CHEMICALS (usually organic based) MAY expire, how have explained, and what are the possible corrections to extend their validity, if it is possible?

Each chemical has a shelf life. Check MSDS supplied with the chemical. To avoid expiry of chemicals, order required quantity only. Excess chemicals stored may lead to expiry and issue of its disposal. 

which is the means for evaluating the water retention capacity in cooked meat products, and in the powders; in addition to what is the method to measure the extraction of proteins

in a powder

Each chemical comes with a material safety datasheet "MSDS" on which you'll find the perfect conditions to inhibit the degredation of this chemical under the storage conditions section.

e.g. keep away from light, keep in tight container, use in the presence of Nitrogen, keep in refrigerated place ...etc.

For the case of olive oil and oils by and large. The oxidation reaction is catalized by heat, light and presence of metals. So removing or reducing these three factors will certainly extend the validity of oil. Also, anti-oxidants are added to take the bullet of oxidation for the oil to be oxidized. The most famous anti-oxidants used in pharmaceutical products are Butylated Hydroxyanisole "BHA" & Butylated Hydroxytoluene "BHT" those are called Hinderd phenolics anti oxidants.

Aromatic Amine are also very effective anti-oxidants that are used to inhibit the oxidation of oils. Typically, the synergism between Hindered Phenolics & Aromatic Amines is employed in several cases.

Extending Validity of chemicals is by preserving it away from moisture, very high or very low degrees of tempreature, keeping it closed not to open for a long time, not to use tools that have been already used in other chemicals, away from light.....These all as I think.