Powdered milk water content

The certified reference material (CRM 450), used for the validation of the method, is real contaminated powdered milk with a certified content in PCB-52, PCB-101, PCB-118, PCB-156, and PCB-180. This material contains approximately 3.9% water and 25% fat. It is used after reconstituting and was supplied by the EC Community Bureau of Reference (BCR). 

Riickold et al., 2000). This leads to greater or smaller discrepancies between the "official" results for moisture and the water content, depending essentially on the lactose content of the product. For the typical spray-dried milk such as full cream or skimmed milk powder these discrepancies are normally small as the lactose is in most cases amorphous. 

The water mass fraction of the milk powder was determined on 18 samples regularly taken during the filling procedure and was measured by Karl-Fischer titration the water content was found to be (2.1 0.2)% (mass fraction). 

FIGURE 8.3 Water vapor pressure or water sorption isotherms of foods. Given are water content versus water activity (aw). (a) skim milk (powder), (b) Various foods meat (1), apple (2), boiled sweet (3), skim milk (4), and peanuts (5). (c) Caseinate systems (water content expressed asg perg dry protein) pure caseinate (1), curd or renneted milk (2), and cheese (3). 

It was mentioned above that the crystallization of lactose can occur at a critical water content, just above the glass transition. It was further (implicitly) assumed that this would happen at the same mass fraction of water i/fw in skim milk powder. Experiments show that this is not precisely correct but that the critical conditions for crystallization are at the same water activity. Does this imply that the glass transition is determined by aw rather than i//w ... 

Electrostatic interactions in air are very different compared to the electrostatic interactions in aqueous systems, as there is no ion solubility and no double layer is formed. The source of the surface charges is also different. In air, there are no possibilities for acid-base interactions or for ion disassociation. Charging in air is caused by static electricity and is stable for non-conducting particles. This makes the interaction coulombic in nature, with a range comparable to the radius of the particle. The electrostatic interactions easily dominate when the particle size is large, the density is low, and there is a low water content (low conductivity). Typical examples could be during the drying of milk powder or the transport of coffee powder. 

Dairy products, such as mUk powder, should be prepared exclusively from milk and should not contain solids from whey. The absence of rennet whey solids from mUk powder is required according to legislation. Considering the lower price of rennet whey, it can be an attractive adulterant of milk powder. Thus, the presence of CMP can be a good marker to evaluate milk powder authenticity. Whey powders contain about 12% protein and 75% lactose. Caseinomacropeptide can account for more than 16% of the protein content. RP-HPLC can be used to detect rennet whey in mUk powder by CMP measurement. For this purpose, powdered milks were reconstituted with deionized water. Skim milks were prepared by separating the fat from the whole milk by centrifugation at 700 X g (at 4°C) for 10 min. Caseinomacropeptide and... 

Incredibly, in the summer of 2008, approximately 300 000 Chinese babies became sick and at least six died of kidney failure. Chinese companies had diluted milk with water and added melamine to make the protein content appear normal. Two people were executed in 2009 for their role in producing tainted milk. In 2010, Chinese authorities found 40 tons of powdered milk containing melamine. 

DeVilder and Bossuyt (12) determined water content in industrial skim milk and whole milk powders obtained by low, medium, and high thermal treatment of milk before spray drying. They also used two different technological processes for drying. They concluded that the accuracy of the method, even if very reliable, could be improved by calibrating for each factory or, preferably, for each production line. They determined... 

At the same time, Baer et al. (1) determined water content, protein, and fat in commercial skim milk powders and in the laboratory prepared from nonfat dry milk (NFDM) samples. They used 44 commercial low-, medium-, and high-heat samples and 38 laboratory prepared samples, to increase the composition range. Data indicated that prediction of moisture content by NIR was linear throughout the tested range (2.85-9.70%). They reported that usable predictions of composition could be obtained even when physical factors such as particle size were not constant. They also concluded that NIR calibrations at individual dairy plants probably result in lower SEP values because of the greater physical homogeneity of samples. 

The importance of sorption isotherms is generally in the evaluation of the water content in food at which the adverse effects on the food quahty can be minimised. This is usually the moment when other layers are formed around the monomolecular layer of water (vicinal water), which is the instant when the multilayer water arises. Most adverse events in storage of foods with medium and low water content, such as crystallisation of amorphous sugars (e.g. lactose in powdered or condensed milk), agglomeration of powder materials, stickiness or re-crystallisation of water and formation of large crystals in frozen products (e.g. in ice cream) relates to water content, its activity and storage temperature, and are therefore... 

Oral powder- The oral powder may be mixed with a small amount of water, milk, formula, soy formula, soy milk, or dietary supplement once mixed, the entire contents must be consumed in order to obtain the full dose. Acidic food or juice (eg, orange juice, apple juice, or apple sauce) are not recommended because of bitter taste. Do not reconstitute with water in its original container. Once mixed, store the oral powder for no more than 6 hours. May be refrigerated for up to 6 hours. 

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