Effect of the Roselle (Hibiscus sabdariffa) extract on oxidation stability of bulk frying oil during open and deep frying: a response surface approach

Synthetic antioxidant such as BHA (butylated-hydroxyanisole), BHT (butylated-hydroxytoluene) and TBHQ (tertiary-butyl-hydroquinone) are usually added into frying oil to prolong its shelf life and reusability. However, its utilization has become more obsolete. Roselle (Hibiscus sabdariffa L.) is a tropical plant which has been reported to possess antioxidant, anti-tumor and antihyperlipemic activities that was suspected to be contributed by its phenolic anthocyanins compound. This study was aimed to study the effect of the addition of roselle extract as a natural antioxidant in bulk frying oil (BFO). Central composite design of Response Surface Methodology was employed to measure the trend of roselle extract utilization in open frying and deep frying practice. The results showed that the addition of roselle extract could retard the formation of free fatty acids (FFA) to maximum 0.1226 mg KOH/g oil (4% addition) and lowered hydroperoxide formation as low as 7.47 MeqO2/kg oil after treated with 20 times of successive frying. The trend study showed that the addition of 0.04% of roselle extract could prolong the usage of oil up to 6 times in the open frying treatment. On the other hand, only 0.01% of the roselle extract was needed to prolong the oil usage up to 20 times in deep frying practice. This result showed that the roselle extract can be used as a substitute for synthetic antioxidant to prolong the shelf life and reusability of BFO.