Surface activity, film formation, and emulsifying properties of milk proteins

Abstract

This overview indicates that simple, reliable standardized methods for measuring emulsifying activity and for determining ES are not yet available. One of the major shortcomings of most of the current methods is the inability to detect very small fat globules (less than 0.5 micron), which may be very important in stable emulsions. Several of the methods are time consuming and destructive. To minimize the time required to evaluate emulsions, techniques that monitor instability under the influence of accelerated aging (increased temperature and gravitational field) have been used with varying degrees of success. These methods, e.g., centrifugation, are useful, but processes occurring during centrifugation or heating may not be characteristic of those occurring in a stored emulsion. Generally, there is no method that simultaneously determines changes in emulsions due to the aggregation coalescence, flocculation, creaming, of the droplets and/or oiling off. No single criterion of emulsion instability is sufficient to characterize all the changes occurring in the system. A nonintrusive technique that can monitor dynamic changes in emulsions is needed. Ideally, it should be simple, rapid, inexpensive, and applicable to both diluted and concentrated emulsions. Scientists must continue research to develop such a standard universal method for determining ES, because data from different laboratories cannot currently be validly compared. Reliable methods are also required to elucidate relationships between the physical properties of proteins as emulsifiers and their performance in food emulsions. There is a need for opportunities for systematic research to determine the interfacial behavior of food emulsifiers, particularly food proteins. Research to describe the kinetics and thermodynamics of adsorption at an interface, the extent of unfolding, the degree of packing and polypeptide interactions in an interface during film formation, and information concerning the physical and mechanical properties of interfacial films is needed to describe emulsifying behavior of different proteins. The effects of components in the continuous and discontinuous phase, parameters of manufacture, and interactions between different types of surface-active materials that occur in food need to be studied.

Optimization of dynamic loop mixer operating conditions for production of O/W emulsion for cell microencapsulation

“…The physico-chemical and functional properties of whey proteins have been extensively reviewed [19,24] and would appear to satisfy the requirements of an encapsulating agent. Microencapsulating properties of whey proteins have been investigated and reported in recent years [18,29].…”

Effects of Disulfide Reduction on the Emulsifying Properties of Bovine Serum Albumin

“…An emulsion with smaller droplet size is considered to be the most stable. 22 ) As shown in Fig. 2, the droplet size distribution was less heterogeneous with the emulsions of BSA reduced at 30 mM 2-ME than with those of native BSA and of the protein reduced at 200 mM 2-ME; by triplicate measurements, the profile was confirmed to be esentially the same for each BSA smaple.…”

“…The stability of an emulsion, however, also depends on the properties of the interfacial protein membrane or film. 22 ,23) Although at present we have no data on the properties of BSA at the interface of an emulsion, the protein reduced at 30 mM 2-ME may take the flexible state which is allowed at the interface of an emulsion to form a stable membrane or film consisting of a highly polymerized network or thick layer.…”

“…22) Proteins are adsorbed at interfaces in such a way that hydrophilic amino acids tend to orient toward the aqueous phase, whereas hydrophobic amino acids tend to associate with the lipid phase. 22 ,23) The present study demonstrates that the emulsifying properties of BSA can be improved in terms of particle size (Fig.…”

“…An emulsion comprises fat droplets enveloped by a continuous film of a surfactant material that stabilizes the droplets to prevent association and coalescence. 22 ,23) Emulsion stability is influenced by the conformational state of an absorbed protein.…”