Evaluation and classification of quality of commercial milk consumed in Tuxtepec, Oaxaca, Mexico.

The physicochemical and color characteristics of eight milk brands consumed in the municipality of Tuxtepec and a classification was proposed based on fat and non-fatty solids content and added water. The different milk brands showed significant differences (p < 0.05) in all the parameters. Brand H displayed the lowest values for all parameters, except for fat and added water. None of the milk brands complies with the specifications set by the Mexican Official Standard (NOM, for its acronym in Spanish) in terms of protein, lactose, non-fatty acids content and density. The cryoscopy values for all the brands were greater that the established by NOM, with high values of added water. All the brands comply with the minimum standards for titratable fat and acidity. In regards to color, there were differences (p < 0.05) among brands, with brand H as the furthest from the standard blank. Using a Cluster analysis, and on the basis of the parameters proponed, four groups of milk were identified: acceptable quality (brands F, G), fair quality (brands B, C, E), poor quality (brands A, D), and inacceptable quality (brand H).