Prolamins, zein

Zein occurs as a very light yellow to tan colored, granular or fine powder. It comprises the prolamine protein component of corn (Zea mays Linne ). It is produced commercially by extraction from corn gluten with alkaline aqueous isopropyl... 

Gliadins are prolamins, a group of plant storage proteins with a high proline content, found in the seeds of cereal grains wheat (gliadin), barley (hordein), rye (secalin), corn (zein) and, as a minor protein, avenin in oats. 

Prolamins are insoluble in water but soluble in 70-80% aqueous alcohol. Upon hydrolysis they yield much proline and amide nitrogen. They are deficient in lysine. Example - Gliadin of wheat and Zein of com. 

Zein is a prolamin with a molecular weight of approximately 38 000. 

Zein is a prolamin obtained from com (Zea mays Linne (Fam. Gramineae)). It occurs as a granular, straw- to pale yellow-colored amorphous powder or fine flakes and has a characteristic odor and bland taste. 

Prolamins. A group of simple proteins. Yield only amino acids upon cleavage by enzymes or acids. Examples gliadin, hordein, zein from grains. 

Zeins, the major storage proteins of maize belonging to the prolamins. In maize, the ethanol-soluble or protamine fraction consists of the zeins (Mr 10-22 kDa) that constitutes as much as half of the total protein of the endosperm. They are characterized by a high content of Glu (23%) and Leu (19%). The amino acid sequence of a representative of the zeins has been derived from the nucleotide sequence of a zein cDNA clone [D. Geraghty et al.. Nucleic Acids Res. 1981, 9, 5163]. 

Amide-rich polypeptides have been prepared by Krull et a/. (1965) for the purpose of employing model systems for studies of the contribution of side-chain amides to protein properties. Such glutamine-containing polypeptides may be regarded as models for prolamine proteins such as gliadin and zein, and also for glutelin proteins. 

Ethibloc (Ethnor Laboratories/Ethicon Inc., Norderstedt, Germany) is not available in the US. This biodegradable solution is a mixture of zein (a water-insoluble prolamine derived from corn gluten), alcohol, poppy seed, propylene glycol oil... 

One of the questions posed in Chapter 1 was "Why does dough from cereals other than wheat not have viscoelastic properties " It is well established that the gluten proteins of wheat are responsible for the viscoelastic properties of wheat flom dough (see Chapter 6). The requirements for a protein (or any polymer) to exhibit viscoelasticity are discussed in Chapter 14. One of these is that the protein should be above its glass transition temperature (Tg). Zein, the prolamin protein of maize, is found to contribute viscoelastic properties to a zein-starch dough when the temperature is raised above its Tg at that water content (Bushuk and MacRitchie 1989 Lawton 1992). This shows that it is possible to obtain viscoelastic properties with nonwheat cereal proteins. 

Zein is a protein (prolamine) extracted from maize seeds. It is used predominantly for the coating of confectionary and pharmaceutical tablets (50). 

Prolamines a group of simple (unconjugated) proteins, soluble in 90% ethanol. They occur in cereals, and contain up to 15 % proline and 30-45 % glutamic add, but they have only low contents of essential amino acids. The chief representatives are gliadin (wheat and rye), zein (maize contains no tryptophan or lysine) and hordein (barley contains no lysine). Oats and rice do not contain P. 

RP-HPLC is especially valuable in genetic studies of maize. Paulis et al. [175] showed that prolamin RP-HPLC differentiates normal, opaque-2, and modified opaque-2 genotypes differing in nutritional quality and endosperm texture. Modified opaque-2 maize genotypes ( quality protein maize ) are enriched in high-proline alcohol-soluble glutelin subunits and contain less zein than normal maize. 

Paulis and Bietz [187] used preparative RP-HPLC to fractionate zein. Fraction homogeneity, MW, and charge were examined by electrophoresis amino acid compositions related results of different techniques. Similarly, preparative RP-HPLC and lE-HPLC have fractionated oat prolamins for subsequent characterization [188-189]. 

Not all these groups of protein are necessarily found in any one species of seed (Table 2.2). The Gramineae contain prolamins (e.g. gliadin, zein and... 

Prolamins Gliadin Secalin Avenin Hordein Zein Oryzin Cafirin... 

Alanine Alanine occurs in almost all proteins in amounts of 2-12% (average content is 9.0%). Maize prolamine protein zein and animal protein gelatine contain about 9% of alanine. 

Fabra, M.J., Lopez-Rubio, A. and Lagaron, J.M. (2013b). High barrier polyhydroxy-alcanoate food packaging film by means of nanostructured electrospun interlayers of zein prolamine. Food Hydrocolloids, 32(1), 106-114. 

Fernandez, A.,Torres-Giner, S. and Lagaron, J.M. (2009). Novel route to stabilization of bioactive antioxidants by encapsulation in electrospun fibers of zein prolamine. Food Hydrocolloid, 23,1427-1432. 

Torres-Giner, S., Gimenez, E. and Lagaron. J.M. (2008). Characterization of the morphology and thermal properties of Zein Prolamine nanostructures obtained by electrospinning. Food Hydrocolloids, 22,601-614. 

Torres-Giner,S.,Martmez-Abad, A.,Ocio,M.J. and Lagaron, J.M. (2010). Stabilization of a nutraceutical omega-3 fatty add by encapsulation in ultrathin electro-sprayed zein prolamine. Journal of Food Science, 75, N69-N79. 

Gliadins or Prolamins.— These are peculiar to plants, and occur largely in the seeds of cereals. They are insoluble in water and in 90 per cent, alcohol, but have the special property of being soluble in 70-80 per cent, aqueous alcohol. They are not coagulated by heat. Important prolamins are hordein, from barley zein, from maize and gliadin, from wheat and rye. 

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