Foods : their origin, composition and manufacture / by William Tibbles.

  • Tibbles, William, 1859-1928.
Date:
1912
Catalogue details

Licence: In copyright

Credit: Foods : their origin, composition and manufacture / by William Tibbles. Source: Wellcome Collection.

Provider: This material has been provided by The University of Leeds Library. The original may be consulted at The University of Leeds Library.

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    Uracil, C4H4N2O2 ( = 2, 6-di-oxy-pyrrimidine) : It is derived from thymo-nucleic acid, and from the nucleic acids of spleen, pancreas, yeast, and herring testicles. It forms rosettes of needle-shaped crystals ; readily soluble in hot water, not very soluble in cold water, and almost insoluble in alcohol and ether. Thymin, CgHgNaOa (5-methyl-uracil) : This results from the splitting of thymo-nucleic acid, and crystallizes in steUar form or dendric leaves. Cystosin, C4HgN30 ( = 6-amino-di-oxy-pyrrimidine): It is the result of splitting up the nucleic acids of the spleen, pancreas, yeast, etc. It crystallizes in thin leaves which look like mother-of-pearl, and dissolves in water with difficulty. 8. The Derivatives of Protein—These consist of metaproteins, proteoses, peptones, and polypeptides. These are usually regarded as the products of protein digestion or hydrolysis only ; but seeing that they frequently occur among the constituents of vegetables, it would be impossible to say that some of them are not in course of being transformed into proteins of a higher grade. Metaproteins are the most complex; they consist of acid- albumin and alkali-albumin, and were formerly called albumin- ates. But the latter is considered to be an objectionable term, because metaproteins are obtained from both albumins and globulms, and the suffix ate implies a salt. They are insoluble in pure water and neutral solutions containing no salt; they are soluble m acid or alkaline solutions or weak salines. They are not coagulated by heat; but, like globulins, they are precipitated by neutral salts—e.g., sodium chloride and magnesium or ammonium sulphate m excess ia) Acid-albumin, or syntonin, is precipitated from its solution by neutralization even in the presence of alkaline phosphates. (&) Alkah- albumin is also precipitated by neutralization. Alkali-albumin contains less sulphur than acid-albumin.^ A very msoluble alkali- albumin (Lieberkuhn's jelly) is formed by adding strong potash to the white of egg. Legumin, or vegetable casem, is simply alkali- albumin formed from native globulins by reagents of the analyst. Conglutin is the legumin from almonds and lupins. . , , Proteoses are less complex than metaproteins ; they include albumoses, globuloses, gelatose, vitellose, casemose, myosmose etc., according to their origin. In plants they are called phyto- albumoses-..g., in gluten. They are most y Fotems which have undergone some chemical change, usually as the result of enzymic action, as in the process o digestion. They give he biuret reaction-^..., rose-red colour with KHO and CuSO^ They are not coagulated by heat, but most of them are precipitated by saturation ^ith sulphate of ammonia and other neutral salts, also by tannic acid and nitric acid. They are classified as— [a] Proio-proieose or albumose : Soluble in pm-e water, piecipi- tated from solution by MgSO^, CaSO,, and (NH4)2S04- -Ph^ albumose in wheat flour and papaw juice is a proto-albumose. 1 Halliburton's Chemical Physiology, p. 128. ^btd.
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