In the early '90s, the United States began to commercialize crude vegetables on a large scale, especially with lettuce, kale, and carrots. This kind of processed vegetables are loved by consumers in fast-paced big cities because of their hygienic, fast, fresh and healthy advantages.
In some large supermarkets in China, although there are similar crude products, they mainly focus on tropical fruits that are not easy to preserve, while relatively few vegetable rough products, mainly on vegetables with sheath leaves such as coconut white, corn and bamboo shoots.
At room temperature (25 2C°C), it is very sensitive to ultraviolet C, and we can use this to quickly determine the optimal radiation dose, which meets the requirements of the pre-experiment.
We conducted a total of six sets of experiments, and each group received an irradiation dose of 106kj m2 (2 min.) 12 (4 min.) 18(6 min.) 24 (8 min.) 30 (10 minutes) and 636kJ m2 (12 min).
From Figure 4In 1, we can see that the control group began to show significant greening on the second day of storage; On day 3, the 2-, 4-, and 6-minute treatments were partially greened; However, the 8-, 10-, and 12-minute treatments showed no significant greening.
Therefore, we can conclude that the effect of UV-C inhibition of greening is positively correlated with UV-C dose.
After analysis Figure 42 in the brightness index and whiteness index, the following conclusions can be drawn: on the second day, the effect of the control and 6-minute treatments was significantly lower than the average; On the third day, the 4-minute and 8-minute treatments were significantly more effective than the other treatments, and the 12-minute treatment was slightly less effective.
At the same time, according to Figure 4The whiteness index (WI) in 2 shows that the difference between the treatments is not significant the next day, except for the control; On the third day, the whiteness effect of the 8-minute treatment was significantly better than that of the other treatments, and the difference was significant (p<0.).05)。
This may be due to the fact that more than 8 minutes of UV-C treatment time will over-oxidize the skin and promote the browning of sunflower white, thereby increasing the uncertainty of the treatment effect and also increasing the application cost.
Conversely, treatment times of less than 8 minutes may lead to insufficient inhibition effect, while treatment of 0 to 6 minutes may lead to the recurrence of greening in the later stage of the cocoon.
Open-air sales are mainly on the roadside, with daily sales from 6 a.m. to 9 a.m. and 4 p.m. to 7:30 p.m. This sales environment is lit by natural light, with about 6-7 hours of sunlight per day, temperatures between 23-33 degrees Celsius, and greenery is often seen during morning sales.
1.The second type of farmers' market: the sales time is roughly from 4 a.m. to 5 p.m., the light source is mainly a mixture of light and natural light, the light time is more than 12 hours, the ambient temperature changes in the range of 20-28, and the phenomenon of greening gradually appears after 8 a.m.
2.The third type of medium-sized supermarket: usually equipped with a dedicated open freezer and packaged with plastic wrap, the sales time is from 7 a.m. to 9 p.m.
The light source type is pure light, the illumination time is more than 13 hours a day, the ambient temperature fluctuates between 8-15, and the greenery phenomenon will be postponed until the afternoon.
Large supermarkets will be equipped with atomised hydration units, but the freezer units will not be used for vegetable sales, only between 8 a.m. and 10 a.m. daily**. Supermarket lighting uses pure light, which is higher than that of medium-sized supermarkets, and the light hours are more than 15 hours a day.
The air conditioner will maintain the ambient temperature fluctuating between 20-25C, and the greenery usually occurs at noon on the first day of sale. It should be noted that due to the semi-self-service environment of the supermarket, each time the goods are picked up, the temperature will change, so the supermarket greens faster than the laboratory.
In addition, the smaller the diameter of the callus, the faster the greening rate. Under the experimental storage conditions of medium-sized supermarkets, the greening rate of A. cocoonus was the slowest, which was helpful to analyze the specific changes of various enzyme activities in A. cocoon.
Therefore, we chose continuous light exposure at 101C for 24 h as the formal experimental storage conditions.
The study on the effect of UV-C treatment on the quality of Callus palena found that UV-C treatment could effectively reduce the weight loss rate and delay water loss, and there were significant differences between the treatment group and the control group on the 6th and 8th days.
In addition, UV-C treatment can also maintain the brightness and whiteness index of the white, avoiding a significant reduction during storage. The specific data showed that the brightness and whiteness index of the control group were significantly higher than those of the treatment group from the 4th to the 8th day, but the whiteness index of the treatment group decreased by only one-third of that of the control group at the end of storage.
Therefore, UV-C treatment is an effective way to protect the quality of cocoon.
During storage, the hue and chromaticity values of the control group increased significantly, from 95 at day 006 and 1239 increased to 8 on the 8th day and 10271 and 4213.
Conversely, the tonal values of the treatment group remained basically unchanged, indicating that there was no significant change in the color contrast of the treatment group. The color values of the control group increased significantly, which may be due to the significant increase in color saturation in the control group due to greening.
The contents of chlorophyll a, chlorophyll b and total chlorophyll in the control group increased significantly with the extension of storage time, which were significantly higher than those in the treatment group (P<005）。These data suggest that light exposure promotes the synthesis of large amounts of chlorophyll from the rhombic epidermis while using 4The treatment of 24 kJ M2UV-C could effectively inhibit the biosynthesis of chlorophyll from Rhonine white, thereby maintaining the appearance quality of Rhizophyllum spp. during storage.
After two days of storage, the cutability of control white was significantly improved, and there was a very significant difference on the sixth day (P<0.).01), and before the end of Tibet, they were significantly higher than those of the treatment of sunflower (P<0.).05)。
The cleavability of the treated water chestnut remained basically unchanged throughout the storage period, and the average value of the 6 times remained at 7429±2.There was no significant difference between 56 and above.
Since the accumulation of lignin will affect the cleavability of sunflower white, increase the texture of water chestnut white, and finally reduce the quality of water chestnut white 1431. Therefore, lignin staining was performed on the sunflower white sections on the eighth day of storage to understand the lignin type and distribution.
From Figure 45 It can be seen that the pink dots on the control sunflower white are g-type lignin monomers, which are mainly distributed in the periphery of the cross-section of water chestnut white, while no obvious discoloration was found in the treatment of zhibai.
According to Figure 46 It can be seen that although neither the control Lingbai nor the treatment Zhibai showed the orange color of the S-type lignin monomer, the cross-sectional ** part of the control Zhibai showed a large amount of yellow-brown of the G-type lignin monomer, which was significantly more than that of the treated Lingbai.
Taken together, these results indicate that Rhobidon mainly produces g-lignin monomers.
To sum up, through 4With 24 kJ MUV-C treatment, we found that it could inhibit the formation of G-type lignin during the storage process, and at the same time reduce the water consumption of water from physiological and biochemical reactions, which ultimately prevented the improvement of the texture of water chestnut, reduced the rate of weight loss of water chestnut, and maintained the taste of water chestnut.
Through staining experiments, we found that UV-C can slow down the production of lignin in rhogyna. To validate this conclusion, we further measured the changes in total lignin and total cellulose content in the control and treatment of Ryba.
The data showed that the total lignin and total cellulose content in the body showed an overall upward trend during storage. From the 6th day onwards, there was a significant difference in the total lignin content between the control and the treatment (P<0.).05）；On the 8th day, there was also a significant difference in the total cellulose content between the control sunflower and the treatment (P<0.).05）。
Table 43 The data showed that the difference between the control and treatment groups began to be significant on day 4 and reached a very significant level on day 8. This trend coincides with the cleavage change of Kwai white, which may be due to the fact that UV-C delays the weight loss rate and promotes the production of lignin and cellulose.
In addition, the experimental results show that 4The 24 kJ MUV-C treatment significantly reduced the production of total lignin and total cellulose in white.
L-phenylalanine ammonia-lyase (PAL) plays a key role in plant secondary metabolism and can catalyze the production of cinnamic acid from phenylalanine, which in turn synthesizes lignin.
Therefore, measuring PAL activity can help us understand the effect of ultraviolet light on lignin synthesis. The study data showed that the PAL activity of the control P. rhodospermum reached the highest value on the 4th day, which was consistent with the time point of the first greening of Rhizombica spp., and then gradually decreased, and did not participate in the further greening process of Rhodophyllum spp.
Both cut damage and environmental stresses (e.g., UV light) can lead to an increase in PAL activity. The results show that 4UV treatment at 24 kJ m2 increased the PAL activity of Rhombocystis in response to environmental stress at the beginning of the experiment, but did not inhibit the synthesis of cinnamic acid.
To determine how ultraviolet light inhibits lignin synthesis, we also need to continue to study other lignin catalytic enzymes.
The FRAP method and the DPPH method are two basic methods for detecting the antioxidant activity of vegetables, and by comparing the FRAP and DPPH values of different vegetables, you can understand the strength of the antioxidant activity of different vegetables.
The ferrous ion reducing force method (FRAP method) is to characterize the strength of the antioxidant activity of vegetables by measuring their Fe2+ content. From Figure 48 shows that the data showed a downward trend in the first two days of storage, began to rise again on day 4, and began to show a significant difference on day 6 (p < 0.).05）。
At the beginning of the experiment, the Fe2+ content of vegetables in the control group was significantly higher than that in the treatment group, which may be related to the oxidation of UV-C. The downward trend after day 6 in the control group was also consistent with the change in total phenol content, while the extremely significant difference (p < 0.) was observed in the treatment group on day 801) also indicates 424 kJ m UV-C treatment had a significant effect on improving the antioxidant activity of white vegetables.
By calculating the free radical scavenging rate by the dpph method, the strength of antioxidant activity of vegetables can be inferred. It was found that there was a positive correlation between DPPH radical scavenging and total phenol content, which was also verified in this experiment.
From Figure 48 It can be seen that the control water rhombus increased slightly on the 6th day and basically remained at 820.about 12%, while the treated whites maintained an upward trend throughout the storage period, and there were significant differences with the control group on the 2nd, 6th and 8th days (P<0.).05）。
The experimental results show that 424 kJ MUV-C treatment could improve the white dpph radical scavenging capacity.
After the analysis of experimental data, we can conclude that under the condition of 25C 2C, short-wave ultraviolet (UV-C) treatment of rough water chestnut white can effectively maintain its appearance quality.
Of these, 4The UV-C treatment at 24 kJ m had the best effect, and the incidence of white epidermal greening was the lowest, which was 3182121.06kj/m2。
In contrast, the incidence of greening in the same amount of UV-C treatment was significantly higher. In addition, high-dose UV-C treatment (530kJ m2 and 636 kJ m2) did not show a significant advantage over the optimal treatment, which may increase the cost of treatment and also increase the incidence of rhombic browning, given the generalization perspective.
In a 10C light environment, 4The 24 J MUV-C treatment could maintain the surface brightness value (L) and white value (Wi) basically stable by inhibiting the increase of chlorophyll content in the epidermis of Rhobic.
In addition, this treatment increases peroxidase activity (CAT) and reduces lignin (G-type) and cellulose formation, thereby maintaining the toughness of the white skin while reducing the rate of weight loss.
However, since UV-C has no positive effect on the activity of alanine ammonia-lyase (PAL), a key enzyme in lignin synthesis, further measurement of the activities of quality-catalyzed enzymes such as 4Cl, C4H and CAD is needed to determine the inhibition mechanism.
Experimental data show that UV-C can stimulate the antioxidant response of sunflower white, and strengthen the antioxidant system by increasing the concentration of phenolic compounds in the body and enhancing the antioxidant CAT activity.
Notably, although UV-C does not have a significant effect on antioxidants such as ascorbic acid, guaiacol peroxidase, and ascorbate peroxidase, the stress response it induces is sufficient to enhance the antioxidant capacity of Kwai Bai.