Rennet process, casein production

Commercial casein is usually manufactured from skim milk by precipitating the casein through acidification or rennet coagulation. Casein exists in milk as a calcium caseinate-calcium phosphate complex. When acid is added, the complex is dissociated, and at pH 4.6, the isoelectric point of casein, maximum precipitation occurs. Relatively little commercial casein is produced in the United States, but imports amounted to well over 150 million lb in 1981 (USDA 1981C). Casein is widely used in food products as a protein supplement. Industrial uses include paper coatings, glues, plastics and artificial fibers. Casein is typed according to the process used to precipitate it from milk, such as hydrochloric acid casein, sulfuric acid casein, lactic acid casein, coprecipitated casein, rennet casein, and low-viscosity casein. Differences... 

Casein is the material that curdles when acid is added to skim milk. Most of us think of it as cottage cheese. It normally comprises about 3% of the weight of whole milk. Since the type of acid used for curdling has a noticeable effect on the quality and purity of casein, it is normally classified as lactic, hydrochloric, or sulfuric acid material. Lactic acid casein is the product of natural self-souring, although this is normally promoted by inoculating skim milk with lactobacillus. A small portion of casein is produced by the rennet process. This material is... 

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...

Coextrusion is the process of extruding two or more materials simultaneously or in tandem. It allows a combination of an ingredient such as wheat flour, which is inexpensive and easily enriched with vitamins and minerals, with dairy protein, which provides functionality and texture. For example, an early coextrusion of wheat flour and rennet casein was performed by van de Voort et al. (1984), who obtained products with varying characteristics depending on process parameters. 

Because of problems encountered in blending whey products containing residual M. miehei rennet with materials containing casein, this rennet preparation has been modified to decrease its heat stability (Branner-Jorgensen et al 1980 Cornelius 1982). This process involves treatment of the rennet with hydrogen peroxide under controlled conditions. Some enzymic activity is lost but the modified enzyme has about the same stability as calf rennet. Nearly all M. miehei rennet used by the cheese industry is now modified (Ramet and Weber 1981). 

Weal BC and Southward CR. Recent Developments in Casein Manufacture. I. The production of rennet casein by a continuous cook process. NZ J. Dairy Sci. Technol. 1974 9 2-5. 

Cryodestabilization of casein limits the commercial feasibility of frozen milk, which may be attractive in certain circumstances. However, cryode-stabilized casein might be commercially viable, especially if applied to milks concentrated by ultrafiltration, which are less stable than normal milk. Cryodestabilized casein may be processed in the usual way. The product is dispersible in water and can be reconstituted as micelles in water at 40°C, The heat stability and rennet coagulability of these micelles are generally similar to those of normal micelles and casein produced by cryodestabilization may be suitable for the production of fast-ripening cheeses, e.g. Mozzarella or Camembert, when the supply of fresh milk is inadequate. As far as we are aware, casein is not produced commercially by cryodestabilization. 

The rennet coagulation of milk is a two-stage process the primary phase involves the enzymatic production of para-casein and TCA-soluble peptides [(glyco) macropeptides] while the secondary phase involves the aggregation or gelation of para-casein Ca at temperatures >20°C the two stages overlap somewhat. The subject has been reviewed by Fox (1984) and Dal-gleish (1992, 1993). 

Casein, which is a type of protein included in milk, is used as a thickening agent for adhesives. There are three types of casein add casein, lactic casein, and rennet casein, depending on the production process. Acid casein is used for latex adhesives as thickening agents. Since casein is basically insoluble in water, alkaU water solutions (e.g., with ammonia, potassium hydrate, sodium hydrate, borax, etc.) are used after water immersion to swell. Quality check of casein is conducted to measure the viscosity of water solution of 1—2%. 

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