Maize, ’’

FIGURE 1.3 Photograph of the modern maize cob (bottom) compared to its ancestor Teosintle (lying on top) (courtesy of Dr. Juan Manuel de la Fuente). 

Major Characteristics and Adaptation Range of Commercial Cereal Grains 

Maize is classed according to color (yellow or white) and caryopsis shape (dent or flint). The most popular class is yellow-dent. Maize is highly adaptable to different soils and environments. The optimum growth temperature is from 25°C-30°C. It requires a 500 mm rainfall during its cycle, which usually lasts 120 days. It is planted from sea level up to 2500 m altimde, and from 50° north latitude to 40° south latitude. The crop is highly susceptible to low temperatures or frosting 

Three major classes are recognized long, medium, and short. Rice is a tropical cereal generally planted on flooded lands called paddies, although it is also planted using intense irrigation. 

Rice is usually transplanted and requires high labor. The crop is highly susceptible to low temperatures and photoperiod. It is generally planted from sea level to 3000 m altitude 

This grain, botanically Zea mays, is the native grain plant of the Americas where it is known as corn. Sometimes it is referred to as Indian corn. 

Maize has some potential as a bread making ingredient and is so used in the places where it is grown. Presently, maize is not a viable grain crop in Europe owing to the climate. 

Imported maize is the raw material for several food ingredients used in the bakery industry. While maize can be dry milled like wheat, it is more commonly wet milled. The wet milling process is much better suited to separating the different components of maize so that the oil, the protein and the starch can be recovered separately. Maize starch is used directly in bakery products as corn flour, so-called even in the UK. 

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Amalean high amylose com starch American Maize... 

Similar materials are available based on potato starch, eg, PaseUi SA2 which claims DE below 3 and has unique properties based on its amylose—amylopectin ratio pecuhar to potato starch. The product contains only 0.1% proteia and 0.06% fat which helps stabilize dried food mixes compounded with it. Another carbohydrate raw material is waxy-maize starch. Maltodextrias of differeat DE values of 6, 10, and 15, usiag waxy-maize starch, are available (Staley Co.). This product, called Stellar, is offered ia several physical forms such as agglomerates and hoUow spheres, and is prepared by acid modification (49). Maltodextrias based oa com starch are offered with DEs of 5, 10, 15, and 18 as powders or agglomerates (Grain Processing Corp.). 

In industrial production of acid-modified starches, a 40% slurry of normal com starch or waxy maize starch is acidified with hydrochloric or sulfuric acid at 25—55°C. Reaction time is controlled by measuring loss of viscosity and may vary from 6 to 24 hs. For product reproducibiUty, it is necessary to strictly control the type of starch, its concentration, the type of acid and its concentration, the temperature, and time of reaction. Viscosity is plotted versus time, and when the desired amount of thinning is attained the mixture is neutralized with soda ash or dilute sodium hydroxide. The acid-modified starch is then filtered and dried. If the starch is washed with a nonaqueous solvent (89), gelling time is reduced, but such drying is seldom used. Acid treatment may be used in conjunction with preparation of starch ethers (90), cationic starches, or cross-linked starches. Acid treatment of 34 different rice starches has been reported (91), as well as acidic hydrolysis of wheat and com starches followed by hydroxypropylation for the purpose of preparing thin-hoiling and nongelling adhesives (92). 

Starch acetates [9045-28-7] are made by reaction of starch with acetic anhydride. Starch acetates are used in foods to provide paste clarity and viscosity stabiHty at low temperatures. A waxy maize starch acetate is most commonly used. Waxy maize starch acetates for food use are often cross-linked. Acetylated starches are also widely used in warp sizing of textiles. 

Atrazine and simazine arose principally as a result of their use in amenity situations but, since their ban for non-agriciiltiiral purposes, concentrations are generally declining. Fiowever, atrazine and simazine still have some agricultural uses (atrazine on maize and simazine on a wide range of crops), so the risk of pollution still exists when these pesticides are applied in either groundwater or surface water drinking water supply catchments. 

Of these materials zein, the maize protein, has been used for plastics on a small scale. It can be cross-linked by formaldehyde but curing times are very long. Complicated bleaching processes have led to the production of almost colourless samples in the laboratory but the process cannot readily be extended to large-scale operation. The cured product has a greater water resistance than casein. Proteins from soya bean, castor bean and blood have also been converted into plastic masses but each have the attendant dark colour. 

Dusts from barley, oats, rye, wheat or maize, or The baking or flour milling industry or on farms... 

VsUlago maydis. Alkaloids isolated from this maize fungus were named ustilaginine and ustilagotoxine and are stated to resemble ergotinine and ergo-toxine respectively. (Mas, Bol. Soc. Quim. Peru, 1938, 4, 3.)... 

Size exclusion was first noted in the late fifties when separations of proteins on columns packed with swollen maize starch were observed (Lindqvist and Storgards, 1955 Lathe and Ruthven, 1956). The run time was typically 48 hr. With the advent of a commercial material for size separation of molecules, a gel of cross-linked dextran, researchers were given a purposely made material for size exclusion, or gel filtration, of solutes as described in the classical work by Porath and Flodin (1959). The material, named Sephadex, was made available commercially by Pharmacia in 1959. This promoted a rapid development of the technique and it was soon applied to the separation of proteins and aqueous polymers. The work by Porath and Flodin promoted Moore (1964) to apply the technique to size separation, gel permeation chromatography of organic molecules on gels of lightly cross-linked polystyrene (i.e., Styragel). 

The noteworthy properties of amines ae their basicity and their rmcleophilicity. The basicity of amines has been discussed in Section 22.4. Several reactions in which amines act as nucleophiles have already been encountered in ealier chapters. These ae sum-maized in Table 22.4. 

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