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Benefits of casein additives in historic mortar mixes
Published in Jan Kubica, Arkadiusz Kwiecień, Łukasz Bednarz, Brick and Block Masonry - From Historical to Sustainable Masonry, 2020
K. Falkjar, J. Erochko, M. Santana, D. Lacroix
Casein is a protein naturally occurring in bovine milk; it is divided into three protein subgroups: α-casein, β-casein and κ-casein. Further subgroups of α-casein exist (Atamer, et al., 2017). Bovine casein typically contains 48% α-casein, 34% β-casein and 15% κ-casein (Atamer, et al., 2017). The chemical structure, comprising of a series of amino acids, is the same except for the number of phosphate groups present (Bian & Plank, 2013). Casein is typically extracted from milk by means of acid precipitation: casein precipitates at a pH less than 4.6 (Bian & Plank, 2013), is partially insoluble near a neutral pH—κ-casein is soluble while the other types of casein are insoluble (Zittle & Custer, 1963)—and dissolves completely at a pH greater than 10.0 (Post, Arnold, Weiss, & Hinrichs, 2012). Lime mortar, for which the main constituent is calcium hydroxide, has a pH of 12.6, equivalent to that of a saturated calcium hydroxide solution, therefore, casein dissolves in the mortar and has been shown to increase the workability of the mortar and to improve adhesive properties (Asselin-Boulanger, 2018). In particular, the anionic phosphate component causes the protein to absorb calcium existent in masonry mortar, and thus behave as a superplasticiser additive (Zittle & Custer, 1963). It has been used to increase the workability of mortars since medieval times in many parts of Europe (Ince, 2012) (ASTM International, 2018). It was also used in glues and adhesives in the 19th century (ASTM International, 2013), and is still used to the present day as an additive in certain paints.
Physical networks of biopolymers
Published in K. Dušek, S.I. Kuchanov, Polymer Networks '91, 1992
Casein (milk) gels are important technologically because they form the basis of cheese, yoghurt and other similar products. The term casein, itself, describes a number of different proteins (αs1,αs2,B and κ-caseins), which occur in milk as roughly spherical but highly voluminous micelles, typical DP ≈10000, particularly stabilized by colloidal calcium phosphate. Treating whole milk with an enzyme chymosin (rennet) is believed to cleave away the κ-casein which exists on the “outside” of the micelle, producing a coagulate (curd), which is separated from the remaining liquor (whey), a solution of whey proteins. Many detailed studies of casein aggregation have been carried out, although most often using the methods of classical colloid science (Ref.26).
Enzyme Catalysis
Published in Harvey W. Blanch, Douglas S. Clark, Biochemical Engineering, 1997
Harvey W. Blanch, Douglas S. Clark
Enzymes are produced from microbial, plant and animal sources. In the case of animal enzymes, the organ is obtained from a slaughterhouse and the enzyme is recovered by extraction. Calf rennet, used in cheese manufacture, is recovered from the fourth stomach of the calf and is comprised of chymosin (88-94%) and pepsin (6-12%). It acts on the K-casein fraction of casein micelles in milk, releasing a soluble peptide and leaving an insoluble fraction, p-\k-casein, which destabilizes the micelle and causes milk to clot. Papain is a plant protease prepared by water extraction of crude Carica papaya. Ficin is similarly obtained from Ficus carica. These enzymes are then filtered, solvent precipitated and dried.
Production and characterization of infant milk formula powders: A review
Published in Drying Technology, 2021
A. K. M. Masum, Jayani Chandrapala, Thom Huppertz, Benu Adhikari, Bogdan Zisu
Caseins are more heat stable compared to whey proteins. For instance, sodium caseinate can withstand severe heating (140 °C, > 60 mins) without any remarkable changes.[45] However, casein interacts with whey proteins during heating. A mixture containing β-Lg and k-casein forms aggregates during heating through disulfide and/or hydrophobic interactions.[46] Heating facilitates the formation of complexes between whey proteins and casein micelles or k-caseins by increasing interaction.[47] Heating using steam injection and use of high solids wet-mixes can decrease the thermal denaturation of whey proteins and increase the colloidal stability of IMF formulations.[40,41]
Evaluation of the milk clotting properties of an aspartic peptidase secreted by Rhizopus microsporus
Published in Preparative Biochemistry & Biotechnology, 2020
Ronivaldo Rodrigues da Silva, Tatiane Beltramini Souto, Nathalia Gonsales da Rosa, Lilian Caroline Gonçalves de Oliveira, Maria Aparecida Juliano, Luiz Juliano, Jose C. Rosa, Hamilton Cabral
At the forefront of the drive to meet demand and reduce production costs for cheese-making is the search for new milk coagulants.[5,6] Highly efficient, specific enzymes are required for this step in order to cleave the Phe105-Met106 peptide bond in k-casein, and low proteolysis in other portions of casein.[7] An example of such an enzyme is calf chymosin (E.C. 3.4.23.4), which has been used for cheese making since prehistoric times.[8] However, calf chymosin is not widely available,[1] and its use is becoming problematic due to numerous ethical and religious objections. Additionally, a ban has been placed on recombinant calf rennet in some countries such as France and Germany.[9]