Analytical approaches for the assessment of free fatty acids in oils and fats
Free fatty acids (FFA) are produced by the hydrolysis of oils and fats. The level of FFA depends on time, temperature and moisture content because the oils and fats are exposed to various environments such as storage, processing, heating or frying. Since FFA are less stable than neutral oil, they are more prone to oxidation and to turning rancid. Thus, FFA is a key feature linked with the quality and commercial value of oils and fats. The American Oil Chemists' Society (AOCS), the Association of Official Analytical Chemists (AOAC) and the European Commission (EC) Regulations have established almost identical standard methods for the assessment of FFA. These methods are based on titration, where oils or fats need to be dissolved in hot neutralized ethanol or ethanol/diethyl ether using phenolphthalein as an end point indicator. Titrimetric procedures are, however, laborious and need large amounts of chemicals and solvents. The cost of chemicals and environmental issues further limit these procedures. In addition, accurate detection of end points, especially for highly colored crude oil using a colorimetric indicator, is a difficult task. Despite these disadvantages, the titration method is unfortunately still being used in most of the edible-oil industries for the determination of FFA. Because of a lack of any comprehensive review on this very important topic, we have made an attempt to present a review in order to discuss the various methods available with special emphasis on the instrumental methods because of their high sensitivity, accuracy and rapidity.