Available via license: CC BY
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Food Sci Nutr. 2023;00:1–15.
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1wileyonlinelibrary.com/journal/fsn3
Received: 9 August 2023
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Revised: 26 September 2023
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Accepted: 4 October 2023
DOI: 10.1002 /fsn3. 3776
ORIGINAL ARTICLE
Microencapsulated polyphenol extracts from Georgia-grown
pomegranate peels delay lipid oxidation in salad dressing
during accelerated and ambient storage conditions
BoranYang |JinruChen | Kevin Mis Solval
This is an op en access arti cle under the ter ms of the Creative Commons Attribution License, which p ermit s use, distrib ution and repro duction in any me dium,
provide d the original wor k is properly cited.
© 2023 The Au thors . Food Sci ence & Nutr ition published by Wiley Periodic als LLC .
Depar tment of Food Science and
Technolog y, University of Ge orgia, Griffin,
Georgia, USA
Correspondence
Kevin Mis So lval, Department of Fo od
Science a nd Technology, University of
Georgia, 1109 Experiment Street , Grif fin,
GA 30223 , USA.
Email: kmissolval@uga.edu
Funding information
Agricultural Marketing Service
Abstract
Lipid oxidation is a major cause of quality deterioration in salad dressings. This study
evaluated the effect of incorporating microencapsulated polyphenol extracts via
spray dr ying from pomegranate peels (MPP) to delay lipid oxidation in Italian-style
salad dressings (ISD) during accelerated (55°C) and ambient (25°C) storage condi-
tions. ISDs, prepared at high (5000 rpm) and low (250 rpm) shear rates conditions,
were formulated with unencapsulated polyphenol extracts from pomegranate peels
(PPP), MPP, and/or grape seed extract (GSE). Lipid oxidation in ISDs was evaluated
by measuring peroxide value (PV), iodine value (IV), and TBARS, stored in accelerated
and ambient conditions for 21 days and 8 weeks, respectively. Tannis in extracts were
measured via HPLC-DAD and the total hydrolyzable tannin content of PPP and MPP
was 283.09 and 427.74 (mg/g extract), respectively. Condensed tannins were not de-
tected in PPP and MPP but were found in GSE (348.53 mg/g extract). Salad dressings
prepared at high shear rates had significantly (p < .05) higher emulsion stability than
those homogenized at low shear rates. Mixing conditions did not affect the lipid oxi-
dative stability of IDSs. Salad dressing stored under accelerated storage had higher
lipid oxidation (higher PV, lower IV, and higher TBARS) after 21 days than IDSs stored
under ambient conditions for 8 weeks. ISDs prepared with MPPP showed significantly
(p < .05) lower lipid oxidation than the other ISDs at the end of the shelf life studies.
Results from the accelerated storage suggested that incorporating MPP could have
extended the shelf life of IDSs by 20% compared to using unencapsulated polyphenol
extracts. The study demonstrated that MPP delays lipid oxidation in ISDs during stor-
age more effectively than unencapsulated extracts. MPP may serve as a natural and
effective functional food ingredient for controlling lipid oxidation in high-lipid and
acidified foods.
KEYWORDS
accelerated storage, ambient shelf life test, antioxidant, lipid oxidation, salad dressing
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YA NG et al .
1 | INTRODUCTION
Salad dressings are popular and versatile condiments enjoyed by
many people worldwide. They are often prepared by emulsifying
vegetable oils, acidifying ingredients, spices, and other additives, re-
sulting in a variety of flavors and textures and unique styles such as
Italian, Thousand Island, and French dressings (Mizani et al., 2015).
Some salad dressings adopt an oil-in-water (o/w) or water-in-oil
(w/o) emulsion structure, where tiny oil or water droplets are dis-
persed in an aqueous phase. Meanwhile, others take the form of
suspensions (Arancibia et al., 2013). The physical stability of salad
dressings, crucial for maintaining their structure over time, relies on
several factors, including interfacial composition, emulsion droplet
size, flocculation, and final phase separation (Kiokias et al., 2016;
Zhang et al., 2008). Commercially available salad dressings typically
come in two t ypes: one phase and two phase. One-phase dressings
often include emulsifiers and undergo fine homogenization with
high shear rates, resulting in a smooth and creamy consistency that
prevents phase separation. On the other hand, two-phase salad
dressings form distinct layers of oil atop the water phase (Perrechil
et al., 2010). Preparing stable and appealing salad dressings involves
careful attention to processing conditions such as shear rate, tem-
perature, and mixing time during the homogenization/mixing step.
These factors are crucial to stabilizing stable salad dressings with
desirable organoleptic properties (Bengoechea et al., 2009; Kim
et al., 2020).
According to the U.S. Food and Drug Administration (FDA),
salad dressings must contain at least 30% vegetable oil (by
weight) (Ma & Boye, 2013). The most popular vegetable oils used
in salad dressings are olive oil, peanut oil, and sunflower due to
their great flavor, unsaturated fatty acid profile, and potential
health benefits (Kaltsa et al., 2018). However, using vegetable
oils with a high content of unsaturated fatt y acids can challenge
salad dressings' shelf life stability. This is because these oils are
highly prone to lipid oxidation, which can form undesirable com-
pounds like lipid hydroperoxides, aldehydes, ketones, and lactones
(Sainsbury et al., 2016; Tseng & Zhao, 2013). According to Kiokias
et al. (2016), physicochemical properties (pH and size and electri-
cal charges of micelles), as well as processing parameters (storage
temperature, homogenization conditions, oxygen, and light levels),
may play roles in determining how well a salad dressing withstands
lipid oxidation. To address this issue, synthetic and natural anti-
oxidants are widely used in salad dressings to minimize or delay
lipid oxidation and the formation of oxidation products that may
negatively affect the taste and nutritional value of the dressings.
Natural antioxidants such as fruit polyphenols and tocopherols
are considered safe and effective alternatives to synthetic anti-
oxidants such as butylated hydroxyanisole (BHA) and tert-butyl
hydroquinone (TBHQ) (Phisut et al., 2018). Recent studies have
reported using fruit processing by-product s (peels, seeds, etc.)
to develop functional foods with antioxidant and antimicrobial
proper ties (Rosales Soto et al., 2012). This approach aligns with
the current food waste reduction and sustainability initiatives,
making it a promising direction for developing novel food ingre-
dients (Pande & Akoh, 2009; Tseng & Zhao, 2013). Exciting re-
search has shown that polyphenols obtained from pomegranate
peels offer strong antioxidant benefits (Hooks et al., 2021; Pateiro
et al., 2021; Shahkoomahally et al., 2021). However, directly
adding polyphenol-rich extracts to foods is technologically chal-
lenging due to their low stability during processing and storage
(Santos & Meireles, 2011). When polyphenol-rich extracts are di-
rectly added to foods may result in bitterness, astringency, and
unpleasant flavors. To address this, researchers have explored
novel str at egies to enh an ce the stabilit y an d co mp at ibilit y of poly-
phenol extracts in foods. Microencapsulation has emerged as a
highly effective strategy to stabilize plant-based bioactives with
antioxidant properties (Jolayemi et al., 2021).
According to Corrigan et al. (2012), accelerated shelf-life tests
(ACSL) are cost-effec tive alternatives to determine the shelf life of
foods. These tests subject foods to higher storage temperatures,
stronger ultraviolet light intensities, and/or prooxidants that ac-
celerate deterioration. In the case of salad dressings, ACSL evalu-
ations often involve exposure to temperatures between 50 and
60°C (Berton et al., 2014). Recent studies have explored incorpo-
rating phytochemicals with antioxidant properties extracted from
plant by-products to improve the oxidative stability of salad dress-
ings during storage (Jolayemi et al., 2021; Tseng & Zhao, 2013).
Nonetheless, no studies have reported the effect of shear rates and
the addition of microencapsulated pomegranate peel extrac ts (MPP)
on the oxidative stability of salad dressings. Hence, this study aimed
to evaluate the influence of MPP on the physicochemical and oxi-
dative stability of Italian-style salad dressings homogenized at dif-
ferent shear rates during ACSL and ambient shelf life evaluations
(AMSL).
2 | MATERIALSANDMETHODS
2.1 | Materials
Polyphenol-containing extract (PPP) isolated from Georgia-grown
pomegranate peels were microencapsulated by following the
method previously repor ted by our group (Yang et al., 2022). In
short, PPP was homogenized with a mixture of maltodextrin: pome-
granate peel pectin (ratio 3:1, w/w) to create PPP suspensions (core:
wall materials = 1:5, w/w). Then, the PPP suspensions were spray-
dried to produce microencapsulated MPP powders. A commercial
grape seed extract (GSE) (Grape seed extract, Zazzee, Montebello,
NY, USA) was purchased from a local store in Griffin, GA. Peanut
oil, white wine vinegar, salt, red pepper flakes, garlic powder, basil
leaves, and oregano were obtained from a local supermarket in
Griffin, GA, USA. Iodine monochloride Wijs solution, chloroform,
potassium iodide, sodium thiosulfate, starch indicator, glacial acetic
acid, iso-octane, 1, 1, 3, 3-tetraethoxtpropane, trichloroacetic acid,
and 2-thiobarbituric acid were obtained from Fisher Scientific (Fair
Lawn, NJ, USA).
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YAN G et a l.
2.2 | Characterizationofphenoliccompoundsin
PPP, MPP, and GSE
Tannins and phenolic compounds in PPP, MPP, and GSE were
quantified at the Watrelot Lab (Department of Food Science and
Human Nutrition, Iowa State University, Ames, IA, USA) as de-
scribed below.
2.2.1 | Tannin content
Tannins (hydrolyzable and condensed) were determined by high-
performance liquid chromatography coupled with a diode array
detector (HPLC-DAD) after directly injecting samples prepared in
methanol. Punicalagin (α and β) and ellagic acid content were cal-
culated using a commercial standard of punicalagin and ellagic acid,
respectively (Mathon et al., 2019).
2.2.2 | Monomeric phenolic compounds
Monomeric phenolic compounds found in PPP, MPP, and GSE were
characterized by direct injec tion of the samples prepared at 5 g/L
in 13% ethanol, 5 g/L tar taric acid, pH 3.5 by HPLC-DAD by follow-
ing the method of Ritchey and Waterhouse (1999). The amounts of
flavanols were reported as equivalent to (−)-epicatechin in mg/g of
extract. While quantities of ellagitannins were expressed as equiva-
lent to β-punicalagin in mg/g of extract.
2.3 | RheologicalpropertiesofPPPsuspensions
PPP suspensions were stirred overnight at 25°C before testing.
Shear stress sweep tests were conducted in a modular compact
rheometer (MCR92, Anton Paar, Graz, Austria) with a parallel plate
measuring geometry (25-mm diameter, part No. 790 44, Anton Paar,
Graz, Austria); using a gap of 500 μm. Then, the resultant steady
shear flow curves were analyzed at 25°C, using shear rates from 1 to
100 s−1. Shear stress (σ) and apparent viscosity (η) were measured as
a function of shear rate. Data from the flow curves were fit ted to the
Powe r law model (Equation 1) to def ine shear-effected ch ar ac teriza-
tions of the PPP suspensions.
where σ represents the shear stress (Pa), K is the consistency index
(Pa.sn),
𝛾
is the shear rate (s
−1), and n is the flow behavior index
(dimensionless).
2.4 | PreparationofItalian-stylesaladdressing
(ISD)
Fresh ISDs were prepared by mixing 50 g/100 g of peanut
oil, 30 g/100 g of white wine vinegar, 4 g/100 g of table salt,
2 g/100 g of garlic powder, 2 g/100 g of red pepper flakes,
1 g/100 g of basil leaves, and 1 g/100 g of oregano leaves.
Afterward, either 0.5 g/100 g of PPP, 3 g/100 g of MPP powder
(equivalent to 0.5 g/100 g free polyphenol-containing ex tracts),
or 0.5 g/100 g of GSE were added as natural antioxidants. Also,
an ISD without natural antioxidants was prepared as a control.
Then, the mixtures were homogenized at a shear rate of 1 g
(LOW) or 280 g (HIGH) using an ultra-high shear homogenizer
(Fisherbrand 850 Homogenizer, Thermo Fisher Scientific Inc.,
Chicago, IL , USA) for 10 min. In total, eight dif ferent ISDs were
prepared ( Table 1) which were immediately characterized after
production and stored under ACSL and AMSL conditions. The
RGB (red, green, and blue) images of the resultant ISDS are
shown in Figure 1.
2.5 | EmulsifyingpropertiesofISDs
Emulsifying capacity (EC) and emulsion stability (ES) were evalu-
ated according to the method of Yang et al. (2018). For EC, the
ISDs were centrifuged at 8000 × g for 12 min using a centrifuge
(Model J2-21M; Beckman Instruments Inc., Palo Alto, CA, USA).
Meanwhile, for the ES, the fresh samples were held in a hot water
bath (Model 2872; Thermo Fisher Scientific Inc., Marietta, OH,
USA) at 80°C for at least 1 h, then the samples were centrifuged at
700 × g for 12 min. After ward, the EC and ES values were calculated
using Equation (2).
where EL (g) is the mass of the resultant emulsified layer. FE is the
whole mass ( g) of the fresh samples.
(1)
𝜎=K𝛾n
(2)
EC or ES (%)=(EL ∕FE)×100
TAB LE 1 Description of Italian salad dressings (ISDs) evaluated
in the study.
ISD
Mixing conditions
(shear rate)
Naturalantioxidant(g/100 g)
PPP MPP GSE
LC LOW – – –
LPPP LOW 0.5 – –
LMPP LOW – 3 –
LGSE LOW – – 0.5
HC HIGH – – –
HPPP HIGH 0.5 – –
HMPP HIGH – 3 –
HGSE HIGH – – 0.5
Abbreviations: GSE, grape seed extract; HC, ISD prepared with high
shear without antioxidant; HGSE, ISD prepared with high shear with
GSE; HIGH, high shear rate, 500 0 rpm; HMPP, ISD prepared with high
shear with MPP; HPPP, ISD prepared with high shear with PPP; LC, ISD
prepared with low shear without antioxidant; LGSE, ISD prepared with
low shear with GSE; LMPP, ISD prepared with low shear wit h MPP;
LOW, low shear rate, 250 rpm; LPPP, ISD prepared with low shear with
PPP; MPP, microencapsulated PPP powder; PPP, polyphenol-containing
extracts isolated from pomegranate peels.
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YA NG et al .
2.6 | Storagestability
Approximately 100 mL of ISDs was placed in 4 oz. regular mouth
mason glass jars with metal lids (Verones Direct, Shenzhen,
Guangdong, China), and stored at 55°C in an air-forced oven (MO
1440SC , Lindberg/ Blum M, Asheville, NC, USA) for 21 days for
ACSL and/or at room temperature (~25°C) in light-proof cabi-
nets for 8 weeks for AMSL, respectively. All ISDs were evalu-
ated for pH, color, peroxide value (PV ), iodine value (IV), and
thiobarbituric acid reactive substances (TBARS) as described
in Sections 2.7–2.9. Analyses were conducted every 3 days and
every 2 weeks for samples stored under ACSL and AMSL condi-
tions, respectively.
2.7 | pHofISDs
Approximately, 20 mL of sample was placed in a beaker and the
pH value was measured using a previously calibrated pH bench-
top meter (Accumet AE150, Fisher Scientific Inc., Chicago, IL,
USA).
2.8 | Color
The color of the ISDs was measured using a Lab Scan XE Colorimeter
(Hunter Associates Laboratory, Inc. Reston, VA) and the results were
reported as CIE (L*, a*, and b* value). The total color difference (ΔE)
of salad dressings was calculated from the method reported by Jiang
et al. (2020) and using Equation (3):
where
L0
,
a0
, and
b0
are the value s of fr es hly made IS Ds (day 0) ;
Ld
,
ad
, and
bd
are the corresponding values of the ISDs after storage for certain
time intervals (days 3, 6, 9, 12, 15, 18, and 21 for ACSL; weeks 2, 4, 6,
and 8 for AMSL).
2.9 | Oxidationstability
2.9.1 | PV determination
The PV of ISDs was determined based on AOAC official method
965.33 (George & Latimer, 2 016). Approximately 20 g of ISDs was
centrifuged at 450 0 × g for 5 min, then the top layer was collected and
filtered through Whatman No. 4 filter paper (Whatman International
Ltd., Maidstone, UK). Af terward, approximately 5 g of samples was
dissolved in 30 mL of glacial acetic acid−isooctane (3:2, v/v). Upon
addition of 0.5 mL of saturated potassium iodide solution and 30 mL
of deionized water, the solutions were then titrated against 0.01 M
standardized sodium thiosulfate (Na2S2O3) solution using 0.5 mL of
1% starch indicator until the blue color was just disappeared. The PV
was calculated as shown in Equation (4).
where PV is reported as the millimolar peroxide per kilogram of the
sample, S is the volume of titrant (mL) for samples, B is the volume
of titrant (mL) for blank, C is the concentration of Na2S2O3 solution
(mol/L), W is the mass of the samples (g), and 1000 is the conversion
of units (g/kg).
2.9.2 | Quantification of IV
The IV of ISDs was calculated by following the AOAC official method
993.20 (George & L atimer, 2016). Ten grams of salad dressings was
centrifuged at 4500 × g for 5 min, then the supernatant was collected
and filtered through Whatman No. 4 filter paper. Afterward, 0.3 g of
filtered samples was dissolved in 10 mL of chloroform. Next, 25 mL
of Wijs solution was added and the mixture was then placed in the
dark at room temperature for 1 h. Thereafter, 15 mL of 15% (w/v) po-
tassium iodide solution and 110 mL of deionized water were added
to the samples. The resultant solutions were gradually titrated
against 0.1 M standardized sodium thiosulfate solution using 1 mL
(3)
Δ
E=
√(
L
0
−L
d)
2+
(
a
0
−a
d)
2+
(
b
0
−b
d)2
(4)
PV
=(
S−B
)
×C×1000
2×W
FIGURE1 Pictures of Italian-style
homemade salad dressings (ISDs). See
Table 1 for the description of LC, LPPP,
LMPP, LGSE, HC, HPPP, HMPP, and HGSE.
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YAN G et a l.
of 1% starch indicator until the blue color disappeared. The iodine
value was calculated based on the Equation (5).
where IV value equals to gram iodine absorbed per 100 g of sample, B
is the volume of titrant (mL) for blank, S is the volume of titrant (mL) for
samples, N is the normality of Na2S2O3 (mol/L), 126.9 is the molecular
mass of iodi ne (g /m ol ), W is th e ma ss of th e sam ple s (g), and 100 0 i s the
conversion of units (mL/L).
2.9.3 | TBARS analysis
TBARS value of ISDs was determined by following the method re-
ported by Nielsen (2017). Approximately 2 g of samples was dis-
solved in 10 mL of 10% trichloroacetic acid solution and centrifuged
at 1200 × g for 5 min to collect the supernatants. Afterward, 4 mL of
0.5% 2-thiobarbituric acid solution was added to the supernatants,
and a blank (4-mL deionized water mixed with 4 mL of 0.5% 2-thio-
barbituric acid solution) was also prepared. Then, all the samples
were heated in boiling water for 40 min. After cooling to room tem-
perature, the absorbance of samples was recorded using a Genesys
30 ultraviolet–visible spectrophotometer (Thermo Fisher Scientific
Inc., Madison, WI, USA) set at λ = 532 nm. Quantification was based
on the standard cur ve generated with 1, 1, 3, and 3-tetraethoxypro-
pane (TEP), and the result was reported as mg TEP/kg.
2.10 | Statisticalanalysis
All the experiments and analyses were carried out in triplicate de-
terminations. Means and SD of experimental results were reported,
and the data were analyzed using the statistical software SAS (SAS
University edition version 3.8, SAS Institute, Cary, NC, USA). The
significant differences among means of experimental results were
analyzed by an analysis of variance (ANOVA). A p value less than
alpha = 0.05 was statistically significant .
3 | RESULTSANDDISCUSSION
3.1 | PhenoliccompoundanalysisofPPP,MPP,and
GSE
The tannin content of PPP, MPP, and GSE is shown in Table 2.
The total hydrolyzable tannin content of PPP and MPP was
283.09 ± 98.81 and 427.74 ± 28.53 (mg/g ex trac t), respectively.
Condensed tannins were not detected in PPP and MPP, but were
found in GSE (348.53 ± 173.09 mg/g extract), which is in line with
previous work integrated by Cai et al. (2017). Canuti et al. (2020)
have reported that hydrolyzable tannins, particularly ellagitannins
including α-punicalagin and β-punicalagin, are highly effective in
(5)
IV
=(
B−S
)
×N×126.9
W×1000
×
100
TAB LE 2 Phenolic compound analysis of PPP, MPPP, and GSE*.
Sample
Tannins (mg/g extract) Monomeric phenolic compounds (mg/g extract)
α-Punicalagin β-Punicalagin Ellagic acid Total tannin content Gallic acid (+)-catechin (−)-epicatechin Unknown Unknown
PPP 108. 29 ± 34.87b101.01 ± 35.68a73.81 ± 28.29a283.09 ± 98.81a20.55 ± 2.3 4b8.36 ± 1.21b− 2. 28 ± 0.46c−
MPP 174. 4 8 ± 13.01a138.54 ± 9.42a114 .5 4 ± 6.40a42 7.74 ± 28.53a3 0.48 ± 0. 20a20.88 ± 0.36a− 6.0 0 ± 0.17a−
GSE − − − 348.53 ± 173.09a− 2.63 ± 0.21c2.63 ± 0.12 3.03 ± 0.06b12.73 ± 0.40
Note: Means with the same superscript let ter in the same column are not significantly different (p < .05). See Ta b le 1 for t he description of PPP, MPP, and GSE.
*Values are the mean ± SD of triplicate determinations.
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YA NG et al .
regulating oxidation and protecting the wine against chemical oxi-
dation. It is impor tant to note that the analyses were conducted in
an oth e r sta te in th e US. Du rin g sto r age , tran spo r t ati on, an d pre p ara -
tion of the samples, the tannins in the PPP might have degraded due
to exposure to environment al factors such as light, heat, and oxygen.
The tannin content in MPP may have remained higher than in PPP
due to the protection effect of the microencapsulation. Flavanols in-
cluding (+)-catechin and an unidentified flavanol detected at 280 nm
were quantified (20.88 ± 0.36 and 6.00 ± 0.17 mg/g dry extract,
respectively) in MPP, and their content was higher than the corre-
sponding content (8.36 ± 1.21 and 2.28 ± 0.46 mg/g dry extract) in
PPP (Table 2). The flavanols found in GSE were mainly (+)-catechin,
(−)-epicatechin, and two unknown compounds detected at 280 nm.
Fruit flavanols have been demonstrated to have high efficacy in pre-
venting lipid peroxidation in different systems and have shown posi-
tive effects against developing diseases such as atherosclerosis and
coronar y heart disease (Panche et al., 2016).
3.2 | RheologicalpropertiesofPPPsuspensions
A non-Newtonian, shear-thinning (pseudoplastic) behavior (indicated
by n < 1) was observed for PPP suspensions, which might be at trib-
uted to the phy sic al di sru pti on of cha in entan gl e me nts in pect in mo l-
ecules (Morales-Contreras et al., 2018). The shear-thinning property
of PPP helped to provide a pleasant mouthfeel (Chen et al., 2020).
The results also revealed that the power law model effectively de-
scribed the flow behavior of PPP suspensions (R2 = 0.996) with con-
sistency index (K) value = 0.059, indicating a relatively low viscosity.
Therefore, the PPP suspensions can be easily pumped and atomized
into the spray dryer's chamber to produce MPP powders.
3.3 | Emulsifyingcapacityandemulsion
stability of ISDs
Emulsifying capacity refers to the ability of surfactants and other
ingredients to facilitate the formation of food emulsions (Liang
et al., 2015). ISDs homogenized at high shear rates had significantly
higher (p < .05) emulsifying capacity (%) values than those homog-
enized at a lower shear rate (Table 3). At higher shear rates, the par-
ticle–particle collisions and interactions were higher, which might
have resulted in smaller micelles and suspended solids. Therefore,
only suspended and tiny micelles and par ticles remained in the salad
dressings, resulting in higher emulsion capacity (Brewer et al., 2016).
Interestingly, LMPP and HMPP, which contained microencapsulated
PPP powders, had significantly (p < .05) higher EC than the other
ISDs prepared with other antioxidants and homogenized at low and
hig h sh ear rates, re sp ec tively (Table 3). This effect may be due to the
higher viscosities and emulsification properties of the maltodextrin–
pectin found in the MPP powders. Different food produc ts show
different levels of EC and ES. Although there is no defined value for
EC or ES for ISD s, Fernan de s an d Salas Mel lado (2018) repor ted that
mayonnaises prepared with different levels of freeze-dried chia mu-
cil age wi th an EC of 63 .7 %. Similarly, Dabb ou r et al. (2018) evaluated
the EC of food emulsions containing soybean oil and sunflower meal
protein, and the results ranged from 49.09 to 52.45%.
On the other hand, emulsion stabilit y measures the ability of
food emulsions to stabilize the fine droplets during and after the
emulsification process (Liang et al., 2015). The results obtained in
this study showed that the emulsion stability of ISDs ranged from
55.45 to 63.17%. As in the previous case of EC, ISDs homogenized
at high shear rates had significantly (p < .05) higher ES values than
those homogenized at lower shear rates (Table 3). Moreover, LMPP
had a significantly (p < .05) higher ES compared to LC, LPPP, and
LGS E; while HMPP showe d an ES (%) of 63.17 which was si gn if icantly
(p < .05) higher than those of HC (60.06), HPPP (60.22), and HGSE
(60. 21) (Table 3). The higher ES values of LMPP and HMPP may be
explained by the presence of maltodextrin: pectin in MPP, which may
have helped create more stable suspensions with higher viscosities.
Similar findings have been reported by Perrechil et al. (2010) for ES of
commercial Italian salad dressings during 6 days of storage (50–65%).
However, our results were lower than the ES values (81.8–88.2%)
reported by Mohamad et al. (2019) who utilized cocoa but ter as a
stabilizer for salad dressings. According to Lozano-Gendreau and
Vélez-Ruiz (2019), food emulsions and suspensions with high oil con-
tent (>50% w/w) may show lower values of EC and ES.
3.4 | LipidoxidationinISDsunderaccelerated
storage conditions
3.4.1 | Changes in pH and color
Fresh ISDs had an initial pH of ~3.08–3.16, which decreased over
time and showed an average value of 3.05 at 21 days of accelerated
storage (Figure 2a). It has been reported that the slight reduction
in pH in salad dressing during accelerated storage may be due to
increased vibrations of molecules at higher temperatures and the
TABLE3 Emulsifying capacity and emulsion stability of ISDs*
ISD Emulsifying capacity (%) Emulsion stability (%)
LC 53.54 ± 0.06d55.45 ± 0.26d
LPPP 53.96 ± 0.08d55. 61 ± 0.05d
LMPP 57. 50 ± 0.13b58.82 ± 0.13c
LGSE 53. 84 ± 0.07d55.68 ± 0. 28d
HC 56.80 ± 0.14 c60.06 ± 0.06b
HPPP 57. 4 0 ± 0.29b60.22 ± 0.05b
HMPP 60.41 ± 0.32a63.17 ± 0.05a
HGSE 57. 4 4 ± 0.31b60.21 ± 0.02b
Note: Means with the same superscript let ter in the same column are
not significantly different (p < .05). See Tab l e 1 for description of LC ,
LPPP, LMPP, LGSE, HC, HPPP, HMPP, and HGSE.
*Values are the mean ± SD of triplicate determinations.
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YAN G et a l.
formation of secondary products such as acetic and propanoic acids
as well as free fatty acids from lipid oxidation (Kiokias et al., 2016).
According to Tseng & Zhao, 2013, the relatively stable acidic envi-
ronment of salad dressings may help to stabilize polyphenols which
may be able to control lipid oxidation for longer periods.
The color parameters (L*, a*, and b* values) of ISD dressings
during ACSL are listed in Table 4. On day 0, all of the salad dress-
ings had a lemon-yellow color (hue angles between 58 and 71) with
color saturation ranging from 23.29 to 32.61. An analysis of vari-
ance revealed that the antioxidants and the shear rate of homoge-
nization had a significant effect (p < .05) on the color parameters of
salad dressings. After 21 days of accelerated storage, the lightness
(L*) and yel lown es s (b*) of all ISD s we re sig ni ficantl y (p < .05) reduced
and resulted in darker ISDs. It has been suggested that these color
changes in food emulsions/suspensions with high oil concentrations
may be due to flocculation which is accelerated by the lower vis-
cosities of the continuous phase at higher storage temperatures
(Lozano-Gendreau and Vélez-Ruiz, 2019). Interestingly, the changes
in a* values (redness) of ISDs were less noticeable than the changes
in L* and b* values. Furthermore, not all ISDs had a significant re-
duction in redness (a*) and the minor decrease in a* values could
be explained by the degradation of functional ingredients due to
oxidative reactions observed at high storage temperatures (Phisut
et al., 2018). Moreover, the total color dif ference (ΔE) of ISDs is pre-
sented in Figure 2b. It was noted that the ΔE of all salad dressings
was >10. LMPP had the most dramatic ΔE valu e s wh ile HG SE ha d the
lowest value of ΔE. In general, salad dressings homogenized at high
shear rates had lower ΔE than those prep ar ed at low shea r ra te s. The
significant color differences through storage could be attributed to
(a) the flocculation of the oil droplets and suspended solids (Lozano-
Gendreau and Vélez-Ruiz, 20 19); and (b) the presence of weak acids
(vinegar) could lead to the extraction of more and different pigments
from the ingredients at elevated temperatures which may have in-
creased the diffusion rate and solubility of pigments in salad dress-
ings (Mohamed et al., 2016; Oancea et al., 2012).
3.4.2 | Lipid oxidation
Lipid oxidation is one of the significant concerns in food quality de-
terioration. The oxidative process of lipids may be catalyzed by light,
heat, enzymes, metals, and microorganisms (Tseng & Zhao, 2013).
PV, IV, and TBARS values are three common indicators of lipid oxi-
dation in foods. Furthermore, PV indicates the quantity of peroxides
and hydroperoxides formed in the initiation stage of lipid oxidation.
As shown in Figure 3a, the PV of all ISDs significantly (p < .05) in-
creased during storage, especially for those without antioxidants (LC
and HC). Peroxides were detected after 6 days in LC and HC and
after 9 days in antioxidant-containing ISDs. Moreover, LC and HC
had significantly (p < .05) higher PVs (approximately 50%) than the
rest of ISDs after 21 days of storage. Curiously, the shear rates did
not af fec t the PV of IS Ds (Figure 3a). All antioxidant-containing ISDs
showed similar PVs at the end of 21 days of storage. The result s may
have indicated that high storage temperature could accelerate the
oxidation of oils. Interestingly, antioxidants used in the study were
effective at delaying lipid oxidation in ISDs to some extent. It has
been reported that the PV of commercial salad dressings should be
at most 10 mmol/k g oil (Lozano-Gendreau and Vélez-Ruiz, 20 19). All
ISDs were under the maximum limit for PV; however, they all showed
signs of lipid oxidation, as observed in IV and TBARS. Vegetable oils
with a high content of polyunsaturated fatty acid (PUFA) are more
vulnerable to lipid oxidation, while the presence of saturated fatty
acid (SFA) and monounsaturated fatty acid (MUFA) could improve
their oxidative stability (Cao et al., 2015). The ma in fat t y acid s in pea -
nut oil are oleic acid (45–53%, MUFA), linoleic acid (27–32%, PUFA),
and palmitic acid (11–14%, SFA) (Ghazani & Marangoni, 2016). PV
can only measure initial lipid oxidation products; meanwhile, hy-
droperoxides are unstable molecules that decompose quickly into
secondary oxidation products such as aldehydes during storage at
elevated temperatures (Eidhin & O'Beirne, 2010). This may have
FIGURE2 pH values (a) and color changes (b) of ISDs stored
under ACSL conditions. See Table 1 for description of LC, LPPP,
LMPP, LGSE, HC, HPPP, HMPP, and HGSE.
8
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YA NG et al .
TAB LE 4 Color values (L* a* b*) of Italian salad dressings (ISDs) during accelerated storage (ACSL)a.
Color parameter ISD Day 0 Day3 Day 6 Day 9 Day 12 Day 15 Day 18 Day 21
L*LC 21.55 ± 0.56a20.67 ± 0.3a17. 9 ± 0.25b16 .58 ± 0.08c14.1 2 ± 0.56d13.07 ± 0.15e11.8 4 ± 0. 32f8.21 ± 0.30g
LPPP 21.59 ± 0 .41 a19.9 7 ± 0.49b18.46 ± 0. 52c18.60 ± 0.58c16.94 ± 0.58d13 .97 ± 0.31e8.76 ± 0.16f5.33 ± 0. 25g
LMPP 26.07 ± 0.10a25.86 ± 0.39a22. 28 ± 0.38c23.66 ± 0.54b1 7.41 ± 0.39d16. 05 ± 0.02e13.75 ± 0.37f9. 6 6 ± 0. 54g
LGSE 2 9.9 4 ± 0.39 24 .79 ± 0.19b19.72 ± 0.44c16.91 ± 0.48d16 .05 ± 0.33d12.30 ± 0.09e9.97 ± 0.39f7. 2 5 ± 0.08g
HC 32.02 ± 0 .14a24.5 0 ± 0. 57b21.45 ± 0. 32c21.23 ± 0.26c17. 4 3 ± 0.08d12.54 ± 0.53f10 .61 ± 0 .24 g13.65 ± 0.36e
HPPP 30.33 ± 0. 24 23.50 ± 0.19b24.49 ± 0.48b15.07 ± 0 .55d20.00 ± 0. 41c13.77 ± 0.15e11.70 ± 0.36f11.67 ± 0.35f
HMPP 35.85 ± 0.36 a24.14 ± 0.44c26.35 ± 0.23b23.90 ± 0.28c16.93 ± 0.24d11.47 ± 0.20e11.4 4 ± 0.55 e11.07 ± 0.27e
HGSE 27. 5 4 ± 0.43a26.12 ± 0.37b22 .61 ± 0.53c21.12 ± 0.3 4d19. 07 ± 0.19e14. 65 ± 0.25f15.04 ± 0 .12f11 .93 ± 0.15g
a*LC 15.25 ± 0.53a11.06 ± 0.35c9.10 ± 0.23d12.2 ± 0.30b9. 3 3 ± 0.12d14.75 ± 0.38a15.32 ± 0.40a12 . 51 ± 0.27b
LPPP 15.26 ± 0.19a13. 61 ± 0.43c14. 76 ± 0.33ab 14 .28 ± 0.46b15.72 ± 0.15a8 .93 ± 0.16f12 .92 ± 0.42d10. 59 ± 0. 30e
LMPP 15.26 ± 0.19a15.61 ± 0.22a15.49 ± 0.25a15.56 ± 0.28a12.92 ± 0.08b9.38 ± 0.28c8 .29 ± 0.22d7. 5 6 ± 0.57de
LGSE 16.16 ± 0.37a15.92 ± 0.08a12.60 ± 0.15c13.9 9 ± 0.55b16.56 ± 0.05a13.17 ± 0.39b16.48 ± 0.42a8.65 ± 0.29d
HC 9.2 3 ± 0 .16d12.75 ± 0.42a11 .19 ± 0.14 b10. 20 ± 0.18c6.53 ± 0 .19f8.86 ± 0.59e9. 31 ± 0.43d9. 6 3 ± 0. 25d
HPPP 11.4 4 ± 0.12 b11.01 ± 0.57b7.72 ± 0.34e11 .6 8 ± 0 .12b8.46 ± 0.31d10.6 4 ± 0. 32c12.31 ± 0.10a7.9 7 ± 0.17e
HMPP 9.19 ± 0.19b8 .43 ± 0.29bc 8.99 ± 0.06b7. 5 4 ± 0.53c5.4 4 ± 0.34d11.94 ± 0.24 a7.06 ± 0.26c8.88 ± 0.49b
HGSE 10.3 8 ± 0.4 0b7. 11 ± 0.53d8.62 ± 0 .24 c11. 50 ± 0.22a9.82 ± 0.20b7. 55 ± 0.31d10.63 ± 0.18ab 10. 35 ± 0.26b
b*LC 28.6 ± 0 .41a22.72 ± 0.49b15.07 ± 0.19 f20.78 ± 0.39c16.89 ± 0.14e22 .68 ± 0.59b18 .97 ± 0.64d12 .27 ± 0. 54g
LPPP 32.69 ± 0.46a19.9 0 ± 0. 56c21.28 ± 0.44b19.9 3 ± 0.21c13. 22 ± 0. 26f17.06 ± 0.09d14.9 0 ± 0.25e8.67 ± 0.33g
LMPP 32.69 ± 0.46a29. 3 8 ± 0.45b23.70 ± 0.35c20 .41 ± 0.15d12.49 ± 0.3 0h17. 58 ± 0. 51e15.86 ± 0.22f13.32 ± 0.47g
LGSE 15.50 ± 0.53b15.20 ± 0.07b14.67 ± 0. 32bc 17. 0 2 ± 0.40a9.86 ± 0.48g13.30 ± 0.13d12.44 ± 0.58e10.53 ± 0. 47f
HC 27. 18 ± 0.03b29.74 ± 0.40a23.59 ± 0.32c20.07 ± 0. 41e16.71 ± 0.48g18.77 ± 0.45f15.96 ± 0.36g21.36 ± 0.51 d
HPPP 27. 10 ± 0.20a20.85 ± 0.46c2 2.75 ± 0.38b22.02 ± 0.45b16. 69 ± 0.42d22.06 ± 0.18b19. 31 ± 0.36c1 7. 5 4 ± 0.35d
HMPP 23.64 ± 0.40a20.87 ± 0 .16b1 7.1 6 ± 0.09d15.79 ± 0.45e13. 68 ± 0. 29f18.82 ± 0.29c23.37 ± 0.49a17. 4 8 ± 0 . 51d
HGSE 20.05 ± 0.42b13.61 ± 0.28f18.79 ± 0.11c25.94 ± 0.57a20.46 ± 0.27b15.12 ± 0.49e16.15 ± 0.32d18.75 ± 0.26c
Note: Means with the same letter in the same row are not significantly different (p < .05). See Ta ble 1 for description of LC, LPPP, LMPP, LGSE, HC , HPPP, HMPP, and HGSE.
aValues are the mean ± SD of triplic ate determinations.
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9
YAN G et a l.
occurred in LH and HC after day 18 (the PVs of LC and HC at day 18
were higher than those of corresponding samples on day 21). Given
the possibility of decomposition of hydroperoxides, PV only was not
enough to assess the quality of edible oils.
The iodine value measures the degree of unsaturation of fat ty
acids. A decrease in IV indicates an increase in the degree of satura-
tion of fatty acids (Ayodeji & Ganiyu, 2015). Changes in IV of ISDs
are presented in Figure 3b. During the first 12 days of storage, all
ISDs were within the standard range (84–107) of fresh peanut oil
(Karl, 2 017). Not surprisingly, the IV of LC and HC reduced at higher
rates than those of antioxidant-containing ISDs. After 21 days of
storage, the IV of LC and HC was significantly (p < .05) lower than
the rest of the ISDs. Interestingly, LMPP and HMPP had significantly
(p < .05) higher IV (+5%) than those of LC and HC after 21 days of
storage. Even more, shear rates did not have any effect on the IV
of the ISDs during ACSL. These results suggested that ISDs expe-
rienced a reduction in the unsaturation of their fatty acids due to
the breakdown of carbon chain bindings, thus forming saturated
carbon chains (Mohamad et al., 2 019). Antioxidants containing ISDs,
especially those containing MPPP powders, have shown lower lipid
oxidation than ISDs without antioxidants (especially in the first
15 days of storage). Similar trends for IV have been reported by Guo
et al. (2016) in palm oil with rosemary ethanol extract during frying
and accelerated storage and Jahurul et al. (2017) in mango seed fat
and palm oil mid-fraction blends as cocoa butter replacers under ac-
celerated storage conditions.
The TBARS is a parameter used to monitor the produc tion of
secondary lipid oxidation products, mainly malondialdehyde (MDA).
It was noted that the TBARS of all ISDs significantly (p < .05) in-
creased after 21 days of storage (Figure 3c). Surprisingly, LMPP and
HMPP showed significantly (p < .05) lower TBARS than the rest of
the treatments after 21 days of storage. Furthermore, there was
no apparent effect of the shear rates on the TBARS values of ISDs.
Food produc ts with TBARS values lower than 0.576 mg MDA/kg dry
weight (DW) of the sample are considered fresh, those with TBARS
values between 0.65 and 1.44 mg MDA/kg DW are considered ran-
cid but still acceptable, and those with TBARS values higher than
1.5 mg MDA/kg DW are considered unacceptable for consumption
(Cong et al., 2020; Fuchs et al., 2015; Singh et al., 2020). Using those
criteria, all treatments were considered fresh after 9 days of storage.
After 18 days of accelerated storage, all ISDs, but LMPP and HMPP,
could have been considered unacceptable for consumption. In addi-
tion, the results confirmed that antioxidant s effectively delayed the
formation of MDA in salad dressings (Phisut et al., 2018). Also, these
findings suggest that MPP was an effective antioxidant for delaying
lipid oxidation in a salad dressing system after 21 days of acceler-
ated storage and that the breakdown of peroxides to carbonyl and
aldehyde compounds such as MDA was accelerated by high storage
temperatures (Ayodeji & Ganiyu, 2015).
Accelerated storage is always a cost-effective approach when
predicting the shelf life of foods (Feng, 2011). The estimated shelf
life can be c alculated based on Equation (6) (Joseph, 2016):
where Q10 is a typical value (2.0) to estimate reaction rates in food, T1
is the temperature (55°C) of accelerated conditions, and T2 is the room
temperature (25°C).
In this study, 21 days of ACSL was equivalent to 168 days
(5.6 months) of ambient storage. Using PV as an indicator for the de-
termination of the shelf life of ISDs, all treatments were within the
normal range after 21 days of ACSL. Furthermore, if the results for
IV were to be used to calculate shelf life, the IVs of LC and HC were
below the normal range after 15 days of accelerated storage (equiv-
alent to 120 days of ambient storage), while MPP-cont aining salad
dressings were still acceptable after 18 days of AC SL. Using TBARS
as the leading indicator, the LC, LPPP, LGSE, HC, HPPP, and HGSE
treatments were considered rancid and unacceptable af ter 15 days
of accelerated storage (equivalent to 120 days of ambient stor-
age), while LMPP and HMPP were still considered acceptable after
18 days (equivalent to 144 days of ambient storage). These results
(6)
Estimated shelf life =
Q
10
(
T1
−
T2
∕
10
)
×days of ACSL
FIGURE3 Peroxide value (a), Iodine value (b), and TBARS
values (c) of Italian salad dressings (ISDs) during accelerated
storage (ACSL). ( = LC; = LPPP; = LMPP; = LGSE; = HC;
= HPPP; = HMPP; = HGSE). a–dMeans with the same letter
in the same day are not significantly different ( p < .05). See Table 1
for a description of LC, LPPP, LMPP, LGSE, HC, HPPP, HMPP, and
HGSE.
10
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YA NG et al .
suggest that MPP may extend the shelf life of ISDs by 24 days by
delaying lipid oxidation. However, the results obtained under accel-
erated shelf life studies must be interpreted with care when predic t-
ing the shelf life of foods. Bec ause the oxidation mechanisms could
change with temperature, samples could exhibit excessive rancidity,
which is not associated with t ypical storage conditions. Depending
on the type of oil, these predictions may lead to an overestimation or
underestimation of the actual shelf life (Farhoosh, 2007). Therefore,
it is recommended to confirm accelerated storage with ambient
storage conditions. Nevertheless, when time is constrained, acceler-
ated storage studies provide an exciting approach to evaluating the
preliminary effectiveness of natural antioxidants. A similar study by
Aksoy et al. (2022) reported the use of OXITEST to evaluate the ox-
idative stability of salad dressings enriched with microencapsulated
phenolic extract s from cold-pressed grape and pomegranate seed
oil by-products. The study demonstrated that incorporating those
natural antioxidants significantly increased the oxidation stability of
the salad dressings without lowering their physical stabilit y.
3.5 | LipidoxidationinISDsduringambient
storage conditions
3.5.1 | Changes in pH and color
The pH of the aqueous phase has been reported as a critical factor in
controlling the microstructural stability of food emulsions and sus-
pensions (Seo et al., 2013). The pH changes of salad dressings during
ambient storage conditions are presented in Figure 4a. The initial
pH values of ISDs were ~3.2 and significantly (p < .05) increased
to 3.32–3.38 after storage (25°C, relative humidity of 40–60% in
the dark) for 8 weeks. The increased pH might be explained by the
slight decomposition of acetic acid and other ingredient s in the
salad dressings during storage in a warm and humid environment
(Ahmad, 2020). According to Park and Lee (2009), acetic acid can
be decomposed in oxidation processes in the presence of ultravi-
olet radiation. During storage, the oxygen from the air can slowly
diffuse into the salad dressings, leading to oxidative reactions. The
oxidative degradation of acetic acid may have caused the increase in
pH. Additionally, microorganisms present in the salad dressing can
potentially metabolize acetic acid as a carbon source, leading to its
decomposition.
Generally, the pH of salad dressings is <4.6 (pH of acidified
foods) which limits microbial growth during storage at ambient tem-
perature (Breidt et al., 20 14).
The color parameters (L*, a*, and b* values) of salad dressings
during ambient storage are presented in Table 5. Fresh ISDs had
different lightness, redness, and yellowness because of different
homogenization conditions and different types of ingredients used.
After 8 weeks of storage under AMSL conditions, the degree of light-
ness of all salad dressings was significantly (p < .05) lower than that
of the corresponding fresh samples while there were no obvious
patterns of change in the values of a* and b* during storage. These
results confirmed the results observed in ACSL, where darker ISDs
were obser ved after 21 days of storage.
The total color difference (ΔE) of ISDs during AMSL is shown
in Figure 4b. In general, ISDs prepared at high shear rates showed
lower changes in color compared to the ISDs prepared at low shear
rates. Furthermore, compared with ΔE of salad dressing during ac-
celerated storage, the ΔE of all treatments was smaller under am-
bient storage. Moreover, the ΔE of HC and HMPP were relatively
low and st ab le (6–8) during t he 8-week storage period, which indi-
cated that their color did not change as much as in the case of the
other ISDs. It has been hypothesized that the different ΔE values
could be explained by the extrinsic color changes of ingredients
as well as the homogenization conditions such as shear rates and
homogenization time (Eissa et al., 2016). Overall, these color pa-
rameters should be taken into account when formulating various
salad dressings because consumers have a preconceived prospec t
of the appearance of the different products (Chung et al., 2 017).
FIGURE4 pH values (a) and color changes (b) of ISDs during
ambient storage conditions. See Table 1 for description of LC, LPPP,
LMPP, LGSE, HC, HPPP, HMPP, and HGSE.
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11
YAN G et a l.
3.5.2 | Lipid oxidation
As previously stated, the auto-oxidation of oil is a major problem
in salad dressings, and the primary products from lipid oxidation
can be measured as PV (Kishk & Elsheshetawy, 2013). The PV of
ISDs under AMSL is shown in Figure 5a. It was observed that all
ISDs started to show signs of oxidation within the first 2 weeks of
storage. Also, all samples showed PV lower than 5.5 mmol/kg oil
after 8 weeks of storage. Interestingly, LMPP and HMPP had sig-
nificantly (p < .05) lower PVs than the rest of the ISDs at the end
of the storage time. The results also revealed that ISDs prepared
with MPP had the lowest PV followed by those prepared with
GSE and PPP, respectively. It appears that shear rates did not af-
fect the PV of ISDs under AMSL. Interesting findings were made
after comparing PV in ACSL (Figure 3a) with PV in AMSL (Figure 5a).
PVs obtained in ACSL (3 weeks) were higher than those obtained
under AMSL (8 weeks). This finding was consistent with the previ-
ous findings that PVs under ambient storage were lower than those
obtained under ACSL (Branco et al., 2 011). Similar results have
been reported by Mohammadi et al. (2016), who demonstrated that
microencapsulation of phenolic compounds in double emulsion sys-
tems can increase antioxidant capacity due to a controlled release
effect. An antioxidant's relative effectiveness depended on the lipid
substrate, physical state (emulsion), oxidation time, and temperature
(Lee et al., 2 014).
The IVs of all salad dressings during ambient storage are pre-
sented in Figure 5b. Initially, all ISDs had IVs higher than 96 g io-
dine/100 g oil. Then, the IV of all ISDs was significantly (p < .05)
reduced during ambient storage. At the end of the 8 weeks, LMPP
and HMPP showed significantly (p < .05) higher IVs compared to
the rest of the treatments. Moreover, the IV of LMPP and HMPP
was ~8.1% higher than those of LC and HC. Meanwhile, LC and
HC showed the lowest IV, which may have indicated the highest
decrease in unsaturation (presumably due to oxidation). As in the
case of PV, th ere was no apparent effec t of shear rates on the IV of
ISDs. The results suggested that antioxidants could help to inhibit/
de lay the des t ruc t ion of fat ty ac id dou ble bo nds , thus dela yin g lip id
oxidation. In addition, the controlled release of MPP helped sus-
tain their antioxidant activities longer than unencapsulated/free
antioxidants.
TAB LE 5 Color values (L* a* b*) of Italian salad dressings (ISDs) stored under ambient storage (AMSL) conditionsa.
Color value ISD Week0 Week2 Week4 Week6 Week8
L*LC 18.65 ± 0.13 a10.72 ± 0. 24d11 .43 ± 0. 20b14.3 8 ± 0 .31b9. 5 0 ± 0.07e
LPPP 18.95 ± 0.08a13 .56 ± 0.23e14 .82 ± 0.37d16.05 ± 0.11c17. 5 0 ± 0.13 b
LMPP 25.03 ± 0.12 a17. 5 8 ± 0.14b14.75 ± 0.22e19.6 5 ± 0.15b15.84 ± 0.31d
LGSE 20 .95 ± 0.43a17. 0 0 ± 0.14 b15.10 ± 0.23c1 7. 0 1 ± 0.06b16.62 ± 0.30b
HC 18.95 ± 0.13a14 .6 0 ± 0.36c1 7. 5 3 ± 0.16b1 7. 3 2 ± 0.19b15.01 ± 0.13 c
HPPP 19. 83 ± 0.10 a17. 4 9 ± 0.18c16.82 ± 0.33d18.55 ± 0.03b18.32 ± 0.09b
HMPP 23.23 ± 0.11a19. 4 6 ± 0.36b16. 82 ± 0.42d19. 51 ± 0.19b18.58 ± 0.22c
HGSE 25.91 ± 0.15a15.93 ± 0.03c14.62 ± 0.04d1 7. 3 4 ± 0.06b16.19 ± 0.07c
a*LC 12.63 ± 0. 34c15.93 ± 0. 21a14. 25 ± 0.20b9. 42 ± 0.22d14.37 ± 0.36b
LPPP 12.07 ± 0.26a12.69 ± 0.23a9.5 8 ± 0. 28b9. 28 ± 0.11b9.40 ± 0.17 b
LMPP 9.0 6 ± 0.29b9. 24 ± 0.31b8 .16 ± 0 .13c6 .61 ± 0 .24 d9.9 7 ± 0.31a
LGSE 13.7 7 ± 0.27a9.51 ± 0.27c9. 33 ± 0.10 c10.94 ± 0.30 b13.22 ± 0. 51a
HC 9.4 0 ± 0.14 ab 8.89 ± 0.57b7.62 ± 0.04c7. 0 8 ± 0.12c9.6 6 ± 0.10a
HPPP 9.8 8 ± 0.11a8.30 ± 0.01b9.43 ± 0.32a7. 94 ± 0 .16b8.05 ± 0.10 b
HMPP 12.39 ± 0.12a11 .03 ± 0.14b11.53 ± 0.28b10.00 ± 0.37c12. 51 ± 0. 21a
HGSE 12.64 ± 0.21b13.94 ± 0.25a12.11 ± 0.27b12. 86 ± 0.24b13.99 ± 0.11a
b*LC 30.07 ± 0.71a18.23 ± 0.40 b18.21 ± 0.19b18.98 ± 0.17b14. 64 ± 0.33c
LPPP 27. 95 ± 0 .19a21. 83 ± 0.33b18 . 51 ± 0.20c18.86 ± 0.24c14. 29 ± 0.53d
LMPP 22.02 ± 0.92a18.10 ± 0.64b16 .27 ± 0.17c13.07 ± 0.45 d18.91 ± 0.49b
LGSE 25.37 ± 0.60 a15.55 ± 0. 52d14.43 ± 0. 25e19. 4 0 ± 0.58b18.04 ± 0.35c
HC 26.44 ± 0.28a22.07 ± 0.10b19.7 5 ± 0.18d20.01 ± 0.16c19.82 ± 0.53cd
HPPP 28.14 ± 0.82a20.66 ± 0.49c24.49 ± 0.76b18.89 ± 0.21d15.65 ± 0.64e
HMPP 27. 94 ± 0.48a22.79 ± 0.40bc 23.44 ± 0.44b21. 29 ± 0.38c23.15 ± 0 .59b
HGSE 20.41 ± 0. 47c23.71 ± 0.26a20.43 ± 0.47c23.95 ± 0.28a21.44 ± 0.46b
Note: Means with the same letter in the same row are not significantly different (p < .05). See Ta ble 1 for description of LC, LPPP, LMPP, LGSE, HC ,
HPPP, HMPP, and HGSE.
aValues are the mean ± SD of triplic ate determinations.
12
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YA NG et al .
The initial TBARS value of all ISDs was 0.23 mg MDA/kg oil.
At the end of 8 weeks, LC and HC showed a significantly (p < .05)
higher TBARS (~3.02–3.04 mg MDA/kg oil) than the rest of ISDs.
Moreover, LMPP and HMPP showed significantly (p < .05) lower
TBARS th an the rest of th e tr eatment s (Figure 5c). As in the previous
cases of PV and IV, there was not an apparent effect of shear rates
on TBARS values of ISDs. As we mentioned previously, LC, LPPP,
LGSE, HC, HPPP, and HGSE may have been classified as rancid but
still acceptable; while LMPP and HMPP could have been classified as
fresh (TBARS < 0.6 mg MDA/Kg oil) after 4 weeks of storage. After
6 weeks of storage, all ISDs, but LMPP and HMPP, could have been
classified as unacceptable for consumption. It has been reported
that MDA is one of the many reactive electrophile species that
cause oxidative stress in cells and the formation of advanced glyca-
tion end-products, which are associated with several degenerative
diseases such as cancer, diabetes mellitus, and kidney dysfunction
(Oboh et al., 2014 ).
Normally, polyphenols can act as chain-breaking antioxidants,
hydroperoxide destroyers, and metal chelators (Chong et al., 2015).
The phenolic hydroxyl groups could donate hydrogen atoms to scav-
enge free radicals such as hydroxyl, peroxyl, superoxide, and nitric
oxide which were produced from the mixtures of secondary oxida-
tion products and transition metals in the aqueous phase of salad
dressings, resulting in retardation of the initiation or propagation
stage of lipid oxidation. Therefore, these antioxidants can interfere
with fur ther lipid oxidation in salad dressings.
4 | CONCLUSION
The study demonstrated the effectiveness of incorporating micro-
encapsulated polyphenols from pomegranate peels (MPP) in the
Italian salad dressings system to control lipid oxidation during accel-
erated and ambient storage conditions. All fresh salad dressings had
a lemon-yellow color, and those prepared at high she ar rat es had sig-
nificantly higher emulsion stability than those prepared at low shear
rates. Mixing conditions did not affect the lipid oxidation and quality
deterioration in the salad dressings during storage. Results from the
accelerated storage suggested that incorporating MPP could have
extended the shelf life of salad dressings by 20% (24 days) compared
to using an unencapsulated polyphenols extract. Moreover, MPP-
containing salad dressings stored at accelerated and ambient condi-
tions showed less indication of lipid oxidation than those prepared
with unencapsulated polyphenol extract. Microencapsulation pro-
vides an exciting potential to improve the stability of natural antioxi-
dants when they are added to high lipid content and acidified foods
to control lipid oxidation.
AUTHORCONTRIBUTIONS
Boran Yang: Conceptualization (equal); investigation (lead); meth-
odology (lead); sof tware (equal); writing – original draft (lead). Jinru
Chen: Funding acquisition (lead); resources (equal); writing – review
and editing (equal). Kevin Mis Solval: Data curation (equal); funding
acquisition (equal); investigation (supporting); methodology (sup-
porting); project administration (lead); resources (equal); supervision
(lead).
ACKNOWLEDGMENTS
The authors want to acknowledge the support of the USDA National
Institute of Food and A griculture, Hatch Project 1021399.
FUNDINGINFORMATION
This research was funded by the USDA/AMS (Agricultural
Marketing Service) Specialty Crop Block Program grant (SCBGP)
administered by the Georgia Depar tment of Agriculture Award no.
RSRC0001136001.
CONFLICT OF INTEREST STATEMENT
There are none to declare.
FIGURE5 Peroxide value (a), iodine value (b), and TBARS values
(c) of Italian salad dressings (ISDs) during ambient storage (AMSL).
( = LC; = LPPP; = LMPP; = LGSE; = HC; = HPPP;
= HMPP; = HGSE). abcdMeans with the same letter in the
same day are not significantly different (p < .05). See Table 1 for
description of LC, LPPP, LMPP, LGSE, HC, HPPP, HMPP, and HGSE.
|
13
YAN G et a l.
DATA AVAIL AB I LI T Y STATE MEN T
Limited data will be made available upon request.
ORCID
Kevin Mis Solval https://orcid.org/0000-0002-1568-640X
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