Che Man, Yaakob

Irwandi, Jaswir

Jamilah, B.

Liu, Jia Long

Mohd Ghazali, Hasanah

Selamat, Jinap

Tan, Chin Ping

Yusoff, M. S. A.

Universiti Putra Malaysia Institutional Repository

UPM Research Report 1998: Volume 2EFFECTS OF NATURAL AND SYNTHETICANTIOXIDANTS ON CHANGES IN RBD PALMOLEIN DURING DEEP-FAT FRYINGY.B Cbe Man, C.P. Tan, J.lrwandi, J.L. Liu, S. Jinap,H.M. Gbazali, B. Jamilah and M.S.A. YusofFaculty of Food Science and BiotechnologyUniversiti Putra Malaysia, 43400 UPM, Serdang, Selangor,MalaysiaKeywords: deep fat frying, antioxidants, oxidation,quality parameters, RBD palm olein.IntroductionDeep fat frying is one of the most commonly used proce-dures for preparation and manufacture of foods throughoutthe world. Lipid oxidation is one of the major deteriorativereactions in frying oils and fried foods, and often results in asignificant loss of quality. Antioxidants are added to fats andoils and foods containing fats to inhibit the development ofoff-flavours arising from the oxidation of unsaturated fattyacids. However, the commercial use of synthetic antioxidantsis strictly controlled and increasing consumer awareness offood additives and safety has prompted increased interest inthe use of natural antioxidants as alternatives to syntheticcompounds. Extract of many plants have been reported tohave varying degrees of antioxidant activities in fats and oils,with rosemary (Rosemarinus officinalis L.) and sage (Salviaofficinalis L.) being the most potent (Zhang et al. 1990).Therefore, the objective of this study was to assess the fryingperformance of RBD palm olein treated with natural antioxi-dants, oleoresin rosemary and sage extract, in comparisonwith synthetic antioxidants, butylated hydroxyanisole (BHA)and butylated hydroxytoluene (BHT).Materials and MethodsThe effect of antioxidants on the changes in quality charac-teristics ofRBD palm olein during deep fat frying (at 180°C)of potato chips for 3.S h/day for 7 consecutive days in fivesystems were compared in this study. The systems were RBDpalm olein without antioxidant (control), with 200 ppm bu-tylated hydroxytoluene (BHT). 200 ppm butylated hy-droxyanisole (BHA). 200 ppm oleoresin rosemary and 200ppm sage extract. The oil (4.S kg) was put into a Valentinebatch fryer and was stirred for 10 minutes to ensure dissolu-tion of antioxidant. In the case of system I (control), the oilalso was held for 10 minutes at 60°C, although no antioxi-dant was added. The temperature was then raised to 180°C in20 minutes. Frying started 20 minutes after the temperaturehad reached 180°C. A batch of 100 g raw potato chips wasfried for 2.S minutes at every 17.Sminutes interval. Fried oilsamples were analyzed for peroxide value (PV), thiobarbitu-ric acid (TBA) value, iodine value (IV), free fatty acids(FFA) content, polymer content, viscosity, EI%lcmat 232 and268 nm, color, fatty acid composition and CI8:2/CI6:0 ratio.Results and DiscussionThe oil system in the absence of antioxidants (System I) ex-perienced a greater degree of deterioration than oil systemswith the presence of antioxidants (Systems II, III, IV and V).The PV rose and fell during frying which is the same patternobserved for peroxides in most deep fat frying studies. Sincehigh heat (180 ± SoC)was used on these systems, peroxidesformed during oxidation may have decomposed to secondaryoxidation products (15). RBD palm olein with the addition of208antioxidants (Systems II, III, IV and V) had PVs that weresignificantly (P<O.OS) lower than those of the controlthroughout the duration of the study. Judging from the PVs,the oxidative stability was decreased in the order oleoresinrosemary '" BHA > sage extract « BHT > control. TBA val-ues of all systems increased progressively with the fryingtime. The control (System I) consistently had the highestTBA values among the five systems throughout the 7 con-secutive days of frying. The other treatments in order of thelevel (highest) of TBA value were BHT '" sage extract >BHA > oleoresin rosemary. The changes in iodine value over7 days of frying were 15.15, 13.73, 14.08, 13.04 and l3.13 gof 121 100 g oil for Systems I, II, III, IV and V, respectively.The changes in iodine value showed that both oleoresinrosemary and sage extract were comparatively more effectivein protecting oxidation of unsaturated fatty acid that BHAand BHT. At the end of frying period, FFA contents were0.81, 0.80, 0.77, 0.76 and 0.79 % for Systems I, II, III, IVand V, respectively. The FFA content increases were highestfor the oil system without antioxidants (System I). The in-crement of FFA content in oil systems with antioxidants wasin the order: oleoresin rosemary '" BHA < sage extract <BHT. Polymer content of all systems increased slowly overthe first 5 days of frying followed by a marked increase overthe last 2 days of frying. The oleoresin rosemary had thestrongest effect in retarding formation of polymers duringfrying, followed by sage extract, two synthetic antioxidants(BHA and BHT) and control. The significant (P<O.OS)changes in viscosity over 7 days of frying were 37.S0, 34.59,32.50, 31.S0 and 33.91 centipoise for Systems I, II, III, IVand V, respectively. The effects of each system in controllingviscosity increases were considered in order as follows: oleo-resin rosemary> BHA > sage extract> BHT > control. Thered and yellow colour of oil systems increased significantly(P<O.OS)throughout the 7 consecutive days of frying. Theresult~ s~owed that System IV (200 ppm oleoresin rosemary)was significantly (p<0.05) darkened at a less rapid rate thanfour other systems. The changes in EI%Icmat 232 and 268 nmof a given substance can be used as a relative measurementof oxidation. The stabilising effect of antioxidants on RBDpalm olein was in the order: oleoresin rosemary> sage ex-tract » BHA > BHT. The decreases in C18: 2 across 7 con-secutive days of frying were 7.07, 3.S7, 4.23,3.63 and 4.03%for S~ste~s I, II, III, IV and V, respectively. The overall rateof .0Xldationof C18: 2 was reduced in the presence of anti-~x~dants. However, oleoresin rosemary showed greater ac-tivity than three other antioxidants throughout 7 consecutivedays of frying.ConclusionsTh.ea~dition ~f.antioxidants to RBD palm olein improves itsoXIda~Ivestab.Ihtywhen used as a deep fat frying oil. Gener-ally, m the Oil, oleoresin rosemary was superior to controlan~ t~ee oth~r antioxidants. The order of activity found forantIoxId~ts m RBD palm olein during deep fat frying ofpotato chips was oleoresin rosemary> BHA > sage extract>BHT: although some variation from this order was found de-pending on the method of assessment.ReferencesZhang,. K.~., Bao, Y.D., Wu, P., Rosen, R.T. and Ho, C.T. 1990.Antioxidative Components of Tanshen (Salvia miltiorrhiza~~;.f.)'Journal a/the Agriculture and Food Chemistry. 38: 1194-Supported by IRPA Grant 03-02-04-0003

Effects of natural and synthetic antioxidants on changes in RBD palm olein during deep-fat frying

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Effects of natural and synthetic antioxidants on changes in RBD palm olein during deep-fat frying

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