This section is from the book "Practical Dietetics With Special Reference To Diet In Disease", by William Gilman Thompson. Also available from Amazon: Practical Dietetics with Special Reference to Diet in Disease.
The various albuminous foods are digested best, each with a different degree of acidity, and it is probable that throughout a meal the intensity of reaction of the gastric juice varies considerably, becoming stronger as more food is absorbed or more juice is formed, or weaker as more of it passes with the chyme into the pylorus or as it is more diluted with additional food or drink. In this manner the different proteids are all certain of a fair opportunity for timely digestion.
The products of albuminoid digestion in the stomach have been carefully analysed by Kühne and Chittenden, and are found to succeed each other in the following order: 1. Albuminoids or proteids.
2. Syntonin or acid albumin.
3. Albumoses or proteoses - proto-albumose, hetero-albumose, deutero-albumose. The three latter form -
Raw meat in the stomach turns grey-brown and swells. It takes longer to digest meat raw than when cooked, for the fibres are penetrated less easily by the gastric juice. An exception to this occurs when the raw meat is first scraped or made into a pulp. In the digestion of meats Frerichs found that the connective tissue is first broken down by the gastric juice, then the sarcolemma, and finally the substance between the striae of the muscle fibres.
Vegetable albumin is digested in the stomach in a manner quite similar to the digestion of animal proteids.
Gluten and vegetable casein are also dissolved by the gastric juice when strongly acid.
Gelatin is one of the substances most easily dissolved in and absorbed from the stomach. It is altered by the hydrochloric acid of the gastric juice, so that it can no longer be solidified by cold. It is finally converted into diffusible substances somewhat resembling peptones, but not identical with them.