Effects of 1-methylcyclopropene on texture properties of Rabbiteye blueberry during long-term storage and simulated transportation

Rabbiteye Blueberry (Vacciniumashei) is a climacteric fruit and soft fruit (Dan & Nesmith, 2011). Texture is one of the main quality parameters accepted by consumers, including eating quality, and storability during handling, postharvest storage and transportation (Li et al., 2011a). The texture properties mainly include firmness, springiness, cohesiveness, gumminess, chewiness, and resilience. The decrease in firmness lead to fruits softening, could be the reliable parameters of texture properties evaluation of soft fruits (Li et al., 2011a, b; Tian et al., 2011; Jia et al., 2014). There was significant positive correlation between commodity rate, fruits softening, firmness, cohesiveness, springiness, gumminess, chewiness, and resilience, respectively. The firmness had a significant positive correlation with TSS and TA (Ji et al., 2014; Wang et al., 2014).


Introduction
Rabbiteye Blueberry (Vacciniumashei) is a climacteric fruit and soft fruit (Dan & Nesmith, 2011).Texture is one of the main quality parameters accepted by consumers, including eating quality, and storability during handling, postharvest storage and transportation (Li et al., 2011a).The texture properties mainly include firmness, springiness, cohesiveness, gumminess, chewiness, and resilience.The decrease in firmness lead to fruits softening, could be the reliable parameters of texture properties evaluation of soft fruits (Li et al., 2011a, b;Tian et al., 2011;Jia et al., 2014).There was significant positive correlation between commodity rate, fruits softening, firmness, cohesiveness, springiness, gumminess, chewiness, and resilience, respectively.The firmness had a significant positive correlation with TSS and TA (Ji et al., 2014;Wang et al., 2014).
There is little scientific literature pertaining to use 1-MCP treatments on texture properties of blueberries during storage and transportation.Moreover, the effects of 1-MCP on texture properties of blueberry during storage and transportation had still not been reported.Thus, the objective of this study is to assess the effects of 1-MCP on texture properties of rabbiteye blueberry of 'Gardenblue' fruit during long-term storage and simulated transportation.

Plant material
'Gardenblue' blueberry is grown in orchard, Majiang county, Guizhou province, in China.The blueberry fruits were hand-harvested on July 15, 2015, at 90% maturity (the fruit is blue and pedicel slightly red).Damaged and rotten blueberry fruits were eliminated, the fruits of uniform size without obvious damage were placed into 125 g punnets and transported to Guizhou engineering research center for fruit processing.

1-MCP treatment and storage conditions
The 288 punnets were randomly divided into four lots, each treatment for 72 punnets, the 12 punnets was packed into a commercial polyethylene bags, then transferred to cold storage, precooling at 1 °C for 12 h.The 0.14% 1-MCP (SmartFresh TM , Agrofresh Onc., USA) was used to create 0.0, 0.1, 0.2 and 0.3 μL L -1 in commercial polyethylene bags.After the treatment, the all fruits were stored at 0 ± 0.5 °C, 85% ~ 95% R.H., 12 punnets per 1-MCP treatment were sampled at 0, 20, 40, 60, and 80 days after storage, determined the texture properties, TSS and TA after removal of rotten fruit.

Simulated Commercial transportation conditions
Commercial transportation of Guizhou highway road conditions was simulated by using transportation simulator.After 40 and 80 days of storage, quickly put 8 punnets into a foam box with commercial cold pack to simulate the commercial transportation conditions at the average velocity of 100 km/h for 2 days at 25 °C.12 punnets per 1-MCP were analyzed for texture properties, TSS and TA for three replicates.

Texture properties
The force-time curves of blueberry fruits were determined by using a P/36R of TA.XT Plus texture profile analyzer (Stable Micro System Ltd., UK).The force was measured with the following instrumental settings: 2 mm/s of test speed, 1 mm/s of post-test speed, and auto-force trigger of 5.0 g.Each fruit was compressed and deformed to 30%.Thirty replicates, the same size fruits, were conducted for each treatment, the firmness, springiness, cohesiveness, gumminess, chewiness, and resilience were determined based on the force-time curve (Singh et al., 2013).

TA and TSS
TA was determined in triplicate by pH Meter (model PHS-3C, ONESA Scientific Onstrument Co., Ltd, Shanghai, China), using 0.1 N NaDH up to the pH 8.2, and expressed as g citric acid kg -1 (Xie et al., 2016).TSS of fruits were measured in triplicate using a hand-held refractometer (PAL-1, ATAGD, Tokyo, Japan) at 25 °C and expressed as % (Xie et al., 2015).

Statistical analysis
This study was executed by using a randomized factional experimental design.Statistical tests were carried out using the SPSS® Computer program, Version 22.0 (SPSS Statistical Software, Onc., Chicago, OL, USA).Significant differences between different storage time and treatments by using Duncan's multiple range test at the 5% level.The overall value and their comparison were used when the interactions were discovered not significant.

Firmness
Fruit firmness of blueberry is an important parameter to evaluate the fruit softening.The firmness in control and 0.1 μL L -1 1-MCP treated blueberries decreased during 80 days of storage.However, the firmness in 0.2 μL L -1 and 0.3 μL L -1 1-MCP treated blueberries increased then decreased during storage (Table 1), the firmness increase with the water loss after harvest was previously found by Allan-Wojtas et al. (2001) and Chiabrando & Giacalone (2011).The firmness of blueberry fruit treated with 0.3 μL L -1 1-MCP was maintained at higher levels.The 0.3 μL L -1 1-MCP can effectively delay the decrease of blueberries firmness after 80 days of storage plus 2 days transportation.These data clearly indicated that 0.3 μL L -1 1-MCP delayed the softening of blueberry fruit.Retention of blueberry fruits firmness is of great importance during long term storage and transportation.This work reported that 1-MCP treatments conquered decline in firmness of blueberry fruit.Similar to firmness, certain reports claim that 1-MCP retard the reduction in firmness and delay the softening of blueberry (Dan & Nesmith, 2011;Wang et al., 2013bWang et al., , 2014;;Ji et al., 2014;Wang et al., 2015).

Springiness
On this study, the springness of all treatment blueberries decreased during storage and simulated transportation (overall values) (Table 1), the springness of blueberries treated with 0.3 μL L -1 1-MCP was maintained at higher levels.The blueberries treated with 0.3 μL L -1 1-MCP can effectively delay in this decrease of blueberry springiness after 80 days of storage plus 2 days transportation.These changes occurred much slower in the blueberries treated with 0.2 and 0.3 μL L -1 1-MCP than the blueberries treated with control and 0.1 μL L -1 1-MCP.The previously reported that 1-MCP delayed springiness changes in grape (Li et al., 2011b), pears (Wang et al., 2013a).

Cohesiveness
The cohesiveness of all treatment blueberries is decreased until to 40 days then progressively increased during 80 days of storage (Table 1).The cohesiveness of blueberries treated with 0.2 μL L -1 1-MCP was retained at higher levels, the 0.3 μL L -1 1-MCP treatment can effectively delay the decrease of blueberry cohesiveness after 80 days of storage plus 2 days transportation.As in our study, the cohesiveness of blueberries is not affected by 1-MCP treatments, in agreement with jujube (Xie et al., 2009) and apple (Li et al., 2013;Jia et al., 2014).However, delay in the changes of cohesiveness was recorded for grape (Li et al., 2011b) and pear (Wang et al., 2013b).

Gumminess
The gumminess of blueberries in control and treated with 0.1 μL L -1 1-MCP decreased during storage and simulated transportation.However, the gumminess of blueberries treated with 0.2 and 0.3 μL L -1 1-MCP increased until to 40 days of storage then reduced during storage and simulated transportation (Table 1).The 0.2 and 0.3 μL L -1 1-MCP were more effective treatments in maintaining higher gumminess (overall) during storage and simulated transportation.The reduction in gumminess loss of fruit treated with 1-MCP is in agreement with fruit senescence.

Chewiness
The all treatments chewiness decreased during storage and storage plus 2days transportation (Table 1).The fruits treated with 1-MCP showed slightly higher than the control, and the difference among the treatment during storage and simulated transportation.The fruits treated with 0.3 μL L -1 1-MCP were the most effective in maintaining higher chewiness level (overall values) during storage and simulated transportation.This result shows that the 1-MCP concentrations had a positive impact on the blueberry chewiness.Previous studies demonstrated that 1-MCP delayed the drop of grape chewiness (Li et al., 2011b), pear (Wang et al., 2013b), apple (Li et al., 2013;Jia et al., 2014), and peppers (Guo et al., 2015).Resilience Control 0.17 de 0.16 fg 0.15 hij 0.18 cd 0.15 ghij 0.18 cd 0.14 lm 0.15 A 0.1 μL L -1 1-MCP 0.17 de 0.16 f 0.15 ijk 0.19 b 0.15 ghi 0.18 cde 0.14 kl 0.16 A 0.2 μL L -1 1-MCP 0.17 de 0.17 e 0.15 ijk 0.18 cd 0.18 bc 0.18 cd 0.14 lm 0.16 A 0.3 μL L -1 1-MCP 0.17 de 0.16 fgh 0.15 ijk 0.20 a 0.13 m 0.18 cd 0.15 jk 0.16 A Dverall 0.17 ab 0.16 ab 0.15 b 0.19 a 0.15 b 0.18 a 0.14 b Different letters in each column represent significant differences between the ripe stage (P < 0.05).All measures were performed in three independent samples.

Resilience
The resilience showed no consistent change during storage and transportation.Resilience of all treatment blueberries is decreased until to 40 days of storage then rose (Table 1).On this study, the resilience linearly decreased with storage time(overall), 1-MCP had no effects on the blueberries resilience during storage and transportation.The decline in resilience of blueberries treated with 0.2 μL L -1 1-MCP was slower than other treatments.This result shows that the 1-MCP had a slightly effect on the resilience of the blueberry.Similar to our study, there were negligible differences on resilience for grape by1-MCP treatments (Li et al., 2011b).However, 1-MCP had a significantly effect on the resilience of pear (Wang et al., 2013b) and apple (Li et al., 2013;Jia et al., 2014).

TA and TSS
The TA in all treatment blueberry increased until to 20 days or 40 days, then decreased during storage (Figure 1A), however, the TA of blueberries for 80 days of storage plus 2 days transportation was significantly higher than that of stored at80 days.The TA of blueberries treated with 0.3 μL L -1 1-MCP was kept at lower levels after 80 days of storage plus 2 days of simulated transportation.These changes of blueberries treated with 0.3 μL L -1 1-MCP occurred much slower than other treatment.Similar to our study, 1-MCP can effectively delay the drop of TA in blueberry (Dan & Nesmith, 2011;Chiabrando & Giacalone, 2011;Ji et al., 2014), it mainly by regulating the balance between malate biosynthesis and degradation (Liu et al., 2016).
TSS is a key factor for fruit quality and acceptability of soft fruit.TSS changes of all treatment blueberries during storage and simulated transportation are showed in Figure 1B.TSS level at the preliminary stage of storage was 15.97% and decreased gradually during storage and simulated transportation in all treatment blueberries.As in this study, in Austin, Bright well, and Premier, TSS was minimal affected by 1-MCP (Dan & Nesmith, 2011).However, 1-MCP retard the decrease of TSS was recorded for blueberry (Chiabrando & Giacalone, 2011;Ji et al., 2014). 191/192 191

Correlation analysis
Table 2 displays the correlation among texture properties, TA and TSS during storage and transportation.These findings mirrored the trend reported for all the parameters (firmness, springiness, cohesiveness, gumminess, chewiness, resilience, TA and TSS).A positive correlation among the texture properties, TA and TSS was pointed out.The firmness was strongly correlated with springiness, gumminess, chewiness, resilience, TA and TSS.The springiness was strongly correlated with TSS, resilience, cohesiveness, TA, chewiness, and gumminess.
The cohesiveness was strongly related to resilience, TA and TSS.The cohesiveness was strongly associated with resilience, TA and TSS.The gumminess was strongly correlated with chewiness and resilience.The chewiness was strongly correlated with resilience.The resilience was strongly correlated with TSS, weaker correlation with TA.Similar to our study, there was significant positive correlation among firmness, springiness, cohesiveness, gumminess, chewiness, resilience, TA and TSS, respectively (Li et al., 2011b;Tian et al., 2011;Li et al., 2013;Jia et al., 2014).

Figure 1 .
Figure 1.TA (A) and TSS (B) of blueberries during storage and simulated transportation.Different letters in each column represent significant differences between the ripe stage (P < 0.05).All measures were performed in three independent samples.

Table 1 .
Texture properties during storage and simulated transportation.

Table 2 .
Correlation analysis among parameters.