JPH05115223A - Modification of cold-resistant leaf vegetables - Google Patents

Abstract

PURPOSE:To increase the sugar content of the leaf of a cold-resistant leaf vegetable, to soften the texture and to improve the taste of the vegetable by forming frost on the surface of the vegetable on a field with ice-nucleation bacteria. CONSTITUTION:Ice-nucleation bacteria are attached to the surface of a cold- resistant leaf vegetable grown on a field such as NOZAWANA (a kind of herb mustard), spinach and Welsh onion. The vegetable is exposed to a temperature near the optimum ice-nucleation temperature of the bacteria to effect the formation of frost on the surface of the leaf to enable the production of delicious cold-resistant leaf vegetable meeting the shipping time independent of the climate and the configuration of the ground. The application of the ice-nucleation bacteria to the leaf surface is preferably carried out by spraying a suspension of the bacteria.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for improving the taste of leafy vegetables such as Nozawana, Yukina, spinach, and green onions having cold resistance.

[0002]

2. Description of the Related Art For example, pickled Nozawana pickles have been used as processed vegetables for wintering in Shinshu, where the winter is severe, but in recent years, demand has expanded nationwide as their unique flavor became known. is there. Nozawana-zuke pickles Nozawana-zuke in a state like this when it is pickled and frosted once or twice and then salted to give it a slight sweetness and consistency. It is favored as a pickled "or" or "sticky" pickle. In this way, by attaching frost to the leaf surface, the leaf shows a defense reaction against cold, stores sugars in the cells, increases the viscosity of the cell fluid, and causes a peculiar taste. Not only Nozawana, but also green onions, snow vegetables,
It is well known for its cold-resistant leafy vegetables such as spinach.

However, due to the adjustment of the shipping time, it is necessary to harvest early, or even if the nighttime temperature drops to a level sufficient for frosting, frost is formed in some fields and In some fields, frost does not form, and immediately after frosting, leaves have a bitter taste, but after frost formation, the above-mentioned paste may appear after a certain period of time. However, there are inconveniences such as having to concentrate at a certain time during the harvest time, and when it is exposed to frost or exposed to unnecessarily cold air, the tissue on the surface is necrotic and the surface layer peels off. However, it is actually difficult to mass-produce “Nozawana pickles with paste” to a certain extent in a short period of time, regardless of whether they are for personal use or not. Is.

[0004]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and in a field where the nighttime temperature reaches −2 to −3 ° C. or lower, it can be optionally protected from cold. The purpose of the present invention is to improve the taste of edible leafy vegetables by appropriately forming frost.

[0005]

In general, water is said to freeze at around 0 ° C. under atmospheric pressure, but in reality, a supercooling phenomenon is likely to occur, and particularly in the case of fine water droplets (about 10 μl). Is extremely hard to freeze, and the freezing temperature of fine water droplets reaches to -39 ° C. However, it has been known that such fine water droplets also freeze at a higher temperature due to the presence of ice crystal nuclei such as silver impregnation, but in recent years, the phenomenon of frost on the leaves of plants has also been reported. Some bacteria adhering to the surface, such as those belonging to the genus Pseudomonas or Erwinia, were found to have ice crystal nuclei in the finely condensed water generated on the leaf surface as the temperature decreased. Then, it became known that it caused freezing.

[0006] The gist of the present invention is to use a so-called ice nucleus-activating bacterium having such an action, and apply this to cold-tolerant leafy vegetables that grow in fields, such as in cultivation greenhouses and open fields, by appropriate means. Attached, by exposing the leaf vegetables near the optimum temperature in the ice nucleus formation of the ice nucleus-activating bacteria, frost is formed at a temperature at which the leaf tissue is not necrotic, to the plant,
Characterized by causing a defense reaction against the cold,
It is a method of modifying cold-resistant leafy vegetables. The temperature at which the leaf tissue does not necrosis varies depending on the cold resistance temperature of each leaf vegetable, but specifically, if it is a temperature around −2 to −3 ° C., in most cold resistant leaf vegetables, damage due to cold air will be caused. Never generated.

[0007] Pseudomonas fluorescens, Pseudomnas syr can be used as ice nuclei-activating bacteria for such purposes.
imgae ， Pseudomnas viridiflava, Erwinia herbicola,
Erwinia ananas, Erwinia stewartii, Erwinia uredobo
ra etc. are known. These ice nucleus-activating bacteria are appropriately used according to the degree of cold tolerance of the plant, but generally, in order to cause a defense reaction that improves the taste of cold-resistant leafy vegetables, it is -2- to- The range of 3 ° C. is most preferable, and particularly in the case of Nozawana, the lower the temperature, the more noticeable the discoloration of leaves and the partial necrosis of tissues may occur.

As a substance having such a relatively high ice nucleation temperature, Xanthomonas t found by the present inventor
ranslucens (IFO 13559) and Pseudomnas syrimgae (IF
O 3310), Erwinia herbicola (IFO 12686), and Microtechnical Research Institute No. 10186 ice nucleus-activating bacteria.

Such ice-nucleus-activating bacteria may be used in a viable state, or may be sterilized without deactivating ice-nucleus activity, for example, irradiating ultraviolet rays to sterilize. The freeze-dried ice nucleating bacteria were freeze-dried with the culture solution, or the method of Obata et al. (Journal of Fermentat
ion and Bioengineering, Vol.70, No.5, 308-312p199
Based on (0), substances having ice nucleation activity separated from ice nucleation active bacteria by a surfactant may be used.

As a method for adhering to plants, these may be suspended in an appropriate dispersion medium and sprayed on the leaves by a sprayer, or an extender powder (eg starch).
May be sprayed with. The concentration used is 10 ³ to 10 ⁸ ce
lls / ml is sufficient to produce the desired effect.

[0011]

[Effect] According to the method of the present application, vegetables with good taste can be produced at the time of shipment, and even in places where frost formation was difficult due to the conventional climate and topography, the taste is soft and tasty. Leaf vegetables can be obtained. Moreover, since the ice-nucleus-active bacteria used have naturally existed in the past and had the same function, there is no danger of toxicity or the like at all. Examples will be given below.

[0012]

Example 1 Step A. Preparation of Ice Nucleus-Activating Bacteria Ice-nucleating bacteria (Microtechnological Research Institute No. 10186) were trypti
Using case soy medium, in a 5 liter jar incubator,
After shaking culture at 18 ° C for 24 hours, the culture solution is centrifuged to separate ice-nuclei-active bacteria and washed with phosphate buffer (pH 7.0), and then the absorbance is adjusted to 0.1 (OD660nm). After adjustment and centrifugation, the supernatant was removed and diluted with purified water to adjust the concentration to 1.8 × 10 ⁸ cells / ml to prepare a spray solution.

Step B. Modification by frost formation Nozawana growing in a greenhouse and having an average plant height of about 50 cm was divided into an experimental section and a control section, and the experimental section was obtained in the above step A. 50 ml of spray liquid per 1 m ²
Was sprayed by the atomizer. On the other hand, in the control area,
Purified water was sprayed at the same rate as the experimental plot. After the leaf surface was naturally dried, the temperature in the greenhouse was lowered to -3 ° C at a rate of 0.5 ° C / hr by a refrigerator, and the frosted state was maintained at about -3 ° C for 3 hours. Was observed. As a result, frost formation was clearly observed on the surface of Nozawana in the experimental plot, but no frost formation was observed in the control plot.

Nozawana in the experimental zone has 4 leaf tips.
After ~ 5 days, the color began to change to reddish brown, and after 5 days, the harvested product was salted with 3% sodium chloride. No discoloration was observed in Nozawana in the control area, but they were similarly harvested and salted. When comparing the tastes of both,
Nozawana pickles in the experimental area are softer than those in the control area,
In terms of sweetness and paste (viscosity), the results were superior, and a clear difference was felt.

Claims (3)

[Claims] 1. A method for reforming cold-resistant leafy vegetables, which comprises causing ice-nucleus-active bacteria to adhere to the surface of cold-resistant leafy vegetables that grow in a field, thereby causing frost to form on the surface of the cold-resistant leafy vegetables. 2. The method according to claim 1, wherein the ice-nucleating bacteria are attached to the leaves by spraying a suspension of the ice-nucleating bacteria on the leaves. 3. A suspension of ice-nucleating bacteria is Xanthomonas tr.
anslucens IFO 13559, Pseudomonas IFO 3310, Pseudom
The method for reforming according to claim 2, which is a suspension of ice-nucleating bacteria containing at least one of onas IFO 12686.