Optimal storage temperature and 1-MCP treatment combinations for different marketing times of Korla Xiang pears

JIA Xiao-hui, WANG Wen-hui, DU Yan-min, TONG Wei, WANG Zhi-hua, Hera Gul

Research Institute of Pomology, Chinese Academy of Agricultural Sciences, Xingcheng 125100, P.R.China

1.Introduction

Korla Xiang pear (Pyrus sinkiangensis Yü Korla Xiang),which originated from Xinjiang Uygur Autonomous Region in China, is usually harvested in mid-September.It has many valuable characteristics, such as a thin exocarp, crispy flesh,high juice and sugar content, little endocarp, and rich flavor(Gao et al.2005).It has a high profit value, high sales, and the longest marketing duration and is the main pear cultivar exported from China (Jia et al.2009).According to our continuous tracking study, maintenance of green color is the primary indicator of quality in the market evaluation of Korla Xiang pears at present (Jia et al.2014).Maintenance of green color is generally achieved by early harvesting and decreasing storage temperature, but early harvesting results in poor fruit quality and storage at a low temperature near freezing eventually results in chilling injury.

The ethylene inhibitor, 1-methylcyclopropene (1-MCP),is broadly used in the preservation of fruit and vegetables for several reasons.First, 1-MCP inhibits the decline in fruit firmness, thus extending the storage life (Sun et al.2003;Li et al.2004; Sisler and Serek 2010; Wang et al.2015).Second, 1-MCP inhibits the occurrence of disorders such as superficial scald (Gago et al.2013, 2015; Gao et al.2015;DeEll et al.2016; Zhou et al.2017) and core browning(Villalobos-Acuna et al.2011a, b; Wang et al.2011).Third,1-MCP induces disease resistance against fungal pathogens(Jiang et al.2001; Zhang et al.2012).Finally, it can slow down the degradation of chlorophyll, thus keeping the fruit surface bright (Golding et al.1999; Cheng et al.2012;Fernández-León et al.2013).However, 1-MCP treatment also inhibits the production of aromatic volatile compounds,particularly esters, which is an important index used to evaluate the quality of climacteric fruits (Argenta et al.2003;Rizzolo et al.2005; Zhou et al.2015; Li et al.2016).The effects of 1-MCP in combination with other treatments such as a modified or controlled atmosphere (Anna et al.2014),maturity (Jia et al.2014), and Ca2+(Gago et al.2016), etc.,have also been studied.The control of fruit and vegetable ripening by 1-MCP is affected by plant-related factors, such as species, cultivar and maturity of fruit at harvest, and external factors, such as treatment temperature and duration and delays between harvest and time of treatment (DeEll et al.2002; Watkins 2006, 2008; Jia et al.2014).

Temperature is an important environmental factor that affects the quality of fruits during storage.Low-temperature conditions can result in the increased production of esters and fruity flavor attributes (Makkumrai et al.2014) and inhibition of microbial growth (Yamane 1982), contrarily on the other hand it can cause many problems, mainly including superficial scald (Hu et al.2004; Rizzolo et al.2014), flesh browning (Kou 2001; Cantin et al.2010), core browning (Wang et al.2014; Zhou et al.2014) and abnormal softening (Wang et al.2005).The effects of 1-MCP depend on temperature; the susceptibility to some disorders that are thought to be related to chilling injury appears to be increased by 1-MCP treatment during low temperature storage (Watkins et al.1995; Watkins 2006).Treatment with 1-MCP strongly inhibits softening, yellowing, soft scald and internal breakdown in Abate Fetel pears stored at -0.5°C, regardless storage atmosphere and time.But 1-MCP-treated pears stored at 1°C developed soft scald in a control atmosphere, although the severity was slight and the fruits were still marketable (Vanoli et al.2016).

In this study, we analyzed the effects of 1-MCP combined with low temperature on the quality of Korla Xiang pears during storage.The research objectives included determining the optimal combination of storage temperature and 1-MCP treatment for different marketing times, and to solve issues related to the storage of Korla Xiang pears, such as poor fruit quality and chilling injury due to early harvesting and decreasing storage temperature,respectively.

2.Materials and methods

2.1.Fruit materials and treatments

Pear (Pyrus sinkiangensis Yü Korla Xiang) fruits were harvested at commercial maturity from an orchard in Korla County, Xinjiang Uygur Autonomous Region, China on 15th September 2015.After being harvested, these fruits were immediately transported to the Research Institute of Pomology, Chinese Academy of Agricultural Sciences, in Liaoning Province.It took 3 days to transport the pears by air and land transportations.Fruits were of uniform size and without physical injuries or infections.The average fruit firmness from 20 randomly selected fruits was 52.23 N as determined by a fruit texture analyzer (GS-15, GÜSS,South Africa), and the total soluble solids (TSS) content was 13.07% as determined by a digital refractometer (PR-101α,ATAGO, Japan).

The fruits were enclosed in a plastic container (500 L) and treated with 0.03125 g 1-MCP (Youer, Hangzhou, China),which was obtained by dissolving a commercial powder in sterile distilled water to a concentration of 1.0 μL L-1.An equal volume sterile water was used as a control.The fruit were treated for 20 h at 15°C and then randomly divided into three groups.The fruits (20 kg) were packed in a single unsealed plastic bag to maintain a high relative humidity(90-95%), and then put into plastic trays and stored at -1.5,0 and 2°C, respectively.The fluctuations in temperature of the surrounding environment remained in the range from-0.3 to 0.3°C.

After storage for 90, 150 and 225 days, respectively, 15 pears per treatment (1-MCP/storage temperature) were analyzed for skin color, chlorophyll fluorescence parameters,firmness, TSS, titratable acidity, ascorbic acid content,cellular membrane permeability and malondialdehyde content.Ethylene production and respiration rate were measured for 18 fruits (6 fruits per plastic box, 3 boxes per treatment) at the 1st, 3rd, 5th and 7th day of storage at 20°C.Stalk preservation index, core browning index, decay rate and weight loss rate were determined after 90, 150 and 225 days of storage, and each box was considered a replicate.

2.2.Determination of skin color

Fruit surface hue angle (H) and lightness (L) values were determined according to the method of Li et al.(2012) with some modifications.For 15 individual fruits, the surface H and L values for 2 sites on the equatorial perimeter located on opposite sides were determined using a Minolta colorimeter (Model CR-400, Minolta Camera Co., Japan).

2.3.Stalk preservation index, core browning index,decay rate and weight loss rate

For determination of the stalk preservation index, the stalk preservation level was divided into 6 levels; level 1(completely dry and brown), level 2 (more than 2/3 dry and brown), level 3 (1/2 to 2/3 dry and brown), level 4 (1/3 to 1/2 dry and brown), level 5 (less than 1/3 dry and brown)and level 6 (not dry and brown).The core browning index,or the amount of core brown area was divided into 6 levels:level 1 (no brown), level 2 (less than 1/3 brown), level 3 (1/3 to 1/2 brown), level 4 (1/2 to 2/3 brown), level 5 (more than 2/3 brown) and level 6 (completely brown).The formulae used to calculate the stalk preservation index and core browning index were:

Stalk preservation index=

Where, the number “5” means the representative value of the highest level.Decay rate was calculated as the percentage of decayed fruits among all investigated fruits.

The fruit weight loss during 90, 150 and 225 days of storage was calculated by subtracting the final weight from the initial (fresh) weight.

2.4.Determination of firmness, TSS, titratable acidity and ascorbic acid content

Fruit firmness was determined on opposite sides of the equatorial perimeter of each fruit after skin removal using an electronic texture analyzer fitted with an 11.3-mm round head probe (GS-15, GÜSS, South Africa).Penetration speed was 10 mm s-1.Pulp was cut from the equator and juice samples were obtained by squeezing the pulp.TSS content was measured in these fruit juice samples using a digital refractometer (PR-101α, ATAGO, Japan).Titratable acidity (expressed as mg equivalents of malic acid per g of juice) was determined by titrating a 3-g juice sample with 0.1 N NaOH to an end point using an intelligent potentiometric titration instrument (808, Metrohm, Switzerland).The fruit juice used to measure the TSS and titratable acidity came from the opposite sides of equatorial perimeter.Ascorbic acid content was determined as described by Cao et al.(2007) and expressed as mg 100 g-1.Measurements were done on the same fruit for a total of 15 fruits.First flesh firmness was determined, followed by TSS, titratable acidity and ascorbic acid content.

2.5.Measurement of cellular membrane permeability and malondialdehyde (MDA) content

Cell membrane permeability was measured using a DDS-320 conductivity meter.For this purpose, 30 peels, each 10 mm in diameter and 0.5 mm thick, were cut from the equatorial perimeter of every fruit.These peels were placed into three 100-mL glass beakers filled with 50 mL water.Three samples were directly measured using a conductivity meter (C0), and then placed in a shaker set at a speed of 60 r min-1under a constant temperature for 30 min.The cellular permeability of these samples (C1) was then measured.Finally, after the samples were incubated for 30 min in a boiling water bath, then, after cooling, the volume was raised to 50 mL, and the cellular membrane permeability of these samples (C2) was measured.The following formula was used to calculate the relative electric conductivity:Relative electric conductivity (%)=.To determine the cellular membrane permeability of the flesh, flesh samples 10 mm in diameter with a thickness of 2 mm were cut with two knives from 1 mm above the equator.The determination of relative electric conductivity was identical to that described for the peel.MDA content was expressed in nmol g-1and was determined as described by Cao et al.(2007), peel and flesh samples were also collected for determinations of MDA content.

2.6.Ethylene production and respiration rate

Respiration rate (expressed as CO2evolution) and ethylene production were measured daily for 18 pears per treatment after 24 h at 20°C upon removal from cold storage.A set of 6 pears was sealed for 60 min in a 2.35-L airtight plastic box, and then a 1-mL gas sample was withdrawn through a rubber septum using a plastic syringe for analysis in a gas chromatograph (LUNAN GC-9890, Shandong, China).Nitrogen was used as the carrier gas at flow rates of 55-58 mL min-1.The temperatures of the detector, the packed column and the reformer were, respectively, 140,120, and 350°C.The headspace ethylene gas samples were withdrawn through a septum on the top of the plastic box using a 1-mL gas-tight syringe.Ethylene production rate was expressed as μL kg-1h-1, and fruit respiration rate(CO2evolution rate) was expressed as mg CO2kg-1h-1.

2.7.Statistical analysis

The data were subjected to analysis of variance (ANOVA)using SPSS Statistics 16.0 (SPSS Inc., Chicago, Illinois,USA).Data were presented as means±standard deviations.Comparison of means was performed using Duncan’s multiple range test.A value of P＜0.05 was considered statistically significant.

3.Results

3.1.H value, L value and chlorophyll fluorescence parameters

H value indicates the skin color, and the lower the H value is, the yellower the skin is.The decrease in H value during storage indicated that the skin color of Korla Xiang pears changed from green to yellow (Fig.1-A).For all cold storage times, the H value of the fruits stored at 2°C was significantly lower than fruits stored at -1.5 and 0°C.1-MCP treatment significantly inhibited the decrease in H value of pears stored for 90 days at the same temperature.But 1-MCP had no significant effect on the H value of fruits stored for 150 and 225 days at the same temperature (Fig.2-A and B).

Greasiness of the skin is the result of the change in fruit wax components and is a visual phenotype of fruit senescence.L value indicates the degree of greasiness of the skin, and the higher the L value is, the greasier the skin is.The change in L values during storage indicated that the degree of greasiness of Korla Xiang pears changed from low to high (Fig.1-B).With increasing storage time and storage temperature, the L value increased while the H value gradually decreased.After 90 days of storage,small decreases in H value were observed with increasing temperature.1-MCP treatment did not have a significant effect on the L value of fruits stored at 150 and 225 days at the same temperature.

The L value was lower for fruits stored at -1.5°C compared with 0 and 2°C.Compared with the control,1-MCP treatment effectively inhibited the increase in L value and decrease in H value.

Chlorophyll fluorescence reflects the ability of the peel to photosynthesize.Fmand Fv/Fmdecreased gradually with increasing time in cold storage and with increasing storage temperature (Fig.3-A and B).For each storage time, the Fmand Fv/Fmvalues were the highest for 1-MCP-treated fruits stored at -1.5°C and the lowest for the control fruits stored at 2°C.Compared with the control fruits, Fmand Fv/Fmin 1-MCP-treated fruits increased with increasing storage temperature.

3.2.Stalk preservation index, core browning index,decay rate and weight loss rate

Fig.1 Hue angle value (H, A) and lightness value (L, B) of the Korla Xiang pears were measured after 7 days at 20°C after 90,150 and 225 days of storage at -1.5, 0 and 2°C.Values are means±SD (n=3).The different letters above the error bars represent signifcant differences at P＜0.05 according to Duncan’s multiple range test at the same storage time.

Fig.2 The appearance of Korla Xiang pears subjected to different storage temperatures with or without 1-methylcyclopropene(1-MCP) treatment.Images were taken after 7 days at 20°C after cold storage for 150 days (A) and 225 days (B).Control (left)and 1-MCP-treated (right) pears stored at different temperatures are shown.

Fig.3 Fm (A) and Fv/Fm (B) of the Korla Xiang pears measured after 7 days at 20°C after 90, 150 and 225 days of storage at -1.5,0 and 2°C.Values are means±SD (n=3).The different letters above the error bars represent signifcant differences at P＜0.05 according to Duncan’s multiple range test at the same storage time.

With increasing time in cold storage, the stalk preservation index decreased, while the core browning index, decay rate and weight loss rate gradually increased (Fig.4).The stalk preservation index was higher under low temperature(Fig.4-A), while the decay rate (Fig.4-C) and weight loss rate (Fig.4-D) were lower.Under a storage temperature of 2°C, regardless of 1-MCP treatment, the stalk preservation index was significantly lower than that of fruits stored at -1.5 and 0°C (Fig.4-A).For control fruits stored for 90 and 150 days, the highest core browning index was observed at a storage temperature of -1.5°C.In control fruits stored for 225 days, the highest fruit core browning index was observed at 2°C, and the browning index was relatively stable during the entire storage period at -1.5°C(Fig.4-B).In general, 1-MCP inhibited the increase in core browning index, decay rate (Fig.4-C) and weight loss rate (Fig.4-D).

3.3.Firmness, total soluble solids, titratable acidity and ascorbic acid content

Fruit firmness declined with decreasing temperature(Table 1), and 1-MCP treatment inhibited this decline, with the highest firmness observed for 1-MCP-treated fruits stored at 0°C (Table 1).The effects of 1-MCP and different low-temperature treatments on fruit TSS content were not significant (Table 2).There was no significant decrease in firmness and TSS during storage.In fruits stored for 150 days,the titratable acid content was the highest for 1-MCP-treated fruits stored at 0°C.After 225 days of cold storage,1-MCP-treated fruits stored at 2°C had the highest titratable acid content, whereas control fruits stored at -1.5°C had the lowest (Table 3).The ascorbic acid content was the highest in 1-MCP-treated fruits stored at -1.5°C (Table 4).In general, 1-MCP treatment significantly inhibited the decline intitratable acid and ascorbic acid content.

3.4.Cellular membrane permeability and MDA content

Fig.4 Stalk preservation index (A), core browning index (B), decay rate (C) and weight loss ratio (D) of Korla Xiang pears were measured after 7 days at 20°C after 90, 150 and 225 days of storage at -1.5, 0 and 2°C.Values are means±SD (n=3).The different letters above the error bars represent signifcant differences at P＜0.05 according to Duncan’s multiple range test at the same storage time.

Table 1 Firmness of pears kept for 7 days at 20°C after 90,150 and 225 days of cold storage (N)

At all storage times, 1-MCP inhibited the increase in relative electrical conductivity of the peel and core.After storage for 90 days, the relative electrical conductivity of the core of control fruits stored at -1.5°C was the highest (Fig.5-B).After storage for 150 days, regardless of 1-MCP treatment,the relative electrical conductivity of the peel and core of fruits stored at 2°C were significantly higher than two other storage temperatures (Fig.5).

With increasing storage time, the content of MDA increased in both the peel and the core, and 1-MCP treatment significantly inhibited this increase (Fig.6).The highest MDA content for both control and 1-MCP-treated fruits was observed for fruits stored for 225 days at -1.5°C.At all storage times, the MDA content of the core of control fruits was significantly higher than 1-MCP-treated pears stored at the same temperature (Fig.6-B).After storage for 225 days, the MDA content of the cores of 1-MCP-treated fruits was the lowest for fruits stored at 0°C (Fig.6-B).

Table 2 Total soluble solids content of pears kept for 7 days at 20°C after 90,150 and 225 days of cold storage (%)

Table 3 Titratable acidity of pears kept at 7 days at 20°C after 90,150 and 225 days of cold storage (mg g-1)

Table 4 Ascorbic acid content of pears kept for 7 days at 20°C after 90, 150 and 225 days of cold storage (mg 100 g-1)

Fig.5 Relative electrical conductivity of the peel (A) and core (B) of Korla Xiang pears were measured after 7 days at 20°C after 90, 150 and 225 days of storage at -1.5, 0 and 2°C.Values are means±SD (n=3).The different letters above the error bars represent signifcant differences at P＜0.05 according to Duncan’s multiple range test at the same storage time.

3.5.Respiration rate and ethylene production

During the first 150 days of storage, 1-MCP significantly inhibited ethylene production and respiration rate at 20°C(Fig.7-A, B, D and E).After 225 days at -1.5 and 0°C,1-MCP still effectively inhibited ethylene production, but at 2°C, it had no inhibitory effect on ethylene production and respiration rate (Fig.7-C and F).Ethylene production by pears treated with 1-MCP at -1.5°C was the lowest for all storage times, followed by 1-MCP-treated pears stored at 0°C.Whereas pear ethylene production at 2°C was the highest after the first day at 20°C, the respiration rate of the pears at -1.5°C was the highest for all storage times.In general, low temperature and 1-MCP treatment inhibited the release of ethylene, but at -1.5°C increased the respiration rate.

Fig.6 Malondialdehyde (MDA) of the peel (A) and core (B) of the Korla Xiang pears were measured after 7 days at 20°C after 90,150 and 225 days of storage at -1.5, 0 and 2°C.FW, fresh weight.Values are means±SD (n=3).The different letters above the error bars represent signifcant differences at P＜0.05 according to Duncan’s multiple range test at the same storage time.

4.Discussion

Chlorophyll degradation is the most visual representation of plant senescence and fruit ripening (Ougham et al.2008).Chlorophyll degradation is usually accompanied by the loss of photosynthetic efficiency and senescence(Thomas and Howarth 2000).Here we used chlorophyll fluorescence, which reflects the ability of the peel to photosynthesize, as a measure of chlorophyll degradation.We found that, compared with the control group, 1-MCP inhibited the decrease of the photosynthetic parameters,Fvand Fv/Fm.Treatment with1-MCP significantly reduced fruit ethylene production, and peels retained a higher chlorophyll content for a longer period of time.These results may indicate that an increase in endogenous ethylene acts as a signal to stimulate chlorophyll catabolism in the fruit peel.

Temperature has a significant effect on chlorophyll degradation in postharvest fruits and vegetables.We found that, compared with -1.5 and 0°C, storage at 2°C accelerated the process of fruit color changing from green to yellow.This may be due to the effect of temperature on various enzymes involved in chlorophyll degradation in fruits and vegetables, such as chlorophyll peroxidase (Yang et al.2005).Moreover, relatively low temperatures have an inhibitory effect on enzyme activity.We also found that under different temperatures, ethylene production was quite different.For example, when fruits were removed from storage at low temperature, higher ethylene production was observed in the fruits stored at 2°C than those stored at -1.5°C.Studies have shown that the degradation of fruit color and ethylene production are positively correlated (Cheng et al.2012).The higher the storage temperature, the higher the ethylene concentration in the environment, which will further accelerate the process of fruit yellowing.

Core browning is another major problem when storing Korla Xiang pears.Storage temperature and duration are the two major factors affecting core browning.Lowtemperature-induced core browning generally occurs early during storage.High temperatures or long storage times lead to senescence core browning, which generally occurs late during storage.We found that the main factor affecting the core browning of Korla Xiang pears is low temperature,i.e., -1.5°C.So, when there is no chilling injury, lower temperature sare more conductive to the control of core browning.

Early studies suggested that the higher the TSS content was, the lower the freezing point was (Chen et al.1990,Shen et al.2011).In addition, there are different freezing points in different parts of the fruit.The freezing point of the core is the highest, and the core is sensitive to chilling injury (Shen et al.2008).The fruits that were stored at-1.5°C had the highest TSS content.Hence, there was no core browning because fruits had a lower freezing point.And fruit storage at -1.5°C should be practiced only when higher TSS contents are ensured.At 2°C, core browning occurs late during storage.Hence, 2°C can be used for short-term storage.

Fig.7 Ethylene production and respiration rate of Korla Xiang pears were measured on the 1st, 3rd, 5th and 7th day at 20°C after cold storage for 90 days (A and B), 150 days (C and D) and 225 days (E and F) at -1.5, 0 and 2°C.Values are means±SD (n=3).The different letters above the error bars represent signifcant differences at P＜0.05 according to Duncan’s multiple range test at the same storage time.

5.Conclusion

In summary, by evaluating the effect of different storage temperatures and 1-MCP treatment combinations on fruit characteristics, we have determined the optimal storage conditions for different marketing times of Korla Xiang pears.For storage until New Year’s Day (a storage duration of 90 days), 2°C or 1-MCP combined with 2°C can be used.For storage until the Spring Festival (a storage duration of 150 days), 0°C or 1-MCP combined with 0°C can be used.For storage until May (a storage duration of 225 days), 1-MCP combined with -1.5°C can be used.However, fruits stored at-1.5°C should have a high TSS content to avoid chilling injury.

Acknowledgements

This study was supported by a grant from the National Key R&D Program of China (2016YFD0400903-06), the emarked fund for China Agriculture Research System(CARS-29-19), the Agricultural Science and Technology Innovation Program of the Chinese Academy of Agricultural Sciences (CAAS-ASTIP-2016-RIP-06).

Anna R, Maurizio G, Maristella V.2014.1-Methylcyclopropene

application, storage temperature and atmosphere modulate sensory quality changes in shelf-life of ‘Abbé Fétel’ pears.Postharvest Biology and Technology, 92, 87-97.

Argenta L C, Fan X T, Mattheis J P.2003.Influence of 1-methylcyclopropene on ripening, storage life, and volatile production by d’Anjou cv.pear fruit.Journal of Agricultural& Food Chemistry, 51, 3585-3864.

Cantin C M, Crisosto C H, Ogundiwin E A, Gradziel T, Torrents J, Moreno M A, Gogorcena Y.2010.Chilling injury susceptibility in an intra-specific peach Prunuspersica (L.)Batsch progeny.Postharvest Biology and Technology, 58,79-87.

Cao J K, Jiang W B, Zhao Y M.2007.Fruits and Vegetables Postharvest Physiological and Biochemical Experiment Instruction.China Light Industry Press, Beijing.pp.54-156.(in Chinese)

Chen C S, Nguyent K, Braddock R J.1990.Relationship between freezing point depression and solute composition of fruit juice systems.Journal of Food Science, 55, 566-569.

Cheng Y D, Dong Y, Yan H B, Ge W Y, Shen C G, Guan J F,Liu L Q, Zhang Y Y.2012.Effects of 1-MCP on chlorophyll degradation pathway-associated genes expression and chloroplast ultrastructure during the peel yellowing of Chinese pear fruits in storage.Food Chemistry, 135,415-422.

DeEll J R, Geoffrey B L, Behrouz E M.2016.Effects of multiple 1-methylcyclopropene treatments on apple fruit quality and disorders in controlled atmosphere storage.Postharvest Biology and Technology, 111, 93-98.

DeEll J R, Murr D P, Porteous M D, Rupasinghe H P V.2002.Influence of temperature and duration of 1-methylcyclopropene (1-MCP) treatment on apple quality.Postharvest Biology and Technology, 24, 349-353.

Fernández-León M F, Fernández-León A M, Ayuso M L,González-Gómez D.2013.Different postharvest strategies to preserve broccoli quality during storage and shelf life:Controlled atmosphere and 1-MCP.Food Chemistry, 138,564-573.

Gago C M, Guerreiro A C, Miguel G, Panagopoulos T, Sánchez C, Antunes M D.2015.Effect of harvest date and 1-MCP(SmartFreshTM) treatment on ‘Golden Delicious’ apple cold storage physiological disorders.Postharvest Biology and Technology, 110, 77-85.

Gago C M L, Guerreiro A C, Miguela G, Panagopoulos T,da Silva M, Antunes M D C.2016.Effect of Calcium chloride and 1-MCP (SmartfreshTM) postharvest treatment on ‘Golden Delicious’ apple cold storage physiological disorders.Scientia Horticulturae, 211, 440-448.

Gago C M, Miguel M G, Cavaco A M, Almeida D P, Antunes M D.2013.Combined effect of temperature and controlled atmosphere on storage and shelflife of ‘Rocha’ pear treated with 1-methylcyclopropene.Food Science and Technology International, 21, 94-103.

Gao M M, Zhou S, Guan J F, Zhang Y Y.2015.Effects of 1-methylcyclopropene on superficial scald and related metabolism in ‘Wujiuxiang’ pear during cold storage.Journal of Applied Botany and Food Quality, 88, 102-108.

Gao Q M, Li J, Li Y.2005.Literature review of researches on‘Kuerle Sweet Pear’.Nonwood Forest Research, 23, 79-82.(in Chinese)

Golding J B, Shearer D, McGlasson W B, Wyllie S G.1999.Relationships between respiration, ethylene, and aroma production in ripening banana.Journal of Agricultural &Food Chemistry, 47, 1646-1651.

Hu W R, Zhang Z Q, Ji Z L, Liu S Z, Zhang H L.2004.Changes of pericarp color and the content of anthocyanin and flavonoids in litchi pericarp during chilling-injuried temperature storage.Acta Horticulturae Sinica, 31, 723-726.(in Chinese)

Jia X H, Jiang Y B, Wang W H, Shen C M, Xia Y J, Wang Z H.2009.Present situation, existing problems and strategies of pear sales in supermarket.China Fruit & Vegetable, 6,50-52.(in Chinese)

Jia X H, Wang W H, Li S Q, Du Y M, Yu Q, Zhang F, He Z S.2014.The investigation of storage situation of ‘Korla Xiangli’pears in Xinjiang.China Fruit, 5, 75-78.(in Chinese)

Jia X H, Xia Y J, Wang W H, Tong W, Jiang Y B, Wang Z H.2014.Effects of harvest maturity combined with 1-MCP on storage quality and its physiological property of apple.Journal of Chinese Institute of Food Science and Technology, 14, 197-203.(in Chinese)

Jiang Y M, Joyce D C, Terry L A.2001.1-Methylcyclopropene treatment affects strawberry fruit decay.Postharvest Biology and Technology, 23, 227-232.

Kou L P.2001.Study on effection of temperature and gas on flesh browning of ‘Fuji’ apples.MSc thesis, Northwest A&F University, China.(in Chinese)

Li F J, Yang H Q, Zhang X H, Shu H R, Zhou J.2004.Effects of 1-MCP on ethylene synthesis and metabolism of apple during storage.Scientia Agricultura Sinica, 37, 734-738.(in Chinese)

Li G P, Jia H J, Li J H, Li H X, Teng Y W.2016.Effects of 1-MCP on volatile production and transcription of ester biosynthesis related genes under cold storage in ‘Ruanerli’pear fruit (Pyrusussuriensis Maxim.).Postharvest Biology and Technology, 111, 168-174.

Li L, Ban Z J, Li X H, Wang X L, Guan J F.2012.Phytochemical and microbiological changes of honey pomelo (Citrus grandis L.) slices stored under super atmospheric oxygen, low-oxygen and passive modified atmospheres.International Journal of Food Science and Technology,47, 2205-2211.

Makkumrai W, Anthon G E, Sivertsen H, Ebeler S E, Negre-Zakharov F, Barrett D M, Mitcham E J.2014.Effect of ethylene and temperature conditioning on sensory attributes and chemical composition of ‘Bartlett’ pears.Postharvest Biology and Technology, 97, 44-61.

Ougham H, Hörtensteiner S, Armstead I, Donnison I, King I, Thomas H, Mur L.2008.The control of chlorophyll catabolism and the status of yellowing as a biomarker of leaf senescence.Plant Biology, 10, 4-14.

Rizzolo A, Cambiaghi P, Grassi M, Zerbini P E.2005.Influence of 1-methylcyclopropene and storage atmosphere on changes in volatile compounds and fruit quality of conference pears.Journal of Agricultural and Food Chemistry, 53, 9781-9789.

Rizzolo A, Grassi M, Vanoli M.2014.1-Methylcyclopropene application, storage temperature and atmosphere modulate sensory quality changes in shelf-life of ‘Abbé Fétel’ pears.Postharvest Biology and Technology, 92, 87-97.

Shen C M, Wang L J, Wang W H, Wang R H, Tong W, Xia Y J, Jia X H.2011.Determination of the freezing point temperature of 12 pear cultivars and the correlation analysis of the impact factors.Journal of Nanjing Agricultural University, 34, 35-40.(in Chinese)

Shen J, Wang X D, Zhang Y F, Wang S Y, Liu B.2008.Experimnt on hyo-on storage of Kuala fragrant pear.Journal of Chemical Industry and Engineering, 59, 99-103.(in Chinese)

Sisler E C, Serek M.2010.Inhibitors of ethylene responses in plants at the receptor level: Recent developments.Physiologia Plantarum, 100, 577-582.

Sun X S, Wang W H, Wang Z H, Li Z Q, Zhang Z Y.2003.Effects of 1-MCP on physiological changes of ‘Jonagold’ apples at ambient temperature after harvest.Acta Horticulturae Sinica, 30, 90-92.(in Chinese)

Thomas H, Howarth C J.2000.Five ways to stay green.Journal of Experimental Botany, 51, 329-337.

Vanoli M, Grassi M, Rizzolo A.2016.Ripening behavior and physiological disorders of ‘Abate Fetel’ pearstreated at harvest with 1-MCP and stored at different temperatures andatmospheres.Postharvest Biology and Technology,111, 274-285.

Villalobos-Acuna M G, Biasi W V, Flores S, Jiang C Z, Reid M S,Willits N H, Mitcham E J.2011a.Effect of maturity and cold storage on ethylene biosynthesis and ripening in ‘Bartlett’pears treated after harvest with 1-MCP.Postharvest Biology and Technology, 59, 1-9.

Villalobos-Acuna M G, Biasi W V, Mitcham E J, Holcroft D.2011b.Fruit temperature and ethylene modulate 1-MCP response in ‘Bartlett’ pears.Postharvest Biology and Technology, 60, 17-23.

Wang G X, Wang Y S, Liang L S.2005.Studies on chilling injury and quality deterioration of Okubo peach under different storage temperature strategies.Forest Research,18, 114-119.(in Chinese)

Wang Z H, Jiang Y B, Wang W H, Hang B, Du Y M, Tong W,Jia X H.2014.Effects of different low storage temperatures on tissue browning and quality of ‘Dangshan Suli’ pears during shelf-life.Acta Horticulturae Sinica, 41, 2393-2401.(in Chinese)

Wang Z H, Wang W H, Tong W, Ding D D, Wang B L, Zhang Z Y.2011.Effects of different cooling methods on physiology and core browning of ‘Yali’ pear treated with 1-MCP.Journal of Fruit Science, 28, 513-517.(in Chinese)

Watkins C B.2006.The use of 1-methylcyclopropene (1-MCP)on fruits and vegetables.Biotechnology Advances, 24,389-409.

Watkins C B.2008.Overview of 1-methylcyclopropene trials and uses for edible horticultural crops.HortScience, 43, 86-94.

Watkins C B, Bramlage W J, Cregoe B A.1995.Superficial scald of Granny Smith apples is expressed as a typical chilling injury.Journal of the American Society for Horticultural Science, 120, 88-94.

Yamane A.1982.Development of controlled freezing-point storage of foods.Journal of Japanese Society of Food Science and Technology, 29, 736-743.

Wang Y, David S.2015.1-MCP efficacy in extending storage life of ‘Bartlett’ pears is affected by harvest maturity, production elevation, and holding temperature during treatment delay.Postharvest Biology and Technology, 103, 1-8.

Yang X T, Zhang Z Q, Pang X Q.2005.Effect of chlorophyll degradation on postharvest quality of fruits and vegetables.Journal of Fruit Science, 22, 691-696.

Zhang Z Q, Tian S P, Zhou Z, Xu Y, Qin G Z.2012.Effects of 1-methylcyclopropene (1-MCP) on ripening and resistance of jujube (Zizyphus jujuba cv.Huping) fruit against postharvest disease.LWT-Food Science and Technology,45, 13-19.

Zhou S, Cheng Y D, Guan J F.2017.The molecular basis of superfcial scald development related to ethylene perception and α-farnesene etabolism in ‘Wujiuxiang’ pear.Scientia Horticulturae, 216, 76-82.

Zhou X, Dong L, Zhou Q, Wang J W, Chang N, Liu Z Y, Ji S J.2015.Effects of intermittent warming on aroma-related esters of 1-methylcyclopropene-treated ‘Nanguo’ pears during ripening at room temperature.Scientia Horticulturae,185, 82-89.

Zhou Y C, Pan X P, Qu H X, Steven J R.2014.Low temperature alters plasma membrane lipid composition and ATPase activity of pineapple fruit during blackheart development.Journal of Bioenergetics & Biomembranes, 46, 59-69.