March, 19501 EL-SOKKARY AND HASSAN : EGYPTIAN MILK 143 Lactose and Chloride Contents of Egyptian Cows’ and Buff aloes’ Milks BY A. M. EL-SOKKARY AND H. A. HASSAN SyNoPsIs-Previous studies of Egyptian milks have not included the direct chemical estimation of lactose and chloride contents. An investigation has therefore been carried out, as an extension of previous work, into the lactose and chloride contents of the milks of Egyptian cows and buffaloes, 100 of each animal being taken at random. Buffaloes’ milk was found to have a significantly higher lactose c6ntent and lower chloride content than cows’ milk. Mean values, ranges of variation and frequency distributions of values have been calculated for both milks. The chloride - lactose relation, calculated by the Mathieu and Fen6 formula, was found to be approximately the same for both milks, although the value was lower than had originally been supposed.OWING to the lack of adequate data on the subject, there is still considerable scope for an investigation of the milks of Egyptian cows and buffaloes. In a previous paper,l the authors have given some results for both milks, but lactose and chloride contents were not given, since they were not determined. Lactose is generally obtained by difference methods in routine milk analysis, and thus there are very few available data based on its actual chemical determination, as compared with the data concerning the other constituents of cows’ milk. This inadequacy is even more noticeable in the case of buffaloes’ milk, owing to the small amount of work that has been carried out on it.It was decided, therefore, to carry out an investigation on both milks to complete the previous study. The complementary relationship between lactose and chloride in milk has been recognised for over 50 years, and Mathieu and Ferrk’s formula2 is still looked upon as a valuable means of assessing the part played by lactose in the variation of non-fatty solids in milk. The chloride content of milk is taken as a criterion of the performance of the animals’ glands in milk secretion, since a low chloride content denotes a high level of lactose secretion, and thus indicates a good condition of the secreting tissue. Recent investigation^,^^^ however, although still indicating a close negative correlation between the lactose and chloride contents of milk, show wide variation in Mathieu and Ferrk’s value or the “simplified molecular constant.” The problem, therefore, needed further investigation, particularly with respect to the Egyptian milk animals, in which field this paper is the first to deal with the subject.EXPERIMENTAL This study was carried out on individual samples taken from the well-mixed milk from the morning milking of 100 cows and the same number of buffaloes kept in Cairo and on neighbouring farms. Samples were taken at random, but animals with clinical cases of disease were avoided. Lactose and chloride contents were determined, and their relationship calculated according to the Mathieu and Ferrk formula2: Lactose, per cent. + 19.6 x chloride, per cent. = constant (7).METHODS OF ANALYSIS-Lactose was determined by the gravimetrk method of A.O.A.C. for milk: and chloride by the wet digestion method developed by Davies.9144 EL-SOKKARY AND HASSAN: LACTOSE AND CHLORIDE CONTENTS [Vol. 75 RESULTS Table I shows the means, S.D., S.E.M. and significance of differences in lactose content, The significance of differences chloride content and chloride - lactose number, for both milks. is calculated by the t-test.’ TABLE I: THE SIGNIFICANCE OF DIFFERENCES BETWEEN cows’ AND BUFFALOES’ MILKS Lactose, % Chloride, yo Chloride - lactose number 7- 7- EzZ-za Cows’ Buff aloes’ Cows’ Buff aloes’ Mean .. . . 4-71 4-87 0.0765 0.0649 6.20 6.15 Range of variation 3-75-5-39 3.91-5.46 0.0403-0-1492 0-0338-0.1 190 5.73-6-89 6.83-6-58 S.D. ... . 0.33 0.27 0.0209 0.0149 0.20 0.18 S.E.M. . . . . 0.03 0.03 0.002 1 0.0015 0.02 0.02 Difference between means, C-B . . - 0.16 + 0.0116 + 0.05 t .. .. .. 3.7324 4.5366 1.8746 Probability, P . . < 0.01 < 0.01 0.1-0*05 - Significance* .. + + The frequencies with which the threevalues occur were calculated, and are given in * Plus sign (+) = significant; minus sign (-) = insignificant. Tables 11. I11 and IV. TABLE I1 FREQUENCY DISTRIBUTION OF PERCENTAGE OF LACTOSE 3-40 3.80 4.20 4.60 5.00 5-40 Intervals . . to to to to to to 3-80 4.20 4.60 5.00 5.40 5.80 Cows’milk .. .. 2 5 32 39 22 - Buffaloes’ milk . . - 1 13 52 33 1 TABLE I11 FREQUENCY DISTRIBUTION OF PERCENTAGE OF CHLORIDE 0.0300 0.0500 0.0700 0.0900 0.1100 0.1300 0.0500 0.0700 0.0900 0.1100 0.1300 0.1500 Intervals .. to to to to to to Cows’ milk . . .. 7 35 38 14 3 3 Buffaloes’ milk . . 12 51 33 3 * 1 - TABLE IV FREQUENCY DISTRIBUTION OF CHLORIDE - LACTOSE NUMBER 5.6 5.8 6.0 6.2 6.4 6.6 6.8 Intervals . . to to to to to to to 5.8 6.0 6.2 6.4 6-6 6.8 7.0 Cows’ milk .. 2 8 41 36 9 1 3 Buffaloes’ milk . . - 16 54 20 8 2 - DISCUSSION OF RESULTS LACTOSE CONTENT- Total 100 100 Total 100 100 Total 100 100 It can be seen from Table I that the lactose content of cows’ and buffaloes’ milks ranged from 3-75 to 6.39 per cent. and 3.91 to 5-46 per cent. respectively; the mean values being 4.71 per cent., S.E.M. 0.03, and 4.87 per cent., S.E.M. 0-03. It is thus observed that buffaloes’ milk has a higher lactose content than that of cows; the difference averaging 0.16 per cent.This difference, though little, is consistent, and, as calculated by the t-test, has a P of less than 0.01, which indicates its high significance. This was also proved by Anantakrishnan ei! al.? who found that Indian buffaloes’ milk contained more lactose than did cows’ milk. Table I1 shows that the highest frequency distribution of lactose lies in the class 4-60 to 5.00 per cent. in both milks, but for that of cows this highest frequency represents 39 per cent. of the samples, while it represents 52 per cent. of the samples of buffaloes’ milk. It is also noticeable that for cows’ milk, 39 per cent. of the samples are below this class, whileMarch, 19501 OF EGYPTIAN cows’ AND BUFFALOES’ MILKS 145 for buffaloes’ milk, the corresponding percentage is only 14, and 34 per cent.of the samples are above the 4.60 to 5.00 per cent. class. This distribution clearly shows that the value tends to be higher for buffaloes’ than for cows’ milk. Results given by Ghosb and Datta-Roy8 show that lactose in buffaloes’ milk ranged from 4.0 to 5.3 per cent., and that of cows’ milk ranged from 3.8 to 5.3 per cent. These results are in close agreement with those of the present investigation, and with most of the available data for European and other breeds of cows. CHLORIDE CONTENT- I t is well known that the chloride contents of individual samples of cows’ milk show wide variation. The mean values are 0.0765 per cent., S.E.M. 0.0021, and 0.0649 per cent., S.E.M. 0.0015, for cows’ and buffaloes’ milks respectively. In the former, the value varied from 0.0403 to 0.1492 per cent., while in the latter it varied from 0.0338 to 0.1190 per cent., thus indicating that, on the average, cows’ milk is 0.0116 per cent.higher in its chloride content than that of buffaloes. The difference is statistically significant, as shown in Table I. This observation, together with the higher content of lactose in buffaloes’ milk and its higher value of casein nitrogen as a percentage of the total nitrogen - casein number (El- Sokkary and Hassanl), indicates that buffaloes have a more efficient secreting tissue than cows have. It can also be seen, by comparing the present results with those given by D a ~ i e s , ~ that Egyptian cows’ milk tends to contain less chloride than does the milk of other breeds of Table I11 shows that the highest percentage distributions of the chloride value for both cows’ and buffaloes’ milks lie in the classes 0.07 to 0.09 per cent.and 0.05 to 0-07 per cent. respectively, representing 35 and 51 per cent. of the samples. For cows’ milk, 58 per cent. of the samples had chloride values above the highest frequency distribution, while for buffaloes’ milk, only 37 per cent. were above i t ; hence the significance of the difference between the two milks is explained. This is demonstrated by the magnitude of the variations in Table I. cows. CHLORIDE AND LACTOSE RELATIONSHIP- Owing to the fact that chloride and lactose concentrations in milk account for approxi- mately 75 per cent. of its osmotic pressure, many attempts have been made to establish the correlation between them on a complementary basis.Among these attempts are those of Kopatschekl* and Koestler,ll but their ratios, however, are not so commonly used as that given by the formula suggested by Mathieu and known as the “simplified molecular constant.” It is stated that if the value is below 7, the milk sample may be suspected of containing added water. Since these workers published their results many investigations have been carried out on the subject, and these showed the value to vary over a remarkably wide range. Richmond et aLl2 state that the value is said to lie, for most milks, between 7.4 and 7.9, but they quoted a report of a range of 6.92 to 8.28. Recently, some investigators have given results which show wider variations. Mathieu,13 working on the milk of cows in Alpine regions, found that the ratio, in most samples, was higher than 8.0.Anantakrishnan et aL3 found that, with Indian cows’ and buffaloes’ milks, the lactose - chloride relationship did not hold. Moreover, working out the ratio from results given by Roadhouse and Henderson* on milk from American breeds of cows, the authors found that, for one set of results, the ratio varied from 6.19 to 7.34, corresponding to lactose and chloride contents of 4.74 and 0.074 per cent. respectively for the lower ratio, and 4.16 and 0.162 per cent. respectively for the higher ratio. In another set, a ratio as low as 5.99 is given, corresponding to 5.05 per cent. lactose and 0.048 per cent. chloride. These latter results agree to a large extent with those of the present study, where the mean value for the ratio in cows’ milk is 6.20, S.E.M.0-02, ranging from 5.73 to 6-89, and that of buffaloes’ milk is 6.15, S.E.M. 0.02, ranging from 5.83 to 6.58. Difference between both means is shown to be insignificant (see Table I). Table IV gives the frequencies with which values are distributed among the various classes. The highest percentage distributions for both milks lie in the same class, namely 6.0 to 6.2, and represent 41 per cent. of the cows’ milk samples and 54 per cent. of those of buff aloes’ milk.146 HALES THE INFRA-RED SPECTROSCOPIC ESTIMATION OF [Vol. 75 SUMMARY- Buffaloes’ milk was found to have significantly higher lactose and lower chloride contents than cows’ milk. The following are the respective means for cows’ and buffaloes’ milks: Lactose: 4-71 per cent., S.E.M.0.03, and 4.87 per cent., S.E.M. 0.03. Chloride: 0-0765 per cent., S.E.M. 0.0021, and 0.0649 per cent., S.E.M. 0.0015. Using the formula suggested by Mathieu and Ferr6 the lactose - chloride relation was calculated, and was found to be approximately the same for both milks, although the value was lower than had originally been supposed. REFERENCES 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. El-Sokkary, A. M., and Hassan, H. A., J . Dairy Res., 1949, 16, 217. Mathieu, L., and F e d , L., J . SOC. Chem. Ind., 1914, 33, 214. Anantakrishnan, C. P., Dastur, N. N., and Kothavala, 2. R., Indian J . Vet. Sci., 1944, 13, 297. Roadhouse, C. L., and Henderson, J. L., Calif. Agric. Expt. Sta. Bull., 1935, 395. Oficial and Tentative Methods of Analysis of the A.O.A.C., 6th Edition, 1945. Davies, W. L., Analyst, 1932, 57, 99. Fisher, R. A., Statistical Methods for Research Workers, Oliver & Boyd, Edinburgh, 1936. Ghosb, N. K., and Datta-Roy, B. K., Indian Med. Gazette, 1941, 76, 279. Davies, W. L., J . Dairy Res., 1938, 9, 327. Kopatschek, F., quoted by Davies, W. L., Chemistry of MiEk, Chapman & Hall, 1936, p. 49. Koestler, G. A,, Mitt. A u s dem Geb. Lebensmie. Untersuch. u. Hyg., 1920, 11, 154. Richmond, H. D. et al., Dairy Chemistry, Chaxles Griffin & Co., Ltd., London, 1942, p. 130. Mathieu, M. G., Lait, 1942, 22, 219-220, 317-323. DAIRY DEPARTMENT, FACULTY OF AGRICULTURE FOUAD I UNIVERSITY, CAIRO July, 1949