Seeds of cereals

Prolamines. Proteins insoluble in water, but dissolving in aqueous alcohol solutions. Found in the seeds of cereals. 

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. 

Furthermore, Lisbonne has foimd that the pancreatic juice, as well as saliva, possesses the power of rapidly coagulating solutions of soluble starch at 130°, a property which Fernbach and olff noted in 1904 in the macerations of seeds of cereal, and which they attributed to a special enzyme, amylo-coagulase. 

Phytic acid,myo-inositol-l,2,3,4,5,6-hexakisdihydrogenphosphate, is the main storage form of phosphorus used during germination of seeds of cereals, pulses and oilseeds. Phytic add in seeds occurs primarily as a mixed calcium and magnesium salt, which is called phytin. Insoluble salts and ones that are utilised only slightly are also produced with other di- and trivalent ions, such as Fe and Zn in particular. The issue of phytin is discussed in detail in Chapter 6 (see Section 6.3.4.2.1). 

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. 

Endosperm A nutritive tissue found in seeds of cereal grains. It represents a part of the gametophyte tissue, since it develops from the mbryonic sac as a result of the fertilization of the two polar nuclei and pollen. The endosperm is triploid, and the genetic information is two-thirds female and one-third male. 

The case of canola is extraordinary because of the very high level accumulations (50-fold) of leaf-type carotenoids in seeds when the gene was introduced under the seed-specific promoter, napin. The exalbuminous seeds of canola differ from those of genetically engineered rice cereal grains in that they have chloroplasts, which may explain the capacity for hyperaccumulation of carotenoids. 

The germination stimulant or stimulants from host plants have not yet been identified, but research on isolation and identification of these allelopathic compounds continues. Other nonhost plants, such as cotton, also release chemicals which stimulate the germination of witchweed seed and these crops can replace the cereal crops in witchweed-infected fields. If no acceptable host is present, the witchweed plant is unable to mature and produce seed. The importance of cereal crops as a staple food in underdeveloped countries makes growth of nonhost crops only partially acceptable, and there are numerous wild hosts that allow the witchweed to germinate, mature, and produce more seed (several thousand seeds can be produced by a single plant). Nevertheless, application of either natural or synthetic stimulants in the absence of a host plant is an effective way of reducing and eventually eliminating the witchweed problem. 

In the quest to find other plants that are suitable as bioreactors, various monocoty-ledonous and dicotyledonous species have been tested. These include corn [16], rice and wheat [17], alfalfa [18], potato [19, 20], oilseed rape [21], pea [22], tomato [23] and soybean [24]. The major advantage of cereal crops is that recombinant proteins can be directed to accumulate in seeds, which are evolutionar specialized for storage and thus protect proteins from proteolytic degradation. Recombinant proteins are reported to remain stable in seeds for up to five months at room temperature [17] and for at least three years at refrigerator temperature without significant loss of activity [25]. In addition, the seed proteome is less complex than the leaf proteome, which makes purification quicker and more economical [26]. 

Compositional differences in the pea seeds influence the quality of the end products. Pea flours have been used for protein enrichment of a number of cereal-based products however, undesirable sensory characteristics may limit their use, in spite of improved functional effects in food systems. The production of volatile compounds during cooking and baking of foods with pea supplementation affects their acceptability. Enzyme systems active in unheated pea flours may contribute to their functional properties, but adversely affect the sensory quality of the food. 

We found that the seeds of several other plants (e.g. of Raphanus sp. or of Amaranthus caudatus) are much more sensitive against inhibitors from oat caryopses than oats itself. This means that germination of such seeds is effectively inhibited if they are in the immediate neighborhood of oat caryopses even if germination of oats itself can take place. Oats are more active in allelopathy than other cereals (2). 

Muller, K.J., Kunz, P., Spiess, H., Heyden, B., Irion, E. and Karutz, C. 2000. An overnational cereal circuit for developing locally adapted organic seeds of wheat. In Alfbldi, T., Lockeretz, W. and Niggli, U. (eds) Proceedings of the 13th International IFOAM Scientific Conference. Hochschulverlag ETH, Zurich, p. 224. 

Phosphoric acid is the characteristic ingredient of the seeds of plants. It forms about one-half of the ash of the groin of the different cereals, when burnt with their husks, but is seldom present in any considerable quantity in their ripe straws. 

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