Determination of Lactose Concentration in Milk Serum by Refractometry and Polarimetry

Rodica Căpriță


The research had in view to evaluate and compare two instrumental techniques used for the determination of milk lactose. Refractometric and polarimetric measurements were carried out on milk serum obtained after precipitation of casein by two different methods: by acidification of milk to its isoelectric point (E1), and by using copper sulphate and potassium ferrocyanide (E2). The average lactose content measured by refractometry was 5.469±0.256g% for method E1 and 5.852±0.218g% for method E2. The obtained average lactose values measured by polarimetry were higher both for E1 (5.613±0.253g%) and E2 (5.910±0.224g%) methods, due to the interference with other optically active components. The experimental data revealed a high correlation between the results obtained by refractometry and polarimetry (r = 0.8712) when casein precipitation was performed by potentiometric titration until pH = 4.6, at 25°C with 2N acetic acid (method E1).


lactose, milk, refractometry, polarimetry

Full Text:



Messer, M., Fitzgerald, P.A., Merchant, J.C., and Green, B., Changes in carbohydrates during lactation in the eastern quoll Daysurus viverrinus (Marsupialia), Comp. Biochem. Physiol., 1987, 88B, 1083–1086.

Miller, G.D., Jarvis, J.K., and McBean, L.D., Handbook of Dairy Foods and Nutrition, Second Edition, CRC Press Inc., Boca Raton, FL, 2000.

Wong, N.P., Lactose, in: Fundamentals of Dairy Chemistry, Marth E.H., Steele J.L. (eds.), Gaithersburg, MD., Aspen Pub., 1999, p. 361

Jensen, R.G. (Ed). Handbook of Milk Composition. New York, Academic Press, 1995.

Corso, N., Olano, A., and Castro, I.M., Carbohydrates, in : Handbook of Dairy Foods Analysis, Nollet, L.M.L, Fidel Toldra F. (eds.), RC Press, 2009 - Technology & Engineering, p.139.

Bleck, G.T., Wheeler, M.B., Hansen, L.B., Chester-Jones, H., and Miller, D.J., Lactose synthase components in milk: concentrations of alpha-lactalbumin and beta 1,4-galactosyltransferase in milk of cows from several breeds at various stages of lactation, Reprod. Domest. Anim., 2009, 44(2), 241-247.

Vilotte, J-L., Lowering the milk lactose content in vivo: potential interests, strategies and physiological consequences, Reprod. Nutr. Dev., 2002, 42, 127–132.

Clark, S., and Costello, M., Genetics and Milk Production, in: Handbook of Food Products Manufacturing: Health, Meat, Milk, Poultry, Seafood, and Vegetables, vol. 2, Hui Y.J. (ed.), John Wiley & Sons, 2007.

Newburg, D.S., and Neubauer, S.H., Carbohydrates in milk: Analysis, quantities, and significance, in: Handbook of milk composition, Jensen R.G. (ed.), San Diego, Academic Press, 1995, pp. 273–349.

Tunick, M.H., Selection of Techniques Used in Food Analysis, in: Methods of Analysis of Food Components and Additives, edited by Semih Otles, Taylor & Francis (CRC Press), 2005.

Kleyn, D.H., Determination of lactose by an enzymatic method, J. Dairy Sci., 1985, 68(10), 2791-8.

Pritchard, S., and Kailasapathy, K., Chemical, Physical and Functional Characteristics of Dairy Ingredients, in: Dairy Ingredients for Food Processing, Chandan R.C., Kilara, AF. (eds.), John Wiley & Sons, 2010, pp. 35-57.

Hueso, P., Martín-Sosa, S., and Martín, M-J., Role of Milk Carbohydrates in Preventing Bacterial Adhesion, in: Handbook of Carbohydrate Engineering, Yarema K.J. (ed.), Taylor & Francis (CRC Press), 2005, pp. 141-175.

Căpriţă, R., Principii şi tehnici biochimice, Ed. Gutenberg, Arad, 2001, pp. 147-149.

Fox P.F., and McSweeney P.L.H., Dairy Chemistry and Biochemistry, Kluwer Academic, New York, 1998, pp. 21-38


  • There are currently no refbacks.

Copyright (c)

Scientific Papers Animal Science and Biotechnologies publish open access articles under the terms of the Creative Commons Attribution 4.0 Licence (read full legal code).


ISSN print 1841 - 9364
ISSN online 2344 - 4576
ISSN-L  1841 - 9364
(former ISSN 1221-5287, E-ISSN 1841-9364)

PAPER ACCESS: Full text articles available for free
FREQUENCY: Semiannual

Banat´s University of Agricultural Sciences and Veterinary Medicine "King Michael I of Romania" from Timisoara
Bioengineering Faculty of Animal Resources
300645, Timişoara, Calea Aradului 119, Romania

E-mail: spasb [at]
Phone: +40-256-277160, Fax.: +40-256-277110