Proteins Chemistry, Characterization, and Quality》.pdf.pdf

Proteins: Chemistry, Characterization, and QualityS Sforza and T Tedeschi, University of Parma, Parma, ItalyPA Wierenga, Wageningen University, Wageningen, herlands?2016 Elsevier Ltd. All rights in FoodsProteins are one of the pound classes in raw agri-cultural materials (., milk, eggs, soy, and cereals) as well asin meat and fish products. The proteins present in raw productsserve different purposes, related to the structure and propertiesof the proteins. The first distinguishing feature of proteins istheir solubility. This was used in the classical separation ofwheat proteins by Osborne. The milled wheat can be sequen-tially extracted by water, 5% NaCl, and 70% ethanol to yieldthe albumin, globulin, and prolamin fractions. The remainingalcohol-insoluble fraction contains the glutelins, -bined with the prolamin fraction are referred to as gluten. Formilk whey, obtained after the removal of the caseins (either bychymosin or by precipitation at ), a similar separation ofproteins is obtained by increasing the concentration of ammo-nium sulfate. The globulins precipitate in 50%, and the albu-mins in 100% (NH4)2SO4. Proteins that are insoluble inaqueous solutions often have the function to provide structure(., myosin in muscle tissue). Soluble proteins such as foundin milk are often used for metabolic purposes (., enzymes,transport proteins, and