Influence of temperature, time and pretreatment media on protein content of milk collected on filter paper disks

Filter paper disks or strips are an economic and convenient medium to collect liquid biological samples. It is widely used to collect clinical samples for diagnosis of a few diseases. The present study focused on determining the suitability of this method to monitor protein levels of milk samples. Bradford protein assay was employed to evaluate the accuracy, suitability, and coefficient of variation of protein in milk collected on filter paper disks. The coefficient of variation (CV) was 4.41% within a sample and 7.27% between the samples. The protein level was significantly lower than that in samples of fresh milk, and only 83.6% protein could be recovered. The results showed that protein level was significantly affected by the length of time over which the samples had been preserved and the media used for pre-treating the disks. Protein levels gradually fell as the time over which the samples had been preserved increased. The results indicate that disks pre-treated with Tris-HCl buffer without EDTA and stored under 37 degrees C were the most effective in preserving milk proteins in the samples.