Composition of saliva

Saliva is a complex fluid produced by a number of specialized glands which discharge into the oral cavity. It is composed of water 99% and solid 1% which include a complex mixture of inorganic and organic substances.

Organic substance such as L-amylase (ptyalin), lingual lipase, kallikrein, lysozymes, small amounts of urea, uric acid, cholesterol, and mucin. While inorganic substances are Na, Cl, K and HCO3.

It is estimated that over 200 different proteins and peptides are contained in human saliva.

The two major proteins present in saliva are alpha-amylase and mucin. Salivary –amylase (ptyalin) is produced predominantly by the parotid glands, and mucin is produced mainly by the sublingual and submandibular salivary gland.

Many substances in blood serum are found in saliva. The salivary concentration of some of these is proportional to the serum concentration.

The major characteristics of saliva are:
*Its large volume relative to the mass of the salivary glands
*Its high potassium concentration
*Its low osmolarity
*The specialized organic materials it contains

Salivary secretion is stimulated by smell and taste. The regulatory centers are in pons in brain.
Composition of saliva

What is ash content?

What is ash content?
When either organic compounds are decomposed or released at high temperature (500C -600C), the remaining residue is the ash.

This residue consists of oxides and salts containing anions such as phosphates, chlorides, sulfates, and other halides and cations such as sodium, potassium, calcium, magnesium, iron, and manganese.

During the ashing process organic salts decompose, losing the carbon-containing moiety. The metal from such salts forms and oxide or reacts with other anions of the matrix. Some metals (e.g., cadmium and lead) may be volatized during ashing; therefore, if the ash is to be examined for trace elements, care should be exercised to prevent losses during ashing.

For most foods, ashing at 485C or less for 12hrwill give acceptable results for trace elements analysis. Losses of minerals due to carbon release can be appreciable from carbon-containing samples.

This mechanical loss of cash can be avoided by starting the incineration in the muffle furnace at a low temperature (room temperature) and allowing the temperature to rise slowly.

Air currents may be a problem if the door of the furnace is opened suddenly. Generally, samples should not be placed ion areas of the furnace closer than 1 in. from the rear wall and 1.5 in form the front.
What is ash content?