Determination of lactose in milk

Lactose, the major carbohydrate of milk, forms over 50% of the solids in skimmed milk, and an even greater proportion of the whey solids (4). There are numerous methods for determining the lactose content of milk products and an excelente review of those appearing in the literature between 1964 and 1974 was recently made (1). Although enzymatic procedures are particulary useful for the determination of small quantities of sugars, e.g. in cheese (6), and for the estimation of lactose, glucose, galactose, fructose, and fruit yoghurt (3), new colorimetric procedures are constantly being developed.

Recently, a new colorimetric method involving the use of phenol, sodium hydroxide, picric acid and sodium bisulfite was developed for the estimation of lactose in fluid milk and whey (7); the method is applicable for lactose determination in presence of lactate and its sodium salt (8), as well as for total nonstructural carbohydrate determination of plant issues (5).

We have tested the above method and this paper reports the results obtained in the analysis of fresh and refrigerated raw milk, buttermilk and whey samples, including one mastitic milk sample, using Teles’ technique and an international standard for the lactose determination in milk.

References

(1) BOSSET, J. D.; BLANC, B.; PLATTNER, E. Le dosage du lactose et de ses produits d’hydrolyse dans le lei et dans quelques produits laitiers: méthodes et appareillages tirés de la litterature purus entre 1964 at 1974. Trav. Chim. Aliment. Hyg., v. 67, p. 488-514, 1976.

(3) LECHNER, E. Determinação de lactose no leite e produtos lácteos. Revista do ILCT, v. 36, n. 214, p. 3-6, 1981.

(4) NICKERSON, T. A. Lactose chemistry. J. Agric. Food Chem., v. 27, n. 4, p. 672-677, 1979.

(5) SILVEIRA, A. J. da; TELES, F. F. F.; STULL, J. W. A rapid technique for total nonstructural carbohydrate determinations os plant tissue. J. Agric. Food Chem., v. 26, n. 3, p. 770-677, 772.

(6) STEFFEN, Chr.; NICK, B.; BLANC, B. Methodik zur enzymatischen Bestimmung von Lactose, Glucose, Galactose und Lactat im Käse. Schweitz. Milchw. Forsch., v. 4, p.13-15, 1975.

(7) TELES, F. F. F.; YOUNG, C. K.; STULL, W. J. A method for rapid determination of lactose. J. Dairy Sci., v. 61, n. 4, p. 506-506, 1978.

(8) TELES, F. F. F.; BATISTA, C. M.; REZENDE, J. L. M. Nova técnica para análise de lactose na presença de lactato. Revista do ILCT, v. 37, n. 200, p. 27-30, 1982.

[63] WOLFSCHOON-POMBO, A. F.; LIMA, A. de; CASAGRANDE, H. de R. Determination of lactose in milk. Dairy Industries International, v. 48, n. 3, p. 35-37, 1983.

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