Monitoring of Edible Oils Quality in Restaurants and Fast Food Centers Using Peroxide and Acid Values

Abstract

Continuous surveillance and monitoring of used materials in food processing is a tool for achieving to food safety assurance. Peroxide and Acid values are common indicators to detect fat oxidation, frequent and longtime heating and usage of edible oils in cooking or frying of food. This study aimed to quality assessment of used edible oils in restaurants and fast food centers (Sandwich centers) of Zanjan, Iran by determination peroxide value (PV) and acid value (AV). A total 60 oil samples were collected randomly from restaurants (27 samples) and fast food centers (33 samples) based on cluster sampling plan of the Zanjan city. Titration methods were used to determine Peroxide and Acid values according to Iran national standards protocols No. 4179 and 4178. Peroxide value in 22 (81.48%) and 24 (80%) of oil samples and Acid value in 22 (81.48%) and 30 (90.9%) of samples taken from restaurants and fast food centers were higher than standard limit, respectively. Present investigation has shown that High PV and AV in used edible oils of many restaurants and fast food centers in Zanjan, Iran. High range of Peroxide and Acid values indicate an improper use of oils in food preparing centers and presence toxic compounds in used oils and foodstuffs which threaten food consumers' health. Therefore, continuous surveillance and monitoring of restaurants and food preparing centers and training of chefs, food operators in order to apply proper methods of cooking and frying food is very important and necessary.

Full text

JCHR (2018) 8(3), 217-222
Journal of Chemical Health Risks
www.jchr.org
ORIGINAL ARTICLE
Monitoring of Edible Oils Quality in Restaurants and Fast Food
Centers Using Peroxide and Acid Values
Hassan Hassanzadazar*1, Farhad Ghaiourdoust2, Majid Aminzare 1, Ehasan Mottaghianpour1, Borzoo Taami1
1Department of Food Safety and Hygiene, School of Public Health, Zanjan University of Medical Sciences, Zanjan, Iran
2Department of Environmental Health Engineering, School of Public Health, Zanjan University of Medical Sciences,
Zanjan, Iran
(Received: 19 April 2018 Accepted: 21June 2018)
KEYWORDS
Determination;
Frying;
Quality assessment;
Sandwich centers;
Zanjan
ABSTRACT: Continuous surveillance and monitoring of used materials in food processing is a tool
for achieving to food safety assurance. Peroxide and Acid values are common indicators to detect fat
oxidation, frequent and longtime heating and usage of edible oils in cooking or frying of food. This
study aimed to quality assessment of used edible oils in restaurants and fast food centers (Sandwich
centers) of Zanjan, Iran by determination peroxide value (PV) and acid value (AV). A total 60 oil
samples were collected randomly from restaurants (27 samples) and fast food centers (33 samples)
based on cluster sampling plan of the Zanjan city. Titration methods were used to determine Peroxide
and Acid values according to Iran national standards protocols No. 4179 and 4178. Peroxide value in 22
(81.48%) and 24 (80%) of oil samples and Acid value in 22 (81.48%) and 30 (90.9%) of samples taken
from restaurants and fast food centers were higher than standard limit, respectively. Present
investigation has shown that High PV and AV in used edible oils of many restaurants and fast food
centers in Zanjan, Iran. High range of Peroxide and Acid values indicate an improper use of oils in food
preparing centers and presence toxic compounds in used oils and foodstuffs which threaten food
consumers' health. Therefore, continuous surveillance and monitoring of restaurants and food preparing
centers and training of chefs, food operators in order to apply proper methods of cooking and frying
food is very important and necessary.
INTRODUCTION
Continuous surveillance and monitoring of used materials
in food processing is a tool for achieving to food safety
assurance [1]. Fats and edible oils are one of the most
important ingredients used in food processing, which play
an important role in flavoring, taste, consistency and
nutritional quality of foods. Frying is one of the oldest and
most popular methods for cooking and preparing foods
using edible oils in different sources including vegetables,
animals and fishes which are economically important for
global trade. [2, 3]. Heating and frying in the food
processing lead to changes in the chemical structure of
constituents or used ingredients such as proteins,
carbohydrates and lipids. Hydrolysis, polymerization and
thermo-xidation of lipids, denaturation of proteins and
*Corresponding author: Hassanzadazar_h@zums.ac.ir (H. Hassanzadazar)

H. Hassanzadazar et al / Journal of Chemical Health Risks 8(3) (2018) 217-222
218
Maillard reaction between proteins and carbohydrates occur
in heated foods [4, 5]. Each of these changes in vital
molecules especially lipids causes Changes in odor, taste,
color, texture, formation of toxic compounds, and losing
their nutritional quality [6, 7]. Lipid Hydrolysis results in
release of long and short chain free fatty acids and
acidification of the oil structure. Increasing of free fatty
acids (FFAs) facilitates oxidative reactions in the presence
of oxidants such as oxygen, heat and light. Development of
oxidation causes unpleasant changes such as loss of flavor,
nutritional value and color and leading to rancidity of the
oil [7, 8].
Lipid thermoxidation causes to accumulate many volatile
and non-volatile compounds in oils or food including
peroxides, hydroxyls, carboxylic acids, aldehydes, ketones
and etc. Peroxides are unstable compounds and quickly
converted to secondary metabolites and can create free
radicals that not only cause food spoilage but also can
damage body tissues of the consumers [7, 9]. Tissue
damage caused by free radicals and their effects on human
health are commonly seen as chronic signs. There are many
reports of mutagenicity, cytotoxicity, carcinogenicity,
teratogenicity, inflammatory diseases, cardiovascular
disease, liver disease, aging and diarrhea, abdominal pain,
nausea and vomiting, weakness and lethargy, headache and
etc. following the frequent use of rancid oils [8-12].
The deterioration degree of the oils and fats used in cooking
can be determined by measuring various parameters such as
Acid Value (AV), peroxide value (PV), saponification
value (SV), iodine value (IV), p-Anisidine and TOTOX
values, smoke point, viscosity, moisture content and color
[8,11]. AV and PV are common parameters to determine
the quality of oils or fats. Free fatty acids (FFAs) content
determines the acidity and the degree of hydrolysis in the
edible oil. In other words they show duration of exposure of
the oil or fat to hydrolyzing agent such as heat or light [1].
Acid value (AV) level shows FFAs content which is
determined based on the titration and chemical reaction of
free fatty acids with potassium hydroxide [13]. Peroxide
value shows the amount of peroxides and hydroperoxides
formed in the initial stages of lipid oxidation which is
determined by iodometric titration [14]. Albeit, newer,
faster and more precise titration methods based apparateus
analyzing are invented and used to determine the AV and
PV of edible oils or fats [1, 15]. Allowed limits of AV and
PV in Iranian national standard are ≤ 1 mgKOH /gr and 2-5
mEq/Kg of oil or fat, respectively [13, 14].
Today, consumption of ready-to-eat foods and food
consuming in restaurants and fast food centers (Sandwich
centers) is becoming accustomed due to lack of time to
cooking at home and food diversity. Considering to high
usage of oils or fats in restaurants and fast food centers for
cooking and frying of different foods, effects of frequent
heating on oil’s quality and destructive effect of
deteriorated oils on the individuals and society health
because of high content of toxic compounds, continuous
monitoring of used oil’s quality is necessary. Many studies
have been conducted throughout the world including Iran,
on the quality of the used oils for cooking and frying [6, 15-
18]. Consumption of ready-to-eat foods in restaurants and
fast food (Sandwich) centers is usual in Zanjan province,
Iran. Based on our knowledge according to literature
review, there are no study on quality of used oils in
restaurants and fast food centers in Zanjan province, Iran.
Therefore, this study aimed to determine the quality of used
oils for frying and cooking in restaurants and fast food
centers (Sandwich centers) in Zanjan, Iran.
MATERIALS AND METHODS
Sampling
In this descriptive cross-sectional study, during the spring
of 2017, 60 edible oil samples used for cooking and frying
food in 33 fast food centers (Sandwich centers) and 27
restaurants were collected in dark bottles based on the
cluster sampling plan of Zanjan, Iran. All samples were
transferred as soon as possible to the laboratory and the
amount of peroxide and acid values were evaluated in
accordance proposed national standard protocol of Iran NO.
4179 and 4178 [13, 14]. Sampling time at restaurants and
fast food centers was determined between 12:00 and 14:30.
Most activities were being performed to prepare foods at
this time in the above mentioned places. All measurements
were replicated three times.

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Peroxide value determination
The PV for oil samples were determined by titration
method based on national standard protocol of Iran [14].
Briefly, 5.00 g of each sample was weighed into a 250 ml
Erlenmeyer flask and 20 mL chloroform with 30 mL acetic
acid (2:3) was added to flask. After shaking, o.5 mL
saturated potassium iodide (KI) solution and 100 mL D.W
were added and swirled 1 minute. Then solution was slowly
titrated with 0.01N sodium thiosulphate with constant
shaking. It was continued for color changes to light yellow.
In this step 0.5 mL of 1 percent soluble starch as an
indicator was added to solution to change light yellow color
to blue. The sodium thiosulphate (Na2S2O3) was added
until disappearance of the blue color. All steps were
performed for blank solution. The following formula was
used to calculation of PV as meq peroxide/kg of oil:
        

V: Volume of sodium thiosulphate used for sample; V0:
Volume of sodium thiosulphate used for Blank; N:
Normality of sodium thiosulphate; m: Weight of sample
Acid value determination
The AV for oils samples were determined by titration
method based on national standard protocol of Iran [13].
Briefly, based on color and expected AV in samples,
adequate amount of oil was weighted and added into a 250
ml Erlenmeyer flask. In another flask, 50 mL ethanol
solution containing 0.5 mL Phenolphthalein indicator was
heated to the boiling point. After reaching the ethanol
temperature to 70ºC, it was added to first flak and it was
slowly titrated with 0.1N solution of KOH or NaOH and
continued until disappearing the color of solution. The
following formula was used to calculation of AV as
mgKOH/g of oil:
    

N: Normality of KOH solution; V: Volume of KOH used
for titration; m: Weight of sample
Statistical analysis
All tests were conducted in triplicate. The mean±SD,
minimum and maximum were obtained using SPSS
software (version 16, Chicago, IL, USA).
RESULTS
Table 1 and 2 show PV and AV content in the oil samples
collected from restaurants and fast food centers,
respectively. As is shown in table 1, PV was higher than
standard limit in 22 (81.48%) and 24 (80%) samples taken
from restaurants and fast food centers, respectively. AV
was higher than standard limit in 22 (81.48%) and 30
(90.9%) samples taken from mentioned places, respectively
(Table 2).
Table 1. Peroxide value (PV) range in oil samples taken from restaurants and Fast food (sandwich) centers of Zanjan
Fast food (Sandwich) centers
Restaurants
Sampling
Places
PV
(mEq/gr)
Mean±SD
MAX.
MIN.
NO (%)
Mean±SD
MAX.
MIN.
NO (%)
2.11±0.08
3.8
1.2
9 (27.27)
3.53±0.2
4.8
1.2
5 (18.52)
5 (≥standard limit)
10.75±0.11
16.8
5.8
13(39.39)
14.32±0.37
18.2
5.8
10 (37.04)
5-20
51.68±1.25
82.2
29.8
5 (15.15)
57.03±0.56
78.2
52.2
7 (25.92)
21-100
211.82±1.2
298.2
138.2
6 (18.19)
185.5±0.12
258.2
118.2
5 (18.52)
>100
33 (100)
27 (100)
Total

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220
Table 2. Acid value (AV) range in oil sample taken from restaurants and Fast food (sandwich) centers of Zanjan
Fast food (Sandwich) centers
Restaurants
Sampling
places
AV
(mg KOH/gr)
Mean±SD
MAX.
MIN.
NO (%)
Mean±SD
MAX.
MIN.
NO (%)
0.75±0.02
0.84
0.56
3 (9.1)
0.73±0.12
0.84
0.56
5 (18.52)
≥ 1(standard
limit)
2.15±0.25
5.07
1.12
24(72.72)
1.83±0.47
5.35
1.12
22 (81.48)
1-6
10.66±0.46
13.81
6.92
6 (18.18)
0
0
0 (0)
>6
33 (100)
27 (100)
Total
DISCUSSION
The results of this study showed that more than 80 % of oil
samples in point of view PV and AV had higher range than
recommended limits in national standard of Iran for PV and
AV in edible oils in restaurants and fast food (sandwich)
centers in Zanjan, Iran (Table 1 and 2). Determination of
PV is one of the best indicators to detect fat oxidation,
frequent heating and usage of oils for cooking or frying
[17]. High PV in the oil samples in present study regardless
to the oil type indicates the onset of oxidation in oils and
progress of oil deterioration and in particular long time and
high heating of used oils in restaurants and sandwich
centers [5]. There are other reasons to increase the PV in
heated and used oils which are not likely to be considered
in food centers including regarding to higiene regulations
while working with oil, cleaning surfaces in contact with
oil, proper disposing of burnt oil and low heating of used oil
for cooking or frying the foods [11, 19].
High PV was reported in many researches conducted on
heated edible oils used in restaurants and sandwich centers
throughout the world including Iran. Taghipour
Fardardekani and Taghipour (2015), Pour Mahmoudi and
colleges (2009) and Arbabi and Doris (2011) reported that
98%, 97.3% and 100 % used edible oils in restaurants and
sandwich centers of Behbahan, Yasooj and Sharekord cities
of Iran had higher PV than standard allowed limit [11,19
and 20]. In another study Rahimzadeh and colleges (2011)
reported higher PV value in 58.3% and 100% of used edible
oils in restaurants and sandwich centers of Gorgan city
from Iran [18]. Results of these studies are consistent with
our results. Freire and colleges (2013) from Brazil reported
high PV in 1.43 % of oil samples but in yilmaz and
Aydeniz study (2011) from turkey PV of the samples was
within the standard range. Results of both studies are lower
and not consistent with our results [21, 22]. PV decreases
with the continuous heating of the oil [1, 7]. In Park and
Kim (2016), Arbabi and Doris (2011), Takeoka and
colleges (1997) and Herchi and colleges (2016) studies, it
have been shown that produced peroxides due to oil heating
are unstable and were converted to other metabolites [17,
19, 23 and 24].
Oil acidity increases due to heat treatment. The main reason
for this raising is production of free fatty acids (FFAs) due
to the hydrolysis of esteric lipids in the oil (lipolysis) which
increases with heating time lapsing and frequent heating
cycles in the oil [17]. Increase in FFA content and AV due
to lipolysis caused by heating in used oils was reported in
several studies [8, 11 and 24]. Free fatty acids, especially
short chain FFAs are susceptible to oxidation and cause
unpleasant smell of the oils due to hydrolytic rancidity [2].
High levels of peroxide and acid value in used oils in
restaurants and sandwich centers can be attributed to the
frequent use of oil for cooking or frying [11]. Frequent
heating of the oil causes polymerization, oxidation and
hydrolysis reactions of the lipids and formation of various
unpleasant and toxic compounds such as acrolein,
hydroxides, ketones, hydrocarbons, polymers and aldehydes
which have harmful effects on the health of the community
and consumers of food prepared with these types of oils [8].
Their amount is affected by the frying temperature, frying
time, type of used edible oil, presence of antioxidants in the
oil, filtering, use time of the cooking oil or fat and frequent
use until disposal of oil, heating of the oil and the type of

H. Hassanzadazar et al / Journal of Chemical Health Risks 8(3) (2018) 217-222
221
fryer [4, 25]. The high degree of oxidative degradation in
the oils used in food shops and restaurants indicates the lack
of awareness or attention to the quality of the oil and non-
compliance with health principles when using oil by food
operators and low quality of the used oils. Therefore,
continuous surveillance and monitoring of restaurants and
food shops and training of Chefs, food operators in order to
apply proper methods of cooking and frying food is very
important and necessary.
CONCLUSIONS
Present investigation has shown that the PV and AV in used
edible oils of many restaurants and fast food centers were
higher than Iranian standard allowed limit which indicate an
improper use of oils in these food shops and presence toxic
compounds in used oils and foodstuffs which can threaten
food consumers' health. Therefore, given to increasing
amounts and high consumption of ready to eat (RTE) foods
particularly fried foods in today's community, it is
necessary to train food operators and notifying people to the
harmful effects of these foods on their health.
ACKNOWLEDGEMENTS
Hereby, authors thanks to the committee of student research
of Zanjan University of Medical Sciences for financial and
moral support of present study (Grant No. A-11-940-10).
Conflicts of interest
The authors declare that there is no conflict of interest.
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