Wheat proteins solubility-based

Biscuits were prepared from plant-protein flours based on 20Z replacement for wheat flour. In biscuits prepared with fractions isolated from cottonseed flours, the quantities used were calculated using the percentages these fractions represented of the original flour, e.g., the salt solution soluble fraction of LCP flour was 43X of the original flour and 8.6Z, (20 x 0.43) replacement for wheat was used to prepare the biscuit. 

Proteins are natural, renewable, and biodegradable polymers which have attracted considerable attention in recent years in terms of advances in genetic engineering, eco-friendly materials, and novel composite materials based on renewable sources. This chapter reviews the protein structures, their physicochemical properties, their modification and their application, with particular emphasis on soy protein, zein, wheat protein, and casein. Firstly, it presents an overview of the structure, classification, hydration-dehydration, solubility, denaturation, and new concepts on proteins. Secondly, it concentrates on the physical and chemical properties of the four important kinds of proteins. Thirdly, the potential applications of proteins, including films and sheets, adhesives, plastics, blends, and composites, etc. are discussed. 

Dried Gluten. This material is sold as vital wheat gluten, it is produced by a scaled up version of the process for producing wet gluten for flour testing. A flour and water dough is made and then washed to remove the starch, the soluble proteins and the pentosan-based gum fraction. This latter fraction is an example of a non-starch carbohydrate. 

Glutelins. Soluble in very dilute acid or base and insoluble in neutral solvents. These proteins occur in cereals, such as glutenin in wheat and oryzenin in rice. 

Natural polymers such as starch and protein are potential alternatives to petroleum-based polymers for a number of applications. Unfortunately, their high solubility in water limit their use for water sensitive applications. To solve this problem thermoplastic starches have been laminated using water-resistant, biodegradable polymers. For example, polylactic acid and P(3HB-co-3HV) were utilised as the outer layers of the stratified polyester/PWS (plasticized wheat starch)/polyester film strucmre in order to improve the mechanical properties and water resistance of PWS which made it useful for food packaging and disposable articles [65]. Moreover, improved physic-chemical interactions between P(3HB-CO-3HV) and wheat straw fibres were achieved with high temperature treatment. It resulted in increased P(3HB-co-3HV) crystallization, increased Young s moduli and lowered values of stress and strain to break than the neat matrix of P(3HB-co-3HV). There was no difference in the biodegradation rate of the polymer [66]. 

The macroscopic properties of the protein-based, 3D macromolecular networks partially depend on system stabilising interactions. The water solubility of protein materials depends on the nature and density of intermolecular interactions. Materials are soluble in water when the energy of the interprotein bonds is lower than the energy of the interactions that could be established between water and polar groups not involved in the network. The presence of physical nodes (i.e., chain entanglements), covalent intermolecular bonds and/or a high interaction density is sufficient to produce films that are completely or partially insoluble in water [77]. For example, the presence of intermolecular covalent bonds in wheat gluten- or keratin-based materials makes them insoluble. 

Proteins are the second largest group of compounds in endosperm (12-15%). Cereal proteins are classified based on their solubility characteristics water soluble albumins (5-10%), dilute salt-solution soluble globuhns (5-10%), aqueous alcohol soluble prolamins (40-50%) and dilute acid or alkah soluble glutelins (30-40%) (Godon, 1994). Cereal proteins, similar to other plant proteins, are low in some of the essential amino acids, for example lysine. Glutamic acid is the major amino acid in wheat. 

---