A peach fruit chilling injury detection and prediction method

Abstract

This invention relates to a method for detecting and predicting chilling injury in peach fruit, comprising the following steps: cutting the fruit pulp into sections and randomly grouping them; subjecting each group of pulp to high-pressure treatment at different pressures; adding a dissociation solution to the pulp in different groups to dissociate membrane-bound polyphenol oxidases in the pulp; and measuring the enzyme activities (B1, B2, B3, B4…B) of the membrane-bound polyphenol oxidases in the pulp treated at different pressures. n The dissociated membrane-bound polyphenol oxidase was activated by adding an activator, and then the enzyme activity C was measured. The activation rates under different high-pressure treatment conditions were B1 / C, B2 / C, B3 / C, B4 / C…B. n / C; Based on the activation rate under high-pressure treatment at different pressures, the pressure value P corresponding to the activation rate discrimination standard value R is calculated. Then, based on the prediction equation between the pressure value P and the storable time, the storable time is calculated. This method can quickly and early detect chilling injury and can also predict the storable time of unknown peach fruits.

Description

Technical Field

[0001] This invention relates to the field of post-harvest testing and prediction technology for agricultural products, and in particular to a method for detecting and predicting chilling injury in peach fruits. Background Technology

[0002] Peaches are a typical climacteric fruit, exhibiting vigorous respiration after harvest and rapid ripening and softening, making them highly susceptible to decay and spoilage. Their shelf life at room temperature is only 2-3 days. Low temperatures are an effective measure to delay ripening and softening, extending the storage period. However, peaches are prone to chilling injury at low temperatures, with symptoms including browning of the flesh, fruit rotting, failure to soften and ripen during shelf life (lignification), diminished flavor, and reduced juice yield. Studies have shown that 2.2–7.6℃ is the most sensitive temperature range for chilling injury in peaches, with many studies indicating that peaches are most susceptible to chilling injury at 5℃. The optimal storage temperature is 0℃ or ice-temperature storage. Generally, the lower the storage temperature of chill-sensitive fruits and vegetables, the more severe the chilling injury. For example, bananas have a chilling injury critical temperature of 11℃, with an optimal storage temperature of 13-15℃. Controlling the storage temperature can prevent chilling injury. However, the ideal storage temperature for peaches is 0℃ or even below freezing, which is lower than the critical chilling injury temperature of 7.6℃. This effectively places the fruit at chilling injury temperatures, making it impossible to prevent chilling injury through temperature control alone. Short-term storage will not cause chilling injury, but once the storage time exceeds a certain limit, it will occur. Furthermore, because the symptoms of chilling injury in peaches are delayed, even if chilling injury has already occurred at low temperatures, it often only becomes apparent during the shelf life after the fruit has left the warehouse. Chilling injury is a physiological disorder, characterized by its sudden onset and widespread nature; once it occurs, the entire batch and warehouse are affected, causing significant economic losses. Due to the lack of effective methods for detecting and predicting chilling injury, the chilling time for freshly picked peaches has long been judged based on experience. Even for unknown samples whose refrigeration history is uncertain, it is difficult to determine the refrigeration period based on experience alone.

[0003] Traditional methods for detecting chilling injury in peaches involve storing the peaches on the shelf for 2-3 days, then cutting them open and observing their internal structure. Symptoms such as browning, softness, and hardening are used to determine the presence and severity of chilling injury, or indicators like juice yield or browning degree are used for evaluation. However, Chinese invention patents CN201310409795.7 ("A Method for Detecting Early Chilling Injury in Peach Fruits Using Hyperspectral Image") and CN201610339086.X ("A Non-destructive Detection Method for Chilling Injury in Peach Fruits") detect changes in the internal and external color of chilled peaches to determine the occurrence and severity of chilling injury, preventing chilled fruit from entering the market and avoiding further losses. However, there are still some shortcomings: (1) Since chilling injury is irreversible, even if chilling injury can be detected, even if it is early chilling injury, the resulting losses cannot be avoided; (2) For normal fruit that has not been chilled, it is still unknown how long it can be stored; (3) For peaches that have been purchased, the storage temperature and time before purchase are often uncertain, and there is a great risk of chilling injury if they are stored at low temperatures after purchase. Therefore, there is an urgent need for a detection and prediction method that can be carried out before chilling injury occurs.

[0004] Numerous studies have shown that the formation of chilling injury symptoms is closely related to the increase in the activity of key chilling injury enzymes, such as polyphenol oxidase (PPO), pectin methyl esterase (PME), and peroxidase (POD), which are key enzymes in the formation of chilling injury symptoms such as browning, fluffing, and lignification in peach fruits. Key chilling injury enzymes are divided into two forms: free and membrane-bound. Among them, membrane-bound key chilling injury enzymes have the following two major characteristics: (1) they are inactive or have weak activity, that is, they have potential enzyme activity; (2) they can be activated under certain conditions and exhibit high catalytic activity. Long-term low temperature leading to membrane lipid phase transition is one of the activation conditions. The affinity between the substrate and the enzyme will be significantly enhanced, and the increase in enzyme activity will disrupt the metabolic balance, resulting in chilling injury. This is a novel metabolic pathway induced and activated by a purely physical variable, which is different from the free radical aging and gene regulation theory and is independent of other abiotic stress and aging mechanisms. Experimental studies have found that, in addition to temperature, pressure is another purely physical variable that can activate potential key chilling injury enzymes and has an equivalent enzyme activation effect. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide a method for detecting and predicting chilling injury in peaches, which can detect whether peaches have suffered chilling injury and the shelf life of peaches.

[0006] The technical solution adopted by this invention to solve the above-mentioned technical problem is: a method for detecting and predicting chilling injury in peach fruit, characterized by comprising the following steps:

[0007] (1) Peach fruit pretreatment

[0008] Peel and pit the peaches to be tested to obtain the pulp. Cut the pulp into pieces and randomly group them. Each group of pulp is subjected to high pressure treatment at different pressures for the same time.

[0009] (2) Obtain membrane-bound polyphenol oxidase from fruit pulp and determine its activity.

[0010] Dissociation solution was added to different groups of fruit pulp to dissociate membrane-bound polyphenol oxidase. The enzyme activity A of membrane-bound polyphenol oxidase in untreated pulp and the enzyme activities B1, B2, B3, B4…B4 in pulp treated with different pressures were then measured. n ;

[0011] (3) Determine the activity of membrane-bound polyphenol oxidase after activation and calculate the activation rate.

[0012] An activator was added to the dissociated membrane-bound polyphenol oxidase to activate it. The average enzyme activity (C) after activation was then measured for each group. The activation rate under no high-pressure treatment was A / C; the activation rates under different high-pressure treatments were B1 / C, B2 / C, B3 / C, B4 / C…B n / C, activation rates B1 / C, B2 / C, B3 / C, B4 / C…B n / C are denoted as R1, R2, R3, R4...R n ;

[0013] (4) Determine if cold damage has occurred

[0014] By comparing the activation rate A / C and the activation rate discrimination standard value R, it can be determined whether cold damage has occurred.

[0015] (5) Predicting storage time

[0016] The activation rate discrimination standard value R is calculated based on the activation rate under high pressure treatment conditions at different pressures, and the pressure value P corresponding to it is then calculated based on the prediction equation between the pressure value P and the storage time T.

[0017] Furthermore, the high pressure range used in step (1) is 10–500 MPa, and the treatment time is 5 min. When the pressure value P corresponding to the activation rate discrimination standard value R is within the range of 30–50 MPa, the peach fruit has not yet suffered chilling injury, but if it continues to be stored in cold storage, chilling injury will soon occur; it is necessary to remove it from the storage in time or raise the storage temperature to a non-chilling injury temperature, such as 8–10℃, to avoid further development and occurrence of chilling injury.

[0018] Further, the operation of dissociating membrane-bound polyphenol oxidase in step (2) is as follows: Buffer solution is added to each group of fruit pulp obtained in step (1), and homogenization is performed to obtain a first homogenate. The first homogenate is centrifuged, the supernatant is discarded, and the filter residue is collected. Dissociation solution is added to the filter residue, and homogenization is performed again to obtain a second homogenate. The second homogenate is centrifuged, and the supernatant is collected to obtain peach fruit membrane-bound polyphenol oxidase solution. The enzyme activity A and enzyme activities B1, B2, B3, B4…B of the membrane-bound polyphenol oxidase solution are measured. n .

[0019] Further, the dissociation solution mentioned in step (2) is Triton X-100 with a mass concentration of 0.1 to 1.0%; the activator mentioned in step (3) is sodium dodecyl sulfate with a mass concentration of 0.05 to 0.2%.

[0020] Furthermore, the activation rate discrimination standard value R mentioned in step (4) is 10-30%. If the activation rate A / C is greater than the activation rate discrimination standard value R, then chilling injury has occurred; if the activation rate A / C is less than the activation rate discrimination standard value R, then chilling injury has not occurred.

[0021] Furthermore, the activation rate discrimination criterion value in step (4) is preferably 25%.

[0022] Furthermore, in step (5), the two activation rates R around the activation rate standard value R are determined based on the activation rate. n and R n+1 The corresponding pressure values ​​P n and P n+1 The pressure value P when the activation rate is R is calculated, and the theoretical storage period T is calculated based on the pressure value P.

[0023] Furthermore, the pressure value P at an activation rate of R is derived from the following linear equation: P = P n +(25-R n (P) n+1 -P n ) / (R n+1 -R n ).

[0024] Furthermore, the predictive equation between the theoretical storage period T and the pressure value P at the activation rate R is as follows: T = 0.074P, R 2 =0.954.

[0025] Furthermore, the high-pressure treatment of the fruit pulp in step (1) can also be: using the same high pressure for different treatment times; the high pressure of this treatment method is a fixed pressure within the range of 10-500 MPa, and the treatment time range is 1-30 min. For example, using the same 200 MPa high pressure for 1-30 min. If the same pressure is used for different treatment times, then another chilling injury prediction equation can be established between the final theoretical storage period T and the treatment time t when the activation rate is R: T = 1.563t; when the time corresponding to the activation rate discrimination standard value R is within the range of 1-3 min, the peach fruit has not yet suffered chilling injury, but if it continues to be refrigerated, chilling injury will soon occur; it is necessary to remove it from storage in time or raise the storage temperature to a non-chilling injury temperature, such as 8-10℃, to avoid further development and occurrence of chilling injury.

[0026] Compared with the prior art, the advantages of the present invention are as follows:

[0027] (1) The relationship between the activation rate of membrane-bound polyphenol oxidase and the standard value R of activation rate was used to determine whether peach fruit was chilled. Compared with the results of traditional methods, the consistency reached 94.4% and the accuracy of judgment was high.

[0028] (2) Earlier detection time: The pulp of the peach fruit to be tested was treated with dissociation solution and activator to obtain the enzyme activity of membrane-bound polyphenol oxidase before and after activation. Based on the ratio of enzyme activity before and after activation, i.e. activation rate, it can quickly identify whether chilling injury has occurred. Compared with the traditional method of placing it for three days before judgment, it can distinguish chilled fruit from normal fruit earlier.

[0029] (3) High pressure is used to activate the potential enzyme activity of membrane-bound polyphenol oxidase. Different pressures correspond to different activation rates. When the activation rate reaches the activation rate discrimination standard value R, there is a linear relationship between the high pressure value P and the storage time T = 0.074P.

[0030] (4) Predictability: For unknown peach fruits, only different high-pressure treatments for the same time are used to obtain the high-pressure value P corresponding to the activation rate discrimination standard value R. Then, the storage time T can be calculated through the pressure value P. This provides a method to predict the storage time before chilling injury occurs. This method is simple and efficient.

[0031] (5) Chilling injury can be avoided: For normal fruit that is predicted to suffer chilling injury, low-temperature storage, sales or warming to non-chilling injury temperature can be stopped in time, which can completely avoid chilling injury and reduce economic losses. Detailed Implementation

[0032] The present invention will be further described in detail below with reference to the embodiments.

[0033] Taking the "Lakeview Honey Peach" as an example, high pressure was used to activate latent membrane-bound polyphenol oxidase to detect and identify browning chilling injury in peach fruits, and to predict the timing of browning chilling injury. All high-pressure equipment was a CQC2L-600 ultra-high pressure system manufactured by Beijing Suyuan Zhongtian Co., Ltd.

[0034] Example 1: Effect of storage time on the activation rate of membrane-bound polyphenol oxidase

[0035] Freshly picked peaches were selected, removing any mechanically damaged, rotten, or moldy fruits, and choosing those that were uniform in size and about 80% ripe. The peaches were stored at 1±1℃ for 42 days, with samples taken every 7 days to determine the activation rate. Simultaneously, every 7 days, peaches were removed from storage and left at room temperature for 3 days. The peaches were then cut open to observe the internal browning, using traditional methods to determine the occurrence of chilling injury.

[0036] The activation rate of membrane-bound polyphenol oxidase in peach fruit was determined according to the following steps:

[0037] (1) Sample preparation: Peel and pit the peaches, cut the pulp into two groups;

[0038] (2) Extraction and separation of membrane-bound polyphenol oxidase: Add the pH 5.5 acetate-sodium acetate buffer to the pulp, then homogenize and break the pulp to obtain the first homogenate. After centrifugation of the first homogenate, discard the supernatant and collect the filter residue. Add 0.1% Triton X-100 to the filter residue and homogenize and break the filter residue to obtain the second homogenate. After centrifugation of the second homogenate, collect the supernatant, which is the membrane-bound polyphenol oxidase solution. Measure the enzyme activity A of the membrane-bound polyphenol oxidase at this time.

[0039] (3) Activator treatment: Sodium dodecyl sulfate (SDS) was added to the membrane-bound polyphenol oxidase solution. Sodium dodecyl sulfate was used as an activator to activate the membrane-bound polyphenol oxidase. The mass concentration of sodium dodecyl sulfate was 0.05% and the activation time was 20 min.

[0040] (4) Determine the activity C of bound polyphenol oxidase after treatment with activator, and calculate the activation rate value A / C.

[0041] The method for determining the activity of membrane-bound polyphenol oxidase was based on the "Guide to Postharvest Physiological and Biochemical Experiments of Fruits and Vegetables" published by Cao Jiankang et al., which specifically used catechol as a substrate and measured the change in absorbance at a wavelength of 420 nm.

[0042] Example 2: Effect of storage time on the activation rate of membrane-bound polyphenol oxidase

[0043] Freshly picked peaches were selected, removing any mechanically damaged, rotten, or moldy fruits, and choosing those that were uniform in size and about 80% ripe. The peaches were stored at 1±1℃ for 42 days, with samples taken every 7 days to determine the activation rate. Simultaneously, every 7 days, peaches were removed from storage and left at room temperature for 3 days. The peaches were then cut open to observe the internal browning, using traditional methods to determine the occurrence of chilling injury.

[0044] The activation rate of membrane-bound polyphenol oxidase in peach fruit was determined according to the following steps:

[0045] (1) Sample preparation: Peel and pit the peaches, cut the pulp into two groups;

[0046] (2) Extraction and separation of membrane-bound polyphenol oxidase: Add the pH 5.5 acetate-sodium acetate buffer to the pulp, then homogenize and break the pulp to obtain the first homogenate. After centrifugation of the first homogenate, discard the supernatant and collect the filter residue. Add 1.0% Triton X-100 to the filter residue and homogenize and break the filter residue to obtain the second homogenate. After centrifugation of the second homogenate, collect the supernatant, which is the membrane-bound polyphenol oxidase solution. Measure the enzyme activity A of the membrane-bound polyphenol oxidase at this time.

[0047] (3) Activator treatment: Sodium dodecyl sulfate (SDS) was added to the membrane-bound polyphenol oxidase solution. Sodium dodecyl sulfate was used as an activator to activate the membrane-bound polyphenol oxidase. The mass concentration of sodium dodecyl sulfate was 0.2% and the activation time was 40 min.

[0048] (4) Determine the activity C of bound polyphenol oxidase after treatment with activator, and calculate the activation rate value A / C.

[0049] The method for determining the activity of membrane-bound polyphenol oxidase was based on the "Guide to Postharvest Physiological and Biochemical Experiments of Fruits and Vegetables" published by Cao Jiankang et al., which specifically used catechol as a substrate and measured the change in absorbance at a wavelength of 420 nm.

[0050] Example 3: Effect of storage time on the activation rate of membrane-bound polyphenol oxidase

[0051] Freshly picked peaches were selected, removing any mechanically damaged, rotten, or moldy fruits, and choosing those that were uniform in size and about 80% ripe. The peaches were stored at 1±1℃ for 42 days, with samples taken every 7 days to determine the activation rate. Simultaneously, every 7 days, peaches were removed from storage and left at room temperature for 3 days. The peaches were then cut open to observe the internal browning, using traditional methods to determine the occurrence of chilling injury.

[0052] The activation rate of membrane-bound polyphenol oxidase in peach fruit was determined according to the following steps:

[0053] (1) Sample preparation: Peel and pit the peaches, cut the pulp into two groups;

[0054] (2) Extraction and separation of membrane-bound polyphenol oxidase: Add the pH 5.5 acetate-sodium acetate buffer to the pulp, then homogenize and break the pulp to obtain the first homogenate. After centrifugation of the first homogenate, discard the supernatant and collect the filter residue. Add 0.5% Triton X-100 to the filter residue and homogenize and break the filter residue to obtain the second homogenate. After centrifugation of the second homogenate, collect the supernatant, which is the membrane-bound polyphenol oxidase solution. Measure the enzyme activity A of the membrane-bound polyphenol oxidase at this time.

[0055] (3) Activator treatment: Sodium dodecyl sulfate (SDS) was added to the membrane-bound polyphenol oxidase solution. Sodium dodecyl sulfate was used as an activator to activate the membrane-bound polyphenol oxidase. The mass concentration of sodium dodecyl sulfate was 0.1% and the activation time was 30 min.

[0056] (4) Determine the activity C of bound polyphenol oxidase after treatment with activator, and calculate the activation rate value A / C.

[0057] The method for determining the activity of membrane-bound polyphenol oxidase was based on the "Guide to Postharvest Physiological and Biochemical Experiments of Fruits and Vegetables" published by Cao Jiankang et al., which specifically used catechol as a substrate and measured the change in absorbance at a wavelength of 420 nm.

[0058] Table 1. Effects of storage time on browning rate and activation rate of membrane-bound polyphenol oxidase in peach fruits.

[0059] Storage time 0d 7d 14d 21d 28d 35d 42d Browning rate (%) <![CDATA[0 a ]]> <![CDATA[0 a ]]> <![CDATA[0 a ]]> <![CDATA[0 a ]]> <![CDATA[4.2±1.2 b ]]> <![CDATA[78.3±4.1 c ]]> <![CDATA[92.6±5.5 d ]]> Activation rate (%) <![CDATA[6.2±0.8 a ]]> <![CDATA[6.3±0.6 a ]]> <![CDATA[6.1±1.3 a ]]> <![CDATA[6.5±1.4 a ]]> <![CDATA[15.3±1 b ]]> <![CDATA[35.2±2.2 c ]]> <![CDATA[63.4±2.1 d ]]>

[0060] The experimental results are shown in Table 1. Browning occurred relatively concentrated between 28 and 35 days. No chilling injury occurred between 0 and 21 days, but once the storage time exceeded 28 days, chilling injury symptoms became widespread, with the browning rate reaching as high as 78% by 35 days. The activation rate of membrane-bound polyphenol oxidase (MPO) showed a highly consistent trend with the browning rate. Therefore, the MPO activation rate can be used to determine whether chilling injury has occurred; a value between 15.3% and 35.2% represents the threshold for chilling injury. Based on experiments with individual peaches, the final determination of the activation rate for browning in peaches was 25.0%, and the average time for browning was 31 days. MPO activity can also indicate chilling injury to some extent. The activation rate is the ratio of the activity of MPO before and after activation; therefore, compared to MPO activity, the activation rate can eliminate the influence of pH, substrate concentration, and ambient temperature.

[0061] Example 4: Determining the pressure required for peaches stored for different times to reach the activation rate discrimination standard value.

[0062] Freshly picked peaches were selected, and those with mechanical damage, rot, or mold were removed. Peaches of uniform size and about 80% ripeness were chosen. The peaches were then stored at 1±1℃ for 42 days, and samples were taken every 7 days to determine the pressure required to reach the activation rate standard value.

[0063] The pressure required for the activation rate of membrane-bound polyphenol oxidase in peach fruit to reach the activation rate discrimination standard value was determined according to the following steps:

[0064] (1) Sample preparation: Peel and pit the peaches, cut the pulp into 6 groups;

[0065] (2) High pressure treatment: each group of fruit pulp was treated with high pressure of 10, 100, 200, 300, 400 and 500 MPa for 5 minutes, with one pressure value corresponding to each group of fruit pulp;

[0066] (3) Extraction and separation of membrane-bound polyphenol oxidase: A pH 5.5 acetate-sodium acetate buffer solution was added to each group of fruit pulp. The pulp was then homogenized to obtain a first homogenate. After centrifugation, the supernatant was discarded, and the filter residue was collected. Triton X-100 (0.5% by mass) was added to each group of filter residue, and the residue was homogenized to obtain a second homogenate. After centrifugation, the supernatant of each group was collected, and the enzyme activities of membrane-bound polyphenol oxidase B1, B2, B3, B4…B in the supernatant were measured. n ;

[0067] (4) Activator treatment: Sodium dodecyl sulfate (SDS) was added to the supernatant of each group. Sodium dodecyl sulfate was used as an activator to activate membrane-bound polyphenol oxidase. The mass concentration of sodium dodecyl sulfate could be selected as 0.1%, and the activation time was 30 min.

[0068] (5) Determine the average enzyme activity C of bound polyphenol oxidase in each group after activator treatment, and calculate the activation rate values ​​B1 / C, B2 / C, B3 / C, B4 / C…B n / C, activation rates B1 / C, B2 / C, B3 / C, B4 / C…B n / C are denoted as R1, R2, R3, R4...R n ;

[0069] (6) Calculation of the pressure P required to reach the activation rate criterion value R: Take the activation rates R1, R2, R3, R4...R after high-pressure treatment respectively. n The two processing pressure values ​​P, one small and one large, are closest to 25%. n and P n+1 and the corresponding two activation rate values ​​R n and R n+1 The required pressure value P is calculated using the following linear equation: P = P n +(25-Rn (P) n+1 -P n ) / (R n+1 -R n ).

[0070] If we assume that the activation rate is 21% after treatment at 300MPa for 5 minutes and 33% after treatment at 400MPa for 5 minutes, then according to the formula, the treatment pressure value P that reaches the activation rate discrimination standard value of 25% is P = 300 + (25-21)(400-300) / (33-21) = 333MPa.

[0071] Table 2. Pressure required for membrane-bound polyphenol oxidase to reach the chilling injury threshold after different storage times.

[0072]

[0073] The experimental results are shown in Table 2. A linear regression curve can also be plotted between the storage time T and the required pressure P to obtain: T = 0.074P, R 2 =0.954. This equation is the chilling injury prediction equation. Similarly, with a fixed pressure method, such as using 200MPa high pressure to treat the fruit pulp for 1 to 30 minutes, the high pressure treatment time t required to reach the discrimination standard value R can be measured, and another chilling injury prediction equation T = 1.563t can be established based on this.

[0074] Example 5: Verifying the accuracy of using the activation rate of membrane-bound polyphenol oxidase to determine whether peach fruit has suffered chilling injury.

[0075] Six freshly picked peaches, six peaches refrigerated for 28 days, and six peaches refrigerated for 35 days, for a total of 18 peaches, were mixed together. The peaches were numbered 1-18 and cut in half. One half was used to detect the activation rate of membrane-bound polyphenol oxidase, using the same method as in Example 3. The cut surface of the other half was treated with 1% lactosylnatamycin for mold prevention and left at room temperature for 3 days. The half was then cut open and the browning was observed.

[0076] Table 3. Comparison of chilling injury in peach fruit determined by activation rate method and traditional method.

[0077]

[0078]

[0079] Table 3 shows the results of the activation rate method and the traditional method for determining chilling injury in peaches. The results from both methods were largely consistent, with 17 out of 18 peaches showing the same result, a consistency rate of 94.4%. Only peach number 8, with an activation rate of 18.5%, was classified as normal using the activation rate method but as chilling injured using the traditional method. This misjudgment of chilling injury may be related to differences in maturity between the two halves of the peach; it may also be due to human error in the traditional method; and further lowering of the chilling injury threshold may be necessary.

[0080] Example 6: Predicting the shelf life of peaches by using the pressure required for the fruit to reach the chilling injury threshold.

[0081] Five batches of peaches were purchased from wholesale markets and fruit supermarkets. The pressure required to reach the chilling injury threshold was determined for each batch of peaches according to the method in Example 4, and the shelf life of the peaches was calculated using the formula T = 0.074P. Simultaneously, the five batches of peaches were stored at 1±1℃, with samples taken every 7 days, for a maximum storage period of 42 days. After being left at room temperature for 3 days, the samples were cut open and their browning was observed, expressed as the browning rate.

[0082] Table 4. Experimental results of predicted and actual storage time of peach fruit chilling injury.

[0083]

[0084] The experimental results are shown in Table 4. Batch 1, 4, and 5, according to the predicted equation, have a relatively long storage time of 28–31 days, close to the 31-day storage time of freshly picked peaches. This indicates that these three batches of peaches were not subjected to low-temperature storage, or only underwent short-term low-temperature transit. Actual storage experiments showed that chilling injury began to occur in the peaches after 28 days. Batch 2 and 3 require lower pressure to activate bound polyphenol oxidase, and according to the predicted equation, they can be stored for another 8.9–14.8 days. Actual storage experiments showed that chilling injury began to occur in the peaches after 7 days.

[0085] Whether or not peaches are stored at low temperatures before purchase, and the duration of such storage, significantly impacts their shelf life. If two or three batches of peaches are purchased and stored as fresh fruit for 21 days, severe chilling injury will occur, resulting in substantial losses. Experimental results show that the predicted chilling injury time coincides with the actual occurrence of chilling injury. This method can be used to predict chilling injury in peaches for which the pre-purchase storage temperature and time are uncertain, thus guiding low-temperature storage.

[0086] The specified threshold is a pressure of 30–50 MPa. At this pressure, the peaches have not yet suffered chilling injury, but continued refrigeration will quickly lead to it. Timely removal from storage or raising the storage temperature to a non-chilling injury level, such as 8–10°C, can prevent further development and occurrence of chilling injury.

Claims

1. A method for detecting and predicting chilling injury in peach fruits, characterized in that, Includes the following steps: (1) Pretreatment of peach fruit Peel and pit the peaches to be tested to obtain the pulp. Cut the pulp into pieces and randomly group them. Each group of pulp is subjected to high pressure treatment at different pressures for the same time. (2) Obtain membrane-bound polyphenol oxidase from fruit pulp and determine its activity. Dissociation solution was added to different groups of fruit pulp to dissociate membrane-bound polyphenol oxidase. The enzyme activity A of membrane-bound polyphenol oxidase in untreated pulp and the enzyme activities B1, B2, B3, B4…B4 in pulp treated with different pressures were then measured. n ; (3) Determine the activity of membrane-bound polyphenol oxidase after activation and calculate the activation rate. An activator was added to the dissociated membrane-bound polyphenol oxidase to activate it. The average enzyme activity (C) after activation was then measured for each group. The activation rate under no high-pressure treatment was A / C; the activation rates under different high-pressure treatments were B1 / C, B2 / C, B3 / C, B4 / C…B n / C, activation rates B1 / C, B2 / C, B3 / C, B4 / C…B n / C are denoted as R1, R2, R3, R4...R n ; (4) Determine if cold damage has occurred The activation rate A / C and the activation rate discrimination standard value R are compared to determine whether chilling injury has occurred. The activation rate discrimination standard value R is 10~30%. If the activation rate A / C is greater than the activation rate discrimination standard value R, chilling injury has occurred; if the activation rate A / C is less than the activation rate discrimination standard value R, chilling injury has not occurred. (5) Predicting storage time The activation rate discrimination standard value R is calculated based on the activation rate under high-pressure treatment conditions at different pressures, corresponding to the pressure value P. Then, the storage time is calculated based on the prediction equation between the pressure value P and the storage time T. The two activation rates R around the activation rate discrimination standard value R are then considered. n and R n+1 The corresponding pressure values ​​P n and P n+1 The pressure value P at an activation rate of R is calculated and derived from the following linear equation: P = P n +(25- R n (P) n+1 - P n ) / (R n+1 - R n The theoretical storage period T is calculated based on the pressure value P. The predictive equation between the theoretical storage period T and the pressure value P at the activation rate R is as follows: T = 0.074P, R 2 =0.

954.

2. The method for detecting and predicting chilling injury in peach fruit according to claim 1, characterized in that: The high pressure range used in step (1) is 10~500MPa, and the processing time is 5min.

3. The method for detecting and predicting chilling injury in peach fruit according to claim 1, characterized in that: The operation of dissociating membrane-bound polyphenol oxidase in step (2) is as follows: Buffer solution is added to each group of fruit pulp obtained in step (1), and homogenization is performed to obtain the first homogenate. The first homogenate is centrifuged, the supernatant is discarded, and the filter residue is collected. Dissociation solution is added to the filter residue, and homogenization is performed again to obtain the second homogenate. The second homogenate is centrifuged, and the supernatant is collected to obtain the peach fruit membrane-bound polyphenol oxidase solution. The enzyme activity A and enzyme activities B1, B2, B3, B4…B of the membrane-bound polyphenol oxidase solution are measured. n .

4. The method for detecting and predicting chilling injury in peach fruit according to claim 1, characterized in that: The dissociation solution mentioned in step (2) is Triton X-100 with a mass concentration of 0.1~1.0%; the activator mentioned in step (3) is sodium dodecyl sulfate with a mass concentration of 0.05~0.2%.

5. The method for detecting and predicting chilling injury in peach fruit according to claim 1, characterized in that: The activation rate criterion value mentioned in step (4) is 25%.

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