The Stability of biodiesel is an important characteristic that
affects the usage of biodiesel. It is the ability to resist the physical
and chemical changes caused by interaction with the environment. The factors promoting auto-oxidation of biodiesel are
(i) polyunsaturation (ii) the position of C–C double bond and (iii)
number of bis-allylic sites. Conjugate arrangement of double
bonds in carbon chain is more stable than the methylene interrupted structure. Out of the various structure indices which are
measure of the polyunsaturation, BAPE is most important. Unsaturation also has the strongest influence on the Induction period of
the blends of biodiesel. This study also discussed the various tests
available for measurement of stability of fatty acids, oils, food
products and biodiesel. Rancimat test is a unanimous choice for
measurement of oxidation stability and has been prescribed in
various American and Europeon standards. NIRS has gained
popularity in the past decade as the quickest and effective method
of stability measurement due to its advantages over Rancimat test.
Antioxidants are very effective in increasing the stability of biodiesel and reduction in NOx. PY and PG have been reported as the
best antioxidants in major studies. This study also point out that
Aluminum and Stainless steel are most suitable for containers of
biodiesel. There is further scope of study in the UAOM and thermogravimetric analysis methods of stability testing