Effects of Different Oxygen Levels with High-Carbon Dioxide Atmosphere on Postharvest Quality of Fresh Fig under Palliﬂex Storage Systems

: Regulation of storage atmosphere composition with high carbon dioxide (CO 2 ) is a highly effective and alternative approach to control quantity and quality losses in many horticultural crops. The aim of the study was to determine the effects of different O 2 with constant high-level CO 2 on the postharvest quality of ﬁg cv. Bursa Siyahi in a new practical approach. For this purpose, 6% O 2 + 15% CO 2 (PL1), 9% O 2 + 15% CO 2 (PL2) and 21% O 2 + 0.03% CO 2 (Control) compositions were tested under a palliﬂex storage system during the cold storage and shelf-life. PL1 and PL2 were found to be more effective than the control for investigated parameters in general. After 28 days of cold storage and +3 days shelf-life, PL1 was also effective in controlling weight loss, ethylene production, antioxidant activity, decay incidence, decay severity, and total microorganisms. However, there were no signiﬁcant differences between PL1 and PL2 for total soluble solids, titratable acidity, taste, visual appearance, ﬁrmness, respiration rate, and anthocyanin content. PL1 could be an effective composition for controlling decay and maintaining the postharvest quality of fresh ﬁgs during cold storage and shelf-life without any side effects on visual appearance and taste. with


Introduction
Fig (Ficus carica L.) is one of the oldest cultivated and demanded fruits by consumers with high appreciation [1]. Demand for exotic fruit like figs is increasing nowadays due to their rich biochemical properties and positive effects on human health and delicious taste. Fresh figs are rich in phenolic, flavonoid [2], anthocyanin [3] and antioxidant compounds [4]. Fig is one of the most precious fruits with high economic value, and its total production was 1,264,943 tons in 2020, and approximately 75% of the production was met by Turkey (25.3%), Egypt (15.9%), Morocco (11.4%), Iran (8.5%), Algeria (9.2%) and Spain (4.7%), respectively [5]. Moreover, Turkey is the world leader in the exportation of fresh figs, with 20,334 tons in 2019 [6]. The handling, storage, shipping and marketing process of fresh figs requires professional expertise and diligence due to the pomological properties and short postharvest life [7]. Despite the high demand for fresh figs in the market, yearround availability is limited due to its short shelf-life period, and postharvest losses of fresh figs can reach up to 40-50% under inappropriate storage conditions and even higher during shelf-life [8]. Therefore, it is extremely important to develop new postharvest technologies for perishable horticultural crops like fresh fig, especially the commodities having short storage and shelf-life periods. There are several studies conducted to decrease postharvest losses and maintain fruit quality of fresh figs using different postharvest techniques, including low temperature and high CO 2 [9], low O 2 [10], modified atmosphere packaging [11][12][13][14], controlled atmosphere [15,16], 1-MCP [17], UV-C [18], SO 2 [19], calcium chloride [20], chlorine dioxide [21], sodium carbonate, acetic acid [22] and different coating

Materials and Methods
Fresh fig fruits belonging to cv. Bursa Siyahi were harvested from a commercial orchard in Bursa, Turkey. The fruits were immediately transported with a refrigerated truck to the postharvest physiology laboratory of the Department of Horticulture of Akdeniz University in Antalya, Turkey. After eliminating damaged fruits, fruits were harvested commercially at the mature stage and uniformly selected for size and color. Selected fruits were placed into commercial cardboard boxes with 22 inserts, and the boxes containing the fruits were stored in three different ways. The first group was stored in palliflex containing the gas composition 21% O 2 + 0.03% CO 2 as control. The second group was stored in palliflex containing the gas composition 6% O 2 + 15% CO 2 (PL1), and the last group was stored in palliflex containing 9% O 2 + 15% CO 2 (PL2). Fig fruits were stored at 0 ± 0.5 • C at 90 ± 5% RH for 28 days and sampled on 0, 14 and 28 days. Moreover, the fruits were kept for 3 days at 20 • C to evaluate shelf-life performance under ambient atmosphere composition after sampling. For each atmosphere composition, three palliflex storage units were used. In this storage, O 2 and CO 2 levels for each unit were adjusted by a flow-through system, mixing N 2 supplied from a generator, CO 2 , and O 2 supplied from gas bottles. The atmosphere inside each unit was measured at ten-minute intervals until the desired atmosphere compositions were set, and then the compositions were hourly checked and adjusted by the automation during storage.

Weight Losses and Fruit Firmness
Weight loss was determined with a digital scale (Denver TP-214, Denver Instruments, Bohemia, NY, USA) with a sensitivity of 0.01 g at the beginning of the experiment and the end of certain storage periods. Weight loss was calculated as the percentage loss of the initial weight. The firmness of fruits was determined by using a penetrometer (Chatillon DFI 10, Largo, FL, USA) to measure the peeled equatorial region on 3 different sides of fruits. Fruit firmness was shown as an average of these measurements, and results were given in Newton (N).

Total Soluble Solids (TSS) and Titratable Acidity (TA)
Total soluble solid content was measured by a digital refractometer (Atago, Tokyo, Japan) and given as percentage. To determine titratable acidity (TA), the purees were diluted ten times with distilled water and measured through a method described by Bahar and Lichter [16]. TA content was given as the percentage of citric acid.

Visual Appearance and Taste
Visual appearance and taste parameters were evaluated by five trained judges. For each fruit sample, the judges were asked to taste and visualize it and then asked how they felt about the fruit sample on a five-point hedonic scale described by Selcuk and Erkan [29]. In addition, bottled water was given to cleanse their palate in between fruit samples. The hedonic scale was: 1 = very poor; 2 = poor (limit of marketability); 3 = good; 4 = very good; 5 = excellent.
Equation (1) was used to calculate the visual appearance and taste score: Visual appearance or taste score = Total score/Maximum score (1) where the total score is an overall of scores given by five panelist and maximum score is the highest scale point (5).

Respiration Rate and Ethylene Production
The respiration rate and ethylene production were determined by using gas chromatography (GC; Thermo Electron S.p.A., Strada Rivoltana, Milan, Italy). Fruit samples with known weight and volume were initially stored in 3 L gas-tight jars at 20 • C for 1 h. Then, the gas samples of 1 mL were taken out of the jar with a gas-tight syringe to measure respiration rate and ethylene production. Thermal conductivity detector (TCD), Supelco 80/100 alumina F-1 column, flame ionization detector (FID) and GS-GasPro 113-4362 capillary column were used to measure CO 2 and ethylene production, respectively. For respiration measurements, the oven temperature, detector temperature, hydrogen and dry airflow rates were set as 130 • C, 275 • C, 45-and 400 mL min −1 , respectively. Whereas, in the ethylene analysis, oven temperature, detector temperature, and hydrogen, dry air and helium flow rates were set as 35-, 350-and 25 mL min −1 , respectively. The external standards of ethylene and carbon dioxide were used to evaluate the obtained findings.
Equation (2) was used to calculate the respiration rate and ethylene production: where A is the sample area (ppm)/standard area (ppm), Vj is the jar volume (L), Vp is the product volume (L), t is the time (hour) and g is the fruit weight (kg).

Total Antioxidant Activity and Anthocyanin Content
Antioxidant activity (AA) was determined based on the inhibition of 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical, described by Fernández-León et al. [31]. According to their method, 50 µL of the sample extract was diluted with 950 µL of DPPH solution (6 × 10 −5 mol L −1 in methanol). The mixture was kept at room temperature for 30 min and then measured at a wavelength of 515 nm in a spectrophotometer (Specord 40, Analytik-Jena, Jena, Germany). Trolox was used as standard, and AA was calculated as mg of Trolox (6-hydroxy-2,5,7,8-tetramethylchroman-2-carboxylic acid) equivalent 100 g −1 of fresh weight. Total monomeric anthocyanin content was determined using the pHdifferential method described by Lee et al. [32]. According to their method, the pH of the extract was adjusted to pH 1.0 and 4.5 with the potassium chloride (0.025 M, pH 1.0) and sodium acetate buffers. The absorbance of each equilibrated solution was read at 510 and 700 nm in a spectrophotometer (Specord 40, Analytik-Jena, Germany). Distilled water was used as a blank, and total anthocyanins were calculated as µg cyanidin-3-glucoside g −1 of fresh weight.

Decay Incidence, Decay Severity and Total Microorganisms
Decay incidence was recorded by counting the number of fruits with visible symptoms and expressed as a percentage of total fruits. Decay severity was estimated by visualizing the decay area on the surface of the fruit using a scale from 0 (sound fruit) to 5 (81-100% of rotted fruit surface) [33]. The total microorganisms were examined according to the method described by Cantín et al. [19] in both cold storage and shelf-life conditions. To measure the total microorganism, 1 cm 2 pieces were taken from the surface of the fruits and put into microtubes. Then, 1 mL of sterile water was added to the samples in microtubes, and the samples were vortexed for 30 s; 100 µL of the suspension was placed in a Petri dish containing potato dextrose agar (PDA) medium. Microorganisms were counted after incubation for 5 days at 25 • C.

Statistical Analysis
The experiment was conducted by completely randomized design with three replicates, and each replication included 22 fruits. Basic statistical parameters such as mean and standard error of the mean were calculated, and one-way analysis of variance (ANOVA) was performed for each parameter. The data were analyzed by using the SAS 9.0 statistical software (SAS Institute, Cary, NC, USA), and means were compared using Duncan's multiple range test (p ≤ 0.05).

Weight Loss
Different atmosphere compositions significantly affected the weight loss of fig fruits and increased with prolonging storage duration of both cold storage and shelf-life conditions ( Figure 1A,B). The atmosphere compositions, PL1 (1.81%) and PL2 (1.82%), significantly reduced weight loss in comparison to control (2.37%) after 14 days of cold storage ( Figure 1A). Similar results were found in the cold storage period of 28 days, and the highest weight loss reached 3.99% (control). A considerable increase was determined during shelf-life conditions in all atmosphere compositions. After 14 days of cold storage at 0 • C + 3 days of shelf-life at 20 • C, while the highest weight loss was determined as 6.24% in control, and the lowest was 4.63% in PL1 ( Figure 1B). Similarly, after 28 days of cold storage + 3 days shelf-life at 20 • C, whereas the weight loss reached 8.14% in control, it was 6.26% in PL1 ( Figure 1B). Weight loss of horticultural crops during storage affects many biochemical processes and metabolic activity as well as loss of income [34]. In addition, high weight loss in figs can negatively influence the postharvest quality of fruit due to surface wrinkle, desiccation and reduced visual appearance [35]. The current findings illustrated that weight loss of fruits during storage was lower in PL1 and PL2 compared to control. Moreover, the effects of atmospheric composition on weight loss were more evident under shelf-life conditions. However, Tsantili et al. [10] reported that there were no significant differences between control and 2% O 2 (balanced with N 2 ) treated fruit stored at −1 • C.
after incubation for 5 days at 25 °C.

Statistical Analysis
The experiment was conducted by completely randomized design with three replicates, and each replication included 22 fruits. Basic statistical parameters such as mean and standard error of the mean were calculated, and one-way analysis of variance (ANOVA) was performed for each parameter. The data were analyzed by using the SAS 9.0 statistical software (SAS Institute, Cary, NC, USA), and means were compared using Duncan's multiple range test (p ≤ 0.05).

Weight Loss
Different atmosphere compositions significantly affected the weight loss of fig fruits and increased with prolonging storage duration of both cold storage and shelf-life conditions ( Figure 1A,B). The atmosphere compositions, PL1 (1.81%) and PL2 (1.82%), significantly reduced weight loss in comparison to control (2.37%) after 14 days of cold storage ( Figure 1A). Similar results were found in the cold storage period of 28 days, and the highest weight loss reached 3.99% (control). A considerable increase was determined during shelf-life conditions in all atmosphere compositions. After 14 days of cold storage at 0 °C + 3 days of shelf-life at 20 °C, while the highest weight loss was determined as 6.24% in control, and the lowest was 4.63% in PL1 ( Figure 1B). Similarly, after 28 days of cold storage + 3 days shelf-life at 20 °C, whereas the weight loss reached 8.14% in control, it was 6.26% in PL1 ( Figure 1B). Weight loss of horticultural crops during storage affects many biochemical processes and metabolic activity as well as loss of income [34]. In addition, high weight loss in figs can negatively influence the postharvest quality of fruit due to surface wrinkle, desiccation and reduced visual appearance [35]. The current findings illustrated that weight loss of fruits during storage was lower in PL1 and PL2 compared to control. Moreover, the effects of atmospheric composition on weight loss were more evident under shelf-life conditions. However, Tsantili et al. [10] reported that there were no significant differences between control and 2% O2 (balanced with N2) treated fruit stored at −1 °C.  Differences between current findings can be caused by cultivar differences, storage systems and especially the combined effect of low O 2 and high CO 2 . It is known that the low O 2 and high CO 2 levels could affect the respiration rate and metabolism of fruits and vegetables [26,27]. In another similar study, the 'Ottomanit' fig variety fruits were stored in different atmosphere compositions such as 5/5, 5/10 and 5/15 (O 2 /CO 2 %), resulting in lower weight loss compared to the control [16].

Firmness
Fruit firmness was also influenced by cold storage and decreased nearly two-fold during the first 14 days of cold storage in all atmosphere compositions; however, there were no significant differences between PL1 and PL 2 ( Figure 2A). Moreover, the lowest fruit firmness was determined in control (3.   Similar findings were obtained in shelf-life conditions; however, it was determined that PL1 effectively delayed the softening process after 14 + 3 days storage at 20 • C. Fruit firmness in control was diminished by 66.71% and 71.17% after 14 + 3 days and 28 + 3 days of shelf-life compared to harvest. During the ripening-related loss of firmness, it is considered that structural changes in pectin, hemicellulose and cellulose are responsible for altering the structure of the cell wall [36]. It was reported that lowering the O 2 level decreases enzyme activities related to cell modification resulting in delaying the fruit softening [37]. Tsantil et al. [10] also reported that low O 2 level and low temperature slowed firmness loss in fresh fig fruit. Furthermore, Villalobos et al. [13] examined the firmness of 'San Antonio' and 'Banane' figs packaged in microperforated films under low O 2 and high CO 2 and the loss of fruit firmness was prevented due to the reduction in respiration rate and ethylene production. Similar results were obtained in 'Cello Dama Blanco', 'Cuello Dama Negro' and 'San Antonio' fig varieties packaged in different microperforated films [14].

Total Soluble Solids (TSS) and Titratable Acidity (TA)
Although TSS content was slightly increased during cold storage in all atmosphere compositions, control fruit had significantly higher TSS than PL1 and PL2 both after 14and 28-days storage durations (Table 1). However, 14-day cold storage + 3-day shelf-life did not significantly affect the TSS content, while it was higher in control than in PL1 and PL2 after 28-day cold storage + 3-day shelf-life (Table 2). TSS content was closely linked with fresh weight loss and TA content in fresh fig [38]. In this study, control fruit had high-level weight loss in comparison to the PL1 and PL2 due to the slowdown effects of atmosphere composition on metabolism. In parallel to the current findings, Bahar and Lichter [16] determined that a controlled atmosphere delayed ripening and slowed down the increased rate in TSS both in cold storage and shelf-life and in 'Ottomanit' figs. In addition, the atmosphere compositions did not significantly affect the TA content during the cold storage and shelf-life (Tables 1 and 2). Similarly, Ayhan and Karacay [12] also reported no significant differences between passive and active MAP (10% O 2 + 20% CO 2 ) application except for the 20th day of storage for the 'Bursa Siyahi' fig variety in terms of the TA. However, Özkaya et al. [17] reported a slight decrease in TA among control and 1-MCP treated 'Bursa Siyahi' fruits. The different findings obtained from the studies above can be caused by the treatments, harvest maturity stages and storage conditions.

Visual Appearance and Taste
Visual appearance score was not significantly different during the first 14-day storage either in storage time or tested atmosphere compositions (Table 1). However, after the 28-day storage, visual appearance scores decreased in all atmosphere compositions compared to the initial values, and they were lower in control (4.1) in comparison to PL1 (4.6) and PL2 (4.5). Furthermore, shelf-life statistically affected the visual appearance of the fruits (Table 2). Both after 14 + 3 days and 28 + 3 days, the visual appearance scores decreased in all atmosphere compositions compared to the initial value, and the lowest values were recorded in the control (2.7 and 1.7). The fruit taste decreased during storage; however, there were no significant differences among the atmospheric compositions (Table 1). Significant differences occurred in PL1 and PL2 compared to the initial value of taste after 14 days of storage. On the other hand, the fruit taste score significantly decreased after 14 + 3-days and 28 + 3-days of storage in all, compared to the initial value of the fruits ( Table 2). However, the lowest taste score was observed in the control fruit compared to PL1 and PL2 after 14 + 3-days storage, and the atmosphere compositions were not significantly different after 28 + 3-days storage.
Cantín et al. [39] reported that the visual appearance of fig fruit decreased during the storage due to the senescence process and increasing deterioration. On the contrary, the current study findings showed that low O 2 and high CO 2 had positive effects on inhibiting metabolic activity, decay incidence, decay severity and amount of microorganisms during prolonged cold storage and shelf-life conditions. Similar results were reported by Waghmare and Annapure [40], who studied the single and combined effects of irradiation (0.

Ethylene Production and Respiration Rate
At harvest, the ethylene production of the 'Bursa Siyahi' fruit was determined as 3.23 µL C 2 H 4 kg −1 h −1 , and the respiration rate was 21.71 mL CO 2 kg −1 h −1 (Figure 3). Ethylene production significantly increased during both cold storage and shelf-life ( Figure 3A,B). However, high CO 2 and low O 2 levels slowed down ethylene synthesis in fig fruit. On the 14th day of cold storage, the ethylene production in the control fruit was higher in comparison to in fruits stored in PL1 and PL2. A low amount of oxygen solidly decreased the ethylene production in fruits stored in cold storage after 28 days. The highest ethylene production was in control, and the lowest was in PL1 ( Figure 3A). The trend was also similar during shelf-life conditions. While the highest ethylene production reached 8.08 µL C 2 H 4 kg −1 h −1 in control, the lowest was reached 6.16 µL C 2 H 4 kg −1 h −1 in PL1 after 28 + 3-days storage. In general, respiration rate slightly increased during 14-days storage, and it declined during 28-days storage in control. Although the respiration rate was higher at 25.49 mL CO 2 kg −1 h −1 in control in comparison to PL1 and PL2, there was no significant difference between the PL1 and PL2 for the respiration rate during 14-day storage (Figure 3C), and a similar trend was observed at the end of the 14 + 3-day storage ( Figure 3D). On the other hand, respiration rate significantly decreased in control fruit (18.83 mL CO 2 kg −1 h −1 ) compared to PL1 and PL2 (21.16 and 22.73 mL CO 2 kg −1 h −1 ) at the end of the 28-day storage. Furthermore, respiration rate sharply decreased to 21.61 mL CO 2 kg −1 h −1 in control and was significantly lower than PL1 and PL2 after 28 + 3-days storage; however, PL1 and PL2 were not statistically different ( Figure 3D). Crisosto et al. [42] reported that the ethylene production of fresh fig fruit generally increased from 4.0 to 6.0 µL C 2 H 4 kg −1 h −1 when respiration rate increased from 20 to 30 mL CO 2 kg −1 h −1 at 20 • C. Similar results were found in the current study, where ethylene production changed between 3.23 and 8.08 µL C 2 H 4 kg −1 h −1 while respiration rate changed from 18.83 to 27.60 mL CO 2 kg −1 h −1 based on treatments and storage times. were found in the current study, where ethylene production changed between 3.23 and 8.08 μL C2H4 kg −1 h −1 while respiration rate changed from 18.83 to 27.60 mL CO2 kg −1 h −1 based on treatments and storage times.

Figure 3.
Ethylene production and respiration rate changes during cold storage (A,C), and ethylene production and respiration rate changes during shelf life (B,D). Data are the mean ± SE of three replicates of twenty-two fruit. Different uppercase letters indicate significant differences for each atmosphere composition during storage, and different lowercase letters indicate significant differences among atmosphere compositions for each sampling date at p < 0.05. Non-significant differences (p ≥ 0.05) in atmosphere composition and storage time did not give any letters.
In this study, PL1 and PL2 were more successful in inhibiting ethylene production in comparison to control. Similarly, the enriched storage atmosphere of 15% and 20% CO2 inhibited ethylene production in the 'Mission' fig due to the effects of autocatalytic ethylene biosynthesis [9]. In addition, many studies illustrated that low O2 and high CO2 reduced ethylene production and respiration rate [27,43] since they slow down fruit maturation by decreasing the expression of genes associated with ethylene synthesis [44]. On the other hand, although the respiration rate increased in the first period and then decreased, ethylene production in all atmosphere compositions showed an increasing trend during the storage periods. The increasing trend, especially in the first period, for both traits can be because fruits of cv. Bursa Siyahi show a certain amount of color change and maturation after harvesting. It was also stated by Freiman et al. [45] that there may be an increase in ethylene production in fig fruit with the progress of ripening. Similarly, Özkaya et al. [17] reported that an increase in ethylene production and respiration rate Figure 3. Ethylene production and respiration rate changes during cold storage (A,C), and ethylene production and respiration rate changes during shelf life (B,D). Data are the mean ± SE of three replicates of twenty-two fruit. Different uppercase letters indicate significant differences for each atmosphere composition during storage, and different lowercase letters indicate significant differences among atmosphere compositions for each sampling date at p < 0.05. Non-significant differences (p ≥ 0.05) in atmosphere composition and storage time did not give any letters.
In this study, PL1 and PL2 were more successful in inhibiting ethylene production in comparison to control. Similarly, the enriched storage atmosphere of 15% and 20% CO 2 inhibited ethylene production in the 'Mission' fig due to the effects of autocatalytic ethylene biosynthesis [9]. In addition, many studies illustrated that low O 2 and high CO 2 reduced ethylene production and respiration rate [27,43] since they slow down fruit maturation by decreasing the expression of genes associated with ethylene synthesis [44]. On the other hand, although the respiration rate increased in the first period and then decreased, ethylene production in all atmosphere compositions showed an increasing trend during the storage periods. The increasing trend, especially in the first period, for both traits can be because fruits of cv. Bursa Siyahi show a certain amount of color change and maturation after harvesting. It was also stated by Freiman et al. [45] that there may be an increase in ethylene production in fig fruit with the progress of ripening. Similarly, Özkaya et al. [17] reported that an increase in ethylene production and respiration rate was determined in fruits of cv. Bursa Siyahi stored for 10 days. Moreover, it is considered that the decrease in respiration rate at the end of the storage can be caused by fruit senescence. Byeon and Lee [38] also highlighted that the respiration of fig fruits increased during the first ten-day cold storage and then decreased sharply during the second half of cold storage.

Total Antioxidant Activity
It is acknowledged that fig fruit has rich antioxidant activity [4,46]. In the current study, the total antioxidant activity gradually decreased in all atmosphere compositions compared to the initial value during storage ( Figure 4A). However, low O 2 and high CO 2 slowed the loss of antioxidant activities of fruits compared to control. During the 14-day storage, control fruit had significantly lower antioxidant activity than PL1 and PL2. At the end of the 28-days storage, while the highest antioxidant activity was detected in PL1 (428.2 mg Trolox 100 g −1 fw), the lowest was in the control fruit (396.5 mg Trolox 100 g −1 fw) ( Figure 4A). Similar results were also obtained in shelf-life conditions ( Figure 4B). Singh and Singh [47] stated that the antioxidative systems efficiently managed under low O 2 atmospheres to scavenge reactive oxygen species produced in response to gas stresses. In the current study, low O 2 combined with high CO 2 levels delayed the decrease in antioxidant activity of fresh figs. PL1 delayed loss of antioxidant activity, and therefore low O 2 can be prominent to reduce antioxidant loss in fresh figs at the end of the storage. The decrease in antioxidant activity can be caused by a decrease in polyphenol, vitamin C and other antioxidant-derivative biochemicals, as stated by Adiletta et al. [24]. On the other hand, Solomon et al. [1] also reported that total polyphenol and anthocyanin contents were positively correlated with antioxidant activity in ripe fig fruits as in this study. Therefore, decreased anthocyanin content in long-term storage may cause a decrease in antioxidant activity. was determined in fruits of cv. Bursa Siyahi stored for 10 days. Moreover, it is considered that the decrease in respiration rate at the end of the storage can be caused by fruit senescence. Byeon and Lee [38] also highlighted that the respiration of fig fruits increased during the first ten-day cold storage and then decreased sharply during the second half of cold storage.

Total Antioxidant Activity
It is acknowledged that fig fruit has rich antioxidant activity [4,46]. In the current study, the total antioxidant activity gradually decreased in all atmosphere compositions compared to the initial value during storage ( Figure 4A). However, low O2 and high CO2 slowed the loss of antioxidant activities of fruits compared to control. During the 14-day storage, control fruit had significantly lower antioxidant activity than PL1 and PL2. At the end of the 28-days storage, while the highest antioxidant activity was detected in PL1 (428.2 mg Trolox 100 g −1 fw), the lowest was in the control fruit (396.5 mg Trolox 100 g −1 fw) ( Figure 4A). Similar results were also obtained in shelf-life conditions ( Figure 4B). Singh and Singh [47] stated that the antioxidative systems efficiently managed under low O2 atmospheres to scavenge reactive oxygen species produced in response to gas stresses. In the current study, low O2 combined with high CO2 levels delayed the decrease in antioxidant activity of fresh figs. PL1 delayed loss of antioxidant activity, and therefore low O2 can be prominent to reduce antioxidant loss in fresh figs at the end of the storage. The decrease in antioxidant activity can be caused by a decrease in polyphenol, vitamin C and other antioxidant-derivative biochemicals, as stated by Adiletta et al. [24]. On the other hand, Solomon et al. [1] also reported that total polyphenol and anthocyanin contents were positively correlated with antioxidant activity in ripe fig fruits as in this study. Therefore, decreased anthocyanin content in long-term storage may cause a decrease in antioxidant activity.

Total Anthocyanin Content (TAC)
At harvest, TAC was 122.7 μg cy-3-rutinoside g −1 . TAC significantly increased during the 14-day storage period in all atmosphere compositions, and then it decreased in PL2 and control at the end of the 28-day storage ( Figure 5A). The highest TAC was detected in control fruit (139.1 μg cy-3-rutinoside g −1 ) during the first 14-day storage, and the lowest

Total Anthocyanin Content (TAC)
At harvest, TAC was 122.7 µg cy-3-rutinoside g −1 . TAC significantly increased during the 14-day storage period in all atmosphere compositions, and then it decreased in PL2 and control at the end of the 28-day storage ( Figure 5A). The highest TAC was detected in control fruit (139.1 µg cy-3-rutinoside g −1 ) during the first 14-day storage, and the lowest TAC was in control (115.4 µg cy-3-rutinoside g-1) during the last 28-day storage. The storage of figs for 14 + 3-days significantly affected the TAC, where it was 143.3 µg cy-3-rutinoside g −1 in control and higher than PL1 and PL2 ( Figure 5B). On the other hand, TAC was significantly higher in PL1 and PL2 than in control at the end of 28 + 3-days storage.
increased during the first five days and then decreased at the end of storage, as found in this study. Romero et al. [48] reported that high CO2 levels as a pretreatment increased the anthocyanin content of the grapes, but this increase was lower in comparison to nontreated as found in the current study. Ali et al. [49] also claimed a decrease in the anthocyanin content of litchi fruit stored in a controlled atmosphere due to the slowing effects of the latter on metabolism and senescence. It can be because of the relatively high O2 level since it is known as a destabilizing factor for polyphenolic compounds like total anthocyanins [50]. Khorshidi et al. [51] also support this hypothesis by acknowledging that a lower content of polyphenol and anthocyanin cherries stored in a normal atmosphere compared to fruits stored in a modified atmosphere was observed.

Decay Incidence, Decay Severity and Total Microorganisms
Appropriate storage conditions should be provided to avoid decay losses in fresh fig; if not, severe decay loss may appear within a short time. There was no decay during the first 14-day cold storage in low O2 stored fruit, while a 5.6% decay incidence was found in control (Table 3). Whereas the highest decay incidence was determined in control (42.6%), the lowest was in PL1 (25.9%) during the 28-days of cold storage. However, decay incidences of fig fruit sharply increased during shelf-life conditions (Table 4). After 14 + 3days storage, while the highest decay incidence (51.9%) was determined in control fruits, the lowest (28.0%) was determined in PL1. A similar trend was observed at the end of 28 + 3-days storage. When the decay incidence of control fruits increased up to 87.0%, it was 40.7% in PL1 (Table 4). Therefore, low O2 and high CO2 storage can be used effectively to control the decay incidence of fresh fig. The highest decay severities of 3.2 and 37.0 were detected in control for 14 and 28-days storage, respectively. Decay severity decreased based on the lowering oxygen level, and at the end of the storage, the lowest decay severity was 13.4 observed in PL1 (Table 3). During 14 + 3-days and 28 + 3-days shelf-life, while the highest decay severity was 44.0 and 69.5 in control, respectively, the lowest (14.4 and TAC showed an increase in the first 14-day cold storage period and then showed a decrease; however, these changes between periods were limited to PL1 and PL2. Saki et al. [25] reported that the anthocyanin content of coated and uncoated cv. 'Siah' fig fruit increased during the first five days and then decreased at the end of storage, as found in this study. Romero et al. [48] reported that high CO 2 levels as a pretreatment increased the anthocyanin content of the grapes, but this increase was lower in comparison to non-treated as found in the current study. Ali et al. [49] also claimed a decrease in the anthocyanin content of litchi fruit stored in a controlled atmosphere due to the slowing effects of the latter on metabolism and senescence. It can be because of the relatively high O 2 level since it is known as a destabilizing factor for polyphenolic compounds like total anthocyanins [50]. Khorshidi et al. [51] also support this hypothesis by acknowledging that a lower content of polyphenol and anthocyanin cherries stored in a normal atmosphere compared to fruits stored in a modified atmosphere was observed.

Decay Incidence, Decay Severity and Total Microorganisms
Appropriate storage conditions should be provided to avoid decay losses in fresh fig; if not, severe decay loss may appear within a short time. There was no decay during the first 14-day cold storage in low O 2 stored fruit, while a 5.6% decay incidence was found in control (Table 3). Whereas the highest decay incidence was determined in control (42.6%), the lowest was in PL1 (25.9%) during the 28-days of cold storage. However, decay incidences of fig fruit sharply increased during shelf-life conditions (Table 4). After 14 + 3-days storage, while the highest decay incidence (51.9%) was determined in control fruits, the lowest (28.0%) was determined in PL1. A similar trend was observed at the end of 28 + 3-days storage. When the decay incidence of control fruits increased up to 87.0%, it was 40.7% in PL1 (Table 4). Therefore, low O 2 and high CO 2 storage can be used effectively to control the decay incidence of fresh fig. The highest decay severities of 3.2 and 37.0 were detected in control for 14 and 28-days storage, respectively. Decay severity decreased based on the lowering oxygen level, and at the end of the storage, the lowest decay severity was 13.4 observed in PL1 (Table 3). During 14 + 3-days and 28 + 3-days shelf-life, while the highest decay severity was 44.0 and 69.5 in control, respectively, the lowest (14.4 and 28.2) was obtained from PL1 (Table 4). Moreover, a combination of low O 2 and high CO 2 significantly inhibited the total microorganism populations of fig fruits in parallel to decay data. PL1 and PL2 had significantly fewer microorganisms than control during the first 14-day storage (Table 3). At the end of the 28-day storage, while the highest microorganism population was detected in control (4.37 × 10 5 cfu), the lowest was in PL1 (2.37 × 10 5 cfu). Similar results were also found in shelf-life (Table 4). The higher microorganism population was determined in control (5.90 × 10 5 cfu) followed by PL2 (4.10 × 10 5 cfu) and PL1 (3.20 × 10 5 cfu) after 28 + 3-days storage. The quality of fresh fig can be negatively affected by many pathogens such as Alternaria spp., Botrytis spp., Fusarium spp., Aspergillus spp., Penicillium spp. and Rhizopus spp. [8,19,52]. In the current study, most fresh figs decay occurred as mottling from the ostiole part of the fruit or start from the contact points with viols in packages. It was observed that low O 2 and high CO 2 had positive effects on lowering decay incidence and severity since they inhibit pathogen reproduction. Colelli et al. [9] reported that for controlling decay, 15% and 20% CO 2 levels were more effective than the normal atmosphere for cv. Mission fig. The 15% CO 2 or higher level was effective against Botrytis rot in Red Globe and Thompson Seedless grape [53]. Besides, 10% CO 2 + 6% O 2 level was suggested for Red Globe grapes for 4 weeks [54]. MAP, including low O 2 and high CO 2 storage, was effective in reducing decay development on 'San Antonio' and 'Banane' fig, while decay reached 98% in control fruit at the end of 21-day storage [13]. Likewise, positive effects of atmosphere compositions were also observed in 'Cuello Dama Blanco' and 'Cuello Dama Negro' fig cultivars reported by Villalobos et al. [14]. The total microorganisms in the current study varied from 1.67 × 10 5 to 5.90 × 10 5 cfu, and these findings agreed with the findings of Tepeli et al. [55], who determined the total microorganisms to be between 1.00 × 10 5 and 9.50 × 10 5 cfu in 'Bursa Siyahi' fig stored with antimicrobial MAP. The ripening and senescence are delayed in a controlled atmosphere, and so decay incidence and susceptibility could be reduced [56]. These findings suggest that PL1 was more effective in controlling total microorganism burden both in cold storage and shelf-life.

Conclusions
A typical controlled atmosphere storage is not appropriate for fresh figs since commercial companies face many challenges regarding fruit circulation and management in a short season. Therefore, palliflex storage systems might be a useful alternative to overcome these problems. The current study revealed that the atmosphere composition of 6% O 2 + 15% CO 2 (PL1) was more effective in reducing ethylene production, respiration rate, antioxidant activity, decay incidence, decay severity and total microorganisms without any side effects on visual appearance and taste.