in Cheddar cheese and the effect of salt. N. Z. J. Dairy Sci. Technol. 15:265. Van den Berg, G. and de Vries, E. 1975. Whey composition during the course of cheese manufacture as affected by the amount of starter and curd washing water. Neth. Milk Dairy J. 29: 181. Wong, N.P., LaCrois, D.E. and McDonough, F.E. 1978. Minerals in whey and whey fractions. J. Dairy Sci. 61 :1708. Submitted July 19,1988 Revised September 7,1988 Accepted September 15, 1988
Hill and Ferrier / 79
RESEARCH
Composition and Quality of Cheddar Cheese A.R. Hill Department of Food Science University of Guelph Guelph, Ontario NIG2WI and
L.K. Ferrier Department of Animal and Poultry Science University of Guelph Guelph, Ontario NIG2WI
directe faible (r = 0.57) mais significative (P <.0,001) fut observee entre la texture et la saveur. SM diminua avec I'augmentation de MNFS (p,OO), et MNFS fut correIe directement avec FDM. Les ratios mo-
Abstract Cheddar cheese samples aged 3-12 months were obtained from Ontario and Quebec cheese factories. A total of?3 samples were collected in two lots (38 samples collected in June, 1987 and 35 samples collected in July 1987), graded by an Agriculture Canada cheese grader using a 10 point scale and analyzed for pH, fat, moisture and salt contents. The second lot (35 samples) was also analyzed for calcium, phosphorus and nitrogen content. Mean compositional values (ClJo) and their respective coefficients of variation (CIJo) were: moisture 34,4,4.4; fat 33.5, 4.0; protein 24.2,3.4; salt 1.69, 10.1; calcium 0,76,11.8; phosphorus 0.51,7,8. Regression analysis was used to evaluate relationships between grade scores for both texture and flavour and the following parameters: cheese pH, moisture in the nonfat substance (MNFS), salt in the moisture (SM), fat in the dry matter (FDM) calcium and phosphorus, None of the models tested were useful predictors of cheese quality, There was a weak (r = 0.57) but significant (p <0,001) direct relationship between texture and f1avor scores, SM decreased with increasing MNFS (p <0.(01), and MNFS correlated directly with FDM, Molar ratios of calcium to phosphorus were inversely related to calcium content.
Introduction
Resume Des echantillons de from age cheddar ages de 3 a 12 mois furent obtenus de fromageries de l'Ontario et du Quebec, Un total de 73 echantillons furent rassembles en deux groupes (38 echantillons recueillis en juin 1987 et 35 echantillons recueillis en juillet 1987), classes par un classificateur de fromaged' Agriculture Canada d 'apres une echelle de 10 points et analyses pour le pH et les teneurs en matiere grasse, en humidite et en sels. Le deuxieme lot (35 echantillons) fut de plus analyse pour les teneurs en calcium, en phosphore et en azote. ~es valeurs de composition moyennes (CIJo) et leurs coefficients respect1fs de variation (CIJo) furent: humidite 34.4, 4.4; matiere grasse 33,5, 4,0; proteine 24.2,3.4; sels 1.69, 10,1; calcium 0,76, 11,8; phosphore 0.51,7,8. L'analyse de regression fut utilisee pour evaluerles rapports entre les notes de classification pour la texture et la saveur et les parametres suivants: pH du fromage, humidite de la fraction degraissee (~NFS), sel dans l'humidite (SM), matiere grasse dans la matiere seche (FDM), calcium et phosphore. Acun de ces modeles etudies s'est avere un predicteur utile de la qualite du fromage. Une relation
The flavor and texture of Cheddar cheese are mainly determined by its chemical composition and the temperature of curing (Lawrence et al., 1984; Lawrence et al., 1983; Lawrence and Gilles, 1980). Increases in both the scale and mechanization of Cheddar cheese manufacture and the need to produce cheese of uniform high quality have prompted interest in the possibility of predicting cheese quality from compositional parameters. In New Zealand all export Cheddar cheese has been graded by compositional analysis since 1978 (Lawrence et al., 1984). The current New Zealand standards for export Cheddar cheese are 50010 minimum FDM (fat in the dry matter), 56010 maximum MNFS (moisture in the non-fat substance), 3.7 - 6.3010 SM (salt in the cheese moisture) and pH 4.95 - 5.20 at 14 days after manufacture (Lawrence and Gilles, 1980). In addition, calcium content is well-recognised as an important factor in determining basic structure and texture of cheese (Lawrence et al., 1984; Adda et al., 1982). Soft ripened cheese such as Feta, Blue and Camembert have low calcium contents (2-2.4010 of non-fat solids) while hard-ripened cheese such as Cheddar (2-2.6010 of non-fat solids) and Swiss (2.63.0% of non-fat solids) have higher levels of calcium (Lawrence et al., 1984). The most important factor in determining calcium loss from cheese curd is the pH at the time of whey draining (Hill et al., 1985; Lawrence et al., 1984). Lawrence and Gilles (1980) suggest that calcium content of Cheddar cheese should be greater
Copyright iD 1989 Canadian Institute of Food Science and Technology
75
than 170mM/kg (0.68070) to ensure optimum firmness. Because phosphates act as calcium chelators and are also important to casein micelle structure (Le., basic cheese structure), the ratio of calcium to phosphorus is also important to cheese structure. Decreasing pH at the time of whey separation causes reduced levels of both calcium and phosphorus in the curd and reduced calcium/phosphorus ratios (Hill et al., 1985; van den Berg and de Vries, 1975; Wongetal., 1978). Whey separated at pH 6.5 had calcium and phosphorous contents of0.022 and 0.45070, respectively, while whey, separated at pH 4.8, had calcium and phosphorous contents of .099 and .074070, respectively (Hill et al., 1985). In Canada, the maximum moisture and minimum fat values for Cheddar cheese are 39070 and 30070, respectively (Canada Agricultural Products Standards Act, 1979), corresponding to MNFS and FDM levels of 56 and 49070. For MNFS, 56070 represents the maximum value for a cheese of legal fat and moisture content in Canada. FDM values can be increased above 49070 by standardizing cheese milk to higher fat contents or decreased by producing drier cheese. Many Canadian cheese manufacturers routinely measure cheese pH, fat, moisture and salt, and could therefore, use pH, FDM, MNFS and SM as quality control parameters if appropriate. The major objective of this investigation was to test the hypothesis that one or more of pH, FDM, MNFS, SM and calcium contents are useful predictors of Cheddar cheese quality.
Materials and Methods Cheddar cheese samples Cheddar cheese, aged 3-12 mo, was collected in 1or 2 kg consumer size packages. The total number of samples was 73, representing eight different cheese plants in Ontario and Quebec. Samples were collected on two separate occasions: 38 samples in the first group collected in June, 1987 and 35 samples in the second group collected in July, 1987. Subsamples for grading and analysis were taken by cutting complete cross sections of each sample. The first cross section (i.e., the end of the rectangular block) was discarded.
Analytical Sub-samples (about 250g cross sections) for compo_ sitional analysis were grated and stored in Whirl Pack bags. Total solids were determined by drying to constant weight in a forced air oven at 95°C for approximately 18 h. pH was measured using a Radiometer research pH meter (Model pH M84) and combination electrode (type GK240 1C). Grated cheese was packed around the electrode in a 30 mL beaker to ensure contact between the pH electrode and the moisture phase of the cheese. Nitrogen and phosphorus were measured after digestion (Thomas et al., 1967) using Technicon autoanalyzers with phosphate and ammonium molybdate indicators, respectively. Calcium and potassium were determined on the same digest with a Varian Model 125 atomic absorption spectrometer. Salt was determined by the Volhard procedure (AOAC, 1975). Mojonnier fat determinations (AOAC, 1975) were performed on 10 mL aliquots of cheese homogenates prepared by homogenizing about 40 g cheese in about 150 g of 7070 sodium citrate solution. Calcium, phosphorus and nitrogen values were obtained for the second group only (35 samples) while moisture, fat, salt and pH were determined on all samples.
Statistical analyses Relationships between each of flavor, texture and total grade scores vs pH, MNFS, FDM, SM and calcium were examined for significant correlations using xy plots and regression analyses. Regression analyses examined each independent variable individually (eg. Grade vs pH) as well as in multiple regression models. Because calcium values were only available for Group 2 data, two models were used as defined below. The
40 >- 30 c: (1) (.)
::s
eT
(1)
20
~
Grading
LL
Cheese grading was performed by an official Agriculture Canada cheese grader. The same official graded both groups of samples. A maximum of 5 points each was assigned to texture and flavor (5 representing excellent cheese and 1 representing poor cheese), giving a maximum total grade score of 10. No intermediate levels were defined by the investigators but the grader voluntarily chose a score of greater than about 2.5 for each of texture and flavor (or a total score of 5) to represent first grade cheese.
o~
76 / Hill and Ferrier
10
2
4 6 8 Grade Score
Fig. I. Percentage frequency distributions of grade scores for 73 samples of Cheddar cheese. Maximum score for flavor plus texture was 10.
J. Inst. Can. Sci. Technol. Aliment. Vol. 22. No. I, 1989
Table I.
Composition of Cheddar cheese produced in Ontario and Quebec. Sample (n)
Minimum
Maximum
Mean
s.d. 1
c.v. 2
(070)
(070)
(070)
(070 )
(070)
73 73 73 35 35 35 73 73 73 73
30.10 31.00 1.31 22.65 0.60 0.45 46.70 46.90 3.60 5.20
38.08 37.80 2.04 26.16 0.95 0.57 55.40 53.50 6.70 5.60
34.40 33.47 1.69 24.20 0.76 0.51 51.68 50.99 4.91 5.36
1.53 1.35 0.17 0.83 0.09 0.04 1.87 1.63 0.56 0.09
4.4 4.0 10.1 3.4 11.8 7.8 3.6 3.2 11.4 I.7
Moisture Fat salt Protein Calcium Phosphorus MNFS FDM SM pH 'standard deviation of variation
2coe fficient
first was applied to all the data (73 observations) and the second to Group 2 data only (35 observations). Response = Group pH MNFS FDM SM Response = pH MNFS SM Calcium 2 Regression analyses were performed by SAS program (SAS, 1985) which computed F-values based on Type 1 and Type III sums of squares.
-Results and Discussion Cheese grading The percentage frequency distribution of total grade scores (Figure 1) indicates that 75lrJo ofthe scores were in the range of 4 to 7. The grader reported that most cheese scored at 5 would have been graded first grade (i.e. 92 out of 100) by the official grading system. In the official system, total scores are given out _of 100 but in practice scores greater than 94 are never assigned, scores greater than 93 are rare and because ~heese scoring less than 92 is second grade, a score of :91 is never assigned to avoid controversy. Thus, in practice the official system limits the grader's ability to distinguish between first grade and higher quality levels of Cheddar cheese. Therefore, for this study the 30
o
30
32.
34 36 % Moisture
38
31
33
35 % Fat
grader was asked to use a 10 point scale. Considering that official scores greater than 93 are seldom assigned, it is interesting to note that given a ten point scale, the grader chose a score of about five to represent first grade cheese and readily distinguished quality levels ranging up to 8.5 Regression of flavor scores with texture scores indicated a significant linear relationship (p <0.001) but the correlation coefficient was not high (r = 0.57), indicating other sources of variation.
Cheese composition The range, mean, standard deviation and coefficient of variation for Cheddar cheese components are detailed in Table 1. Bar charts in Figures 2, 3 and 4 illustrate percentage distributions of Cheddar cheese components. Cheese composition data agreed with results obtained by Ng-Kwai-Hang et al. (1988) who reported mean moisture, fat, protein and salt contents of Quebec Cheddar cheese of 37.7, 32.3, 24.0 and 1.5lrJo respectively. It is interesting that we found a mean moisture content of less than 35lrJo considering that a maximum of 39lrJo moisture has been allowed in Canadian Cheddar cheese since 1979. Considerable variations occurred in fat and protein contents. Fat ranged up to 37.8lrJo although the required minimum is 30lrJo. Variation in FDM (c.v. = 3.2 vs4.03 for fat) indicates that variations in fat and protein content are not only due to differences in MNFS but also to incon20
37
40
>- 15 u
~
30
!
c: Q) :;, 10
0'
20
u.
10
~
~
1.5
1.7 1.9 % Salt
2.1
23
24 25 26 % Protein
Fig. 2. Percent frequency distributions of moisture, fat and salt contents in 73 samples of Cheddar cheese and protein content (N x 6.38) in 35 samples of Cheddar cheese. Can. Inst. Food Sci. Technol. J. Vol. 22, No. I. 1989
5
o .60
.70
.80
% Calcium
.90
.44
.48
.52
.56
% Phosphorus
Fig. 3. Frequency distributions of calcium and phosphorus contents in 35 samples of Cheddar cheese.
Hill and Ferrier / 77
40
1.00
•
>u
c:
Cl> :::l
0Cl>
20
;!
10
0.95
•• •
0.90 5.3
4.0
5.5
5.0
6.0
7.0
Q.
-...
SM
pH
ca
..
•
.t
• • • ••• •
•
•
•• • • •• •
0.85
0
•••
0.80 >- 15 u
0.75
c:
Cl> :::l
0Cl>
0.70 5
.60 ~
W
~
M
~
g
W
~
MNFS
~
M
FOM
Fig. 4. Frequency distributions of pH, percent salt in the moisture (SM), percent moisture in the nonfat substance, (MNFS) and percent fat in the dry matter, FDM for 73 samples of Cheddar cheese.
sistent standardization of milk protein/fat ratios. This ,,:ould seem to indicate unnecessarily poor yield efficIency unless cheese makers are deliberately standardizing to low protein/fat ratios to enhance quality. Some variation in FDM could also be attributed to natural variation of the ratio of casein nitrogen to total nitrogen in the milk supply. Studies conducted at the Ontario Central Milk Testing Laboratory indicate a range of 59 to 82010 of casein nitrogen in total milk nitrogen for plant milk supplies (Szijarto, 1973). Salt c.ontents showed large variations (c. v. = 10.05) as prevIOusly noted by Kindstedt and Kosikowski (1988). Factors affecting cheese salt absorption have 0.57 • •
••
Q.
...0
Cl. III
•
• • •• • • • • •• • • •• ••
0.51
0
.£:
Q.
•
• 0.53
III ::;, ~
••
•
0.55
-
•
Ca/P=1.32 - 0.58 Ca r=0.85, p<0.001
10
.t ;!
• •
0.49
0:::!!
••
0.47 0.45
•
• .60
P=0.318 Ca + 0.268 r =0.82 p<0.01
•• .65
.70
.75
.80
.85
.90
.95
% Calcium (Ca) Fig. 5. Relationship between phosphorus and calcium contents for 35 samples of Cheddar cheese. Regression line, observed values and regression equation.
78 / Hill and Ferrier
.65
.70
.75
.80
.85
.90
.95
mM Calcium/kg Cheese Fig. 6. Regression of molar calcium phosphorus ratio (Ca/P) on mM calcium per kg for 35 samples of Cheddar cheese. Regression line, observed values and regression equation.
b~en described (Gilles, 1976; Sutherland, 1974) includmg MNFS and the acidity at salting. Mean calcium and phosphorus levels were 0.76 and 0.51 %,.respectively, withc.v. values of I I.8and 7.8%, respectIvely. The relationship between phosphorus and calcium contents was approximately linear (Figure 5). The molar ratio of calcium to phosphorus (Ca/P) decreased with increasing calcium content ranging from 0.74 at about 150 mM calcium per kg cheese (0.60%)toO.98 at about 240 mM calcium per kg cheese (0.96%) (Figure 6). This result is in agreement with calcium and phosphorus contents of Cheddar cheese from the midwestern U.S.A. reported by Kindstedt and Kosikowski (1988). It also confirms earlier reports that molar Ca/P ratios of cheese whey increased with increasing calcium content (Hill et al., 1985; Van den Berg and de Vries, 1975; Wong et al., 1978). MNFS was significantly correlated with FDM values (p
Cheese grade vs composition Regression analyses of tlavor, texture and grade scores vs pH, MNFS, FDM, SM and calcium showed little correlation between cheese composition and cheese quality. The effect of MNFS as indicated by Model 1 was marginally significant for flavor (p = 0.048 and 0.084 for Type I and Type III sums of squares, respectively) but its effect on total grade score was less significant (p = 0.075 and 0.178 for Type I J. Inst. Can. Sci. Technol. Aliment. Vo!. 22, No. I, 1989
and Type III sums of squares, respectively). Plots of grade scores vs compositional parameters confirmed the lack of correlation. The data also showed no correlation between cheese age (mild, medium or old) and grade score. . These results do not imply that the parameters studied are not important to cheese quality but only that ranges required to affect cheese quality are wider than occurred in our sample population. This range limit may negate the practical value of using composition as an indicator for cheese quality. Such wide ranges in some or all of these parameters may not be acceptable in other cheese. For example, some high moisture cheese such as American type Mozzarella are subject to gas formation in the packages and various off flavors as early as four weeks after manufacture. One likely contributing factor is that SM ratios in this cheese are frequently low «4.0010) due to its high moisture content. The difficulty is that the cheesemaker must control salt content within a narrow range ( <2.0010) to avoid a salty taste while still maintaining an adequate level of SM to control bacterial growth. In effect, he must find the right balance between MNFS and SM values. This relationship is illustrated by the current investigation where MNFS and SM values were correlated (p <0.001, r = 0.59). It also seems likely that calcium content is less critical in Cheddar cheese than in brine-salted cheese, especially in pastafilata and Swiss type cheese. For example, a correlation was observed between a softening defect in Mozzarella cheese and calcium content (unpublished data for commercial cheese; calcium values by atomic absorption, B. McDougal, personal communication). Mozzarella cheese having less than 0.8010 calcium tended to be soft and short in body after 3 to 6 w while cheese having more than 1.2010 calcium tended to be firm and corky. Because pH values in this study did not represent the pH of the cheese when young, it is not surprising that there was no relationship between pH and cheese quality. The pH of Cheddar cheese at 7 - 14 d represents the minimum pH which occurs before proteolysis begins to neutralize cheese acidity. The pH of young Cheddar cheese is determined by the acidity at salting, the SM ratio and the amount of residual lactose (Lawrence and Gilles, 1982; Thomas and Pearce, 1981; Turner and Thomas, 1980).
Conclusion Variations in MNFS, SM, FDM and calcium contents of Cheddar cheese samples selected from 8 cheese factories were large but insufficient to show a correlation with grade scores for cheese texture or flavor. Therefore, this study using samples from eight cheese factories indicates that compositional parameters are of little value in supplementing sensory cheese grading. More data over a longer time period would be required to evaluate the possibility that improved correlations between grade scores and compositional parameters may be realized using within-plant data.
Con. Inst. Food Sei. Teehnol. J. Vol. 22, No. I, 1989
Acknowledgements This work was supported by the Ontario Milk Marketing Board and the Ontario Ministry of Agriculture and Food. We appreciate the technical assistance of Mr. N. Giguere.
References Adda, J., Gripon, J .C. and Vassal, L. 1982. The chemistry of f1avor and texture gen'eration in cheese. Food Chem. 9:115. AOAC. 1975. Official methods of analysis. 12th ed. Association of Official Analytical Chemists, Washington, DC. Canada Agricultural Products Standards Act, 1979. Dairy Products Regulations. Canada Gazette Part 11, Vol. 113, No. 22, p.4260. Gilles, J. 1976. Control of salt in moisture levels in Cheddar cheese. N. Z. J. Dairy Sci. Technol. 11 :219. Hill, A.R., Bullock, D.H, and Irvine, D.M. 1985. Composition of cheese whey: effect of pH and temperature at dipping. Can. Inst. Food Sci. Technol. J. 18:53. Kindstedt, P.S. and Kosikowski, F.V. 1988. Calcium, phosphorus and sodium concentrations in Cheddar cheese. J. Dairy Sci.71:285. Lawrence, R.e., Heap, H.A. and Gilles, J,,1984. A controlled approach to cHeese technology. J: Dairy Sci. 67:1632. Lawrence, R.C. and Gilles, J. 1982. Factors that determine the pH of young Cheddar cheese. N. Z. J. Dairy Sci. Technol. 17: 1. Lawrence, R.C. and Gilles, J. 1980. The assessment of the potential quality of young Cheddar cheese. N. Z. J. Dairy Sci. Technol. 15: 1. Lawrence, R.C., GiBes, J. and Creamer, L.K. 1983. The relationship between cheese texture and f1avor. N.Z. J. Dairy Sci. Technol. 18: 175. Lelievre, J. 1983. Influence of the casein/fat ratio in milk on the moisture in nonfat substances in Cheddar cheese. J. Soc. Dairy Technol. 36:119. Ng-Kwai-Hang, K.F., Moxley, J.E. and Marziali, A.S. 1988. Cheddar cheese composition in some Quebec cheese factories. Can. Inst. FoodSci. Technol. J. 21:80. SAS, 1985. SAS/STAT Guide for Personal Computers. SAS Institute Inc. Box 800, Cary, Ne. Sutherland, B.J. 1974. Control of salt absorption and whey drainage in Cheddar cheese manufacture. Aust. J. Dairy Technol. June. p. 86. Szijarto, L.F. 1973. Variability of casein serum protein and nonprotein nitrogen in plant milk supplies in Ontario. J. Dairy Sci.56:46. Thomas, R.C., Sheard, R.W. and Moyer, J.P. 1967. Comparison of conventional and automatic procedures for nitrogen, phosphorus and potassium analysis of plant material using a single digestion. Agronomy J. 59:240. Thomas, T.D. and Pearce, K.N. 1981. Influence of salt on lactose fermentation and proteolysis in Cheddar cheese. N. Z. J. Dairy Sci. Technol. 16:253. Turner, K.W. and Thomas, T.D. 1980. Lactose fermentation in Cheddar cheese and the effect of salt. N. Z. J. Dairy Sci. Technol. 15:265. Van den Berg, G. and de Vries, E. 1975. Whey composition during the course of cheese manufacture as affected by the amount of starter and curd washing water. Neth. Milk Dairy J. 29: 181. Wong, N.P., LaCrois, D.E. and McDonough, F.E. 1978. Minerals in whey and whey fractions. J. Dairy Sci. 61 :1708. Submitted July 19,1988 Revised September 7,1988 Accepted September 15, 1988
Hill and Ferrier / 79