Use optimization of natural antioxidants in refined, bleached, and deodorized palm olein during repeated deep-fat frying using response surface methodology

An optimization study on the use of oleoresin rosemary extract, sage extrac t, and citric acid added into refined, bleached, and deodorized (RBD) palm olein in deep-fat frying of potato chips was carried out using response sur face methodology (RSM). Results showed that oleoresin rosemary extract was the most important factor affecting the sensory acceptability of potato chi ps. For taste and odor, its effects were highly significant (P < 0.01), whi le for crispiness and overall acceptability, the effects were significant ( P < 0.05). As for sage extract, the level of this antioxidant had a highly significant (P < 0.01) effect on appearance and taste and a significant eff ect (P < 0.05) on odor and overall acceptability, but had no effect on cris piness. Although there was no significant synergistic correlation between c itric acid and oleoresin rosemary extract or sage extract at the first orde r, its second order was significantly (P < 0.05) related to taste, crispine ss, and overall accept ability. An interaction between oleoresin rosemary a nd sage extracts also significantly (P < 0.05) improved the scare of overal l acceptability of the potato chips. Contour maps of the sensory scores of potato chips indicated that the optimal points for appearance were achieved using 0.062% oleoresin rosemary extract, 0.066% sage extract, and 0.023% c itric acid, while optimal task was achieved with 0.063% oleoresin rosemary extract, 0.075% sage extract, and 0.025% citric acid. With the same sequenc e of ingredients added into oil, the combinations required to achieve the o ptimal odor, crispiness, and overall acceptability scores were 0.058-0.046- 0.026, 0.060-0.071-0.022, and 0.060-0.064-0.026%, respectively.