Low titratable acidity in individual milk samples of cows

LUIS C. ARRUDA JUNIOR*1, DILETA R. M. ALESSIO1, FERNANDO A. SCHMIDT1,

ANGELA PELIZZA1, ADRIANA HAUSER1, MARCIEL FRANÇA1, DAÍSE WERNCKE2,

ALEXANDRE S. ABREU2, VIVIAN FISCHER2, ANDRÉ THALER NETO1 1Post Graduate Program Animal Science, University the State of Santa Catarina,

Agroveterinárias Science Center, Lages, SC, Brazil 2Post Graduate Program Zootechnics, Federal University of Rio Grande do Sul, Porto Alegre,

RS, Brazil

*luis.arruda@ifc-concordia.edu.br

The milk composition is a factor that determines its nutritional quality and suitability for

processing and human consumption. According to the Instruction Nº62/2011 of the Ministry of

Agriculture, Livestock and Supply it is necessary to meet compositional standards of quality and

physical properties of raw milk. Physical characteristics such as titratable acidity (TA) are highly

important for processing dairy products, being established legal limits between 14 to 18º Dornic

(ºD). However, there is lack of research of the conditions that milk with low TA occurs, the

conditioning factors and their relation with the milk. Based on this, the aim was to characterize

low TA on individual fresh cow milk samples and its relation to milk composition. The study was

conducted using data from six independent experiments carried out from 2007 to 2015, in the

South and Highland of Santa Catarina, totaling 1.717 milk samples of Holstein, Jersey and

crossbred ½ Jersey x Holstein cows. Was considered milk with low TA samples with 14ºD or less.

For statistical analysis, somatic cell count (SCC) was transformed into logarithm to base two

(somatic cell score). Multivariate analysis methodology was used, (factor analysis) by FACTOR

procedure, of SAS® statistical package, and metric variables standardized by STANDARD

procedure selected by commonalities and analyzed the relationship between the factors presented

with Promax rotation. Of the total samples, 28.64% had low TA. Factor analysis explained 59.6%

of the total variance of three factors. The first factor show the positive relationship between lactose

content, TA and milk production (0.7521; 0.6833; 0.5609), with negative relation to SCC (-

0.6457). The second factor make up the positive relationship of fat and milk protein (0.8110;

0.8453). The third factor shows that the increase of urea nitrogen percentage in milk (MUN)

(0.8070), increases milk stability to the alcohol test (0.6321). The relationship between SCC and

low TA can be explained by the higher pH in milk with high SCC. The infected mammary gland

show altered milk composition, with higher content of sodium and lower potassium content; the

pH tends to be higher and, therefore less TA. The reduction on lactose concentration in the mastitic

milk can happen due to damage of the epithelial cells of the mammary gland, with milk lactose

extravasation into the bloodstream and, also due to the maintenance of osmotic equilibrium. It

follows that low TA on milk is related to high SCC and low lactose content, and unrelated to fat,

and protein content, MUN and instability of milk to the alcohol test.

Keywords: individual milk samples, legislation, milk processing, physical properties of milk,

titration Dornic