Application of sorbitol in improving hardness of grape fruits

Abstract

The invention relates to the technical field of fruit quality improvement, in particular to application of sorbitol in improvement of grape fruit hardness. A large number of field trials verify that after sorbitol is adopted for treatment, the fruit hardness of the four grape varieties of'red double flavor ', 'rose flavor', 'sunshine rose 'and'Italian' is remarkably improved compared with that of a control group; in addition to improvement of fruit hardness, the method disclosed by the invention can also promote fruit color uniformity, increase the content of soluble solids, reduce the content of titratable acids, enable the fruit flavor to be better, enhance the oxidation resistance, and improve the overall commodity value of the grape fruits. The sorbitol adopted by the invention is a natural or biodegradable substance, is environment-friendly and has no residual pollution; the pesticide preparation and spraying operation is simple, complex equipment is not needed, and the cost is low.

Description

Technical Field

[0001] This invention relates to the field of fruit quality improvement technology, and in particular to the application of sorbitol in improving the firmness of grapes. Background Technology

[0002] Grapes belong to the family Vitaceae, genus Vitis (Vitis). Vitis Grapes are perennial plants and one of the oldest species in the world. Their fruit can be eaten fresh, used for winemaking, and dried, and has high economic value. Grapes occupy a very important position in global fruit production. According to statistics from the Food and Agriculture Organization of the United Nations (FAO), in 2022, the world's vineyard harvested area was 6.7302 million hectares, with a total output of 74.9426 million tons. my country's total grape cultivation area was 705,100 hectares, ranking fourth in the world, after Spain, France, and Italy; its output reached 15.3779 million tons, an increase of 2.53% compared to the same period in 2021, and it has consistently ranked first in the world in grape production since 2010. my country's grape industry has developed rapidly and is currently the fourth largest fruit producer in the country, after apples, citrus fruits, and pears. In 2022, the total grape output accounted for 4.91% of the country's total fruit output (312.9624 million tons). In terms of global grape production, nearly 70% of grapes are used for processing and over 30% are used for fresh consumption. In my country, however, fresh consumption is the main focus, accounting for more than 70%. Fresh grape production is the mainstay of my country's grape industry.

[0003] Grapes are a typical non-climacteric fruit, meaning their softening occurs earlier than that of climacteric fruits. As berries with thin skins and abundant juice, they are prone to cracking and rotting during consumption, transportation, and storage. Furthermore, the concentrated harvest season for most grape varieties frequently leads to difficulties for growers in selling their fruit and resulting in low prices. Improving grape firmness can significantly increase the fruit's storage and transport resistance, allowing for staggered harvesting, greatly enhancing its economic value, and effectively extending its supply period.

[0004] In viticulture, improving fruit firmness is crucial for ensuring the quality and commercial value of grapes during post-harvest storage and transportation. Currently, common techniques for improving grape fruit firmness mainly include adjusting cultivation management practices (such as controlling water and fertilizer, and pruning) and using chemical regulators. While traditional cultivation management practices are relatively green and safe, their effects on improving fruit firmness are limited and are greatly affected by environmental factors, making precise control difficult. On the other hand, while some chemical regulators can improve fruit firmness to a certain extent, they can easily lead to fruit deformities, deteriorated flavor, and even the risk of excessive pesticide residues, posing potential harm to human health and the ecological environment. Therefore, there is an urgent need to develop a safe, efficient, and significantly effective new technology for improving grape fruit firmness to meet the needs of industry development. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides the application of sorbitol in improving the firmness of grapes.

[0006] The technical solution of the present invention is as follows: Application of sorbitol in improving grape fruit firmness.

[0007] According to a preferred embodiment of the present invention, the method of application is to spray a sorbitol solution during the grape growing season.

[0008] According to a preferred embodiment of the present invention, the concentration of the sorbitol solution is 40-60 mM.

[0009] According to a preferred embodiment of the present invention, the spraying method involves spraying the entire leaf of the grape plant during the new shoot growth period and the inflorescence separation period, focusing on spraying both the upper and lower surfaces of the leaves, and spraying continuously 2 to 3 times.

[0010] More preferably, the amount of spray is such that the leaf surface is just covered with uniform droplets without dripping.

[0011] More preferably, the spraying interval is 3 to 7 days.

[0012] More preferably, the spraying method involves maintaining a distance of 30-40 cm between the sprayer and the plant.

[0013] According to a preferred embodiment of the present invention, the grape varieties include: 'Red Double Flavor', 'Muscat', 'Sunshine Rose', and 'Italian'.

[0014] Beneficial effects: 1. Significantly Improved Fruit Firmness: Extensive field trials have verified that sorbitol treatment significantly improved the fruit firmness of four grape varieties—'Red Double Flavor,' 'Muscat,' 'Sunshine Rose,' and 'Italian'—compared to the control group. During the veraison stage, the increase in fruit firmness reached 27.8%–31.3%, and this high level of firmness was maintained throughout the ripening period, effectively improving the fruit's storage and transport resistance.

[0015] 2. Comprehensive Improvement of Fruit Quality: In addition to improving fruit firmness, the method of this invention can also promote uniform coloring of some grape varieties, increase soluble solids content, and reduce titratable acid content, resulting in better fruit flavor. Simultaneously, the enhanced antioxidant capacity of the fruit can delay fruit senescence, effectively extend shelf life, and improve the overall commercial value of the grapes.

[0016] 3. Environmentally friendly, economical, and easy to promote: The sorbitol used in this invention is a natural or biodegradable substance, which is environmentally friendly and leaves no residual pollution. The preparation and application of the agent are simple, requiring no complex equipment and at a low cost. Furthermore, this method is highly compatible with conventional grape cultivation and management practices, making it easy to promote and apply in grape-growing areas, and can bring significant economic benefits to growers. Attached Figure Description

[0017] Figure 1 Figure showing the effect of sorbitol spraying on the appearance quality of 'Red Double Flavor' grapes; Figure 2 Figure showing the effect of sorbitol spraying on the appearance quality of 'Muscat' grapes. Detailed Implementation

[0018] The technical solution of the present invention will be further described below with reference to the embodiments, but the scope of protection of the present invention is not limited thereto.

[0019] Unless otherwise specified, the experimental methods used in the following examples are conventional methods; and the materials and reagents used are commercially available unless otherwise specified.

[0020] Materials and Methods 1. Experiment time and location: May to September 2024, Jinan City, Shandong Province.

[0021] 2. Variety and Plant Selection The grape varieties selected are 'Red Double Flavor', 'Muscat', 'Sunshine Rose', and 'Italian'. 'Red Double Flavor' is a hybrid of European and American grapes, characterized by early ripening, thin skin, soft and juicy flesh, and a combination of banana and rose aromas. 'Muscat' is a Eurasian variety, with a strong rose aroma, slightly soft and juicy flesh, and is very popular with consumers. 'Sunshine Rose' is also a hybrid of European and American grapes, with a relatively thin skin, firm and crisp flesh, and a rose aroma. 'Italian' is a Eurasian variety with large berries, a medium-thick skin, and crisp flesh. These varieties have high market demand, but there is room for improvement in fruit firmness under natural growing conditions, and they show good adaptability to the treatment with the agent of this invention.

[0022] Plant selection: Within the planting areas of each variety, healthy plants with consistent growth were selected by observing indicators such as plant height, stem diameter, new shoot growth, leaf color and size. Selected plants should be free from obvious pests and diseases and exhibit robust growth to ensure the consistency and comparability of subsequent treatment effects and reduce interference from individual plant differences on the experimental results.

[0023] 3. Pharmaceutical preparation and properties Preparation of Sorbitol Solution: Sorbitol is a polyol that can serve as a carbon source and osmotic regulator in plants. Weigh a certain amount of sorbitol, add an appropriate amount of distilled water, stir thoroughly to dissolve, and prepare a 50mM (approximately 10g / L) sorbitol solution. This concentration can provide sufficient energy and carbon skeleton for fruit development while maintaining intracellular osmotic pressure balance.

[0024] 4. Key Spraying Time and Operation 1) Determining the timing of spraying: Spray sorbitol solution during the new shoot growth period and the inflorescence separation period of grapevines, spraying 2-3 times consecutively, with an interval of 3-7 days between each spray. The new shoot growth period is the rapid growth stage of the vegetative organs of grapevines. At this time, the plant is more sensitive to nutrients and external stimuli. Spraying the agent can promote the absorption and translocation of nutrients by the plant, laying the foundation for subsequent reproductive growth. The inflorescence separation period is a critical period for grape inflorescence differentiation and development. Spraying during this period helps regulate the development of flower organs and ensure normal fruit setting and development.

[0025] 2) Spraying Procedure: Use a backpack electric sprayer to evenly spray the prepared sorbitol solution onto the entire leaf surface of the grapevine, focusing on both the upper and lower surfaces of the leaves. Maintain a distance of approximately 30-40 cm between the sprayer and the plant to ensure even coverage and prevent localized over- or under-concentration of the pesticide, which could negatively impact the treatment effect. Each spray should be applied until a uniform mist forms on the leaf surface without dripping.

[0026] 5. Sampling and Testing 1) Sampling Plan: Sampling will begin at the young fruit stage after pesticide application, with sampling every three weeks until the fruit matures. The young fruit stage is defined as a fruit diameter of 5-8 mm. At each sampling, 10 fruits from different locations and parts of each treated plant of each variety will be randomly selected to ensure representativeness. Simultaneously, untreated plants of the same variety and vigor will serve as a control group, and sampling will be conducted concurrently.

[0027] 2) Hardness Measurement: The hardness of the sampled fruit was measured using a GY-4 fruit hardness tester. Before measurement, the fruit skin was cleaned to remove surface impurities and bloom. Three measurement points were evenly selected at the equator of the fruit, and the average value was taken as the hardness value of the fruit. The data was recorded in detail.

[0028] 3) During the measurement process, quality indicators such as soluble solids content, titratable acid content, and fruit color were also measured simultaneously to comprehensively evaluate the impact of pesticide treatment on fruit quality. Soluble solids were measured using a handheld PAL-1 refractometer; titratable acid was measured using a 0.06 mol·L⁻¹ solution. -1 The content of NaOH was determined and expressed as tartaric acid; the content of anthocyanins was determined by pH differential method.

[0029] Example 1 1. Material preparation Select 20 healthy 'Red Double Flavor' grapevines with uniform growth and no pests or diseases, and divide them into two groups of 10 each. Prepare a 50mM (approximately 10g / L) sorbitol solution and distilled water for each group.

[0030] 2. Processing procedure On May 7 and May 12 (the period of new shoot growth and inflorescence separation), the prepared sorbitol solution was sprayed evenly on the entire leaf of the first group of grapevines using a sprayer, which was designated as the experimental group (Sor). The other group was sprayed with distilled water in the same way, which was designated as the control group (CK).

[0031] 3. Fruit sampling and testing After fruit sampling, the hardness of the fruit on each of the 10 grapevines in each group was measured using a hardness tester, and the data were recorded. The specific data are shown in Table 1.

[0032] Table 1. Changes in fruit firmness of 'Red Double Flavor' variety after sorbitol solution treatment

[0033] Note: * in the table indicates a significant difference, P<0.05.

[0034] The soluble solids content, titratable acid content, and anthocyanin content of mature grape berries were simultaneously determined, and the results are shown in Table 2.

[0035] Table 2. Content of soluble solids, titratable acid and anthocyanins in the fruit of the 'Hongshuangwei' variety at maturity.

[0036] Note: * in the table indicates a significant difference, P<0.05.

[0037] 4. Results Analysis The results of the firmness changes are shown in Table 1. After spraying 'Red Double Flavor' grapes with sorbitol solution, the firmness of the fruit increased to varying degrees as the fruit grew, especially during the color-changing period (July 16th to August 6th), when the increase in firmness was particularly significant. Compared with the control group, the increase in fruit firmness ranged from 27.8% to 31.3%, significantly improving the quality and storage and transportation resistance of the grapes. As shown in Table 2, compared with the control group, the soluble solids and anthocyanin content of grapes treated with sorbitol were significantly increased, while the titratable acid content was significantly decreased. This indicates that spraying sorbitol can also improve the appearance quality of 'Red Double Flavor' grapes, enhance their taste and flavor, and, as an antioxidant, increasing the content of anthocyanins can also improve the nutritional value of the grapes. Figure 1The effect of sorbitol spraying on the appearance quality of 'Red Double Flavor' grapes shows that the color of the grapes was significantly improved after spraying.

[0038] Example 2 1. Material preparation Twenty 'Muscat' grapevines of uniform vigor were selected and randomly divided into two groups of ten vines each. A 50mM (approximately 10g / L) sorbitol solution and distilled water were prepared for each group.

[0039] 2. Processing procedure On May 7 and May 12 (the period of new shoot growth and inflorescence separation), the prepared sorbitol solution was evenly sprayed onto the entire leaf of the first group of grapevines using a sprayer, which was designated as the experimental group (Sor). The other group was sprayed with distilled water in the same way, which was designated as the control group (CK).

[0040] 3. Fruit sampling and testing Fruit firmness was measured after sampling, and the specific data are shown in Table 3.

[0041] Table 3. Changes in fruit firmness of 'Muscat' cultivar after sorbitol solution treatment

[0042] Note: * in the table indicates a significant difference, P<0.05.

[0043] The soluble solids content, titratable acid content, and anthocyanin content of mature grape berries were simultaneously determined, and the results are shown in Table 4.

[0044] Table 4. Content of soluble solids, titratable acid and anthocyanins in mature 'Muscat' cultivar fruits

[0045] Note: * in the table indicates a significant difference, P<0.05.

[0046] 4. Results Analysis The statistical analysis results of the measurement data are shown in Tables 3 and 4. The effect of sorbitol spraying on the appearance quality of grapes is as follows: Figure 2 As shown in the figure. The results indicated that spraying 'Muscat' grapes with sorbitol solution improved fruit firmness to varying degrees. Compared with the untreated control group, the firmness increased by 32.5% after sorbitol treatment on August 27th, demonstrating a significant improvement in fruit firmness. Compared with the control group, the sorbitol-treated grapes showed significantly increased soluble solids and anthocyanin content, and significantly decreased titratable acid content, indicating that sorbitol treatment can also improve the taste, flavor, appearance, and nutritional value of 'Muscat' grapes.

[0047] Example 3 1. Material preparation Similarly, 20 'Sunshine Rose' grapevines were selected and divided into 2 groups of 10 vines each. A 50mM (approximately 10g / L) sorbitol solution and distilled water were prepared for each group.

[0048] 2. Processing procedure On May 7 and May 12 (the period of new shoot growth and inflorescence separation), the prepared sorbitol solution was evenly sprayed onto the entire leaf of the first group of grapevines using a sprayer, which was designated as the experimental group (Sor). The other group was sprayed with distilled water in the same way, which was designated as the control group (CK).

[0049] 3. Fruit sampling and testing Table 5. Changes in fruit firmness of 'Sunshine Rose' variety after sorbitol solution treatment

[0050] Note: * in the table indicates a significant difference, P<0.05.

[0051] The results of the determination of soluble solids content and titratable acid content of mature grape berries are shown in Table 6.

[0052] Table 6. Soluble solids and titratable acid content in mature 'Sunshine Rose' varietal fruit

[0053] Note: * in the table indicates a significant difference, P<0.05.

[0054] 4. Results Analysis The statistical analysis results of the measurement data are shown in Tables 5 and 6. After spraying sorbitol solution on 'Sunshine Rose' grapes, the fruit firmness increased to varying degrees with changes in fruit growth stages, with the last test showing an increase of 11.0%. Compared with the control group, the soluble solids content of grapes treated with sorbitol was significantly increased, and the titratable acid content was significantly decreased, indicating that spraying sorbitol can also improve the fruit quality of 'Sunshine Rose' grapes.

[0055] Example 4 1. Material preparation Twenty healthy 'Italian' grapevines with uniform growth and free from pests and diseases were selected and divided into two groups of 10 vines each. A 50mM (approximately 10g / L) sorbitol solution and distilled water were prepared for each group.

[0056] 2. Processing procedure On May 7 and May 12 (the period of new shoot growth and inflorescence separation), the prepared sorbitol solution was evenly sprayed onto the entire leaf of the first group of grapevines using a sprayer, which was designated as the experimental group (Sor). The other group was sprayed with distilled water in the same way, which was designated as the control group (CK).

[0057] 3. Fruit sampling and testing Based on Example 1, grape firmness was measured once more. Specific data are shown in Table 7.

[0058] Table 7. Changes in fruit firmness of the 'Italian' variety after sorbitol solution treatment.

[0059] Note: * in the table indicates a significant difference, P<0.05.

[0060] The results of the determination of soluble solids content and titratable acid content of mature grape berries are shown in Table 8.

[0061] Table 8. Soluble solids and titratable acid content in the fruit of the 'Italian' variety at maturity.

[0062] Note: * in the table indicates a significant difference, P<0.05.

[0063] 4. Results Analysis The statistical analysis results of the measurement data are shown in Tables 7 and 8. The results show that after spraying sorbitol solution on 'Italian' grapes, the fruit firmness increased to varying degrees with the changes in fruit growth stages, with the last test showing an increase of 9.7%. Compared with the control group, the titratable acid content of grapes treated with sorbitol was significantly reduced, indicating that spraying sorbitol can also improve the taste and flavor of 'Italian' grapes.

[0064] Based on the four examples, it was found that spraying sorbitol solution improved the firmness of all four grape varieties. The firmness of 'Red Double Flavor' and 'Muscat' grapes improved more significantly, while the firmness of 'Sunshine Rose' and 'Italian' grapes improved relatively less.

[0065] In addition, spraying sorbitol can also optimize the quality of some grape varieties, reduce acidity, increase soluble solids content, and improve taste; promote anthocyanin synthesis, enhance fruit color vibrancy and antioxidant capacity, and improve nutritional value.

[0066] In terms of variety validation, the experiment selected representative grape varieties such as 'Red Double Flavor' (early-maturing European-American hybrid), 'Muscat' (classic Eurasian variety), 'Sunshine Rose' (classic European-American hybrid), and 'Italian' (late-maturing Eurasian variety), covering different flavor types, cultivation regions, and market positioning among table grapes. The results showed that this method significantly improved fruit firmness in all varieties, effectively extending the shelf life of grapes in the field, providing a practical solution to the long-standing problems of fruit softening and poor storage and transportation in the grape industry. From a feasibility perspective, sorbitol is a safe and environmentally friendly substance with controllable costs. Spraying is simple and easy, requiring no complex equipment or high labor costs, making it highly suitable for the production needs of large-scale vineyards. The inventors hope to accelerate the industrialization of this technology through patent protection mechanisms, helping the grape industry achieve both quality upgrades and economic benefits, and promoting the industry's transformation towards a green and efficient modern production model.

Claims

1. Application of sorbitol in improving grape fruit firmness.

2. The application as described in claim 1, characterized in that, The method described involves spraying a sorbitol solution during the grape growing season.

3. The application as described in claim 2, characterized in that, The concentration of the sorbitol solution is 40~60mM.

4. The application as described in claim 2, characterized in that, The spraying method involves spraying the entire plant's leaves during the new shoot growth period and the inflorescence separation period, focusing on both the upper and lower surfaces of the leaves, and spraying 2-3 times consecutively.

5. The application as described in claim 4, characterized in that, The amount of spray used is such that it just forms a uniform mist on the leaf surface without dripping.

6. The application as described in claim 4, characterized in that, The spraying interval is 3 to 7 days.

7. The application as described in claim 4, characterized in that, The spraying method involves maintaining a distance of 30-40 cm between the sprayer and the plant.

8. The application as described in claim 1, characterized in that, The grape varieties mentioned include: 'Red Double Flavor', 'Muscat', 'Sunshine Rose', and 'Italian'.

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