Protein particle size

Theie aie only a few fat replacement products based on protein. LITA is a com protein—polysaccharide compound the role of the polysaccharide is to stabilize the protein (zein). The final product is 87% protein and 5% polysaccharide. The mixture, spray dried after processing, claims to look like cream on rehydration. It is low in viscosity, flavor, and lubricity, and is stable to mild heating. The protein particle size is 0.3—3 p.m (55). 

Protease-resistant isoform of a host-encoded protein Particle size distribution analyser... 

Figure 4 summarizes the residual activities of proteins obtained after GAS and PCA processing. The only reports of protein activity greater than 80% are for insulin, ribonuclease A, lysozyme, and trypsin. These proteins are relatively small, having molecular weights of 5.8, 13.7, 14.4, and 23.8 kDa, respectively. Other larger proteins have been precipitated in the form of 1-5-pm-sized particles, but none have retained substantial activity. Further, from the limited studies available, we can conclude that the protein particle size is a function of the operating temperature (102) and the activity of the reconstituted protein is inversely related to its molecular weight (Fig. 4). The analysis presented below attempts to describe the interrelated causes of reduction in protein activity during C02-based processing.

Increasing protein particle size increases the rate of protein release (Table 9.2 and Figure 9.12). The size of the protein particles in the matrix affects the size of the water-filled channels formed as the particles dissolve. Larger particles occupy more volume in a matrix, increasing the pore-to-pore connectivity. Increased connectivity provides simpler pathways (i.e., less tortuous and less constricted pathways) for diffusion of protein molecules [16, 36, 40]. This can be seen in Table 9.2 for a variety of proteins as the average particle size increases, the overall tortuosity (Ft) decreases. 

Dangaran, K.L., Cooke, P., Tomasula, P.M. The effect of protein particle size reduction on the physical properties of C02-precipitated casein films. J. Food Sci. 71, 196—201 (2006)... 

To quantitate the influence of polymer molecular weight, protein loading, and protein particle size on the rate of release, calculated overall tortuosities (Ft) were compared for release from matrices where only one of these parameters was varied (Fig. 4). The tortuosity was greatly influenced by the molecular weight of the polymer (Ft Mfr Fig. 4a). Particle size and the loading also strongly influence the overall tortuosity (Ft <=< size and Ft oc loading-2 5 Fig. 4b, c). 

Support Pore size (nm) Mol. wt exclusion limit foi globular proteins Particle size (gm) Column sizes Length (cm) i.d. (mm) Chemical nature Availability bulk material Manufactured ... 

Another example is the purification of a P-lactam antibiotic, where process-scale reversed-phase separations began to be used around 1983 when suitable, high pressure process-scale equipment became available. A reversed-phase microparticulate (55—105 p.m particle size) C g siUca column, with a mobile phase of aqueous methanol having 0.1 Af ammonium phosphate at pH 5.3, was able to fractionate out impurities not readily removed by hquid—hquid extraction (37). Optimization of the separation resulted in recovery of product at 93% purity and 95% yield. This type of separation differs markedly from protein purification in feed concentration ( i 50 200 g/L for cefonicid vs 1 to 10 g/L for protein), molecular weight of impurities (<5000 compared to 10,000—100,000 for proteins), and throughputs ( i l-2 mg/(g stationary phasemin) compared to 0.01—0.1 mg/(gmin) for proteins). 

The largest class of processes appHed to farm commodities are separations, which are usually based on some physical property such as density, particle size, or solubiHty. For example, the milling process for cereal grains involves size reduction (qv) foUowed by screening to yield products that have varied concentrations of starch, fiber, and protein. Milling of water slurries is practiced to obtain finer separation of starch, fiber, protein, and oil. 

Fat Replacers. The reduction of fat in substitute dairy products results in an increase in water and a stress on the food system both in respect to body and texture, and to flavor. There is no universal fat replacer, but microparticulated proteins having particle sizes <10 fim and/or starch derivatives, and gums have been used as fat replacers. 

Whey proteins that have been heat precipitated under very high shear have a particle size between 1 and 3 micrometers, and give the impression of fat in some products. These microparticulated whey proteins are being used as fat replacers in frozen desserts and processed cheese substitutes. 

Sephadex. Other carbohydrate matrices such as Sephadex (based on dextran) have more uniform particle sizes. Their advantages over the celluloses include faster and more reproducible flow rates and they can be used directly without removal of fines . Sephadex, which can also be obtained in a variety of ion-exchange forms (see Table 15) consists of beads of a cross-linked dextran gel which swells in water and aqueous salt solutions. The smaller the bead size, the higher the resolution that is possible but the slower the flow rate. Typical applications of Sephadex gels are the fractionation of mixtures of polypeptides, proteins, nucleic acids, polysaccharides and for desalting solutions. 

Petanate, A.M. and Glatz, C.E., 1983. Isoelectric precipitation of soy protein. I. Factors affecting particle size distributions. II. Kinetics of protein aggregate growth and breakage. Biotechnology and Bioengineering, 25, 3049. 

TSK-GEL column Particle size (/tm) Average pore size (A) Polyethylene oxides/glycols Molecular weight of sample Dextrans Globular proteins ... 

In addition it should be added that microdisperse forms of CP can precipitate proteins from solutions. Figs. 21-23 show that CP microdispersions with particle size of 1-2 pm precipitate serum albumin from solutions [81] in complete agreement with general flocculation laws for polyelectrolytes. The figs, show an extreme... 

The resolution of these columns for protein mixtures, however, was comparably poor. The peak capacity for human serum albumin was near 3 during 20 min gradient elution. Improvement has been reached by covalent binding of PEI (M = 400-600) onto a 330 A silica of 5 pm particle size [38], The peak capacities of ovalbumin and 2a -arid glycoprotein were 30-40 (tgradienl = 20 min). Enhanced peak capacity and resolution probably were due to the more diffuse structure of PEI coupled to silane moieties than that of strictly adsorbed on silica and cross-linked (see Sect, 2.2). Other applications of covalently adsorbed PEI are discussed in Sect. 4.1. 

For the preparation of nanoparticles based on two aqueous phases at room temperature one phase contains chitosan and poly(ethylene oxide) and the other contains sodium tripolyphosphate. The particle size (200-1000 nm) and zeta potential (between -i- 20 mV and -l- 60 mV) could be modulated by varying the ratio chitosan/PEO-PPO. These nanoparticles have great proteinloading capacity and provide continuous release of the entrapped protein (particularly insulin) for up to one week [100,101]. 

Fig. 1. Relationship between reactor mean velocity gradient and particle size for isoelectric soya protein precipitate. Open symbols represent precipitate diameter for 50% oversize Closed symbols represent precipitate diameter for 90% oversize [51]...

The Water Unextractable Solids were isolated from dehulled, defatted, untoasted soy bean meal (particle size < 0.5 mm) by removal of cold water solubles, proteins and starch. The soy bean meal was extracted with cold water, a solution containing sodium dodecylsulphate and 1,4-dithiothreitol, and incubated with a-amylase, to yield the CWS, SDSS and HWS... 

Diffusion and sedimentation measurements on dilute solutions of flexible chain molecules could be used to determine the molecular extension or the expansion factor a. However, the same information may be obtained with greater precision and with far less labor from viscosity measurements alone. For anisometric particles such as are common among proteins, on the other hand, sedimentation velocity measurements used in conjunction with the intrinsic viscosity may yield important information on the effective particle size and shape. ... 

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