Whey solubility

WHEY. Whey is the watery part of milk separated from the curd. Whey is available as dried whey, condensed whey, dried whey solubles, condensed whey solubles, dried hydrolyzed whey, condensed hydrolyzed whey, condensed whey product, dried whey product, and condensed cultured whey. 

The ratio of a-lactose [10039-26-6] and P-lactose in dry milk and whey varies according to the speed and temperature of drying. An aqueous solution at equiHbrium at 25°C contains 35% a- and 63% -lactose. The latter is more soluble and sweeter than DL-lactose and is obtained by heating an 80% DL-lactose [63-42-3] solution above 93.5°C, foUowed by drying on a dmm or roUer dryer. Lactose is used for foods and pharmaceutical products. 

Tofu. Tofu is prepared by adding a coagulant such as calcium sulfate to soymilk to precipitate the protein and oil into a gelatinous curd. The curd is then separated from the soluble portion (whey), pressed, and washed to yield a market-ready product. Tofu, a traditional food in Japan (90), was populari2ed in the United States in the late 1970s and is available in many U.S. supermarkets. 

Whey concentration, both of whole whey and ultrafiltration permeate, is practiced successfully, but the solubility of lactose hmits the practical concentration of whey to about 20 percent total sohds, about a 4x concentration fac tor. (Membranes do not tolerate sohds forming on their surface.) Nanofiltration is used to soften water and clean up streams where complete removal of monovalent ions is either unnecessary or undesirable. Because of the ionic character of most NF membranes, they reject polyvalent ions much more readily than monovalent ions. NF is used to treat salt whey, the whey expressed after NaCl is added to curd. Nanofiltration permits the NaCl to permeate while retaining the other whey components, which may then be blended with ordinaiy whey. NF is also used to deacidify whey produced by the addition of HCl to milk in the production of casein. 

Also, pilot plant and laboratory scale anaerobic studies have demonstrated successful treatment of wastewaters of 5,000 to 50,000 mg/L GOD from corn chips containing soluble and colloidal corn starch and protein, cheese whey, organic chemicals, food, bakeiy, breweiy, paper mill foul condensate, paint, and numerous other hazardous anci non-hazardous materials. 

The largest industrial use of ultrafiltration is the recovery of paint from water-soluble coat bases (primers) applied by the wet electrodeposition process (electrocoating) in auto and appliance factories. Many installations of this type are operating around the world. The recovery of proteins in cheese whey (a waste from cheese processing) for dairy applications is the second largest application, where a... 

Sodium carboxymethylcellulose (commonly known as CMC) was introduced in 1945 by Josephson and Dahle 10) for use in ice cream. It is cold water-soluble, will not react with acid, and has excellent water-binding properties. When properly processed, it is easily dispersible and quickly soluble in the mix. These properties make it well suited for high temperature-short time (HTST) mix. When used alone, it has a tendency to cause separation or wheying off in the mix. Irish moss extract is used with CMC to eliminate this condition. From 0.15 to 0.25% CMC is most often used in ice cream mix. 

Milk from cows contains 3.2% protein, about 80% of which is casein. Casein is isolated by a precipitation process from milk, involving heating, rinsing to remove whey, and drying to a powder. The yield is about 3 kg/ 100 kg skim milk. Rennet casein is obtained when the casein is precipitated by chymosin enzyme, also known as rennet, and acid casein is produced when precipitation is accomplished by acidification. Acid casein is usually found in the form of sodium caseinate or calcium caseinate, which are water-soluble salts. Caseinates are made by reacting NaOH or CaOH with a slurry of casein curd or powder and then spray drying (Southward, 2010). 

Denaturation and aggregation of whey proteins are affected by the pH of extrusion. When extruding WPI, alkaline conditions increase denaturation and solubility, decrease pasting properties, and produce more pronounced microstructural changes (Onwulata et ah, 2006). Denaturation in the extruder causes whey proteins to form small primary aggregates that combine to form large clusters. The clusters are then aligned by shear to form fibrous structures. 

FIGURE 5.6 Solubility of texturized dairy protein products extruded at different temperatures, 25 (control), 50, 75, and 100 C Nonfat dried milk (NDM) whey protein concentrate (WPC80), containing 80% protein and whey protein isolate (WPl), containing 95% protein (Onwulata et at, 2003a). 

Lactose, the milk sugar, is a reducing disaccharide consisting of glucose and galactose moieties. The estimated annual worldwide availability of lactose as a byproduct from cheese manufacture is several million tons [1,2], but only about 400 000 t/a lactose is processed further from cheese whey [3], Non-processed whey is an environmental problem due to its high biochemical and chemical oxygen demand [2], The use of lactose as such is limited by two main factors relatively low solubility of lactose in most solvents and lactose intolerance in human body [1]. 

New technology has been applied to allow more whey to be used. The technology has been applied to convert the lactose into a mixture of dextrose and galactose. These two monosaccharides are both reducing sugars and the mixture is much more soluble than lactose. 

One of the bars to the use of lactose as a food ingredient is its limited solubility. This can be overcome by enzymatically splitting the lactose to its component monosaccharides dextrose and galactose. These monosaccharides are much more soluble than lactose but can still undergo the Maillard reaction. If the lactose is split into its constituent monosaccharides, whey can be condensed to a relatively stable high solids syrup. These syrups tend to carry some cheese flavour notes but, where used appropriately, can contribute beneficial colours and flavours in biscuits. 

Chemical reactions Polymerization of casein and whey proteins are due to some kind of chemical reactions. The different proteins as found in the supernatant of milk after precipitation at pH 4.6 are collectively called whey proteins. These globular proteins are more water soluble than caseins and are subject to heat dena-turation. Denaturation increases their water-binding capacity. The principal fractions are P-lactoglobulin, a-lactalbumin, bovine serum albumin (BSA), and immunoglobulins (Ig). 

NFDM, which retains casein micelles similar to those in fresh milk, is produced by pasteurization of sklmmllk, vacuum concentration and spray drying under processing conditions that result in either "low heat" or "high heat" product. Low heat NFDM is required for most applications that depend upon a highly soluble protein, as the case for most emulsification applications, since it is manufactured under mild temperature conditions to minimize whey protein denaturation and complexation with casein micelles. 

Partly delactosed whey is produced by concentrating cheese whey or casein whey sufficiently to exceed the solubility limit of lactose, followed by cooling, seeding with lactose crystals and removal of the crystalline lactose. The resulting liquor fraction is recovered and dryed. 

Whey protein concentrates (WPC) are produced by a variety of processing treatments to remove both lactose and minerals (20) as indicated in Figure 5. Even though it would be highly desireable to remove most of the lactose and minerals in these processes, it is not practical from an economic standpoint and thus most of these products only range in protein content from 35 to 50 %.The major objective of most of these processes is to produce a WPC with minimal protein denaturation in order to obtain a product with maximum protein solubility and functionality. However, from a practical consideration this objective is not readily obtainable, and thus most WPC products commercially available exhibit variable whey protein denaturation and functionality (20). 

Initially, it was believed that milk contained only one type of protein but about 100 years ago it was shown that the proteins in milk could be fractionated into two well-defined groups. On acidification to pH 4.6 (the isoelectric pH) at around 30°C, about 80% of the total protein in bovine milk precipitates out of solution this fraction is now called casein. The protein which remains soluble under these conditions is referred to as whey or serum protein or non-casein nitrogen. The pioneering work in this area was done by the German scientist, Hammarsten, and consequently isoelectric (acid) casein is sometimes referred to as casein nach Hammarsten. 

Casein can be precipitated from solution by any of several salts. Addition of (NH4)2S04 to milk to a concentration of 260 g 1 1 causes complete precipitation of the casein together with some whey proteins (immunoglobulins, Ig). MgS04 may also be used. Saturation of milk with NaCl at 37°C precipitates the casein and Igs while the major whey proteins remain soluble, provided they are undenatured. This characteristic is the basis of a commercial test used for the heat classification of milk powders which contain variable levels of denatured whey proteins. 

The caseins may be precipitated from milk by c. 40% ethanol while the whey proteins remain soluble lower concentrations of ethanol may be used at lower pH values. 

The whey prepared by any of the above methods, except 4, contains lactose and soluble salts. Total whey proteins may be prepared from the... 

It was recognized 60 years ago that whey prepared by any of the above methods contained two well-defined groups of proteins which could be fractionated by saturated MgS04 or half saturated (NH4)2S04 the precipitate (roughly 20% of total N) was referred to as lactoglobulin and the soluble protein as lactalbumin. 

The whey proteins, which represent about 20% of the proteins of bovine milk, are typical globular proteins with high levels of secondary and tertiary structures, and are, therefore, susceptible to denaturation by various agents, including heat. The denaturation kinetics of whey proteins, as measured by loss of solubility in saturated NaCl at pH 4.6, are summarized in Figure... 

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