Method for growing citrus plants

Abstract

To provide a method for efficiently cultivating higher quality citrus fruits.SOLUTION: A cultivation method of the present invention is characterized by feeding 3 to 15 kg of soy sauce cake per citrus plant as fertilizer. Furthermore, soy sauce cake is fed only when the fruit is ripening. Not only can this method produce higher quality fruit from citrus plants, but it can also be used to process the fruit obtained by this method into food by well-known means, enabling the production of products with better flavor and higher added value than before.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a cultivation method. More specifically, it relates to a cultivation method for citrus plants.

Background Art

[0002] The citrus genus is a genus of the Rutaceae family. Its scientific name is Citrus, and its fruits are widely used for food and are widely cultivated in the country. In particular, in Japan, the production of Satsuma mandarin, which is generally called "mikan", is prosperous, and the harvest amount reaches 147,800 t. Satsuma mandarin is popular as a domestic fruit and is also exported. However, compared with the 1980s, the domestic consumption and export volume of Satsuma mandarin in Japan have decreased, and the provision of more attractive fruits of citrus plants is desired.

Summary of the Invention

Problems to be Solved by the Invention

[0003] Therefore, an object of the present invention is to provide a method capable of efficiently cultivating fruits of higher-quality citrus plants.

[0004] To achieve the above object, the present invention comprises a cultivation method characterized by applying soy sauce cake only during the fruit ripening period of citrus plants or from September to November. Further, it is preferable that the amount of soy sauce cake applied is 3 to 15 kg / tree.

[0005] Furthermore, the present invention comprises a cultivation method characterized by applying 3 to 15 kg / tree of soy sauce cake as a fertilizer to citrus plants. Also, it is preferable to apply soy sauce cake only during the fruit ripening period.

[0006] In previous studies on mandarins, there are reports that the sugar content increased by 1 to 2 degrees Brix by water control through furrow cutting cultivation or film mulch cultivation (Takatsuki, 1991), and reports that the sugar content (Brix) increased from 8.33 to 8.73 at 2-fold dilution and 9.01 at 10-fold dilution by applying deep ocean water.

[0007] It has also been reported that as the amount of nitrogen applied increased, the sugar content, total nitrogen, and amino nitrogen in the juice components increased, and the free amino acids arginine, aspartic acid, serine fraction, proline, and alanine increased, accounting for 70-90% of the total free amino acids.

[0008] On the other hand, soy sauce, a typical Japanese seasoning, originated in Yuasa Town, Wakayama Prefecture, and the industry is still thriving nationwide. In 2021, about 700,000 kl of soy sauce was produced nationwide. Soy sauce cake is produced as a by-product of soy sauce production (a by-product produced when squeezing mash). Soy sauce cake is discharged in a relatively large amount, accounting for 20-30% of the weight of soy sauce raw materials. The composition of soy sauce cake has been reported to be 37.7% crude protein, 21.4% soluble non-nitrogenous matter, 14.8% crude fiber, 14.2% ash, 11.9% crude lipids, etc. Because of its high protein content, soy sauce cake is considered suitable for feed and fertilizer, but because it has a high salt concentration, additional processes such as desalination processing are required. For this reason, there are mixed fertilizers that use soy sauce cake, but the amount of soy sauce cake mixed is very small, and it is adjusted so that the soil does not become highly salty. Furthermore, given that other fertilizers are available at low cost, its use is limited as it is not profitable.

[0009] Therefore, the present inventors have focused on the possibility that soy sauce cake, which is rich in various amino acids as a nitrogen source but has a high salt concentration, can be used as a fertilizer to improve the sugar content, umami, and flavor of the fruits of citrus plants. They have discovered that the application of soy sauce cake has a favorable effect on the flavor of the fruits of citrus plants, and that the application time and amount are characteristic, and have completed the present invention. In particular, it is important to know that it is suitable to apply soy sauce cake during the fruit maturation stage, rather than during the fruit enlargement stage when the fruits grow larger, that the effect is more pronounced with an appropriate application amount, and that soy sauce cake can be used without the need for mixing with other materials or desalination treatment.

[0010] In the present application, the genus Citrus means those belonging to the genus Citrus in the family Rutaceae, order Sapindales. Specifically, it includes iyo-kan (Citrus iyo), unshu-mikan (C. unshiu), orange (C. sinensis), kabosu (C. sphaerocarpa), kishu-mikan (C. kinokuni), chinotto (C. chinotto), grapefruit (C. X paradisi), kouji (C. leiocarpa), sanbokan (C. sulcata), citron (C. medica), jabara (C. jabara), sudachi (C. sudachi), daidai (C. aurantium), tachibana (C. tachibana), tangor (C. reticulata), natsudaidai (natsumikan, C. natsudaidai), hassaku (C. hassaku), hanayu (C. hanayu), hyuga-natsu (C. tamurana), hirami lemon (C. depressa), buntan (C. maxima), ponkan (mandarin orange, C. reticulata), yuzu (C. junos), lime (C. aurantifolia), lemon (C. limon).

[0011] Among these, unshu-mikan (Wenzhou mandarin, scientific name: C. unshiu) is particularly preferred, and it is also preferably applicable to those belonging to the genus Citrus that can be harvested within a year, such as kishu-mikan, chinotto, kouji, ponkan (mandarin orange), etc., which are similar in properties to unshu-mikan.

[0012] The soy sauce cake in the present invention means the pressed residue generated in the soy sauce manufacturing process, contains at least salt and protein, and is regardless of the production area and the type of soy sauce. The present invention enables the efficient and effective utilization of soy sauce cake. Regarding the application method, it is only necessary to place the soy sauce cake as it is around the tree in an appropriate size, and there is no particular need to embed it in the ground or make it into powder. Although the application method is not limited, in terms of the fact that the effect can be recognized even when administered as the soy sauce cake without mixing and reacting with other fertilizers as an individual, it is also advantageous in solving the problems in the utilization of soy sauce cake. From application to harvest, although not particularly limited, it is desirable to leave at least two weeks in between.

[0013] The fruit ripening period is the time after the fruit enlargement period (also called the fruit growth period) when the fruit grows large at a high pace, during which the fruit enlargement slows down and the coloring suitable for harvesting becomes darker. According to the Guidelines for Environmentally Friendly Agricultural Cultivation Techniques (Wakayama Prefecture), among the germination period, leaf expansion period, flowering period, and ripening period, it means the ripening period. In the case of Satsuma mandarin cultivated in Japan, it generally refers to September to November, and harvesting is usually carried out around October to December. Also, considering that the flowering is in May, it can be said to be a period of about 4 to 6 months (about 120 to 200 days) from the full bloom of flowering.

[0014] The fruit of the citrus plant cultivated by the method of the present invention can be directly consumed as a high-quality fruit, for example, as a mandarin. Therefore, the present invention is also a method for cultivating the fruit of the citrus plant.

[0015] Furthermore, by processing the fruit of the citrus plant obtained by the present invention by known means into food products, it becomes possible to efficiently produce high-added-value products with better flavor than before. Although not limited to the commodity form, for example, canned fruit, bottled fruit, jam, marmalade, fruit butter, pickled fruit, dried fruit, frozen fruit food, beverages, and other foods mixed with processed fruit can be mentioned. Such processed foods are also suitable for branding and overseas expansion.

Brief Description of the Drawings

[0016]

Figure 1

Figure 2

Embodiments for Carrying Out the Invention

[0017] Experiment 1: Soy sauce cake was applied to mandarin trees, and its effect was verified. 1. Experimental Materials For the experimental mandarin orange trees, mandarin orange trees (about 60 years old) grown in the open field at the Yuasa Farm attached to Kinki University were used.

[0018] 2. Application of soy sauce cake Application and cultivation management to mandarin orange trees; Plate-shaped soy sauce cake crushed by a crusher (chipper) was applied once around the mandarin orange trees at a rate of 5 kg / 8 m 2 / tree or 10 kg / 8 m 2 / tree. The management of mandarin orange trees after the application of soy sauce cake was carried out in the same way as conventional cultivation. Regarding the application time and application amount, it is as follows.

[0019] 1) Examination due to difference in application time; Among 43 mandarin orange trees, 10 trees were cultivated by the conventional method as control trees, and soy sauce cake was applied to the remaining 33 mandarin orange trees in addition to the conventional method. On June 9, July 13, September 17, and November 16, 2019, soy sauce cake crushed separately each time was applied at a rate of 10 kg / tree (not continuously applied, but applied once for each group at different times). More specifically, full bloom date (5 / 13) → soy sauce cake application in June (6 / 9, 28 days after full bloom) → soy sauce cake application in July (7 / 13, 62 days after full bloom) → soy sauce cake application in September (9 / 17, 128 days after full bloom) → soy sauce cake application in November (11 / 16, 188 days after full bloom) → harvest (12 / 4, 206 days after full bloom).

[0020] 2) Examination due to difference in application amount; Among 15 mandarin orange trees, 5 trees were cultivated by the conventional method as control trees, and soy sauce cake was applied to the remaining 10 mandarin orange trees in addition to the conventional method. The application to mandarin orange trees was carried out by applying 5 kg / tree or 10 kg / tree of soy sauce cake crushed on October 12, 2022. More specifically, full bloom date (5 / 8) → soy sauce cake application in October (10 / 12, 158 days after full bloom) → harvest (12 / 10, 217 days after full bloom).

[0021] 3. Sampling of mandarin orange fruits The harvest of the mandarin fruits was carried out by harvesting all the fruits borne on one mandarin tree. The harvest time was December 4, 2019 in the case of 2-1) and December 11, 2022 in the case of 2-2).

[0022] 4. Preparation of juice samples From the harvested mandarin fruits, fruits of M size (fruit transverse diameter 61 - 67 mm) were randomly selected as test samples. As the preparation of the samples for item 5. below, the fruits for which the sugar content and acidity were measured were cut across, and the juice was squeezed using a fruit juice extractor, and the juice was used as a sample for GC-MS analysis. Separately from the samples for item 5. measurement, 5 mandarin fruits were randomly selected, and the juice was collected from them and used as a sample for item 6. taste test.

[0023] 5. Measurement of amino acid and sugar contents in mandarin fruits using GC-MS 1) Preparation (extraction and derivatization) of GC-MS analysis samples 2 ml of the juice obtained in 4. was aliquoted and stored frozen until measurement. At the time of GC-MS measurement, the frozen juice was thawed, and the obtained mandarin juice was diluted 10-fold with distilled water. 1,000 μl of a mixed solution (MeOH / H2O / CHCl3 = 5:2:2) was added to the diluted solution and mixed well with a vortex mixer. 60 μl of a 0.2 mg / ml ribitol aqueous solution was added as an internal standard, and the mixture was shaken at 37 °C, 1,200 rpm for 30 minutes using a heating shaker. After shaking, centrifugation was performed at 16,000 g, 4 °C for 3 minutes, and 900 μl of the supernatant was collected. The collected supernatant was concentrated at room temperature for 2 hours using a centrifugal concentrator. After concentration, it was frozen with liquid nitrogen and then freeze-dried overnight to obtain an extract. 100 μl of a 20 mg / ml methoxyamine hydrochloride pyridine solution was added to the extract and redissolved, and the mixture was shaken at 30 °C, 1,200 rpm for 90 minutes using a heating shaker. After adding 50 μl of N-methyl-N-trimethylsilyl-trifluoroacetamide (MSTFA), the mixture was shaken at 37 °C, 1,200 rpm for 30 minutes using a heating shaker. Then, the entire solution was transferred to a vial for GC-MS in its entirety and used as a GC-MS analysis sample.

[0024] 2) GC-MS analysis The adjusted GC-MS analysis sample was analyzed using GCMS-QP2010 (SHIMAZU). The column used was CpSil8 CB-MS (length: 23.5 m, inner diameter: 0.25 mm, film thickness: 0.25 μm), and the carrier gas was He. The sample was injected at 1 μl with a vaporization chamber temperature of 230°C and a split ratio of 50:1. The column temperature was held at 80°C for 2 minutes, then linearly heated at 15°C / min and held at 280°C for 10 minutes for analysis. Mass spectrometry was performed using the Electron Ionization (EI) method, scanning the range of m / z = 85 - 500 at an ion temperature of 200°C and an interface temperature of 250°C for analysis.

[0025] Principal component analysis (PCA) was performed on the peak list obtained from the chromatogram data of GC-MS analysis using MS-DIAL, a universal tool for non-target metabolome analysis. At that time, scaling was performed with pareto scaling, corrected with ribitol as an internal standard, and data analysis was carried out. As a result, 151 peaks were detected, and 124 of them were identified. The results of the principal component analysis (PCA) are shown in Figure 1. First, when considering the application time, the components of the primary metabolites of each sample were mainly classified into two clusters. The large cluster formed in the upper right center of the score plot included the control, June application, and July application. The other cluster formed in the upper left of the score plot included the September application and November application.

[0026] As shown in Fig. 1, when soy sauce cake was applied to mandarin orange trees at a rate of 10 kg / tree in June or July (during the fruit enlargement period), no difference was observed in the fruit internal component composition compared to the control group (conventional cultivation group). On the other hand, when soy sauce cake was applied in September or October when the fruits were ripening (fruit ripening period), the component composition was different from that of the control group. When soy sauce cake was applied during the fruit ripening period, as shown in Fig. 2, it was found that rare sugars such as trehalose, D-allose, and D-talose increased. Therefore, it was found that applying soy sauce cake during the fruit ripening period (September - November) was more effective than during the fruit enlargement period (June - August).

[0027] 6. Taste test After the fruits were harvested, a taste test was conducted on 48 people under blind conditions. The taste evaluation method was examined using umami, sweetness, sourness, and deliciousness as indicators. Regarding the evaluation method, fruits different from those of M size (fruit transverse diameter 61 - 67 mm) used in 4. were cut horizontally, and the juice was squeezed using a fruit juice extractor for fruits, and the juice was used as the test sample. The test sample was drunk, and the three groups (control, 5 kg application, 10 kg application) were ranked from the top, and the one with the highest evaluation in each item was scored 3 points, and the following were scored 2 points and 1 point in order.

[0028] 8. Statistical processing The results of the taste test were expressed as the mean ± standard error, and the Bonferroni / Dunn multiple comparison test (Multiple range test) was used for statistical processing.

[0029] 9. Results It was examined whether the change in the components contained in mandarin orange fruits due to soy sauce cake affected the taste (Table 1). When a taste test was conducted on mandarin orange fruits to which soy sauce cake was applied on October 12, 2022, and harvested on December 11 of the same year, the scores of "umami", "sweetness", "sourness", and overall "deliciousness" of those to which 5 kg of soy sauce cake was applied were significantly higher than those of the control group. On the other hand, for the 10 kg application, "sourness" was significantly higher than that of the fruits in the control group, and "deliciousness" was also superior and higher than that of the control group. Considering the significant effect of applying 5 kg of soy sauce cake, it is assumed that using at least 3 kg or more will improve the deliciousness.

[0030]

Table 1

[0031] From this, it was found that the change in the components contained in mandarin fruits due to soy sauce meal led to deliciousness.

[0032] Experiment 2: Soy sauce meal was applied to mandarin trees to verify its effects. 1. Experimental materials Twenty-five Satsuma mandarin trees (about 50 years old) in the Yuasa Farm of Kinki University were used for the test.

[0033] 2. Test method Of the 25 mandarin trees, 5 were used as control trees and cultivated by the conventional method, and the remaining 20 mandarin trees were applied with soy sauce meal in addition to the conventional method. On June 27 and November 14, 2020, the ground soy sauce meal was applied at a rate of 10 kg / 8 m 2 / tree or 20 kg / 8 m 2 / tree around the mandarin trees. Subsequently, the fruits were harvested on December 5 and 6.

[0034] After the fruit harvest, a taste test was conducted on 10 people in the field under blind conditions. For the taste evaluation method, richness, sweetness, sourness, and deliciousness were used as indicators. Regarding the evaluation method, fruits of M size (fruit transverse diameter 61 - 67 mm) were cut horizontally, and the juice was squeezed using a fruit juicer for the test subjects. After drinking the test subjects, they were ranked in 5 groups from the highest, and the one with the highest evaluation in each item was scored 5 points, and the following were scored 4 points in order.

[0035] For the quality inspection, 5 fruits of M size were collected from each plot of mandarin trees, and the fruit weight, sugar content, and acidity were measured using a fruit selector (Kubota Corporation). The experimental results were expressed as the mean ± standard error, and the Bonferroni / Dunn multiple comparison test (Multiple range test) was used for statistical processing.

[0036] 3. Results and Discussion The appearance of mandarin orange trees at the time of harvest in the control plot and the applied plot was observed comparatively. Even when 10 kg or 20 kg of soy sauce meal was applied once to the mandarin orange trees, no change in appearance was observed before harvest. Also, no morphological changes (salt damage) such as the tree withering or the leaves turning yellow were seen.

[0037] Next, a taste test of the obtained fruits was conducted. When soy sauce meal was applied at a rate of 10 kg / tree in November, an evaluation that it was generally felt to be more delicious than the control group was obtained (Table 2). On the other hand, the fruits applied with 20 kg / tree in June and November had lower umami and sweetness.

[0038]

Table 2

[0039] Next, the fruit sugar content and acidity, which are objective indicators for evaluating the deliciousness (quality) of mandarin oranges, were measured (Table 3). For the measurement, only M-sized fruits were used in the experiment for the purpose of excluding the influence on the fruit sugar content. As shown in Table 2, the sugar content, which is an index of sweetness in mandarin orange fruits, slightly increased when applied at 10 kg / tree in November, but did not increase when applied at 10 kg / tree in June. Furthermore, when the application rate was increased from 10 kg to 20 kg, the sugar content decreased in the June application plot. Also, no significant difference was observed in the acidity for each test plot.

[0040]

Table 3

[0041] Fruit weight, sugar content and acidity of mandarin orange fruits by application of soy sauce meal In the taste test conducted under blind conditions, most people evaluated the mandarins with 10 kg of soy sauce meal applied per tree in November as "delicious". Furthermore, when measuring the sugar content and acidity, which are objective indicators of the sweetness and sourness of mandarin fruits, the sugar content decreased with an application rate of 20 kg per tree. Therefore, at the set application rate of soy sauce meal (20 kg per tree) in this study, there is a possibility of over-application. Also, when combined with Experiment 1, this result suggests an improvement in some flavor that cannot be measured only by criteria such as sugar content and sourness, and it can be said that it enables the provision of more attractive mandarins.

[0042] Furthermore, in view of the experimental results, since the suitable application period is the fruit ripening stage and an application rate of 5 kg has sufficient effect, the suitable application rate is considered to be 3 to 15 kg per tree. Also, this finding is presumed to be effective in the genus Citrus that is similar in properties to Satsuma mandarin. By applying soy sauce meal, further processing is not required and efficient effective utilization can be achieved. Moreover, different from the past, it is possible to provide delicious and attractive Citrus fruits that cannot be measured only by criteria such as sugar content and acidity.

[0043] Furthermore, by processing the fruits of the Citrus plant obtained by the present invention by known means into food products, it becomes possible to efficiently produce high-value-added products with better flavor than before.

Claims

1. A cultivation method characterized by applying soy sauce meal only during the fruit ripening period of citrus plants.

2. The cultivation method according to Claim 1, characterized in that the citrus plant is Satsuma mandarin.

3. The cultivation method according to Claim 2, characterized in that the amount of soy sauce meal applied is 3 to 15 kg per plant.

4. A cultivation method characterized by applying 3 to 15 kg of soy sauce meal per plant to citrus plants as fertilizer.

5. The cultivation method according to Claim 4, characterized in that the citrus plant is Satsuma mandarin.

6. The cultivation method according to Claim 5, characterized by applying soy sauce meal only during the fruit ripening period.

7. A cultivation method characterized by applying soy sauce meal to Satsuma mandarin trees only during the period from September to November.

8. The cultivation method according to Claim 5, characterized in that the amount of soy sauce meal applied is 3 to 15 kg per plant.

9. A method for manufacturing processed food, characterized by processing the fruits of plants cultivated by the cultivation methods of Claims 1 to 8.

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