Professor Xin Guang of Shenyang Agricultural University, et al.: Simulate the effect of different harvesting methods on the quality of Fir nigna, under the condition of cold chain temperature

It is a high-protein, low-fat edible fungus with high umami amino acid content, in addition to antioxidant active ingredients
such as polyphenols.
However, the fruiting body of P.
nignais has high moisture content and no epidermal protection, which is vulnerable to mechanical damage in picking, transportation, storage and other links, which greatly affects the development of
P.
nigrica industry.

At present, the research on Chicken fir fungus is mainly focused on cultivation and chemical composition analysis, and the research on the effect of different harvesting methods on the quality of Chicken fir fungus black skin under cold chain temperature has rarely been reported
.
Wang Zicheng, Wang Yafei, Xin Guang* and others from the College of Food Science of Shenyang Agricultural University explored the effects of it on the sensory, physiological, nutritional and flavor indexes of Chicken fir black skin fungus through two different harvesting methods, so as to determine the best harvesting method for storage of Chicken fir black skin fungus under cold chain temperature conditions, in order to provide theoretical reference for the postharvest storage and preservation of Chicken fir fungus and promote the development of
edible fungus industry.

1.
Effect of harvesting method on sensory quality of P.
nigricus

Texture characterization analysis

The changes in the texture indexes of the cap are shown in Table 1, and the hardness, cohesion (except for day 5), adhesiveness and chewing of the cap are the most in the pulling group
.
Explanations showed that the harvesting method of pulling at 10 °C would maintain the better texture of P.
nigricus
.

Color analysis

As shown in Table 2, under the condition of 10 °C, the L* value of the cap of P.
nigra showed a decreasing trend with the extension of storage time, and the color variation range of P.
nigra was larger, possibly because the harvesting method of cut was more likely to activate polyphenol oxidase, resulting in browning
.
In summary, under the cold chain temperature storage conditions, the harvesting method of pulling can reduce the browning
of the cap of P.
nigricus.

2.
Effects of harvesting methods on respiration rate and ethylene release of P.
nigricus

The greater the respiration intensity, the more vigorous the physiological metabolism of edible fungi and the shorter
the storage period.
On day 1 of storage, the respiration rate of the cut treatment group was 1.
5 times that of the extraction treatment group (Figure 1A).

The respiration rates of the two harvesting methods peaked at 3 d, and the respiration rates were 391.
87 mg/(kg·h) and 385.
23 mg/(kg·h),
respectively.
After fractionation, the respiratory intensity of P.
nigra increased by 1.
01~1.
62 times
.

The ethylene release amount during storage of P.
nigricum is shown in Figure 1B, on the first day of storage, the ethylene release in the pulling treatment group is 4.
5 times that of the cut, but the ethylene release rate in the cut treatment group is greater than that in the pulling treatment group, which may be because the mechanical damage caused by cutting makes the ethylene of P.
nigricum produce wounded ethylene, resulting in a rapid increase
in ethylene release.
The peak of ethylene release and the peak of respiration intensity of the two harvesting methods of cutting and pulling basically coincided, which is a typical respiratory leap type
.
In summary, the harvesting method of cutting kept the initial respiratory intensity of P.
nigra at a high level
.

3.
Effect of harvesting method on the nutritional quality of Fir nigna

The soluble sugar content of P.
nigra increased first and then decreased during storage, with the pulling group peaking on day 7, and the cutting treatment group having a higher soluble sugar fraction in the later stage of storage (Fig.
2A
).
。 With the extension of storage time, the soluble protein content of P.
nigra collected by the two methods showed an overall upward trend (Fig.
2B), and the soluble protein content of P.
nigra harvested after 5 days was significantly higher than that in the pulling treatment group (P<0.
05), which may be due to mechanical damage to enhance oxygen permeability, accelerate respiratory metabolism of P.
nigra, and produce more small molecule soluble proteins<b11>.
As shown in Fig.
2C and D, under the storage conditions of 10 °C, the contents of polyphenols and flavonoids in the harvested method were significantly higher than those in the pulling treatment group (P<0.
05).
<b12> In summary, the harvesting method of cutting was more conducive to increasing the nutrient content of
P.
nigricus.

4.
Effect of harvesting method on the flavor quality of Fir nigricus black-skinned

Analysis of changes in amino acid content

The content of aspartic acid in P.
nigra decreased first and then increased, while the content of glutamate showed an upward trend (Tables 3 and 4).

Among them, the content of glutamic acid was significantly higher than that of aspartic acid, and the content of glutamate in the cutting and pulling treatment groups was 11.
1~61.
0 times and 8.
6~31.
0 times
of aspartic acid content, respectively.
The total umami amino acid content of Chicken fir nigra was significantly higher than that in the pulling treatment group, which may be that the harvesting method of cut made the protein degradation rate of Chicken fir nigra higher than the rate
of conversion of amino acids into volatile substances.
In summary, the cutting harvesting method made the umami amino acid content
of Chicken fir fungus niggara higher.

Analysis of changes in taste values

As shown in Figure 3, at a storage temperature of 10 °C, the umami values of P.
nigrica were harvested by pulling and cutting, and the umami values of P.
nigrica decreased with the extension of storage time, and reached the minimum values at 9 days of storage, 14.
54 and 10.
87
, respectively.
The umami value of P.
nigrica was significantly higher than that in the cutting treatment group (P<0.
05), and the bitterness value was opposite to the change of umami value, but there was no significant relationship between the bitter value and the change of umami value of P.
nigrica in the harvesting method, indicating that the harvesting method of cut had a greater<b11> influence on the taste value.
In summary, the umami value of the black-skinned chicken fir fungus was large
.

Analysis of nucleotide and EUC changes

As shown in Figure 4, the content of 5'-IMP in the cut treatment group was significantly higher than that in the pulling treatment group (P<0.
05), and the content of 5'-XMP in the plucked P.
nigra was significantly higher than that in the cutting treatment group (the difference was 1.
20~1.
36 times).
<b10> However, the content of 5'-AMP and 5'-GMP of P> was not significant (P0.
05), but the content of 5'-AMP and 5'-GMP were the main contributors
to the umami of P Fir nigra in the whole storage process.
The total nucleotide content of the four nucleotides was shown in Figure 4E, and on the 3rd and 5th days, the total nucleotide content in the extraction treatment group was higher than that in the extraction treatment group, and after 5 days, the total nucleotide content in the extraction treatment group was higher than that in the extraction treatment group, especially on the 9th day, the difference between the two groups was significant (P<0.
05), reaching 1.
1 times<b12>.
In summary, the total nucleotide content of the harvested chicken fir nigra was relatively high
.

As shown in Figure 4F, except for the 9th day, the EUC of the cutting treatment group was significantly higher than that of the pulling treatment group (P<0.
05), and the EUC range of P.
nigra harvested by cutting and pulling was 5.
9~18.
2 and 5.
9~15.
6<b10>, respectively.
In the later stage of storage, both harvesting methods had a large EUC, indicating that the mymas nigra had a higher umami value
in the later stage of storage.
In summary, the cutting harvesting method makes the umami value of the black fir fungus higher
.

Analysis of changes in the relative content of C8 volatile compounds

As shown in Figure 5, except for the 5th and 13th days, the relative content of C8 volatile compounds of P.
nigra was greater than that in the pulling treatment group, especially on the 7th day, the difference between the two groups was the largest, reaching 1.
27 times
.
This may be related to the intensity of breathing, as lower respiratory intensity allows the aroma of Firidium niggaris to maintain a higher aroma
.
As shown in Figure 1, on day 7, the respiration intensity of the extraction group was significantly lower than that in the cut treatment group, while in Figure 5, the total content of C8 volatile compounds in the cut treatment group on day 7 was higher than that in the extraction group
.
In summary, the content of volatile compounds in the harvested Chicken fir nigra was relatively high
.

Conclusion