3.5.2. Free fatty acid content
Free fatty acids (FFA) content is considered to be an indicator of oil quality in food industry as it leads to development of off-flavor in oils and fried products. FFA was found to increase with an increase in frying cycles in case of heating as well as frying. The percentage of FFA of fresh RBO was 0.15. FFA was found to increase after heating and frying for 1–6 consecutive cycles, from 0.3 to 0.44% and 0.48% respectively. The change in FFA after frying was found to be more in comparison to only heating (Fig. 3a). The moisture coming from the fried product accelerates the hydrolysis of oil. It is known that water can promote the hydrolysis of triacylglycerols to form a combination of mono and diacylglycerols, glycerol and free fatty acids. The increase in FFA was due to the cleavage and oxidation of double bonds to form carbonyl compounds, which oxidized to low molecular weight fatty acid during frying (Irwandi and Cheman, 2000 and Ramadan et al., 2006). The increase in FFA level is not a very reliable parameter for the degradation of frying oil, because it is difficult to differentiate between the FFA formed by oxidation or by hydrolysis (Ramadan et al., 2006). Moreover, low molecular weight FFA may be lost through volatilization during frying (Sulieman et al., 2006).