Method for producing frozen primary processed vegetables, and frozen primary processed vegetables

Abstract

The present invention provides a novel method for producing frozen primary processed vegetables and frozen primary processed vegetables, which have a moderate hardness that allows them to be chewed without being too hard or too soft even when eaten in a frozen state, maintain a pleasant chewiness, and have reduced bitterness and grassy taste, while retaining the original flavor of the vegetables. [Solution] A method for producing frozen primary processed vegetables, and frozen primary processed vegetables, comprising impregnating vegetables with a sugar aqueous solution containing a small amount of a specific organic acid and a high concentration of sugars, and then freezing them.

Description

[Technical Field]

[0001] This invention relates to a novel method for producing frozen primary processed vegetables that can be eaten while frozen, and to frozen primary processed vegetables. More specifically, it relates to a novel method for producing frozen primary processed vegetables and to frozen primary processed vegetables that, even when eaten while frozen, have a moderate firmness that is neither too hard nor too soft, allowing for easy chewing, maintain a pleasant chewiness, and have reduced bitterness and grassy taste, while retaining the original flavor of the vegetables. [Background technology]

[0002] Various methods for producing frozen primary processed vegetables have been proposed. Most of these methods address the issues of syneresis (water separation) after thawing, which occurs when ice crystals formed during freezing destroy the cell walls of vegetables, or the reduction in yield due to syneresis, or the softening of vegetables after thawing due to freezing, and thus improve their suitability for cooking. For example, Japanese Patent Publication No. 2021-145580 (Patent Document 1) proposes using reduced starch syrup having a predetermined sugar composition as a modifying agent to improve yield and texture after freezing and thawing.

[0003] On the other hand, in recent years, the average annual temperature has been rising due to global warming, and health consciousness has been increasing with the advancement of an aging society. Under these circumstances, there is a need for the emergence of frozen, pre-processed vegetables that can be easily consumed even when frozen, from the perspective of nutritional balance.

[0004] Therefore, the inventors tried conventional methods for manufacturing frozen primary processed vegetables. However, although the conventional method solved the problems after thawing, it was still difficult to say that the vegetables were edible in their frozen state. Furthermore, there was room for improvement in the original flavor of the frozen primary processed vegetables. [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2021-145580 [Overview of the Initiative] [Problems that the invention aims to solve]

[0006] Therefore, the present invention has been made in view of these circumstances. The object of the present invention is to provide a novel method for producing frozen primary processed vegetables, and frozen primary processed vegetables, that have a moderate hardness that allows them to be chewed without being too hard or too soft even when eaten in a frozen state, and that maintain a pleasant chewiness, while also reducing the bitterness and grassy taste of the vegetables and retaining the original flavor of the vegetables. [Means for solving the problem]

[0007] The inventors diligently researched the components to be impregnated into vegetables and the manufacturing process in order to achieve the above objective. As a result, they discovered that if vegetables are impregnated with a sugar aqueous solution containing a small amount of specific organic acid and a high concentration of sugars, and then frozen, they can be eaten frozen without being too hard or too soft, but have a moderate firmness that allows for easy chewing, maintain a pleasant chewiness, and have reduced bitterness and grassy taste, resulting in frozen primary processed vegetables that retain the original flavor of the vegetables. This discovery finally led to the completion of the present invention.

[0008] In other words, the present invention is (1) A step of impregnating vegetables with a sugar solution, and a step of freezing the sugar-impregnated vegetables, A method for producing frozen primary processed vegetables, The aforementioned aqueous sugar solution contains one or more sugars, such as monosaccharides, oligosaccharides, or their reduced forms, and malic acid. The soluble solids content (Brix) of the aforementioned sugar aqueous solution is 30.0° or higher and 70.0° or lower. Of the soluble solids (Brix) of the aforementioned sugar aqueous solution, 80% by mass or more are the aforementioned sugars, and 0.001% by mass or more and 0.50% by mass or less are malic acid. The obtained frozen primary processed vegetable has a soluble solid content (Brix) of 15.0° or more and 25.0° or less, the impregnation amount of malic acid impregnated into the frozen primary processed vegetable is 0.0005 mass% or more and 0.1 mass% or less, under the following measurement conditions, the breaking load of the frozen primary processed vegetable is 1.0×10 3 g or more and 30.0×10 3 g or less, and the minimum value of the first derivative after breaking calculated for the function y=f(x) representing the relationship between load (y) and strain (x) after breaking is -30.0×10 4 g or more and -2.0×10 4 g or less, a method for producing a frozen primary processed vegetable, <Measurement Conditions> Sample product temperature: -18°C ± 2°C Measurement speed: 1 mm / sec Penetration strain rate: 80% Plunger shape: cylindrical stainless steel plunger with a diameter of 3 mm Load cell: 50 kg Sample thickness: 10 to 15 mm Analysis device: Texture Analyzer (2) The method for producing a frozen primary processed vegetable according to (1), comprising a heating step of heating the vegetable to a product temperature of 70°C or higher before or concurrently with the sugar impregnation step, (3) The method for producing a frozen primary processed vegetable according to (2), comprising a cooling step of cooling the heated vegetable after the heating step to a product temperature of 40°C or lower after the heating step, (4) The method for producing a frozen primary processed vegetable according to (1) or (2), wherein the vegetable is a root vegetable, a stem vegetable or a fruit vegetable, (5) A frozen primary processed vegetable impregnated with an aqueous sugar solution, the aqueous sugar solution contains one or more saccharides selected from monosaccharides, oligosaccharides or reduced products thereof, and malic acid, the frozen primary processed vegetable has a soluble solid content (Brix) of 15.0° or more and 25.0° or less, the impregnation amount of the malic acid impregnated into the frozen primary processed vegetable is 0.0005 mass% or more and 0.1 mass% or less, under the following measurement conditions, the breaking load of the frozen primary processed vegetable is 1.0×103 g or more and 30.0×10 3 g or less, and for the function y=f(x) representing the relationship between load (y) and strain (x) after fracture, the minimum value of the first derivative after fracture calculated is -30.0×10 4 g or more and -2.0×10 4 g or less, which is a primary frozen processed vegetable, <Measurement Conditions> Sample product temperature: -18°C ± 2°C Measurement speed: 1mm / sec Penetration strain: 80% Plunger shape: cylindrical stainless steel plunger with a diameter of 3 mm Load cell: 50 kg Sample thickness: 10~15 mm Analytical device: Texture Analyzer . Effects of the Invention

[0009] According to the present invention, a novel primary frozen processed vegetable can be provided, which does not become too hard or too soft even when eaten in a frozen state, has an appropriate hardness that allows chewing, maintains a suitable chewing texture, reduces the acridness and green grassy odor of vegetables, and retains the original umami of vegetables. Therefore, it can be expected to be in demand as a food with excellent nutritional balance that can be easily eaten by both infants and the elderly as a measure against heat stroke in summer. Mode for Carrying Out the Invention

[0010] Hereinafter, the present invention will be described in detail. In the present invention, "%" means "% by mass" and "parts" means "parts by mass".

[0011] <Features of the Present Invention> The present invention provides a novel method for producing frozen primary processed vegetables, and also provides frozen primary processed vegetables, which are obtained by impregnating vegetables with a sugar aqueous solution containing a small amount of specific organic acid and a high concentration of sugars, and then freezing them. The resulting frozen primary processed vegetables have a moderate hardness that allows them to be chewed without being too hard or too soft, even when eaten while frozen, and they maintain a pleasant chewiness. Furthermore, the bitterness and grassy taste of the vegetables are reduced, and the original delicious flavor of the vegetables is preserved.

[0012] <Meaning of each vegetable> In this invention, "vegetables" refers to raw vegetables as raw materials, as well as materials that have undergone or are about to undergo the processes described below. For each process that has been carried out, for example, a product that has undergone the sugar impregnation process with a sugar solution will be labeled as "sugar-impregnated vegetables, etc.," and the labeling will be done in a way that makes it possible to identify which process has been carried out. Furthermore, "frozen primary processed vegetables" refers to those obtained by the manufacturing method of the present invention, or the product of the present invention itself.

[0013] <Frozen primary processed vegetables> In the present invention, "frozen primary processed vegetables" refers to primary processed vegetables in a frozen state, and "primary processed vegetables" refers to vegetables that can be used as cooking ingredients, etc., as in the conventional method, but have been subjected to some treatment other than freezing, such as heat treatment, sterilization treatment, cutting treatment, immersion treatment, etc.

[0014] <Types of vegetables> Any vegetable other than potatoes and fruit vegetables can be used as the "frozen primary processed vegetable" of the present invention. Examples of such vegetables include root vegetables other than potatoes such as carrots, burdock, and lotus root; stem vegetables such as asparagus, celery, and udo; fruit vegetables such as tomatoes, pumpkins, cucumbers, sweet corn, and green peas; and leafy vegetables such as cabbage, lettuce, and spinach. In particular, the present invention is best suited for root vegetables, stem vegetables, or fruit vegetables, and is even more best suited for root vegetables or stem vegetables. Furthermore, since root vegetables such as sweet potatoes, potatoes, and taro are rich in starch, they are excluded from the vegetables used in this invention because, even without using the manufacturing method of the present invention, heating them to a temperature of 70°C or higher results in a moderate hardness that is neither too hard nor too soft, allowing them to be chewed even when consumed while still frozen.

[0015] <Types of sugars used in sugar solutions> In the present invention, the sugars used in the aqueous sugar solution are one or more monosaccharides, oligosaccharides, or reduced products thereof. Examples of monosaccharides include glucose, galactose, fructose, and xylose. Examples of disaccharide to decasaccharide oligosaccharides include lactose, sucrose, maltose, isomaltose, trehalose, cellobiose, maltooligosaccharide, isomaltoligosaccharide, gentiooligosaccharide, nigerooligosaccharide, fructooligosaccharide, and starch syrup. In addition, in the present invention, reducing sugars such as sorbitol and reduced starch syrup, which are reduced monosaccharides or oligosaccharides, may be used, or mixed sugars such as glucose-fructose syrup and glucose syrup may be used. Furthermore, the sugars used in the aqueous sugar solution of the present invention also include sugars derived from fruit juices such as fruit juice, concentrated fruit juice, or clarified concentrated fruit juice. Furthermore, in the case of using the aforementioned mixed liquid sugar, fruit juice, etc., the parts other than the sugars, such as water and organic acids, do not fall under the category of sugars.

[0016] <Concentration of soluble solids (Brix) in sugar aqueous solution> The concentration of soluble solids (Brix) in the aqueous sugar solution used in this invention, i.e., the Brix degree, is between 30.0° and 70.0°. At the lower limit of the range, it is preferably 32.0° or more, more preferably 35.0° or more, and at the upper limit, it is preferably 65.0° or less, more preferably 60.0° or less. If the temperature falls below the lower limit, the chewiness decreases sharply and does not maintain a suitable level of chewiness. Also, if consumed while frozen, it may be too hard and not have the appropriate firmness for chewing. On the other hand, if the temperature exceeds the upper limit of the range, if consumed while frozen, it may be too soft and not have the appropriate firmness for chewing, and the texture will remain soft afterward, not maintaining a suitable level of chewiness.

[0017] <Concentration of the sugars in the soluble solids (Brix) of the aqueous sugar solution> In the present invention, the sugars make up the soluble solids (Brix) of the aqueous sugar solution, that is, the concentration of the sugars when the soluble solids (Brix) are set to 100%, is 80% or more, preferably 85% or more, more preferably 90% or more, and even more preferably 95% or more. If the value falls below the aforementioned lower limit, it may be difficult to obtain frozen primary processed vegetables that have an appropriate hardness that allows them to be chewed without being too hard, which is the effect of the present invention. Furthermore, the reduction of bitterness and grassy taste in the vegetables may not be sufficient, and the frozen primary processed vegetables may not be able to be said to have the original flavor of the vegetables.

[0018] <Malic acid concentration in soluble solids (Brix) of sugar aqueous solution> In the present invention, the malic acid content of the soluble solids (Brix) of the aqueous sugar solution, that is, the concentration of malic acid when the soluble solids (Brix) is set to 100%, is 0.001% or more and 0.50% or less. At the lower limit of the above range, it is preferably 0.005% or more, and more preferably 0.01% or more. At the upper limit of the above range, it is preferably 0.35% or less. If the value falls below the lower limit of the aforementioned range, the bitterness and grassy taste of vegetables, which are the effects of the present invention, will not be sufficiently reduced, and the original deliciousness of the vegetables will be compromised. On the other hand, if the upper limit of the aforementioned range is exceeded, the bitterness and grassy taste of the vegetables will be sufficiently reduced, but the sourness of malic acid may be present, which may impair the original flavor of the vegetables. In addition, while malic acid itself may be added, fruit juices containing malic acid, such as apple juice, peach juice, or lemon juice, concentrated fruit juice, or clarified concentrated fruit juice thereof, may also be added to achieve a malic acid concentration within the aforementioned range. Furthermore, in this invention, a salt thereof may be used as the malic acid, in which case the concentration converted to malic acid corresponds to the aforementioned malic acid concentration.

[0019] <Overview of the process of the present invention> A typical method for producing frozen primary processed vegetables according to the present invention comprises at least a sugar impregnation step of impregnating vegetables with the sugar aqueous solution, and a freezing step of freezing the sugar-impregnated vegetables. Furthermore, by including a heating step in which the vegetables are heated to a temperature of 70°C or higher before or together with the sugar impregnation step, it becomes possible to efficiently impregnate the vegetables with sugars and malic acid, which reduces bitterness and grassy taste in the vegetables and makes it easier to obtain frozen primary processed vegetables that retain the original flavor of the vegetables, which is preferable. Furthermore, after the heating step, it is preferable to have a cooling step in which the heated vegetables are cooled to a temperature of 40°C or lower, as this helps to better preserve the original flavor of the vegetables. The manufacturing method of the present invention will be described in more detail below.

[0020] <Pre-processing of vegetables> A typical manufacturing method of the present invention involves first pre-treating the raw vegetables, such as washing, peeling, surface sterilization, or freezing, or cutting them into bite-sized pieces, or a combination of these processes.

[0021] <Cutting, one of the pre-processing steps for vegetables> As for the cutting method, any method commonly used in cooking is acceptable, such as rough chopping, dicing, slicing, cube cutting, or ginkgo leaf cutting. As for the size after cutting, there are no particular restrictions as long as it is a size that is easy to eat, but specifically, depending on the type of vegetable, it is good to cut it into pieces of about 0.5 cm to 5 cm, or 1 g to 10 g.

[0022] <Peeling, one of the pre-processing steps for vegetables> For peeling, any method commonly used in cooking is acceptable, such as removing the outer skin with a knife or peeling device, or, as described in the examples below, a method that removes the outer skin cleanly and efficiently, for example, so-called blanching, where the outer skin is removed after immersing in hot water at 90°C or higher for 5 to 30 seconds.

[0023] <Surface sterilization, one of the pre-treatment methods for vegetables> For surface sterilization, the present invention can use sterilization methods employed in the food industry, such as using sterilized water such as hypochlorous acid water or ozonated water, or immersing in hot water at 70°C or higher for several seconds to one minute. In addition, while the pre-treatment of vegetables, such as blanching and hot water sterilization, involves a heating process, it is not included in the heating process described later in this invention.

[0024] <Amount of sugar solution used in the sugar impregnation process> In a typical manufacturing method of the present invention, a sugar aqueous solution is first prepared in order to impregnate vegetables with sugar. The sugar aqueous solution used in the present invention is as described in paragraphs 0015 to 0018. The amount of sugar solution depends on the shape and size of the vegetables being treated, but it should be an amount sufficient to allow the surface of the vegetables being treated in the sugar impregnation process to come into contact with the sugar solution. Specifically, for example, it is preferable to use 0.4 parts or more, more preferably 0.5 parts or more, of the sugar solution per part of the vegetables being treated in the sugar impregnation process. In this invention, there are no particular restrictions on the upper limit of the amount of sugar aqueous solution, but considering productivity, it is preferable to use 20 parts or less, and more preferably 15 parts or less, of sugar aqueous solution per part of vegetables.

[0025] <Sugar impregnation time in the sugar impregnation process> In the sugar impregnation step of the present invention, the sugar impregnation time needs to take into account various factors, such as the type, shape and size of vegetables, the concentration of soluble solids (Brix) in the aqueous sugar solution, the type and concentration of sugars in the soluble solids (Brix), and also whether a heating step described later is involved or not. Furthermore, the product of the present invention is a frozen primary processed vegetable that has an appropriate hardness that can be chewed without being too hard or too soft when eaten in a frozen state, and maintains a suitable chewing resistance. Specifically, the breaking load described later is 1.0×10 3 g or more and 30.0×10 3 g or less, and the minimum value of the primary differential value after breaking is -30.0×10 4 g or more and -2.0×10 4 g or less. It is necessary to satisfy this range. In consideration of the above factors, in the present invention, the breaking load is 1.0×10 3 g or more and 30.0×10 3 g or less, and the minimum value of the primary differential value after breaking is -30.0×10 4 g or more and -2.0×10 4 g or less, and the sugar impregnation time may be determined so as to fall within this range. Specifically, the sugar impregnation time in the sugar impregnation step of the present invention is, for example, preferably 10 hours or more and 200 hours or less. Furthermore, the lower limit of the sugar impregnation time is more preferably 12 hours or more, still more preferably 15 hours or more, and the upper limit is more preferably 150 hours or less, still more preferably 120 hours or less.

[0026] <Processing Temperature of Sugar Impregnation Step> Since the sugar impregnation time in the sugar impregnation step of the present invention is long, the treatment is preferably carried out under refrigeration at 0°C or more and 10°C or less, more preferably 0°C or more and 8°C or less, in order to suppress the growth of bacteria during this period.

[0027] <Other Conditions for Sugar Impregnation Step> The sugar impregnation step may be carried out while slowly stirring the whole, as long as the shape of the vegetables is not impaired.

[0028] <Heating Step> A typical manufacturing method of the present invention may include a heating step in which the vegetables are heated to a temperature of 70°C or higher, more preferably 80°C or higher, before or together with the sugar impregnation step. Including a heating step makes it possible to efficiently impregnate the vegetables with sugars and the specific organic acids, which reduces the bitterness and grassy taste of the vegetables and makes it easier to obtain frozen primary processed vegetables that retain the original flavor of the vegetables, which is preferable.

[0029] <Heating method in the heating process> The method of heating vegetables in the heating process is not particularly limited, as long as it is a method used in the food industry, such as hot water, steam, or an electromagnetic field. However, heating with hot water is preferred because it has excellent thermal conductivity and productivity, and it is easy to control the temperature of the vegetables.

[0030] <Hot water heating process> For example, in the hot water heating step, in order to heat-treat the vegetables to the predetermined product temperature, the vegetables that have undergone pre-treatment such as cutting are placed in hot water at approximately the same temperature or slightly higher, and the heating treatment is preferably carried out for 5 to 60 minutes, more preferably for 5 to 45 minutes, and even more preferably for 5 to 30 minutes. While there are no specific regulations regarding the upper limit of the vegetable temperature during the heating process, it is preferable to set it to 110°C or lower, and more preferably 100°C or lower, considering the ease of temperature control and productivity of the vegetables. Furthermore, the amount of hot water, as with the "amount of sugar solution used in the sugar impregnation process" in paragraph 0024, depends on the shape and size of the vegetables to be heat-treated, but it should be an amount sufficient to allow the surface of the vegetables to be treated in the heating process to come into contact with the hot water. Specifically, for example, it is preferable to use 0.4 parts or more, more preferably 0.5 parts or more, of hot water per part of vegetables to be treated in the heating process. There is no particular upper limit, but considering productivity, it is preferable to use 20 parts or less, more preferably 15 parts or less, of hot water per part of vegetables.

[0031] <Heating process using sugar solution> When a heating step is performed along with the sugar impregnation step, it is preferable to perform the heat treatment with a sugar aqueous solution heated to a predetermined temperature instead of the hot water. The time required for the heating process is also included in the time required for the sugar impregnation process in this invention, as it also serves as the impregnation treatment with the sugar aqueous solution.

[0032] <Cooling process> In a typical manufacturing method of the present invention, if the heating step is performed, it is preferable to include a cooling step in which the heated vegetables are cooled to a product temperature of preferably 40°C or lower, more preferably 35°C or lower. In particular, rapid cooling is preferred, in which the heated vegetables are cooled to the product temperature within 60 minutes. Performing the cooling step is preferable because it does not impair the appearance of the vegetables. Examples of cooling methods include removing cooked vegetables from hot water or heated sugar solution and then impregnating them in cooling water or sugar solution at room temperature (25°C) or below, preferably refrigerated (10°C or below), but the present invention is not particularly limited to these methods.

[0033] <Freezing process> A typical manufacturing method of the present invention includes a freezing step in which sugar-impregnated vegetables are frozen. Freezing methods include rapid freezing, in which the core temperature of the food passes through the maximum ice crystal formation temperature range of -1°C to -5°C within 30 minutes, and slow freezing, which takes longer than that time. In the present invention, either rapid freezing or slow freezing may be used, but rapid freezing is preferred because it is easier to obtain frozen primary processed vegetables that are neither too hard nor too soft, have a moderate hardness that allows for chewing, and maintain a pleasant chewiness even when eaten in a frozen state. Furthermore, the final freezing temperature in the freezing process can be any temperature between -30°C and -15°C, which is the typical storage temperature for frozen foods, and it is also advisable to store the frozen primary processed vegetables at the aforementioned temperature.

[0034] <Regarding frozen primary processed vegetables obtained by the manufacturing method of the present invention> The above describes a typical manufacturing method of the present invention. The frozen primary processed vegetables obtained by this manufacturing method have a soluble solids content (Brix) of 15.0° to 25.0°. The amount of malic acid impregnated into the aforementioned frozen primary processed vegetables is 0.0005% or more and 0.1% or less. Under the following measurement conditions, the breaking load of the frozen primary processed vegetable was 1.0 × 10⁻⁶. 3 g or more 30.0×10 3 The minimum value of the first derivative after fracture calculated for the function y=f(x), which shows the relationship between load (y) and strain (x) after fracture, for values ​​less than or equal to g, is -30.0 × 10⁻¹⁰. 4 g or more -2.0×10 4 It is less than or equal to g. <Measurement conditions> Sample temperature: -18℃±2℃ Measurement speed: 1mm / sec Penetration distortion: 80% Plunger shape: 3mm diameter cylindrical stainless steel plunger Load cell: 50kg Sample thickness: 10-15 mm Analytical device: Texture analyzer

[0035] <Amount of soluble solids (Brix) in frozen primary processed vegetables> The amount of soluble solids (Brix) of pre-treated vegetables used in the present invention, also known as the Brix degree, is generally less than 15.0°, although this varies depending on the type of vegetable. In contrast, the amount of soluble solids (Brix) of the frozen primary processed vegetables of the present invention is 15.0° to 25.0°, preferably 16.0° to 24.0°. If the amount of soluble solids (Brix) in the frozen primary processed vegetables of the present invention falls below the aforementioned lower limit, the chewiness decreases rapidly and does not maintain a suitable level of chewiness. Furthermore, when consumed while still frozen, the vegetables may be too hard and cannot be said to have a suitable chewiness. On the other hand, if the temperature exceeds the upper limit of the aforementioned range, the food will be too soft when eaten while frozen, lacking the appropriate firmness for chewing, and will remain soft even after chewing, failing to maintain a pleasant chewiness.

[0036] <Analysis method for soluble solids (Brix)> The soluble solids (Brix) of the pre-treated vegetables used in this invention, or the frozen primary processed vegetables of this invention, are determined by pasteuring the vegetables using a conventional method, separating the clarified liquid using a filter cloth, filter paper, etc., and analyzing the amount of soluble solids (Brix) in the clarified liquid using a commercially available Brix meter. The soluble solids (Brix) of the aforementioned sugar aqueous solution can be analyzed directly using a Brix meter because the sugar aqueous solution is a clarified liquid.

[0037] <Amount of malic acid impregnated into frozen primary processed vegetables> In this invention, malic acid is impregnated into vegetables along with sugars by performing a sugar impregnation process using a sugar aqueous solution containing malic acid. In this invention, the amount of malic acid impregnated into the frozen primary processed vegetables is 0.0005% or more and 0.1% or less. The lower limit of the above range is preferably 0.0008% or more, more preferably 0.001% or more, and the upper limit is preferably 0.08% or less. If the values ​​fall below the aforementioned lower limit, the bitterness and grassy taste of the vegetables are not reduced, and it is difficult to say that they possess the original flavor of the vegetables. On the other hand, if the above upper limit is exceeded, the frozen primary processed vegetables will exhibit a sour taste and it is difficult to say that they possess the original flavor of the vegetables.

[0038] <Method for calculating the amount of malic acid impregnation> In this invention, the amount of malic acid impregnated into the frozen primary processed vegetables is first calculated by subtracting the soluble solids (Brix) of the pre-treated vegetables from the soluble solids (Brix) of the frozen primary processed vegetables to determine the amount of malic acid impregnated into the frozen primary processed vegetables in terms of soluble solids (Brix). Next, the percentage of the soluble solids (Brix) of the sugar solution used that was impregnated is calculated from the amount of malic acid impregnated into the frozen primary processed vegetables in terms of soluble solids (Brix). Then, the concentration of malic acid in the sugar solution used is calculated from the concentration of malic acid relative to the soluble solids (Brix) of the sugar solution used, and the amount of malic acid impregnated into the frozen primary processed vegetables is calculated by multiplying this malic acid concentration by the impregnation percentage. For example, as detailed in Example 1 described below, the amount of soluble solids (Brix) impregnated by the sugar solution impregnated into the frozen primary processed vegetables is 11.2° (=21.2°-10.0°). From the soluble solids of the impregnated sugar solution of 11.2°, 23.6% (=11.2°×100 / 47.5°) of the sugar solution used has penetrated into the pre-treated vegetables. The malic acid content of the sugar solution used is 0.048% (=47.5°×0.1% / 100), so the amount of malic acid impregnated into the frozen primary processed vegetables is 0.011% (=0.048%×23.6% / 100). When calculating the soluble solids (Brix) increased by the sugar solution, the soluble solids (Brix) of the pre-treated vegetables are subtracted from the soluble solids (Brix) of the frozen primary processed vegetables. However, the soluble solids (Brix) of the pre-treated vegetables are approximately the same as the soluble solids (Brix) of the raw vegetables used.

[0039] <Method for analyzing malic acid> Since most vegetables do not contain malic acid, the amount of malic acid impregnation may be calculated based on the malic acid content extracted and analyzed from the frozen primary processed vegetables of the present invention according to Chapter 6 "Carbohydrates and Organic Acids," "41-1 High-Performance Liquid Chromatography," "(d) In the case of heterogeneous solid samples such as meat and vegetables," of the Analysis Manual for the 2015 Edition of the Japanese Food Composition Table. The following describes specific methods for extracting and analyzing organic acids, including malic acid.

[0040] <1) Extraction: (d) In the case of heterogeneous solid samples such as meat and vegetables> Weigh approximately 2 g (W) of the sample into a centrifuge tube, add 20 mL (V) of 0.5% (V / V) perchloric acid, mix with a homogenizer, then transfer to a 100 mL Erlenmeyer flask while grinding with a wire mesh funnel and glass rod, filter, and use the filtered solution as the sample solution for measurement.

[0041] <2) High-performance liquid chromatography> Column: 8.0mm inner diameter, 300mm length, ion exclusion and reverse-phase column (two Shodex RSpak KC-811 columns linked together) Column temperature: 40℃ Mobile phase: 3mmol / L perchloric acid Reaction solution: 15 mmol / L disodium hydrogen phosphate solution containing 0.2 mmol / L bromothymol blue. Flow rate: Mobile phase 1.0 mL / min, reaction solution 1.4 mL / min Measurement wavelength: 445nm

[0042] <3) Measurement> The sample solution for measurement is injected into a high-performance liquid chromatograph under the above conditions, and the peak height of each organic acid is measured. Similarly, standard solutions are injected, and a calibration curve is created.

[0043] <4) Calculation> Organic acid content (g / 100g)=(A×V×100) / (W×1000) A: Organic acid concentration (mg / mL) in the sample solution determined from the calibration curve. V: Constant volume (mL) W: Sample volume (g)

[0044] <Minimum breaking load and first derivative after breaking of frozen primary processed vegetables> The breaking load of the frozen primary processed vegetables of the present invention is 1.0 × 10⁻⁶ 3 g or more 30.0×10 3 The minimum value of the first derivative after fracture calculated for the function y=f(x), which shows the relationship between load (y) and strain (x) after fracture, is -30.0 × 10⁻⁶. 4 g or more -2.0×10 4 It is less than or equal to g. Furthermore, the lower limit of the breaking load is preferably 2.0 × 10 3 It is 10 g or more, and the upper limit is preferably 25.0 × 10 3 It is less than or equal to g. The lower limit of the minimum first derivative value after fracture is preferably -25.0 × 10 4 It is 10g or more, and the upper limit is preferably -2.5 × 10 4 It is less than or equal to g. If the breaking load of frozen primary processed vegetables falls below the aforementioned range, they will be too soft when consumed while still frozen and will not have the appropriate firmness for eating. On the other hand, if the breaking load of the frozen primary processed vegetables exceeds the aforementioned range, they will be too hard to eat while still frozen and will not have the appropriate firmness for consumption. Furthermore, if the minimum value of the first derivative after fracture exceeds the aforementioned range, it indicates that the food is too soft when consumed while frozen, and that it remains soft afterward, failing to maintain a pleasant chewiness. On the other hand, if the minimum value of the first derivative after fracture falls below the aforementioned range, the chewiness decreases rapidly and does not maintain a pleasant chewiness.

[0045] <Method for measuring the minimum breaking load and first derivative after breaking of frozen primary processed vegetables> The present invention is analyzed under the following measurement conditions, where the breaking load is the value obtained by rounding the analytical value to the nearest tens of grams, and the minimum value of the first derivative after breaking is the value obtained by rounding the analytical value to the nearest hundred grams. Since the samples will be analyzed using the analytical instrument described below, samples with a nearly flat top and bottom surface and a thickness of 10-15 mm should be selected and analyzed. If all samples are less than 10 mm thick (for example, celery), select a sample that is close to 10 mm thick for analysis. If there are no samples with a thickness of 10-15 mm but with both the top and bottom surfaces being approximately flat, select a sample with one side being approximately flat, cut the opposite side to be approximately flat while maintaining the thickness of 10-15 mm, and analyze the sample with the cut surface facing downwards. For samples that are roughly spherical, such as cherry tomatoes, select those with a diameter of 10-15 mm and analyze them by pressing them from above with a plunger. The sliced ​​celery in Example 4, described later, was analyzed by pressing it from the inner skin side with a plunger. Furthermore, during analysis, the sample temperature should be pre-adjusted to -20°C using a constant temperature incubator or similar device so that the analysis can be performed within the temperature range specified in the measurement conditions below. Immediately before analysis, the sample should be removed from the incubator and analyzed immediately. If the sample shifts during measurement, it may be supported with a finger or similar object to prevent it from shifting, as long as the sample temperature does not exceed the upper limit. <Measurement conditions> Sample temperature: -18℃±2℃ Measurement speed: 1mm / sec Penetration distortion: 80% Plunger shape: 3mm diameter cylindrical stainless steel plunger Load cell: 50kg Sample thickness: 10-15 mm Analytical instrument: Texture analyzer (TA-XT-plus: manufactured by Stable Micro Systems) [Examples]

[0046] The present invention will be described in detail below based on examples and comparative examples of the present invention, as well as Table 1. However, the present invention is not limited to these examples.

[0047] <Example 1> Carrots (1) Pretreatment After removing the outer skin from the carrots, they were cut into irregular pieces weighing 3g to 6g to obtain pre-treated carrots. The soluble solids content (Brix) of the pre-treated carrots was 10.0°.

[0048] (2)Heating process One portion of the pre-treated carrots was placed in three portions of hot water heated to 95°C using a kneader, and the mixture was heated at the same temperature for 10 minutes while being slowly stirred.

[0049] (3) Cooling process After removing the preheated carrots from the kneader, they were immediately placed in room temperature (approximately 20°C) cooling water and rapidly cooled to a temperature of 35°C or lower within 60 minutes while the cooling water was running.

[0050] (4) Sugar impregnation process Of the soluble solids (Brix) of the sugar aqueous solution, 99.9% was fructose and 0.1% was malic acid. The sugar aqueous solution was prepared so that the soluble solids (Brix) of the sugar aqueous solution was 47.5°. Sixty parts of the cooled carrots were placed into 40 parts of the sugar aqueous solution cooled to a liquid temperature of 5°C, and a sugar impregnation process was carried out at the same temperature for 16 hours.

[0051] (5) Freezing process After removing the sugar-impregnated vegetables from the sugar solution, they were arranged on a tray lined with parchment paper so that they did not overlap, and then frozen in a freezing device by rapid freezing, passing through the maximum ice crystal formation temperature range of -1°C to -5°C within 30 minutes, until the product temperature reached -25°C, thereby producing the frozen primary processed carrots of the present invention.

[0052] <Example 2> Burdock (1) Pretreatment After removing the outer skin of the burdock root, it was sliced ​​into rounds to obtain pre-treated burdock root. The size of the round slices was 1 cm thick for those with a diameter of less than 2 cm, and 0.5 cm thick for those with a diameter of 2 cm or more. The soluble solids content (Brix) of the pre-treated burdock was 9.0°.

[0053] (2) Heating process and (3) Cooling process The pre-treated burdock root was subjected to a heating and cooling process in the same manner as in Example 1.

[0054] (4) Sugar impregnation process Sucrose, 4x concentrated peach juice, and 5x concentrated lemon juice were dissolved in clean water to prepare a sugar aqueous solution with a Brix of 36.0°. Of the soluble solids (Brix) of the sugar aqueous solution, 95.0% is sucrose, 3.0% is sugars derived from the two types of concentrated fruit juices, and 0.17% of the soluble solids (Brix) of the sugar aqueous solution is malic acid derived from the two types of concentrated fruit juices. The 55 parts of the cooled burdock were placed into 45 parts of the sugar aqueous solution cooled to a liquid temperature of 5°C, and a sugar impregnation process was carried out at the same temperature for 32 hours.

[0055] (5) Freezing process The sugar-impregnated burdock was subjected to a freezing process in the same manner as in Example 1 to produce the frozen primary processed burdock of the present invention.

[0056] <Example 3> Cherry Tomatoes (1) Pretreatment One portion of cherry tomatoes was placed in two portions of 95°C hot water and heated for 20 seconds. Immediately afterward, the tomatoes were removed, and the outer skins of the cherry tomatoes were blanched to obtain pre-treated cherry tomatoes. The soluble solids content (Brix) of the blanched and pre-treated cherry tomatoes was 6.0°C.

[0057] (2) Heating process and (3) Cooling process The pre-treated mini tomatoes were not subjected to heating or cooling processes.

[0058] (4) Sugar impregnation process Apple clarified concentrate (Brix 70.1°), malic acid, and water were mixed to prepare a sugar aqueous solution with a soluble solids content (Brix) of 54.0°. Of the soluble solids (Brix) in the aforementioned sugar aqueous solution, 99.9% are sugars derived from clarified and concentrated apple juice, and 0.06% of the soluble solids (Brix) in the aforementioned sugar aqueous solution are malic acid. 65 portions of the pre-treated mini tomatoes were placed in 35 portions of the sugar aqueous solution cooled to 5°C, and a sugar impregnation process was carried out at the same temperature for 80 hours.

[0059] (5) Freezing process The sugar-impregnated mini tomatoes were subjected to a freezing process in the same manner as in Example 1 to produce the frozen primary processed mini tomatoes of the present invention.

[0060] <Example 4> Celery (stalk portion) (1) Pretreatment Commercially available IQF (Individual Quick Frozen) celery was sliced ​​into 3cm-thick rounds. One portion of the sliced ​​celery was then placed in two portions of 90°C hot water and heated for 10 seconds at the same temperature. After heating, it was immediately removed to obtain pre-treated celery. The soluble solids content (Brix) of the pre-treated celery was 3.0°C.

[0061] (2) Heating process and (3) Cooling process The pre-treated celery was not subjected to heating or cooling steps.

[0062] (4) Sugar impregnation process Glucose-fructose syrup (product name: Fruct M75C, manufactured by Nippon Corn Starch Co., Ltd., Brix 75°) and malic acid were dissolved in plain water to prepare a sugar aqueous solution with a soluble solids content (Brix) of 60.0°. Of the soluble solids (Brix) of the aforementioned sugar aqueous solution, 99.6% are sugars from the glucose-fructose syrup, and 0.34% of the soluble solids (Brix) of the aforementioned sugar aqueous solution are malic acid. 65 parts of the pre-treated celery were added to 35 parts of the sugar aqueous solution cooled to a liquid temperature of 5°C, and a sugar impregnation process was carried out at the same temperature for 24 hours.

[0063] (5) Freezing process The sugar-impregnated celery was subjected to a freezing process in the same manner as in Example 1 to produce the frozen primary processed celery of the present invention.

[0064] <Example 5> Carrots (1) Pretreatment After removing the outer skin from the carrots, they were cut into 1.5 cm cubes. The soluble solids content (Brix) of the pre-treated carrots was 10.0°.

[0065] (2) Heating process and (4) Sugar impregnation process Reduced starch syrup (product name: SE57, manufactured by Bussan Food Science Co., Ltd., Brix 70.0°) and malic acid were dissolved in clean water to prepare a sugar aqueous solution so that the soluble solids content (Brix) of the sugar aqueous solution was 35.0°. Of the soluble solids (Brix) of the aforementioned sugar aqueous solution, 99.9% are sugars from the reduced starch syrup, and 0.02% are malic acid. Fifty parts of the pre-treated carrots were placed in a kneader into fifty parts of the sugar solution heated to 95°C, and subjected to a heat treatment and sugar impregnation treatment at the same temperature for 5 minutes while slowly stirring.

[0066] (3) Cooling process and (4) Sugar impregnation process After removing the heated and partially sugar-impregnated carrots from the kneader, 50 portions of them were immediately added to 50 portions of the sugar solution that had been prepared separately and cooled to a liquid temperature of 5°C. The heated and partially sugar-impregnated carrots were rapidly cooled within 60 minutes while the sugar solution was being cooled, so that the product temperature was 35°C or lower.

[0067] (4) Sugar impregnation process Fifty portions of the cooled carrots were placed in fifty portions of the sugar solution prepared separately at a liquid temperature of 5°C, and the sugar impregnation process was carried out at the same temperature. The total time for the sugar impregnation process using the sugar solution was 24 hours, which is the sum of the processing time in the heating process (2) and the cooling process (3) and the processing time in the sugar impregnation process (4).

[0068] (5) Freezing process The sugar-impregnated carrots were subjected to a freezing process in the same manner as in Example 1 to produce the frozen primary processed carrots of the present invention.

[0069] <Example 6> Burdock (1) Pretreatment The same pretreatment as in Example 2 was performed. The soluble solids content (Brix) of the pretreated burdock was 9.0°.

[0070] (2) Heating process and (3) Cooling process The pre-treated burdock was subjected to the same heating and cooling steps as in Example 1, except that it was heated in 85°C hot water for 20 minutes.

[0071] (4) Sugar impregnation process Corn syrup (product name: Tetrap, manufactured by Nagase Vita Co., Ltd., Brix 72°) and 4x concentrated peach juice were mixed with clean water to prepare a sugar aqueous solution with a soluble solids content (Brix) of 43.0°. Of the soluble solids (Brix) of the sugar aqueous solution, 99.7% are sugars from the corn syrup, 0.2% are sugars from the concentrated fruit juice, and 0.006% of the soluble solids (Brix) of the sugar aqueous solution are malic acid derived from the concentrated fruit juice. The 55 parts of the cooled burdock were placed into 45 parts of the sugar aqueous solution cooled to a liquid temperature of 5°C, and a sugar impregnation process was carried out at the same temperature for 40 hours.

[0072] (5) Freezing process The sugar-impregnated burdock was subjected to a freezing process in the same manner as in Example 1 to produce the frozen primary processed burdock of the present invention.

[0073] <Comparative Example 1> Burdock (1) Pretreatment After removing the outer skin of the burdock root, it was cut into the same shape and size as in Example 2. The soluble solids content (Brix) of the pre-treated burdock root was 9.0°.

[0074] (2) Heating process and (3) Cooling process The pre-treated burdock root was subjected to a heating and cooling process in the same manner as in Example 1.

[0075] (4) Sugar impregnation process Sucrose was dissolved in clean water to prepare a sugar aqueous solution with a Brix content of 20.0°. Furthermore, the entire amount of soluble solids (Brix) in the aforementioned sugar aqueous solution is sucrose, and the aforementioned sugar aqueous solution does not contain malic acid. Sixty parts of the pre-treated burdock were placed in 40 parts of the sugar aqueous solution cooled to 5°C, and a sugar impregnation process was carried out at the same temperature for 3 hours.

[0076] (5) Freezing process The sugar-impregnated burdock was subjected to a freezing process in the same manner as in Example 1 to produce a comparative frozen primary processed burdock.

[0077] <Comparative Example 2> Carrots (1) Pretreatment After removing the outer skin of the carrots, they were cut into the same shape and size as in Example 5. The soluble solids content (Brix) of the pre-treated carrots was 10.0°.

[0078] (2) Heating process and (3) Cooling process The pre-treated carrots were subjected to the same heating and cooling processes as in Example 1, except that they were subjected to a heat treatment for 120 minutes.

[0079] (4) Sugar impregnation process Glucose-fructose syrup (product name: Fruct M75C, manufactured by Nippon Corn Starch Co., Ltd., Brix 75°), malic acid, and purified water were mixed to prepare a sugar aqueous solution with a soluble solids content (Brix) of 73.0°. Of the soluble solids (Brix) of the aforementioned sugar aqueous solution, 99.9% are sugars from the glucose-fructose syrup, and 0.003% of the soluble solids (Brix) of the aforementioned sugar aqueous solution are malic acid. Sixty parts of the cooled carrots were placed into 40 parts of the sugar aqueous solution cooled to a liquid temperature of 5°C, and a sugar impregnation process was carried out at the same temperature for 240 hours.

[0080] (5) Freezing process The sugar-impregnated carrots were subjected to a freezing process in the same manner as in Example 1 to produce a comparative frozen primary processed carrot.

[0081] <Analysis results> Each of the frozen primary processed vegetables obtained in Examples 1 to 6 and Comparative Examples 1 to 2 was analyzed according to the method for analyzing soluble solids (Brix) described in paragraph 0036, the method for calculating malic acid described in paragraph 0038, and the method for measuring the minimum value of the breaking load and the first derivative after breaking described in paragraph 0045. The results are shown in Table 1.

[0082] [Table 1]

[0083] As shown in Table 1, in the sugar impregnation process before freezing, the amount of soluble solids (Brix) in the sugar aqueous solution and the content of sugars and malic acid in the soluble solids (Brix) were controlled, and the amount of soluble solids (Brix) and malic acid impregnation in the frozen primary processed vegetables were within a specified range. The resulting products had a moderate hardness that was neither too hard nor too soft, allowing for easy chewing even when consumed frozen, and maintained a pleasant chewiness. Furthermore, the bitterness and grassy taste of the vegetables were reduced, and the vegetables retained their original flavor. On the other hand, the comparative product in Comparative Example 1, which used a sugar aqueous solution with a low amount of soluble solids (Brix), was hard when eaten frozen, but had a moderate hardness that allowed it to be chewed. However, the chewiness decreased rapidly and did not last long, and furthermore, the bitterness derived from burdock was not reduced, and it did not have the original flavor of the vegetable. Furthermore, in Comparative Example 2, which used a sugar solution with a high amount of soluble solids (Brix) and a low malic acid content, the product was too soft when consumed frozen, lacking the appropriate chewiness. Moreover, it remained soft even after chewing, failing to maintain a pleasant texture, and was too sweet, lacking the natural flavor of the vegetables. In Example 4, since all the celery samples were less than 10 mm thick, the one with a thickness of 8 mm, which was the closest to 10 mm, was selected, and the minimum breaking load and first derivative value were determined.

Claims

1. A method for producing frozen primary processed vegetables, comprising a sugar impregnation step of impregnating vegetables with a sugar aqueous solution and a freezing step of freezing the sugar-impregnated vegetables, The aforementioned aqueous sugar solution contains one or more sugars, such as monosaccharides, oligosaccharides, or their reduced forms, and malic acid. The soluble solids content (Brix) of the aforementioned sugar aqueous solution is 30.0° or higher and 70.0° or lower. Of the soluble solids (Brix) of the aforementioned sugar aqueous solution, 80% by mass or more are the aforementioned sugars, and 0.001% by mass or more and 0.50% by mass or less are malic acid. The soluble solids content (Brix) of the obtained frozen primary processed vegetables is 15.0° or higher and 25.0° or lower. The amount of malic acid impregnated into the aforementioned frozen primary processed vegetables is 0.0005% by mass or more and 0.1% by mass or less. Under the following measurement conditions, the breaking load of the frozen primary processed vegetable was 1.0 × 10⁻⁶. ３ g or more 30.0×10 ３ The minimum value of the first derivative after fracture calculated for the function y = f(x), which shows the relationship between load (y) and strain (x) after fracture, for values ​​less than or equal to g, is -30.0 × 10⁻¹⁰. ４ g or more -2.0×10 ４ It is less than or equal to g. A method for producing frozen primary processed vegetables, characterized by the following: (excluding potatoes and fruit-like vegetables as vegetables used in the frozen primary processed vegetables). <Measurement conditions> Sample temperature: -18°C ± 2°C Measurement speed: 1mm / sec Penetration distortion: 80% Plunger shape: 3mm diameter cylindrical stainless steel plunger Load cell: 50 kg Sample thickness: 10-15 mm Analysis device: Texture analyzer

2. The process includes a heating step in which the vegetables are heated to a temperature of 70°C to 100°C before or together with the sugar impregnation step. A method for producing frozen primary processed vegetables according to claim 1, characterized in that

3. The heating step is followed by a cooling step in which the heated vegetables are cooled to a temperature of 40°C or lower. A method for producing frozen primary processed vegetables according to claim 2, characterized in that

4. The aforementioned vegetables are root vegetables, stem vegetables, or fruit vegetables. A method for producing frozen primary processed vegetables according to claim 1 or 2, characterized in that

5. A frozen primary processed vegetable that has been impregnated with a sugar solution, The aforementioned aqueous sugar solution contains one or more sugars, such as monosaccharides, oligosaccharides, or their reduced forms, and malic acid. The soluble solids content (Brix) of the aforementioned frozen primary processed vegetables is 15.0° or higher and 25.0° or lower. The amount of malic acid impregnated into the frozen primary processed vegetables is 0.0005% by mass or more and 0.1% by mass or less. Under the following measurement conditions, the breaking load of the frozen primary processed vegetable was 1.0 × 10⁻⁶. ３ g or more 30.0×10 ３ The minimum value of the first derivative after fracture calculated for the function y = f(x), which shows the relationship between load (y) and strain (x) after fracture, for values ​​less than or equal to g, is -30.0 × 10⁻¹⁰. ４ g or more -2.0×10 ４ It is less than or equal to g. A frozen primary processed vegetable characterized by the following features (excluding potatoes and fruit-like vegetables as vegetables used in the frozen primary processed vegetable): <Measurement conditions> Sample temperature: -18°C ± 2°C Measurement speed: 1mm / sec Penetration distortion: 80% Plunger shape: 3mm diameter cylindrical stainless steel plunger Load cell: 50 kg Sample thickness: 10-15 mm Analysis device: Texture analyzer

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