Acid-soluble wheat proteins from

Figure 5. Elution of acid-soluble wheat proteins from hydrophobic gel Phenyl-Sepharose-4B by different solvents. NaDodSO = SDS flSJ.

Alkali-extracted proteins from simflower oil cake (89% proteins, Nx6.25) and wheat gluten (76.5% proteins, Nx5.7) were reacted with n-octanol in the presence of an acid catalyst. Temperature, reaction time and catalyst concentration were varied according to an experimental design to maximize the esterification yield. The latter was determined by alkaline hydrolysis and subsequent analysis by gas chromatography. The hydrolysis of the peptide chain was traced by the determination of the amount of free amino groups in esterified proteins using 2,4,6-trinitrobenzene-sulfonic acid (TNBS) assays. The solubility curves of modified proteins in water as a function of pH were obtained by Kjeldahl analysis to determine the composition of the soluble and insoluble parts. 

Glutelins a group of simple proteins from grain. Hiey are generally insoluble in water, salt solutions and dilute ethanol, but at extreme pH values they do become soluble. Ihey contain up to 45% glutamic acid. The best known are glutenin in wheat, orycenin in rice and hordenin in barley. 

Piergiovanni AR 2007. Extraction and separation of water-soluble proteins from different wheat species by acidic capillary electrophoresis. J Agric Food Chem 55 3850-3856. 

Hops or hops-derived products are usually boiled for 0.5 to 2.5 hours with wort. Wort is an aqueous solution of fermentable sugars (glucose, maltose, maltotriose) obtained by enzymatic hydrolysis of starch derived from malt extraction or from other sources (wheat, maize, rice). The hop boiling takes place in copper or stainless steel tanks and aims to precipitate wort proteins, to sterilize the wort, to remove volatile off-odours by steam distillation and most importantly, to transform the alpha acids into beer-soluble and bitter iso-alpha acids. 

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