Feasibility study of lecithin nanovesicles as spacers to improve the solubility of milk protein concentrate powder during storage

Novel methods to study the effect of protein content and dissolution temperature on the solubility of milk protein concentrate: Focused beam reflectance and ultrasonic flaw detector-based methods

ABSTRACTThe influence of spray-drying conditions on functional and reconstitution properties of sweetened yogurt powder was studied. Twenty experiments with different spray-drying conditions (140–180°C inlet air temperature, 0.3–0.6 L/h feed rate and 500–1000 kPa atomization pressure) were performed according to central composite experimental design. Analysis of experimental data of solubility and dispersibility of yogurt powder revealed negative correlation with inlet air temperature and atomization pressure. Solubility of powder was significantly (p < 0.05) affected by feed rate. Wetting time of powder increased significantly (p < 0.001) with the increase of spray-drying temperature. The bulk, tapped, and particle densities were in the range of 344.8–475.7, 551.7–782.5, and 1187.5–1666.7 kg/m3, respectively. A significant quadratic effect (p < 0.001) of inlet air temperature and atomization pressure was observed on bulk density. Particle density increased with the increase in inlet air temperature and atomization pressure (p < 0.001). The results of the present investigation has the credible evidence to support that the processing conditions viz. inlet air temperature and atomization pressure decreased the water activity and flow property of the sweetened yogurt powder, whereas feed rate showed positive effect.

This study was conducted to optimize the production of spray-dried white dragon fruit (Hylocereus undatus) powder using resistant maltodextrin as wall material. The inlet air temperature (140 °C, 150 °C and 160 °C), outlet temperature (75 °C, 80 °C and 85 °C) and resistant maltodextrin concentrations (20%, 25% and 30%) were tested as independent variables. Process yield, moisture content, water activity, solubility, hygroscopicity and bulk density of the powders were analysed as responses. Process yield significantly (p&lt;0.05) increased with increasing inlet temperature and decreasing resistant maltodextrin concentration. Outlet temperature and resistant maltodextrin concentration significantly (p&lt;0.05) reduced the moisture content and water activity of the white dragon fruit powder. Powder solubility and hygroscopicity significantly (p&lt;0.05) increased as inlet and outlet temperature increased. Bulk density values decreased as inlet and outlet temperature increased. An optimum conditions for spray dried white dragon fruit powder that would produce high in yield, low moisture content, low water activity, high solubility, low hygroscopicity and high bulk density were found at 153 °C inlet temperature, 82 °C outlet temperature and 20% concentration.

The solubility of milk protein concentrate (MPC) powders was influenced by the method used for preparing the concentrate, drying conditions, and the type of dryer used. Increasing total solids of the ultrafiltered concentrates (23% total solids, TS) by diafiltration to 25% TS or evaporation to 31% TS decreased the solubility of MPC powders (80-83% protein, w/w dry basis), with ultrafiltration followed by evaporation to higher total solids having the greater detrimental effect on solubility. High shear treatment (homogenisation at 350/100bar, microfluidisation at 800bar or ultrasonication at 24kHz, 600watts) of ultrafiltered and diafiltered milk protein concentrates prior to spray drying increased the nitrogen solubility of MPC powders (82% protein, w/w dry basis). Of the treatments applied, microfluidisation was the most effective for increasing nitrogen solubility of MPC powders after manufacture and during storage. Manufacture of MPC powders (91% protein, w/w dry basis) prepared on two different pilot-scale dryers (single stage or two stage) from milk protein concentrates (20% TS) resulted in powders with different nitrogen solubility and an altered response to the effects of microfluidisation. Microfluidisation (400, 800 and 1200bar) of the concentrate prior to drying resulted in increased long term solubility of MPC powders that were prepared on a single stage dryer but not those produced on a two stage spray dryer. This work demonstrates that microfluidisation can be used as a physical intervention for improving MPC powder solubility. Interactions between the method of preparation and treatment of concentrate prior to drying, the drying conditions and dryer type all influence MPC solubility characteristics.

The effects of high pressure (HP) treatment (100-400 MPa at 10-60 °C) on the solubility of milk protein concentrate (MPC) powders were tested. The solubility, measured at 20 °C, of fresh MPC powders made with no HP treatment was 66%. It decreased by 10% when stored for 6 weeks at ambient temperature (~20 °C) and continued to decrease to less than 50% of its initial solubility after 12 months of storage. Of the combinations of pressure and heat used, a pressure of 200 MPa at 40 °C applied to the concentrate before spray drying was found to be the most beneficial for improved solubility of MPC powders. This combination of pressure/heat improved the initial cold water solubility to 85%. The solubility was maintained at this level after 6 weeks storage at ambient temperature and 85% of the initial solubility was preserved after 12 months. The improved solubility of MPC powders on manufacture and on storage are attributed to an altered surface composition arising from an increased concentration of non-micellar casein in the milk due to HP treatment prior to drying. The improved solubility of high protein powders (95% protein) made from blends of sodium caseinate and whey protein isolate compared with MPC powders (~85% protein) made from ultrafiltered/diafiltered milk confirmed the detrimental role of micellar casein on solubility. The results suggest that increasing the non-micellar casein content by HP treatment of milk or use of blends of sodium caseinate and whey proteins are strategies that may be used to obtain high protein milk powders with enhanced solubility.

The aim of this study was to evaluate the effect of air outlet temperature (75 and 85 °C) and milk type on proximate composition, water activity, particle size distribution, color, and rehydration ability of spray-dried skim dromedary and cow’s milk powders. While the water activity of powders was close to 0.4 when spray-dried at 75 °C air outlet temperature, it ranged from 0.2 to 0.3 for a production at 85 °C air outlet temperature. Skim dromedary milk powder had a lower water activity than skim cow’s milk powder after spray-drying at 85 °C air outlet temperature. Spray-drying yields were greater at the higher air outlet temperature (85 °C) for both skim milk powders. The particle size distributions of spray-dried skim milk powders were centered around 14–20 µm. The particles of skim dromedary milk powders were smaller than those of skim cow’s milk powders as skim dromedary milk was less viscous, leading to smaller sprayed droplets. No significant influence of spray-drying conditions on particle size distribution was observed for dromedary milk powders. Regardless of the spray-drying conditions and the milk type, the produced powders were very bright and had a low color saturation. Scanning electron microscopy images showed that spray-dried powders appeared as agglomerates of small particles with angular shapes rather than individual particles. All investigated spray-dried powders were considered non-wettable, hardly dispersible, and fairly soluble. Skim dromedary milk powder produced at 85 °C air outlet temperature showed a significantly higher solubility index than the same formulation spray-dried at 75 °C outlet air temperature. The opposite was obtained for skim cow’s milk powder. These results demonstrated that the outlet drying air temperature significantly influenced water activity, spray-drying yield and solubility of spray-dried dairy powders.

Soluble and insoluble fish protein powders were made from arrowtooth flounder (AF) fillets using three methods, which were heating and fractionation, enzymatic hydrolysis and alkali protein extraction. The AF powders were compared, and physical, chemical and rheologic properties were evaluated. The alkali protein extraction soluble (AES) (89.6%) and enzymatic hydrolysis soluble (EHS) (84.8%) powders had higher protein contents than other protein powders (72.6–77.8%). Both heating and fractionation soluble (HFS) and heating and fractionation insoluble powders were whiter than the other protein powders. HFS and EHS had the highest nitrogen solubility values, and EHS had the highest emulsion stability values. Sodium dodecyl sulfate electrophoresis indicated AES and alkali protein extraction insoluble protein powders had more high molecular weight protein bands, while EHS, enzymatic hydrolysis insoluble and HFS protein powders were substantially hydrolyzed and had an abundance of low molecular weight peptides. The flow and viscoelastic properties of the emulsions prepared with soluble AF were investigated using a parallel plate rheometer. The power law model was used to determine the flow behavior index (n) and consistency index (K). The emulsion containing AES had the highest K value (85.3 Pa·s) and the lowest value was for EHS (27.3 Pa·s). Soluble arrowtooth powders exhibited pseudoplastic behavior and viscoelastic characteristics. PRACTICAL APPLICATIONS There is an abundance of arrowtooth flounder (AF); however, its utilization as human food is challenging because of the proteases that reduce texture during cooking. Methods of processing are needed to convert the fish into more marketable forms. One alternative is to produce purified protein powder and high-protein ingredients for human consumption. Fish provide an excellent source of very digestable and high-quality protein. Isolated fish protein powders have desirable functional properties, such as the ability to hold water and fat, and emulsifying capacities. Protein from AF can be converted into a high-value protein powder food ingredient. The application of these ingredients could include incorporation into muscle tissue products by injection, tumbling and coating.

Results are presented which show that the water formed during the combustion of hydrocarbon fuel is significant in relation to the evaporation potential of the fuel when used in a direct gas‐fired drier. As a result, the outlet air humidity of direct‐fired driers is higher than that of indirect‐fired plant operating at the same outlet and inlet air temperatures. The powder moisture increases with increasing humidity at constant temperature. To compensate for this increase in moisture content, either the drier must be run at a lower inlet temperature throughout, or the outlet temperature of the drier must be increased. However, with heat sensitive materials such as milk a serious loss in powder solubility can occur if the latter action is chosen. These results suggest that the difference in overall efficiency of direct and indirect forms of heating in spray driers is less than has previously been assumed.

The most widely used technique for dehydration of dairy products is spray drying. This is an effective method for preserving biological products as it does not involve severe heat treatment and allows storage of powders at an ambient temperature. The maximum moisture content of a dairy powder (max 4% for skim milk powder) is defined in the product specification in relation to the water activity, and this must be close to 0.2 at 25 °C for optimum preservation. From an economic point of view, it is very important to operate as closely as possible to this limit. Many dairy manufacturers and researchers have demonstrated and reported that powder moisture is related to the outlet air temperature, but this is not always true. The aims of this study were to evaluate the direct and indirect relationships between outlet air temperature and moisture content of skim milk powder in relation to the spray-drying parameters (concentrate mass flow rate, absolute humidity of inlet air and inlet air temperature) using a thermodynamic approach. Our experiments showed that moisture content of skim milk powder can be close to 5.1 ± 0.0% with variations in outlet air temperature of 77 to 87 °C. Other experiments showed that the powder moisture content can vary from 4.6 ± 0.0% to 5.2 ± 0.0% even when the outlet air temperature remains close to 86 ± 1 °C. These results indicate that there is no direct relationship between outlet air temperature and powder moisture content. It is preferable to use the Enthalpic Mollier-Ramzine diagram of wet air and certain transfer equations related to the Fick and Fourier laws to demonstrate that the powder moisture content is directly related to the relative humidity (RH) of the outlet air. The moisture content and water activity of skim milk powder were close to 5.1 ± 0.0% and 0.27 ± 0.01 for outlet air RH close to 7.0 ± 0.1%, respectively, whatever the other drying parameter values. We demonstrated in this study that control of the RH of the outlet air is at least as important as control of the outlet air temperature to optimize the moisture content of a dairy powder, regardless of the absolute humidity of the inlet air, concentrate mass flow rate or inlet air temperature.

Changes in the physical properties, solubility, and heat stability of milk protein concentrates prepared from partially acidified milk

Effects of spray-drying conditions on the chemical, physical, and sensory properties of cheese powder

Effect of NaCl addition during diafiltration on the solubility, hydrophobicity, and disulfide bonds of 80% milk protein concentrate powder

Effect of diets containing tuna head hydrolysates on the survival and growth of shrimp Penaeus vannamei

Experimental and numerical study of a vertical earth-to-air heat exchanger system integrated with annular phase change material

Application of front-face fluorescence spectroscopy as a tool for monitoring changes in milk protein concentrate powders during storage