Effect Of Methyl Jasmonate On Storage Quality Of Fresh-cut Cistanche Deserticola

Abstract 

To investigate how methyl jasmonate (MeJA) affects the storage quality of fresh-cut Cistanche deserticola, we immersed fresh-cut Cistanche deserticola in MeJA solutions of 100, 150, and 200 µmol/L concentrations and measured changes in hardness, weight loss rate, total soluble solids (TSS), total colony count, color, browning degree, total phenol content, polyphenol oxidase (PPO), peroxidase (POD), and malondialdehyde (MDA) content during storage. 

Results indicated that after 14 days of storage, fresh-cut Cistanche deserticola treated with 200 µmol/L MeJA showed a decrease in MDA, PPO, and POD activities by 21.32%, 23.62%, and 24.08%, respectively, while the total phenol content increased by 33.68%, resulting in higher antioxidant capacity and a significant delay in the degree of browning during storage. MeJA treatment also slowed down color changes and weight loss during storage, reduced the total colony count by 23.88%, and increased the hardness and TSS content by 17.89% and 40.22%, respectively, effectively maintaining the storage quality of fresh-cut Cistanche deserticola. This study contributes theoretical support for developing preservation techniques and extending the shelf life of fresh-cut Cistanche deserticola. 

Keywords: fresh-cut Cistanche deserticola; Methyl jasmonate (MeJA); storage quality; correlation analysis; principal component analysis

HOW LONG DOES IT TAKE FOR CISTANCHE TO WORK?

Cistanche deserticola is a perennial parasitic herbaceous plant of the genus Cistanche of the Orobanchiaceae family. It is a precious Chinese herbal medicine. The varieties of Cistanche deserticola recorded in the herbal medicine of the past dynasties include Cistanche deserticola Ma and Cistanche salsa (C. A. Mey.) G. Beck [ 1]. In 2023, Desert Cistanche deserticola was officially listed as a Chinese herbal food with the same origin as medicine and food and is widely used in health foods in my country [2]. Desert Cistanche deserticola is often used to nourish kidney yang, strengthen muscles and bones, replenish essence and blood, and prolong life. It enjoys the reputation of "desert ginseng" [3]. In terms of consumption, processing and utilization, desert Cistanche deserticola is mostly made into dried flakes for consumers to eat. However, the drying process will cause the loss of some nutrients of Cistanche deserticola. With the fast-paced development, consumers prefer ready-to-eat, highly nutritious food. Fresh-cut desert cistanche deserticola is easy to eat and has a fresh texture, which can meet people's daily needs. However, fresh cutting exposes Cistanche deserticola directly to the air, which accelerates the browning and microbial contamination of fresh-cut desert Cistanche deserticola, affects the sensory and storage quality, and shortens the shelf life [4]. In order to facilitate sales, fresh-cut desert Cistanche deserticola can be packaged in vacuum packaging, but this cannot effectively delay the browning of Cistanche deserticola. As the market and consumer demand for fresh-cut Cistanche deserticola increases, there is an urgent need to solve its storage problem.

Methyl jasmonate (MeJA) is a volatile ester derivative of jasmonic acid. It has been proven to be an endogenous hormone widely present in plants. It has a variety of physiological effects and can delay the aging process of fruits and vegetables during postharvest storage. , improve storage quality [5]. The application of MeJA as a preservative can increase the content of antioxidant substances in fruits and vegetables, enhance the activity of antioxidant enzymes, effectively inhibit physiological changes such as oxidative browning and membrane lipid peroxidation of fresh fruits, and extend the storage period of fruits and vegetables [6]. Studies have shown that MeJA treatment can reduce the occurrence of chilling injury in peaches during storage [7]; Liu [8] and others found that MeJA treatment can enhance the disease resistance of kiwi fruit and extend its shelf life. Liang Xiwen[9] found that

0.15 mmol/L MeJA treatment can inhibit the color change and decrease in hardness of the fruit, increase the total phenolic content, and extend the storage period of sweet cherries. Xue Pengyu et al. [10] found that treatment with 100 μmol/L MeJA can reduce the activity of PPO in longan fruits after harvest, increase the total phenolic content of the peel, and enhance its antioxidant capacity, thereby delaying the occurrence of postharvest longan peel browning and extending the shelf life. . Yan Yanhua [11] found that methyl jasmonate treatment reduced the activity of PPO and POD in the body, delayed the browning phenomenon, maintained the color and flavor of yam, and delayed its aging.

There are currently no reports on the effect of MeJA on the storage quality of fresh-cut desert Cistanche deserticola. Therefore, this study selected MeJA as a preservative to treat vacuum-packed fresh-cut desert Cistanche deserticola, to explore the effect of MeJA treatment on the storage quality of fresh-cut desert Cistanche deserticola during storage, and to provide a theoretical basis for the application of MeJA in the storage and preservation of fresh-cut desert Cistanche deserticola.

1 Materials and methods

1.1 Test materials

Desert Cistanche deserticola was picked in Minqin County, Wuwei, Gansu Province and quickly transported back to the laboratory and pre-cooled at 4°C for 24 hours.

Methyl jasmonate (≥ 95%, BR), Shanghai Yuanye Biotechnology Co., Ltd.; Tween-80, absolute ethanol, Tianjin Kaixin Chemical Industry Co., Ltd.; Fulin-Shauka test solution, Xiamen Haibiao Technology Co., Ltd.; Catechol, thiobarbituric acid, sodium carbonate, gallic acid, sodium dihydrogen phosphate, disodium hydrogen phosphate, guaiacol, Tianjin Damao Chemical Reagent Factory; hydrogen peroxide, trichloride Acetic acid, polyvinylpyrrolidone, Tianjin Guangfu Technology Development Co., Ltd.

1.2 Main instruments

UV-2550 UV-visible spectrophotometer, Shimadzu Company, Japan; H-1850R desktop high-speed refrigerated centrifuge, Changsha Xiangyi Centrifuge Instrument Co., Ltd.; Spectramax M2 microplate reader, American Megu Molecular Instrument Co., Ltd.; TA. . Express C texture analyzer, Stable Micro Systems Company, UK; PAL-1 handheld digital sugar meter, ATAGO Company, Japan.

1.3 Test methods

1.3.1 Sample processing

Dissolve MeJA in 0.01% absolute ethanol, then add 0.1% Tween-80. The control group is an aqueous solution of 0.01% absolute ethanol and 0.1% Tween-80. Select desert Cistanche deserticola that is free from pests, diseases, and mechanical damage, has a diameter of 5-6 cm, and a length of 50-60 cm as test materials. The concentrations of MeJA were determined through preliminary experiments to be 100 µmol/L, 150 µmol/L, and 200 µmol/L, respectively. Wash and peel the fresh Cistanche deserticola and immediately cut it into 1 cm thick round pieces, and soak them in MeJA solution for 30 min (marked as M1, M2, M3 respectively). The CK group was treated with absolute ethanol and Soak in Tween-80 aqueous solution for 30 minutes, remove until no water drips from the surface, vacuum package (polyester vacuum bag PET, 0.16 mm) and store at 4±1°C. Samples were taken for measurement every 2 days, and each set of experiments was repeated three times.

times, and the results are expressed as mean ± standard deviation.

1.3.2 Indicator determination

1.3.2.1 Determination of total number of bacterial colonies

Refer to GB4789.2-2022 "National Food Safety Standard - Food Microbiological Inspection - Determination of Total Bacterial Count" for measurement, and the unit is expressed in lg (CFU/g).

1.3.2.2 Hardness

Determined using a texture analyzer. Each treatment group randomly selected 6 pieces of fresh-cut desert cistanche. Test conditions: Use a P/2 model probe, pre-test speed 2.0 mm/s, test speed 1.0 mm/s, post-test speed 1.0 mm/s, probe test distance is 3.0mm.

1.3.2.3 Weight loss rate

The weight loss rate is measured using the weighing method.

1.3.2.4 Soluble solids

Measured using a hand-held digital sugar content meter. Weigh 5 g of desert Cistanche deserticola sample, add 20 mL of distilled water, homogenize and filter with gauze to extract the juice for measurement.

1.3.2.5 Color

A colorimeter was used to determine the L*, a*, and b* values of fresh-cut desert Cistanche deserticola. Six pieces of fresh-cut desert Cistanche deserticola were randomly selected from each treatment group and measured three times.

1.3.2.6 Browning degree

It was measured using the extinction value method [12] with slight modifications. Take 1.0 g of desert Cistanche deserticola sample, add 10 mL of distilled water, homogenize and centrifuge at 4°C and 10 000 r/min for 10 min. Take the supernatant and soak it in a water bath at 25°C for 5 minutes at a constant temperature. Measure the absorbance value at 410 nm, and the results are expressed as OD410.

1.3.2.7 Total phenols

The Folin phenol method [13] was used to measure, and gallic acid was used as a standard curve to calculate the total phenolic content in mg/100 g.

1.3.2.8 PPO and POD activity

Extraction of enzyme solution: Take 1.0 g desert Cistanche deserticola sample, add 5.0 mL of pre-cooled phosphate buffer containing 0.1% (w/v) Triton X-100 and 0.5 g insoluble polyvinyl polypyrrolidone (PVPP) (pH 7.0) , grind the homogenate under ice bath conditions and transfer it to a centrifuge tube, then rinse the mortar with 5.0 mL phosphate buffer, combine the extracts, and centrifuge at 12 000 r/min for 15 min at 4°C. The supernatant is the enzyme The crude extract was collected and stored in a refrigerator at 4°C until use.

PPO activity was measured using a colorimetric method [14]. POD activity was determined using the guaiacol method [14].

1.3.2.9 Malondialdehyde

It is based on the method of Yu Jun [15] with slight modifications. Take 1.0 g desert Cistanche deserticola sample and extract it with trichloroacetic acid (TCA) solution, and then measure the absorbance at 450, 532 and 600 nm.

1.4 Data analysis

Excel 2021 was used for data statistics, SPSS Statistics 25.0 was used for one-way analysis of variance (ANOVA), Duncan's multiple range test was used for significance (P<0.05), and Origin 2021 was used for plotting.