Whey sterilization

Large quantities of evaporated milk are used to manufacture ice cream, bakery products, and confectionery products (see Bakery processes and LEAVENING agents). When used for manufacturing other foods, evaporated milk is not sterilized, but placed in bulk containers, refrigerated, and used fresh. This product is caHed condensed milk. Skimmed milk may be used as a feedstock to produce evaporated skimmed milk. The moisture content of other Hquid milk products can be reduced by evaporation to produce condensed whey, condensed buttermilk, and concentrated sour milk. 

Membrane-retained components are collectively called concentrate or retentate. Materials permeating the membrane are called filtrate, ultrafiltrate, or permeate. It is the objective of ultrafiltration to recover or concentrate particular species in the retentate (eg, latex concentration, pigment recovery, protein recovery from cheese and casein wheys, and concentration of proteins for biopharmaceuticals) or to produce a purified permeate (eg, sewage treatment, production of sterile water or antibiotics, etc). Diafiltration is a specific ultrafiltration process in which the retentate is further purified or the permeable sohds are extracted further by the addition of water or, in the case of proteins, buffer to the retentate. 

A process for ultra-high temperature sterilization of whey has been proposed. The purpose of the process is to destroy 99.99% of the spores in... 

Hydrogen peroxide is used as a sterilant or preservative for milk and whey it destroys harmful micro-organisms. Any excess hydrogen peroxide left in the milk or whey after treatment can be decomposed to water and oxygen using an enzyme (catalase). 

Casein is low in sulphur (0.8%) while the whey proteins are relatively rich (1.7%). Differences in sulphur content become more apparent if one considers the levels of individual sulphur-containing amino acids. The sulphur of casein is present mainly in methionine, with low concentrations of cysteine and cystine in fact the principal caseins contain only methionine. The whey proteins contain significant amounts of both cysteine and cystine in addition to methionine and these amino acids are responsible, in part, for many of the changes which occur in milk on heating, e.g. cooked flavour, increased rennet coagulation time (due to interaction between /Mactoglobulin and K-casein) and improved heat stability of milk pre-heated prior to sterilization. 

It is necessary to forewarm milk to impart adequate heat stability to the concentrate to permit it to withstand subsequent sterilization treatments. The heat-induced casein micelle-whey protein complexes in forewarmed milk are less sensitive to heat than native whey proteins and thus provide the required stability to the concentrate. The forewarming treatment also stabilizes the milk mineral system by com-plexing Ca and Mg ions with casein micelles and by converting ionic forms to the less reactive form of colloidal phosphate (Morr 1975). 

Preparation and sterilization of medium Typical medium consists of corn steep liquor (4 percent to 5 percent dry weight) an additional nitrogen source such as soy meal, yeast extract, whey a carbon source such as lactose and various buffers. 

The formation of beads is a two-step process based on the cold gelation of whey proteins in the presence of divalent cations, such as Ca2+ [67], Briefly, the whey protein isolate (WPI) solution (10% w/v in deionized water) was (i) adjusted at pH 7 to favor the apparition of negative charges implied in ionic bounds with Ca2+ ions and (ii) heated (80 °C, 45 min) to denaturate the proteins. Recombinant cells in the beginning of their stationnary growth phase were suspended in a sterile solution of... 

Microfiltration processing for clarification and defatting of cheese whey, for selective separation and concentration of micellar caseins from milk for various purposes, for fractionation of caseins and their peptides, for recovery of native whey proteins from milk, for gentle sterilization of milk to produce extended shelf fife liquid milk and cheese milk, for fractionation of globular milk fat and its components, for the reduction of microorganisms in cheese brine, and for the removal of colloidal particles in membrane cleaning solutions. 

A major emphasis in the utilization of MF in the dairy industry that is of relevance to cheesemaking is changing the casein to whey protein ratio or the casein to fat ratio in mUk fractions [91]. MF of whole or skim mUk produces a retentate that is rich in native micellar casein, which improves the cheesemaking process, and a crystal clear and sterile permeate with composition close to that of sweet whey but with greater amount of native whey proteins that is suitable for direct manufacmre of whey protein isolate [8,52,92-95]. In processing skim mUk using MF membranes of 0.2 p,m pore size or smaller, the permeation of... 

Blue cheese flavors have been prepared via submerged culture fermentations in a sterile milk-based medium using Penicillium rogueforti(63). The fermentations are conducted under pressure with low aeration rates with optimal flavor production occurring from 24-72 hours. Similarly, Kosikowski and Jolly(64) prepared blue cheese flavors from the fermentation of mixtures of whey, food fat, salt and water by P roqueforti. Dwivedi and Kinsella(65) developed a continuous submerged fermentation of P. roqueforti for production of blue cheese flavor. 

Continuous fermentation processes can also be carried out in a hollow fiber fermentor (HFF).85 Cells are packed into the shell side of a hollow fiber module, while substrate solution is fed to the core of the fibers (Figure 7.41). Since the cell slurry is separated from the substrate solution by the membrane, HFFscan be used for fermentation of liquid streams containing low molecular weight fermentable substances. A careful choice of membrane molecular weight cut-off can also assure that the cell environment is fully sterilized. Figure 7.45 shows typical performance of an HFF for whey permeate fermentation to ethanol by... 

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