A novel mitigator of enzymatic browning-hawthorn leaf extract and its application in the preservation of fresh-cut potatoes
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Food Quality and Safety, 2021, 5, 1–9
doi:10.1093/fqsafe/fyab015
Article
Article
A novel mitigator of enzymatic browning—
hawthorn leaf extract and its application in the
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preservation of fresh-cut potatoes
Liping Qiao (乔丽萍)1,3, Hailin Wang (王海林)1, Jinsheng Shao (邵金升)1,
Laifeng Lu (路来风)1, Jinhu Tian (田金虎)2 and Xia Liu (刘霞)1,*
1
State Key Laboratory of Food Nutrition and Safety, Ministry of Education, Tianjin Key Laboratory of Food Nutrition and
Safety, College of Food Science and Engineering, Tianjin University of Science & Technology, Tianjin, China; 2College
of Biosystems Engineering and Food Science, National–Local Joint Engineering Laboratory of Intelligent Food
Technology and Equipment, Zhejiang Key Laboratory for Agro-Food Processing, Zhejiang Engineering Laboratory
of Food Technology and Equipment, Fuli Institute of Food Science, Zhejiang University, Hangzhou, China and 3Tianjin
Gasin-DH Preservation Technology Co. Ltd., Tianjin, China
*Correspondence to: Xia Liu, State Key Laboratory of Food Nutrition and Safety, Key Laboratory of Food Nutrition and Safety, Min-
istry of Education, Tianjin Key Laboratory of Food Nutrition and Safety, College of Food Science and Engineering, Tianjin University
of Science & Technology, Tianjin 300457, China. E-mail: liuxia831930@163.com
Received 3 March 2021; Revised 6 April 2021; Editorial decision 14 April 2021.
Abstract
Objectives: The purpose of this study was to evaluate the antibrowning functions of hawthorn leaf
extract on fresh-cut potato and its possible mechanism.
Materials and Methods: Fresh-cut potatoes were treated with different concentrations (0.01%, 0.05%,
and 0.1%) of hawthorn leaf extract and preserved at 4 ℃ for 8 days. The appearance and colour of
potato slices were evaluated, along with the content of the phenol, malondialdehyde (MDA), and
hydrogen peroxide (H2O2) during cold storage. Meanwhile, the activities of polyphenol oxidase
(PPO), peroxidase (POD), phenylalanine ammonia-lyase (PAL), lipoxygenase (LOX), catalase (CAT),
superoxide dismutase (SOD), and the antioxidant capacity were determined. Furthermore, the
composition of hawthorn leaf extract was analyzed by high-performance liquid chromatography–
tandem mass spectrometry (HPLC-MS/MS).
Results: The addition of hawthorn leaf extract effectively delayed the browning process. It not
only enhanced the CAT activity and antioxidant capacity but also reduced the LOX activity and
accumulation of MDA and H2O2. Meanwhile, the activities of PPO, POD, and PAL as well as the
content of phenol were controlled. Additionally, 25 phenols, 34 flavonoids, and 5 proanthocyanidins
were identified through high-performance liquid chromatography–tandem mass spectrometry
(HPLC-MS/MS), including caffeic acid, quercetin and catechol.
Conclusion: Hawthorn leaf extract significantly alleviated the browning of fresh-cut potato. It could
serve as a natural antibrowning alternative by stabilizing the membrane and modulating reactive
oxygen species and redox reactions.
Keywords: Hawthorn leaf extract; enzymatic browning; fresh-cut potatoes.
© The Author(s) 2021. Published by Oxford University Press on behalf of Zhejiang University Press.
1
This is an Open Access article distributed under the terms of the Creative Commons Attribution-NonCommercial License (http://creativecommons.org/licenses/
by-nc/4.0/), which permits non-commercial re-use, distribution, and reproduction in any medium, provided the original work is properly cited. For commercial
re-use, please contact journals.permissions@oup.com
2 L. P. Qiao et al.
Introduction were measured. Finally, the composition of HLE was discovered by
high-performance liquid chromatography–tandem mass spectrom-
Minimally processed fruits or vegetables are now popular around
etry (HPLC-MS/MS).
the world and have a promising future because of their advantages of
being fresh, convenient, nutritional and pollution-free (Rizzo et al.,
2018; Tao et al., 2019). However, browning discoloration resulting
Materials and Methods
from fresh-cut processing is an important issue, which can not only
be correlated with the presence of quality characteristics and shelf- Samples and processing
life but also adversely plays a key role in consumer perceptions and Solanum tuberosum potatoes (cv. Netherlands) with yellow flesh
purchase choice (Subhashree et al., 2017; Cairone et al., 2019). It is were obtained from a local farm in Tianjin, China. Potatoes with a
reported that millions of dollars are lost every year due to the discol- uniform size and color and without defects were selected and stored
oration of fruits and vegetables in food industry, and approximately at 4 °C until use. HLE (water extract, extraction ratio 10:1) was
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50 per cent of consumers would wholly discard the food when the purchased from the Xi’an Zelang Biology Co., Ltd. (Xi’an, China).
browning was obvious (Jaeger et al., 2018; Weerawardana et al., Three concentrations of HLE, 0.01 per cent, 0.05 per cent and
2020). Therefore, how to alleviate browning development and main- 0.1 per cent (w/w), were prepared along with the control sample
tain product quality is of great urgency and also makes sense for without extract (CK) using distilled water. First, nondamaged pota-
reducing food waste and financial loss. toes were washed, peeled and sliced into 0.5-cm round chips, which
It is well known that browning discoloration in fresh cuts is the were then washed with tap water. Second, the chips were soaked
result of brown pigment generation and accumulation, which starts in the four prepared solutions for 5 min. Third, the samples were
from the oxidation of phenols to quinones and ends with melanin- placed into a 280 mm×180 mm polyethylene self-sealed bag after
like transformation by polyphenol oxidase (PPO) or peroxidase drying with gauze. Each bag contained nine fresh-cut potato chips
(POD) when oxygen is available (Jiang et al., 2014). Meanwhile, from at least three different potatoes. Finally, the treated samples
phenol and phenylalanine ammonia lyase (PAL) also play a key role were stored for 8 days at (4±1) °C, and every 2 days the samples
in the occurrence of browning (Cantos et al., 2002; Dong et al., were measured.
2016). Furthermore, the antioxidant level has been demonstrated
to be highly associated with browning alteration, such as the ac- Assessment of color
tivities of catalase (CAT) and superoxide dismutase (SOD) as well
A colorimeter (HP-200, Shanghai, China) was used to measure the
as the antiradical capacity (Chumyam et al., 2019). Additionally,
browning of the slices, including the L*, a*, and b* values, which
lipoxygenase (LOX) activity and accumulation of malondialdehyde
indicated the brightness, reddish-greenish, and yellowish-bluish, re-
(MDA) and hydrogen peroxide (H2O2) were revealed to participate
spectively (Liu et al., 2019). Each slice was measured three times at
in browning development (Gao et al., 2017; Zheng et al., 2019).
different points. The overall color
variation (ΔE*) were evaluated
In recent decades, many physical and chemical technologies
based on the equation: ∆E∗ = ∆L∗ 2 +∆a∗ 2 +∆b∗ 2 .
have been explored to reduce browning. However, due to the high
cost, low operability or potential hazard concerns, some methods
are limited to some extent (Moon et al., 2020). Focusing on a nat- The activities of PPO, POD and PAL, and the
ural, safe and low-cost antibrowning substance is of interest. It is phenolic content
worth mentioning that natural extracts with certain health and The activities of PPO and POD were determined by following a
antibrowning properties have become a hot spot, along with people’s minor modification to a previously described procedure (Tao et al.,
pursuit of natural and safe foods. Several antibrowning extracts have 2019). The crude extract was homogenized using 2.0 g sample tis-
been demonstrated to efficiently reduce browning in fresh cuts, such sues in 5.0 mL of extraction buffer containing 1 mmol L–1 poly-
as pineapple extract (Supapvanich et al., 2012), nectarine extract ethylene glycol (PEG), 4 per cent polyvinylpolypyrrolidone (PVPP)
(Redondo et al., 2016), ginger extract (Weerawardana et al., 2020), and 1 per cent Triton X-100. After centrifugation at 4 °C (12 000×g,
grape seed extract (Altunkaya and Gökmen, 2012), hibiscus flower 30 min), the supernatant was collected for activity determination.
extract (Wessels et al., 2014), apple pomace and peel extract (Dias The PPO activity reaction system contained 4.0 mL of 50 mmol L–1
et al., 2020), potato peel extract (Venturi et al., 2019), mango peel acetic acid–sodium acetate buffer, 1.0 mL of 0.05 mmol L–1 catechol
extract (Jirasuteeruk and Theerakulkait, 2019), pine needle ex- solution and 0.1 mL of supernatant. The absorbance value was recorded
tract (Yu et al., 2014), basil leaf and wheat bran extracts (Sikora at 420 nm every 1 min within 6 min. The PPO activity of the fresh weight
et al., 2019), tea extract (Yu and Zeng, 2013), purslane extract (Liu sample was expressed as U g–1.
et al., 2019), and grape leaf extract (Altunkaya, 2014). The haw- The POD reaction mixture is composed of 3.0 mL of
thorn leaf is widely used in traditional chinese medicine with the 0.025 mol L–1 guaiacol solution, 0.5 mL of supernatant, and 0.1 mL
antiradical and antihypertensive functions and membrane protection of 0.5 mol L–1 H2O2 solution. After rapid mixing, the absorbance at
effects, which is inseparable from maintaining the polyphenols, fla- 470 nm was recorded every 30 s for 3 min. The POD activity of the
vonoids and procyanidins (Öztürk and Tunçel, 2011; Włoch et al., fresh weight sample was shown as U g–1.
2013). However, whether hawthorn leaf extract (HLE) could serve The PAL was assessed by a slightly modified procedure (Liu et al.,
as an antibrowning alternative to the above-mentioned extracts is 2018). First, potato tissue (2.0 g) was ground into homogenate with
unknown. 5.0 mL of extraction buffer containing 2 mmol L–1 EDTA, 4 per cent
This research aims to investigate whether HLE could influence polyvinylpyrrolidone (PVP) and 5 mmol L–1 β-mercaptoethanol.
the browning process of potato slices during storage and explore After centrifugation at 4 °C (12 000×g, 30 min), 0.5 mL of super-
how it works from the perspective of antioxidant modulation. The natant was rapidly mixed with a reaction solvent containing 0.5 mL
activities of PPO, POD, and PAL as well as phenol accumulation of 0.02 mol L−1 l-phenylalanine and 3.0 mL of 0.05 mol L−1 boric
were determined. Furthermore, the activities of SOD, CAT, and acid buffer (pH 8.8), which was incubated at 37 °C for 10 min.
LOX, the contents of MDA and H2O2, and the antioxidant capacity Finally, the reaction mixture was incubated at 37 °C for 60 min, and
Hawthorn leaf extract controlled the browning of potatoes 3
the A290nm was recorded. The PAL activity of fresh weight samples and incubated for 15 min. Finally, the reaction was stopped and the
was shown as U g–1. A560nm was recorded. The SOD activity was shown as U g–1.
The total phenolic content was measured via a modified method The scavenging capacity of the 2,2-diphenyl-1-picrylhydrazyl
(Liu et al., 2018). First, the extract was prepared by homogenizing a (DPPH) radical by HLE was calculated (Zheng et al., 2019).
2.0 g sample with 60 per cent ethanol (5 mL), followed by centrifu- Absorbance values were obtained at 517 nm, and the A0, Ar and As
gation (12 000×g, 10 min). Then, the extract supernatant (0.5 mL), were recorded; DPPH(%)=[1−(As−Ar)/A0]×100%.
20 per cent (w/w) Na2CO3 solution (1.6 mL), Folin’s phenol reagent
(0.5 mL) and distilled water (4 mL) were mixed well and incu-
The photochemistry of the HLE
bated for 25 min in the dark. Finally, the A760nm was determined.
The content of flavonoids in the HLE was estimated by a previ-
A standard curve of gallic acid was established to quantify the total
ously reported procedure with slight alterations (Meda et al., 2005).
phenolic content as g kg–1.
One gram of HLE was diluted with 5 mL of a 2 per cent aluminum
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chloride solution. The mixture was ultrasonicated for 30 min and
MDA and H2O2 contents and LOX activity centrifuged at 12 000×g and 4 °C for 10 min. Finally, the absorbance
MDA accumulation was estimated by a previously reported pro- was measured at 415 nm, and the content of flavonoids was deter-
cedure with minor alterations (Zheng et al., 2019). First, 1.0 g mined by the rutin standard curve method. The phenol content in
samples were homogenized in 100 g L–1 trichloroacetic acid (TCA, HLE was determined as above mentioned method meanwhile.
5.0 mL) solution and centrifuged at 4 °C (12 000×g, 20 min). Second, The HLE was analyzed by liquid chromatography–tandem mass
2.0 mL of the supernatant was mixed with 0.67 per cent tert-butyl spectrometry (LC-MS/MS), which included a Thermo Vanquish
alcohol (2.0 mL) and held at 100 °C for 20 min. The blank tube used UHPLC (Thermo Fisher Scientific, Germering, Germany) and a Q
2.0 mL of 100 g L–1 TCA solution instead of the extract. Third, after Exactive™ HF mass spectrometer detector (Thermo Fisher Scientific,
cooling and centrifugation at 4 °C (12 000×g, 5 min), the absorbance Germering, Germany) along with a Hypersil Gold C18 Column
was determined at 450 nm, 532 nm and 600 nm, and the MDA con- (100 mm×2.1 mm, 1.9 µm; Thermo Fisher Scientific, Waltham, MA,
tent was shown as µmol kg−1. USA). Samples (0.1 g) were ground in liquid nitrogen and placed
The H2O2 content was quantified via a previously reported in eppendorf (EP) tubes, and 500 µL of methanol aqueous solution
method with minor modifications (Dong et al., 2015). Fresh samples (80 per cent) with formic acid (0.1 per cent) was added. A certain
(2.0 g) were homogenized in 5.0 mL of precooled acetone and centri- amount of supernatant was diluted in mass spectrometry-grade water
fuged at 4 °C (12 000×g, 10 min). Second, the supernatant (0.1 mL), to a 53 per cent methanol concentration. Then, the supernatant was
titanium tetrachloride–hydrochloric acid (0.1 mL) and concentrated centrifuged at 15 000×g and 4 °C for 10 min. Finally, the supernatant
ammonia solution (0.2 mL) were mixed and centrifuged at 4 °C was gathered and analyzed by LC-MS/MS (Liu et al., 2019).
(12 000×g, 10 min). Finally, the precipitate was added to 3.0 mL of The chromatographic parameters were as follows: The mobile
2 mol L–1 sulfuric acid, and the A412nm value was recorded. The H2O2 phases A (0.1 per cent formic acid) and methanol (B) in positive-
content in the fresh weight samples was shown as µmol g–1. ion mode, and ammonium acetate (A, 0.05 mmol L–1, pH 9.0) and
The LOX activity was calculated based on (You et al., 2012) with methanol (B) in negative-ion mode, respectively. The column tem-
slight alterations. First, 2.0 g of potato sample was ground in 5 mL perature was 40 °C, and the flow rate was 0.2 mL min–1. The fol-
of 0.1 mol L–1 phosphate buffer (pH 6.8) consisting of 1 per cent lowing program was used: 98 per cent A and 2 per cent B (0–1.5 min),
Triton X-100 and 4 per cent PVPP. After blending, the mixed liquor 0 per cent A and 100 per cent B (1.6–14 min), then 98 per cent A and
was centrifuged at 4 °C (12 000×g, 30 min). Then, the reaction solu- 2 per cent B (14.1–17 min). All spectral data were recorded in the
tion consisting of 2.7 mL of 0.1 mol L–1 sodium phosphate buffer range of 70–1050 m/z. The electrospray ionization source was set
(pH 6.8) and 0.1 mL of 0.5 per cent linoleic acid solution was re- as follows: spray voltage, 3.2 kV; sheath gas flow rate, 40 arb; aux-
acted at 30 °C for 30 min. After heat preservation, 2 mL of the super- iliary gas flow rate, 10 arb; and capillary temperature, 320 °C. The
natant was added, and then, the A234nm was recorded for 3 min. The evaluation was executed in the positive ion and negative ion modes. The
LOX activity was shown as U g–1. molecular formulas were predicted by the molecular ion peaks and frag-
ment ions and also compared with the mz Cloud, mz Vault and Mass
CAT and SOD activities and the antioxidant capacity List databases. The background ions were removed by comparison with
A slightly modified method (Duan et al., 2011) was adopted to ana- blank samples, and the quantitative results were normalized. Finally,
lyze the CAT activity. Potato slices (2.0 g) were homogenized in data identification and quantitative results were obtained.
100 mmol L–1 sodium phosphate buffer (5 mL, pH 7.5) consisting
of 5 mmol L–1 dithiothreitol (DTT) and 5 per cent PVP. After cen-
Statistical analysis
trifugation at 4 °C and 12 000×g for 30 min, the reaction system
A randomized trial was designed, and the experiment was repeated
consisting of 2.9 mL of 20 mmol L–1 H2O2 solution and 0.1 mL of
three times. Experimental data were analyzed by one-way analysis of
supernatant was mixed. The A240nm values were measured for 3 min
variance in SPSS 24.0 (IBM Co., Armonk, NY, USA). The data were
immediately after mixing, and the data were recorded every 30 s.
shown as the mean value±standard deviation, and the significance
The CAT activity was shown as U g–1.
level was P
4 L. P. Qiao et al.
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Figure 1. Changes in the photographs of potato slices (A) and colour L* values (B), a* values (C), and ΔE* values (D) of potato slices under different treatments
of hawthorn leaf extract (0.00% (CK), 0.01%, 0.05%, and 0.1%) at 4 °C for 8 days. The lowercase letters in the figures indicate significant differences (PHawthorn leaf extract controlled the browning of potatoes 5
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Figure 2. Changes in the LOX (A) activity, contents of MDA (B) and H2O2 (C), antioxidant capacity by DPPH radical scavenging (D) and CAT (E), and SOD (F)
activities of potato slices under different treatments of hawthorn leaf extract (0.00% (CK), 0.01%, 0.05%, and 0.1%) at 4 °C for 8 days. The lowercase letters in the
figures indicate significant differences (P6 L. P. Qiao et al.
PPO, POD, and PAL activities and phenolic demonstrates that the phenolic compounds accumulated in a gradu-
accumulation ated manner and HLE limited this growth rate to a certain extent.
Enzyme activity (PPO, POD, and PAL) and phenolic content are vital A concentration effect was observed on day 4 (the first peak), and
contributors to enzymatic browning in fresh-cut products (Toivonen as the concentration increased, the phenolic content decreased. On
and Brummell, 2008). The activities of PPO and POD continuously day 8, 0.05 per cent HLE maintained the lowest content, which was
increased during the storage process, and HLE treatment signifi- approximately 34.2 per cent less than that of the CK slices.
cantly controlled them (Figure 3A and 3B). The 0.05 per cent con- The phenol accumulation and the activities of PPO, POD and
centration of HLE reduced the PPO and POD activities the most, PAL are highly correlated with the browning of minimally pro-
achieving activity reductions of 22.1 per cent and 17.2 per cent in cessed products (Fan et al., 2019). PPO is considered to be the crit-
PPO and POD, respectively, on day 8 compared to the control group. ical enzyme involved in enzymatic browning, which catalyzes phenol
The higher concentration (0.1 per cent) and lower concentration oxidation, quinine polymerization and dark pigment generation,
(0.01 per cent) weakly decreased these enzymatic activities. During which is why most antibrowning studies have applied theoretical
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refrigeration, the PAL activity peaked on day 2, and the HLE treat- methods to modulate PPO activity (Yu et al., 2014). Meanwhile,
ment diminished its activity to some extent (Figure 3C). Superior POD is found to participate in browning reactions via H2O2 during
inhibition was achieved by the 0.05% HLE treatment. On day 2 the PPO-catalyzed quinines (Toivonen and Brummell, 2008). Sikora
and day 8 the activities in the slices treated with 0.05 per cent HLE et al. (2019) observed that basil leaves and wheat bran extracts re-
were 28.8 per cent and 30.9 per cent lower than those of the control duced the enzymatic browning of shredded iceberg lettuce to the
slices, respectively (PHawthorn leaf extract controlled the browning of potatoes 7
Table 1. The main flavonoids, phenols and proanthocyanidins of hawthorn leaf extract analyzed by liquid chromatography–tandemmass
spectrometry (LC-MS/MS)
No. Name Formula Molecularweight Detection mode
1 Quercitrin C21H20O11 448.10 (–)
2 Apigenin C-pentoside C20H18O9 402.09 (+)
3 Eupatilin C18H16O7 344.09 (–)
4 Hesperetin 5-O-glucoside C22H24O11 464.13 (–)
5 3-Methoxyflavone C16H12O3 274.06 (+)
6 Liquiritin C21H22O9 418.13 (–)
7 Naringin dihydrochalcone C27H34O14 582.19 (–)
8 Naringin C27H32O14 580.18 (–)
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9 Rutin C27H30O16 610.15 (–)
10 Luteolin C15H10O6 286.05 (+)
11 Astilbin C21H22O11 450.12 (–)
12 Isoschaftoside C26H28O14 564.15 (+)
13 Myricetin C15H10O8 318.04 (+)
14 Trifolin C21H20O11 448.10 (+)
15 Neohesperidin C28H34O15 610.19 (–)
16 Apigenin-7-glucoside C21H20O10 432.10 (–)
17 Eriodictyol C15H12O6 288.06 (–)
18 Quercetin C15H10O7 302.04 (–)
19 Naringenin C15H12O5 272.07 (–)
20 1,2,3,7-Tetramethoxyxanthone C17H16O6 316.09 (+)
21 Kaempferol C15H10O6 286.05 (+)
22 Apigenin C15H10O5 270.05 (–)
23 Rhamnetin (7-O-methxyl quercetin) C16H12O7 316.06 (+)
24 4′,7-Di-O-methylnaringenin C17H16O5 300.10 (–)
25 Apigenin 6-C-glucoside C21H21O10 433.11 (+)
26 Puerarin C21H20O9 416.11 (+)
27 Genistein C15H10O5 270.05 (–)
28 Sinensetin C20H20O7 372.12 (+)
29 Nobiletin C21H22O8 402.13 (+)
30 Hesperetin C16H14O6 302.08 (+)
31 Amentoflavone C30H18O10 538.09 (–)
32 Tangeritin C20H20O7 175.07 (+)
33 Isochlorogenic acid C C25H24O12 516.13 (–)
34 d-(–)-Quinic acid C7H12O6 192.06 (–)
35 Vanillactic acid C10H12O5 212.07 (+)
36 Salicylic acid C7H6O3 138.03 (+)
37 Protocatechuic acid C7H6O4 154.03 (–)
38 Vanillic acid C8H8O4 168.04 (–)
39 Caffeic acid C9H8O4 180.04 (–)
40 Syringic acid C9H10O5 198.05 (–)
41 p-Coumaric acid C9H8O3 164.05 (–)
42 3-Coumaric acid C9H8O3 164.05 (–)
43 Chlorogenic acid C16H18O9 354.10 (–)
44 d-(+)-Phenyllactic acid C9H10O3 166.06 (–)
45 Sinapinic acid C11H12O5 224.07 (–)
46 2,4-Dihydroxybenzoic acid C7H6O4 154.03 (–)
47 2-Hydroxycinnamic acid C9H8O3 164.05 (–)
48 Salidroside C14H20O7 300.12 (–)
49 Methyl gallate C8H8O5 184.04 (–)
50 β-d-glucopyranosyl-caffeic acid C15H18O9 342.09 (–)
51 3,5-Dimethoxy-4-hydroxycinnamic acid C11H12O5 224.07 (+)
52 Benzoic acid C7H6O2 122.04 (–)
53 Cinnamic acid C9H8O2 148.05 (+)
54 trans-Cinnamic acid C9H8O2 148.05 (–)
55 Apocynin C9H10O3 166.06 (+)
56 Quinic acid C7H12O6 192.06 (+)
57 Hydrocinnamic acid C9H10O2 150.07 (–)
58 Catechol C6H6O2 128.05 (–)
59 Catechin C15H14O6 290.08 (–)
60 Theaflavins C29H24O9 516.14 (–)
61 4-Methylcatechol C7H8O2 124.05 (+)
62 Hyperin C21H20O12 464.09 (+)
63 Arbutin C12H16O7 272.09 (+)
64 Oleanolic acid C30H48O3 438.35 (+)
Detection mode: (+) positive mode and (–) negative mode.8 L. P. Qiao et al.
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Figure 4. The possible mechanism whereby treatments of hawthorn leaf extract alleviate the development of browning. HLE, hawthorn leaf extract; LOX,
lipoxygenase; MDA, malondialdehyde; CAT, catalase; SOD, superoxide dismutase; DPPH, 2,2-diphenyl-1-picrylhydrazyl; PPO, polyphenol oxidase; POD,
peroxidase; PAL, phenylalanine ammonia-lyase.
maximum activity of PAL perfectly coincides with the discoloration and membrane stabilization function. The antibrowning mechanism
of potatoes in different cultivars. In terms of phenol, it is generally of the HLE was collectively assumed as in Figure 4, which also needs
accepted that phenol accumulation accompanies browning develop- to be further explored.
ment (Dong et al., 2016). Liu and colleagues found that treatment
with cod peptides or purslane extract limited the browning intensity,
suppressed the activities of PPO, POD and PAL, and reduced the ac- Conclusion
cumulation of phenolic compounds in fresh-cut potatoes (Liu et al., The present research revealed that the application of HLE could
2018, 2019). Therefore, the controlled activities of PPO, POD and effectively control the browning of fresh-cut potatoes during cold
PAL and the fewer phenolics with the addition of HLE possibly help storage at 4 °C for 8 days. The addition of HLE not only enhanced
in retarding browning and maintaining brightness. the CAT activity and antioxidant activity but also controlled the
LOX activity and accumulation of MDA and H2O2. Meanwhile, the
Phytoactive composition of HLE activities of PPO, POD and PAL and the phenolic accumulation were
retarded by HLE treatment, and the medium concentration of 0.05
To explore why HLE could function as an antibrowning agent, sev-
per cent preserved the best color appearance with least browning
eral experiments were performed. First, the contents of total phenols
intensity. HPLC-MS/MS analysis revealed that HLE is rich in poly-
and total flavonoids in HLE were 1.52 and 0.86 g kg–1, respectively.
phenols, flavonoids and proanthocyanidins.
Second, HPLC-MS/MS was applied to analyze its main composition.
It is well known that some natural extracts such as tea are
As shown in Table 1, 64 flavonoids, phenolics and proanthocyanidins
famous for their phenol compounds, health benefits and homology
were identified in the positive and negative modes. There were
characteristic of being both a medicine and food. As another type
34 types of flavonoids and 25 types of phenols. Additionally, 5
of oriental magic leaf with a cheap cost, hawthorn leaves also con-
proanthocyanidins, including catechol, catechin, 4-methylcatechol,
tain many phytoactive polyphenols. HLE is a promising alternative
theaflavins and hyperin, were found. Furthermore, it has been docu-
antibrowning substance, which can not only preserve the appearance
mented that HLE maintains many functional polyphenols, which
and quality of fresh cuts but also help promote human wellness.
benefit the biological membrane. Alirezalu et al. (2018) stated that
vitexin, vitexin 2-O-rhamnoside and chlorogenic acid were the most
abundant phenolic compounds in HLE and could serve as natural Author Contributions
antioxidants for application in the food or pharmaceutical indus-
Liping Qiao contributed to conceptualization, methodology, and writing ori-
tries. Wloch et al. (2013) reported that procyanidins and epicatechin
ginal draft; Hailin Wang contributed to data curation, software, and validation;
were a dominant share of the HLE. They found that the HLE was
J.S. and L.L. contributed to writing, review and editing; Jinhu Tian contributed
mainly located in the hydrophilic region of the membrane, altered the to visualization and investigation; Xia Liu contributed to project administra-
packing order of the lipid polar heads, and effectively protected lipids tion and supervision.
extracted from the erythrocyte membrane against oxidation, which
all helped strengthen the cell membrane and made it more resistant
to stress. In addition, HLE could constitute a type of barrier that Funding
protected and strengthened the membrane without any side effects This project was sustained by the National Natural Science Foundation
(Włoch et al., 2013). Therefore, it is suspected that the antibrowning of China (No.32001765) and the Open Project Program of the State Key
effect of HLE resulted from the identified phytoactive compositions Laboratory of Food Nutrition and Safety, China (SKLFNS-KF-202016).Hawthorn leaf extract controlled the browning of potatoes 9
Conflict of Interest Liu, X., Lu, Y. Z., Yang, Q. (2018). Cod peptides inhibit browning in fresh-
cut potato slices: a potential anti-browning agent of random peptides.
The authors declare no conflict of interest.
Postharvest Biology and Technology, 146: 36–42.
Liu, X., Yang, Q., Lu, Y. Z., et al. (2019). Effect of purslane (Portulaca oleracea
L.) extract on anti-browning of fresh-cut potato slices during storage.
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