Acid gels

Pish protein concentrate and soy protein concentrate have been used to prepare a low phenylalanine, high tyrosine peptide for use with phenylketonuria patients (150). The process includes pepsin hydrolysis at pH 1.5 ptonase hydrolysis at pH 6.5 to Hberate aromatic amino acids gel filtration on Sephadex G-15 to remove aromatic amino acids incubation with papain and ethyl esters of L-tyrosine and L-tryptophan, ie, plastein synthesis and ultrafiltration (qv). The plastein has a bland taste and odor and does not contain free amino acids. Yields of 69.3 and 60.9% from PPG and soy protein concentrate, respectively, have been attained. 

Solvent Recovery. A mixture of methanol and methyl acetate is obtained after saponification. The methyl acetate can be sold as a solvent or converted back into acetic acid and methanol using a cationic-exchange resin such as a cross-linked styrene—sulfonic acid gel (273—276). The methyl acetate and methanol mixture is separated by extractive distillation using water or ethylene glycol (277—281). Water is preferred if the methyl acetate is to be hydroly2ed to acetic acid. The resulting acetic acid solution is concentrated by extraction or a2eotropic distillation. 

Liquid Water Linde Type 4 A Linde Type 5 A Activated Alumina Silicic Acid Gel... 

The concomitant use of various bleaching agents has also been shown to improve PIH. In 1975, tretinoin in combination with hydroqui-none and dexamethasone was reported as an effective treatment for PIH [14]. In a small study, the application of 2% hydroquinone and 10% glycolic acid gel twice daily and 0.05% tretinoin cream at night has been shown to provide benefit for darker-skinned patients with PIH [15]. Similarly, Yoshimura et al. [16] suggested efficacy of tretinoin combined with hydroquinone and lactic acid in reducing PIH. More re-... 

Elewski B, Fleischer AB, Pariser DM (2003) A comparison of 15% topical azelaic acid gel and 0.75% metronidazole gel in the topical treatment of papu-lopustular facial rosacea results of a randomized trial. Arch Dermatol 139 1444-1450... 

Approximate results obtained by Katchalsky, Lifson, and Eisen-berg o swelling in water of poly-(methacrylic acid) gels cross-... 

Fig. 137.—Equilibrium swelling ratio qm of poly-(methacrylic acid) gels prepared by copolymerizing methacrylic acid with 1, 2, and 4 percent (upper, middle, and lower curves, respectively) of divinylbenzene plotted against degree of neutralization i with sodium hydroxide. (Katchalsky, Lifson, and Eisenberg. )...

One example is silicate cement where orthosilicic acid, chemically generated in solution, condenses to form a silicic acid gel. Another is refractory cement where a cementitious product is formed by the heat treatment of an acid orthophosphate, a process which again involves condensation to form a polyphosphate. 

J Hasa, M Ilavsky. Deformational, swelling, and potentiometric (methacrylic acid) gels. II. Experimental results. J Polym Sci Polym Phys Ed 13 263-275, 1975. 

Pabley, A.S. and Holcomb, D.L. "A New Method of Acidizing or Acid Fracturing Crosslinked Acid Gels," 1980 Proc. Annu. Southwest. Pet. Short Course, Lubbock, April 17-18, 31 38. 

Shiino D, Murata Y, Kubo A et al (1995) Amine containing phenylboronic acid gel for glucose-responsive insulin release under physiological pH. J Control Release 37 269-276... 

Another use of pectin is when making a fruit flan or an open tart. These products are often coated with a pectin jelly based on a high methoxyl pectin. The pectin is dispersed and heated to dissolve it. As high methoxyl pectin requires an acid pH to set, just before use acid is added and the pectin mixture is poured over the flan. These fruit products are expected to be acid as part of the fruit flavour, so an acid gel is acceptable. 

FIG. 26 Observed water self-diffusion coefficients as a function of the protein concentration (g protein/g water) for micellar casein dispersions ( ), for acid gels (O), and for rennet gels ( ) [reproduced with permission from Mariette et al (2002)]. 

Pectin.—This general term has been retained to designate pectinic acids which will form the customary pectin-sugar-acid gels. 

A client asks for a salicylic acid gel he is buying for his mother for the removal of corns and calluses. 

Bikker, J.F., Anema, S.G., Li, Y., Hill, J.P. (2000). Rheological properties of acid gels prepared front heated milk fortified with whey protein mixtures containing the A, B and C variants of p-lactoglobulin. International Dairy Journal, 10, 723-732. 

Polyurethane Hydrogel Cross-Linked Polyacrylamide Gels Cross-Linked Polyacrylic Acid Gels... 

A hydrogel placed in an excess of water will absorb the liquid until it reaches a maximum. This ability is typically reported as the percent water in a fully swollen gel. The hydrophilicity of the polymer and the degree of cross-linking determine the degree to which the gel will absorb. Some hydrogels contain as much as 99% water. An acrylic acid gel will have a higher equilibrium moisture than a polyvinyl alcohol gel. This characteristic is not unlike the hydrodynamic volume factor described above. 

FIGURE 8.5 Effects of ions on polyacrylic acid gels. 

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