| 摘要 |
Zein is extracted from proteinaceous material derived from maize by means of an aqueous alcoholic solvent at a temperature not above 70 DEG C. and a hydrogen ion concentration such that the pH of the final extract is not less than 6. The solvent may contain up to 20 per cent or more, preferably 7-8 per cent, of water and may be pure aqueous ethyl or methyl alcohol or mixtures with other organic solvents. Extraction is preferably effected at 55-65 DEG C., the final pH being 6 to 7. Gluten meal may be extracted with 93 per cent alcohol. The pH value, which is normally too low and, moreover, falls as the extraction proceeds, is regulated by the addition of alkali such as sodium hydroxide at the beginning or from time to time during the extraction. The extract may be concentrated by vacuum distillation, for example to 30 per cent zein content. It is treated with a solvent for oil and colouring matter such as toluol, benzol, xylol, carbon tetrachloride or, less desirably, aliphatic hydrocarbons such as petroleum ether, and the solvent layer separated. The zein solution is mixed with water to precipitate the zein which is mixed with water until it loses its adhesive nature, rolled into sheets, soaked in water and dried. The dried sheets can then be ground for use in making plastics.
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