Wheat proteins extensibility

While any type of flour can be made in a wholemeal form some products probably can not be made from wholemeal flour. The problems are that although all the wheat protein is present the quality of the protein is lower towards the outside of the wheat berry. This effect would render the making of products requiring very high extensibility, e.g. filo pastry, very difficult. The other problem is that the bran particles tend to burst gas bubbles, reducing the amount of lift. Despite the above, wholemeal bread flour is common and wholemeal self raising flour can be made. 

A wheat protein derivative with molecular weight of 250-500 kDa has been studied in aqueous solution and in an 0/W emulsion for its effects on the viscoelastic properties of the skin. A slight increase in skin extensibility and elasticity was found and related to its moisturizing and film-forming effects. This derivative is proposed in skin care preparation for transient skin Arming-tightening effects (54). 

The thermal properties of wheat proteins have been extensively studied. DSC of wheat protein at low water content shows multiple endotherms. These have been identified as... 

Wafer Flour. Wafer flour is a type of biscuit flour with the same basic specification of low protein soft wheat flour with a low starch damage. Once again the required dough property is extensibility. The only differences are that if the protein is too low the wafer will be too soft to handle, and if the protein is too high the wafer will be too hard. The other important property is a resistance to gluten separation. Wafer flours are likely to be brown. 

VPGVP, which tends to form a type II P turn with proline in position 2 (Fig. 2-24) is present in long tandem repeats e.g., (VPGVG). These extensible regions alternate with short a helices which are crosslinked to other chains. Similar structures are present in silks (Box 2-B) and in proteins of wheat gluten. ... 

Two books by C. H. Bailey have become standard references. The first (59) covers wheat as a raw product and is concerned with varieties and environment in respect to composition, the milling process and its effects on the milled products, and the characteristics of flour. The second (60) is primarily a biochemical study concerned with the proteins, starches, sugars, gums, lipids, minerals, and vitamins of the wheat kernel. Both are extensively documented. 

Endo and co-workers at Ehime University, Matsuyama, Japan, have led the development of the most promising eukaryotic cell-free system to date, based on wheat embryos. A significant advance made by this group was the development of pEU expression vectors that have overcome many of the difficulties associated with mRNA synthesis for translation in a eukaryotic system [8]. In addition to extensive optimization of reaction conditions that have seen improvements in protein synthesis rates, Endo and colleagues have improved wheat extract embryo preparation protocols to enhance the stability of these systems to a remarkable extent [9]. When coupled with the dialysis mode of reaction, Endo et al. were able to maintain translational activity in a coupled transcription/ translation wheat embryo reaction for 150 hours, producing 5 mg of enzymatically active protein per mb reaction mixture [10]. This again represents a serious alternative to in vivo methods of large-scale protein production. 

Reviews on methods for nonenzymatic phosphorylation of food proteins are available, covering the literature up to 1991 [60-62]. Of the chemical reagents surveyed, phosphorus oxychloride (POCl3) and sodium trimetaphosphate (STMP) have been investigated extensively. However, only POCI3 appears to be suitable and ready for large-scale application. Food proteins frequently phosphorylated include soy protein, wheat gluten, and yeast protein. 

FIG. 31. Biaxial extensional viscosity and shear viscosity vs extension and shear for wheat flour dough with 16.0% protein content (Huang and Kokini, 1993). tjb is biaxial extensional viscosity, ij is shear viscosity. 6 ij superimposed with tjb indicate that the biaxial extensional viscosity are about five times larger than shear viscosity at the equivalent shear rate. 

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