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Effects of protein and fat levels in milk on cheese and whey compositions
Food Research International 25 (1992) 445-451
Effects of protein and fat levels in milk on cheese and whey compositions Y. Lou & K. F. Ng-Kwai-Hang* Department of Animal Science, McGill University, Macdonald Campus, 21,l I I Lakeshore Road, Ste Anne de Bellevue, Quebec, Canada H9X ICO
Bulk tank milk was standardised to six levels of fat (3.0, 3.2, 3.4, 3.6, 3.8, 4.0%) and similarly to six levels of protein, thus giving a total of 36 combinations in composition. Milk was analyzed for total solids, fat, protein, casein, lactose and somatic cell count and was used to make laboratory-scale cheese. Cheese samples from each batch were assayed for total solids, fat, protein and salt. Losses of milk components in the whey were also determined. Least squares analysis of data indicated that higher protein level in milk was associated with higher protein and lower fat contents in cheese. This was accompanied by lower total solids (higher moisture) in cheese. Inversely, higher fat level in milk gave higher fat and lower protein and moisture contents in cheese. Higher fat level in milk resulted in lower retention of fat in cheese and more fat losses in the whey. Higher protein level in milk gave higher fat retention in cheese and less fat losses in the whey. Regression analysis showed that cheese fat increased by 4.22%, while cheese protein decreased by 2.61% for every percentage increase in milk fat. Cheese protein increased by 2.35%, while cheese fat decreased by 6.14% per percentage increase in milk protein. Milk with protein to fat ratio close to 0.9 would produce a minimum of 50% fat in the dry matter of cheese. Keyw0rd.y: protein and fat in milk, cheese composition,
whey composition.
is 37% moisture (63% total solids) with a minimum of 50% fat in the dry matter. Cheese-making efficiencies are reflected by the extent of losses of milk components in the whey. Several workers (Barbano & Sherbon, 1984; Ng-Kwai-Hang et al., 1987) reported that lower than expected cheese-making efficiency found in some cheese factories was attributed to low milk casein in relation to fat and this resulted in excessive fat losses in the whey during cheese manufacturing. While the previous article (Lou and Ng-KwaiHang, 1992) reported on effects of altering milk fat and protein on cheese yield potential, the present study investigates, under laboratory conditions, the extent to which cheese composition and distribution of milk components in cheese and whey are altered by adjusting content of protein and fat in the milk used for cheese-making.
INTRODUCTION Efficient incorporation of milk components into cheese is of great interest to the cheese-maker because the quality of the resulting product will determine its commercial value. In the process of making Cheddar cheese, more than 90% of the fat and casein in milk contribute to the cheese solids. Amounts of minerals, whey protein, and lactose in milk which are retained in cheese during its manufacture depend on cheese moisture content (Emmons et al., 1990) as well as the manufacturing practices. The quality of a Cheddar cheese is based on its content of major components, including moisture, fat, protein and salt. To maintain uniformity in the product from one batch to another, and to conform to certain minimum legal limits, it is essential that cheese composition is carefully controlled. For example, the target value for Cheddar cheese
MATERIALS
*To whom all correspondence should be addressed.
Throughout
Food Research International 0963-9969/92/$05.00 0 1992 Canadian Institute of Food Science and Technology
and 445
AND METHODS the study, procedures for obtaining milk to six levels of fat (3.0-
standardising
446
Y. Lou, K. F. Ng-Kwai-Hang
4.0%) and six levels of protein (3.0-40%), cheesemaking under laboratory conditions, collection and weighing of cheese and whey samples, analysing components in milk, cheese and whey were the same as previously described (Lou & Ng-KwaiHang, 1992). Briefly, bulk tank milk from the college farm was nartiallv skimmed and then adiusted to contain &six dikerent levels of fat (3~@-4~0%) with cream-rich milk. Within each of the fat levels, the milk was also adjusted to contain six levels of protein (3.040%) with instant skim milk powder. The 36 possible combinations of adjusted milk samples in terms of fat and protein contents were used to make Cheddar-type cheese under standardised laboratory conditions (Lou & Ng-KwaiHang, 1992). After overnight pressing, cheese curds were weighed, grated, hermetically sealed in a plastic bag, and kept frozen at -10°C pending chemical analyses. Subsamples of initial milk used and of resulting whey from each batch of cheese were taken for chemical analyses. Milk, cheese, and whey samples were analysed in duplicate for total solids, fat, and protein as described previously (Lou & Ng-Kwai-Hang, 1992). Milk was also analysed for lactose, casein, non-casein protein (NCP) and somatic cell count (SCC) whereas cheese was also analysed for salt content. Statistical analysis The data were analysed by least squares methods in statistical models which included fat levels, protein levels, casein to fat ratio, and protein to fat ratio as fixed effects. Milk concentration in total solids, casein, NAP, lactose, XC, and initial pH of milk were included in the model as covariates to test the significance and obtain regression coefficients for these parameters. Six subclasses were used for levels of fat and also six subclasses for levels of milk protein. Twelve subclasses were used for casein to fat ratio and protein to fat ratio.
RESULTS AND DISCUSSION Cheese and whey composition The overall means and standard deviations for cheese and whey components for a total of 596 lots of cheese included in this study are presented in Table 1. Total solids in cheese varied from 55.87 to 60.61% (i.e. moisture of 39.394l.13%) in
Table 1. Overall means (x) and standard deviations (SD) for cheeseandwhey compositions for au samples included in this study
Product and component
8
SD
Cheese Total solids (%) Fat (%) Protein (%j Salt (%)’ ’ Fat in dry matter (%) Protein in dry matter (%) Moisture in non-fat substances
58.41 58.64 24.34 0.92 49.00 41.70 58.29
2.07 2.72 1.53 0.22 3.67 2.99 2.12
7.64 0.26 0.95
0.68 0.08 0.09
Whey Total solids (%) Fat (%) Protein (%)
the 36 combinations of milk fat and protein levels. If the values for total solids in cheese were compared within a given milk fat level, it was found that total solids in cheese decreased as protein content of milk increased, whereas within a milk protein level, cheese total solids increased proportionally with milk fat. It was also found that the highest protein content (4.0%) in milk resulted in low total solids in cheese while the lowest protein content in milk (3.0%) gave the highest cheese solids (58.89-60.61%). This situation reveals that higher milk protein, specifically casein, is associated with higher moisture content in cheese (Gilles & Lawrence, 1985). In cheese, casein is associated with 2.5 times its weight of water (Emmons et al., 1990). The ranges of fat and protein contents in cheese were 23.61-33.73% and 21.7627.12%, respectively. It was observed that within a given milk fat level, as protein concentration increased, fat in cheese decreased while protein in cheese increased. Fat content in cheese increased and protein content in cheese decreased with increasing fat concentration of milk for a given protein level. This is because casein and fat constitute more than 90% of the cheese total solids and they are negatively correlated (Ng-Kwai-Hang, 1990). Therefore, an increase of protein in cheese is accompanied by a decrease in fat content and vice versa. The salt contents of cheese in all levels of milk fat and protein ranged from 0.76 to 1.11% and were below the targeted value of 1.5%. Salt was added to give a final concentration of 1.5% in the cheese curd before pressing and losses in the liquid during the pressing process resulted in a cheese containing less than 1.5% salt. Variations in fat on a dry matter basis (FDM) and protein in cheese total solids (PDM) for the 36 combinations of milk and fat protein levels fol-
EfSects of protein and fat levels in milk on cheese and whey compositions
lowed similar trends as fat and protein contents in cheese. Milk with a protein to fat ratio of higher than 0.95 produced cheese containing less than 50% FDM. Although there is no legal limit for protein content of cheese, PDM is usually approximately 40% in cheese (Barbano & Sherbon, 1984; Ng-Kwai-Hang et al., 1988). A high PDM will result in a cheese that appears to be drier than what the moisture content indicates. Results in cheese composition for the 36 milk fat/protein combinations suggest that milk containing 3440% fat and 3.2-3.6% protein will produce cheese of a desirable composition. Values for moisture in nonfat substances (MNFS), with a range of 56.2360.53% for all combinations of fat and protein levels, were higher than some literature values (Barbano & Sherbon, 1984; Gilles & Lawrence, 1985). This was due to the higher moisture content of cheese (39.39-44.13%) attained in the present study, particularly for milk compositional combinations where protein levels were high in relation to fat. Overall means and standard deviations of whey composition are also presented in Table 1. Total solids in whey ranged from 6.57 to 8.76% in the 36 combinations of milk fat and protein levels. It was observed that total solids of whey increased as protein content of milk increased for a given fat level. This may be explained by the fact that the increase of protein content in milk was accompanied
447
by an increase of lactose content due to the addition of skim milk powder. For a given protein level, values for total solids in whey increased slightly with increased fat content in milk. Fat content in whey ranged from 0.18 to 0.37% in all combinations of milk fat and protein levels. Fat in whey slightly changed among six protein levels within each of fat levels. However, fat in whey increased as milk fat increased. This indicates that, for a given level, increasing milk fat will result in greater loss of fat in the whey during cheese-making because there is not enough casein to associate with fat. Protein content in whey varied from 0.83 to 1.04% for all milk fat and protein levels. It was found that protein in the whey increased with increasing milk protein for a given fat level, while it was changed slightly with an increase in milk fat within a protein level. This situation may be attributed to an increasing amount of NCP in the milk through the addition of SMP to increase milk protein. Recoveries of milk components in the cheese
Means and standard deviations for total solids, fat and casein of milk recovered in cheese in the 36 combinations of milk fat and protein levels were calculated and are shown in Table 2. Overall means were 49.83, 90.66 and 96.81%, for recoveries of total solids, fat and casein in cheese, respec-
Table 2. Recoveries of milk components in cheese for 36 combinations of milk fat and protein levels Milk fat level
Milk protein
Recovery m 2
z’?
level 4
3
5
6
SD
J?
SD
2
SD
2
SD
x
SD
J?
SD
1 Total solids Fat Casein
48.70 90.67 97.25
0.99 3.20 3.05
49.38 91.77 95.08
0.86 3.03 3.62
48.54 91.79 95.79
0.92 3.04 5.65
48.04 92.77 98.38
1.31 2.92 4.81
47.87 94.42 99.92
0.92 2.91 2.47
46.80 93.46 98.07
0.75 4.94 5.35
2 Total solids Fat Casein
51.01 92.17 94.17
1.57 2.72 5.27
50.14 91.80 96.50
1.46 2.04 4.82
50.18 91.80 96.45
1.72 2.04 3.94
49.33 91.42 97.00
2.11 2.87 2.76
49.66 93.47 95.73
1.35 2.03 2.15
48.97 92.40 97.50
2.10 2.59 2.07
3 Total solids Fat Casein
49.22 89.06 97.65
2.24 4.70 5.30
50.06 90.19 96.22
1.26 2.13 5.47
49.92 91.05 94.38
1.81 2.84 3.50
49.00 89.33 96.58
1.72 3.20 3.51
48.79 91.50 97.46
1.80 3.24 3.64
48.68 91.61 96.89
2.16 2.87 4.01
4 Total solids Fat Casein
50.93 90.06 97.06
1.59 3.08 4.62
50.65 90.48 94.90
1.73 3.78 3.58
50.46 90.79 96.64
1.13 344 4.30
50.00 90.50 97.17
1.05 2.87 4.36
49.77 91.47 96.84
0.99 3.73 3.1 1
48.99 90.90 96.90
1.34 2.73 3.52
5 Total solids Fat Casein
50.87 89.21 99.29
1.57 3.91 5.90
50.92 89.88 98.41
1.23 3.71 4.37
50.76 89.47 97.41
0.87 2.60 4.65
50.03 89.92 97.08
0.56 2.50 4.48
50.49 91.59 97.41
0.95 2.06 4.00
49.10 91.20 97.90
1.29 3.29 2.64
6 Total solids Fat Casein
5144 88.88 99.24
2.13 4.23 4.05
51.64 88.42 96.92
1.40 3.32 530
50.71 89.83 94.33
0.92 4.55 5.02
50.68 89.07 97.87
0.80 2.76 3.07
50.62 89.83 96.67
1.51 3.67 2.95
50.09 89.15 97.31
0.57 2.27 3.88
Y. Lou, K. F. Ng-Kwai-Hang
448
tively. Recovery of total solids in cheese varied from 4680 to 51.44% and decreased slightly as protein content in milk increased within a given fat level but increased with increasing fat content of milk for a given protein level. Although lactose accounted for a greater proportion of milk solids, it did not contribute significantly to the cheese mass. Therefore, milk with a higher protein level used to make cheese resulted in lower recovery of total solids in cheese. In contrast, a higher fat level gave higher recovery of total solids in cheese, since most of the fat in milk contributes to cheese solids. The recovery of milk fat in cheese was in a range of 8894% for the 36 combinations of six levels each of fat and protein. According to Van Slyke’s formula (Van Slyke & Price, 1949), an average of 93% fat recovery could be expected under normal conditions. Most of the values for fat recovery shown in Table 2 are lower than 93%. However, these results are similar to the findings by Lelievre (1983) and Gilles and Lawrence (1985). For a given milk fat content, the recovery of fat in cheese increased with increasing protei content in milk and for a given milk protein content, the fat recovery decreased with increasing fat content in milk. It is likely that the retention of fat in cheese is associated with the contents of protein and fat in milk. Such relationships were also found by Moxley and Ng-Kwai-Hang (1984), and Barbano and Sherbon (1984), who reported that low fat recoveries in cheese were due to a low casein to fat ratio in milk. The values for casein recovery in cheese are in a range of 94101% for all combinations of fat and protein levels. Most of
these values are close to or above 96% recovery predicted by Van Slyke’s formula. At least 4% casein is unavoidably lost in the whey as glycomacropeptide from K-casein (Phelan, 198 1) and proteose-peptone formed as a result of plasmin action on P-casein (Donnelly & Barry, 1983). Therefore a casein recovery of greater than 96% may be due to some of the NCP contributing to the cheese solids. An analysis of variance was carried out to study the influence of milk fat level, milk protein levels, ratios of casein to fat and protein to fat, and other milk components in cheese composition, and the results are summarised in Table 3. Sum of squares in the above table was computed using type III sum of the squares in SAS (1982). In this way, the effect of any factor on cheese composition could be calculated with adjustments being made for the effects of all the other factors included in the model. Milk fat level significantly affected protein 0, I 0.01) and salt (p 5 0.05) contents in cheese but did not have an effect on total solids and fat contents in cheese. Protein to fat ratio significantly influenced (p I 0.01) fat and protein content of cheese. Total solids in milk had significant effects on total solids (p 5 0.05), fat 0, I 0.01) and protein 0, I 0.05) in cheese while casein in milk only influenced (p I 0.05) fat content in cheese. Relationship between milk composition and cheese composition Regression of fat and protein percentages in cheese on milk fat and protein were significant and are
Table 3. Analysis of variance for cheese composition
Source
Sum of squares
df Total solids
Fixed effects Milk fat level Milk protein level Casein/fat Protein/fat Covariutes (milk component) Total solids (%) Casein (%) NAP (%) Lactose (%) Somatic cell count Initial milk pH Error up 2 0.05. bp I 0.01.
Fat
Protein
5 5 11 11
23.67 24.68 33.62 41.07
13.19 12.93 24.20 40.756
16.606 9.40 0.64 34.976
1 1 1 1 1 1
1444” 4.86 11.05 1.98 2.55 0.26
11.036 5.30” 4.34 0.02 0.70 0.13
3.79” 0.58 5.21 0.95 1.72 0
557
1731.20
801.39
547.43
Salt
0.56” 0.42 0.27 0.49 0.02 0 0.15 0 0.01 0.05 25.65
Efsects of protein and fat levels in milk on cheese and whey compositions 35 -
33 -
-be
31 -
T g
2Q-
37 -
5 5 % ha
27 -
25 -
27
b-2.40
b-2.29 b-2.21
b=2.01
b-2.24
i--_:
b-2.77
21 -I-
t 2.0
3.1
3.3
Protein
3.6
3.7
3.9
4.1
in milk(%)
2.9
3.1
3.3
3.5
3.7
3.9
4.1
Fat in Milk(%)
Fig. 1. Regression of fat and protein in cheese on protein
Fig. 2. Regression of fat and protein in cheese on fat content
content of milk for different fat levels. (14, Protein = 3.0%; x, protein = 3.2%; x, protein = 3.4%; -Ef, protein = 3.6%; *, protein = 3.8%; +, protein = 4.0%).
of milk for different rotein levels. (A, Protein = 3.0%; z, protein = 3.2%; G+T protein = 3.4%; B, protein = 3.6%; X, protein =‘3.8%; 0, protein = 4.0%).
presented in Figures 1 and 2. In Figure 1, the fat levels were fixed to test the effect of protein content of milk and protein percentages in cheese for each of fixed fat levels. The analyzed results in Figure 1 show that cheese fat and cheese protein change in opposite directions following an increase in milk protein for each of the fat levels. Cheese protein was positively correlated to milk protein, while cheese fat was negatively correlated. Protein content in cheese increased by 2.01-2.77%, whereas cheese fat decreased by 541-6.67% for every percentage increase in milk protein in different fat levels. In Figure 2, the protein levels were fixed to test the effect of fat content of milk on fat and protein percentages in cheese for each of the fixed protein levels. It was found that fat content in cheese was positively correlated to milk fat and
cheese protein was negatively correlated to milk fat for all protein levels. Fat content in cheese increased by 3.55461% and cheese protein decreased by 2.25-2.89% for an increase of 1% in milk fat in different protein levels. From the results presented in Figures 1 and 2, it was obvious that the change of cheese fat was greater than that of cheese protein following variations in milk fat and protein. This is explained by the fact that increasing the fat in cheese decreased the moisture content in cheese, resulting in higher total solids (Pearce, 1978). Thus, the percentage of fat in cheese increased to a great extent. As protein increased in milk, only casein (80%) of protein) contributed to the cheese, besides, cheese moisture increased with increasing milk protein, resulting in lower total solids.
Y. Lou, K. F. Ng-Kwai-Hang
450
Table 4. Percentage of fat in dry matter of cheese predicted from regression equation, FDM = 5398 + 6GF - 73OP Milk protein
(%)
Milk fat (%)
3.0
3.2
3.4
3.6
3.8
4.0
3.0 3.2 3.4 3.6 3.8 4.0
M 50.87 52.08 53.29 54.50 55.72
48.16 w 50.58 51.79 53.00 54.22
46.66 47.87 m 50.29 51.50 52.72
4516 46.37 47.58 4879 50.00 51.22
43.66 44.87 46.08 47.29 48.50 49.72
42.16 43.37 44.58 45.79 47.00 48.22
Values below the line represent legal limit of 50%.
those
meeting
the minimum
Table 4 shows the values for fat on dry matter in cheese predicted from the equation Y(FDM) = 53.98 + 6.06F - 7,5OP, obtained from regression analysis. From the results, it is obvious that milk with a given percentage of fat can produce different FDM in cheese by changing the percentage of milk protein. For example, milk with 3.6% fat (level 4) and 3.0% protein (level 1) will produce cheese containing 53.29% FDM, whereas milk at the same level of fat and 4.0% protein (level 6) will produce cheese containing only 4579% FDM. Cheese composition is a good indicator of cheese quality. For Cheddar-type cheese, the minimum legal limit is 50% for FDM. In Table 4 it was found that only the combinations of fat and protein below the underlined values gave the legal fat content of cheese. The predicted values in Table 4 were close to actual values as described previously. The combinations of fat and protein levels in milk which gave over 50% FDM in cheese, have a protein to fat ratio below 0.95. This is close to 0.90, indicated by Banks et al. (1984). As the results indicated, milk with a protein to fat ratio greater than 0.95 would produce cheese containing less than 50% FDM. Also, a higher ratio, which means high protein in relation to fat in milk, will produce cheese containing higher moisture because the protein in milk is positively correlated with cheese moisture. On the other hand, if milk with a protein to fat ratio much lower than 0.95, e.g. below 0.85, was used to make cheese, more fat would be lost in the whey since not enough protein was available to associate with fat during cheese curd formation. This would result in economic loss to cheese industries. With the present milk payment formula, prices for milk are paid according to the fat content of milk, but cheese-makers could not achieve maximum profits if no adjustments were made to optimise the protein to fat
ratio. Therefore, in order to obtain good quality cheese and maximum profits, it is suggested that the protein to fat ratio in milk should be 0.90 f 0.05. Losses of milk components in the whey The means and standard deviations for the losses of milk components in the whey for 36 combinations of fat and protein levels were calculated. Overall means were 52.04, 6.46, 24.25% for the losses of total solids, fat, and protein in the whey, respectively. Values for milk total solids lost in the whey during cheese-making varied from 49.40 to 53.95%. In other words, only about 50% of the milk solids, mainly fat, protein and some minerals, contributed to cheese solids. The remaining 50%, mainly lactose, NCP and half of the minerals, were lost in the whey. The means for the loss of fat in the whey were in a range of 5.10-8.06%. Van Slyke’s formula would predict that 7% fat is lost in the whey. In our study, the average value for fat loss (6.46%) was close to the predicted value (7%). However, the average fat loss in the whey should have been approximately 10% if compared with the overall mean of fat recovery in the cheese described above. Gilles and Lawrence (1985) also reported about 10% loss of milk fat in the whey in making Cheddar-type cheese. The low values for fat in whey obtained in our study may be attributed to the filtration used when taking the whey sample from the total volume of whey. Large fat globules were filtered out from the whey. Protein losses in the whey were within the range of 22.07-26.70% and were similar to those reported by Lelievre (1983). The loss of protein in whey can be calculated from NCP and casein in the milk. It is assumed that all of the NCP and 4% of the casein, which is predicted by Van Slyke’s formula, in milk is lost in the whey during cheese-making. The calculated values for the protein loss were in a range of 20.21-26.89% (average value 24.45%) which are within the actual range shown above. Table 5 summarises the analysis of variance performed to investigate the degree of variation in the losses of milk components in whey due to milk fat level, milk protein level, ratios of casein to fat and protein to fat and other milk components. Total solids loss in the whey were affected significantly (p 5 0.01) by milk fat level, milk protein and protein to fat ratio. Fat loss in the whey was influenced significantly (p I 0.01) by fat level, pro-
Efsects of protein
andfat
levels in milk on cheese and whey compositions
Table 5. Analysis of variance for milk component losses in the whey Source
df
Sum of squares Total solids
Fat
5 5 11 11
111.01* 68.33’ 23.54 66.65’
64.436 56.40’ 64-65’ 19.72
8.93 30.67” 19.60 20.36
1 1 1 1 1 1
4.32 3.14 1.08 1.94 0.02 0.04
0.09 0.13 0.69 0.13 3.48 3.38
9.07” 4.66 5.03 0.49 3.01 0.34
557
1450.03
1559.58
--
Protein
Fixed effects
Milk fat level Milk protein level Casein/fat Protein/fat Covariates
(milk component) Total solids (?/a) Casein ((s/o) NCP (%I) Lactose (“A) Somatic cell count Initial milk pH Error
1352.20
up I 0.05 *p IO.01
451
ACKNOWLEDGEMENTS The authors are grateful to the Agropur Cooperative Agro-Alimentaire, Granby, Quebec, for providing starter culture and calf rennet and for its technical assistance. The authors would also like to thank Mr Donald Galbraith and Mr George Destounis for this assistance in performing laboratory analyses. This project was financially supported by Conseil des Recherches en Peche et en Agroalimentaire du Quebec (Project No. 2588).
REFERENCES Banks, J. M., Muir, D. D. & Tamine, A. T. (1984). A comparison of the quality of Cheddar cheese produced from seasonal and standardized milk. J. Sot. Dairy Technol., 37, 88-92.
tein level and casein to fat ratio. The loss of protein in the whey was significantly (p I 0.05) affected by protein level and milk total solids.
CONCLUSIONS Results obtained from this study showed that cheese composition was significantly influenced by the levels of fat and protein in milk, since fat and protein are the two major solid components in the cheese. Higher protein level in milk was associated with higher protein content and lower fat content in cheese. Conversely, higher fat level in milk gave higher fat content and lower protein content in cheese. Casein has the ability to contribute absorbed water to the cheese in addition to its own weight. Therefore, higher protein content of milk resulted in lower total solids in cheese. The levels of fat and protein in milk also influenced the retention of fat in cheese. Higher fat level in milk resulted in lower retention of fat in cheese and more fat losses in the whey. Higher protein level in milk gave higher fat retention in cheese and less fat losses in the whey. From the results of cheese composition, we conclude that in order to obtain a minimum of 50% FDM in cheese, protein to fat ratio in milk should be around 0.9 (or casein to fat ratio around 0.7).
Barbano, D. M. & Sherbon, J. W. (1984). Cheddar cheese yield in New York. J. Dairy Sci., 67, 1873-83. Donnelly, W. J. & Barry, J. G. (1983). Casein compositional studies III. Changes in Irish milk for manufacturing and role of milk proteinase. J. Dairy Res., 50, 433-4 1. Emmons, D. B., Ernstrom, C. A., Lacroix, C. & Verret, P. (1990). Predictive formulas for yield of cheese from composition of milk: A review. J. Dairy Sci., 73, 1365-94. Gilles, J. & Lawrence, R. C. (1985). The yield of cheese. N.Z. J. Dairy Sci. Technol., 20, 205-14.
Lelievre, J. (1983). The influence of the casein to fat ratio in milk on the moisture in the non-fat substance in Cheddar cheese. J. Sot. Dairy Technol., 36, 119-20. Lou, Y. & Ng-Kwai-Hang, K. F. (1992). Effects of protein and fat levels in milk on Cheddar cheese yield. Food Res. Intl., 25, 437-44.
Moxley, J. E. & Ng-Kwai-Hang, K. F. (1984). A study of milk composition-cheese yield relationships in the Canadian Cheddar cheese industry. Final report to Canadian dairy commission. Macdonald College of McGill University, Ste-Anne-de-Bellevue, Quebec, Canada. Ng-Kwai-Hang, K. F. (1990). Protein composition of milk and cheesemaking. Modern Dairy, Feb., pp. 1415. Ng-Kwai-Hang, K. F., Moxley, J. E. & Marziali, A. S. (1987). Gross composition of milk and Cheddar cheese yield in some Quebec cheese factories. Can. Inst. Food Sci. Technol. J., 20, 372-7.
Ng-Kwai-Hang, K. F., Moxley, J. E. & Marziali, A. S. (1988). Cheddar cheese composition in some Quebec cheese factories. Can. Inst. Food Sci. Technol. J., 21, 80-3. Pearce, K. N. (1978). The relationship between fat and moisture in cheese. N.Z. J. Dairy Sci. Technol., 13, 59-60. Phelan, J. A. (1981). Standardisation of milk for cheesemaking at factory level. J. Sot. Dairy Technol., 34, 152-6. SAS (Statistical Analysis System Institute) (1982). SAS User’s Guide: Statistics. SAS Institute, Cary, NC. Van Slyke, L. L. & Price, W. V. (1949). Cheese. Orange Judd Publishing Co., New York.
Effects of protein and fat levels in milk on cheese and whey compositions Y. Lou & K. F. Ng-Kwai-Hang* Department of Animal Science, McGill University, Macdonald Campus, 21,l I I Lakeshore Road, Ste Anne de Bellevue, Quebec, Canada H9X ICO
Bulk tank milk was standardised to six levels of fat (3.0, 3.2, 3.4, 3.6, 3.8, 4.0%) and similarly to six levels of protein, thus giving a total of 36 combinations in composition. Milk was analyzed for total solids, fat, protein, casein, lactose and somatic cell count and was used to make laboratory-scale cheese. Cheese samples from each batch were assayed for total solids, fat, protein and salt. Losses of milk components in the whey were also determined. Least squares analysis of data indicated that higher protein level in milk was associated with higher protein and lower fat contents in cheese. This was accompanied by lower total solids (higher moisture) in cheese. Inversely, higher fat level in milk gave higher fat and lower protein and moisture contents in cheese. Higher fat level in milk resulted in lower retention of fat in cheese and more fat losses in the whey. Higher protein level in milk gave higher fat retention in cheese and less fat losses in the whey. Regression analysis showed that cheese fat increased by 4.22%, while cheese protein decreased by 2.61% for every percentage increase in milk fat. Cheese protein increased by 2.35%, while cheese fat decreased by 6.14% per percentage increase in milk protein. Milk with protein to fat ratio close to 0.9 would produce a minimum of 50% fat in the dry matter of cheese. Keyw0rd.y: protein and fat in milk, cheese composition,
whey composition.
is 37% moisture (63% total solids) with a minimum of 50% fat in the dry matter. Cheese-making efficiencies are reflected by the extent of losses of milk components in the whey. Several workers (Barbano & Sherbon, 1984; Ng-Kwai-Hang et al., 1987) reported that lower than expected cheese-making efficiency found in some cheese factories was attributed to low milk casein in relation to fat and this resulted in excessive fat losses in the whey during cheese manufacturing. While the previous article (Lou and Ng-KwaiHang, 1992) reported on effects of altering milk fat and protein on cheese yield potential, the present study investigates, under laboratory conditions, the extent to which cheese composition and distribution of milk components in cheese and whey are altered by adjusting content of protein and fat in the milk used for cheese-making.
INTRODUCTION Efficient incorporation of milk components into cheese is of great interest to the cheese-maker because the quality of the resulting product will determine its commercial value. In the process of making Cheddar cheese, more than 90% of the fat and casein in milk contribute to the cheese solids. Amounts of minerals, whey protein, and lactose in milk which are retained in cheese during its manufacture depend on cheese moisture content (Emmons et al., 1990) as well as the manufacturing practices. The quality of a Cheddar cheese is based on its content of major components, including moisture, fat, protein and salt. To maintain uniformity in the product from one batch to another, and to conform to certain minimum legal limits, it is essential that cheese composition is carefully controlled. For example, the target value for Cheddar cheese
MATERIALS
*To whom all correspondence should be addressed.
Throughout
Food Research International 0963-9969/92/$05.00 0 1992 Canadian Institute of Food Science and Technology
and 445
AND METHODS the study, procedures for obtaining milk to six levels of fat (3.0-
standardising
446
Y. Lou, K. F. Ng-Kwai-Hang
4.0%) and six levels of protein (3.0-40%), cheesemaking under laboratory conditions, collection and weighing of cheese and whey samples, analysing components in milk, cheese and whey were the same as previously described (Lou & Ng-KwaiHang, 1992). Briefly, bulk tank milk from the college farm was nartiallv skimmed and then adiusted to contain &six dikerent levels of fat (3~@-4~0%) with cream-rich milk. Within each of the fat levels, the milk was also adjusted to contain six levels of protein (3.040%) with instant skim milk powder. The 36 possible combinations of adjusted milk samples in terms of fat and protein contents were used to make Cheddar-type cheese under standardised laboratory conditions (Lou & Ng-KwaiHang, 1992). After overnight pressing, cheese curds were weighed, grated, hermetically sealed in a plastic bag, and kept frozen at -10°C pending chemical analyses. Subsamples of initial milk used and of resulting whey from each batch of cheese were taken for chemical analyses. Milk, cheese, and whey samples were analysed in duplicate for total solids, fat, and protein as described previously (Lou & Ng-Kwai-Hang, 1992). Milk was also analysed for lactose, casein, non-casein protein (NCP) and somatic cell count (SCC) whereas cheese was also analysed for salt content. Statistical analysis The data were analysed by least squares methods in statistical models which included fat levels, protein levels, casein to fat ratio, and protein to fat ratio as fixed effects. Milk concentration in total solids, casein, NAP, lactose, XC, and initial pH of milk were included in the model as covariates to test the significance and obtain regression coefficients for these parameters. Six subclasses were used for levels of fat and also six subclasses for levels of milk protein. Twelve subclasses were used for casein to fat ratio and protein to fat ratio.
RESULTS AND DISCUSSION Cheese and whey composition The overall means and standard deviations for cheese and whey components for a total of 596 lots of cheese included in this study are presented in Table 1. Total solids in cheese varied from 55.87 to 60.61% (i.e. moisture of 39.394l.13%) in
Table 1. Overall means (x) and standard deviations (SD) for cheeseandwhey compositions for au samples included in this study
Product and component
8
SD
Cheese Total solids (%) Fat (%) Protein (%j Salt (%)’ ’ Fat in dry matter (%) Protein in dry matter (%) Moisture in non-fat substances
58.41 58.64 24.34 0.92 49.00 41.70 58.29
2.07 2.72 1.53 0.22 3.67 2.99 2.12
7.64 0.26 0.95
0.68 0.08 0.09
Whey Total solids (%) Fat (%) Protein (%)
the 36 combinations of milk fat and protein levels. If the values for total solids in cheese were compared within a given milk fat level, it was found that total solids in cheese decreased as protein content of milk increased, whereas within a milk protein level, cheese total solids increased proportionally with milk fat. It was also found that the highest protein content (4.0%) in milk resulted in low total solids in cheese while the lowest protein content in milk (3.0%) gave the highest cheese solids (58.89-60.61%). This situation reveals that higher milk protein, specifically casein, is associated with higher moisture content in cheese (Gilles & Lawrence, 1985). In cheese, casein is associated with 2.5 times its weight of water (Emmons et al., 1990). The ranges of fat and protein contents in cheese were 23.61-33.73% and 21.7627.12%, respectively. It was observed that within a given milk fat level, as protein concentration increased, fat in cheese decreased while protein in cheese increased. Fat content in cheese increased and protein content in cheese decreased with increasing fat concentration of milk for a given protein level. This is because casein and fat constitute more than 90% of the cheese total solids and they are negatively correlated (Ng-Kwai-Hang, 1990). Therefore, an increase of protein in cheese is accompanied by a decrease in fat content and vice versa. The salt contents of cheese in all levels of milk fat and protein ranged from 0.76 to 1.11% and were below the targeted value of 1.5%. Salt was added to give a final concentration of 1.5% in the cheese curd before pressing and losses in the liquid during the pressing process resulted in a cheese containing less than 1.5% salt. Variations in fat on a dry matter basis (FDM) and protein in cheese total solids (PDM) for the 36 combinations of milk and fat protein levels fol-
EfSects of protein and fat levels in milk on cheese and whey compositions
lowed similar trends as fat and protein contents in cheese. Milk with a protein to fat ratio of higher than 0.95 produced cheese containing less than 50% FDM. Although there is no legal limit for protein content of cheese, PDM is usually approximately 40% in cheese (Barbano & Sherbon, 1984; Ng-Kwai-Hang et al., 1988). A high PDM will result in a cheese that appears to be drier than what the moisture content indicates. Results in cheese composition for the 36 milk fat/protein combinations suggest that milk containing 3440% fat and 3.2-3.6% protein will produce cheese of a desirable composition. Values for moisture in nonfat substances (MNFS), with a range of 56.2360.53% for all combinations of fat and protein levels, were higher than some literature values (Barbano & Sherbon, 1984; Gilles & Lawrence, 1985). This was due to the higher moisture content of cheese (39.39-44.13%) attained in the present study, particularly for milk compositional combinations where protein levels were high in relation to fat. Overall means and standard deviations of whey composition are also presented in Table 1. Total solids in whey ranged from 6.57 to 8.76% in the 36 combinations of milk fat and protein levels. It was observed that total solids of whey increased as protein content of milk increased for a given fat level. This may be explained by the fact that the increase of protein content in milk was accompanied
447
by an increase of lactose content due to the addition of skim milk powder. For a given protein level, values for total solids in whey increased slightly with increased fat content in milk. Fat content in whey ranged from 0.18 to 0.37% in all combinations of milk fat and protein levels. Fat in whey slightly changed among six protein levels within each of fat levels. However, fat in whey increased as milk fat increased. This indicates that, for a given level, increasing milk fat will result in greater loss of fat in the whey during cheese-making because there is not enough casein to associate with fat. Protein content in whey varied from 0.83 to 1.04% for all milk fat and protein levels. It was found that protein in the whey increased with increasing milk protein for a given fat level, while it was changed slightly with an increase in milk fat within a protein level. This situation may be attributed to an increasing amount of NCP in the milk through the addition of SMP to increase milk protein. Recoveries of milk components in the cheese
Means and standard deviations for total solids, fat and casein of milk recovered in cheese in the 36 combinations of milk fat and protein levels were calculated and are shown in Table 2. Overall means were 49.83, 90.66 and 96.81%, for recoveries of total solids, fat and casein in cheese, respec-
Table 2. Recoveries of milk components in cheese for 36 combinations of milk fat and protein levels Milk fat level
Milk protein
Recovery m 2
z’?
level 4
3
5
6
SD
J?
SD
2
SD
2
SD
x
SD
J?
SD
1 Total solids Fat Casein
48.70 90.67 97.25
0.99 3.20 3.05
49.38 91.77 95.08
0.86 3.03 3.62
48.54 91.79 95.79
0.92 3.04 5.65
48.04 92.77 98.38
1.31 2.92 4.81
47.87 94.42 99.92
0.92 2.91 2.47
46.80 93.46 98.07
0.75 4.94 5.35
2 Total solids Fat Casein
51.01 92.17 94.17
1.57 2.72 5.27
50.14 91.80 96.50
1.46 2.04 4.82
50.18 91.80 96.45
1.72 2.04 3.94
49.33 91.42 97.00
2.11 2.87 2.76
49.66 93.47 95.73
1.35 2.03 2.15
48.97 92.40 97.50
2.10 2.59 2.07
3 Total solids Fat Casein
49.22 89.06 97.65
2.24 4.70 5.30
50.06 90.19 96.22
1.26 2.13 5.47
49.92 91.05 94.38
1.81 2.84 3.50
49.00 89.33 96.58
1.72 3.20 3.51
48.79 91.50 97.46
1.80 3.24 3.64
48.68 91.61 96.89
2.16 2.87 4.01
4 Total solids Fat Casein
50.93 90.06 97.06
1.59 3.08 4.62
50.65 90.48 94.90
1.73 3.78 3.58
50.46 90.79 96.64
1.13 344 4.30
50.00 90.50 97.17
1.05 2.87 4.36
49.77 91.47 96.84
0.99 3.73 3.1 1
48.99 90.90 96.90
1.34 2.73 3.52
5 Total solids Fat Casein
50.87 89.21 99.29
1.57 3.91 5.90
50.92 89.88 98.41
1.23 3.71 4.37
50.76 89.47 97.41
0.87 2.60 4.65
50.03 89.92 97.08
0.56 2.50 4.48
50.49 91.59 97.41
0.95 2.06 4.00
49.10 91.20 97.90
1.29 3.29 2.64
6 Total solids Fat Casein
5144 88.88 99.24
2.13 4.23 4.05
51.64 88.42 96.92
1.40 3.32 530
50.71 89.83 94.33
0.92 4.55 5.02
50.68 89.07 97.87
0.80 2.76 3.07
50.62 89.83 96.67
1.51 3.67 2.95
50.09 89.15 97.31
0.57 2.27 3.88
Y. Lou, K. F. Ng-Kwai-Hang
448
tively. Recovery of total solids in cheese varied from 4680 to 51.44% and decreased slightly as protein content in milk increased within a given fat level but increased with increasing fat content of milk for a given protein level. Although lactose accounted for a greater proportion of milk solids, it did not contribute significantly to the cheese mass. Therefore, milk with a higher protein level used to make cheese resulted in lower recovery of total solids in cheese. In contrast, a higher fat level gave higher recovery of total solids in cheese, since most of the fat in milk contributes to cheese solids. The recovery of milk fat in cheese was in a range of 8894% for the 36 combinations of six levels each of fat and protein. According to Van Slyke’s formula (Van Slyke & Price, 1949), an average of 93% fat recovery could be expected under normal conditions. Most of the values for fat recovery shown in Table 2 are lower than 93%. However, these results are similar to the findings by Lelievre (1983) and Gilles and Lawrence (1985). For a given milk fat content, the recovery of fat in cheese increased with increasing protei content in milk and for a given milk protein content, the fat recovery decreased with increasing fat content in milk. It is likely that the retention of fat in cheese is associated with the contents of protein and fat in milk. Such relationships were also found by Moxley and Ng-Kwai-Hang (1984), and Barbano and Sherbon (1984), who reported that low fat recoveries in cheese were due to a low casein to fat ratio in milk. The values for casein recovery in cheese are in a range of 94101% for all combinations of fat and protein levels. Most of
these values are close to or above 96% recovery predicted by Van Slyke’s formula. At least 4% casein is unavoidably lost in the whey as glycomacropeptide from K-casein (Phelan, 198 1) and proteose-peptone formed as a result of plasmin action on P-casein (Donnelly & Barry, 1983). Therefore a casein recovery of greater than 96% may be due to some of the NCP contributing to the cheese solids. An analysis of variance was carried out to study the influence of milk fat level, milk protein levels, ratios of casein to fat and protein to fat, and other milk components in cheese composition, and the results are summarised in Table 3. Sum of squares in the above table was computed using type III sum of the squares in SAS (1982). In this way, the effect of any factor on cheese composition could be calculated with adjustments being made for the effects of all the other factors included in the model. Milk fat level significantly affected protein 0, I 0.01) and salt (p 5 0.05) contents in cheese but did not have an effect on total solids and fat contents in cheese. Protein to fat ratio significantly influenced (p I 0.01) fat and protein content of cheese. Total solids in milk had significant effects on total solids (p 5 0.05), fat 0, I 0.01) and protein 0, I 0.05) in cheese while casein in milk only influenced (p I 0.05) fat content in cheese. Relationship between milk composition and cheese composition Regression of fat and protein percentages in cheese on milk fat and protein were significant and are
Table 3. Analysis of variance for cheese composition
Source
Sum of squares
df Total solids
Fixed effects Milk fat level Milk protein level Casein/fat Protein/fat Covariutes (milk component) Total solids (%) Casein (%) NAP (%) Lactose (%) Somatic cell count Initial milk pH Error up 2 0.05. bp I 0.01.
Fat
Protein
5 5 11 11
23.67 24.68 33.62 41.07
13.19 12.93 24.20 40.756
16.606 9.40 0.64 34.976
1 1 1 1 1 1
1444” 4.86 11.05 1.98 2.55 0.26
11.036 5.30” 4.34 0.02 0.70 0.13
3.79” 0.58 5.21 0.95 1.72 0
557
1731.20
801.39
547.43
Salt
0.56” 0.42 0.27 0.49 0.02 0 0.15 0 0.01 0.05 25.65
Efsects of protein and fat levels in milk on cheese and whey compositions 35 -
33 -
-be
31 -
T g
2Q-
37 -
5 5 % ha
27 -
25 -
27
b-2.40
b-2.29 b-2.21
b=2.01
b-2.24
i--_:
b-2.77
21 -I-
t 2.0
3.1
3.3
Protein
3.6
3.7
3.9
4.1
in milk(%)
2.9
3.1
3.3
3.5
3.7
3.9
4.1
Fat in Milk(%)
Fig. 1. Regression of fat and protein in cheese on protein
Fig. 2. Regression of fat and protein in cheese on fat content
content of milk for different fat levels. (14, Protein = 3.0%; x, protein = 3.2%; x, protein = 3.4%; -Ef, protein = 3.6%; *, protein = 3.8%; +, protein = 4.0%).
of milk for different rotein levels. (A, Protein = 3.0%; z, protein = 3.2%; G+T protein = 3.4%; B, protein = 3.6%; X, protein =‘3.8%; 0, protein = 4.0%).
presented in Figures 1 and 2. In Figure 1, the fat levels were fixed to test the effect of protein content of milk and protein percentages in cheese for each of fixed fat levels. The analyzed results in Figure 1 show that cheese fat and cheese protein change in opposite directions following an increase in milk protein for each of the fat levels. Cheese protein was positively correlated to milk protein, while cheese fat was negatively correlated. Protein content in cheese increased by 2.01-2.77%, whereas cheese fat decreased by 541-6.67% for every percentage increase in milk protein in different fat levels. In Figure 2, the protein levels were fixed to test the effect of fat content of milk on fat and protein percentages in cheese for each of the fixed protein levels. It was found that fat content in cheese was positively correlated to milk fat and
cheese protein was negatively correlated to milk fat for all protein levels. Fat content in cheese increased by 3.55461% and cheese protein decreased by 2.25-2.89% for an increase of 1% in milk fat in different protein levels. From the results presented in Figures 1 and 2, it was obvious that the change of cheese fat was greater than that of cheese protein following variations in milk fat and protein. This is explained by the fact that increasing the fat in cheese decreased the moisture content in cheese, resulting in higher total solids (Pearce, 1978). Thus, the percentage of fat in cheese increased to a great extent. As protein increased in milk, only casein (80%) of protein) contributed to the cheese, besides, cheese moisture increased with increasing milk protein, resulting in lower total solids.
Y. Lou, K. F. Ng-Kwai-Hang
450
Table 4. Percentage of fat in dry matter of cheese predicted from regression equation, FDM = 5398 + 6GF - 73OP Milk protein
(%)
Milk fat (%)
3.0
3.2
3.4
3.6
3.8
4.0
3.0 3.2 3.4 3.6 3.8 4.0
M 50.87 52.08 53.29 54.50 55.72
48.16 w 50.58 51.79 53.00 54.22
46.66 47.87 m 50.29 51.50 52.72
4516 46.37 47.58 4879 50.00 51.22
43.66 44.87 46.08 47.29 48.50 49.72
42.16 43.37 44.58 45.79 47.00 48.22
Values below the line represent legal limit of 50%.
those
meeting
the minimum
Table 4 shows the values for fat on dry matter in cheese predicted from the equation Y(FDM) = 53.98 + 6.06F - 7,5OP, obtained from regression analysis. From the results, it is obvious that milk with a given percentage of fat can produce different FDM in cheese by changing the percentage of milk protein. For example, milk with 3.6% fat (level 4) and 3.0% protein (level 1) will produce cheese containing 53.29% FDM, whereas milk at the same level of fat and 4.0% protein (level 6) will produce cheese containing only 4579% FDM. Cheese composition is a good indicator of cheese quality. For Cheddar-type cheese, the minimum legal limit is 50% for FDM. In Table 4 it was found that only the combinations of fat and protein below the underlined values gave the legal fat content of cheese. The predicted values in Table 4 were close to actual values as described previously. The combinations of fat and protein levels in milk which gave over 50% FDM in cheese, have a protein to fat ratio below 0.95. This is close to 0.90, indicated by Banks et al. (1984). As the results indicated, milk with a protein to fat ratio greater than 0.95 would produce cheese containing less than 50% FDM. Also, a higher ratio, which means high protein in relation to fat in milk, will produce cheese containing higher moisture because the protein in milk is positively correlated with cheese moisture. On the other hand, if milk with a protein to fat ratio much lower than 0.95, e.g. below 0.85, was used to make cheese, more fat would be lost in the whey since not enough protein was available to associate with fat during cheese curd formation. This would result in economic loss to cheese industries. With the present milk payment formula, prices for milk are paid according to the fat content of milk, but cheese-makers could not achieve maximum profits if no adjustments were made to optimise the protein to fat
ratio. Therefore, in order to obtain good quality cheese and maximum profits, it is suggested that the protein to fat ratio in milk should be 0.90 f 0.05. Losses of milk components in the whey The means and standard deviations for the losses of milk components in the whey for 36 combinations of fat and protein levels were calculated. Overall means were 52.04, 6.46, 24.25% for the losses of total solids, fat, and protein in the whey, respectively. Values for milk total solids lost in the whey during cheese-making varied from 49.40 to 53.95%. In other words, only about 50% of the milk solids, mainly fat, protein and some minerals, contributed to cheese solids. The remaining 50%, mainly lactose, NCP and half of the minerals, were lost in the whey. The means for the loss of fat in the whey were in a range of 5.10-8.06%. Van Slyke’s formula would predict that 7% fat is lost in the whey. In our study, the average value for fat loss (6.46%) was close to the predicted value (7%). However, the average fat loss in the whey should have been approximately 10% if compared with the overall mean of fat recovery in the cheese described above. Gilles and Lawrence (1985) also reported about 10% loss of milk fat in the whey in making Cheddar-type cheese. The low values for fat in whey obtained in our study may be attributed to the filtration used when taking the whey sample from the total volume of whey. Large fat globules were filtered out from the whey. Protein losses in the whey were within the range of 22.07-26.70% and were similar to those reported by Lelievre (1983). The loss of protein in whey can be calculated from NCP and casein in the milk. It is assumed that all of the NCP and 4% of the casein, which is predicted by Van Slyke’s formula, in milk is lost in the whey during cheese-making. The calculated values for the protein loss were in a range of 20.21-26.89% (average value 24.45%) which are within the actual range shown above. Table 5 summarises the analysis of variance performed to investigate the degree of variation in the losses of milk components in whey due to milk fat level, milk protein level, ratios of casein to fat and protein to fat and other milk components. Total solids loss in the whey were affected significantly (p 5 0.01) by milk fat level, milk protein and protein to fat ratio. Fat loss in the whey was influenced significantly (p I 0.01) by fat level, pro-
Efsects of protein
andfat
levels in milk on cheese and whey compositions
Table 5. Analysis of variance for milk component losses in the whey Source
df
Sum of squares Total solids
Fat
5 5 11 11
111.01* 68.33’ 23.54 66.65’
64.436 56.40’ 64-65’ 19.72
8.93 30.67” 19.60 20.36
1 1 1 1 1 1
4.32 3.14 1.08 1.94 0.02 0.04
0.09 0.13 0.69 0.13 3.48 3.38
9.07” 4.66 5.03 0.49 3.01 0.34
557
1450.03
1559.58
--
Protein
Fixed effects
Milk fat level Milk protein level Casein/fat Protein/fat Covariates
(milk component) Total solids (?/a) Casein ((s/o) NCP (%I) Lactose (“A) Somatic cell count Initial milk pH Error
1352.20
up I 0.05 *p IO.01
451
ACKNOWLEDGEMENTS The authors are grateful to the Agropur Cooperative Agro-Alimentaire, Granby, Quebec, for providing starter culture and calf rennet and for its technical assistance. The authors would also like to thank Mr Donald Galbraith and Mr George Destounis for this assistance in performing laboratory analyses. This project was financially supported by Conseil des Recherches en Peche et en Agroalimentaire du Quebec (Project No. 2588).
REFERENCES Banks, J. M., Muir, D. D. & Tamine, A. T. (1984). A comparison of the quality of Cheddar cheese produced from seasonal and standardized milk. J. Sot. Dairy Technol., 37, 88-92.
tein level and casein to fat ratio. The loss of protein in the whey was significantly (p I 0.05) affected by protein level and milk total solids.
CONCLUSIONS Results obtained from this study showed that cheese composition was significantly influenced by the levels of fat and protein in milk, since fat and protein are the two major solid components in the cheese. Higher protein level in milk was associated with higher protein content and lower fat content in cheese. Conversely, higher fat level in milk gave higher fat content and lower protein content in cheese. Casein has the ability to contribute absorbed water to the cheese in addition to its own weight. Therefore, higher protein content of milk resulted in lower total solids in cheese. The levels of fat and protein in milk also influenced the retention of fat in cheese. Higher fat level in milk resulted in lower retention of fat in cheese and more fat losses in the whey. Higher protein level in milk gave higher fat retention in cheese and less fat losses in the whey. From the results of cheese composition, we conclude that in order to obtain a minimum of 50% FDM in cheese, protein to fat ratio in milk should be around 0.9 (or casein to fat ratio around 0.7).
Barbano, D. M. & Sherbon, J. W. (1984). Cheddar cheese yield in New York. J. Dairy Sci., 67, 1873-83. Donnelly, W. J. & Barry, J. G. (1983). Casein compositional studies III. Changes in Irish milk for manufacturing and role of milk proteinase. J. Dairy Res., 50, 433-4 1. Emmons, D. B., Ernstrom, C. A., Lacroix, C. & Verret, P. (1990). Predictive formulas for yield of cheese from composition of milk: A review. J. Dairy Sci., 73, 1365-94. Gilles, J. & Lawrence, R. C. (1985). The yield of cheese. N.Z. J. Dairy Sci. Technol., 20, 205-14.
Lelievre, J. (1983). The influence of the casein to fat ratio in milk on the moisture in the non-fat substance in Cheddar cheese. J. Sot. Dairy Technol., 36, 119-20. Lou, Y. & Ng-Kwai-Hang, K. F. (1992). Effects of protein and fat levels in milk on Cheddar cheese yield. Food Res. Intl., 25, 437-44.
Moxley, J. E. & Ng-Kwai-Hang, K. F. (1984). A study of milk composition-cheese yield relationships in the Canadian Cheddar cheese industry. Final report to Canadian dairy commission. Macdonald College of McGill University, Ste-Anne-de-Bellevue, Quebec, Canada. Ng-Kwai-Hang, K. F. (1990). Protein composition of milk and cheesemaking. Modern Dairy, Feb., pp. 1415. Ng-Kwai-Hang, K. F., Moxley, J. E. & Marziali, A. S. (1987). Gross composition of milk and Cheddar cheese yield in some Quebec cheese factories. Can. Inst. Food Sci. Technol. J., 20, 372-7.
Ng-Kwai-Hang, K. F., Moxley, J. E. & Marziali, A. S. (1988). Cheddar cheese composition in some Quebec cheese factories. Can. Inst. Food Sci. Technol. J., 21, 80-3. Pearce, K. N. (1978). The relationship between fat and moisture in cheese. N.Z. J. Dairy Sci. Technol., 13, 59-60. Phelan, J. A. (1981). Standardisation of milk for cheesemaking at factory level. J. Sot. Dairy Technol., 34, 152-6. SAS (Statistical Analysis System Institute) (1982). SAS User’s Guide: Statistics. SAS Institute, Cary, NC. Van Slyke, L. L. & Price, W. V. (1949). Cheese. Orange Judd Publishing Co., New York.