Food and Nutrition Sciences, 2013, 4, 1191-1200
Published Online December 2013 (http://www.scirp.org/journal/fns)
http://dx.doi.org/10.4236/fns.2013.412153
Open Access FNS
Effects of Pressurized Argon and Krypton Treatments on
the Quality of Fresh White Mushroom (Agaricus bisporus)
Camel Lagnika1,2, Min Zhang1*, Mohanad Bashari1, Fatoumata Tounkara1
1State Key Laboratory of Food Science and Technology, School of Food Science and Technology, Jiangnan University, Wuxi, China;
2Ecole Nationale des Sciences et Technique de Conservation et Transformation des Produits Agricoles de Sakété, Université d’Agri-
culture de Kétou, Kétou, Benin.
Received August 26th, 2013; revised September 26th, 2013; accepted October 4th, 2013
Copyright © 2013 Camel Lagnika et al. This is an open access article distributed under the Creative Commons Attribution License,
which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. In accor-
dance of the Creative Commons Attribution License all Copyrights © 2013 are reserved for SCIRP and the owner of the intellectual
property Camel Lagnika et al. All Copyright © 2013 are guarded by law and by SCIRP as a guardian.
ABSTRACT
Effects of argon, krypton and their mixed pressure treatments on the quality of white mushrooms were studied during 9
days of storage at 4˚C. Among all treatments in this study, the minimum respiration rate, polyphenoloxidase activity,
retained color change, antioxidants and delayed pseudomonas growth were observed with pressure argon (5 MPa) fol-
lowed by mixing argon and krypton (2.5 MPa each) treatments. Respiration rates after 9 days of storage were 5.35%,
6.20%, 7.50%, 7.60%, 7.91% and 8.95% for HA5, HAK, HA2, HK5, HK2 and control, respectively. DPPH inhibition
percentages of free radical for HA5, HAK, HK5, HA2, HK2 and control mushrooms were 28.03%, 25.24%, 24.96%,
21.87%, 20.56% and 19.06%, respectively, after 9 days of storage. The pressurized argon treatment was the most effec-
tive compared to pressurized krypton. Thus, application of pressurized argon and krypton treatments could extend the
storage life of white mushrooms to 9 days at 4˚C.
Keywords: Pressurized Argon; Krypton; Clathrate Hydrates; White Mushroom; Storage
1. Introduction
Production and consumption of mushrooms have been
gaining substantial ascendency in many parts of the
globe due to their deliciousness, flavor and overall nutri-
tional value. White mushroom (Agaricus bisporus) is
rich in acidic polysaccharides, dietary fiber, and antioxi-
dants including vitamins (C, B12, and D), folate, er-
gothioneine and polyphenol [1,2]. Due to these nutrients,
consumption of white mushrooms may have potential
anti-inflammatory, hypoglycemic and hypocholesterole-
mic consequences. Unfortunately, fresh mushrooms have
very short shelf life (3 to 4 days) compared to most other
vegetables at room temperature [3]. This might be due to
the fact that mushrooms do not have cuticles to protect
them from physical or microbial attack or water loss [4]
also because of their high respiratory rate. Postharvest
browning of Agaricus bisporus is a severe problem that
reduces the shelf-life. The most important factors that
determine the rate of enzymatic browning are the con-
centrations of active polyphenol oxidase (PPO) and phe-
nolic compounds present [5].
Moulds, bacteria, enzymatic activity and biochemical
changes can cause spoilage during storage. Gram-nega-
tive microorganisms, such as Pseudomonas bacteria,
have been associated with mushroom spoilage.
Thus, since mushrooms are highly perishable, they
need special care, especially during harvesting and stor-
age to retain freshness and overall quality.
Parameters such as visual appearance, respiration rate,
color, microbial growth and weight loss are usually used
to determine the quality of mushrooms [6]. Moreover,
the antioxidant status of fruits and vegetables is related to
its shelf life and may provide a useful indicator of the
quality during storage [7]. Various studies have demon-
strated that shelf life of fruits and vegetables is modu-
lated by antioxidants [8,9].
Recently, a great deal of interest has been shown in the
potential benefits of using argon in food preservation.
Many studies on the application of pressurized inert
gases in preserving fresh fruits and vegetables have been
*Corresponding author.

Effects of Pressurized Argon and Krypton Treatments on the Quality of Fresh White Mushroom (Agaricus bisporus) 1192
published [10-16]. Use of argon, a major component of
the atmosphere in modified atmosphere packaging (MAP)
has been reported to reduce microbial growth and im-
prove product overall quality retention [12,17]. Noble
gases dissolved in water under appropriately selected
temperature and pressure conditions, could result in the
formation of highly ordered “iceberg-like” structures
(called gas hydrate or clathrate) around solute molecules
in aqueous solution due to hydrophobic hydration [18].
At 0˚C, argon and nitrogen clathrate hydrates can form
and remain stable at more than 8.7 and 14.3 MPa respec-
tively [19]. Zhan and Zhang, 2005 [11] observed clath-
rate hydrates (structure-type I) using a mixture of argon
and xenon at a pressure range of 0.4 - 1.1 MPa in cu-
cumber samples. Ando et al., [20] examined the forma-
tion of the hydrate crystals of fresh-cut onions, which
were preserved under Xe pressure up to 0.8 MPa at 5˚C
for few hours. Purwanto et al., [21] found the formation
of gas hydrate in distilled water and coffee solutions at
8˚C and 0.70 MPa.
Fresh-cut vegetables and fruits pressurized in the pres-
ence of inert gases under appropriate conditions of pres-
sure and temperature, cause the inert gases to form hy-
drate in these fresh-cut material’s tissue and lower the
activity of intracellular water and inhibit the enzymatic
reactions. The combination of these two phenomena con-
tributes to the reduction of metabolism of fruits and
vegetables [10,12].
To the best of our knowledge, there are no reports of
scientific research works on the effects of combined
pressure argon and krypton treatments on the shelf life of
white mushrooms. Therefore, the present research was
designed to investigate the effects of pressurized argon
and krypton, as well as, the mixture of the two on the
physico-chemical, microbiological properties and sen-
sory quality of mushrooms during cold storage.
2. Materials and Methods
High-pressure equipment HCYF-3 (HuaAn Scientific
Instruments Co. Ltd., Jiangsu-China), commercially avail-
able argon and krypton of 99.7% purity (Wuxi Xinnan
Gas Co. Jiangsu-China) were used. Freshly harvested,
white mushrooms (Agaricus bisporus) were purchased
from a local market at Wuxi, China. All other chemicals
and solvents used were of analytical grade.
The freshly harvested mushrooms were transported to
the laboratory and selected base on uniformity of shape
and colour and free from mechanical damage. Mush-
rooms obtained were randomly divided into six groups,
and each group was samples (65 ± 5 g) at least three
times using glass jars. The different groups were sub-
jected to the following treatments:
 Control (C): mushrooms washed with distilled water
to remove soil then storage at 4˚C;
 pressurised argon (HA2): mushroom treated with Ar
under pressure 2.5 MPa at 4˚C for 1 h;
 pressurised argon (HA5): mushroom treated with Ar
under pressure 5 MPa at 4˚C for 1 h;
 pressurised krypton (HK2): mushroom treated with
Kr under pressure 2.5 MPa at 4 ˚C for 1 h;
 pressurised krypton (HK5): mushroom treated with
Kr under pressure 5 MPa at 4˚C for 1 h;
 pressurised mixed argon and krypton (HAK): mush-
room treated with mixed Ar and Kr under pressure
2.5 MPa each gas at 4˚C for 1 h.
Fresh mushrooms were placed in a high pressure
chamber, and then argon or/and krypton was passed into
the chamber after the evacuation time. After the pressur-
ized argon or/and krypton treatments, all samples were
stored at 4˚C with 90% relative humidity for 9 days.
Measurements and analyses of the mushrooms were
performed on the following days of storage period; 0, 3rd,
6th, and 9th day. Twelve replicates were included in each
treatment group, and subsequently every 3 days, three
replicates from each treatment group were analyzed. All
measurements were done in triplicates.
2.1. CO2 Production
Mushrooms (65 ± 5 g) were placed in 500 mL glass jars
and sealed with high gas barrier film then stored at 4˚C
for 9 days. Carbon dioxide production was measured on
the 3rd, 6th and 9th day of storage period using an O2
and CO2 Analyser (Cyes-II, Jiading federation Instru-
ment, Shanghai, China). Gas samples were taken from
the jars with a 20 mL syringe. Carbon dioxide production
(ΔCO2) was calculated as follows:


22f
CO %COCO
2i
(1)
where, CO2i is the gas concentration on the first day and
CO2f is the gas concentration on the final day of storage.
2.2. Weight Loss
Weight losses were determined by weighing of all
mushrooms contained in one package (initially 65 ± 5 g)
before and after the storage period, which was expressed
as weight loss percentage with respect to the initial
weight.




0f0
Weight loss %W WW100 (2)
where, W0 is the weight on the first day and Wf the
weight on final storage day.
2.3. Color
Surface color of mushrooms was measured with a Mi-
nolta spectrophotometer (CR-400, Konica Minolta Sens-
ing, Tokyo, Japan) using CIE color parameters L*
(light/dark), a* (red/green) and b* (yellow/blue) values.
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Effects of Pressurized Argon and Krypton Treatments on the Quality of Fresh White Mushroom (Agaricus bisporus) 1193
Three readings were taken at three equidistant points on
each mushroom cap. Numerical values of L* and color
difference (ΔE) were considered for the evaluation of
color modification of fresh mushroom. The value ΔE
defines the magnitude of total color difference and is
expressed by the equation [15]:

12
22
**** **
titi ti
ELL aa bb

 


2

(3)
where ΔE indicates the degree of overall color change in
comparison to color values of an ideal mushroom, Li*, ai*
and bi* represented the reading of fresh mushroom with-
out any treatments, and Lt*, at* and bt* referred to the in-
stantaneous individual readings during storage time after
the mushrooms were treated.
2.4. Polyphenoloxidase (PPO) Activity
Polyphenoloxidase (PPO, E.C. 1.14.18.1) activity in
mushroom, during the storage period was determined
according to the method proposed by Pizzocaro et al. [22]
with slight modifications. Fresh mushroom (10 g) was
ground in 10 mL of McIlvaine citric-phosphate buffer,
pH 6.5. The homogenate was centrifuged at 3000 × g at
4˚C for 30 min. The supernatant obtained was filtered
with Whatman no. 4 filter paper and analyzed for PPO
activity at 25˚C afterward. A 2 mL of catechol solution
(0.1%) and 2 mL of McIlvaine buffer pH 6.5 were added
to 0.1 mL of PPO extract. PPO activity was assayed in
triplicate using a spectrophotometer (UV-visible 2600,
Precision Science Instrument, Shanghai, China) at 420
nm and calculated on the basis of the slope from the lin-
ear portion of the curve plotted with ΔA420. One unit of
PPO was defined as the amount of enzyme present in the
extract that resulted in an absorbance increase of 0.001
units per minute. The activity was expressed in units of
PPO per minute and gram (U·min−1·g−1) of fresh mush-
room.
2.5. DPPH Free Radical-Scavenging Assay
The determination of free radical scavenging effect on 1,
1-diphenyl-2-picrylhydrazyl (DPPH) radical was carried
out according to the method of Alothman et al., [23] with
slight modifications. Mushroom samples (2 g) were ho-
mogenised with a mortar and pestle in 10 mL of metha-
nol and centrifuged at 6000 × g for 15 min at 4˚C and
filtered through a Whatman No 1 paper. Aliquots of 0.05
mL of the supernatant were mixed with 1 mL of DPPH
and 1.5 mL of Tris buffer. The homogenate was shaken
vigorously and kept in darkness for 30 min. The absorp-
tion of the samples was measured with the UV-visible
spectrophotometer at 517 nm against methanol as blank.
Results were expressed as percentage of inhibition of the
DPPH radical. Percentage of inhibition of the DPPH
radical was calculated according to the following equa-
tion:



00
DPPH radical scavenging activity %
100AAA

 

(4)
where, A0 is the absorbance of DPPH solution without
extracts and A is the absorbance of the mushroom ex-
tract.
2.6. Total Phenolic and Flavonoids Contents
Total phenolic contents were measured according to Sin-
gleton and Rossi [24]. Mushroom samples (5 g) were
crushed and homogenised in 50 mL methanol. The mix-
ture was centrifuged at 3000 × g for 30 min at 4˚C, fil-
tered with Whatman no. 4 filter paper and the mushroom
extract was collected. Mushroom extract (200 μL) was
mixed with 1.80 mL distilled water then 1 mL of Folin
and Ciocalteu’s phenol reagent was added. After 2 min, 2
mL of 20% sodium carbonate solution (Na2CO3) was
added. Thereafter, the reaction was allowed to proceed in
the dark for 90 min and absorbance was then read at 750
nm using the spectrophotometer. Gallic acid was used to
calculate the standard curve and the results were ex-
pressed as mg of gallic acid equivalents (GAE) per g of
extract fresh weight.
Flavonoids were extracted and determined according
to the methods of Barros et al. [25] with slight modifica-
tions. Namely, 1.8 mL of mushroom extract was added to
20 μL distilled water and 75 μL of 5% sodium nitrite
(NaNO2) then allowed standing for 6 min. Thereafter,
150 μL of 10% aluminium chloride (AlCl3) was added.
After standing for another 5 min, 2 mL of 1 mol·L−1 so-
dium hydroxide (NaOH) was added to the mixtures and
immediately their absorbance (pink in colour) was de-
termined at 510 nm. Rutin was used to establish the stan-
dard curve and the total flavonoids of mushroom were
calculated and expressed on a fresh weight as mg Rutin
equivalents (RUE) per g.
2.7. Microbiological Analysis
All samples were analyzed for the pseudomonas bacteria
counts. Mushrooms samples (10 g) were removed asep-
tically from each pack and diluted with 90 mL of 0.1%
sterile peptone water. The samples were homogenised by
a stomacher at high speed for 2 min. Serial dilutions
(10−1 - 10−8) were made in tubes (1.0 mL with 9.0 mL of
0.1% peptone water). Pseudomonas bacteria were
counted on cephaloridin fucidin cetrimide agar (CFC;
Difco), with selective supplement SR 103 (Oxoid). The
plates were incubated for 48 h at 25˚C and the number of
colony forming units per gram (CFU·g−1) of mushroom
was determined.
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Effects of Pressurized Argon and Krypton Treatments on the Quality of Fresh White Mushroom (Agaricus bisporus) 1194
2.8. Sensory Analysis
Sensory analysis of the mushroom was evaluated ac-
cording to Abdallah et al. and Conesa et al. [26,27] with
slight modifications on days 3, 6 and 9 by 10 semi-
trained recruited among students of the Food Science and
Technology, Jiangnan University. Sensory evaluation
was performed based on four aspects (color, aroma, tex-
ture and overall acceptability). The aspects were evalu-
ated on a scale of 9-1, where 9—excellent, 8—very good,
7—good, 6—fairly good, 5—satisfactory and limit of
marketability, 4—fair and limit of usability, 3—bad,
2—very bad and 1—extremely bad and inedible.
2.9. Statistical Analysis
Data were expressed as mean ± standard deviation (SD).
The Tukey’s test and one-way analysis of variance
(ANOVA) were used for multiple comparisons by the
SPSS 17.0 (SPSS, Chicago, Illinois, USA). Difference
was considered to be statistically significant if P < 0.05.
3. Results and Discussion
3.1. CO2 Production and Weight Loss
Changes of the CO2 production during storage under
different treatments at 4˚C are shown in Figure 1(A). As
can be seen from the figure a progressive increase in CO2
production during the entire storage period was observed
with all samples. At the end of storage time, CO2 produc-
tions were 5.35%, 6.20%, 7.50%, 7.60%, 7.91% and
8.95% for HA5, HAK, HA2, HK5, HK2 and control
samples, respectively. The results also demonstrated that,
argon or krypton treatment at 5 MPa showed lower CO2
production compared to that at 2 MPa. However, argon
treatments were significantly more efficient than krypton
treatments (P < 0.05).
The weight loss of the control sample was the highest
(1.04%) among the six treatments during the storage time
(Figure 1(b)). Samples treated by HA5 had significantly
lower weight loss than the other samples throughout the
storage (P < 0.05). The weight loss of the HAK, HA2,
HK5 and HK2 treatments increased progressively during
storage to a maximum of 0.95% for HK2 sample after 9
days, without significant differences among the HAK
and HA2 treatments. In our results, we observed a corre-
lation between CO2 production and weight loss. HAK
treated ones showed reduced weight loss and respiration
rate compared to samples with 2.5 MPa treatments and
the control. Therefore, the lowest CO2 production and
water loss observed in argon treatment could be related
to the highest solubility nature of argon which caused the
highest capability of gas hydrate formation compared to
krypton [28]. Argon hydrate is the most fundamental
clathrate hydrate in the sense that argon is spherical and
(a)
(b)
Figure 1. Changes in (a) CO2 production and (b) Weight
loss in white mushrooms during storage at 4˚C for 9 days
under different treatments (n = 3).
the smallest of the molecules which can be accommo-
dated in the clathrate cages and therefore, its interaction
with the lattice is the weakest [29].
3.2. Color
Browning after harvest is a common and economically
detrimental phenomenon in the mushroom industry,
which may have negative effect not only on the appear-
ance quality, but also on the flavor and nutrient composi-
tion.
All mushroom samples showed a decrease in white-
ness (L*), however, the color difference (ΔE) increased
during storage (Table 1). Compared to the control mush-
rooms, those treated had a higher L* (P < 0.05) and lower
ΔE (P < 0.05) values. Mushroom with HA5 and HAK
treatments followed by HK5, HA2 and HK2, respectively,
had a higher L* value than that of control during the 9
days of storage.
Color difference (ΔE) during storage differed among
treated ones with HA5 and HAK samples recording
lower color difference in contrast with HK5 followed by
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1195
Table 1. Colour changes of white mushrooms at different types of treatment during storage at 4˚C for 9 days.
Days 0 3 6 9
L
C 91.02 ± 1.66a 85.30 ± 0.66a 82.40 ± 0.33a 63.28 ± 1.43a
HA2 90.40 ± 0.69a 87.47 ± 1.66b 86.18 ± 0.84c 71.51 ± 1.03b
HA5 90.78 ± 1.69a 90.78 ± 1.43e 87.29 ± 1.06d 84.61 ± 1.21e
HK2 90.92 ± 0.27a 86.85 ± 0.33b 83.41 ± 1.16b 70.58 ± 0.16b
HK5 90.70 ± 0.97a 87.51 ± 1.04c 86.57 ± 1.34c 77.58 ± 1.36c
HAK 91.04 ± 0.52a 88.73 ± 1.31d 87.00 ± 0.96d 80.64 ± 2.01d
ΔE
C 3.89 ± 1.32a 9.52 ± 0.98a 13.08 ± 0.53a 30.09 ± 1.72a
HA2 4.20 ± 1.06a 8.42 ± 1.03b 8.62 ± 1.01c 25.30 ± 2.03b
HA5 4.35 ± 1.35a 4.73 ± 1.23e 7.49 ± 1.03d 11.03 ± 1.54e
HK2 4.44 ± 0.37a 8.46 ± 0.17b 12.07 ± 0.69b 25.62 ± 1.05b
HK5 4.44 ± 0.17a 7.40 ± 61.06c 8.30 ± 1.09c 19.13 ± 0.87c
HAK 4.33 ± 0.35a 6.54 ± 1.64d 7.94 ± 1.48d 15.80 ± 1.08d
Values are mean ± standard deviation of triplicates. Data in same column with different letters are significantly different (P < 0.05). Control (C): mushrooms
washed with distilled water to remove soil then storage at 4˚C; (HA2): 2.5 MPa pressure argon treatment at 4˚C for 1 h; (HA5): 5 MPa pressure argon treatment
at 4˚C for 1 h; (HK2): 2.5 MPa pressure krypton treatment at 4˚C for 1 h; (HK5): 5 MPa pressure krypton treatment at 4˚C for 1 h; (HAK): mixing argon and
krypton treatment at 2.5 MPa pressure each at 4˚C for 1 h.
HA2 and HK2 and control. Previously reported relation-
ship between different quality levels in mushrooms (A.
bisporus) and Hunter L-value provided a criterion for
classification [6,30]. Mushrooms with L-values greater
than 93 were classified as excellent sample, however,
that with L-values ranging between 90 to 93, 86 to 89, 80
to 85, and 69 to 79 were classified as very good, good,
fair and poor sample, respectively.
This criterion can be used as an indicator of mushroom
shelf life; for example mushrooms with an L-value less
than 80 would not be acceptable at wholesale level [31].
This grading method is the most frequently used indica-
tor of mushroom shelf-life both in the industry and re-
search [30]. According to that criterion [31], except the
HA5 and HAK samples, other samples had to be re-
jected.
3.3. Polyphenoloxidase (PPO) Activity
PPO plays an important role in the browning process of
many fruits and vegetables. Browning reactions are gen-
erally assumed to be a direct consequence of PPO actions
on polyphenols to form quinones, which ultimately po-
lymerize to produce the browning appearance of fruit and
vegetable [32]. PPO activity in white mushrooms in-
creased on the first day of storage and reached maximum
value on day 6 for all treatments and decreased during
the latter period afterward (Table 2). The lowest activity
was observed in HA5, HAK followed by HK5, HA2 and
HK2 treatment as compared to control. Mobility of water
is restricted by the formation of clathrate hydrates [33].
The lowest PPO activity observed with treated samples
compared to control could be attributed to the formation
of clathrate hydrate. This implied that, structured water
contributed into low water mobility which consequently
delayed the enzymatic browning. It’s also might be due
to the capacity of these gases to dissolve in the aqueous
layer of the mushroom through the cells of the flesh.
Therefore, they can inactivate some chemically-active
sites on the enzymes and/or reduce the level of dissolved
oxygen, whose presence is necessary for oxidative en-
zymes to catalyze metabolic reactions. Behnke [34] de-
monstrated that high pressure inert gases inhibited ty-
rosinase systems by decreasing oxygen availability rather
than by physically altering the enzyme. When noble
gases dissolve in water, enzymatic reactions are inhibited,
resulting in restrained vegetable metabolism [12].
3.4. DPPH Free Radical-Scavenging Assay
Changes during storage in the percentage of inhibition of
DPPH radical by antioxidants present in white mush-
room, are shown in Table 2. DPPH scavenging power of
the mushroom generally showed a reduction trend over

Effects of Pressurized Argon and Krypton Treatments on the Quality of Fresh White Mushroom (Agaricus bisporus) 1196
Table 2. Changes in polyphenoloxidase (PPO) activity and free radical scavenging effect on 1,1-diphenyl-2-picrylhydrazyl
(DPPH) of white mushrooms at different types of treatment during storage at 4˚C for 9 days.
Days 0 3 6 9
PPO activity (U·min−1·g−1)
C 3132 ± 3.56a 3851 ± 8.02a 4496 ± 7.23a 4275 ± 9.20a
HA2 3132 ± 3.56a 3673 ± 3.24b 4229 ± 4.67b 3863 ± 2.65c
HA5 3132 ± 3.56a 3210 ± 1.45e 3809 ± 2.56c 3155 ± 5.63f
HK2 3132 ± 3.56a 3826 ± 2.34a 4449 ± 5.65a 4143 ± 4.65b
HK5 3132 ± 3.56a 3394 ± 6.12c 4200 ± 4.34b 3781 ± 2.64d
HAK 3132 ± 3.56a 3488 ± 5.32d 4037 ± 1.54c 3451 ± 6.34e
DPPH (%)
C 40.61 ± 0.64a 31.29 ± 0.81a 27.51 ± 0.76a 19.06 ± 0.53a
HA2 40.61 ± 0.64a 32.02 ± 0.68b 30.29 ± 0.81c 21.87 ± 0.44d
HA5 40.61 ± 0.64a 37.55 ± 0.37d 34.30 ± 0.27f 28.03 ± 0.76f
HK2 40.61 ± 0.64a 31.24 ± 0.63a 28.54 ± 0.57b 20.56 ± 0.16b
HK5 40.61 ± 0.64a 31.94 ± 0.78b 31.18 ± 0.14d 24.96 ± 0.84c
HAK 40.61 ± 0.64a 35.02 ± 0.68c 32.22 ± 0.68e 25.24 ± 0.59e
Values are mean ± standard deviation of triplicates. Data in same column with different letters are significantly different (P < 0.05). Control (C): mushrooms
washed with distilled water to remove soil then storage at 4˚C; (HA2): 2.5 MPa pressure argon treatment at 4˚C for 1 h; (HA5): 5 MPa pressure argon treatment
at 4˚C for 1 h; (HK2): 2.5 MPa pressure krypton treatment at 4˚C for 1 h; (HK5): 5 MPa pressure krypton treatment at 4˚C for 1 h; (HAK): mixing argon and
krypton treatment at 2.5 MPa pressure each at 4˚C for 1 h.
the 9 days storage time in all samples but at different
extent. However, all the treated samples delayed in the
decrease but at different degrees, with significant differ-
ences (P < 0.05) in DPPH scavenging power between the
treated samples and the control. After 9 days of storage,
percentage of inhibition of DPPH radical for HA5, HAK,
HK5, HA2, HK2 and untreated mushrooms were 28.03%,
25.24%, 24.96%, 21.87%, 20.56% and 19.06% respec-
tively. It was observed that, high pressure argon could
delay the reduction of antioxidant capacity of mushroom
during the refrigerator storage, probably due to noble gas
hydrate formation and residual gas in micropore of fruit
tissue.
3.5. Total Phenolic and Flavonoids Contents
In this study, total phenolics levels declined in all treat-
ments during the 9 days of storage (Table 3). However,
pressurized argon (5 MPa) was more effective in delay-
ing decrease of phenolics than other samples. Mush-
rooms treated samples presented a higher level of total
phenolics, compared to control.
Similar to total phenolics, all the treatments showed a
reduction in flavonoids contents during storage (Table 3).
However, HA5 and HAK treatments appeared to be sig-
nificantly (P < 0.05) efficient in delaying the reduction in
flavonoids in the white mushrooms as compared to other
treatment. Whereas, untreated white mushrooms pre-
sented a lower level of flavonoids, all treatments affected
significantly (P < 0.05) the flavonoid content in white
mushrooms during the 9 days.
It demonstrated that, HA5 and HAK treatments were
significantly effective in maintaining the total phenolic
and flavonoids compounds, which might be due to clath-
rate hydrate formation that inhibited the enzyme activity
of phenolic and flavonoids compounds degradation. The
pressurized argon treatment was the most effective in
delaying the reduction in total phenolics and flavonoids
content compared to pressurized krypton may be due to
the high solubility of argon.
3.6. Microbiological Analysis
Figure 2 presents growth of pseudomonas bacteria (ex-
pressed as log CFU·g−1) of fresh mushroom during 9
days of storage at 4˚C. Gradual growth of microorgan-
isms was seen during storage in all samples. However,
some treatments retarded the microbial growth more than
others. The highest amount of microorganisms was ob-
served in control samples. Pressurized argon samples (5
Mpa) followed by combined of argon-krypton and HK5
samples, were found to be effective in delaying pseudo-
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Effects of Pressurized Argon and Krypton Treatments on the Quality of Fresh White Mushroom (Agaricus bisporus) 1197
Table 3. Changes in functional components in white mushrooms during storage at 4˚C for 9 days under different treatments.
Days 0 3 6 9
Total phenolics (min·g−1)
C 1.03 ± 0.92a 0.90 ± 0.63a 0.62 ± 0.10a 0.43 ± 0.18a
HA2 1.03 ± 0.92a 0.99 ± 0.17bc 0.75 ± 0.25b 0.63 ± 0.16d
HA5 1.03 ± 0.92a 1.02 ± 0.15c 0.89 ± 0.34e 0.76 ± 0.32f
HK2 1.03 ± 0.92a 0.97 ± 0.23b 0.77 ± 0.32c 0.50 ± 0.71b
HK5 1.03 ± 0.92a 0.98 ± 0.43bc 0.77 ± 0.45c 0.58 ± 0.58c
HAK 1.03 ± 0.92a 1.01 ± 0.68c 0.85 ± 0.30d 0.74 ± 0.63e
Total flavonoids (min·g−1)
C 0.71 ± 0.44a 0.50 ± 0.36a 0.38 ± 0.46a 0.25 ± 0.36a
HA2 0.71 ± 0.44a 0.57 ± 0.56c 0.46 ± 0.34c 0.33 ± 0.32c
HA5 0.71 ± 0.44a 0.66 ± 0.14d 0.54 ± 0.17e 0.40 ± 0.37d
HK2 0.71 ± 0.44a 0.51 ± 0.44ab 0.41 ± 0.32b 0.29 ± 0.43b
HK5 0.71 ± 0.44a 0.53 ± 0.65b 0.43 ± 0.45bc 0.30 ± 0.48b
HAK 0.71 ± 0.44a 0.61 ± 0.35cd 0.50 ± 0.33d 0.34 ± 0.23c
Values are mean ± standard deviation of triplicates. Data in same column with different letters are significantly different (P < 0.05). Control (C): mushrooms
washed with distilled water to remove soil then storage at 4˚C; (HA2): 2.5 MPa pressure argon treatment at 4˚C for 1 h; (HA5): 5 MPa pressure argon treatment
at 4˚C for 1 h; (HK2): 2.5 MPa pressure krypton treatment at 4˚C for 1 h; (HK5): 5 MPa pressure krypton treatment at 4˚C for 1 h; (HAK): mixing argon and
krypton treatment at 2.5 MPa pressure each at 4˚C for 1 h.
Figure 2. Growth of pseudomonas bacteria of fresh mush-
room during 9 days of storage at 4˚C under different treat-
ments (n = 3).
monas bacteria growth in mushroom during the 9 days of
cold storage. For HA2 and HK2 treatments, no signifi-
cant (P < 0.05) difference was observed during the stor-
age. In food, microbial growth is closely related to the
water activity of those products and can be delayed by
pressurized inert gases. The inhibitory effect of pressur-
ized gases treatment on microbial growth in white
mushroom might be owned to clathrate hydrates forma-
tion, which reduced water activity and remained gas in
the micropore mushroom to reduce the growth of micro-
organism.
3.7. Sensory Analysis
Figure 3 shows the sensory evaluation including color,
aroma, texture and overall preference of the six treat-
ments for the three typical storage days. On day 3, all the
treatments showed a moderate decrease in the overall
quality. As expected, color, aroma, texture and overall
acceptability significantly changed (P < 0.05) with stor-
age time, supporting the validity of using these parame-
ters as indicators of mushroom deterioration. As the
storage time progressed to day 6, there was a continued
decrease in sensory quality. On day 9 of storage, consid-
ering the development of the evaluated sensory attributes,
HA5 mushrooms showed the lowest deterioration rate,
followed by HAK, HK5 and HA2. On the other hand,
control and HK2 samples reached a score lower than 5 a
value that is below the borderline of acceptability and
marketability.
4. Conclusion
Compared to the untreated (control) samples, treated
samples had significantly (P < 0.05) longer shelf-life.
The argon treatment delayed quality deterioration, re-
duced the loss of water, exhibited the smallest respiration
rate, retained mushrooms color change, showed smaller
Open Access FNS

Effects of Pressurized Argon and Krypton Treatments on the Quality of Fresh White Mushroom (Agaricus bisporus) 1198
(a)
(b)
(c)
Figure 3. Sensory characteristics of fresh mushroom of six
treatments stored for 3, 6 and 9 days at 4˚C. Values repre-
sent the means of the replicates and error bars represent
the standard error of the means (n = 3).
polyphenoloxidase activity, retained antioxidants, de-
layed pseudomonas growth and maintained sensory qual-
ity compared to krypton treatment. Our research showed
that pressurized argon and mixed argon-krypton may be
a useful way of maintaining quality and extending the
shelf-life of white mushroom.
5. Acknowledgements
The authors are grateful to China National Natural Sci-
ence Foundation for supporting this research under con-
tract No. 30972058.
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