The objective of this study was to characterize lactose crystallization behaviour and microstructure of spray dried nanoemulsions with different fat globule sizes (FGS). Powders of the same composition (57.7% w/w lactose, 12.3% w/w sodium caseinate, 27.7% w/w sunflower oil, and 2.3% w/w water) but different FGS (mean diameters 1100nm and 155nm) prior to spray drying were manufactured. Differences in lactose crystallization were studied using dynamic vapour sorption (DVS) and polarized light microscopy (PLM). Crystallization kinetics was modelled using the Avrami and Yang equations. Results showed that lactose crystallized in three dimensions and more rapidly in powders with a smaller FGS. PLM images showed a higher rate of lactose crystal formation for smaller FGS powders when stored for 4 days at 55% relative humidity. Confocal laser scanning microscopy (CLSM) and cryo-scanning electron microscopy (Cryo-SEM) images indicated the more evenly distributed small fat globules inside powder particles prepared from spraydried nanoemulsions. The surface of powder particles was uneven and ruptured post lactose crystallization. Crystals appeared after humidification and were assumed to be anhydrous α- and β-lactose in a 5:3 molar ratio. Results showed powder particles of the same composition were altered in lactose crystallization characteristics by changing the FGS of emulsions pre spray drying.

Lipid oxidation can adversely alter sensory and nutritional attributes of fats preserved in food powders. The aim of this study was to compare the extent of lipid oxidation in spray dried conventional emulsions and nanoemulsions. Powders containing lactose or lactose/sucrose (7:3) (57.9 g/100 g), sodium caseinate (12.4 g/100 g), sunflower oil (27.9 g/100 g) and water (1.8 g/100 g) were manufactured from control emulsions (D[4, 3] similar to 1100 nm) and nanoemulsions (FGS similar to 155 nm). A gas chromatographic headspace solid-phase microextraction (HS-SPME) method was validated and subsequently used to determine levels of volatile compounds pentanal and hexanal as indicators of lipid oxidation in powders stored over a 24 month period. Occluded air was significantly (P < 0.05) lower and interstitial air significantly higher (P < 0.05) in powders made from nanoemulsions. Levels of pentanal and hexanal were significantly (P < 0.05) reduced in powders made from nanoemulsions compared to those from control emulsions, due to their altered structure, lower porosity, and lower free fat. Partial replacement of lactose with sucrose may have also reduced pentanal and hexanal. (C) 2015 Elsevier Ltd. All rights reserved.

A whey protein ingredient, in which β-lactoglobulin was selectivity hydrolysed, was evaluated during manufacturing of infant formulae. Three model infant milk formula (IMF) powders were produced containing: non-hydrolysed (NH) proteins (60:40; whey proteins:caseins); partially hydrolysed (PH) caseins and whey proteins; and selectively hydrolysed (SH) whey proteins. After homogenisation, particle size (D[4,3]) of the SH formulae was similar (P > 0.05) to NH formulae and was significantly (P < 0.05) smaller than PH formulae. Prior to spray drying (∼55% w/w), the viscosity of SH formulae (14.8 ± 0.3 mPa s) was significantly lower (P < 0.05) than that of the NH (48.6 ± 0.8 mPa s) or PH formulae (27.6 ± 1.5 mPa s). Surface free fat, wettability and glass transition temperature of powders were not significantly (P > 0.05) different. IMF manufactured with SH ingredients have applications in high dry matter processes with potential for reduced energy costs in spray drying.

The aim of this study was to determine the effects of ultrasound on the dissolution properties of milk protein concentrate (MPC) powders. A high intensity ultrasound (20 kHz; power 70.2 W) was used to dissolve MPC powder and the dissolution rate was compared to conventional methods of dispersion (e.g., stirring). Rehydration of MPC by stirring at 50 degrees C complied with the 2-step dissolution model whereby the disappearance of larger particles coincided with the formation of smaller ones over time. MPC dispersal by sonication dramatically accelerated this process, achieving >90% levels of powder solubilisation. Temperature rise (>70 degrees C) during sonication causes protein denaturation and aggregation, but this can be alleviated using thermal dissipation. Overall, the use of a combination rehydration process for MPC powders involving (i) conventional dissolution (stirring) for 10 min at 50 degrees C followed by (ii) ultrasonication (<50 degrees C) for 1 min (energy density 21.1 J/mL) can achieve rapid powder dissolution. (C) 2013 Elsevier Ltd. All rights reserved.

The objective of this study was to investigate the physicochemical properties of spray dried nanoemulsions having different final water and sugar contents. Formulations consisting of lactose or a 70:30 mixture of lactose: sucrose (23.9%), sodium caseinate (5.1%) and sunflower oil (11.5%) in water were heat treated (100 degrees C, 30 s), homogenized (17 MPa) or microfluidized (100 MPa) and spray dried at two different outlet temperatures (80 or 90 degrees C). Nanoemulsions produced by microfluidization were more stable and less viscous than control emulsions and had lower solvent extractable free fat. Increasing dryer outlet temperature reduced water content, water activity, particle size, tapped bulk density, with a consequent increase of onset temperature of glass transition (T-g) and crystallization (T-cr) of lactose in powders. Reduction of fat globule size by microfluidization lowered T-cr of lactose, an effect attributed to the lower level of protein in the continuous phase. Partial replacement of lactose with sucrose decreased T-g and delayed crystallisation. The study demonstrated that the physical properties of powders can be altered by reducing the fat globule size of emulsions pre spray drying. (C) 2013 Elsevier Ltd. All rights reserved.

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.