A method to inhibit discoloration of white strawberry skin and thus maintain its original commercial value

Abstract

This invention belongs to the agricultural field and relates to a method for inhibiting the discoloration of white strawberry skin to maintain its original marketability. Specifically, for greenhouse-grown strawberries, the covering material for the top of the strawberry greenhouse is glass or greenhouse film that meets the following conditions: the transmittance of ultraviolet light with a wavelength ≤350nm does not exceed 10%, while the transmittance of ultraviolet light with a wavelength >350nm exceeds 90%; the above-mentioned covering material is used throughout the entire strawberry growing period. This invention has virtually no significant impact on strawberry yield and quality, and can effectively inhibit the color change of white strawberry skin to pink / red, thereby maintaining its original marketability.

Description

Technical Field

[0001] This invention belongs to the agricultural field, specifically relating to a method for inhibiting the discoloration of white strawberry skin, that is, a method for inhibiting the color of white strawberry skin from turning pink / red. Background Technology

[0002] Strawberries, belonging to the genus *Fragaria* of the Rosaceae family, are perennial herbaceous plants. Their fruits are soft, juicy, sweet and sour, and rich in nutrients, earning them the title of "Queen of Fruits." In recent years, my country's strawberry industry has developed rapidly, making it the world's largest producer and consumer. With the development of greenhouse cultivation techniques, strawberries have become a popular winter fruit with high harvest rates, generating significant economic benefits and driving the development of agritourism. In recent years, strawberry varieties have also diversified. Currently, the most common cultivated strawberry varieties are those with red skin, also known as red strawberries. In addition, there are varieties with white or pink skin. White strawberries, in particular, with their unique and rare color, have become a high-end variety in the strawberry world, highly sought after by consumers, and their selling price is more than 50% higher than that of common red strawberries. However, when planting these white strawberry varieties, it was found that the white color of the fruit skin remained unstable. Specifically, the fruit skin was normally white from December to February of the following year, but from February to May before the end of the strawberry season, the color of the fruit skin gradually turned pink or even light red, which greatly affected the marketability of the strawberry fruit. Moreover, in some places, white strawberries showed signs of turning pink as early as the beginning of February, and some pink strawberry varieties also showed the phenomenon of turning red.

[0003] The main reason strawberries turn red is the synthesis of anthocyanins, an important class of flavonoids in plants that play a crucial role in color formation and antioxidant processes in flowers, fruits, and other organs. Many factors influence anthocyanin synthesis, including fertilizers, temperature, and light. Anthocyanin formation in plant tissues depends on light signals, specifically light intensity, light quality, and photoperiod.

[0004] A strawberry greenhouse is a greenhouse specifically designed for strawberry cultivation. The greenhouse frame is typically made of steel pipes, bamboo, wood, or plastic; the greenhouse itself is constructed from transparent, semi-transparent, or opaque materials. The greenhouse roof is generally made of transparent or semi-transparent materials, such as glass, plastic film (soft or hard), and rigid plastic sheets. Common glass types include ordinary flat glass or float glass; common plastic films include polyethylene (PE) film, ethylene-vinyl acetate (EVA) film, polyvinyl chloride (PVC) film, polyolefin (PO) film, and light-converting film; commonly used rigid plastic sheets are primarily polycarbonate (PC), including hollow sheets and corrugated sheets.

[0005] To solve the above problems, current technologies employ the following methods:

[0006] Method 1: Fruit bagging is used to keep the fruit white, but this method is time-consuming. Strawberries have a continuous flowering and fruiting pattern, making it difficult to bag each one. Moreover, bagging strawberry fruits can easily cause diseases and rot, and it is impossible to determine whether they are ripe.

[0007] Method 2: Using strawberry leaves to block direct sunlight from shining on the fruit, some strawberries that were blocked by leaves did turn white, but many that were not blocked still turned pink or red.

[0008] Method 3: Use shade nets to block sunlight. That is, set up shade nets on the top of the greenhouse. Polypropylene film (PP) is the main material for making shade nets. Although it has a certain effect, strawberries are a crop that likes sunlight. Shading will significantly affect the yield and quality of strawberries, so it is not worth the effort. Summary of the Invention

[0009] The technical problem to be solved by the present invention is to provide a method that has virtually no significant impact on strawberry yield and quality, and can suppress the color change of white strawberry skin to pink / red.

[0010] To solve the above-mentioned technical problems, the present invention provides a method for inhibiting discoloration of white strawberry peel:

[0011] For greenhouse-grown strawberries, the covering material for the top of the strawberry greenhouse should be glass or greenhouse film that meets the following conditions:

[0012] The transmittance of ultraviolet light with a wavelength ≤350nm is no more than 10%, while the transmittance of ultraviolet light with a wavelength >350nm exceeds 90%.

[0013] The aforementioned covering material was used throughout the entire strawberry growing season.

[0014] The greenhouse film is a light-converting film.

[0015] By planting white or pink strawberry varieties in the greenhouse according to the above setup, the white or pink color of the strawberries can be kept from deepening throughout the entire harvest period (i.e., inhibiting the white strawberry skin from turning pink or red), thus maintaining the marketability of the fruit. At the same time, it does not affect the strawberries' access to sunlight, ensuring the overall yield and quality of the strawberries.

[0016] In the process of inventing this invention, the following issues were fully considered:

[0017] According to their different biological effects, ultraviolet light in the solar spectrum can be divided into ultra-strong effect waves (UV-C, 220-280nm), strong effect waves (UV-B, 280-320nm), and weak effect waves (UV-A, 320-380nm). Since most of the (UV-C, 220-280nm) is absorbed and blocked by the atmosphere, the ultraviolet cutoff point of sunlight reaching the ground varies in different regions. The ultraviolet cutoff point of sunlight in plateau areas is 296nm, in northwestern desert areas it is 297nm, and in tropical ocean areas it is 298nm.

[0018] This invention analyzes the reasons for the pinkening of strawberry skin, discovering that ultraviolet light in the spectrum is the main cause of the pinkening of white strawberry skin. Further research revealed that the ultraviolet light region with wavelengths below 350nm has the most significant impact on this color change. Therefore, the ideal light-transmitting covering material should first have high transmittance in the 400-700nm photosynthetically active radiation (PAR) region and low transmittance in other wavelength ranges. Then, the covering material for the top of the strawberry greenhouse is set to meet the following conditions: transmittance of ultraviolet light with wavelengths ≤350nm not exceeding 10%, while transmittance of ultraviolet light with wavelengths >350nm exceeding 90%.

[0019] The present invention has the following technical advantages: the raw materials are easy to obtain, it has no impact on the quality and yield of strawberries, and it is easy to operate.

[0020] This invention can effectively suppress the phenomenon of white strawberries gradually turning pink during cultivation. Based on theory and practice, this invention provides a solution. Attached Figure Description

[0021] The specific embodiments of the present invention will be further described in detail below with reference to the accompanying drawings.

[0022] Figure 1 For strawberry greenhouses covered with plastic film;

[0023] Figure 2 A strawberry greenhouse with glass covering;

[0024] Figure 3 A comparison of fruit color on March 30th between glass (left) and PO film (right) as covering materials.

[0025] Figure 4 for Figure 3 Enlarged schematic diagram of the fruit: the left image shows glass as the covering material, and the right image shows PO film as the covering material. Detailed Implementation

[0026] The present invention will be further described below with reference to specific embodiments, but the scope of protection of the present invention is not limited thereto:

[0027] Example 1: Strawberry fruit color under different greenhouse coverings

[0028] Methods: The white strawberry variety "Meng Zhi Ying" was selected. Greenhouse cultivation took place from September of the current year to May of the following year, with fruit production beginning in December. When the white strawberries were transplanted into the greenhouse, the top of the greenhouse was covered with the covering material described in Table 1. Then, the cultivation was managed according to conventional greenhouse strawberry cultivation methods. From December to March of the following year, 30 fruits were observed monthly for each sample. The fruit color was observed and categorized into white, pink, and red. Observation was done visually, and the results are shown in Table 1.

[0029] Table 1: Observation of strawberry fruit color under different greenhouse coverings

[0030]

[0031] Glass must meet the requirement that its transmittance for ultraviolet light with a wavelength ≤350nm does not exceed 10%, while glass with a wavelength >350nm ultraviolet light is also acceptable. PO film, PVC film, and light-converting film are all conventional commercially available products.

[0032] Table 1 shows that the fruit covered with glass remained white throughout, while those covered with PO film turned light pink from February onwards and then pink after March. The fruit covered with PVC film turned light pink after February, and the color did not deepen in March. The fruit covered with light-converting film began to turn light pink after March. Therefore, the color of white strawberries varied significantly under different covering materials. See Table 1 for details. Figure 3 and Figure 4 .

[0033] Example 2: The white strawberry variety in Example 1 was changed to "Mengzhijiao". The results obtained were not significantly different from those in Example 1.

[0034] Therefore, it can be shown that the method of the present invention is applicable to all white strawberries.

[0035] Experiment 1: Average single fruit weight and soluble solids content of strawberries under different greenhouse coverings

[0036] Implementation method (same as Example 1): The strawberry variety selected was Mengzhiying. The high-ridge planting mode in the facility was adopted, and four treatments were designed. Treatment 1 was covered with glass, treatment 2 was covered with PO film, treatment 3 was covered with PVC film, and treatment 4 was covered with light-converting film. After the strawberries were planted, conventional and uniform cultivation management was carried out. From December to March of the following year, random monthly sampling was conducted to measure the weight of single fruit and the solid content. The weight of single fruit was weighed using an electronic scale (accuracy 0.01g), and the soluble solid content was measured using an AtagoPAL-1 digital display saccharimeter.

[0037] Table 2: Average single fruit weight and soluble solids content of strawberries under different greenhouse coverings The data in Table 2 show that there were no significant differences in the average single fruit weight and soluble solids content among the treatments, which indirectly proves that the treatments had no significant impact on strawberry yield and sugar content.

[0038] Finally, it should be noted that the above examples are merely some specific embodiments of the present invention. Obviously, the present invention is not limited to the above embodiments and many variations are possible. All variations that can be directly derived or conceived by those skilled in the art from the disclosure of the present invention should be considered within the scope of protection of the present invention.

Claims

1. A method for inhibiting discoloration of white strawberry peel, characterized in that: For greenhouse-grown strawberries, the roof covering material of the strawberry greenhouse should be glass that meets the following conditions: The transmittance of ultraviolet light with a wavelength ≤350nm is no more than 10%, while the transmittance of ultraviolet light with a wavelength >350nm exceeds 90%. The aforementioned covering material was used throughout the entire strawberry growing season.

2. The method for inhibiting discoloration of white strawberry peel according to claim 1, characterized in that: It can inhibit the white strawberry skin from turning pink or red.

3. The method for inhibiting discoloration of white strawberry peel according to claim 1 or 2, characterized in that: To maintain the marketability of white strawberry fruit.

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