Emulsifying capacity

The presence of a thermodynamically incompatible polysaccharide in the aqueous phase can enhance the effective protein emulsifying capacity. The greater surface activity of the protein in the mixed biopolymer system facilitates the creation of smaller emulsion droplets, i.e., an increase in total surface area of the freshly prepared emulsion stabilized by the mixture of thermodynamically incompatible biopolymers (see Figure 3.4) (Dickinson and Semenova, 1992 Semenova el al., 1999a Tsapkina et al., 1992 Makri et al., 2005). It should be noted, however, that some hydrocolloids do cause a reduction in the protein emulsifying capacity by reducing the protein adsorption efficiency as a result of viscosity effects. 

Measurement the breakpoint (visual, sonic, electronic, etc.) and the amount of oil emulsified (capacity) to the breakpoint (volumetric, gravimetric, viscometric, etc.). 

Lin et al. ( 6) measured the emulsion capacity of defatted sunflower seed products. Data in Table VII show that sunflower flour was superior in emulsifying capacity to all other products tested. The emulsions were in the form of fine foams and were stable during subsequent heat treatments. The diffusion-extraction processes employed to remove phenolic compounds dramatically reduced emulsion capacity, although isolating the protein improved emulsion capacity to some extent. 

Figure 9. Effect of pH on emulsifying capacity of native and chemically modified (succinylation, acetylation) sunflower seed protein concentrates (47)...

Adler-Nissen and Olsen (40) studied the influence of peptide chain length on the taste anT functional properties of enzymatically modified soy protein. The emulsifying capacity of modified proteins could be improved significantly compared to unmodified control samples by controlling the extent of hydrolysis. 

Kuehler and Stine (43) studied the functional properties of whey protein with respect to emulsifying capacity as affected by treatment with three proteolytic enzymes. Two microbial proteases and pepsin were examined. The emulsion capacity decreased as proteolysis continued, suggesting that there is an optimum mean molecular size of the whey proteins contributing to emulsification. 

The hydrolyzed starches are inexpensive, bland in flavor, very soluble (up to 75 ), and exhibit low viscosity in solution. The major shortcomings of these products are a virtual lack of emulsifying capacity and marginal retention of volatiles. 

Emulsifying capacity Maximum amount of oil that can be emulsified by a protein solution before emulsion breakdown Emulsifying capacity = volume of oil emulsilied/wl. of protein... 

A.N. Gurov, M.A. Mukhin, N.A. Larichev, N.V. Lozinskaya and V.B. Tolstoguzov, Emulsifying properties of proteins and polysaccharides, I, Methods of determination of emulsifying capacity and emulsion stability, Colloids Surfaces 6 (1983) 35-42. 

A constitutively hydrophobic food fat is called upon to perform in a hydrophilic environment, suggesting the most important physical property to be its emulsifying capacity. Simultaneously, the fat is ingredient-compatible, heat-stable, and confers a smooth oral sensation. The basic assignment of a fat replacer is to mimic these properties through substitution for the fat s viscosity, texture, and the slippery, creamy, lubricious mouthfeel (Glicksman, 1991). One of the earliest fat substitutes to perform thus was Simplesse (Roller and Jones, 1996), a protein perceived to be of a creamy texture due to inherent 0.1-3.0-pm-diameter microparticles (Thayer, 1992). 

Tornberg and Ediriweera, 1987). Phase inversion temperature (Shinoda and Saito, 1969) and emulsifying capacity (Swift et al., 1961) have been used to evaluate the effects of low molecular weight and protein emulsifiers, respectively. Unfortunately, it is not possible to measure the size of the large droplets present in unhomogenized water-in-oil emulsions because the droplets coalesce very quickly. The phase inversion temperature is not a relevant test, as it may not be related directly to the stability to inversion at the emulsification temperature. Furthermore, it has been stated (Matsumoto and Sherman, 1970) that water-in-oil emulsions do not exhibit a true phase inversion temperature, unlike oil-in-water emulsions. 

Lipoproteins. These are combinations of lipids with protein and have excellent emulsifying capacity. Lipoproteins occur in milk and egg yolk. 

Emulsion Capacity. Enzymatic digestion of proteins beyond 10 min, except the trypsin-treated sample for 30 min, destroyed emulsifying capacity of the flour (Figure 13). Apparently, hydrolysis substantially altered protein surface activity strengths and the ability of the protein to stabilize oil-in-water emulsions. This assumption agrees with earlier work showing decreased emulsion capacity of peanut flour fermented with fungi (27). 

Succinylation increased the emulsifying activity and emulsion stability of soy and cottonseed proteins (12,38). The pH emulsifying capacity profiles of succinylated protein paralleled those of the solubility curves and in all cases the succinylated protein had about double the emulsifying capacity of the unmodified... 

The foaming and emulsifying capacity of yeast proteins have been studied (83,84). Rha et al. (85) have summarized the limited information on the spinning, i.e. fiber forming ability of proteins from C. utilis. 

Alkali treatment has been used to improve the functional properties of the insoluble protein prepared by heat precipitation of an alkaline extract of broken yeast cells (63). Heating yeast protein at pH 11.8 followed by acid precipitation (pH 4.5) yielded a preparation composed of polypeptides with increased aqueous solubility. It also increased foaming capacity of the protein 20-fold. The emulsifying capacity of the modified protein was good whereas the original insoluble protein was incapable of forming an emulsion. Alkali treatment must be carefully controlled to avoid its possible deleterious effects (24,75), e.g. alkaline treatment of yeast protein resulted in a loss (60%) of cysteine (63). 

The emulsifying capacity of the yeast proteins was progressively improved with the extent of succinylation (Table IX) as measured by the turbidimetric technique (89). The modified yeast proteins had excellent emulsifying activities compared to several other common proteins. McElwain et al. (88) observed that succinylation of yeast protein increased emulsion viscosity but decreased emulsion stability. 

The emulsifying properties of proteins have been a subject of concern for those dealing with functional properties of proteins. The studies so far have been restricted to two main approaches emulsifying capacity and emulsion stability measurements. The former measures the maximum oil addition until inversion or phase separation of the emulsion occurs, whereas the latter measures the ability of the emulsion to remain unchanged. 

The present work was carried out with the purpose of relating taste, solubility, emulsifying capacity, foaming capacity, and viscosity of soy protein hydrolysates to the DH of these hydrolysates. This tentative approach to the manufacture of functional soy protein hydrolysates was chosen, because DH is easily controlled during hydrolysis by means of the pH-stat technique (5), and because the properties of the hydrolysate are presumed to be related to the DH-value rather than to hydrolysis parameters such as temperature, substrate concentration, and enzyme-substrate ratio (6). 

Emulsifying Capacity. The method of Swift et al. (14) was used with slight modifications to determine the emulsifying capacity of the soy samples ... 

Later experiments (unpublished data) seem to confirm the existence of the maximum in emulsifying capacity described above, although the emulsifying capacities achieved on the individual hydrolysates exhibited a certain variation ( 15%, calculated from... 

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