Liu Dunhua, researcher at Ningxia University, et al.: Effects of postharvest 1-methylcyclopropene and spontaneous modified atmosphere treatment on softening and related physiological changes of persimmon stored at ice temperature

Diospyros kaki L.
Huoshi is one of the main persimmon varieties in China, rich in a variety of nutrients, with antihypertensive, anti-lipid peroxidation, anti-tumor, immunomodulatory and other health care effects, deeply loved
by consumers.
Persimmon is a typical respiratory leap fruit, with large yield and concentrated harvest season, obvious softening will occur after harvest, and it is more susceptible to mechanical damage and rot after softening, which greatly limits the long-distance transportation of persimmon fruit and its shelf life, so it is particularly important
to explore the influence of storage technology on softening and storage quality during postharvest storage of persimmon.

Ma Qin, Liu Dunhua* of the College of Food and Wine of Ningxia University, and Li Jiangkuo of the National Engineering Research Center for Agricultural Products Preservation (Tianjin), Li Jiangkuo* of the Tianjin Key Laboratory of Postharvest Physiology and Storage and Preservation of Agricultural Products, used 1-methylcyclopropene (1-MCP) and modified atmosphere storage (MA) at ice temperature (-0.
5±0.
3) °C to retain sepals and remove sepals from the environmental gas content of persimmon fruits, The effects of 1-MCP, MA and collaborative treatment (1-MCP+MA) on the softening of persimmons with and without sepals during storage were discussed from the perspectives of physiological indexes and nutritional indexes, which provided a theoretical reference
for the storage and preservation technology of postharvest persimmon fruits.

1.
Effect of different treatments on hardness during ice temperature storage of persimmon

As shown in Fig.
1A and B, under the condition of ice temperature storage, the hardness of persimmon peel decreased with the extension of storage time, and the hardness of the control group after the 15th day of storage period was basically lower than that of other treatment groups, and the decrease was the largest
.
By the end of the ice-temperature storage period, the hardness of persimmon peel with sepals and without sepals were 1-MCP+MA>1-MCP>MA> controls, among which the hardness of the sepal-free control group was higher than that of the sepal-free control group, and the hardness of other sepal-free treatment groups was higher than that of the sepal-treated group
.

As shown in Fig.
1C and D, until the end of the ice-temperature storage period, the pulp hardness of sepal persimmon decreased except for 1-MCP+MA compared with the initial hardness, and the pulp hardness of 1-MCP+MA>1-MCP>MA> control (Fig.
1C).
The 1-MCP treatment group increased the initial hardness by 14.
1%, and the 1-MCP+MA treatment group did not change significantly compared with the initial hardness, and the pulp hardness was 1-MCP> 1-MCP+MA>MA> control (Figure 1D), and the pulp hardness of sepalless persimmon fruit was significantly greater than that of sepal persimmon fruit (P<0.
05).
<b10>

Hardness is the intuitive expression of fruit softening, through which the suitability of storage conditions can be evaluated, in summary, removing sepals treatment can effectively delay the decrease of persimmon hardness compared with retaining sepals, and 1-MCP+MA combined treatment has a better effect in maintaining persimmon hardness, thereby effectively protecting the integrity
of persimmon tissue.

2.
Effects of different treatments on the activity of enzymes related to cell wall degradation during ice temperature storage of persimmon

As shown in Figure 2A~D, when persimmons were stored at ice temperature until the 45th day, the CX and PG activities of the control group with and without sepals were higher than those in other treatment groups, and the activity of CX and PG in the treatment group without sepals was slightly lower than that in the sepal group, indicating that when stored for 45 days, 1-MCP, MA and 1-MCP+MA treatments all inhibited the activity of CX and PG of persimmons, and the combined desepal treatment had a better
effect 。 From the 45th day to the end of the storage period, the CX and PG viability of the sepal control group decreased sharply, and the lowest activity was lower than that in the other treatment groups at the end of the storage period.
However, the vitality of CX and PG in the sepal-free control group decreased slowly, and was still higher than that in other treatment groups at the end of the storage period, indicating that 1-MCP, MA and 1-MCP+MA could inhibit CX and PG activity in the middle and late stages of storage, and the inhibitory effect of combined with decalyx treatment on CX and PG activity was better than that of sepal retention, especially in the sepal-free 1-MCP treatment group
.

As shown in Figures 2E and F, during ice temperature storage, by day 60, the β-Gal activity of the 1-MCP+MA treatment group was significantly greater than that of the other treatment groups (P<0.
05), and the β-Gal activity of the MA treatment group with sepals was lower than that of the control group, and the inhibition effect of sepal treatment was significant compared with desepal treatment, indicating that sepals combined with MA treatment could inhibit β-Gal activity<b10> better.

3.
Effect of different treatments on the composition of gas components in the box during ice temperature storage of persimmon

As shown in Fig.
3A and B, under ice temperature conditions, with the extension of storage time, the CO2 volume fractions
of persimmon fruits with and without sepals treated by MA and 1-MCP+MA increased during ice temperature storage 。 At the end of storage, the CO2 volume fraction in the persimmon storage environment of the MA treatment group was 2.
9%, and the CO2 volume fraction in the storage environment of persimmon fruit in the sepal 1-MCP+MA treatment group was 2.
3%, and the increase rate during the whole storage period was MA>1-MCP+MA.
The CO2 volume fraction in the persimmon storage environment of the sepal-free MA treatment group was 2.
3%, and the CO2 volume fraction in the persimmon storage environment in the sepal-free 1-MCP+MA treatment group was 2.
4%, and the rise rate during the whole storage period was 1-MCP+MA>MA.
The CO2 volume fraction of other treated persimmons did not change
significantly during ice temperature storage.
Compared with the results of sepal treatment, the CO2 volume fraction in the sepal-free treatment box was lower overall, indicating that the retention of sepals enhanced the respiration of persimmon fruits, and MA treatment could maintain high CO2 and low O2 balance through gas exchange in the box, so that MA combined with sepal retention and ice temperature storage treatment had a significant
effect on maintaining a certain CO2 level in the storage environment.

As shown in Fig.
3C and D, with the extension of storage time, the O2 volume fraction of sepal persimmon decreased at a rate of MA>1-MCP+MA, and by the end of the storage period, the O2 volume fraction in the MA group was significantly lower than that in other treatment groups (P<0.
05), and there was no significant difference in the O2 volume fraction decrease rate in the sepal combined with MA and 1-MCP+MA treatment groups.
There were no significant changes<b10> in the 1-MCP with and without sepals and the control group.
It can be seen that MA treatment has the most effective
effect on the reduction of O2 volume fraction in the storage environment when sepals are present.

4.
Effects of different treatments on respiration intensity and ethylene formation rate during ice temperature storage of persimmon