Milk is a highly nutritious food, and it is a source of macro and micronutrients which necessary for growth, development and maintenance of human health. On the other hand, it also considered to be a good environment for a lot of food contaminants that may cause many diseases. In this study, random samples from milk powder were collected from 5 hyper markets in Alexandria governorates, Egypt (15 samples from closed containers and 15 samples from opened containers). All samples were examined for the incidence and enumeration of both aerobic bacteria and mould to judge the microbiological condition. Also, aflatoxin M1 determination. The result revealed that the clearance of all samples which collected from closed containers examined for aerobic bacteria, mould and aflatoxin M1. Results of samples which collected from opened containers revealed that 60% of samples were positive for aerobic bacteria with mean ± SEM (8.1x10³ ± 1.7x10⁴), 33.3% were positive for mould with mean ± SEM (6 x10² ± 1x10³ ) and 13.3 % were positive for aflatoxin M1 with mean ± SEM (1.53 ± 0.28). Results of aerobic bacteria enumeration in all contaminated samples from opened containers were within the accepted limits according to Egyptian standard no.8073\2017. On the other hand, results of aflatoxin M1 exceeded the limits based by Egyptian, European and U.S standards. Two contaminated samples with aflatoxin M1 were subjected to gamma irradiation and ultraviolet treatment, the results showed that the bacterial growth was eliminated in the first sample after 45 minutes UV treatment while reduced by 99.8% in the second sample. Fungal growth was eliminated in the first sample and reduced by 98.75 % in the second sample after 60 minutes of UV radiation treatment. Moreover, aflatoxin M1 reduced by 67.2 % and 72.9 % for the first and second samples respectively after 60 minutes of UV radiation treatment. By using gamma irradiation, bacterial and fungal growth in the two treated samples were significantly reduced by the 1^st treatment dose (5 kGy), while aflatoxin M1 were gradually reduced in both samples by increasing treatment dose without reaching to regulations acceptable limits. It was noticed that some changes on treated samples colour after 60 minutes of UV treatment and 40 kGy gamma irradiation as a side effect from irradiation treatment. Treatment with elevated doses of gamma irradiation had more effect on reduction of aflatoxin M1 than UV irradiation in spite of the both treatment failed to reduce aflatoxin M1 of contaminated samples to the regulations acceptable limit. In addition, irradiation treatment showed side effect on the nutritional values of the two treated milk powder samples including protein, fat, vitamin D, Calcium and total sugar amount. The results showed that most of nutritional values were not affected by UV treatment up to 45 minutes of exposure, while showed slight effect after 60 minutes of exposure. On the other hand, gamma irradiation showed noticeable changes on most of nutritional values from the first dose of exposure.
This study emphasized the importance of good hygienic packaging of milk powder in closed packed containers to keep it safe. Also, the study revealed that treatment either by UV (up to 60 minutes) or elevated doses of Gamma irradiation (up to 100 kGy) had a potential effect on reduction of microbial growth in milk powder samples with insignificant effect on reduction of aflatoxin M1 level to the acceptable limit based by standards, with some changes in samples physical properties and nutritional values. As this study proved that even high doses of irradiation treatment could not eradicate the present toxin. So that, the application of hygienic measures in packaging of milk powder is considered the gold standard for safe products.