Polyacrylamide gel electropheresis and thin layer chromatography (TLC) were applied to detect the fate of aflatoxin B-1 in milk fermented with an active culture of Streptococcus lactis (ATCC-11454). TLC analysis revealed the formation of two fluorescent metabolites (B2a and R0) in fermented milk. Electropheretic analysis of both casein and whey protein showed fluorescent bands in the region of Kappa-casien and immunoglobulin which are glycoproteins in nature. The transformation of B-1 to the nontoxic metabolite B2a and the less toxic compound aflatoxicol (R0) reflects the preference for fermented dairy products in consumption in order to reduce chances of toxicity.

The effects of substituting milk fat with different levels of inulin as a fat replacer on the chemical, microbiological and sensory characteristics of yoghurt were examined. Samples of yoghurt were kept in refrigerator at (5± 2Cº), and examined when fresh, and after 2, 3 and 7 days of storage. Chemical composition, microbiological contents and sensory characteristics were examined. The obtained results indicated that addition of inulin resulted in a significant increase in the total solids, moisture contents, and the development of titratable acidity. On the other hand, less whey syneresis was observed during the storage of the yoghurt samples. On the other hand, replacing of milk fat by inulin was of no significant effect on the fat content. Addition of inulin stimulated the growth of lactic acid bacteria. The colony forming units of total bacterial counts, Lactobacillus delbrueckii ssp. bulgaricus and Streptococcus thermophilus increased up to the 3 rd day of storage period, followed by decrease up to the end of the storage period. Sensory evaluations were almost stable during the first 7 th days of storage, then decreased slightly until the end of storage the period. Yoghurt samples containing 1.2% of inulin showed minor difference in the sensory characteristics, compared with control, and of the most acceptable sample. In conclusion, inulin could be successfully used as a fat replacer in making of low fat yoghurt with additional nutritional benefits without affecting the physico-chemical properties of yoghurt.

A total of 36 samples of Laban Rayeb were collected from 12 different small dairy plants in Assuit Governorate. samples were analyzed for their chemical composition and microbiological quality. The Results showed that the average values of acidity %, moisture, total solids, fat, total nitrogen, soluble nitrogen, soluble nitrogen coefficient were 1.1, 88.29, 11.66, 2.41, 0.52, 0.17 and 4.87, respectively. Moreover, microbiological analysis revealed that the log 10 of total bacteria count ranged from 7.03 to7.21cfu, counts of lactic acid bacteria counts ranged from 5.781 to 6.353cfu, and the coccus group ranged from 5.83 to 6.29cfu and proteolytic bacteria ranged from 4.36 and 6.89cfu. Finally, yeasts and moulds count ranged from 0.00 to 5.21cfu in fresh Rayeb milk samples. Coliform bacteria couldn't be detected in all of the examined samples.

The proteolytic activity of five (ATCC) strains of lactic acid bacteria were investigated in the presence of different concentrations of aflatoxin B-1. The presented data revealed that aflatoxin in milk can affect the lactic acid bacteria which are used in the manufacture of dairy products. Such effect depends on toxin concentration and the species of lactic acid bacteria. This investigation is of practical value because it may explain the effect which occurs during cheese manufacture. This defect can be characterized by off flavour which can be very undesirable for a ripened cheese.

This work was conducted in order to study the kinetic behaviour of dietary aflatoxins in the colostrum of a pregnant cow exposed to contaminated feeds for a short period. In this study, two pregnant cows received a single dose of dietary aflatoxins in the form of rice powder contained 31.20 ppm aflatoxin B and 19.68 ppm aflatoxin G during the last stage of pregnancy, at about two weeks before parturition. Samples of colostrum were collected from dams and assayed for the presence of toxic metabolites as well as its conjugations by electrophoretic analysis. The results revealed that the intake of aflatoxins appeared in the colostrum postpartum as AFM1 and also AFB2a which is a non toxic metabolite. Moreover, it was found that the excreted metabolites including AFB2a were conjugated to the immunoglobulin protein fraction of the colostrum. The significance of the obtained results to the newborn calf are discussed.