Caseinic acid

The U.S. standards for grades of edible dry casein (acid) are presented in Title 7, Part 28, of the Code of Federal Regulation (FDA 1981B) with the following specifications Grades are determined on the basis of flavor and odor, physical appearance, bacterial estimates [standard plate count (SPC) and coliform count], protein content, moisture content, milk fat content, extraneous material, and free acid. 

Dry casein (acid) that fails to meet the requirements of U.S. standard grade, or contains Salmonella or coagulase-positive staphylococci, is considered unsuitable for human food and is not assigned a U.S. grade. 

The )8-carboline skeleton, occasionally hydroxylated at the 6 position appears to be quite popular in nature, and alkaloids of this type have also been found in mushrooms. First, as the result of a thorough examination of the composition of Amanita muscaria metabolites carried out by Eugster, the occurrence in this species of l,2,3,4-tetrahydro-l-methyl-j8-carboline-3-carboxylic acid was established (59). This compound (mp 296-298°C, [ ]d -115°), known also as tetrahydroharman-3-carboxylic acid, was earlier (173) identified as a component of casein acidic hydrolysis products and was prepared synthetically by condensation of tryptophan with acetaldehyde or with pyruvic acid followed by decarboxylation of the 1,3-dicarboxylic acid intermediate (Scheme 32). 

Anaerobic incubations similarly prepared from other media using anal sac inocula, were also tested. These media were Robertson s meat broth (RM), casein acid hydrolysate medium (CHY) and an egg yolk medium (EY) (fresh egg yolk/glucose/Difco brain-heart infusion broth 5/2/100 w/w/w). After incubation, all fermentations were stopped by the addition of excess solid sodium chloride, and maintained at 4 C until required for testing. 

Remove 25 ml. by means of a pipette, add a few drops of phenolphthalein the colour is pink. Now add very cautiously, drop by drop, dilute acetic acid (say Mjioo) until the pink colour has just not disappeared. It is important not to add too much acid, otherwise the casein will be precipitated. Now add 5 ml. of neutralised formalin (see p. 464) and then titrate with Mj 10 NaOH solution. Note the amount required. 

Minerals, particularly Bentonite, ate used to remove proteins that tend to cause haze in white wines. The natural tannin of ted wines usually removes unstable proteins from them. Excess tannin and related phenols can be removed and haze from them prevented by addition of proteins or adsorbents such as polyvinylpyttohdone. Addition of protein such as gelatin along with tannic acid can even be used to remove other proteins from white wines. Egg whites or albumen ate often used to fine ted wines. Casein can be used for either process, because it becomes insoluble in acidic solutions like wines. 

The sulfur amino acid content of soy protein can be enhanced by preparing plasteins from soy protein hydrolysate and sources of methionine or cystine, such as ovalbumin hydrolysate (plastein AB), wool keratin hydrolysate (plastein AC), or L-methionine ethyl ester [3082-77-7] (alkaU saponified plastein) (153). Typical PER values for a 1 2 mixture of plastein AC and soybean, and a 1 3 mixture of alkah-saponified plastein and soybean protein, were 2.86 and 3.38, respectively, as compared with 1.28 for the soy protein hydrolysate and 2.40 for casein. 

Two types of magnesia, caustic-calcined and periclase (a refractory material), are derived from dolomitic lime. Lime is required in refining food-grade salt, citric acid, propjiene and ethylene oxides, and ethylene glycol, precipitated calcium carbonate, and organic salts, such as calcium stearate, lactate, caseinate. 

Casein. Milk contains proteins and essential amino acids lacking in many other foods. Casein is the principal protein in the skimmed milk (nonfat) portion of milk (3—4% of the weight). After it is removed from the Hquid portion of milk, whey remains. Whey can be denatured by heat treatment of 85°C for 15 minutes. Various protein fractions are identified as a-, P-, and y-casein, and 5-lactoglobulin and blood—semm albumin, each having specific characteristics for various uses. Table 21 gives the concentration and composition of milk proteins. 

The enzymatic hydrolysates of milk casein and soy protein sometimes have a strong bitter taste. The bitter taste is frequently developed by pepsin [9001 -75-6] chymotrypsin [9004-07-3] and some neutral proteases and accounted for by the existence of peptides that have a hydrophobic amino acid in the carboxyhc terminal (226). The relation between bitter taste and amino acid constitution has been discussed (227). 

Soybean Protein Isolates. Soybean protein isolates, having a protein content of >90 wt%, are the only vegetable proteins that are widely used in imitation dairy products (1). Most isolates are derived from isoelectric precipitation, so that the soybean protein isolates have properties that are similar to those of casein. They are insoluble at thek isoelectric point, have a relatively high proportion of hydrophobic amino acid residues, and are calcium-sensitive. They differ from casein in that they are heat-denaturable and thus heat-labile. The proteins have relatively good nutritional properties and have been increasingly used as a principal source of protein. A main deterrent to use has been the beany flavor associated with the product. Use is expected to increase in part because of lower cost as compared to caseinates. There has been much research to develop improved soybean protein isolates. 

Fig. 3. Schematic process flow diagram for an imitation cheese product having the following formulation dry ingredients, calcium caseinate (or rennet casein), 24.5 wt % tapioca flour, 3.0 wt % salt, 2.16 wt % adipic acid, 0.6 wt % vitamins and minerals, 0.1 wt % sorbic acid (mold inhibitor), 0.5 wt % fat—color blend, soybean oil hydrogenated to a Wiley melting point of 36°C, 21.3 wt % lactylated monoglycerides, 0.05 wt % red-orange coloring, 0.01 wt...

Casein is one member of the important group of natural polymers, the proteins. These materials bear a formal resemblance to the polyamides in that they contain repeating —CONH— groups and could be formally considered as polymers of amino acids. However, unlike, polymers such as nylon 6 and nylon 11 a number of different a-amino acids are found in each molecule whereas the nylons 6 and 11 have only one oj-amino acid molecule (Figure 30.1). 

Over 30 amino acids have been identified in the hydrolysis product of casein of which glutamic acid, hydroxyglutamic acid, proline, valine, leucine and lysine comprise about 60%. The residues of the aminoacid arginine also appear to be of importance in the cross-linking of casein with formaldehyde. 

It is interesting to note that the amino acid side chains may be either neutral as in valine, acidic as in glutamic acid or basic as in lysine. The presence of both acidic and basic side chains leads to proteins such as casein acting as amphoteric electrolytes and their physical behaviour will depend on the pH of the environment in which the molecules exist. This is indicated by Figure 30.2, showing a simplified protein molecule with just one acidic and one basic side group. 

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