Fresh-keeping method for prolonging storage period of cistanche salsa after picking and reducing loss of nutritional ingredients

Abstract

The invention provides a fresh-keeping method for prolonging the storage period of picked cistanche and reducing the loss of nutritional ingredients, which is characterized by comprising the following steps: pre-cooling the picked fresh cistanche, soaking in hot water in combination with short-wave ultraviolet irradiation, and storing in a low-temperature environment. The method has the beneficial effects that the fresh cistanche is taken as a raw material, and the aim of prolonging the storage period of the picked cistanche is fulfilled through combined application of heat treatment, short-wave ultraviolet irradiation and low-temperature storage after the fresh cistanche is selected and pre-cooled. The method is low in price, simple and convenient to operate, free of residues, green, safe and environment-friendly, the storage period of the fresh cistanche deserticola can be prolonged to 80 days, and the stability of the overall quality and flavor in the low-temperature storage process of the fresh cistanche deserticola can be well kept.

Description

Technical Field

[0001] The present application relates to the technical field of food preservation, and in particular to a preservation method for extending the storage period of Cistanche deserticola after harvest and reducing the loss of nutrients. Background Art

[0002] Cistanche deserticola YC Ma is a root parasitic herb belonging to the genus Cistanche in the family Orobanchaceae. Its medicinal part is the fleshy stem with scaly leaves. It is a traditional precious tonic medicinal material in my country and is known as the "desert ginseng". Cistanche is mainly distributed in the deserts and deserts in northwest my country. It has now developed into a major Chinese medicine variety with a planting area of ​​1.26 million mu, an annual output of 6,000 tons, and a related industry output value of more than 20 billion yuan. With Cistanche (desert) being officially included in the catalog of medicinal and edible substances in 2023, its market demand is growing. The harvesting and processing of Cistanche are highly seasonal, but its fresh fleshy stems have the characteristics of high water content, high sugar content, easy browning and mildew after harvesting, and are not suitable for storage after harvesting, resulting in serious economic losses after harvesting. Therefore, in order to prolong the postharvest storage period, it is particularly important to develop new Cistanche preservation technologies and try the synergistic effects of various modern preservation technologies to improve the preservation effect and maintain stable storage quality.

[0003] In recent years, as consumers' acceptance of chemical residues in food decreases, green, safe and environmentally friendly physical preservation technologies have received more and more attention and have been widely used in the field of postharvest storage research of agricultural products. Fresh Cistanche deserticola is prone to browning and mildew, which are two important reasons for its postharvest quality reduction. Heat treatment and short-wave ultraviolet irradiation treatment have shown good preservation effects in reducing postharvest browning and decay of agricultural products.

[0004] Mild heat treatment (38-60℃) mainly has the functions of heat inactivation of enzymes, reduction of chilling damage and delay of ripening process, killing key insect contamination and controlling fungal decay. Short-term hot water immersion treatment has little adverse effect on the quality characteristics of the sample itself, and can also effectively reduce post-harvest decay and improve its overall appearance. It is easy to use and low-cost, and is widely used in post-harvest research of agricultural products.

[0005] Short-wave ultraviolet rays (200-280 nm) can penetrate the cell membrane of microorganisms and inactivate their genetic material, which in turn causes the microorganisms to lose their ability to reproduce or die. In addition to inhibiting epidermal microorganisms, short-wave ultraviolet radiation can enhance their resistance by regulating the physiological processes of plant organs and delay their post-harvest maturation or aging. At the same time, it is a non-thermal physical method that is inexpensive, safe and effective, easy to operate, and does not leave any residue on the treated samples. It also has the advantages of being eco-friendly and sustainable.

[0006] Temperature is an important factor affecting food quality. Low-temperature storage can reduce the rate of chemical reactions and the activity of enzymes and microorganisms. It is the most common and effective way to extend the shelf life of fresh herbs after harvest and maintain their quality.

[0007] However, there are no domestic or foreign research reports on the combined application of heat treatment, short-wave ultraviolet irradiation and low-temperature storage in the post-harvest preservation of Cistanche deserticola. Summary of the invention

[0008] In view of the above-mentioned technical limitations, the present application proposes a preservation method for extending the post-harvest storage period of Cistanche deserticola and reducing the loss of nutrients; the purpose is to solve the problem of applying heat treatment, short-wave ultraviolet irradiation and low-temperature storage to the post-harvest preservation of Cistanche deserticola and extending the storage period of Cistanche deserticola; the method is low-cost, easy to operate, residue-free, and has the characteristics of being green, safe and environmentally friendly, and can extend the storage period of fresh Cistanche deserticola to 80 days, and better maintain the stability of its overall quality and flavor during low-temperature storage.

[0009] To achieve the above objectives, this application adopts the following technical solutions:

[0010] The invention of the present application is to provide a preservation method for extending the storage period of Cistanche deserticola after harvest and reducing the loss of nutrients. The method comprises precooling the fresh Cistanche deserticola after harvest, soaking it in hot water and irradiating it with short-wave ultraviolet rays, and then storing it in a low-temperature environment.

[0011] Optionally, the above-mentioned preservation method for extending the storage period of Cistanche deserticola after harvest and reducing the loss of nutrients comprises the following steps:

[0012] S1. Material pretreatment: Select fresh fleshy stems of Cistanche deserticola as the material and precool them;

[0013] S2. Heat treatment: completely immerse the Cistanche deserticola in a water bath at a preset temperature and allow it to air dry naturally after treatment;

[0014] S3. Short-wave ultraviolet irradiation: expose Cistanche deserticola to ultraviolet sterilization lamp;

[0015] S4. Packaging and storage: Wrap the processed Cistanche deserticola tightly with plastic wrap and store it at a temperature of 4°C and a relative humidity of 65-75%.

[0016] Optionally, in the above-mentioned preservation method for extending the storage period of Cistanche deserticola after harvest and reducing the loss of nutrients, in step S1, the selected fresh Cistanche deserticola is Cistanche deserticola harvested in spring or autumn without obvious mechanical damage and pests and diseases, and its fleshy stems are taken.

[0017] Optionally, in the above-mentioned preservation method for extending the post-harvest storage period of Cistanche deserticola and reducing the loss of nutrients, in step S1, the precooling treatment conditions are: temperature 4° C., relative humidity 65-75%, and precooling time 24 hours.

[0018] Optionally, in the above-mentioned preservation method for extending the post-harvest storage period of Cistanche deserticola and reducing the loss of nutrients, in step S2, the preset temperature of the heat treatment water bath is 40-60° C., and the treatment time is 30 min.

[0019] Optionally, in the above-mentioned preservation method for extending the storage period of Cistanche deserticola after harvest and reducing the loss of nutrients, in the short-wave ultraviolet irradiation treatment in step S3, the ultraviolet sterilization lamp is an ozone-free double-ended ultraviolet sterilization lamp with a tube diameter of 19 mm, a power of 30 W and a central wavelength of 253.7 nm; the treatment method is to expose the Cistanche deserticola to irradiation 30 cm below the ultraviolet sterilization lamp, and during the irradiation process, rotate to the other side every 10 min to allow the surface to be evenly irradiated; the irradiation time is 30-60 min; the irradiation dose is 1.8-3.6 kJ / m 2 .

[0020] Optionally, in the above-mentioned preservation method for extending the storage period of Cistanche deserticola after harvest and reducing the loss of nutrients, during the packaging process of step S4, the cling film is a PE cling film with a size of 25 cm×50 m and a thickness of 0.01 mm.

[0021] Compared with the prior art, the present invention has the following beneficial effects:

[0022] The present invention uses fresh Cistanche deserticola as raw material, and after selection and precooling, heat treatment-short-wave ultraviolet irradiation-low temperature storage is combined to achieve the purpose of extending the storage period of Cistanche deserticola after harvesting. Heat treatment and short-wave ultraviolet irradiation both have the effects of effectively reducing microbial contamination, changing enzyme activity, maintaining freshness and improving storage quality, are low in price, easy to operate, and free of residue, and have the characteristics of green safety and environmental friendliness, meeting the market and industrial production needs. Combined with low temperature storage, the appearance, weight loss rate, browning degree and hardness loss of fresh Cistanche deserticola after harvesting can be effectively reduced, the activity of antioxidant enzymes can be increased, the activity of browning-related enzymes can be inhibited, and the loss of glycoside components, sugar components, main aroma components and antioxidant activity can be slowed down at the same time, and the storage period of fresh Cistanche deserticola can be extended to 80 days, and the stability of the overall quality and flavor during its storage process can be better maintained. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 Effects of heat treatment and short-wave ultraviolet irradiation alone or in combination on the sensory quality of Cistanche deserticola during storage at 4°C ( Figure 1 A is the difference in weight loss rate, Figure 1 B is the hardness difference, Figure 1 C is the difference in browning degree). The results are expressed as mean ± standard deviation (n=3), and different letters indicate significant differences among different samples (P<0.05).

[0024] Figure 2 The effects of heat treatment and short-wave ultraviolet irradiation alone or in combination on the content of active ingredients in Cistanche deserticola during storage at 4°C ( Figure 2 A is the test result of 7 glycoside components. Figure 2 B is the polysaccharide content test result, Figure 2 C is the result of oligosaccharide content detection). The results are expressed as mean ± standard deviation (n=3), and different letters indicate significant differences between different samples (P<0.05).

[0025] Figure 3 Effects of heat treatment and short-wave ultraviolet irradiation alone or in combination on the in vitro antioxidant activity of Cistanche deserticola during storage at 4°C ( Figure 3 A is the total flavonoids content test result, Figure 3 B is the test result of DPPH free radical scavenging ability. Figure 3 C is the FRAP detection result, Figure 3 D is the result of ABTS free radical scavenging ability test). The results are expressed as mean ± standard deviation (n=3), and different letters indicate significant differences among different samples (P<0.05).

[0026] Figure 4 Effects of heat treatment and short-wave ultraviolet irradiation alone or in combination on the physiological quality of Cistanche deserticola during storage at 4°C ( Figure 4 A is the superoxide anion generation rate detection result, Figure 4 B is the H2O2 content test result, Figure 4 C is the result of SOD activity test. Figure 4 D is the result of CAT activity detection. Figure 4 E is the result of PPO activity detection, Figure 4 F is the POD activity test result, Figure 4 G is the result of soluble quinone content test). The results are expressed as mean ± standard deviation (n=3), and different letters indicate significant differences among different samples (P<0.05).

[0027] Figure 5 This is the fingerprint of volatile organic compounds in Cistanche deserticola.

[0028] Figure 6 The effects of heat treatment and short-wave ultraviolet irradiation alone or in combination on the chromaticity parameter L* ( Figure 6 A), a*( Figure 6 B), b*( Figure 6 C) and overall visual quality ΔE ( Figure 6 The results are expressed as mean ± SD (n = 3), and different letters at each time point indicate significant differences among different treatments (P < 0.05).

[0029] Figure 7 The weight loss rate of fresh-cut Cistanche deserticola during storage at 4°C was evaluated by single or combined treatments of heat treatment and short-wave ultraviolet irradiation. Figure 7 A) and hardness ( Figure 7 The results are expressed as mean ± SD (n = 3), and different letters at each time point indicate significant differences among different treatments (P < 0.05).

[0030] Figure 8 To investigate the effects of heat treatment and short-wave ultraviolet irradiation alone or in combination on the glycosides of fresh-cut Cistanche deserticola during storage at 4°C. Figure 8 A) Polysaccharides ( Figure 8 B) and oligosaccharides ( Figure 8 The results are expressed as mean ± SD (n = 3), and different letters at each time point indicate significant differences among different treatments (P < 0.05).

[0031] Fig. 9 The PCA diagram of volatile organic compounds in fresh-cut Cistanche deserticola at different storage periods ( Fig. 9 A) and Euclidean distance fingerprint ( Fig. 9 B).

[0032] Fig.10 This is the overall appearance of Cistanche deserticola in different groupings and storage periods. DETAILED DESCRIPTION

[0033] In order to make the purpose, technical solution and advantages of the present application more clear, the present application is further described in detail below. However, it should be understood that the description here is only used to explain the present application and is not used to limit the scope of the present application.

[0034] Unless otherwise defined, all technical terms and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art of the present application, and the terms used herein in the specification of the present application are only for the purpose of describing specific embodiments and are not intended to limit the present application. The reagents and instruments used herein are all commercially available, and the characterization means involved can refer to the relevant descriptions in the prior art, which will not be repeated herein.

[0035] In order to further understand the present application, the present application is further described in detail below in conjunction with the best embodiment.

[0036] Example 1

[0037] Comparative experiment on the preservation effect of heat treatment and short-wave ultraviolet irradiation alone or in combination on fresh Cistanche deserticola

[0038] 1. Fresh-keeping treatment:

[0039] (1) Preprocessing:

[0040] Fresh Cistanche deserticola (Cistanche deserticola YCMa) was collected from Suhaitugacha, Bayannuorigongsumu, Zuoqi, Alxa League, Inner Mongolia Autonomous Region (104°48′N, 40°10′E) and immediately transported to the laboratory of the School of Pharmacy, Lanzhou University, Gansu Province. Fleshy stems (single stem weight 488±144 g) with no obvious mechanical damage and pests and uniform size, color, hardness and shape were selected for this study. Fresh Cistanche deserticola was precooled at 4℃ and relative humidity of 70±5% for 24 h before use.

[0041] (2) Experimental groups:

[0042] Control group: no preservation treatment was performed.

[0043] Heat treatment: Immerse the Cistanche deserticola completely in a water bath with a preset temperature of 40°C for 30 min and allow it to air dry naturally after treatment.

[0044] Short-wave ultraviolet irradiation treatment: Cistanche deserticola was exposed to the ultraviolet germicidal lamp at a distance of 30 cm for 30 min. During the irradiation process, it was rotated to the other side every 10 min to ensure that the surface was evenly irradiated. The irradiation time was 30 min. The irradiation dose was 1.8 kJ / m 2 .

[0045] Heat treatment + short-wave ultraviolet irradiation composite treatment: first perform the above-mentioned heat treatment operation, and then perform the above-mentioned short-wave ultraviolet irradiation operation.

[0046] The Cistanche deserticola treated with different methods was tightly wrapped with plastic wrap and stored at 4°C and 70±5% relative humidity for 80 days, with samples taken every 20 days. Three stems were randomly taken from each treatment group at each experimental node as three replicates and thoroughly mixed. One part was quickly frozen with liquid nitrogen and stored at -80°C for physiological index determination and HS-GC-IMS analysis; another part was vacuum freeze-dried, powdered, and stored at -20°C for component content and in vitro antioxidant activity determination.

[0047] 2. Index determination method:

[0048] (1) Weight loss rate and hardness:

[0049] The weight loss rate was determined by weighing method. The ratio of the weight difference of each stem before and after storage to the weight before storage was the weight loss rate of Cistanche deserticola, expressed as a percentage.

[0050] The hardness was measured using a pointer-type fruit hardness tester. About 1 mm of scales were removed from the middle of the upper, middle, and lower sections, and three points were measured at the same distance on the side circumference. The average value was taken as the hardness of Cistanche deserticola (kg / cm 2 ).

[0051] (2)∙O 2- Production rate and H2O2 content:

[0052] The amount of superoxide anions produced per gram of fresh weight (FW) sample per minute was expressed as ∙O 2- Production rate, expressed as nmol / (min·g FW).

[0053] The amount of H2O2 contained in each gram of fresh weight tissue was taken as the H2O2 content, expressed as μmol / g FW.

[0054] (3) Enzyme activity determination:

[0055] The superoxide dismutase (SOD) activity, catalase (CAT) activity, polyphenol oxidase (PPO) activity and peroxidase (POD) activity were determined according to the instructions of the corresponding kits.

[0056] (4) Browning degree and soluble quinones:

[0057] The browning degree was determined by the extinction value method. 1.5 g of fresh sample was ground and homogenized with 17.0 mL of distilled water at 4°C for 20 min, centrifuged at 4000 rpm for 8 min, and the supernatant was incubated in a 25°C water bath for 5 min. The absorbance was measured at a wavelength of 410 nm, and the browning degree was expressed as A410 nm×10.

[0058] Take 1.0 g of fresh sample and homogenize it in 9.0 mL of methanol for 20 min. Centrifuge at 4000 rpm for 5 min, collect the supernatant, and measure the absorbance at 437 nm. The soluble quinone content is A437 nm / g FW.

[0059] (5) Polysaccharides and oligosaccharides:

[0060] Take 0.5 g of powder sample and extract it with 25.0 mL of 80% ethanol solution by ultrasonic (150 w, 40 kHz, 80 ° C) for 30 min. Extract twice, combine the filtrate and dilute to 50.0 mL, and precipitate for use. Take 1.0 mL of filtrate to 10.0 mL test tube in water bath to evaporate alcohol, redissolve with 5.0 mL of water, and dilute to 10.0 mL as oligosaccharide stock solution. The above precipitate evaporates until there is no alcohol smell, and extracts with 25.0 mL of water by ultrasonic (150 w, 40 kHz, 80 ° C) for 30 min. Extract twice, combine the filtrate and dilute to 50.0 mL as polysaccharide stock solution. After reaction using phenol-sulfuric acid method, the absorbance is measured at a wavelength of 490 nm, and the result is expressed as glucose content per kilogram of dry weight (g / kg).

[0061] Accurately weigh 10.00 mg of glucose standard, place it in a 100 mL volumetric flask, and add distilled water to the mark. Prepare a glucose reference stock solution with a concentration of 0.10 mg / mL and store at 4°C for later use. Accurately pipette 0.00 (blank control), 0.20, 0.40, 0.60, 0.80, 1.00, 1.20, 1.60, and 2.00 mL of glucose reference stock solution into a 10 ml stoppered test tube, fill to 2.00 mL with distilled water and react. With glucose concentration as the horizontal axis (X) and A490 nm value as the vertical axis (Y), the standard curve Y=0.0115X+0.0008 (R 2 =0.9994), with a linear range of 0.000-0.001 g / L.

[0062] (6) Glycoside ingredients:

[0063] 1) Sample extraction:

[0064] 1.0 g of powder was sonicated with 50.0 mL of 50% methanol (600 w, 40 kHz, 40 °C) for 40 min, centrifuged (4000 rpm, 5 min), and the supernatant was collected and stored at 4 °C for later use.

[0065] 2) Chromatographic conditions:

[0066] Agilent ZORBAX C18 column (250 mm×4.6 mm, 5 μm), DAD detector, 237 nm, column temperature 30°C, flow rate 1 mL / min, injection volume 10 μL. Mobile phase: acetonitrile (A)-0.5% acetic acid (B), gradient elution conditions: 10-17% A (0-5 min), 17-20% A (5-18 min), 20-23% A (18-35 min), 23-10% A (35-35.01 min), 10% A (35.01-40 min).

[0067] 3) Preparation of standard solution:

[0068] A mixed standard solution containing geniposide (0.350 mg / mL), cistancheside A (0.315 mg / mL), tubuloside A (0.352 mg / mL), echinacoside (0.785 mg / mL), isoverbascoside (0.283 mg / mL), verbascoside (0.340 mg / mL), and 2'-acetylverbascoside (0.343 mg / mL) was prepared with 50% methanol and filtered through a 0.22 μm microporous membrane for chromatographic analysis.

[0069] 4) Sample determination:

[0070] Take the supernatant under the "Sample Extraction" item, filter it through a 0.22 μm microporous filter membrane, and use it for chromatographic analysis.

[0071] (7) In vitro antioxidant activity:

[0072] 1) Total flavonoids content:

[0073] Accurately measure the sample solution under the item "Sample extraction of glycoside components" for determination. The result is expressed as the rutin content per kilogram of dry weight (g / kg). With rutin concentration as the horizontal axis (X) and A505 nm value as the vertical axis (Y), the standard curve is Y=11.629X-0.0044 (R 2 =0.9995), with a linear range of 0.000-0.072 g / L.

[0074] 2) DPPH free radical scavenging ability:

[0075] Take the sample solution under "Sample extraction of glycoside components" for determination and express the result in %.

[0076] 3) ABTS free radical scavenging ability:

[0077] Take the sample solution under the item "Sample extraction of glycoside components" and use 50% methanol as a control to calculate the ABTS free radical scavenging capacity.

[0078] 4) Iron reduction antioxidant capacity determination:

[0079] Take 0.1 mL of the sample under the item "Sample extraction of glycoside components", add 3.0 mL of FRAP reagent, react at 37℃ in the dark for 30 min, measure the absorbance at a wavelength of 596 nm, and the result is expressed as FeSO4 concentration. With FeSO4 concentration as the horizontal axis (X) and A596 nm value as the vertical axis (Y), the standard curve Y=0.6707X-0.0246 (R 2=0.9981), linear range: 0.000-1.924 mmol / L.

[0080] (8) HS-GC-IMS analysis:

[0081] GC-IMS and headspace sampling were used for analysis. 1.0 g of fresh Cistanche deserticola sample was weighed and placed in a 20 mL headspace vial. It was then incubated at 60 °C for 20 min. The centrifugal speed was 500 rpm and the injection needle temperature was 85 °C. Finally, 500 μL of sample was injected. The chromatographic column MXT-5 (30 m×0.53 mm) was used for separation at 60 °C, and N2 (purity ≥99.999%) was used as carrier gas with flow rates of: 0-2 min, 2 mL / min; 2-10 min, 2-10 mL / min; 10-20 min, 10-100 mL / min, and the analysis was stopped after 20 min. The drift tube was maintained at 45 °C under N2 as a drift gas of 150 mL / min. The temperature of the IMS was set to 45 °C. Under the same chromatographic conditions, the retention index (RI) of the identified volatiles was calculated using C4-C9n ketone (Sinopharm Chemical Reagent Beijing Co., Ltd.) as an external reference. The volatile compounds were qualitatively identified by comparing the RI and drift time (DT) of standard compounds in the NIST library and the GC-IMS database. The average of the peak volumes was used to calculate the relative amount of the determined volatiles.

[0082] (9) Data processing:

[0083] All samples were analyzed in triplicate, and the results are expressed as mean ± standard deviation. ANOVA was performed using IBM SPSS19 (SPSS Inc., Chicago, IL, USA), and the differences between means were evaluated using Duncan's test, with significant differences at P < 0.05. PCA and OPLS-DA analyses were performed using SIMCA 14.1 (Sartorius, USA). Cluster heatmaps and Pearson correlation analyses were performed using Origin 2021 (OriginLab Corporation, Northampton, MA, USA).

[0084] 3. Index measurement results:

[0085] (1) Figure 1The figure shows the effects of single or combined treatments of heat treatment and short-wave ultraviolet irradiation on the sensory quality of Cistanche deserticola during storage at 4°C. As can be seen from the figure, compared with other groups, the weight loss rate of the control group increased rapidly, and on the 80th day of storage, the weight loss rate of the control group (9.46%) was significantly higher than that of the short-wave ultraviolet irradiation, heat treatment, and heat treatment + short-wave ultraviolet irradiation groups (P < 0.05). Overall, the weight loss rates of the heat treatment and heat treatment + short-wave ultraviolet irradiation groups were the lowest, and the weight loss rates were only 1.82% and 1.80% after 80 days of storage. Figure 1 As shown in B, the hardness of each group showed a slow downward trend during the entire storage process, but there was no significant difference (P>0.05), which may be due to the protective effect of the attached scales. The browning degree of each group showed a gradual increase during the 80-day low-temperature storage ( Figure 1 C). On the 80th day of storage, the browning degree of the control group (9.20) was significantly higher than that of the heat treatment + short-wave ultraviolet irradiation group (P < 0.05), but there was no significant difference with other treatment groups (P > 0.05). The above results show that the combined treatment of heat treatment + short-wave ultraviolet irradiation can effectively reduce the weight loss rate, browning degree and hardness loss of fresh Cistanche deserticola during low-temperature storage, and maintain a good overall appearance.

[0086] (2) Figure 2 To investigate the effects of heat treatment and short-wave ultraviolet irradiation alone or in combination on the content of active ingredients in Cistanche deserticola during storage at 4°C. Figure 2 As shown in A, the contents of seven glycoside components in the heat treatment group remained high throughout the low-temperature storage process, and reached a maximum value of 12.27 g / kg on the 80th day. In particular, the sum of the contents of echinacoside and verbascoside in the heat treatment group samples was 6.65 g / kg, more than twice the amount specified in the 2020 edition of the "Chinese Pharmacopoeia" (0.3%). This shows that heat treatment can effectively increase the content of glycoside components during low-temperature storage. The polysaccharide content of each treatment group gradually decreased during storage, reaching the lowest value at the end of storage ( Figure 2 B). On the 80th day of storage, the polysaccharide content in the control group (83.51 g / kg) was significantly lower than that in the heat treatment + short-wave ultraviolet irradiation group (144.04 g / kg) (P < 0.05). The oligosaccharide content in each treatment group did not change much during the entire storage period ( Figure 2 C). On the 80th day of storage, the oligosaccharide content in the heat treatment + short-wave ultraviolet irradiation group (283.51 g / kg) was significantly reduced compared with the fresh sample (371.19 g / kg) (P < 0.05), while there was no significant difference in the other treatment groups (P > 0.05). The above results show that the combined treatment of heat treatment + short-wave ultraviolet irradiation can increase the content of glycoside components in Cistanche deserticola during low-temperature storage, while reducing the loss of polysaccharides and oligosaccharides.

[0087] (3) Figure 3 The effects of heat treatment and short-wave ultraviolet irradiation alone or in combination on the in vitro antioxidant activity of Cistanche deserticola during storage at 4°C were investigated. In this study, the total flavonoid content, DPPH free radical scavenging ability and FRAP showed similar fluctuation trends during the entire storage period, all showing a slow increase trend ( Figure 3 A, B and C). At the end of storage, the total flavonoid content, DPPH free radical scavenging ability and FRAP of the heat-treated group (36.81 g / kg, 68.53% and 1.88 mmol / L) were significantly higher than those of the control group (24.25 g / kg, 46.10% and 1.26 mmol / L) and the fresh sample (23.51 g / kg, 58.09% and 1.12 mmol / L) (P < 0.05). Figure 3 As shown in Figure D, the ABTS free radical scavenging capacity of each treatment group was significantly higher than that of the fresh sample (68.51%) (P < 0.05). On the 80th day of storage, compared with the control group (83.29%), the ABTS free radical scavenging capacity of short-wave ultraviolet irradiation (94.08%) and heat treatment (98.92%) increased significantly (P < 0.05), while there was no significant difference between the combined treatment group and the control group (P > 0.05). This indicates that heat treatment and short-wave ultraviolet irradiation alone or in combination can improve the in vitro antioxidant capacity of postharvest Cistanche deserticola to varying degrees.

[0088] (4) Figure 4 The effects of heat treatment and short-wave ultraviolet irradiation alone or in combination on the physiological quality of Cistanche deserticola during storage at 4°C were investigated. 2- The production rate and H2O2 content showed an overall upward trend ( Figure 4 A and B). After 80 days of storage at 4°C, short-wave ultraviolet irradiation, heat treatment, and heat treatment + short-wave ultraviolet irradiation treatment 2- The production rate and H2O2 content were significantly lower than those in the control group (P < 0.05), especially in the short-wave ultraviolet irradiation group (0.56 times and 0.15 times). The SOD activity of each group increased first and then decreased during storage ( Figure 4 C). However, at 80 days of storage, all treatment groups had higher SOD activities than the control group (P < 0.05). The CAT activities of the treatment groups were not statistically different from those of the fresh samples during the entire storage period (P > 0.05) ( Figure 4 D). In this study, heat treatment and short-wave ultraviolet irradiation alone or in combination had a certain inhibitory effect on the activity of PPO and POD ( Figure 4 E and F). Figure 4As shown in Figure G, on the 40th day of storage at 4°C, the soluble quinone content in the heat treatment + short-wave ultraviolet irradiation group was significantly lower than that in the control group (P < 0.05), and was 0.36 times that of the control group. The above research results show that heat treatment and short-wave ultraviolet irradiation alone or in combination can improve the postharvest physiological quality of fresh Cistanche deserticola during low-temperature storage by reducing oxidative stress and reducing the activity of browning-related enzymes.

[0089] (5) Figure 5 This is the fingerprint of volatile organic compounds in Cistanche deserticola. In order to further explore the effects of single or combined treatments of heat treatment and short-wave ultraviolet irradiation on the changes in flavor components of Cistanche deserticola during storage at 4°C, this study used HS-GC-IMS technology to analyze the changes in volatile organic compounds in each sample. In this study, a total of 40 peaks were detected from Cistanche deserticola samples, and 33 volatile compounds were identified, including 12 alcohols, 12 aldehydes, 3 esters, 1 olefin, 2 acids and 3 ketones. Within 80 days of storage at 4°C, the total amount of alcohols, aldehydes and ketones in different treatment groups showed a clear increasing trend. However, the ester components in Cistanche deserticola did not change much during the entire storage period, especially ethyl acetate, which was the most abundant, was the main aroma contributor to all samples. Figure 5 As shown in the figure, the compounds in the red box have higher concentrations in fresh samples, mainly ethyl acetate and limonene with aromatic odor. The compounds in the orange box were detected in fresh samples, and their contents increased significantly in the samples of the control group and the single treatment groups of heat treatment and short-wave ultraviolet irradiation at the end of storage, mainly n-butyraldehyde, 3-methylbutyraldehyde, isopentanol, ethanol and methyl acetate. Ethanol, n-butyraldehyde, 3-methylbutyraldehyde and isopentanol have floral and fruity aromas and are the main aroma contributors in many fruit wines. It is worth noting that the concentrations of these compounds in the combined treatment of heat treatment + short-wave ultraviolet irradiation were relatively low throughout the storage period, indicating that the combined treatment may have a certain effect on fatty acid oxidation or amino acid metabolism during the low-temperature storage of Cistanche deserticola, thereby maintaining the concentrations of alcohol and aldehyde compounds similar to those of fresh samples. The volatile compounds in the green box were mainly high in concentration on the 80th day of storage in the control group, mainly some aldehydes and alcohols, including phenylacetaldehyde, benzaldehyde, 3-methylthiopropionaldehyde, 2-ethylhexanol, n-hexanol, 2-hexanol, cis-2-pentenol and n-octanal, etc. Among them, benzaldehyde, phenylacetaldehyde and 2-ethylhexanol with high content are the main flavor components of cooked jam and tea. If their content exceeds a certain value, the flavor may be reduced.

[0090] The overall appearance of Cistanche deserticola in different groups and storage periods is shown in the figure below. Fig.10 shown.

[0091] The above research results show that the combined treatment of heat treatment + short-wave ultraviolet irradiation can better maintain the quality and flavor stability of fresh Cistanche deserticola, and has good application prospects in the post-harvest storage of Cistanche deserticola.

[0092] Example 2

[0093] Application of heat treatment and short-wave ultraviolet irradiation alone or in combination in the preservation of fresh-cut Cistanche deserticola:

[0094] Fresh Cistanche deserticola is large in size (generally 40-60 cm in length and 2-10 cm in diameter), which may impose certain restrictions on its sales, consumption and product processing methods. In recent years, fresh-cut products have been in great demand worldwide because they can be eaten immediately, which is convenient and retains the fresh characteristics of raw products, which is very consistent with the natural, nutritious and fast-paced lifestyle that people pursue. Cistanche deserticola has a texture similar to that of fruit and is suitable for fresh-cut processing. However, cutting processing can cause severe cell damage, loss of quality such as color, hardness, flavor and excessive water loss, which seriously affects its freshness and shelf life. Therefore, this study further explored the effects of single or combined treatments of heat treatment and short-wave ultraviolet irradiation on the color, weight loss, hardness, active ingredients and flavor of fresh-cut Cistanche deserticola during low-temperature storage, in order to provide more possibilities for the consumption of fresh Cistanche deserticola.

[0095] 1. Fresh-keeping treatment:

[0096] (1) Preprocessing:

[0097] Wash fresh Cistanche deserticola with tap water and air dry. Select the part 15-20 cm away from the root and cut it into thin slices with a thickness of 0.3-0.5 cm. Soak the fresh slices in color-protecting solution (2.5% salt, 0.6% citric acid, 0.10% sodium bisulfite, 0.06% L-cysteine, 0.1% calcium chloride) for 30 minutes, and then treat them according to the following preservation treatment method.

[0098] (2) Experimental groups:

[0099] Control group: no preservation treatment was performed.

[0100] Heat treatment: Place the fresh slices of Cistanche deserticola in a color-protecting solution at 35°C for 1 min and allow to air dry naturally.

[0101] Short-wave ultraviolet irradiation treatment: Fresh slices of Cistanche deserticola were spread out in a single layer, and each side was exposed to a UV-C lamp at a distance of 30 cm from above for 10 min; the irradiation dose was 0.6 kJ / m 2 .

[0102] Heat treatment + short-wave ultraviolet irradiation composite treatment: first perform the above-mentioned heat treatment operation, and then perform the above-mentioned short-wave ultraviolet irradiation operation.

[0103] Fresh slices of Cistanche deserticola after different treatments were placed in PE transparent smooth vacuum bags and vacuumed, and stored at 4°C for 20 days. Three bags of samples were randomly taken out from each group every 5 days as 3 replicates, and the color difference, weight loss rate and hardness were measured. The slices were then cut into small pieces and mixed evenly. One part was quickly frozen with liquid nitrogen and stored at -80°C for HS-GC-IMS determination. One part was vacuum freeze-dried, powdered, and stored at -20°C for component content determination.

[0104] 2. Index determination method:

[0105] (1) Color measurement:

[0106] Measured by colorimeter, color change is determined by , , The value is represented by is the brightness value; Positive values ​​indicate a reddish bias, negative values ​​indicate a greenish bias; Positive values ​​indicate a yellowish tint, negative values ​​indicate a bluish tint. The color difference between the fresh Cistanche deserticola slices and the color difference between the fresh Cistanche deserticola slices is calculated as follows:

[0107]

[0108] Where: The 0th day value; The 0th day value; The 0th day value. The larger the value, The smaller the value, the smaller the browning degree, and vice versa. Six slices were randomly selected from each group to measure the color difference, and each slice was repeated three times.

[0109] (2) Weight loss rate and hardness:

[0110] The weight loss rate is determined by weighing method. The ratio of the weight difference before and after storage to the weight before storage of each bag of samples is the weight loss rate of fresh slices, expressed as a percentage.

[0111] The hardness was measured with a fruit hardness meter. Ten slices were randomly selected from each group. Three positions were selected at equal intervals around the fresh slices (the central circumference of the cylinder side). The hardness of each position was measured and the average value was taken as the hardness of the sample (kg / cm 2 ).

[0112] (3) Glycoside components:

[0113] The determination method of glycoside components is the same as in Example 1.

[0114] (4) Polysaccharides and oligosaccharides:

[0115] The determination method of polysaccharides and oligosaccharides is the same as that in Example 1.

[0116] (5) HS-GC-IMS analysis:

[0117] The HS-GC-IMS analysis method is the same as that in Example 1.

[0118] (6) Data processing:

[0119] The data processing method is the same as that in Example 1.

[0120] 3. Index measurement results:

[0121] (1) Figure 6 The effect of heat treatment and short-wave ultraviolet irradiation alone or in combination on the chromaticity parameters and overall visual quality of fresh-cut Cistanche deserticola during storage at 4°C. As can be seen from the figure, the brightness of the fresh slices in the heat treatment group was best maintained during 20 days of low-temperature storage. The ΔE value showed an opposite trend to L* ( Figure 6 D). As the storage time went by, the ΔE value gradually increased, and the heat treatment group was always at the lowest value, while the value of the control group was significantly higher than that of other preservation treatment groups from the 15th day (P < 0.05). In addition, the a* value of the control group was always significantly higher than that of other preservation treatment groups (P < 0.05), while b* had no significant difference during storage (P > 0.05). In summary, heat treatment and short-wave ultraviolet irradiation alone or in combination can maintain the brightness and color of fresh slices to varying degrees.

[0122] (2) Figure 7 The figure shows the effects of single or combined treatments of heat treatment and short-wave ultraviolet irradiation on the weight loss rate and hardness of fresh-cut Cistanche deserticola during storage at 4°C. As can be seen from the figure, within 20 days of storage at 4°C, there was no statistical difference in the weight loss rate between the control group and the short-wave ultraviolet irradiation group (P>0.05), and both reached the highest value at the end of storage (10.32% and 10.47%). The weight loss rates of the heat treatment + short-wave ultraviolet irradiation and heat treatment groups showed the same increasing trend, and were higher than the other two treatment groups on the 10th day of storage. It is speculated that the heat treatment increased the weight loss of the slices. Figure 7 As shown in Figure B, similar to the results of fresh samples, the hardness of fresh slices in each group showed a slow decreasing trend during the entire storage process, but there was no significant statistical difference among the treatment groups (P>0.05).

[0123] (3) Figure 8The aim of this study was to investigate the effects of heat treatment and short-wave ultraviolet irradiation alone or in combination on the contents of glycosides and carbohydrates in fresh-cut Cistanche deserticola during storage at 4°C. On the 20th day of storage at 4°C, the contents of seven main glycosides in the fresh slices of the control group and the heat treatment + short-wave ultraviolet irradiation group were higher, with the total contents being 13.984 g / kg and 11.235 g / kg, respectively. The sum of the contents of echinacoside and verbascoside were 3.351 g / kg and 3.160 g / kg, respectively. Compared with the control group, short-wave ultraviolet irradiation significantly increased the polysaccharide content of the slices (P < 0.05), while there was no significant difference between the heat treatment and heat treatment + short-wave ultraviolet irradiation groups (P > 0.05). Figure 8 B). The oligosaccharide content of each preservation treatment group at the end of storage was significantly higher than that of the control group, but significantly lower than that of the fresh sample (P < 0.05) ( Figure 8 C). This may be due to the high water solubility of oligosaccharides.

[0124] (4) Fig. 9 The cluster analysis results of volatile organic compounds in fresh-cut Cistanche deserticola at different storage periods. Through the principal component analysis of volatile compounds, PC1 is 32%, PC2 is 21%, and the cumulative total contribution rate is 53%. However, the fresh samples can be clearly separated from the samples stored at 4°C for 10 and 20 days, which indicates that the storage time has a greater impact on the flavor of fresh slices than the different preservation treatments. In addition, based on the fingerprint map of Euclidean distance, the distance between the heat treatment + short-wave ultraviolet irradiation group and the fresh samples is closer ( Fig. 9 B), which indicates that heat treatment + short-wave ultraviolet irradiation can maintain the flavor of fresh slices of Cistanche deserticola better during low-temperature storage.

[0125] The results of the above examples show that heat treatment and short-wave ultraviolet irradiation alone or in combination have a positive effect on the sensory quality, physiological quality, active ingredients, antioxidant capacity and flavor of fresh Cistanche deserticola during low-temperature storage. In addition, heat treatment and short-wave ultraviolet irradiation alone or in combination can maintain the high level and stability of the sensory quality, active ingredients and aroma-related volatiles of fresh-cut Cistanche deserticola to a certain extent. Both heat treatment and short-wave ultraviolet irradiation can be considered as green, safe and effective preservation technologies for maintaining the post-harvest quality of fresh Cistanche deserticola.

[0126] Comparative Example 1

[0127] The treatment method for Cistanche deserticola in this comparative example is the same as the heat treatment group in Example 1, except that the preset temperature is 50°C.

[0128] The experimental results showed that on the 80th day of storage at 4°C, the weight loss rate of the treatment group had no significant difference with the heat treatment group and the heat treatment + short-wave ultraviolet irradiation combined group in Example 1 (P>0.05), and was significantly lower than the short-wave ultraviolet irradiation group (P<0.05); the browning degree of the treatment group had no significant difference with the heat treatment + short-wave ultraviolet irradiation combined group in Example 1 (P>0.05), and was significantly lower than the heat treatment and short-wave ultraviolet irradiation single treatment group (P<0.05); the hardness of the treatment group had no significant difference with each treatment group in Example 1 (P>0.05). Further research found that at the end of storage, the contents of 7 glycosides, polysaccharides and oligosaccharides in the treatment group were significantly lower than those in the heat treatment group in Example 1. This shows that the heat treatment temperature has a good inhibitory effect on the weight, hardness and color loss of fresh Cistanche deserticola during low-temperature storage, but the retention effect on the effective ingredients is not as good as that of the heat treatment group in Example 1.

[0129] Comparative Example 2

[0130] The treatment method for Cistanche deserticola in this comparative example is the same as the heat treatment group in Example 1, except that the preset temperature is 60°C.

[0131] The experimental results showed that on the 80th day of storage at 4°C, the weight loss rate of the treatment group was not significantly different from that of the short-wave ultraviolet irradiation group in Example 1 (P>0.05), but was significantly higher than that of the heat treatment group and the heat treatment + short-wave ultraviolet irradiation combined group (P<0.05); the browning degree was significantly higher than the three preservation treatment groups in Example 1 (P<0.05); and the hardness decreased the fastest, reaching the lowest value of 6.16 kg / cm on the 80th day of storage. 2 , which was significantly lower than that of each treatment group (P<0.05). The results showed that too high temperature (60℃) may cause great damage to the epidermal cells of fresh Cistanche deserticola, and accelerate the process of browning, mildew, and even decay, which is not suitable for post-harvest storage and preservation of Cistanche deserticola.

[0132] Comparative Example 3

[0133] The treatment method for Cistanche deserticola in this comparative example is the same as the short-wave ultraviolet irradiation treatment group in Example 1, except that the irradiation time is 60 min and the irradiation dose is 3.6 kJ / m 2 .

[0134] The experimental results showed that on the 80th day of storage at 4°C, the weight loss rate of this treatment group was significantly higher than that of the three preservation treatment groups in Example 1 (P < 0.05), and was 1.34 times that of the short-wave ultraviolet irradiation treatment group. This result showed that long-term short-wave ultraviolet irradiation would increase the weight loss of Cistanche deserticola after harvest.

[0135] Comparative Example 4

[0136] The heat treatment method for Cistanche deserticola in this comparative example is the same as the heat treatment + short-wave ultraviolet irradiation combined treatment group in Example 1, except that the preset temperature of the heat treatment is 30°C.

[0137] The experimental results showed that on the 80th day of storage at 4°C, the weight loss rate of the treatment group was not significantly different from that of the short-wave ultraviolet irradiation single treatment group in Example 1, but was more than twice that of the heat treatment + short-wave ultraviolet irradiation combined treatment group. This result shows that when the heat treatment temperature is too low, the heat treatment + short-wave ultraviolet irradiation combined treatment does not significantly improve the post-harvest preservation effect of Cistanche deserticola.

[0138] Comparative Example 5

[0139] The heat treatment method for Cistanche deserticola in this comparative example is the same as the heat treatment + short-wave ultraviolet irradiation combined treatment group in Example 1, except that the short-wave ultraviolet irradiation time is 15 min and the irradiation dose is 0.9 kJ / m 2 .

[0140] The experimental results showed that on the 80th day of storage at 4°C, the weight loss rate of the treatment group was not significantly different from that of the heat treatment group and the heat treatment + short-wave ultraviolet irradiation combined group in Example 1 (P>0.05); the browning degree of the treatment group was about 1.2 times that of the heat treatment + short-wave ultraviolet irradiation combined group; the hardness of the treatment group was about 0.9 times that of the heat treatment + short-wave ultraviolet irradiation combined group. The results show that when the short-wave ultraviolet irradiation time is too short, the heat treatment + short-wave ultraviolet irradiation combined treatment does not significantly improve the post-harvest preservation effect of Cistanche deserticola.

[0141] The comparison results of weight loss rate, browning degree and hardness of Example 1 and the comparative example samples stored at 4°C on the 80th day are shown in Figure 1.

[0142] Table 1

[0143]

[0144] The above description is only a preferred embodiment of the present application and is not intended to limit the present application. Any modifications, equivalent substitutions or improvements made within the spirit and principles of the present application should be included in the protection scope of the present application.

Claims

1. A method for preserving Cistanche deserticola for prolonging its storage period and reducing the loss of nutrients, characterized in that: The method is to pre-cool the fresh Cistanche deserticola after harvesting, soak it in hot water and irradiate it with short-wave ultraviolet rays, and then store it in a low-temperature environment.

2. A preservation method for extending the storage period of Cistanche deserticola after harvest and reducing the loss of nutrients according to claim 1, characterized in that: The following steps are involved: S1. Material pretreatment: Select fresh fleshy stems of Cistanche deserticola as the material and precool them; S2. Heat treatment: completely immerse the Cistanche deserticola in a water bath at a preset temperature and allow it to air dry naturally after treatment; S3. Short-wave ultraviolet irradiation: expose Cistanche deserticola to ultraviolet sterilization lamp; S4. Packaging and storage: Wrap the processed Cistanche deserticola tightly with plastic wrap and store it at a temperature of 4°C and a relative humidity of 65-75%.

3. A preservation method for extending the storage period of Cistanche deserticola after harvest and reducing the loss of nutrients according to claim 2, characterized in that: In the step S1, the selected fresh Cistanche deserticola is the one dug in spring or autumn without obvious mechanical damage and pests and diseases, and the fleshy stem is taken.

4. A preservation method for extending the storage period of Cistanche deserticola after harvest and reducing the loss of nutrients according to claim 2, characterized in that: In step S1, the precooling treatment conditions are: temperature 4°C, relative humidity 65-75%, and precooling time 24 hours.

5. A preservation method for extending the storage period of Cistanche deserticola after harvest and reducing the loss of nutrients according to claim 2, characterized in that: In step S2, the preset temperature of the water bath for heat treatment is 40-60° C., and the treatment time is 30 min.

6. A preservation method for extending the storage period of Cistanche deserticola after harvest and reducing the loss of nutrients according to claim 2, characterized in that: In the short-wave ultraviolet irradiation treatment of step S3, the ultraviolet sterilization lamp is an ozone-free double-ended ultraviolet sterilization lamp with a tube diameter of 19 mm, a power of 30 W and a central wavelength of 253.7 nm; the treatment method is to expose the Cistanche deserticola to irradiation 30 cm below the ultraviolet sterilization lamp, and during the irradiation process, rotate to the other side every 10 minutes to allow the surface to be evenly irradiated; the irradiation time is 30-60 minutes; the irradiation dose is 1.8-3.6 kJ / m 2 .

7. A preservation method for extending the storage period of Cistanche deserticola after harvest and reducing the loss of nutrients according to claim 2, characterized in that: In the packaging process of step S4, the cling film is a PE cling film with a size of 25 cm×50 m and a thickness of 0.01 mm.

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