molecules

Article
Bioactive β-Carbolines Harman and Norharman in Sesame
Seed Oils in China
Wei Liu 1, * , Zhaoyu Yang 1 , Lili Shi 1 and Yun Li 2, *

1 College of Food Science and Technology, Henan University of Technology, Lianhua Street,
Zhengzhou 450001, China; 201892085@stu.haut.edu.cn (Z.Y.); shililislla@163.com (L.S.)
2 Key Laboratory of Agro-Products Safety & Quality of the Ministry of Agriculture, Institute of Quality
Standards & Testing Technology for Agro-products, Chinese Academy of Agricultural Sciences,
No. 12, Zhongguancun South Street, Beijing 100081, China
* Correspondence: liuwei307@hotmail.com (W.L.); liyun01@caas.cn (Y.L.); Tel.: +86-371-6775-8022 (W.L.)

Abstract: The β-carbolines in our diet, mainly including harman and norharman, are a group of
biologically active, naturally occurring plant-derived alkaloids. Fragrant sesame seed oil is one
of the most popular flavor edible oils in China. Considering that sesame seeds are roasted at
200–240 ◦ C during the processing of flavor sesame seed oils, it is meaningful to investigate the
levels of β-carboline compounds in various sesame seed oils. In this work, the levels of β-carbolines
(harman and norharman) in different types of sesame seed oils in China (e.g., pressed fragrant sesame
oil, ground fragrant sesame oil) have been determined systematically. The results showed that the
levels of total β-carbolines in pressed fragrant sesame oils (700.5~2423.2 µg/kg) were higher than that
in ground fragrant sesame oils (660.4~1171.7 µg/kg). Roasting sesame seeds at high temperatures
(200–240 ◦ C) led to higher levels of β-carbolines (660~2400 µg/kg) in fragrant sesame seed oils. In
addition, the loss of tryptophan might be attributed to the formation of β-carbolines in sesame seeds




during the roasting process. In general, fragrant sesame seed oils (pressed fragrant sesame oils,

 ground fragrant sesame oils) contain higher levels of β-carbolines due to the formation of harman
Citation: Liu, W.; Yang, Z.; Shi, L.; Li, and norharman during the roasting sesame seed process.
Y. Bioactive β-Carbolines Harman
and Norharman in Sesame Seed Oils Keywords: β-carbolines; harman; norharman; sesame seed oil; roasting
in China. Molecules 2022, 27, 402.
https://doi.org/10.3390/
molecules27020402

Academic Editor: Magdalena 1. Introduction

Rudzińska β-Carbolines, mainly including harman and norharman, are a group of naturally
Received: 1 December 2021
occurring, plant-derived alkaloids that are biologically active in our diets [1–3]. Harman
Accepted: 5 January 2022
(H) and norharman (NH) are also considered as the non-polar heterocyclic aromatic amines
Published: 9 January 2022
(HAAs), generated during the treatment of protein-rich foods (e.g., meat) at high temper-
ature through pyrolysis of proteins and amino acids [4]. Many studies have disclosed a
Publisher’s Note: MDPI stays neutral
possible correlation between enhanced cancer risk and heterocyclic aromatic amines in-
with regard to jurisdictional claims in
take [5,6]. In addition, β-carboline compounds harman and norharman exhibit neuroactive
published maps and institutional affil-
activity in the human body [1,2].
iations.
In the past decades, harman and norharman have been detected in many processed
and stored foods, including cookies, maize, soy, coffee and even fermented alcoholic
beverages [2,7–9]. As a popular beverage, coffee, including brewed coffee and roasted
Copyright: © 2022 by the authors.
coffee beans, has relatively high concentrations of β-carbolines [2]. For example, in coffee
Licensee MDPI, Basel, Switzerland. grounds and instant coffee, the levels of norharman and harman have been determined
This article is an open access article to be 0.09–9.34 µg/g and 0.04–1.41 µg/kg, respectively [7]. Many studies have shown
distributed under the terms and that these β-carbolines (harman and norharman) were found in coffee and were inhibitors
conditions of the Creative Commons of monoamines oxidase (MAO), and that coffee consumption has been correlated with a
Attribution (CC BY) license (https:// lower incidence of Parkinson’s disease (PD) [1,2]. Therefore, coffee is recommended as
creativecommons.org/licenses/by/ a healthy drink in many countries. In fact, cigarette smoke (mainstream and sidestream
4.0/). brands of cigarettes) also contains a high concentration of β-carbolines (8990 ng/cigarette

Molecules 2022, 27, 402. https://doi.org/10.3390/molecules27020402 https://www.mdpi.com/journal/molecules

Molecules 2022, 27, 402 2 of 11

for norharman and 3000 ng/cigarette for harman) [8]. However, cigarette smoke is hard to
be recommended.
Edible oils, especially vegetable oils, are one of the most important food ingredients
in daily life. The average consumption of edible oil is around 28 kg per year in China.
However, less attention has been paid to the levels of harman and norharman in edible
vegetable oils. Indeed, edible vegetable oils, including soybean oil, palm oil, canola
oil, sunflower oil, rapeseed oil and peanut oil, are produced through chemical refining
(e.g., soybean oil) or pressing (e.g., palm oil) [10]. Thus, a very low level of β-carboline
compounds (harman and norharman) is detected in these kinds of edible oils [11]. In
China, flavor vegetable oils (e.g., sesame oil and peanut oil) are very popular due to their
special flavor. For instance, when peanut seeds or sesame seeds are roasted at 140–220 ◦ C
for 30–60 min before pressing, some special flavor compounds will be produced [12,13].
Thus, the oil seeds, such as sesame seeds, will generate heterocyclic aromatic amines (e.g.,
harman and norharman) at heating temperature >100 ◦ C. However, limited reports have
been disclosed on the level of β-carboline compounds (harman and norharman) in edible
oils, especially in flavor vegetable oils (e.g., sesame seed oils) [14].
Sesame seed oil (so called sesame oil) is one of the most popular flavor oils in China;
about 400,000 tons of flavor sesame oil are consumed in China every year. Considering
the processing of flavor sesame oil (roasting the sesame seed at 200–240 ◦ C) and bioac-
tivity of β-carbolines (harman and norharman), it is meaningful to investigate the level
of β-carboline compounds in sesame oils, including pressed fragrant sesame oil, ground
fragrant sesame oil and cold-pressed sesame oil. In this work, the level of β-carbolines
(harman and norharman) in different sesame seed oils in China has been investigated,
and the effect of different processing methods on the levels of harman and norharman in
sesame seed oils has been discussed. The effects of roasting temperature and time on the
levels of β-carboline compounds (harman and norharman) in sesame seed oils have been
investigated as well.

2. Results and Discussion

2.1. Analysis of β-Carbolines in Fragrant Sesame Seed Oils
Based on sesame seed oil processing methods, sesame seed oils in China can be divided
into four types, including: (1) pressed fragrant sesame seed oil, (2) ground fragrant sesame
seed oil, (3) cold-pressed sesame seed oil and (4) refined sesame seed oil [15,16]. These
types of sesame seed oils, mainly pressed fragrant sesame oil and ground fragrant sesame
oil, have different aroma flavors based on the different processing methods. Therefore,
different commercial sesame seed oil samples (16 samples from different brands) were
purchased from supermarkets in China.
The contents of β-carbolines (harman and norharman) in a batch of different pressed
fragrant sesame oils (seven samples) were determined (Figure 1). The results showed
that the contents of harman ranged from 254.0 µg/kg to 1197.7 µg/kg and the contents
of norharman ranged from 403.6 µg/kg to 1230.7 µg/kg. The total β-carbolines (harman
and norharman) ranged from 700.5 µg/kg to 2423.2 µg/kg. Notably, the contents of
norharman were higher than the contents of harman in the pressed fragrant sesame oils
in most cases.
The contents of β-carbolines (harman and norharman) in a batch of different ground
fragrant sesame seed oils (seven samples) were determined (Figure 2). The results showed
that the contents of harman ranged from 122.5 µg/kg to 444.9 µg/kg, the contents of
norharman ranged from 422.3 µg/kg to 726.8 µg/kg, and the total β-carbolines (harman
and norharman) ranged from 660.4 µg/kg to 1171.7 µg/kg in ground fragrant sesame seed
oils. In addition, the contents of norharman were much higher than that of harman in
ground fragrant sesame seed oils.
 2200 b b
2000

Content (μg/kg)
c
1800
Molecules 2022, 27, x FOR PEER REVIEW
1600
1400 d
Molecules 2022, 27, 402 a a a a 3 of 11
1200 b
1000 b b
800 e c c
f d
2800 d
600 Harman
2600 e e Norharman
400 f a
2400 Total β-carbolines
200
2200 b b
0
2000 1 2 3 4 5 6 7

Content (μg/kg)
c
1800 Pressed fragrant sesame seed oils
1600
1400 1. The contents ofd harman and norharman in pressed fragrant sesame
Figure
a a a a
1200
superscript letters indicate a significant
b difference at p-value < 0.05.
1000 b b
800 e c c
f
600
The contents d ofd β-carbolines (harman and norharman) in a batch o
fragrant e
400 e sesame f
seed oils (seven samples) were determined (Figur
200
showed that the contents of harman ranged from 122.5 μg/kg to 444.9 μ
0
of norharman 1 ranged
2 3 from 4422.3 μg/kg5 6to 726.87 μg/kg, and the total β-ca
and norharman) Pressed fragrant
ranged fromsesame
660.4seedμg/kg
oils to 1171.7 μg/kg in ground
seed1. oils. In addition, thenorharman
contents of norharman were much higher tha
FigureThe
Figure 1. contents
The contents
of harmanof andharman and norharman
in pressed fragrant in pressed
sesame fragrant
seed oils. Differentsesame
in ground
superscript lettersfragrant
superscript sesame
indicate a significant
letters indicate seed oils.
adifference at p-value < 0.05.
significant difference at p-value < 0.05.
1300
Harman
1200The
contents
Norharman
of β-carbolines (harman and norharman)
a in a batch o
fragrant
1100 sesame seed oils (seven samples) were determined (Figur
Total β-carbolines
showed
1000 that the contents of harman ranged b from 122.5 μg/kg to 444.9 μ
900
of norharman ranged from 422.3 c
μg/kg to 726.8 μg/kg, and the total β-ca
Content (μg/kg)

d d
800
and norharman)e ranged from 660.4 μg/kg toa 1171.7 μg/kg in ground
700 e
seed
600
oils. In addition,c the contents of norharman
b were much higher th
c c c
in ground
500 fragrant sesame seed oils. a
d
400 b
1300 c
300 de
Harman d
e a
1200 Norharman
200
f Total β-carbolines
1100
100
1000 b
0
900 1 2 3 4 5 c 6 7
Content (μg/kg)

d d
800 Ground fragrant sesame seed oils a
700 e e
Figure
Figure 2. contents
2. The The contents
of harmanof harman
and norharmanand in ground bfragrant in
norharman ground
sesame fragrant
seed oils. Differentsesame
600 c
c indicate a significant
superscript letters c
difference at cp-value < 0.05.
superscript
500
letters indicate a significant difference at p-value < 0.05.
d a
2.2. Analysis
400 of β-Carbolines in Cold-Pressed Sesame SeedbOils
c
2.2.Cold-pressed
Analysis of
300 de β-Carbolines
sesame d inproduced
seed oils are
e
Cold-Pressed
withoutSesame Seed
sesame seed Oils pretreat-
roasting
ment (at higher temperature) before the pressing process. Limited commercial resources
200
could beCold-pressed
f
found in China duesesame seed In
to its non-flavor. oils
fact,are produced
cold-pressed sesamewithout
seed oils cansesame
be s
100
used as a good cooking
treatment oil for temperature)
(at higher its non-flavor. before the pressing process. Limite
0 contents of harman and norharman in two cold-pressed sesame seed oil samples
The
sources
were could
1
also determined be
2 found
(Figure
3 in China
3). The
4 due
5
results showed to 6very
that its non-flavor.
low levels of theIn
7 fact, cold-pre
β-carboline
oils can (harman
compounds be used Ground
and fragrant
asnorharman)
a good sesame
cooking
were seed
oil
detected, oilsitsfrom
for
ranging non-flavor.
8.0 µg/kg to 60.0 µg/kg.
The contents
The of harman
contents ranged from
of harman 1.8 µg/kg
andand to 22.1
norharmanµg/kg, and the contents of norhar-sesam
Figure 2. The contents of harman norharmaninintwo cold-pressed
ground
man ranged from 6.2 µg/kg to 37.9 µg/kg. Moreover, one refined sesame seed oil sample
fragrant sesame
were
was alsoinletters
superscript
analyzed, determined
which aindicate
trace levela(Figure
the total3).
ofsignificant The results
difference
β-carbolines showed
at p-value
(harman and that
< 0.05.
norharman) wasvery l
β-carboline compounds (harman and norharman) were detected, rangin
2.2.60.0
to Analysis of The
μg/kg. β-Carbolines
contentsinofCold-Pressed Sesame
harman ranged Seed
from 1.8Oils
μg/kg to 22.1 μg
tentsCold-pressed
of norharmansesame
ranged seed
from oils
6.2 μg/kg to 37.9 μg/kg.
are produced withoutMoreover,
sesame ons
Molecules 2022, 27, x FOR PEER REVIEW
Molecules 2022, 27, x FOR PEER REVIEW
Molecules 2022, 27, 402 4 of 11
4 o

detected (0.8 µg/kg). Indeed, chemical refining for vegetable oils (e.g., soybean oil) will
(e.g.,
(e.g.,
decrease soybean
soybean
most ofoil) oil)
thewill
minorwill decrease
decrease ofmost
mostsuch
components, the offatty
minor
as free the minor
components,
acids, components,
vitamin such suchaca
as free fatty
E, phytosterols
vitamin
and
vitamin E, phytosterols
otherE,small molecular and
phytosterols andsmall
compounds
other other
[17–19]. small molecular
molecular compounds compounds
[17–19]. [17–19].
128128
HarmanHarman
64 Norharman a
64 Norharman a
Total β-carbolines a
32 Total β-carbolines a
a
32 a
16
Content (μg/kg)

16 b
b
Content (μg/kg)

8
b
8 b
4
b
2 4
b
1 2 c
c
0.5
1 b c
0.25 c
0.5
0.125 b
0.25 Cold-pressed 1 Cold-pressed 2 Refined
Cold-pressed and refined sesame seed oil samples
0.125
Figure 3. TheCold-pressed
contents of1 harman and norharman
Cold-pressed 2 in Refined
cold-pressed and refined sesame oils. Differ
superscriptCold-pressed and
letters indicate refined sesame
a significant seedatoil
difference samples
p-value < 0.05.

Figure 3. The contents of harman and norharman in cold-pressed and refined sesame oils. Different
Figure 3. Theofcontents
2.3. Comparison Fragrantof harman
and and norharman
Cold-Pressed Sesame Seedin cold-pressed and refined se
Oils
superscript letters indicate a significant difference at p-value < 0.05.
superscript letters indicate a significant difference at p-value < 0.05.
Based on the above results, it can be concluded that the contents of norharman (
2.3. Comparison of Fragrant and Cold-Pressed Sesame Seed Oils
μg/kg–1230.7 μg/kg) were higher than the contents of harman (1.8 μg/kg–1197.7 μg/
allBased
in2.3. testedon the above
Comparisonsesameofseed results, it and
Fragrant can be
oil samples concluded that
Cold-Pressed
(see Figures Sesamethe contents
1–3). TheSeed of norharman
Oils
level of total β-carbol
(6.2 µg/kg–1230.7 µg/kg) were higher than the contents of harman (1.8 µg/kg–1197.7 µg/kg)
compounds Based
in all tested (harman
sesame theand
on seed above
oil norharman)
samples results, in
(see Figuresit sesame
can
1–3).be Theseed
leveloil
concluded samples
of total that followed com- the ord
the contents
β-carboline o
pressed
pounds fragrantand
(harman sesame seed oil
norharman) in > ground
sesame seed fragrant
oil samples sesame
followedseed
the oil > cold-pressed
order: pressed se
μg/kg–1230.7 μg/kg) were higher than the contents of harman (1.8 μg/
me seed sesame
fragrant oil > refined
seed oil sesame
> groundseed oil. sesame
fragrant In fact,seed
oil oil
color is an important
> cold-pressed sesameindicator
seed of
in all tested sesame
oil > refinedmethodologies.
processing sesame seed oil. In seed
It fact,
wasoil
oil samples
color is an
observed
(see
important
that roasting
Figures
indicator 1–3).
sesameofseeds
The
oil processing level
at higher temp
of
compounds It (harman
was observed and
that norharman)
roasting sesame in
seeds sesame
atures led to a brown color of fragrant sesame seed oils (pressed fragrantled
methodologies. at higher seed oil
temperatures samples
to a seed
sesame fol
brown color of fragrant sesame seed oils (pressed fragrant sesame seed oils and ground
pressed
and groundfragrant sesameseed
fragrant sesame seed oilcompared
oils) > ground withfragrant sesame
cold-pressed seedseed
sesame oil >oils
c
fragrant sesame seed oils) compared with cold-pressed sesame seed oils or refined sesame
refined
meoils
seed sesame
seed
(Figure seed
oil4). oils (Figure
> Notably,
refined sesame
other 4). Notably,
seed
heterocyclic other
oil.
aromatic In heterocyclic
fact,(HAAs)
amines aromatic
oil color
were anamines
is detected
not (HA
importan
were
in thenot
processing detected
above sesame in theoilabove
methodologies.
seed samples sesame
It was
(Table seed oil samples
observed
1, Figures S1 andthat (Table
S2). 1, Figures
roasting S1 and
sesame S2).
seeds
atures led to a brown color of fragrant sesame seed oils (pressed fragran
and ground fragrant sesame seed oils) compared with cold-pressed se
refined sesame seed oils (Figure 4). Notably, other heterocyclic aromati
were not detected in the above sesame seed oil samples (Table 1, Figure

Figure 4. The colors of different sesame seed oil samples in this work.
Figure 4. The colors of different sesame seed oil samples in this work.

Table 1. The contents of 14 HAAs were determined in different sesame seed oils (μg/kg) a.

Pressed Fragrant Sesame Ground Fragrant Sesame Cold-Pressed Sesame

Molecules 2022, 27, 402 5 of 11

Table 1. The contents of 14 HAAs were determined in different sesame seed oils (µg/kg) a .

Pressed Fragrant Ground Fragrant Cold-Pressed

Sesame Sesame Sesame
HAA (µg/kg)
Seed Oils Seed Oils Seed Oils
(7 Samples) (7 Samples) (2 Samples)
AαC ND b ND ND
MeAαC ND ND ND
Trp-P-1 ND ND ND
DMIP ND ND ND
Glu-P-2 ND ND ND
MeIQ ND ND ND
MeIQx ND ND ND
IQ ND ND ND
PhIP ND ND ND
4,8-DiMeIQx ND ND ND
7,8-DiMeIQx ND ND ND
Harman 254.0–1197.7 122.5–444.9 1.8–22.1
Norharman 403.6–1230.7 422.3–726.8 6.2–37.9
Trp-P-2 ND ND ND
a Not detected (ND); b Note: heterocyclic aromatic amines (HAAs) were detected by LC-MS.

Indeed, roasting of sesame seeds at 200–240 ◦ C for 30–60 min is required at the first
stage of pressed fragrant sesame seed oil and ground fragrant sesame seed oil processing
(Figure 5) [20,21], which will lead to the production of possible heterocyclic aromatic amines
(e.g., harman and norharman) due to pyrolysis of amino acids or proteins at higher temper-
ature (like other protein-rich foods). For the processing of ground fragrant sesame seed oil
(Figure 5), unit operations slurrying and agitating with hot water (90–95 ◦ C) would remove
some β-carboline compounds (harman and norharman) from the sesame seed oil phase [22].
Thus, the processing of traditional Chinese ground fragrant sesame seed oil is called aqueous
extraction for sesame seed oil [23,24]. Therefore, it was found that the levels of β-carboline
compounds (harman and norharman) in ground fragrant sesame seed oils were lower than
the levels of β-carbolines (harman and norharman) in pressed fragrant sesame seed oils (see
Figures 1 and 2). Compared with pressed fragrant sesame seed oil and ground fragrant
sesame seed oil, cold-pressed sesame seed oil only requires drying the sesame seed at mild
heating temperature (<80 ◦ C) before the sesame seed pressing process [16]. Notably, cold-
pressed sesame seed oils do not belong to the flavor edible oils (e.g., fragrant sesame seed oils).
For refined sesame seed oil, conventional refining, including degumming, deacidification,
bleaching and deodorization, will decrease most of the lipid content (e.g., free fatty acids,
vitamin E, phytosterols) and small molecular compounds (e.g., nonpolar heterocyclic aromatic
amines harman and norharman). Thus, the levels of harman and norharman were as low as
0.8 µg/kg in the refined sesame seed oil sample (see Figure 3).

2.4. Effect of Sesame Seed Roasting Process on the Level of β-Carbolines

To investigate the effect of sesame seed roasting temperature on the formation of
β-carboline compounds (harman and norharman) in sesame seed oils, a model roasting
process was conducted at different roasting temperatures (200 ◦ C, 220 ◦ C, 240 ◦ C), and the
results were summarized in Figure 6. The results demonstrated that when roasting sesame
seeds at 200 ◦ C, the total β-carboline compounds (harman and norharman) in sesame seed oil
increased from 32.2 µg/kg to 260.0 µg/kg with the roasting time prolonging from 10 min to
30 min (Figure 6A). When sesame seeds were roasted at 220 ◦ C, the total β-carboline com-
pounds (harman and norharman) in sesame seed oil increased rapidly from 213.0 µg/kg to
799.8 µg/kg with roasting time increasing from 10 min to 30 min (Figure 6B). By increasing the
roasting temperature of sesame seeds to 240 ◦ C, the contents of total β-carboline compounds
(harman and norharman) in sesame seed oil rose quickly to 618.4 µg/kg in 5 min, and the
contents of harman and norharman reached 1239.7 µg/kg in 20 min (Figure 6C).
 sesame seed pressing process [16]. Notably, cold-pressed sesame seed oils do not belong
to the flavor edible oils (e.g., fragrant sesame seed oils). For refined sesame seed oil,
conventional refining, including degumming, deacidification, bleaching and deodoriza-
tion, will decrease most of the lipid content (e.g., free fatty acids, vitamin E, phytosterols)
Molecules 2022, 27, x FOR PEER REVIEW 6 of 11
and small molecular compounds (e.g., nonpolar heterocyclic aromatic amines harman
Molecules 2022, 27, 402 6 of 11
and norharman). Thus, the levels of harman and norharman were as low as 0.8 μg/kg in
the refined sesame seed oil sample (see Figure 3).
2.4. Effect of Sesame Seed Roasting Process on the Level of β-Carbolines
To investigate the effect of sesame seed roasting temperature on the formation of
β-carboline compounds (harman and norharman) in sesame seed oils, a model roasting
process was conducted at different roasting temperatures (200 °C, 220 °C, 240 °C), and
the results were summarized in Figure 6. The results demonstrated that when roasting
sesame seeds at 200 °C, the total β-carboline compounds (harman and norharman) in
sesame seed oil increased from 32.2 μg/kg to 260.0 μg/kg with the roasting time pro-
longing from 10 min to 30 min (Figure 6A). When sesame seeds were roasted at 220 °C,
the total β-carboline compounds (harman and norharman) in sesame seed oil increased
rapidly from 213.0 μg/kg to 799.8 μg/kg with roasting time increasing from 10 min to 30
min (Figure 6B). By increasing the roasting temperature of sesame seeds to 240 °C, the
contents of total β-carboline compounds (harman and norharman) in sesame seed oil rose
quickly to 618.4 μg/kg in 5 min, and the contents of harman and norharman reached
1239.7 μg/kg
Figure 5.
Figure 5. in 20 minprocedure
The processing (Figure of
6C).
different sesame seed oils.
oils.

Molecules 2022, 26, x. https://doi.org/10.3390/xxxxx www.mdpi.com/journal/molecules

6. The
Figure 6. The contents
contentsofofharman
harman(H)(H)andandnorharman
norharman (NH) of sesame
(NH) of sesameseed oilsoils
seed (SSO) by roasting
(SSO) by roasting
sesame seeds
seeds at 200◦°C
at200 (A),the
C (A), thecontents
contentsofofHH and
and NHNHof of
SSOSSO
by by roasting
roasting ◦ C (B),
at 220
at 220 °C (B), the contents
the contents
of H and
and NH
NH of of SSO
SSOby
byroasting 240◦ C°C(C).
roastingatat240 (C). Different
Different superscript
superscript letters
letters indicate
indicate a significant
a significant
difference atp-value
difference at p-value<<0.05.
0.05.
Molecules 2022, 27, x FOR PEER REVIEW 7 of 11
Molecules 2022, 27, 402 7 of 11

In most cases, the levels of norharman in the total β-carbolines was higher than the
In most cases, the levels of norharman in the total β-carbolines was higher than the levels
levels of harman at different roasting temperatures (200–240 °C) (Figure 6). It was con-
of harman at different roasting temperatures (200–240 ◦ C) (Figure 6). It was concluded that the
cluded that
decreasing theofdecreasing
level level of
total β-carboline total β-carboline
compounds (harman compounds
and norharman) (harman andseed
in sesame norhar-
oils
man) in sesame seed oils roasted at different temperatures ◦ followed
◦
roasted at different temperatures followed the order: 240 C > 220 C > 200 C, suggestingthe order:
◦ 240 °C >
220 °C
that > 200 °C,
increasing suggesting
roasting that increasing
temperature and timeroasting
indeedtemperature and time
led to increasing indeed
levels led to
of harman
increasing
and norharman. levels of harman and norharman.
Moreover,ititwas
Moreover, wasobserved
observedthat
that the
the sequence
sequence of the
of the oil oil color
color of different
of different sesame
sesame seedseed
oils
after roasting at different temperatures followed the same order: 240 C > 220 C >220
oils after roasting at different temperatures followed the same order:
◦ 240 °C
◦ > 200°C >
◦ C,
200 °C, and prolonging of roasting time was attributed to the color-deepening
and prolonging of roasting time was attributed to the color-deepening of sesame seed of sesame
seed(Figure
oils oils (Figure
7). The7).above
The above
resultsresults suggested
suggested that sesame
that sesame seed
seed oil oil would
color color would be a
be a good
good indicator of the roasting degree of
indicator of the roasting degree of sesame seeds. sesame seeds.

Figure 7.
Figure 7. The
The color
color of
of sesame
sesame seed
seed oils
oils through
through roasting
roastingsesame
sesameseeds
seedsat
atdifferent
differenttemperatures.
temperatures.

In
In addition,
addition,the fatty
the fattyacid compositions
acid compositions of sesame seed oil
of sesame at different
seed roastingroasting
oil at different temper-
atures ◦
(200–240(200–240
C) were °C)determined (Table 2). The sesame seedsesame
oil contained palmitic acid
temperatures were determined (Table 2). The seed oil contained
(C16:0, 9.68%), stearic acid (C18:0, 6.09%), oleic acid (C18:1, 42.42%) and
palmitic acid (C16:0, 9.68%), stearic acid (C18:0, 6.09%), oleic acid (C18:1, 42.42%) and linoleic acid (C18:2,
41.81%). Indeed,
linoleic acid the 41.81%).
(C18:2, content ofIndeed,
linoleicthe acid (C18:2),
content of as the main
linoleic acidpolyunsaturated fatty
(C18:2), as the main
acid in sesame seed oil,
polyunsaturated◦ fatty acid indecreased (from 41.81% to 40.96%) when the roasting
sesame seed oil, decreased (from 41.81% to 40.96%) when temperature
increased to 220 C and 240 ◦ C, which mainly led to a decrease in total unsaturated fatty
the roasting temperature increased to 220 °C and 240 °C, which mainly led to a decrease
acids (C18:1,
in total C18:2) in
unsaturated sesame
fatty acids seed
(C18:1, oils. The in
C18:2) loss of linoleic
sesame seed acid (C18:2)
oils. The lossunder roasting
of linoleic acid
conditions was attributed to the formation of carbonylic compounds,
(C18:2) under roasting conditions was attributed to the formation of carbonylic com- which would promote
the formation of β-carboline compounds (harman and norharman) [25].
pounds, which would promote the formation of β-carboline compounds (harman and
norharman) [25].
Table 2. Fatty acid compositions (%) of sesame seed oils by roasting sesame seeds at different
temperatures.
Table 2. Fatty acid compositions (%) of sesame seed oils by roasting sesame seeds at different
temperatures.
200 ◦ C 220 ◦ C 240 ◦ C
Fatty
Control
Acid 10 min 20 min 30 min 10 min 20 min 30 min 5 min 10 min 20 min
200 °C 220 °C 240 °C
Fatty Acid Control
9.68 ± 0.03 d,e 9.66 ± e c,d,e 0.03 c,d 0.02 c,d b,c ± 0.02 a 0.00 a,b 0.01 a 0.03 a
C16:0 100.02
min 9.73 ±
200.09
min 9.7430± min ± min
9.7410 ± 0.02
9.7920 min 9.9130 min 9.855±min 10 ±
9.88 min 20±min
9.92
C18:0 6.09 ± 0.01 b 6.23 ± 0.03 a 6.22 ± 0.10 a 6.26 ± 0.05 a 6.18 ± 0.03 a,bc,d 6.21 ± 0.04 a 6.23 ± 0.01 a 6.19 ± 0.03 a,ba,b 6.20 ± 0.02 a 6.24 ± 0.01 a
C16:0
ΣSFA 9.68 ±
15.77 ± 0.04
0.03
d
d,e 9.66 ± 0.02 e
15.89 ± 0.05 c,d 9.73 ± 0.09
15.95 ± 0.19 b,c
c,d,e 9.74 ± 0.03 c,d
16.00 ± 0.08 a,b,c
9.74 ± 0.02
15.93 ± 0.05 b,c,d
9.79 ± 0.02
15.99 ± 0.06 a,b,c
b,c 9.91 ± 0.02
16.14 ± 0.03 a
a 9.85 ± 0.00
16.03 ± 0.03 a,b,c
9.88 ± 0.01
16.08 ± 0.03 ab
a 9.92
16.16 ± 0.03
± 0.04 a
a

C18:0
C18:1 42.426.09 ± b0.01 b 42.60
± 0.06 6.23 ± 0.03
± 0.01 b a 6.22±±0.13
42.50 0.10b a 6.26 ± 0.02
42.58 ± 0.05b a 6.18 0.17 aa,b
42.79±±0.03 6.21±±0.09
42.84 0.04a a 6.23±±0.10
42.88 0.01a a 6.19
42.84 ± 0.02 a a,b
± 0.03 6.20 0.07 aa
42.90±±0.02 6.24
42.88 ± 0.04 a a
± 0.01
C18:2
ΣSFA 41.81 ± 0.02±a0.04 d 41.52
15.77 15.89± 0.02 b
± 0.05 41.55 ±±0.06
c,d 15.95 0.19b b,c 41.42 ±
16.00 0.08b,ca,b,c
41.28 ±
± 0.02
15.93 0.05c,db,c,d 15.99
± 0.16 41.17 ±±0.03 d,e a,b,c
0.06 40.99 ± ±
16.14 0.14 f a
0.03 41.13 ±±0.02
16.03 0.03d,e,fa,b,c 41.02 ±
16.08 0.04 e,fab
± 0.03 40.96 ±
16.16 0.04f a
± 0.02
ΣUFA 84.23 ± 0.08 a a,b b,c 84.00 ± 0.04 b,c,d,e
84.07 ± 0.34 b,c 84.01 ± 0.12 b,c,d a 83.87 ± 0.24 d,e a 83.97 ± 0.03 b,c,d,ea 83.92 ± 0.10 c,d,e 83.84 ± 0.05 e
C18:1 b84.11 ± 0.03
42.42 ± 0.06 42.60 ± 0.01 b 84.05 ± 0.19
42.50 ± 0.13 42.58 ± 0.02 b
b 42.79 ± 0.17 a 42.84 ± 0.09 42.88 ± 0.10 42.84 ± 0.02 42.90 ± 0.07 a 42.88 ± 0.04 a
C18:2 Note:
41.81 ± 0.02 a 41.52 ± 0.02 b 41.55 SFA
± 0.06 b and
41.42UFA
± 0.02are
b,c the abbreviations
41.28 ± 0.16 c,d of saturated
41.17 ± 0.03 d,e fatty40.99 ±acids
0.14 f and unsaturated
41.13 ± 0.02 d,e,f 41.02 fatty acids,
± 0.04 e,f respectively.
40.96 ± 0.02 f
ΣUFA Different
84.23 ± 0.08 a 84.11 ± 0.03 a,b 84.05 superscript
± 0.19 b,c 84.00 ± 0.04letters
b,c,d,e indicate
84.07 ± 0.34a significant
b,c difference
84.01 ± 0.12 at ±p-value
b,c,d 83.87 0.24 d,e < 0.05.
83.97 ± 0.03 b,c,d,e 83.92 ± 0.10 c,d,e 83.84 ± 0.05 e
Note: SFA and UFA are the abbreviations of saturated fatty acids and unsaturated fatty acids, respectively. Different
superscript letters indicate a significant differencemechanism
The formation at p-value < 0.05.
of β-carboline compounds (harman and norharman) in
sesame seed oil was also discussed. In fact, harman and norharman, as non-polar het-
The aromatic
erocyclic formationamines,
mechanism of β-carboline
are usually assignedcompounds
as pyrolysis(harman
productsand norharman)
of amino acids atin
sesame seed oil was also ◦
discussed. In fact, harman and norharman, as
higher temperatures (>150 C) [26], while tryptophan is considered as the main precursor non-polar heter-
ocyclic
of aromatic
β-carboline amines, are
compounds [9].usually assigned
Tryptophan mayasslowly
pyrolysis products
react of amino
with released acids at
aldehydes,
higher temperatures
producing (>150 °C) [26], while tryptophan
tetrahydro-β-carboline-3-carboxylic is considered
acid, which is oxidized astothe main
give precursor
β-carbolines
of β-carboline
(harman compounds
and norharman) [9]. Tryptophan
[27,28]. Some studiesmay haveslowly react with
demonstrated thatreleased aldehydes,
the total amino acid
producing17 amino
(detected tetrahydro-β-carboline-3-carboxylic
acids) content decreased with acid, increasedwhich is oxidized
roasting ◦C
to give
time at 160–200
β-carbolines
during (harman
the roasting and norharman)
treatment of sesame[27,28]. SomeHowever,
seeds [29]. studies have demonstrated
the change that the
of tryptophan
totalnot
was amino acidin(detected
included 17 Therefore,
their study. amino acids) contentofdecreased
the content tryptophan with
wasincreased
determined roasting
when
time at seeds
sesame 160–200
were°Croasted
duringatthe
200–240 ◦
roasting treatment
C (Figure of sesame
8). The seeds [29].
results showed thatHowever, the
the free tryp-
tophan content decreased rapidly from original 547.6 mg/kg to 294.4 mg/kg after roasting

Molecules 2022, 26, x. https://doi.org/10.3390/xxxxx www.mdpi.com/journal/molecules

 change of tryptophan was not included in their study. Therefore, the content of try
phan was determined when sesame seeds were roasted at 200–240 °C (Figure 8).
Molecules 2022, 27, 402 results showed that the free tryptophan content decreased rapidly from 8 oforiginal
11 5
mg/kg to 294.4 mg/kg after roasting at 200 °C for 10 min, and it reduced rapidly to
mg/kg with roasting time increasing to 30 min. When roasting sesame seeds at 220 °C
at 200 ◦ C for 10content
tryptophan min, anddecreased rapidlytoto31.2
it reduced rapidly 30.3 mg/kg
mg/kg with(roasting for increasing
roasting time 10 min) andto 5.7 m
30 min. When roasting sesame seeds at 220 ◦ C, the tryptophan content decreased rapidly
(roasting for 30 min). At the same time, the contents of other amino acids indeed
to 30.3 mg/kg
creased with(roasting for 10roasting
increasing min) andtime,
5.7 mg/kg
which (roasting for 30 min).to
was attributed Atthe
the formation
same time, of com
the contents of other amino acids indeed decreased with increasing roasting time, which
cated Maillard reaction products [4].
was attributed to the formation of complicated Maillard reaction products [4].
600
a

500
Tryptophan (mg/kg)

400

b
300

200

100
c c c c c c
d d
0
Control 10' 20' 30' 10' 20' 30' 5' 10' 20'
200℃ 220℃ 240℃
Roasting temperature and time

Figure8.8.The
Figure content
The of free
content oftryptophan in sesameinseeds
free tryptophan at different
sesame seedsroasting temperatures.
at different roastingDifferent
temperatures.
superscript letters indicate a significant difference at p-value < 0.05.
ferent superscript letters indicate a significant difference at p-value < 0.05.
3. Materials and Methods
3. Materials
3.1. Materials and Methods
3.1. Commercial
Materials sesame seed oils, including pressed fragrant sesame seed oils (n = 7) and
ground fragrant sesame
Commercial seed seed
sesame oils (noils,
= 7),including
were purchased from
pressed a local supermarket
fragrant sesame seed in oils (n
China. Sesame seeds were purchased from a local supermarket in China. Acetonitrile
and ground fragrant sesame seed oils (n = 7), were purchased from a local supermark
(HPLC grade) was purchased from Thermo Fisher Scientific (Shanghai, China). Ammonium
China. Sesame
hydroxide seeds were
and hydrochloric acidpurchased
(HPLC grade) from a local
were supermarket
obtained from Kemiou inChemical
China. Aceton
(HPLC Co.
Reagent grade)
Ltd.was purchased
(Tianjin, China).from
MethylThermo Fisher
alcohol, aceticScientific (Shanghai,
acid and n-hexane China).
were of Am
nium hydroxide and hydrochloric acid (HPLC grade) were obtained from Kem
HPLC grade, and other chemicals were of analytical reagent grade. Oasis MCX solid-phase
extraction
Chemicalcartridge
Reagent(150Co.mg, 6 mL)
Ltd. was purchased
(Tianjin, China).from Watersalcohol,
Methyl (Milford,acetic
PA, USA).
acidThe
and n-he
water used was Wahaha purified water purchased from a local supermarket. The standards
were of HPLC grade, and other chemicals were of analytical reagent grade. Oasis M
AαC, MeAαC, DMIP, Trp-P-1, Trp-P-2, Glu-P-2, MeIQ, MeIQx, IQ, PhIP, 4,8-DiMeIQx and
solid-phase extraction cartridge (150 mg, 6 mL) was purchased from Waters (Milf
7,8-DiMeIQx were purchased from Toronto Research Chemicals (Toronto, ON, Canada).
PA, USA).
Harman The water used was Wahaha
(1-methyl-9H-pyrido[3,4-b]indole), purified
norharman water purchased and
(9H-pyrido[3,4-b]indole) from a local su
4,7,8-
market. The
TriMeIQx were standards
purchased fromAαC,
Alta MeAαC,
scientific DMIP,
(Tianjin,Trp-P-1,
China). Trp-P-2, Glu-P-2, MeIQ, Me
IQ, PhIP, 4,8-DiMeIQx and 7,8-DiMeIQx were purchased from Toronto Research Ch
3.2. Methods
icals (Toronto, ON, Canada). Harman (1-methyl-9H-pyrido[3,4-b]indole), norhar
3.2.1. Model Roasting Process for Sesame Seeds and Oil Extraction
(9H-pyrido[3,4-b]indole) and 4,7,8-TriMeIQx were purchased from Alta scientific (T
Sesame seeds (about 1000 g) were roasted using an automatic electric heater (Korea
jin, China). ◦ ◦ ◦
Hanna Co., Seoul, Korea) at different temperatures (200 C, 220 C, 240 C) for the duration
of 5 min, 10 min, 20 min and 30 min at each temperature with constant stirring. The roasted
3.2. Methods
sesame seeds (100 g) were crushed with a mortar and then extracted with n-hexane three
times. The
3.2.1. Modelobtained mixture
Roasting (oil–hexane)
Process was then
for Sesame rotationally
Seeds and Oil vaporized and blown with
Extraction
nitrogen to remove the remaining n-hexane. The resulting sesame seed oil was centrifuged
Sesame
to remove seeds
impurity (about All
particles. 1000 g) were
samples wereroasted
preparedusing an automatic electric heater (K
as triplicates.
Hanna Co., Seoul, Korea) at different temperatures (200 °C, 220 °C, 240 °C) for the d
3.2.2.
tion ofAnalysis
5 min,of10Fatty Acid
min, 20 Composition
min and 30ofminSesame Seedtemperature
at each Oil with constant stirring.
roasted sesame seeds (100 g) were crushed with a mortar andacid
The fatty acid composition was determined by conversion of oil to fatty methyl
then extracted
esters, prepared following the standard IUPAC method 2.301. Fatty acid compositions
n-hexane three times. The obtained mixture (oil–hexane) was then rotationally of vapor
and blown with nitrogen to remove the remaining n-hexane. The resulting sesame
Molecules 2022, 27, 402 9 of 11

sesame seed oils were analyzed by an Agilent Technologies 6890 N gas chromatograph
(GC) equipped with a 30.0 m × 250 µm × 0.25 µm BPX-70 capillary column and detected
using a flame ionization detector (FID). Samples (1 µL) were injected under the following
conditions: the nitrogen flow rate was 1.0 mL/min, the oven was programmed from the
set temperature of 170 to 210 ◦ C at 2 ◦ C/min, the split ratio was 50:1, the GC injection
temperature was 250 ◦ C, and the detector temperature was 300 ◦ C.

3.2.3. Determination of Free Amino Acids in Defatted Sesame Cake

Free amino acids were analyzed by a Biochrom 30 amino acid analyzer (Biochrom Co.
Ltd., Holliston, MA, USA). The extraction and analysis method was according to Song with
modification [30]. One gram of defatted sesame cake (accurate to 0.0001 g) was weighed into
a 50 mL grinding triangle flask, and 20 mL lithium loading buffer (Biochrom Co. Ltd., USA)
was added. Ultrasonic extraction (300 W) was carried out for 30 min. After centrifugation
(10,000 rpm) and filtration, the samples were detected by an automatic analyzer.

3.2.4. Extraction, Purification and Analysis of Heterocyclic Aromatic Amines

Heterocyclic aromatic amines (HAAs) were determined by LC-MS based on the lit-
erature [31]. Oil samples (1 g) were added with 10µL 5 mg/L 4,7,8-TriMeIQx (internal
standard) and combined with 10 mL acetonitrile (containing 1% acetic acid) in a 50 mL
centrifuge tube, after which the mixture was shaken for 5 min, followed by ultrasonic ex-
traction for 10 min, and shaken vigorously for 1 min before being centrifuged at 10,000 rpm
(−4 ◦ C) for 10 min. The supernatant liquid was collected into a 50 mL centrifuge tube.
The above extraction operations with acetonitrile were repeated twice. All extracts were
collected together.
A solid phase extraction column cartridge Oasis MCX (150 mg/6 mL) was flushed
in advance with 10 mL of methanol and 10 mL 0.1 mol/L HCl–methanol mixed so-
lution (80:20, v/v). All extracts were transferred to the MCX column for enrichment
and purification. Then it was washed with 10 mL water, 10 mL methanol and 10 mL
methanol/ammonia/water (25:5:75, v/v/v) mixed solution. Finally, 10 mL methanol/ am-
monia (95:5, v/v) solution was used for elution. The eluent was collected and evaporated
to dryness under nitrogen. The residue was dissolved in 10 mL 5% formic acid/acetonitrile
(95:5, v/v) mixture and filtered through a 0.45 µm microporous filter for LC/MS analysis.
A Shimadzu LC-20ADXR system coupled with a Triple Quad 3500 mass spectrometer
(AB SCIEX, Redwood City, CA, USA) was used to analyze the HAAs of the sample extract.
Chromatographic separation was performed on an Agilent ZORBAX Eclipse XDB-C18
column (3.5 µm particle size, 150 mm × 2.1 mm i.d) maintained at 35 ◦ C. The gradient
elution was achieved with a binary mobile phase of 5% formic acid/5 mM ammonium
formate aqueous solution (A) and 5% formic acid/5mM ammonium formate methanol
solution (B) at a flow rate of 0.4 mL/min. The gradient elution program was as follows:
0–0.01 min, 5%B; 0.01–1.00 min, 5%B; 1.00–1.10 min, 5–60%B; 1.10–5.00 min, 60–80%B;
5.00–6.00 min, 80–95%B; 6.00–8.00 min, 95%B; 8.00–8.10 min, 95–5%B; 8.10–8.20 min, 5%;
8.20–10.00 min adjust mobile phase balance to initial state. The single injection volume was
set at 5 µL.
MS analysis was carried out with positive electrospray ionization (ESI+). Multiple
reaction monitoring (MRM) conditions were automatically optimized. The capillary voltage
was 5.5 kV, and the ion source temperature was 550 ◦ C. The MRM parameters for 14 HAAs
and internal standard are summarized in Table S1 (see Supplementary Materials).

3.2.5. Statistical Analysis

All experiments were carried out in triplicate, and the mean and standard deviation
(SD) for each of the determinations were calculated and reported. Figure preparation
was performed using Origin Pro software (Origin Lab Co., Northampton, MA, USA). The
differences between groups were tested by ANOVA and Duncan’s multiple range tests.
Means were compared, and they were considered significant when p < 0.05.
Molecules 2022, 27, 402 10 of 11

4. Conclusions
In this work, the levels of β-carbolines (harman and norharman) in different types
of sesame seed oils in China, including pressed fragrant sesame seed oil, ground fragrant
sesame seed oil, refined sesame seed oil and cold-pressed sesame seed oil, were investigated
systematically. The results showed that the levels of the total β-carbolines (harman and
norharman) in pressed fragrant sesame seed oils were higher than those in ground fragrant
sesame seed oils, and they were much higher than those in cold-pressed or refined sesame
seed oils. Model roasting sesame seeds at higher temperatures (200–240 ◦ C) for 5–30 min
led to higher levels of β-carbolines harman and norharman (660~2400 µg/kg) in fragrant
sesame seed oils. The loss of tryptophan might be attributed to the formation of β-carbolines
(harman and norharman) in sesame seeds during the roasting process at higher temperature.
This study will be meaningful to prove a correlation between the contents of β-carbolines in
fragrant sesame seed oils and the roasting processes of sesame seeds, and whether fragrant
sesame seed oils will be a dietary supplement of β-carbolines (harman and norharman).

Supplementary Materials: The following supporting information can be downloaded online. The
supplementary data contain the related MRM parameters for HAAs and internal standard (Table S1),
MRM chromatogram and extracted ion chromatograms (EIC) of HAAs (Figures S1 and S2).
Author Contributions: Conceptualization, W.L. and Y.L.; methodology, Z.Y.; software, Z.Y.; formal
analysis, Z.Y.; investigation, Z.Y.; data curation, Z.Y. and L.S.; writing—original draft preparation,
W.L. and Z.Y.; writing—review and editing, W.L.; supervision, W.L.; funding acquisition, W.L. and
Y.L. All authors have read and agreed to the published version of the manuscript.
Funding: This work was supported by the National Key R&D Program of China (2017YFC1600402)
and Project of Henan University of Technology Excellent Young Teachers (2014003).
Institutional Review Board Statement: Not applicable.
Informed Consent Statement: Not applicable.
Data Availability Statement: Not applicable.
Conflicts of Interest: The authors declare no conflict of interest.
Sample Availability: Samples are available from Wei Liu on valid request.

References
1. Piechowska, P.; Zawirska-Wojtasiak, R.; Mildner-Szkudlarz, S. Bioactive β-Carbolines in Food: A Review. Nutrients 2019, 11, 814.
[CrossRef] [PubMed]
2. Wojtowicz, E.; Zawirska-Wojtasiak, R.; Przygoński, K.; Mildner-Szkudlarz, S. Bioactive β-carbolines norharman and harman in
traditional and novel raw materials for chicory coffee. Food Chem. 2015, 175, 280–283. [CrossRef] [PubMed]
3. Xie, Z.; Cao, N.; Wang, C. A review on β-carboline alkaloids and their distribution in foodstuffs: A class of potential functional
components or not? Food Chem. 2021, 348, 129067. [CrossRef] [PubMed]
4. Gibis, M. Heterocyclic aromatic amines in cooked meat products: Causes, formation, occurrence, and risk assessment. Compr. Rev.
Food Sci. Food Saf. 2016, 15, 269–302. [CrossRef]
5. Sun, J.H.; Yohan, Y.; Cheorun, J.; Jong, Y.J.; Keun, T.L. Effect of Dietary Red Meat on Colorectal Cancer Risk—A Review. Compr.
Rev. Food Sci. Food Saf. 2019, 18, 1812–1824.
6. Sun, J.H.; Cheorun, J.; Yohan, Y.; Jong, Y.J.; Keun, T.L. Controversy on the correlation of red and processed meat consumption
with colorectal cancer risk: An Asian perspective. Crit. Rev. Food Sci. Nutr. 2019, 59, 3526–3537.
7. Herraiz, T. Identification and occurrence of the bioactive β-carbolinesnorharman and harman in coffee brews. Food Addit. Contam.
2002, 19, 748–754. [CrossRef]
8. Herraiz, T. Relative exposure to β-carbolinesnorharman and harman from foods and tobacco smoke. Food Addit. Contam. 2004, 21,
1041–1050. [CrossRef]
9. Nadeem, H.R.; Akhtar, S.; Ismail, T.; Sestili, P.; Lorenzo, J.M.; Ranjha, M.M.A.N.; Jooste, L.; Hano, C.; Aadil, R.M. Hetero-
cyclic Aromatic Amines in Meat: Formation, Isolation, Risk Assessment, and Inhibitory Effect of Plant Extracts. Foods 2021,
10, 1466. [CrossRef]
10. Gao, P.; Cao, Y.; Liu, R.; Jin, Q.; Wang, X. Phytochemical content, minor-constituent compositions, and antioxidant capacity of
screw-pressed walnut oil obtained from roasted kernels. Eur. J. Lipid Sci. Technol. 2019, 121, 1800292. [CrossRef]
Molecules 2022, 27, 402 11 of 11

11. Chang, C.C.; Zhang, D.; Wang, Z.; Chen, B.H. Simultaneous determination of twenty heterocyclic amines in cooking oil
using dispersive solid phase extraction (QuEChERS) and high performance liquid chromatography-electrospray-tandem mass
spectrometry. J. Chromatogr. A 2019, 1585, 82–91. [CrossRef]
12. Ahmed, I.A.M.; Uslu, N.; Ozcan, M.M.; Juhaimi, F.A.L.; Ghafoor, K.; Babiker, E.E.; Osman, M.A.; Alqah, H.A.S. Effect of
conventional oven roasting treatment on the physicochemical quality attributes of sesame seeds obtained from different locations.
Food Chem. 2021, 338, 128109. [CrossRef]
13. Zhang, D.; Li, X.; Cao, Y.; Wang, C.; Xue, Y. Effect of roasting on the chemical components of peanut oil. LWT Food Sci. Technol.
2020, 125, 109249. [CrossRef]
14. Zhang, C.X.; Xi, J.; Zhao, T.P.; Ma, Y.X.; Wang, X.D. β-carbolinesnorharman and harman in vegetable oils in China. Food Addit.
Contam. Part B Surveill. 2020, 13, 193–199. [CrossRef]
15. Wu, W.; Lv, M. Optimization of an improved aqueous method for production of high quality white sesame oil and de-oiled meal.
Grasasy Aceites 2020, 71, e349.
16. Shi, L.K.; Zheng, L.; Zhang, Y.R.; Liu, R.J.; Chang, M.; Huang, J.; Jin, Q.; Zhang, H.; Wang, X. Evaluation and Comparison of Lipid
Composition, Oxidation Stability, and Antioxidant Capacity of Sesame Oil: An Industrial-Scale Study Based on Oil Extraction
Method. Eur. J. Lipid Sci. Technol. 2018, 120, 1800158. [CrossRef]
17. Gomez-Coca, R.B.; Alassi, M.; Moreda, W.; Perez-Camino, M.D. Pyropheophytina in Soft Deodorized Olive Oils. Foods 2020,
9, 978. [CrossRef]
18. Lee, J.G.; Suh, J.H.; Yoon, H.J. The effects of extracting procedures on occurrence of polycyclic aromatic hydrocarbons in edible
oils. Food Sci. Biotechnol. 2020, 29, 1181–1186. [CrossRef] [PubMed]
19. Liu, R.J.; Liu, R.R.; Shi, L.K.; Zhang, Z.Y.; Zhang, T.; Lu, M.; Chang, M.; Jin, Q.; Wang, X. Effect of refining process on
physicochemical parameters, chemical compositions and in vitro antioxidant activities of rice bran oil. LWT Food Sci. Technol.
2019, 109, 26–32. [CrossRef]
20. Salamatullah, A.M.; Alkaltham, M.S.; Uslu, N.; Ozcan, M.M.; Hayat, K. The effects of different roasting temperatures and times on
some physicochemical properties and phenolic compounds in sesame seeds. J. Food Process. Preserv. 2021, 45, e15222. [CrossRef]
21. Zhou, Q.; Geng, F.; Deng, Q.C.; Huang, F.H.; Wang, J.Q. Dynamic analysis of polar metabolites and volatile compounds in sesame
seeds during roasting. Cereal Chem. 2019, 96, 358–369. [CrossRef]
22. Randel, G.; Balzer, M.; Grupe, S.; Drusch, S.; Kaina, B.; Platt, K.L.; Schwarz, K. Degradation of heterocyclic aromatic amines
in oil under storage and frying conditions and reduction of their mutagenic potential. Food Chem. Toxicol. 2007, 45, 2245–2253.
[CrossRef] [PubMed]
23. Geng, Q.; Chen, J.; Guo, R.; Zhang, L.; Li, Q.; Yu, X. Salt-assisted aqueous extraction combined with Span 20 allow the obtaining
of a high-quality and yield walnut oil. LWT Food Sci. Technol. 2020, 121, 108956. [CrossRef]
24. Behraad, T.; Jamshid, F.; Jafar, M.M. Enzyme-assisted aqueous extraction of oil and protein hydrolysate from sesame seed. J. Food
Meas. Charact. 2019, 13, 2118–2129.
25. Pan, T.; Wang, Z.Y.; Chen, B.H.; Hui, T.; Zhang, D.Q. Frying oils with lower levels of saturated fatty acids induce less heterocyclic
amine formation in meat floss (boiled, shredded and fried pork). Int. J. Food Sci. Technol. 2020, 55, 823–832. [CrossRef]
26. Alaejos, M.S.; Afonso, A.M. Factors That affect the content of heterocyclic aromatic amines in foods. Compr. Rev. Food Sci. Food Saf.
2011, 10, 52–108. [CrossRef]
27. Herraiz, T. Identification and occurrence of beta-carboline alkaloids in raisins and inhibition of monoamine oxidase (MAO).
J. Agric. Food Chem. 2007, 55, 8534–8540. [CrossRef]
28. Herraiz, T. Tetrahydro-beta-carboline-3-carboxylic acid compounds in fish and meat: Possible precursors of co-mutagenic
beta-carbolines norharman and harman in cooked foods. Food Addit. Contam. 2000, 17, 859–866. [CrossRef]
29. Ji, J.; Liu, Y.; Shi, L.; Wang, N.; Wang, X. Effect of roasting treatment on the chemical composition of sesame oil. LWT Food Sci.
Technol. 2019, 101, 191–200. [CrossRef]
30. Song, J.; Bi, J.; Chen, Q.; Wu, X.; Lyu, Y.; Meng, X. Assessment of sugar content, fatty acids, free amino acids, and volatile profiles
in jujube fruits at different ripening stages. Food Chem. 2018, 270, 344–352. [CrossRef] [PubMed]
31. Liu, W.; Yang, Z.; Shi, L.; Cui, Z.; Li, Y. Degradation of β-carbolines harman and norharman in edible oils during heating.
Molecules 2021, 26, 7018. [CrossRef]