The compositional and physicochemical properties of different whey permeate (WPP), demineralised whey (DWP) and skim milk powder (SMP) size fractions were investigated. Bulk composition of WPP and DWP was significantly (P < 0.05) influenced by powder particle size; smaller particles had higher protein and lower lactose contents. Microscopic observations showed that WPP and DWP contained both larger lactose crystals and smaller amorphous particles. Bulk composition of SMP did not vary with particle size. Surface composition of the smallest SMP fraction (<75 µm) showed significantly lower protein (-9%) and higher fat (+5%) coverage compared with non-fractionated powders. For all powders, smaller particles were more susceptible to sticking. Hygroscopicity of SMP was not affected by particle size; hygroscopicity of semi-crystalline powders was inversely related to particle size. This study provides insights into differences between size fractions of dairy powders, which can potentially impact the sticking/caking behaviour of fine particles during processing.

The objective of this study was to determine the effect of changing viscosity and glass transition temperature in the continuous phase of nanoemulsion systems on subsequent stability. Formulations comprising of β-casein (2.5%, 5%, 7.5%, and 10% w/w), lactose (0% to 20% w/w), and trehalose (0% to 20% w/w) were generated from Design of Experiments (DOE) software and tested for glass transition temperature and onset of ice-melting temperature in maximally freeze-concentrated state (T(g) ' & T(m) '), and viscosity (μ). Increasing β-casein content resulted in significant (P < 0.0001) increases in viscosity and T(m) ' (P= 0.0003), and significant (P < 0.0001) decreases in T(g) '. A mixture design was used to predict the optimum levels of lactose and trehalose required to attain the minimum and maximum T(g) ' and viscosity in solution at fixed protein contents. These mixtures were used to form the continuous phase of β-casein stabilized nanoemulsions (10% w/w sunflower oil) prepared by microfluidization at 70 MPa. Nanoemulsions were analyzed for T(g) ' & T(m) ', as well as viscosity, mean particle size, and stability. Increasing levels of β-casein (2.5% to 10% w/w) resulted in a significant (P < 0.0001) increase in viscosity (5 to 156 mPa.s), significant increase in particle size (P= 0.0115) from 186 to 199 nm, and significant decrease (P= 0.0001) in T(g) ' (-45 to -50 °C). Increasing the protein content resulted in a significant (P < 0.0001) increase in nanoemulsion stability. A mixture DOE was successfully used to predict glass transition and rheological properties for development of a continuous phase for use in nanoemulsions.

The present study was conducted to analysis the quality indicators of cow's milk both in open market and processing industries in Bangladesh. Total 84 samples of fluid milk (15 samples from the open market of each district are Sirajganj, Pabna, Tangail and Dhaka and 6 samples of pasteurized milk of 4 different brands) were collected. The determination of physicochemical properties, microbial quality and presence of adulterant of all milk samples were carried out. Highest average milk fat was found in the raw milk collected from the open market at Dhaka district and in Brand 4 as 4.2% and 3.55% respectively. The lowest corrected lactometer reading (CLR) was found in Sirajganj as 25.5. A few of the pasteurized milk and open market milk were being adulterated by skimmed milk, sugar, added water and soda and alcohol respectively. Results pertaining to the enumeration of E.coli, Salmonella and V. Cholera exhibited 56.66%, 45% and 10% of samples of open market and 12.5%, 8.33% and 4.17% of samples of brands respectively. Due to unhygienic milking practice and very poor sanitary facilities, the highest amount of total plate count was 7.9 x 10 6 cfu/ml at Sirajganj district.