From high milk protein powders to the rehydrated dispersions in variable ionic environments: A review

Improving rehydration properties of spray-dried milk protein isolates by supplementing soluble caseins

Spray-dried milk protein isolates (MPIs) are important dairy ingredients but may not have desirable rehydration properties for industrial applications. In the present study, rehydration properties of MPIs were improved by spray-drying MPI dispersions containing different amounts of soluble caseins in the form of derivatized MPI (dMPI). dMPI was prepared by alkalizing MPI dispersions to pH 11.0 and subsequently acidifying to pH 6.8 (the pH-cycle). All the spray-dried MPIs had the similar bulk density (around 0.33 g/cm^-3), composition, size distribution (1-100 µm), and SEM morphology. However, the decrease of hydrodynamic diameter, dissolution of total solids and proteins, and disruption of particles during the dynamic rehydration were accelerated as the dMPI content increased, indicating the improved rehydration properties. The improvement in rehydration properties was not due to the wettability that decreased as the dMPI:MPI mass ratio changed from 0:8 to 8:0, but resulted from the reduced cross-linking of casein micelles on powder surface and the increased surface porosity during the hydration as observed for partially hydrated samples. The present work may assist industrial applications of spray-dried MPIs.

Insolubility in milk protein concentrates: potential causes and strategies to minimize its occurrence

Milk protein concentrates (MPCs), which are produced from skim milk following a series of manufacturing steps including pasteurization, membrane filtration, evaporation and spray drying, represent a relatively new category of dairy ingredients. MPC powders mainly comprise caseins and whey proteins in the same ratio of occurrence as in milk. While bovine MPCs have applications as an ingredient in several protein enriched food products, technofunctional concerns, e.g., reduced solubility and emulsification properties, especially after long-term storage, limit their widespread and consistent utilization in many food products. Changes in the surface and internal structure of MPC powder particles during manufacture and storage occur via casein-casein and casein-whey protein interactions and also via the formation of casein crosslinks in the presence of calcium ions which are associated with diminishment of MPCs functional properties. The aggregation of micellar caseins as a result of these interactions has been considered as the main cause of insolubility in MPCs. In addition, the occurrence of lactose-protein interactions as a result of the promotion of the Maillard reaction mainly during storage of MPC may lead to greater insolubility. This review focuses on the solubility of MPC with an emphasis on understanding the factors involved in its insolubility along with approaches which may be employed to overcome MPC insolubility. Several strategies have been developed based on manipulation of the manufacturing process, along with composition, physical, chemical and enzymatic modifications to overcome MPC insolubility. Despite many advances, dairy ingredient manufacturers are still investigating technical solutions to resolve the insolubility issues associated with the large-scale manufacture of MPC.

Chemical Lipophilization of Bovine α-Lactalbumin with Saturated Fatty Acyl Residues: Effect on Structure and Functional Properties

Bovine α-lactalbumin (α-LA) was chemically modified by the covalent attachment of fatty acid residues of different length (lauroyl, palmitoyl, and stearoyl) to modify its functional and antioxidant properties. Structural changes, functional properties, and antioxidant capacity in the pH interval between 3 and 10 were analyzed. Surface properties were improved. The esterification increased the hydrophobic interactions leading to a reduction in the solubility dependent on the incorporation ratio of the fatty acid residues. Improvement in emulsifying, foaming, and antioxidant properties were observed when the length of the fatty acid chains was short and mostly at a basic pH. With these results in mind, experiments could be conducted for the technological applications of these derivatives in the food, pharmaceutical, and cosmetic industries.

Effect of dairy powders fortification on yogurt textural and sensorial properties: a review

Yogurts are important dairy products that have known a rapid market growth over the past few decades. Industrial yogurt manufacture involves different processing steps. Among them, protein fortification of the milk base is elemental. It greatly enhances yogurt nutritional and functional properties and prevents syneresis, an undesirable yogurt textural defect. Protein enrichment can be achieved by either concentration process (evaporation under vacuum and membrane processing: reverse osmosis and/or ultrafiltration) or by addition of dairy ingredients. Traditionally, skim milk powder (SMP) is used to enrich the milk base before fermentation. However, increased quality and availability of other dairy ingredients such as milk protein isolates (MPI), milk protein concentrates (MPC) whey protein isolates (WPI) and concentrates (WPC), micellar casein (MC) and caseinates have promoted their use as alternatives to SMP. Substituting different dry ingredients for skim milk powder in yogurt making affects the yogurt mix protein composition and subsequent textural and sensorial properties. This review focuses on various type of milk protein used for fortification purposes and their influence on these properties.