Food : a brief account of its sources, constituents and uses / A. H. Church.

  • Church, A. H. (Arthur Herbert), 1834-1915.
Date:
1889
Catalogue details

Licence: Public Domain Mark

Credit: Food : a brief account of its sources, constituents and uses / A. H. Church. Source: Wellcome Collection.

    61/280 (page 47)
    the several flesh-formers and allied compounds included in the nitrogenous nutrients. It is probable that all the albuminoids have nearly the same nutrient value and serve the same offices in the animal economy. The rate at which they are digested, however, differs, animal albumen being the most readily acted upon and absorbed. When certain albuminoids, or small percentages thereof, escape digestion, it may arise from several causes, amongst which the inclusion of these substances within indigestible matter, as in coarse wheat bran, is not the least frequent; and, as many of the older analyses of food products greatly exaggerated the percentages of albumi- noids present, it is not to be wondered at that a considerable proportion of some of these substances seemed occasionally to escape digestion and absorption. It must, however, be admitted that legumin, and the other albuminoids of pulse, seem to be but partially utilised in the human economy, unless the daily diet contain but a moderate proportion of them. The albuminoids suffer no chemical change during mastication. But when they come in contact with the gastric juice in the stomach, their digestion commences. The juice contains two active ingredients, an acid or a mixture of acids, together with a neutral nitrogenous substance called pepsin. This pepsin is an unorganised digestive ferment; by its aid, if acid be present and the temperature be suitable (about 98°), albuminoids are all converted into the peptones, described on p. 44. These are all soluble in water, and are not removed from the solu- tion by acids, alkalies, or salts j they are all soluble, even in alcohol, if not very strong ; and they are diffusible. Animal casein before it becomes a peptone, is curdled '} legumin is rapidly changed and dissolved even by gastric juice deprived of its pepsin. Fibrin, whether animal or vegetable, as the gluten-fibrin of wheat grain, is rapidly broken up by the gastric juice, swelling up, and finally becoming a ropy, opaline liquid. Albumen, when soluble, is transformed into peptones without being previously curdled by