Milk, curdling

Chymotrypein is a proteolytic and milk-curdling enzyme of the pancreatic secretion. It is a protein endopeptidase which catalyses the hydrolysis of native proteins to peptones, polypeptides and amino acids, by breaking the peptide linkages of the carboxyl groups of tyrosine and phenylalanine. 

Ohmiya, K., Fukami, K., Shimizu, S., and Gekko, K. 1987. Milk curdling by rennet under high pressure. Journal of Food Science 52 84-87. 

Not to be confused with rennin, the milk-curdling enzyme found in the stomach of ruminant animals. 

Sample preparation Condition a Bond Elut C8 SPE cartridge with 5 mL MeOH and 5 mL water. 20 mL Milk -I- 20 mL buffer, heat at 60° for 20 min or imtil milk curdles, centrifuge for 10 min, add the supernatant to the SPE cartridge, wash with two 2.5 mL portions of water, elute with 2.5 mL MeOH. Evaporate the eluate to diyness under a stream of nitrogen, extract the residue with three 100 pL portions of 50 mM pH 6.0 potassium phosphate buffer, filter (0.2 pm), inject an aliquot of the filtrate. (Buffer was 545 mL 100 mM citric acid, 455 mL 200 mM Na2HP04, and 74.4 g EDTA, adjust to pH... 

Explain how (a) a soap such as sodium stearate stabilizes a colloidal dispersion of oil droplets in vrater (b) milk curdles upon addition of an add. 

Milk normally has a pH of 6.0-6.3. If bacteria grow in it they release acids such as lactic acid which lower the pH and render the milk sour. When the isoelectronic point for casein is reached at about pH 4.7, this phosphoprotein is precipitated and the milk curdles, enabling it to be separated into the traditional curds and whey. The latter corresponds roughly to milk serum (Figure 12.8). 

Vinegar, lemon juice, and curdled milk, all taste sour. What other properties would you expect them to have in common ... 

Why does orange juice cause milk to curdle ... 

The word curdling comes from curd, the coagulated solid formed by adding acid or rennet to milk. Curds are the precursors of most cheeses. 

Tiny organisms in milk produce lactic acid, that turns the milk sour and causes it to curdle. This spoils the milk, but it is a vital factor in the yogurt and cheese industry. Milk can be made sour artificially by adding a few drops of lemon juice or some other mild acid. 

Arsenikon and sandarach mean to Dioscorides, as to Theophrastus, respectively orpiment and realgar. The former, yellow scales or plates, is used in medicine as a depilatory and a caustic. Heated alone, or with charcoal, it loses color and leaves a mass which cooled and powdered is a deadly poison (arsenious oxide). Curdled milk is said to be an antidote. Sandarach, red like cinnabar (dragon s blood, he means), behaves when heated like arsenikon, and in general has properties similar to that substance. He notes that it gives a sulphureous odor when roasted. 

TIE A PIECE OF CHEESE CLOTH OVER A JAR. POUR THE CURDLED MILK INTO THE CHEESE CLOTH. LET LIQUID (WHEY MIXED WITH VINEGAR] RUN OUT. KEEP THE LIQUID. 

Psychrotrophic Bacillus cereus can cause spoilage of pasteurized milk that is free of the more rapidly growing gram-negative psychrotrophs. Proteolytic B. cereus produces a defect of pasteurized milk known as sweet curdling (Overcast and Atmaran 1974). The action of B. cereus proteases on milk proteins has been described by Choud-hery and Mikolajcik (1971). 

Overcast, W. W. and Atmaran, K. 1974. The role of Bacillus cereus in sweet curdling of fluid milk. J. Milk Food Technol. 37, 233-236. 

Rennet Also known as rennin and chymosin. Enzyme that is used for curdling milk and making cheese. 

In many cases, denaturation is irreversible. When cooked egg white is cooled, it does not become uncooked. Curdled milk does not uncurdle when it is neutralized. Denaturation may be reversible, however, if the protein has undergone only mild denaturing conditions. For example, a protein can be salted out of solution by a high salt concentration, which denatures and precipitates the protein. When the precipitated protein is redissolved in a solution with a lower salt concentration, it usually regains its activity together with its natural conformation. 

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... 

It is interesting to know that the plant yellow bedstraw Galium verum) has been used formerly in Britain to curdle milk although it never became a useful rennet substitute. 

It is believed that cheese making was discovered by accident when someone tried to store milk in a bag made out of an animal s stomach and as a result, the enzymes in the stomach curdled the milk. It must have been a very brave or very hungry person who tasted that first cheese, but since then, as a species, we have acquired a liking for the stuff, to the tune of about thirty pounds of cheese per person per year in the United States alone. Cheese, a metastable mixture of oil, water, fats, calcium com-... 

CAS 9001-98-3. A digestive enzyme secreted by the glands of the stomach and causes curdling of milk. It has the power of coagulating 25,000 times its own weight of milk. 

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