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AMERICAN-EURASIAN JOURNAL OF SUSTAINABLE
AGRICULTURE ISSN: 1995-0748, EISSN: 1998-1074
2017, volume(11),issue(4):pages(8-22)
Published Online July 19 2017in http://www.aensiweb.com/AEJSA/
AMERICAN-EURASIAN JOURNAL OF SUSTAINABLE AGRICULTURE. 11(4) July 2017, Pages: 8-22
KarinaJuhnevica-Radenkova, Vitalijs Radenkovs and Dalija Seglina, 2017
Effect of storage technology on structure and physical attributes of apples (Malus × domestica Borkh.)
1Karina Juhnevica-Radenkova, 2Vitalijs Radenkovs and 3Dalija Seglina
1KarinaJuhnevica-Radenkova, researcher, Processing and Biochemistry Department, Institute of Horticulture, Latvia University of Agriculture, Dobele, Latvia. 2Vitalijs Radenkovs, researcher, Processing and Biochemistry Department, Institute of Horticulture, Latvia University of Agriculture, Dobele, Latvia. 2Dalija Seglina, leading researcher, Processing and Biochemistry Department, Institute of Horticulture, Latvia University of Agriculture, Dobele, Latvia. Received 12 March 2017; Accepted 20 June 2017; Published Online 19 July 2017
Address For Correspondence: Vitalijs Radenkovs, Institute of Horticulture, Latvia University of Agriculture,Processing and Biochemistry Department, LV-3701
Latvia, Dobele, Latvia
E-mail: [email protected]
Copyright © 2017 by authors and American-Eurasian Network for Scientific Information.
This work is licensed under the Creative Commons Attribution International License (CC BY).
http://creativecommons.org/licenses/by/4.0/
ABSTRACT Apples (Malus × domestica Borkh.) are a popular temperate fruit, consumed both fresh and processed, and they ranked third for global fruit production at 80.8 million tonnes in 2013. Global production is centred on the high-value fresh market, which requires maintain
fruit quality during long-term storage and shipping.In this study, six frequently grown and commercially available cultivars of apples
grown in Latvia were chosen to evaluate the influence of 1-Methylcyclopropene treatment and Ultra-low oxygen conditions on the changes of structural and physical parameters of apple fruits while long-term storage. Experiments have been carried out during the
period from 2013 to 2014 at the Processing and Biochemistry Department of the Institute of Horticulture, Latvia University of
Agriculture in Dobele. From the results is evident that better preservation of fresh weight loss has been obtained for samples kept in the ULO2 with a controlled atmosphere. Our findings disclose that ULO1 and ULO2 maintained the fruit firmness better than cold storage.
Results obtained after SEM analysis showed that Ultra-low oxygen storage has resulted in less pronounced de-compartmentalisation of
apple matrix, nevertheless cellular membrane cracking and collapse as part of the normal metabolism of the product was evident. Furthermore, ULO storage has affected on better cohesion and higher compressibility of the cells found in apple. A significant positive
effect of 1-MCP on cell integrity was also evident, where cell wall disassembly in many cases was more pronounced when apples were
kept for a long-term storage under cold storage. Besides, there was significant difference in cell size loss among all storage technologies while fruit storage, the changes were considerably slower in ULO1 storage than in other techniques applied.
KEY WORDS surface area;1-methylcyclopropene; structure;apple matrix
INTRODUCTION
Apples are one of the most produced and consumed fruits in the world. Apples available throughout
the food chain have different quality. Fruit quality is determined by several factors, including storage
period, storage conditions, stage of maturity, size of fruits and cells.1-Methylcyclopropene (1-MCP) is an
inhibitor of ethylene perception that can delay or prevent ripening and senescence processes in plant tissues
[39]. The commercialization of 1-MCP as Smart FreshTM and Ethylbloc® for horticultural and food products,
respectively, has had a major effect on many horticultural industries around the world. 1-MCP has several
features that have resulted in its rapid approval by regulatory authorities around the world – it is a gaseous
substance that is easily applied, it has a non-toxic mode of action, negligible residues, and activity at very low
concentrations [4]. By 2011, more than 40 countries had approved the use of 1-MCP as ethylene inhibitor for a
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wide type of climacteric fruits and vegetables including apple, pear, banana, avocado, kiwi fruit, Brussels
sprouts, carrot, cabbage, cucumber and many other ornamental crops [51].
The apple storage in ULO maintains higher flesh firmness, lower physiological disorders, such as
superficial scald [37,55], flesh breakdown and mealiness [53]. These benefits increased significantly the storage
of apple in ULO within the last few years, becoming, along with CA, one of the storage techniques most
used.Qualitative attributes, such as structure, firmness, generally change while storage, as part of the normal
metabolism of the product [45]. Low temperature is the most important factor in maintaining quality and
extending the cold storage and shelf-life of fruits and vegetables after harvest. Most of the physiological,
biochemical and microbiological activities contributing to the deterioration of produce quality are largely
dependent on temperature [46]. However, gas compositionof the ambient air also plays an important role. Long-
term storage period of fruits may be extended through reduced O2 and elevated in CO2, by means of controlled
atmosphere [3,17,41] that slows deterioration intensity and reduces ethylene production, thereby reducing
metabolic activity in terms of respiration [49].According to findings found in literature, it is evident that
controlled atmosphere including ULO storage is an ideal preservation technique that provides an appropriate
environment conditions for long-term fruit storage [34], besides controlled atmosphere storage coupled with
low-temperature storage, can reduce respiration and ethylene synthesis rates; by that, preserve softening of the
fruits along with the changes related to ripening and senescence [1,18,36]. Fresh produce continues to lose water
after harvest, resulting in increased weight loss within long-term storage [31]. In addition, it has been reported
earlier that percent weight loss generally increased with increasing storage duration. The weight loss in fruit
depends on the nature and amount of waxy on the surface, storage type [48], and specific surface area of the
cells [25]. Therefore, it is necessary to define the quality attribute changes of the apples stored under different
environment conditions. Thus this research examines the influence of 1-Methylcyclopropene treatment and
Ultra-low oxygen conditions on the changes of structural and physical parameters of apple fruits while long-
term storage.
MATERIALS AND METHODS
Research Time and Place:
The research has been carried out from 2013 to 2014 at the Processing and Biochemistry Department of the
Institute of Horticulture, Latvia University of Agriculture in Dobele.
Materials used for Research:
Following apple cultivars had been chosen for experiments – autumn cultivars: 'Auksis', 'Orlik', and winter
cultivars: 'Antej', 'Belorusskoje Malinovoje', 'Sinap Orlovskij' and 'Zarja Alatau'. All apple trees were grafted on
the rootstock B9 and grown in the orchard according to an integrated system at the same conditions. All apple
fruits have been harvested according to Commission regulation (EC) No 1221/2008 (2008) that establishes a
standard of the fruits intended to be supplied fresh to the consumer. All apple fruitswere characterised as
“Extra” class. Ripening stage of the fruits were assessed by starch index using Starch-iodine test and Streifs’
index,
SISSC
Findex Streifs'
where: F – firmness, kg cm-2; SSC – soluble solids content (TSS), °Brix; SI – starch index (on a scale from
1 to 10). Harvested fruits met the requirements for fruits intended for long term storage in Latvia(Drudze, 2003,
2005). Shortly after harvesting, apples were air-cooled for 24 hours in a cooling chamber at up to +4 ± 0.5°C.
Thirty kg of fruits were sampled per storage technology and placed by 10 kg in polypropylene, perforated boxes.
The cooled down apples were divided into four groups for post-harvest storage: 1)cold storage at 2 ± 1°C with
relative humidity 85% – control, apples were stored under normal atmosphere; 2) cold storage + 1-MCP, apples
after treatment with 1-methylcyclopropen were stored under normal atmosphere; 3)ULO1 –2.0% CO2, 1.0% O2
with relative humidity 85%; 4) ULO2 –2.5% CO2, 1.5% O2 with relative humidity 85%. Storage in ULO was
implemented in Fruit Control Equipment (Italy) by selecting two different gas compositions. Apples were
maintained in the above experimental condition for six months.
1-MCP powdery substance (purchased from Rand H: Rohm and Haas Company, Italy) was dissolved in
warm water +50 ± 2°C by the ratio of 1:30, to the concentration 0.625 μl L-1 according to [52]. The solution was
prepared in an Erlenmeyer flask and placed in an air-tight processing container with apples intended for storage.
The treatment with 1-MCP was performed at a temperature of 4 ± 0.5°C for 24 h. After treatment, fruit samples
were stored in cold storage under normal atmosphere conditions.
Physical analysis:
Fresh weight loss determined with scaling method provided by [32].
10
100 weightInitial
weightfinal weightInitiallossht Fruit weig
Ten fruitswere used analysis of flesh firmness (kg cm-2). It was measured on twoopposite sides of each
apple without skin (n=20), using digital penetrometer (model TR 53205, Italy), which was equipped with 11
mm diameter probe; peak destructive force was expressed in kilogram per square centimetre (kg cm-2).
Scanning electron microscope (SEM) analysis was performed with a Tescan Mira/LMU scanning electron
microscope(Zambrano-Zaragoza et al., 2014)operating in low vacuum mode (PH2O = 0.1–1.0 torr) using a large
field detector (LFD) and in environmental mode (ESEM, PH2O = 1.0–4.8 torr) using a gaseous secondary
electron detector (GSED). Four specimens about 1 mm thick were cut from apple parenchyma tissues. For the
low vacuum analysis, they were mounted onto SEM stubs by means of double-sided adhesive carbon discs and
observed at 10–20 kV acceleration voltage. For the ESEM analysis, specimens were placed on the cooling stage
setting the temperature at 1 °C and observed at 20–30 kV acceleration voltage.The SEM analysis has been
performed in triplicate for all cultivars selected. In order to improve the sample electrical conductivity and their
ability to reflect electrons and hence provide clear images, all samples were being covered with gold prior to
analysis with a SEM.
Statistical analysis:
Data analysis was carried out using the General Linear Model functions in the IBM® SPSS® Statistics
program 20.0 (SPSS Inc., Chicago, Illinois). The obtained data were analysed using descriptive statistics.
Significant differences determined using UNIANOVA, by Least Significant Difference (LSD) criteria. The
analysis was done considering the main factor influence (storage conditions) on fruit quality. The significance of
differences was determined at p<0.05. Mean and standard deviation values were calculated for all parameters.
RESULTS AND DISCUSSION
Maturity stage of apples at harvest:
To determine whether fruits are ready to harvest many physical parameters must be determined before
harvesting: flesh firmness, total soluble solids and acids content, ethylene concentration, sensory parameters,
Iodine-starch test [40]. The Iodine-starch test is required to correct prognostication of harvesting date [35].
Table 1: The parameters characterizing the maturity stage of apples at harvest
Cultivar Harvesting date Iodine-starch test
(1-10) Streif index
'Auksis' 10/09 3.50b 0.16ab
'Orlik' 10/09 3.50b 0.15ab
'Antej' 14/09 4.50a 0.11b
'BelorusskojeMaļnovoje' 14/09 3.70b 0.18a
'SinapOrlovskij' 21/09 4.00ab 0.19a
'ZarjaAlatau' 26/09 4.30a 0.14b
Note: Value within the same cultivar followed by different small letters are significantly different at p≤0.05 (LSD test).
Based on literature it is seen that cultivar such as 'Auksis' considered to be ready for harvest when the index
is 5.0, while 'Orlik' cultivar is ready for harvest at index 4.0, 'SinapOrlovskij' cultivar at 4.0-4.8, but
'ZarjaAlatau' at 4.5-6.7 [20]. However, it is well-known that the harvesting time differs for every cultivar
depending on the results of iodine-starch test, for example, for 'Elstar' it is 5.0, but for ‘Golden Delicious’ it is
8.0 [5]. Results obtained after Iodine-starch index calculation(Table 1) disclose that cultivar of 'Auskis', 'Orlik',
and 'BelorusskojeMalinovoje' fruits at harvest were close to optimal maturity stage, while cultivar of
'SinapOrlovskij' and 'ZarjaAlatau' appleshad optimal index at harvest [19]. Within this paper Streif index
calculation has been also used to estimate the time of optimal harvest for apple cultivars grown in Latvia. As can
be seen,Streif index fluctuated in a range from 0.11-0.19. Our results are similar to those found in the literature
[20]. Thus, the most optimal harvesting time in terms of the Streif index are second time.
Microstructure of apple parenchyma cells and diameter:
Fruit size is an important commercial trait in crops such as apple (Malus × domesticaBorkh.) [27], however
according with a several reports found in literature, is evident that large fruit have the highest incidence of flesh
breakdown, cracking [25,26], those fruits may soften more rapidly compared with small fruit when harvested at
advanced maturity. To the best of our knowledge, this is a first report that examines the effect of long-term
storage under different environmental conditions on cell structure of apples. As can be seen from micrographs
(Fig. 1 to 6, b) apple fruits those before storage have a well-organised structure in a homogeneous and
anisotropic pattern with a high degree of cellular compartmentation, where intracellular space can also be
observed. However, after the storage of apples for six months, particularly under normal atmosphere conditions
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(control samples) several structural changes of cellular integrity and specific area of the cells can be observed.
In many cases significant de-compartmentation of the cells, their collapse, shrinkage, and blurring are
observed.Modification of the cell matrix particularly result from the action of cell wall modifying enzymes (e.g.
polygalacturonase, pectin methylesterase, pectate lyase, β-galactosidase, cellulase), generally encoded by
ripening-related genes [13]and moisture loss [2].Modifications caused by the activity of endogenous enzymes
such as pectin lyase, pectin methylesterase, β-galactosidase may lead to solubilisation of insoluble forms of
pectic substances, and hemicellulose [11,15], resulting in a significant softening of fruits [15,51]. The
conversion of water insoluble compounds into soluble forms also favoursto intense weight loss by the water
transpiration process. Thus leading to turgor pressure loss [15,47]. A significant difference was observed when
apples were kept for a long-term storage in combination with 1-MCP treatment. As can be seen from
micrographs (Fig.1 to 6, m),disintegration of the cells in many cases are less pronounced, however,membrane
collapse and cracking arestill evident.The deterioration of cell matrix can be explained by the presence in a
lower rate of exo- and endogenous enzymes that are able to split long-chain polymers [16]. There are very few
reports on the effect of 1-MCP on cell integrity. Several studies have examined the effect of ethylene inhibitor
(1-MCP) on the quality of fruits. Supapvanich and Tucker [42],have noted that 1-MCP has inhibited
polygalacturonase, β-galactosidase and β-galactanase activities of fresh cut muskmelon
(Cucumismelovarreticulatus L.), while Kawakami and colleagues [22]have shown that 1-MCP increased the
activity of the antioxidant enzymes glutathione reductase and superoxide dismutase in water-stressed plants.
These effects significantly increased protein concentration and maintained cell membrane integrity. Chiriboga et
al. [6] stated that1-MCP-treated fruit exhibited higher superoxide dismutase (SOD) and catalase (CAT) activity,
together with higher ascorbic acid levels during cold storage of pears.Analysing the data after long-term apple
storage under ultra-low oxygen conditions, structural alterationin terms of cell integrity is evident (Fig. 1 to 6
u1, u2). As can be seen, controlled atmosphere storage has resulted in less pronounced de-compartmentalisation
of apple matrix, nevertheless, cellular membrane cracking and collapse as part of the normal metabolism of the
product was evident (Fig. 2, 3, 4, 6 u1 and u2).Due to lack of scientific papers, concerning influence of storage
conditions on cell structure of apples, not possible to compare the results obtained within this research. Some
papers have been found, which examines interaction of storage conditions, and the fracture force (firmness)of
fruits measured by texture analyses [46]. Authors pointed out on positive effect of controlled atmosphere storage
on cultivar 'Honeycrisp' apple cell integrity maintenance. In turn, Watkins and Nock [50]andFonseca et al.
[13]declared that no effect has been achieved with regards to firmness and cellular disassembly of apple and
pear, respectively.
1b
1c 1m
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Fig. 1: Scanning electron micrograph of cross section of 'Auksis', parenchyma cells
Note: Small letters imply: (b) before storage; (c) cold storage; (m) 1-MCP treated; (u1) ULO1;
(u2) ULO2
Fig. 2: Scanning electron micrograph of cross section of 'Orlik'parenchyma cells
Note: see Fig. 1.
2
c
2
m
2
u
1
2
u
2
2c 2m
2u1 2u2
2b
1u1 1u2
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Fig. 3: Scanning electron micrograph of cross section of 'Antej' parenchyma cells
Note: see Fig. 1.
3c 3m
3u1 3u2
3b
4b
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Fig. 4: Scanning electron micrograph of cross section of 'Belorusskoje Malinovoje' parenchyma cells
Note: see Fig. 1.
4c 4m
4u1 4u2
5c 5m
5b
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Fig. 5: Scanning electron micrograph of cross section of 'Sinap Orlovskij' parenchyma cells
Note: see Fig. 1.
Fig. 6: Scanning electron micrograph of cross section of 'Zarja Alatau' parenchyma cells
Note: see Fig. 1.
Anatomical features such as cell wall and cuticle thickness, cell size, as well asthe distribution of
intercellular gas spaces greatly influence consumer perception of applestructure [38,47].Due to a presence of
intercellular gas and water spaces, there is a high risk of quality deterioration and microorganism development
[34]. Taking into account above-mentioned statement, it is important to draw a line between cell and fruit size
and deterioration incidence. Data depicted in Table 2disclose that the largest cells have been found in a sample
6c 6m
6u1 6u2
6b
5u1 5u2
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'Orlik' (215.15 µm, before storage), while the smallest cells in cultivar 'BelorusskojeMalinovoje' (166.01 µm,
before storage). The same results have been provided by the group of scientists who examined the
microstructure of eight selected cultivar of apples. Scientists stated that ripened fruit parenchyma cell diameter
fluctuates in a range between 50 and 500 micrometres [24]. According to the statement, provided by
[27]appears, that larger fruit can be comprised of larger cells, while Mann and colleagues pointed out that larger
cell size is associated with reduced cell number per unit area [28]. Our results indicate exact opposite, that there
were no found a positive correlation (r=-0.624) between the size of cells and fruits. Besides, wasnoted that
large-sized fruits have smallest cells. It is seen, that cell size of cultivar 'Auksis' and 'Orlik' apples those kept
under normal atmosphere conditions (Fig. 1 to 6 c - control storage, Table 2 and Table 3) reduced considerably
by 7.75% and 30.02%, respectively. On the other hand, significant cell expansion was also evident for cultivar
of 'BelorusskojeMalinovoje' and 'ZarjaAlatau' apples by 13.61% and 12.31%, respectively.
Table 2: The size of cellsand apples stored under different conditions, µm
Cultivar Storage technology Average size of cells before storage
Average size of cells after six
months storage
Average fruit size
'Auksis'
Cold storage
185.03bA±24.62
170.68aB±36.81
Medium size fruits:
70 mm diameter
Cold storage + 1-MCP 112.24cC±34.69
ULO1 161.76bD±33.28
ULO2 160.47bE±47.81
'Orlik'
Cold storage
215.15aA±32.67
150.56bB±76.58
Small size fruits:
60 mm diameter
Cold storage + 1-MCP 160.91aC±64.64
ULO1 124.45dD±43.60
ULO2 147.87cE±63.02
'Antej'
Cold storage
175.06cA±25.85
182.61dB±23.89
Large size fruits:
75 mm diameter
Cold storage + 1-MCP 221.37bC±44.67
ULO1 211.93aD±63.84
ULO2 185.67cE±75.49
'BelorusskojeMalinovoje'
Cold storage
166.01dA±31.21
188.61bB±63.19
Small size fruits: 65 mm diameter
Cold storage + 1-MCP 152.15cC±28.75
ULO1 223.16aD±37.79
ULO2 139.02dE±22.04
'SinapOrlovskij'
Cold storage
176.54cA±24.12
148.90dB±40.37
Large size fruits:
75 mm diameter
Cold storage + 1-MCP 190.86bC±34.88
ULO1 166.56cD±39.87
ULO2 232.02aE±80.03
'ZarjaAlatau'
Cold storage
177.69cA±20.01
199.57aB±43.51
Small size fruits:
65 mm diameter
Cold storage + 1-MCP 172.62bC±35.73
ULO1 171.87bD±36.95
ULO2 144.42cE±22.93
Note: Mean value with standard deviation (±) within the same cultivar followed by different small letters are significantly different at p≤0.05 (LSD test).
Mean value with standard deviation (±) within the same cultivar followed by different capital letters are significantly different at p≤0.05
(LSD test).
Cell expansion during apple storage can be caused by the enzymes expansins. Expansins are plant cell wall-
loosening proteins, which are responsible for many physiological processes, in particular, to promote cell
growth as well as by cleaving hydrogen bonds between cellulose and hemicellulose, enables others cell-wall-
degrading enzymes get to substrates [14,28,30]. Having to regardthe results obtained after long-term apple
storage in combination with 1-MCP, it is seen that cell diameter fluctuated in a range from 112.24 ('Auksis') to
221.37 ('Antej'). In many cases, cell size has reduced considerably, but the most obvious decline was for cultivar
'Auksis' (39.33%) and 'Orlik' (22.88%). Analysing the results obtained after apple storage under ultra-low
oxygen conditions should be noted that the cell size reduction for this type of storage was also apparent,
particularly for cultivar 'Orlik' apples – ULO1 (42.15%) and ULO2 (31.27%).In conclusion, should be noted
that specific surface area of membranescan affect the rate of water transpiration from the cells to surrounding
atmosphere.
Table 3:The changes of apple cell size during six months of storage, %
Storage technology Autumn cultivar Winter cultivar
'Auksis' 'Orlik' 'Antej' 'BelorusskojeMalinovoje' 'SinapOrlovskij' 'ZarjaAlatau'
Cold storage -7.75c -30.02b +4.51 +13.61 -15.65a +12.31
Cold storage + 1-
MCP -39.33a -22.88c +26.45 -8.34b +8.11 -2.85b
ULO1 -12.58b -42.15a +21.06 +34.42 -5.64b -3.27b
ULO2 -13.27b -31.27b +6.06 -16.21a +31.42 -18.72a
Note: Value within the same cultivar followed by different small letters are significantly different at p≤0.05 (LSD test).
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Changes in physical parameters of apple fruit:
Water loss is one of the major factors that effects on fruit quality, in particular on firmness [7]. Water loss
due to transpiration process and metabolic activity of endo- and exogenous enzymes limits the marketable life
and affects consumer acceptability of fresh produce [33]. Recently, several studieshave been conducted, whose
purpose was to find the biological causes of softening [7], while no reports were found in literature regards to
the parenchyma cell microstructure and changes of the cell walls during long-term apple storage. Therefore, is
important to figure out, has storage technology any impact on microstructure and quality (weight loss and
firmness) of apple fruitwhile long-terms storage.
Table 4:Fresh weigh loss of apples stored under different conditions, %
Cultivar Storage technology After six months storage
'Auksis'
Cold storage 11.05a
Cold storage + 1-MCP 8.75b
ULO1 7.89c
ULO2 7.06c
'Orlik'
Cold storage 8.50a
Cold storage + 1-MCP 8.02a
ULO1 7.50b
ULO2 6.41c
'Antej'
Cold storage 9.86a
Cold storage + 1-MCP 8.22b
ULO1 8.57b
ULO2 6.76c
'BelorusskojeMalinovoje'
Cold storage 8.96b
Cold storage + 1-MCP 11.43a
ULO1 5.41d
ULO2 8.11c
'SinapOrlovskij'
Cold storage 11.94a
Cold storage + 1-MCP 9.09b
ULO1 7.14c
ULO2 5.19d
'ZarjaAlatau'
Cold storage 11.43a
Cold storage + 1-MCP 10.81b
ULO1 10.14b
ULO2 5.33c
Note: Value within the same cultivar followed by different small letters are significantly different at p≤0.05 (LSD test).
It has been proved that most fruits and vegetables become unmarketable when they lose 5–10% of their
fresh mass [34]. Results showed that after six months apple storage (Table 4), fresh weight loss was higher in
apples those kept under cold storage conditions, corresponding to an average value – 10.29%, followed by
apples treated with 1-MCP,corresponding to an average value – 9.38%. As can be seen, better preservation of
fresh weight loss has been obtained for samples stored in the ULO2 with controlled environment – 6.47%, while
the ULO1 – 7.75%. It is related to the decelerated metabolism in fruits particularly in protective low oxygen
environment of storage chambers. Similar findings have been provided by the scientists [20], who pointed out
on a positive effect of 1-MCP treatment on maintenance of apple quality stored in normal atmosphere for six
months. With regard to some quality parameters and sensory attributes, 1-MCP treated apples stored under
normal atmosphere are comparable to those stored under ULO conditions. Taking into consideration the weight
loss of samples stored under different conditions and structure of apple samples presented before, some line of
interrelation could be found. Apple samples those the composed of larger cells – 'Auksis', 'ZarjaAlatau', and
'SinapOrlovskij' have lost more fresh weight, than those with small cells – 'BelorusskojeMalinovoje' and 'Antej'.
Flesh firmness of the fruits depends on ripening stage, place of growing, weather conditions and cultivar
[20,40]. Flesh firmness decreases during fruit ripening; therefore for all cultivars, the highest firmness has been
observed before storage and storage technology significantly affects the firmness of the apples [20].
Data depicted in the Table 5disclose that at the beginning of long-term storage, flesh firmness fluctuated in
a range from 6.40 kg cm-2 to 8.14kg cm-2. Although, there was a significant difference in firmness loss among
all storage technologies while fruit storage, the changes were considerably slower in ULO1 and ULO2 storage
than in cold storage and cold storage + 1-MCP treatment.
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Table 5: Flesh firmness of apples stored under different conditions, kg cm-2
Cultivar Storage technology Before storage After six months storage
'Auksis'
Cold storage
6.45cA±0.23
2.18bB±0.11
Cold storage + 1-MCP 2.67bC±0.15
ULO1 4.29aD±0.32
ULO2 5.05aE±0.14
'Orlik'
Cold storage
6.40cA±0.23
2.65cB±0.65
Cold storage + 1-MCP 3.01bcC±0.86
ULO1 4.13aD±0.34
ULO2 3.05bcE±0.11
'Antej'
Cold storage
7.14bA±0.46
2.25cB±0.15
Cold storage + 1-MCP 3.49bC±0.19
ULO1 5.25aD±0.32
ULO2 3.96bE±0.19
'BelorusskojeMalinovoje'
Cold storage
6.87bcA±0.46
2.65cB±0.54
Cold storage + 1-MCP 3.17bC±0.34
ULO1 4.94aD±0.76
ULO2 4.21bE±0.53
'SinapOrlovskij'
Cold storage
8.14aA±1.32
3.66bB±0.32
Cold storage + 1-MCP 3.34bC±0.56
ULO1 5.52aD±0.18
ULO2 5.98aE±0.67
'ZarjaAlatau'
Cold storage
7.17bA±0.83
4.29cB±0.56
Cold storage + 1-MCP 3.83cC±0.43
ULO1 4.41bD±0.56
ULO2 5.03aE±0.36
Note: Mean value with standard deviation (±) within the same cultivar followed by different small letters are significantly different at
p≤0.05 (LSD test). Mean value with standard deviation (±) within the same cultivar followed by different capital letters are significantly different by the LSD at
0.05 level (differences between storage conditions).
Results depicted in Table 5 disclose that ULO1 and ULO2maintained fruit firmness better than cold storage
and 1-MCP treatment. The percentage loss after six months of storage for all apple cultivarswas 32.40% in
ULO1 and 35.60% in ULO2, while apples those treated with 1-MCP had lost an average value 53.70% of fresh
weight. As can be seen, a significant decline of fresh weight was mostobvious for cultivar 'Antej' (68.50%),
'Auksis' (66.20%), and 'BelorusskojeMalinovoje' (61.40%) apples stored under cold storage conditions, while
the lowest reduction rate for cultivar 'Auksis' (21.70%) – ULO2, 'Antej' (26.50%) – ULO1, and 'SinapOrlovskij'
apples (26.50%) – ULO2. The results obtained show that controlled atmosphere storage was able to maintain
fruit firmness significantly better than conventional storage or cold storage combination with 1-MCP treatment.
Similar results were provided by [47], who found lower rate firmness rate of firmness loss in apples during long-
term storage under controlled atmosphere. In addition, Thewes and colleagues [44], have reported that flesh
firmness was higher in cultivar of Royal Gala and Galaxy apples stored under ULO conditions that in Dynamic
Controlled Atmosphere storage coupled with chlorophyll fluorescence (DCA-CF). On the other hand,contrary
results were found, where scientists from Poland [23]reported that firmness of the cultivars 'Rajka', 'Rubinola'
and 'Topaz' fruit, did not differ significantly as a result of storage in normal or controlled atmosphere. Our
results with regards to 1-MCP treatment are opposite to those presented earlier [10], where scientists proved that
1-MCP treatment able to delay fruit ripening and softening during storage in terms of the responses of flesh
firmness, ethylene, and CO2 production.
Conclusions:
The present work investigated the influenceof 1-Methylcyclopropene treatment and Ultra-low oxygen
conditions on the changes of structural and physical parameters of apple fruits while long-term storage. The
results of current research disclose that the line of interaction could be found between the structure of apple
samples and weight loss. Whereas, Apple samples those the composed of larger cells – 'Auksis', 'ZarjaAlatau',
and 'SinapOrlovskij' have lost more fresh weight, than those with small cells – 'BelorusskojeMalinovoje' and
'Antej'. Moreover, results showed that after six months apple storage, fresh weight loss was higher in apples
those kept under cold storage conditions, corresponding to an average value – 10.29%, followed by apples
treated with 1-MCP, corresponding to an average value – 9.38%, whilea better preservation of fresh weight loss
has been obtained for samples stored in the ULO2 with controlled environment – 6.47%, while the ULO1 –
7.75%.Results obtained after SEM analysis showed that Ultra-low oxygen storage has resulted in less
pronounced de-compartmentalisation of apple matrix, nevertheless, cellular membrane cracking and collapse as
part of the normal metabolism of the product was evident. Furthermore, ULO storage has affected on better
cohesion and higher compressibility of the cells found in apple. A significant positive effect of 1-MCP on cell
integrity was also evident, whereas cell wall disassembly in many cases was more pronounced when apples
19
were kept for a long-term storage under cold storage.Our results also refute the hypothesis found in the literature
that larger fruit can be comprised of larger cells. Has been found no a positive correlation (r=-0.624) between
the size of cells and fruits. Besides, was noted that large-sized fruits have smallest cells. Our findings disclose
that specific surface area of membranes can affect the rate of water transpiration from the cells to surrounding
atmosphere.
The Potential Contribution Of The Current Study To Knowledge:
According to Latvian Fruit-growers Association’s research conducted in 2011, 89% of citizens would prefer
apples. While choosing cultivar, 49.6% consider the taste, but 39.6% - the appearance of the fruit. While storage
fruit it is essential to maintain their quality, nutritional value and sensory quality throughout the whole storage
time, so appropriate technologies must be chosen that would help to maintain their quality at the maximum.
Most literature data of fruit storage refer only to technology such as ULO, CA, DCA, ILOS; ILOS+. However,
these treatments are being expensive, and not everyone grower can afford such technology for post-harvest
storage of fruits. The use of 1-MCP in agricultural products including apples, kiwi fruits, tomatoes, bananas,
plums, persimmons, avocados and melons (and some ornamental plants) has been approved and accepted for use
in more than 50 countries including the European Union and the United States. In Europe, SmartFresh and
EthylBlock, products based on 1-MCP, have been commercially used since 2006. Since 2008 (in the USA since
2003) thousands of apple growers have used 1-MCP applications in various storage conditions. In order to
maximize the long-term storage of apples, as well as to provide additional information on the suitability of
Latvian’s apple cultivars for 1-MCP treatment, this research is of great interest to the growers. Our previous
studies have confirmed the effectiveness of the 1-MCP on various cultivars of apples. Nonetheless, due to
weather conditions, the same cultivars can be stored in different ways. To be sure that eventually, after long-
term storage the same results will be apparent, more research should be performed and more harvesting seasons
should be taken into consideration.
ACKNOWLEDGMENTS
This research commissioned by Agricultural services co-operative society “AUGĻU NAMS” has been
conducted within framework “The research of fruit storage technologies” funded by State program
“Competence Centre for Food in Latvia”.
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