Influência de diferentes tipos de micro-organismos na contagem bacteriana total e de células somáticas por citometria de fluxo e na composição centesimal do leite cru

Abstract

Bacterial count was made of 179 raw milk samples from different dairy farms of Minas Gerais, Brazil, through the methods of flow cytometry and standard plate count, the reference method. The results obtained by different methods were analyzed by Pearson correlation. There wassignificant correlation between the values of psychrotrophic and mesophilic counts determined by the reference method with the values of bacterial count determined by flow cytometry (r = 0.6695 and 0.7008, respectively), being possible to establish linear regression equations forbacterial count obtained by flow cytometry according to the count of mesophilic (log CBI by flow cytometry = 0.701 log mesophilic + 1.9091) and psychrotrophic (log CBI by flow cytometry = 0.4703 log psychrotrophic + 3.2784). It was not possible to establish calibration curves for thermophiles and thermodurics because the correlation coefficients obtained among the count of these organisms and total bacterial count determined by flow cytometry were low (r = 0.2996 and 0.2746, respectively). Additionally, the correlation coefficients among thepsychrotrophic count and the percentage of fat, protein, lactose and total solids of milk were determined, through the Spearman correlation. There was weak negative correlation (p < 0.01) for fat and total solids (r = -0.2198 and -0.1635, respectively). There was also weak negativecorrelation (p <0.01) between somatic cell count (analysis performed on the Bentley Somacount® equipment) and milk total solids content (r = -0.1346) and strong negative correlation between somatic cell count and lactose content (r = -0.7180) using the Spearman correlation. There was weak negative correlation between total bacterial count and somatic cellcount in milk. The fat, protein, lactose and total solids of milk showed a negative correlation (p <0,05) with the total bacterial count (r = -0.2130; -0.1772; -0.1912 and -0.2335; respectively).