palm oil: the solution to over-used oil in south africa...

Palm Oil: The Solution to Over-Used Oil in South Africa

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Palm Oil: The Solution toOver-Used Oil in SouthAfrica

Johari Minal*; Kock, J L F**; Razali Ismail*;Pohl, C H**; Botes, P J** and Abdullah Ariffin*

INTRODUCTION

In South Africa, more than 100 000 t used frying oils are sold ascooking oils to the poor communities annually. While there is nothingwrong with the use of used oils/fats within the regulated specifications,they are, unfortunately, highly oxidized, unstable and, worse, maycontain as high as 75% polymers. In animal studies, highly oxidizedand degraded substances caused adverse biological effects includinggrowth retardation, diarrhoea, cellular damage, etc. and even death(Kock et al., 2002). Highly oxidized fats also contain toxic compoundssuch as liposoluble contaminants like PAHs, PCBs and dioxins (Haw,2003). Consequently, South Africa has strict regulations prohibiting theuse of over-used oils in food preparation. By legislation, fryingestablishments are prohibited to use oil containing polymerizedtriglyceride (PTG) breakdown levels (also known as polymers) of 16%and above or total polar compounds (TPC) of 25% and above (Anon,1996). Oils containing less than 16% polymers are regarded as safeand can also be distributed for further use in food preparations (Kocket al., 2002). During an international symposium on deep fat frying inHagen, March 2000, several European Union (EU) countries acceptedvarying levels of PTG (10%-16%) and TPC (24%-27%) as the discardpoints for frying oil (Anon, 2000).

* Malaysian Palm Oil Board,P. O. Box 10620,50720 Kuala Lumpur,Malaysia.E-mail: [email protected]

**Department of MicrobialBiochemical and Food Biotechnology,Faculty of Natural and Agricultural Sciences,University of the Free State,P. O. Box 339,Bloemfontein 9300,South Africa.

Realizing the potential hazardsof using abused oils/fats, theSouth African Frying Oil Initiative(SAFOI) was formed in 1994 toeducate and guide bothconsumers/buyers towards tested/stable cooking/frying oils throughawareness campaigns, training offryer operators/health officials,

seminars, publications and intro-duction of the Seal of Approval,a certification that endorses thequality and stability of frying/cooking oils. In addition toenforcing the regulatory limits bythe Department of Health, SAFOIpromotes the use of more stableoils for frying so that less usedoils above the regulatory limitsare re-used for human consump-tion (Kock et al., 1996). Palmolein was noted as a more stablefrying oil than the soft oils from7000 used oil samples drawnfrom frying establishments acrossSouth Africa since 1997 byEnvironmental Health Officials:not a single palm oil productover-used in frying has been

detected. This was because palmoil is stable against oxidation athigh temperatures. Kock et al.(2003) calculated the inherentstability (IS) of oils and fats(Table 1) and found that palmolein had the lowest IS value,which means it was the moststable oil of all those calculated.This stability is attributed by itspredominant oleic and palmiticacids which are both stableagainst oxidation. The contents ofsusceptible fatty acids againstoxidation, i.e., linoleic andlinolenic acids are only about12% and 0.2%, respectively. Highcontents of natural antioxidants,i.e., vitamin E (tocopherols andtocotrienols), in palm oil/oleinprovide extra protection againstoxygen attack. Crude palm oilcontains 600-1000 ppm vitamin E(Siew, 2005) and refined palm oil,palm olein and palm stearinretain, respectively 69%, 72%and 76% of the original levels incrude palm oil (Sundram, 2005).

The stability of palm oil hasbeen well established throughresearch done worldwide. Manystudies have concluded that palmoil or palm olein is comparable tohydrogenated oils in terms offrying performance, if not better(Zeddelmann and Wurziger, 1973;Toregard and Eriksson, 1979).Palm oil/olein not only has ahigher oxidative stability index(OSI) than the soft oils (Razali,2005) but it also extends theshelf-life of fried foods (Masashiet al., 1985; Augustin et al.,

Palm Oil Developments 43

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TABLE 1. CALCULATED INHERENT STABILITY OF SELECTED OILS AND FATS

Soyabean 7.0Canola 5.5Cottonseed 5.4Olive 1.5Palm olein 1.3Sunflower 6.8

Note: Lower value, higher inherent stability.Source: Kock et al. (2003).

1988), increases productivity(Johari et al., 2003) and does notproduce a soapy taste nor form asticky gum inside the fryer (Razaliet al., 2001). Due to its excellentfrying properties, palm oil/olein isused in industrial deep frying ofinstant noodles and snack foods,flash frying of potato sticks anddeep fat frying in restaurants andfast food chains. However, therehas been no study to determinethe stability of palm oil inextensive batch frying, as is thecase in restaurant operation.

Since restaurants and the foodservice industry are the majorusers of frying oils, a study onextensive frying was conductedby the Lipid Technology Group,University of the Free State,South Africa, to determine thefrying life (to regulatory limits) ofpalm and sunflower oils. Thestudy also tried to find a meansto reduce the over-use of oils/fats.

SPUR FRYING TRIAL

This trial was performed atGolden Cloud Spur Restaurant,Bloemfontein, South Africa. Twofrying oil brands each of palm oil(SupaCrisp) and sunflower oil(Sunseed) were used for fryingover two months. Palm oil wasused in the first month andsunflower oil the next. Therestaurant had three fryers, oneeach for potato chips, onion andcalamari rings. The frying condi-tions practised by the restaurantwere as follow:

Fryer capacity: 20 litresFrying temperature: 180˚C

Frying period:One month, 15 hr day-1

(0900-2400 hr)At the start of the frying trial,

all the three fryers were filledwith fresh oil (Figure 1). Asample of 50 ml oil was takenfrom each fryer everyday at0800 hr. The calamari fryer wasthen topped up with the used oilfrom the onion fryer and the oilfrom the chip fryer used to topup the onion fryer. Fresh oil wasused to top up the chip fryer.Sometimes the onion andcalamari fryers were topped upwith fresh oil during the day, i.e.,when the oil level dropped belowthe set minimum. The residual oil(when too dark in colour) wasrecovered from the fryers and thevolumes measured. Subsequentlythe oil throughput as well asyields was calculated. A customeracceptance survey of the friedfoods was carried out bydistributing a five-point facialhedonic scale (1 = bad, 5 =excellent) smiley facequestionnaire for the chips, onionsand calamari to customers beforethey left the restaurant.

RESULTS AND DISCUSSION

This extensive frying studyinvolved a long period of about30 days of long hours (15 hr)intermittent frying and was doneaccording to the frying proceduresof the restaurant. Palm oil waschosen because it is durableunder extreme frying conditionswhile sunflower oil was selectedas control because it is the majorcooking and frying oil in SouthAfrica. In this study, only PTG,TPC and fatty acid composition

(FAC) were analysed. PTG andTPC are the legislated parametersused to indicate the discard pointsof frying oil in South Africa. Asthe used oils are sold to the poor,it is important to ensure that thePTG and TPC of the discarded oilare within the regulatory limits.FAC analysis was conducted toverify the type of oil used forfrying and to observe if anyparticular fatty acids werepreferentially oxidized. A customeracceptance test was alsoconducted because it is thecustomer who finally decideswhether the fried food isacceptable or not.

Chips Fryer

The PTGs of palm oilremained below 5% throughoutthe trial period of 31 days andfluctuated within a narrow range(average 3.6%; range: 1.9%–4.9%). The PTGs of sunflower oilthroughout the trial of 29 dayswere higher, about twice those ofpalm oil. The PTG range was alsowider (average 8.1%; range:6.3%-13.8%). The average TPCof palm oil was 16.1% with arange of 10.7%-22.3% while thatof sunflower oil was higher at21.1% with a range of 15.6%-30.3%. Towards the end of thetrial for sunflower oil, the TPCswere already above the regulatorylimit of 25%. Chips fried in palmoil received consistently higherrating from the customers(average 4.7 points; range: 4.5–5.0 points) while those ofsunflower were lower with someof the scores below 4 points(average 4.4 points; range: 3.5–5.0 points) (Figures 2, 3, 4 andTable 2).


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Figure 1. The fryer in the kitchen of Spur Restaurant.

Figure 2. Percentage polymerized triglycerides (PTG) of oil in chips fryer.

Days

0 5 10 15 20 25 30 35

% P

TG

0

2

4

6

8

10

12

14

16

% P

TG

DaysSunflower oil (•), palm olein (•)


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Figure 3. Consumer acceptability for foods fried in palm oil.

Figure 4. Consumer acceptability for foods fried in sunflower oil.

Hed

onic

rat

ing

Hedonic rating chips Hedonic rating onion Hedonic rating calamari

Hed

onic

rat

ing

Hedonic rating chipsHedomic rating calamari

Hedonic rating onion

8/5/2003 11/5/2003 14/5/2003 17/5/2003 5/20/2003 23/5/2003 26/5/2003 29/5/2003

Time (days)

Time (days)

8/6/2003 11/6/2003 14/6/2003 17/6/2003 20/6/2003 23/6/2003 26/6/2003 25/6/2003


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TABLE 2. SUMMARY OF PTG, TPC, CUSTOMER ACCEPTANCE AND OIL CONSUMPTION

Characteristic Fryer Palm olein Sunflower oil

PTG (%) Chips 3.6 (1.9–4.9) 8.1 (6.3–13.8)Onion 3.1 (1.5–4.9) 9.1 (5.5–13.0)Calamari 5.3 (2.4–9.8) 9.9 (4.7–14.6)

TPC*(%) Chips 16.1 (10.7-22.3) 21.1 (15.6-30.3)Onion 17.5 (10.7-25.9) 24.3 (14.3-33.4)Calamari 17.4 (10.1-24.6) 23.4 (16.6-33.0)

Customer Chips 4.7 (4.5–5.0) n = 563 4.4 (3.5–5.0) n = 108acceptance (point) Onion 4.2 (3.7–5.0) n = 509 4.1 (3.0–5.0) n = 104

Calamari 4.7 (4.2–5.0) n = 194 3.8 (2.5–5.0) n = 65

Food fried (kg) Chips 4 298 3 130Onion 1 101 1 152.5Calamari 127.33 96.49

Total (kg) 5 526.33 4 378.99

Total oil used (kg) 1 170 1 224

kg food/kg oil used 4.7 3.6

Notes: n = number of customers surveyed.*Only samples on days 1, 10, 20 and 30 were analysed.

Onion Fryer

For the onion rings fried inpalm oil, similar results wereobtained with an average PTGvalue of 3.1% (range: 1.5%-4.9%). Higher PTGs wereobserved with sunflower oil withan average of 9.1% (range:5.5%–13.0%) (Figure 2). Theaverage TPC of palm oil was17.5% with a range of 10.7%-25.9%. Higher TPCs wereobserved with sunflower oil withan average of 24.3%, just belowthe regulatory limit, in the rangeof 14.3%-33.4%, indicating thatsome of the oil had exceeded thelimit at the end of the trial (Table2). For palm oil, a very highcustomer rating was obtained forthe onion rings (average: 4.2points; range: 3.7–5.0 points)(Figure 3). A high rating was alsoobtained for the onion rings friedin sunflower oil (average: 4.1points; range: 3.0-5.0 points) butwith a bigger spread (Figure 4).

Calamari Fryer

For both oils, higher PTGvalues were obtained for the

calamari fryer than from theirchips and onion fryers (Figure 6).While the average PTG value forpalm oil was 5.3% (range: 2.4%–9.8%), that of sunflower oil wasalmost twice as high (average:9.9%, range: 4.7%–14.6%).The highest (i.e. 14.6%) in therange was very close to the 16%limit. The TPCs of palm andsunflower oils in the calamarifryer were almost similar to theones in their onion fryer. Thefluctuating curves of PTG valuesfor both oils in the calamari fryerwere sharper than the curves ofthe oils in the chips and onionfryers. However, the palm oilcurve was of a narrower spreadthan that of sunflower oil. Thesharper curves were probably dueto faster deterioration of the oilsin the calamari fryer as it was thedeteriorated oil from the onionfryer. Even topping up thedeteriorated oil with fresh oil didnot help much in improving thequality of the oil as it degradedquickly.

The PTG regulatory limit of16% is also found to be at thehigher side because from this

study, it was observed that whilethe TPGs are still within theregulatory limit, the TPCs haveexceeded it. A lower limit of 10%as in some other countries wouldbe more suitable.

In general, calamari fried insunflower oil received a lowerscore (average: 3.8 points, range:2.5-5.0 points) by the customersthan fried in palm oil (average:4.7 points, range: 4.2-5.0 points)Thus, the quality of frying oilinfluenced the customeracceptance of the fried foods. duPlessis et al. (2000) mentionedthat when a frying oil reaches theregulatory limits, it is no longerorganoleptically acceptable. In thiscase, some of individual customerscores were less than three pointsfor calamari fried in sunflower oilbecause the oil was heavilydeteriorated, causing increasedsurface oil pick up. Theobservation that surface oil pickup reduced the customeracceptance can also be seen fromthe lower scores for the onionrings compared to those for thechips and calamari because theonion rings absorbed more oil


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Figure 5. Percentage polymerized triglycerides (PTG) in oil for frying onion rings.

than the other two products(Figure 3). In the case of sun-flower oil, the oil in the calamarifryer was so heavily deterioratedthat the surface oil pick up wasmore than the oil absorbed bythe onion rings, hence, the lowercustomer acceptance (Figure 4).By comparing Figures 3 and 4with the development of PTG andTPC during the frying, it can beconcluded that higher PTGcaused higher oil pick up by friedfoods and consequently, lowercustomer acceptance. This wasbecause the PTG of palm oil inthe calamari fryer remained low,thus, the calamari fried in itmaintained a high customer ratingdespite the higher TPC values,while sunflower oil in the calamarifryer had higher PTG values withlower customer rating on thefried calamari. However, all theseobservations would need to beconfirmed.

Fatty Acid Profile

For both oils in the chips,onion ring and calamari fryers,the fatty acid profiles were within

their standard specifications andremained so throughout the runs,indicating that pure palm oil andsunflower oil were used (Figures7 and 8). For palm oil, there wasno particular fatty acid preferen-tially oxidized. However, the palmoil supplied might not have beenwell homogenized from batch tobatch as can be seen from thehigher palmitic acid contents atsome points of the trial. Forsunflower oil, there was a de-creasing linoleic acid contenttowards the end of the trial. Thefatty acid variation throughoutthe study was less in palm oleinthan in sunflower oil.

Oil Consumption

When palm oil was used,1170 kg were needed to fry5526.33 kg food (i.e. 4.7 kgfood/kg oil). The food comprised4298 kg chips, 1101 kg onionsand 127.33 kg calamari (Table 2).However, when sunflower oil wasused, 1224 kg were needed tofry 4378.99 kg food (i.e. 3.6 kgfood/kg oil). The food comprised3130 kg chips, 1152.5 kg onions

and 96.49 kg calamari. Theseresults indicate that moresunflower oil is needed to fry thesame amount of food. This wasdue to the fact that surface oilpick up by the food was morewith sunflower oil, especiallywhen it was heavily deterioratedwith TPGs and TPCs nearing orcrossing the regulatory limits. Asimilar observation was madeby Razali and Badri (2003) withchips fried in palm oil, palm olein,soyabean oil and hydrogenatedsoyabean oil for five consecutivedays, 8 hr per day. The Frenchfries done in soyabean oilabsorbed more fat than in theother three oils because itcontained higher PTG.

CONCLUSION

Sunflower oil was much lessstable than palm oil over the 29-day trial in the frying of chips,onion rings and calamari rings bythe Spur process. On average,when frying calamari, palm andsunflower oils degraded morethan when the other foodstuffswere fried because of the reasons

Days

0 5 10 15 20 25 30 35

% P

TG

0

2

4

6

8

10

12

14

16

% P

TG

DaysSunflower oil (•), palm olein (•)


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Figure 6. Percentage polymerized triglycerides (PTG) of oil in the calamari fryer.

Figure 7. Fatty acid changes in palm olein in the chips fryer during frying.

Days

0 5 10 15 20 25 30 35

% P

TG

0

2

4

6

8

10

12

14

16

Sunflower oil (•), palm olein (•)

% F

atty

aci

ds

30/4/

2003

3/5/20

03

5/6/20

03

9/5/20

03

12/5/

2003

15/5/

2003

18/5/

2003

21/5/

2003

24/5/

2003

27/5/

2003

30/5/

2003

Palmitic acid Stearic acid Oleic acid Linoleic acid


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Figure 8. Fatty acid changes of sunflower oil in the chips fryer during frying.

mentioned earlier. The maximumbreakdown levels of 13.8% PTGsfor chips, 13.0% PTGs for onionsand 14.6% PTGs for calamari,with sunflower oil were muchhigher and closer to theregulatory limits than the levelswith palm oil, i.e. maximumvalues of 4.9%, 4.9% and 9.8%,respectively.

Similar observations were madeon TPC. The average TPCs ofpalm oil after frying chips, onionand calamari were 16.1%, 17.5%and 17.4%, respectively, all belowthe regulatory limit of 25%.However, at the end of the trial,the TPC readings were close to orslightly over the limit. Theaverage TPC readings of sunfloweroil for the chip, onion andcalamari fryers were 21.1%,24.3% and 23.4%, respectively.It is obvious that at the end ofthe trial, the TPC readings ofsunflower oil from all the fryerswere well above the regulatorylimit of 25%.

More food was prepared perunit oil with palm oil (i.e. 4.7 kg/kg oil) than sunflower oil (i.e. 3.6kg/kg oil). This was because thesunflower oil degraded faster andthe degraded oil had a highersurface oil pick up by the foods.

There was no obviousdifference between the averagecustomer acceptance of the chipsand onions fried in both oilsalthough the foods fried insunflower oil obtained the lowestindividual ratings. However, therewas a significantly bettercustomer acceptance of calamarirings fried in palm oil comparedto the rings fried in sunflower oil.

Both palm and sunflower oilsdid not reach the regulatory limitof 16% PTG after a month offrying although the sunflower oilhad almost double the PTG valueof palm oil. But the oils hadreached or were close to theregulatory limit of 25% TPC after,respectively, 20 and 30 days offrying. Thus, sunflower and palmoils should be discarded,respectively, after 20 and 30 daysof frying when the Spur fryingprocedure is used.

Further studies on the bestfrying practices for restaurants areneeded to derive the best fryingpractices as a balance betweencost and quality.

REFERENCES

AUGUSTIN, M A; HENG, L K andTEAH, Y K (1987). Comparison of

the frying performance of marketsamples of palm olein, corn oiland soya oil in Malaysia.Pertanika, 10: 3, 295-304.

ANON (1996). Foodstuffs,Cosmetics and Disinfectants Act,1972 (Act 54 of 1972). Regula-tions published on 16 August1996.

ANON (2000). Recommendationof the 3rd InternationalSymposium on Deep Frying.organized by DGF, Hagen,Germany, 20-21 March 2000.

DU PLESSIS, L M; VAN TWISK, Pand PARSONS, T (2000).Manual on Frying Oil for Use byFast Food and Industrial SnackManufacturers. MPOB, Bangi. 15pp.

HAW, P (2003). Boil, oil andtrouble. South African FoodReview, June 2003: 27-31.

JOHARI MINAL; DU PLESSIS, L,M; BARKHUYSEN, M; VILJOEN,H; ABDULLAH ARIFFIN; ISAMANSOR and RAZALI, I (2003).South Africa’s initial experience inusing palm olein blend for themanufacture of pre-fried Frenchfries.

Palmitic acid

% F

atty

aci

ds

Stearic acid Oleic acid Linoleic acid

1/6/2003 4/6/2003 7/6/2003 10/6/2003 13/6/2003 16/6/2003 19/6/2003 22/6/2003 25/6/2003 28/6/2003

Time (days)


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KOCK, J L F; BOTHA, A; BLOCH,J and NIGAM, S (1996). Usedcooking oil: science tackles apotential health hazards. SouthAfrican Journal of Science, 92:513-514.

KOCK, J L F; POHL, C H andVENTER, A (2002). Superoxidisedsoups and the health risks topoor South Africans. S. Afr. J.Sci., 98: 413-414.

KOCK, J L F; POHL, C H andVENTER, A (2003). Oil & FatWorkshop. Lipid BiotechnologyGroup, University of the FreeState, South Africa.

MASASHI, S; YOSKIKAZU andMASANORI, S (1985). Quality offried foods with palm oil. J.Amer. Oil Chem. Soc., Vol. 62:449-454.

RAZALI, I; IFTIKHAR, A; RAZALI,M; SINGH, B R; ASHRAF, E Mand MAKER, P (2001).Development of palm oil-basedliquid frying oils for home andstar rated restaurants in Oman.MPOB Report G (402) 2001.Restricted.

RAZALI, I and BADRI, M (2003).Oil absorption, polymer and polarcompounds formation duringdeep fat frying of French fries invegetable oils. Palm OilDevelopments No. 38: 11-15.

RAZALI, I (2005). Palm oilproducts in cooking and frying.Selected Readings. 20th Palm OilFamiliarization Programme, 21July –10 August 2005, KualaLumpur.

SIEW, W L (2005). Chemical andphysical characteristics of palmand palm kernel oils and theircrystallization behaviour. SelectedReadings. 25th Palm OilFamiliarization Programme, 31-10August 2005.

SUNDRAM, K (2005). Nutritionalproperties of palm oil and itsfractions: a review. SelectedReadings. 25th Palm OilFamiliarization Programme, 31-10August 2005.

TOREGARD, B and ERIKSSON, A(1979). Proc. of the 10th

Scandinavian Symposium onLipids. Nyborg, Denmark

ZEDDELMANN, H andWURZIGER, J (1973). Fette SeifenAnstrichmittel, 81:498.

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