Lebensm.-Wiss. u.-Technol.

, 29, 573–577 (1996)

Research Note

Utilization of Jojoba Oil for Deep-fat Frying of Foods

I.S. Saguy*, A. Shani, P. Weinberg and N. Garti

I.S. Saguy, P. Weinberg: Department of Biochemistry, Food Science and Nutrition, The Hebrew University of
Jerusalem, P.O. Box 12, Rehovot 76100 (Israel)
A. Shani: Department of Chemistry, Ben-Gurion University of the Negev, Beer-Sheva 84105 (Israel)
N. Garti: Casali Institute for Applied Chemistry, The Hebrew University of Jerusalem, Jerusalem (Israel)
(Received September 22, 1995; accepted October 26, 1995)

Jojoba oil is a mixture of long chain esters comprising C18, C20, C22 and C24 monounsaturated acids and alcohols, but in particular
two ester molecules containing 40 and 42 carbon atoms which make up to 80% of the oil. Five quality parameters of Jojoba oil
were compared with cotton oil in time–temperature conditions simulating abusive industrial deep-fat frying. In four out of five
quality criteria, namely, colour index, oxidation index, peroxide value and viscosity, Jojoba oil was found to be superior to cotton
oil, while free fatty acids showed comparable low values, within the range expected, in industrial frying operations. Oil uptake of
a deep-fried restructured potato product was significantly higher in Jojoba oil as compared to cotton oil. The enhanced stability
during deep-fat frying of Jojoba oil could play a part in improving the shelf-life of fried foods.

©1996 Academic Press Limited

Introduction (9). Additional applications include a mixture of JO

and glyceride oils (80:20 by wt.) for frying scrambled
Reduction of calories derived from oils and fats from eggs (10), and others (11–15).
37% to 20–30% is a health and nutritional goal yet to The utilization of JO to replace frying fat in large- or
be met (1). In addition, cholesterol in blood serum small-scale food frying operations is still not feasible,
causes concern and measures taken toward lowering its nevertheless its application could be advantageous as it
level below 200 mg/dL are to be viewed positively. To is triglyceride-free and does not break down as com-
facilitate reducing these nutritional risks, numerous pared to regular fats, and could be used for extended
fatty substitutes have been developed in recent years, industrial frying periods (16).
most of them based on protein and carbohydrates. The main objectives of this study were to assess the
However, these substitutes usually cannot replace oils performance of JO for deep-fat frying of foods and to
used in cooking, baking and frying (2). Jojoba liquid compare its oxidation stability with cottonseed oil.
wax (Simmondsia chinensis Buxaceae; jojoba ‘oil’, JO),
produced by the seeds of the female plant of the once
wild bush is a narrow mixture of long-chain esters, Materials and Methods
composed mainly of monounsaturated C18, C20, C22 and
C24 acids and alcohols, in particular two ester molecules Frying
containing 40 and 42 carbon atoms which make up to An extruded restructured potato product (17), cylinder-
80% of the oil (3). shaped (0.02 m diameter 3 0.03 m length), was fried in
Jojoba oil is scarcely hydrolysed by pancreatic lipases a bench-top deep-fat fryer (0.12 m depth), containing
(4). Only ca. 40% is digested when incorporated into 2.5 L oil. Cotton oil was obtained from a local
animal diets at significant and practical levels (5), and manufacturer and compared to jojoba oil (Jojoba
its caloric value (in terms of nutrition) could be even Israel, Ltd., Tel Aviv). Both oils were exposed to an
lower (6). Although JO cannot be used in foods until extended frying process carried out in two stages,
proper approval by EC authorities or the FDA (7), lasting 22.3 h (Table 1). In stage I, restructured potato
several applications have been reported, including samples (triplicate) were fried individually (to mini-
coating of foodstuffs (e.g. chocolate, dried fruit), which mize temperature drop) at 175, 185 and 195 °C, for 300
greatly improved stability and reduced moisture loss s. Fryer time and temperature are listed in Table 1.
even in comparison with hydrogenated oil coating (8). Samples were removed from the fryer, and allowed to
Beneficial results were also demonstrated in studies cool to room temperature (23 ± 2 °C) on a paper towel.
focusing on replacing edible fats and oil by JO in In stage II, the same oil used in stage I was heated to
margarine and mayonnaise (4), and for deep-fat frying 205 °C and kept at this temperature for more than 19 h.
To simulate a controlled frying process (Table 1), 2 mL
*To whom correspondence should be addressed. water in the form of small drops was added with a
0023-6438/96/050573 + 05$18.00/0 ©1996 Academic Press Limited

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 lwt/vol. 29 (1996) Nos. 5 & 6

Table 1 Effect of abusive time–temperature conditions simulating deep-fat frying on oil quality parameters
Jojoba oil Cotton oil
Oxidation Peroxide Oxidation Peroxide
Time Temp. Colour index FFA value Viscosity Colour index FFA value Viscosity
(h) (°C) index (mmol/L) (%) (mEq.O2/kg) (mPa s) index (mmol/L) (%) (mEq.O2/kg) (mPa s) Comments
0 175 0.789 4.97 0.19 0.84 28 0.528 13.26 0.08 0.60 40. Oil break-in
2.3 175 0.100 4.68 0.20 2.22 29 0.701 38.50 0.13 5.52 45 Sample frying
3.0 185 0.072 4.47 0.21 2.45 30 0.748 41.79 0.14 6.36 47 Sample frying
3.6 195 0.054 6.57 0.24 2.68 31 0.760 58.90 0.15 7.67 48 Sample frying
8.6 205 0.068 7.03 0.29 2.83 34 0.954 56.03 0.18 7.67 53 +2 mL water
11.8 205 0.080 7.99 0.35 3.10 35 1.120 66.29 0.20 5.60 60 +2 mL water

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15.1 205 0.084 8.52 0.41 3.22 41 1.419 71.75 0.25 4.83 68 +2 mL water
18.3 205 0.101 10.31 0.48 2.91 42 1.670 68.46 0.24 5.13 75 +2 mL water
22.3 205 0.130 8.44 0.60 2.91 45 2.066 74.50 0.41 3.45 83 +2 mL water
 lwt/vol. 29 (1996) Nos. 5 & 6

Pasteur pipette after 8.6, 11.8, 15.1, 18.3 and 22.3 h initial yellow colour to a clear almost colourless fluid.
(Table 1). Oil samples were withdrawn periodically Even after extensive and abusive time–temperature
(Table 1) and analysed in duplicate. Sampling routine exposure (175 to 205 °C for up to 22.3 h), the colour
for both oils was identical. index remained as low as 0.130 ( ± 0.002). This colour
reduction is a distinct characteristic of JO not matched
by any other frying oil. On the other hand, cotton oil
Colour index showed a marked increase in colour index with frying
Absorption at 420 nm was determined on a spec- time. The increase is probably due to oxidation typically
trophotometer and read against water as blank. resulting in the generation of hydroperoxides, conju-
gated dienoic acids, epoxides, hydroxides and ketones.
These compounds could undergo further oxidation, and
Oxidation index fission into smaller fragments or may remain in the
Oxidation index, defined as the absorption of conju- triglyceride molecule and cross-link with each other,
gated dienes, was followed spectrophotometrically leading to dimeric and higher polymeric triglycerides
(UV/Visible Philips Cambridge, U.K.) at 234 nm (18). (22). Fats can also produce dimeric acids, and form
The oil sample was diluted (1:240 and 1:1200 for JO and polymers of higher molecular weight, causing a darker
cotton oil, respectively) with hexane (HPLC grade). An colour and a deposit of yellow or brown pigments (23).
extinction coefficient of 29,000 mol/L (19) was utilized The oxidation process and polymerization of cotton oil
to quantify the concentration of conjugated dienes was accompanied by a viscosity increase(40 ± 2 to
formed during oxidation. 83 ± 5 mPa.s), while JO viscosity remained relatively
low (28 ± 2 to 45 ± 2 mPa.s).
Free fatty acid (FFA) is one of the indicators utilized to
Free fatty acid (FFA) assess oil quality during the frying process. It can be
Oil samples were titrated with 0.01 mol/L KOH (20). used to determine the total content of reactive acid
Data are expressed as percent of oleic acid. groups in the oil. Although FFA is not a good
parameter for comparing different frying processes or
oil stability, it could be used as an indicator to show
Peroxide value (PV) whether the process is in control. Therefore, the values
Standard method (20) was utilized. Data are expressed reported, although somewhat higher for JO, are still
as peroxide value (mEq.O2/kg). within the range expected during a regular industrial
frying operation.
The level of oil primary oxidation is measured by
Viscosity peroxide value. However, as peroxides are very unsta-
A Brookfield LV (Brookfield Engineering Lab. ble at typical frying temperatures, PV content is often a
Stoughton, MA) equipped with an SC4-19 spindle was criterion of the peroxides generated during the cooling
used to measure the viscosity of the oil samples at 30 process. Hence, to compare the two oils, identical
°C. The shear rate ranged from 10 to 50 s–1 and the sampling and cooling procedures were applied. The
Newtonian viscosity was determined. data (Table 1) clearly show a difference between the
two oils. While cotton oil showed a rapid increase (from
0.60 ± 0.03 to 7.67 ± 0.21 mEq.O2/kg) after only 3.6 h,
Other analyses JO reached its maximum (from 0.84 ± 0.04 to
Moisture content, oil uptake and UR criterion (defined 3.22 ± 0.15 mEq.O2/kg) after a much longer time (15.1
as the weight ratio (g/g) between the amount of oil h) and higher frying temperatures (195 to 205 °C). As
uptake and water removed) were determined as expected, in both cases, PV reached a peak and levelled
described previously (21). Oil uptake is expressed as off. A more reliable method than the PV method for
g/100 g dry matter, excluding fat. All data were comparing oil stability is the active oxygen method
statistically analysed using Statistix (Analytical Soft- (AOM). Dienoic acids, such as linoleic acid, are much
ware, St. Paul, NM). When treatment effects were more sensitive towards oxygen and the rate of peroxide
significant (α = 0.01), the least significance difference formation is much faster (24). Typical AOM values are
(LSD) test was used. 14, 45, and 40 to 50 h for cotton oil, high oleic sunflower
oil (25) and JO (Jojoba Israel, Ltd.), respectively.
The above values are not surprising if they are related
Results and Discussion to the oils chemical structure. There are two major
differences between cottonseed oil and JO. Cottonseed
The effect of frying time and temperature on oil oil is a triglyceride while JO is a narrow mixture of long
characteristics is listed in Table 1. The data show a clear chain esters. The degree of unsaturation in the fatty
distinction between cotton oil and JO in colour, acids (and alcohols in JO) is also different. Three major
oxidation indexes, FFA, peroxide values and viscosity. fatty acids comprise cotton oil (saturated palmitic acid
However, the differences are not consistant, and each 22–26%, monounsaturated oleic acid 16–19% and
characteristic should be evaluated separately. diunsaturated linoleic acid 49–58%) (23). The compo-
The colour index of JO decreased significantly from its nents of JO are monounsaturated entities, thus it is

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lwt/vol. 29 (1996) Nos. 5 & 6

more like a high oleic sunflower oil (i.e. palmitic acid, of long chain esters exhibiting high stability at frying
8%; oleic acid, 80%; and linoleic acid, 12%) (25). temperatures manifested by its light colour and an
Hyderoperoxides resulting from oxidation of the diene order of magnitude lower oxidation index measured as
system in linoleic acid are later cleaved to yield short conjugated dienes that absorb UV. The enhanced
chain volatile aldehydes and hydrocarbons (26) which chemical stability may make a significant contribution
evaporate during the frying process (24). Simultane- to improving the shelf-life of fried food products by
ously, longer diunsaturated aldehydes (e.g. 2,4-decan- reducing the deterioration reactions related to fat
dienals) are left behind and may increase the PV of oxidation.
fried linoleic-rich oil (24). Such products are produced
less during frying of oleic acid, and the hydroperoxides
formed from the monounsaturated acid remain their
original length. This might furnish an explanation for References
the lower values of PV observed in JO. Furthermore,
1 ANONYMOUS Limit fat intake to 20–25% of calories.
the oxidation process is accompanied by the formation INFORM, 5, 1279 (1994)
of conjugated dienes units which absorb UV light in the 2 ANONYMOUS. Fat Reduction in Foods. Atlanta, GA:
region of 232–234 nm. As conjugated dienes are formed Calorie Control Council (1993)
mainly from linoleic or linolenic acid during oxidation, 3 ANONYMOUS. Jojoba, New Crop for Arid Lands, New Raw
it is not surprising that the oxidation index of JO Material for Industry. Washington, DC: National Academy
Press (1985)
(resembling sunflower oil that contains ca. 12% linoleic 4 HAMM, D.J. Preparation and evaluation of trialkoxy-
acid) was lower than its counterpart measured for tricarballylate, trialkoxyciltrate, trialkoxyglycerylether,
cotton oil (containing ca. 49–58% linoleic acid). How- jojoba oil and sucrose polyester as low calorie replace-
ever, the ratio between the respective oxidation indexes ments of edible fats and oils. Journal of Food Science, 49,
is much higher than explained by the relative concen- 419–428 (1984)
5 ANANTHARAMAN, K. Jojoba oil — nutritional and safety
tration of the fatty acids. Hence, heating these oils in studies and potentials in clinical nutrition. In: IX Inter-
the presence of air had a profound effect on cotton oil, national Conference on Jojoba and Its Uses, Catamarca,
while JO is much less affected. This explains the order Argentina (1994)
of magnitude difference observed between cotton oil 6 HEISE, C., DECOMBAZ, J. AND ANANTHARAMAN, K. Energy
and JO oxidation index, expressing the oxidation index value of jojoba oil for the growing rats. International
Journal of Vitamins and Nutrition, 52, 216–217 (1982)
as measured by their conjugated double bonds at 234 7 PARK, D.L. AND CARSON, K.L. Regulatory requirement for
nm. food use of jojoba oil. In: VII International Conference on
Oil uptake data (Table 2) show that frying in JO Jojoba and Its Uses, Phoenix, Arizona, pp. 354–364
resulted in a significantly (P < 0.01) higher oil uptake (1988)
both on a dry basis and UR criterion. Although frying in 8 DEVITT, M.T. AND RUSSELL, J.B. Edible oil. US Patent
4,356,197 (1982)
JO could result in a higher uptake, hardly any JO is 9 CLARKE, J.A. AND YERMANOS, D.M. The use of jojoba oil
hydrolysed by pancreatic lipases (4) (only ca. 40% is in deep fat frying. In: IV International Conference on
digested when incorporated into animal diets at sig- Jojoba and Its Uses, Hermosillo, Mexico, pp. 261–265
nificant and practical levels) (5). Hence, if JO was (1980)
approved by the authorities, a significant reduction in 10 KIMURA, A. AND HAYASHI, T. Jojoba oil and glycerides oils
for frying scrambled eggs. Chemical Abstract, 114, 5123z
caloric value due to oil absorbed during frying could be (1991)
achieved. Data (Table 2) also show that the amount of 11 CLARKE, J.A. AND YERMANOS, D.M. Effects of ingestion of
oil absorbed by a product was independent of frying JO on blood cholesterol levels and lipoprotein patterns in
temperature within the range 175 to 195 °C. A similar New Zealand white rabbits. Biochemical and Biophysical
observation has been made previously (27). Research Communications, 102, 1409–1415 (1981)
12 JAMES, K.A.C., BODY, D.R. AND SMITH, W.C. A nutritional
It is worth noting that Jojoba oil is mentioned as a evaluation of Orange Roughy (Haplostethus atlanticus)
potential fat replacement, while keeping the functional using growing pigs. New Zealand Journal of Technology, 2,
organoleptic properties of fats and oils to foods (28). 219–223 (1986)
However, further studies on the organoleptic attributes 13 VERSCHUREN, P.M. Evaluation of jojoba oil as a low-
of foods fried in JO is required. energy fat. I. A 4-week feeding study in rats. Food
Chemistry and Toxicology, 27, 35–44 (1989)
In conclusion, JO has unique quality characteristics 14 VERSCHUREN, P.M. AND NUGTEREN, D.H. Evaluation of
different from other frying oils. JO is a narrow mixture jojoba oil as a low-energy fat. II. Intestinal transit time,
stomach emptying and digestibility in short-term feeding
studies in rats. Food Chemistry and Toxicology, 27, 45–48
Table 2 Effect of media on oil uptake during deep-fat frying (1989)
(5 min) of a restructured potato product 15 VERSCHUREN, P.M. Basic aspects of nutritional assessment
Jojoba oil Cotton oil — jojoba oil. International Journal of Food Science and
Frying Nutrition, 44 (Suppl. 1), S83–S86 (1993)
temperature Oil uptake Oil uptake 16 ANIKA, K. Veerfahren zur Herstellung von fettrreiem
(°C) (g/100g) UR (g/100g UR Frittiergut. German Federal Republic Patent Application
DE 3,529,565 A1 (1987)
175 33.6 0.66 25.2 0.57 17 PINTHUS, E.J., WEINBERG, P. AND SAGUY, I.S. Gel-strength
185 33.7 0.66 27.9 0.58 in restructured potato product affects oil uptake during
195 35.3 0.67 27.6 0.57 deep-fat frying. Journal of Food Science, 57, 1359–1360
(1992)

576
 lwt/vol. 29 (1996) Nos. 5 & 6

18 SHIMADA, Y., ROOS, Y. AND KAREL, M. Oxidation of 25 JONES, L.A. AND KING, C.C. Cottonseed Oil. Memphis, TN:
methyl-linoleate encapsulated in amorphous lactose- National Cottonseed Products Association, The Cotton-
based food model. Journal of Agriculture and Food seed Foundation (1993)
Chemistry, 39, 637–641 (1991) 26 FRANKEL, E.N. Formation of headspace volatiles by
19 PRIVETT, O.S. AND PLANK, M.L. The initial stages of thermal decomposition of oxidized fish oils vs. oxidized
autoxidation. Journal of the American Oil Chemists’ vegetable oils. Journal of the American Oil Chemists’
Society, 39, 465–469 (1962) Society, 70, 767–772 (1993)
20 AOAC. Official Methods of Analysis. Washington, DC: 27 GAMBLE, M.H., RICE, P. AND SELDMAN, J.D. Relationship
Association of Official Analytical Chemists (1984) between oil uptake and moisture loss during frying of
21 PINTHUS, E.J., WEINBERG, P. AND SAGUY, I.S. Criterion for potato slices. from c.v. Record U.K. tubers. International
oil uptake during deep-fat frying. Journal of Food Science, Journal of Food Science and Technology, 22, 233–241
58, 204–205, 222 (1993) (1987)
22 WHITE, P.J. Methods for measuring changes in deep-fat 28 HAUMANN, B.F. Getting the fat out. Researchers seek
frying oils. Food Technology, 45(2), 75–80 (1991) substitutes for full-fat. Journal of the American Oil
23 BLUMENTHAL, M.M. A new look at the chemistry and Chemists’ Society, 63, 278–280 (1986)
physics of deep-fat frying. Food Technology, 45(2), 68
(1991)
24 MELTON, S.L., JAFAR, S., SYKES, D. AND TRIGIANO, M.K.
Review for stability measurements for frying oils and fried
food flavor. Journal of the American Oil Chemists’ Society,
71, 1301–1308 (1994)

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