CN111616207B - Method for selecting optimal harvesting period of non-respiratory jump type fruit after picking and cold storage - Google Patents

Abstract

The invention discloses a method for selecting the optimal harvest time of non-respiratory jump type fruits after being picked and refrigerated, which comprises the following steps: picking when the non-respiratory jump type fruits grow to the mature period on fruit trees, picking at least in 3 stages, wherein the picking interval time of each stage is 3-4 weeks, storing the fruits in a refrigerator corresponding to the fruit variety after picking, detecting the respiratory intensity of the fruits during the storage period, and selecting the stage with the minimum respiratory intensity to determine the optimum picking stage of the fruits of the variety. Also provides a storage method of the non-respiratory transition type fruit, which comprises the following steps: 1) Selecting the optimal harvesting period of the variety of fruits according to the method; 2) Picking fruits according to the selected optimal picking period, and storing the picked fruits in a refrigerator corresponding to the variety for storage. The fruits harvested according to the harvesting period determined by the method have high fruit quality, low fruit damage rate during storage and best commodity under the same refrigeration condition, the storage tolerance of the fruits is improved by timely harvesting, and the fruits are kept fresh to the greatest extent.

Description

Method for selecting the best harvesting period of non-climacteric fruits after cold storage

Technical Field

The invention relates to the technical field of agricultural product production, and in particular to a method for selecting the optimal harvesting period of non-climacteric fruits for post-harvest cold storage.

Background Art

Fruits grow, mature and are ready to be picked. Fresh fruits continue to breathe after being picked (leaving the tree) until they are fully ripe or reach their best eating period. Fruit quality and storage performance are closely related to harvest time, so timely harvesting is particularly important for different varieties.

The appropriate harvesting maturity of fruits is also closely related to their storage and preservation methods. In the document "On the Preservation and Harvesting Maturity of Horticultural Crop Products" (Zhuang Xuzhi. Southwest Horticulture, 2001, 29(4):16-17), it is disclosed that for citrus fruits for storage, the textbook says: "Harvesting should be slightly earlier than fresh-eating fruits, and should be harvested when they are close to maturity; for storage fruits, most of them are harvested when the peel tissue has fully developed, the color has reached about 80%, and the flesh has not yet completely softened." This only explains the harvesting maturity of fruits in the "current" conventional storage methods, and fails to reflect the requirements of harvesting maturity for various storage methods. Some people believe that "citrus fruits for storage should be harvested when they are 70% to 80% mature, that is, when two-thirds of the peel turns yellow", while others believe that they should be harvested when they are fully mature, such as wide-skinned citrus fruits should be harvested when the peel color turns 60% yellow, and oranges should be harvested when they are fully colored. "The above opinions are inconsistent and even conflicting, which shows that the issue of maturity for fresh-keeping harvesting deserves further exploration. In practical application, Shen Zhaomin and others believe that "different fruit storage methods may result in different harvest maturity. For example, fruits for controlled atmosphere storage should be harvested early, while fruits for refrigerated storage have higher requirements for maturity"; Shao Pufen and others introduced that the Jincheng oranges stored in their silicon window controlled atmosphere storage "should be harvested appropriately early..." Previous studies have mostly believed that the higher the maturity of fruits for refrigerated storage, the better. It is generally believed that the lower the maturity of the fruit, the more sensitive it is to low temperatures and the more likely it is to suffer from chilling damage.

The maturity of non-respiratory climacteric fruits is difficult to define, and there are many influencing factors, which are more complicated. In addition, the harvesting period of the same variety in different production areas is not completely consistent, so the harvesting time is mainly based on experience and is mostly a wide time range. Citrus fruits are typical non-respiratory climacteric fruits. In the past, there have been many studies on early and mid-ripening varieties of citrus. Generally, the color change of the early and mid-ripening peel is positively correlated with the maturity of the fruit, and its maturity can be easily judged by the appearance of the peel color. However, there are not many studies on the harvesting period of late-ripening citrus, and there is even less understanding of its harvesting maturity, especially the specific timely harvesting time has not yet been determined (there is no unified basis or specific standard). The harvesting period of general fruits such as late-ripening citrus fruits is not only different due to varieties, tree age, growth environment, etc., but also related to the purpose and purpose of harvesting. Compared with tree storage, tree hanging storage or immediate picking, since most fruits are not picked when the tree is fully ripe, they more or less need to undergo the process of ripening or turnover storage and transportation.

The maturity of late-ripening citrus is difficult to judge by appearance. For example, the Tarocco blood orange will continue to change color (tending to purple-red) at low temperatures, and the color of the blood orange peel and flesh is not consistent; Powell navel oranges are similar to summer oranges, and the peel turns green; the mixed orange Shiranui completes color change in December of the year, but does not begin to mature until March of the following year, so it is difficult to judge its maturity by the peel color, and the rough peel of Shiranui is not conducive to the measurement of the colorimeter. Further research is needed to estimate the suitability of harvesting by internal indicators of the fruit or non-destructively.

Therefore, it is necessary to study the cold storage specificity of late-ripening citrus fruits after harvest in order to find out their different storage, transportation and harvesting periods.

Summary of the invention

The object of the present invention is to provide a method for selecting the best harvesting period of non-climacteric fruits for post-harvest cold storage in view of the above problems.

In order to achieve its purpose, the present invention adopts the following technical solution:

A method for selecting the best harvesting period of non-climacteric fruits after post-harvest cold storage comprises the following steps: picking the non-climacteric fruits when they grow to maturity on the fruit trees, picking them in at least three phases, with the interval between each phase being 3-4 weeks; storing the fruits in a cold storage corresponding to the fruit variety after picking, detecting the respiration intensity of the fruits during storage, and selecting the phase with the smallest respiration intensity as the best harvesting period for the fruit variety.

Preferably, the non-climacteric fruit is late-ripening citrus.

Furthermore, the late-ripening citrus is blood orange, Nashi orange or navel orange. The harvesting period of blood orange is from December of the flowering year to March of the following year, the harvesting period of Nashi orange is from February to May of the second year after flowering, and the harvesting period of navel orange is from March to May of the following year after flowering. The citrus is harvested in at least three phases within the respective harvesting period, and the interval between each phase is 3-4 weeks. After harvesting, the citrus is stored in a cold storage corresponding to the fruit variety. During storage, the respiration intensity of the fruit is detected, and the phase with the smallest respiration intensity is selected as the best harvesting period for the fruit variety.

In the above technical scheme, the picked fruits are pre-cooled and pre-stored before storage or the respiration intensity is tested at least 1-2 weeks after entering the cold storage. At the same time, the respiration intensity of the fruits picked at different periods is tested, and the period with the lowest respiration intensity is selected as the best harvesting period for this variety of fruit.

The present invention also provides a storage method for non-climacteric fruits, comprising the following steps:

1) Select the best harvesting period for the fruit: select the best harvesting period for the fruit of the variety according to the above method;

2) Pick the fruit of this variety according to the selected optimal harvesting period, and store it in the cold storage corresponding to this variety after harvesting.

The beneficial effects of the present invention are as follows: it overcomes the technical prejudice of the prior art that "the higher the maturity of fruits for refrigeration, the better", and proposes a new method for selecting the best harvesting period for post-harvest refrigeration of non-respiratory climacteric fruits. Fruits harvested at the harvesting period determined by this method have high fruit quality and low storage disease rate under the same refrigeration conditions, and have the best commercial quality. Harvesting at the right time not only improves the storage resistance of the fruits, but also enables the fruits to be kept fresh to the greatest extent.

BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 shows the storage lesions of blood oranges harvested at different times.

Figure 2 shows the results of respiration intensity of blood orange fruits during storage at different harvest times.

Figure 3 shows the storage lesions of the third-stage Shiranui after harvest.

DETAILED DESCRIPTION

The present invention will be further described below in conjunction with embodiments, but the present invention is not limited thereto.

The experimental methods in the following examples are conventional methods unless otherwise specified.

Example 1

1 Materials and methods

1.1 Fruit materials and equipment

Tarocco blood oranges were harvested from the orchard of the Resource Room of the Citrus Research Institute of the Chinese Academy of Agricultural Sciences (trees over 5 years old); Nashi oranges were harvested from the storage research orchard of the Citrus Research Institute of the Chinese Academy of Agricultural Sciences (trees less than 3 years old); Powell navel oranges were produced from the orchard in Fengjie, Chongqing. The harvesting period was about one month apart (the second and third periods of Nashi oranges and Powell navel oranges were about three weeks apart); all were harvested in three phases, and the specific harvesting time is detailed in Table 1. Each variety of fruit was harvested in 3 to 5 boxes per period, with about 80 fruits in each box (depending on the size and quantity of the fruit variety).

Several cold storage rooms with adjustable humidity; several plastic fruit boxes and single fruit packaging bags; colorimeter and refractometer are essential for testing, etc.

1.2 Test plan and sampling and testing

The procedures from fruit picking to storage were standardized according to the relevant standards (Citrus Storage NY/T 1189-2006). The experimental scheme is shown in Table 1.

Table 1 Test table of harvesting period of blood orange, unknown fire orange and navel orange

Each treatment number was replicated at least three times, and each replicate was a box of fruit. Real-time monitoring and regular investigation of fruit storage lesions were conducted, and rotten fruit was removed. Finally, statistics were collected on the rot rate and other disease conditions of each treatment, as well as indicators such as intrinsic quality (GB/T 12947-2008 Fresh Citrus).

1.3

1.3.1 Investigation of fruit storage lesions

The diseased fruit rate mentioned in the present application is the percentage of the infectious fruits visible to the naked eye plus the physiologically diseased fruits to the total number of fruits before storage; similarly, the rot rate and brown spot rate are respectively rot rate (%) = (number of rotten and moldy fruits/total number of fruits) × 100; brown spot rate (%) = (number of fruits with brown spots and dry scars/total number of fruits) × 100.

1.3.2 Determination of respiratory intensity

The respiration test adopts the alkaline absorption CO ₂ method. The same treatment is still repeated three times each time. The number of fruit sampled in each repetition depends on the size of the fruit, about 10. Respiration intensity test time: Each sample is tested at least once a month. Since the respiration of fresh fruit just put into the cold storage is relatively high, it is generally tested after it stabilizes (1 to 2 weeks).

1.3.3 Determination of quality and other internal quality indicators

For fruit quality analysis, at least 10 fruits were sampled for each replicate and three replicates were tested after storage. Soluble solids, sugar, acid, vitamin C and other indicators were tested according to the national standard (Citrus fresh fruit inspection method GB/T 8210-2011) and Chinese patent ZL201310752539.8 (patent name: A direct titration method for reducing sugar to improve titration accuracy). The quality indicators TSS, RS, TA and VC represent soluble solids, reducing sugar, total acid (titratable acid) and vitamin C, respectively. In this paper, the solid-acid ratio (TSS:TA) and the sugar-acid ratio (RS:TA) were calculated by dividing the mean, that is, expressed as TSS/TA and RS/TA, respectively.

In the color difference, L is the brightness value, a ^* - the difference between red and green, b ^* - the difference between yellow and blue, OJ is the comprehensive score of the instrument on the juice; the larger the positive value of a ^* , the deeper the red, the larger the positive value of b ^* , the deeper the yellow, ho is the hue angle, when ho is within 90°, the smaller its value, the more purple-red. The symbol △ represents the change before and after storage, that is, the difference between the corresponding index values (after storage - before storage).

1.4 Statistics

The data in the experimental results charts are presented as the mean ± relative standard deviation of three replicates of each treatment number, except for those listed individually. The data were sorted, analyzed and plotted using Microsoft Excel, and the significance of the differences was analyzed using SPSS software.

2 Results and analysis

2.1 Tarocco Blood Orange

Blood oranges harvested in three periods were stored in the same warehouse (6-8℃/RH 80%) after harvesting. After the latest harvest, all fruits harvested in three periods were transferred to indoor (20-22℃) for a shelf life of half a month. The storage lesion situation of Tarocco blood orange (hereinafter referred to as blood orange) and the shelf investigation statistics are shown in Figure 1. From the statistics of the monthly average morbidity of different harvest periods from the lesion investigation data, it can be seen that the first period of blood oranges is relatively good, not only showing the lowest morbidity of rot, but also the morbidity rate during the shelf period is significantly lower than that of T3 blood orange III.

The fruit quality test data results are shown in Table 2 below.

Table 2 Quality test data of blood orange after storage

Note: a, b, c--significant difference mark (p<0.05)

The reducing sugar content of blood orange in stage I and stage II increased by 1.49% and 0.59% respectively compared with the time of harvest, while that in stage III decreased by 1.29%; the vitamin C content in stages I, II and III decreased by 6.99%, 16.05% and 8.61% respectively compared with the time of harvest, indicating that the quality of the first-stage fruit is relatively well maintained. After the longest period of time (5 months), the fruit samples were tested, which also showed that the solid-acid ratio, sugar-acid ratio and juice yield of stage I were the highest, and the vitamin C content was significantly the highest (see Table 2), indicating that the quality of the first-stage harvest is well maintained.

The results of the respiration test data are shown in Figure 2, which shows that the respiration intensity of the first-stage harvested fruit is low and significantly lower than that of the second stage. This also confirms the results of storage disease, that is, the lower the disease rate, the lower the respiration intensity of the first-stage fruit, and vice versa.

The color difference detection of blood orange juice at the end of storage (May 20) and its comparison with the color difference index at harvest can reflect the color changes of the internal quality of fruits at different harvesting periods (see Table 3).

Table 3 Changes of color difference indexes and related color differences of blood orange juice before and after storage

The data in Table 3 show that the color of blood orange juice after storage in stage I not only has the highest a* value and OJ, but also the smallest hue angle ho, and the most obvious red turn (the largest increase in △a) and tends to purple-red (△ho significantly decreases), and the comprehensive score OJ also increases significantly.

Therefore, blood oranges picked in the first period have the least disease and the lowest respiration rate during storage. The quality and color difference of the fruit after storage reflect that the first period is better. At the same time, the darkening of the juice color may also be due to the fact that low temperature helps the synthesis and transformation of anthocyanins and other substances in the fruit itself.

2.2 Mixed Citrus Unknown Fire

After the fruits of the unknown fire were set, they were picked from February to April of the following year, that is, picked on February 6, March 6, and March 27, and stored in the same warehouse (4-6℃/RH70%). The fruits picked last were stored for at least 3 months (stored until July 7) and their disease status was counted. The data results are shown in Figure 3.

Although the parallelism of the three replicates of brown spotted and rotten fruits in the warehouse investigation was not very good (the difference was not significant), the statistics of their final disease data showed that the total disease incidence and monthly average diseased fruit rate of S1 were significantly the highest. In comparison, the last period S3 was better.

Finally (July 14), the respiratory intensities (mgCO ₂ /(kg·h)) of S1, S2, and S3 were measured to be 14.80±1.53, 12.43±1.20, and 10.45±0.57, respectively. S1 was significantly the highest, which also confirmed the storage lesion results.

The relevant data of the internal quality test after storage of the fruits harvested in different stages are shown in Table 4. In comparison, the color difference index of S1 in the first stage was the worst, and its a, b, and OJ values were significantly the lowest, and S3 was slightly better than S2. In terms of quality analysis, except that S1 had a lower solid content and its reducing sugar was lower than the index data at harvest, the solid content and reducing sugar of S3 and S2 were both higher than that at harvest; and the solid content and sugar index of S3 after harvest and storage were higher. The insignificant difference between it and S2 may be due to the short time interval between the two harvest periods.

Table 4 Data on relevant indicators of juice testing at the end of storage of fruits harvested in different stages of Shiranui

Therefore, from the perspective of storage investigation, quality, color difference, etc., S3, which was picked the latest, is the best, and the respiration intensity of S3 is also the lowest.

2.3 Powell Navel Orange

The pathological changes of the plants were investigated during post-harvest storage at P1, P2 and P3. The pathological changes data after about 100 days of storage are shown in Table 5. The table lists the specific data of three replicates for each harvest period.

Table 5 Pathological changes and respiratory test data of Powell navel oranges at different harvesting periods

The data showed that the rot rate was higher in stage Ⅰ, the brown spot rate was higher in stage Ⅲ, and the total incidence of stage Ⅱ P2 was lower; the diseased fruit rates (%) of stages P1, P2, and P3 were 1.04±1.07, 0.43±0.74, and 1.44±1.60, respectively.

The trends of the respiration intensity of the fruits picked in the three periods over time were basically the same, that is, it was higher when just picked (higher in the early stage), and decreased and stabilized in the later stage, and the respiration intensity of the fruits in each period was affected by the storage temperature in the warehouse. Compared with the three periods, the respiration intensity of P2 in period II was the lowest, while that of P1 in period I was always the highest. After three months of storage (June 11), the respiration intensity of P1 was 15.23±1.04/mg CO ₂ /(kg·h). The respiration intensity test data until the last (July 31) are listed in Table 5, and P1 is still significantly the highest.

Table 6 Quality related indicators of three-stage Powell navel oranges before and after storage

The quality results of fruits harvested in three periods and after storage are shown in Table 6. Although all indicators of P3 in stage III are relatively high, in addition to the influence of sampling factors, it is mainly due to the fact that it was harvested later and the storage period is the shortest. Even so, the sugar, acid, and Vc of P3 in stage II are not significantly different from those of P2 in stage I. However, the quality indicators of P1 in stage I have dropped the most, and its total acid and vitamin C have dropped by 61.8% and 37.85% compared with the time of harvest. The brightness L value of the fruits harvested in different periods has decreased after storage, but the a, b, and OJ values have increased. The change range is shown in Table 7. It can be seen that the brightness of P2 has decreased the least (△L) (1.185), and the increase range of △a, △b and △OJ reflecting red, yellow and comprehensive scores is the highest, so P2 in stage II is the best, and the respiration intensity of P2 is also the lowest. In practice, it is also found that the skin of the fruits picked in stage III has "returned to green".

Table 7 Changes in color difference index of juice of three-stage Powell navel orange before and after storage

In summary, the best harvesting periods for each of them are the first period of Tarocco blood oranges (harvested on December 17 of the current year), the third period of Shiranui oranges (harvested on March 27 of the following year), and the second period of Powell navel oranges (harvested on April 9 of the following year).

The cold storage effect studied in this application is based on the data results of quality detection, respiratory intensity, storage pathology and other indicators before and after cold storage of fruits. It also reflects that there is a great correlation between post-harvest pathology of fruits and respiratory intensity, that is, the higher the respiratory intensity of the same variety under the same environmental conditions, the higher the incidence rate, and the faster the quality declines. Although the harvest period of late-maturing citrus varies depending on the variety, they have similar post-harvest reactions. The method of the present invention can determine the optimal harvest period for different late-maturing citrus varieties. Timely harvesting not only improves the storage resistance of the fruit, but also allows the fruit to be kept fresh to the greatest extent. This idea can be used to analyze and determine the appropriate harvest period for other non-respiratory climacteric fruits.

Claims (2)

1. A method for selecting the optimal harvest time of non-respiratory jump type fruits after being picked and refrigerated is characterized by comprising the following steps: picking the fruits at least in 3 stages after the non-climacteric fruits grow to the mature period on the fruit trees, wherein the picking interval time of each stage is 3-4 weeks, storing the fruits in a refrigerator corresponding to the fruit variety after picking, detecting the respiratory intensity of the fruits during the storage period, detecting the respiratory intensity of the picked fruits at least 1-2 weeks after the picked fruits enter the refrigerator, detecting the respiratory intensity of the picked fruits at different periods, detecting the respiratory intensity once at least every month, and selecting the stage with the minimum respiratory intensity to determine the optimum picking stage of the fruits;

the non-respiratory jump type fruits are late-maturing citrus, talocos, or burning-unaware or powell navel oranges, the harvesting period of the talocos is 12 months to 3 months in the next year after flowering, the harvesting period of the burning-unaware is 2 to 5 months in the next year after flowering, and the harvesting period of the powell navel oranges is 3 to 5 months in the next year after flowering.

2. A method for storing non-climacteric fruit, which is characterized by comprising the following steps:

1) Selecting the optimal harvesting period of the fruits: selecting the optimal harvest time of the variety of fruit according to the method of claim 1;

2) And picking the fruits of the variety according to the selected optimal picking period, and storing the picked fruits in a refrigerator corresponding to the variety for storage.

Images