Conservação de amostras de leite cru utilizando diferentes concentrações de azida sódica e cloranfenicol

Abstract

This study aims to evaluate a more intense method for the preservation of raw milk samples, seeking to maintain their integrity and reliability in the evaluation of microbiological quality, providing a safe and reliable result to portray the real conditions of milk production. In order to do this, milk from cooling tanks of two rural properties with bacterial counts previously known has been collected, including two groups of in naturamilk: G-1 being in accordance, and G-2 in disaccordance with the parameters of the current regulations for standard plate count (SPC) obtained electronically. The milk of both groups was split in 720 bottles, comprising the following treatments: usual concentration of sodium azide and chloramphenicol of the azidiol tablet (T-1), double sodium azide concentration and chloramphenicol (T-2) and triple sodium azide concentration and chloramphenicol (T-3). The samples were stored for 14 days in incubation temperature of 3°C ± 1°C, 6°C ± 1°C and 9°C ± 1°C. Samples without the addition of preservative exposed to the same variables have been used as control (T-4). The samples were analyzed on a daily basis over the period of incubation, using for the carrying out of the trials the equipment Bactocount Bentley IBC ®, Bentley Instruments Incorporated, Chaska, United States of America, and the results expressed in individual bacterial count (IBC) and later transformed into base 10 logarithm (Log 10) for the statistical treatment. It's a relevant discovery that the use of preservatives is indispensable for the conservation of the samples, since even under low temperatures, the conditioning is not enough to prevent the increasing of the bacterial count throughout the incubation period, and consequently the deterioration of the samples. The T-3 has shown the best conservation condition, enabling the analysis of bacterial count until the 12th day in incubation temperature of 3°C, and up to the 8th day in incubation temperature of 6° C, without significant change in the results by Tukey test (p > 0,05). In such a way, increasing the concentration of sodium azide and chloramphenicol of the conservative tablet, made possible to extend the analytical viability of the samples. According to the evaluation of linear correlation, for G-1 in the treatments utilizing preservatives, there is no association for the variables; on the other hand, the evaluated in G-2 for these treatments shows an association, since with the increasing of incubation time, the result of bacterial count decreases. For G-1, as for G-2, association between variables of T-4 regardless of the temperature was found, that is; increasing the incubation time also increases the results of the bacterial counting.