Frozen strawberry and production method thereof

Abstract

To provide frozen strawberries, even when eaten in a frozen state, having a firm yet crisp texture without being too sweet, and a production method of the frozen strawberries.SOLUTION: A frozen strawberry vertically cut in half by a texture analyzer ("TA. XTPLUS" manufactured by Stable Micro Systems) is placed on a sample stage with the cross-section facing downward, and a plunger is so set as to penetrate into a highest portion of the strawberry, where the wedge-shaped plunger with a width of 30 (mm)×30° is used. The frozen strawberry has a crushing load of 2000 to 10000 g and a deformation strain rate of 8 to 18% under conditions of a measurement speed of 2 mm / s, a compressive strain rate of 90% and a temperature of -16 to -18°C.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to frozen strawberries that are not too sweet, have a moderate hardness, and have a light and crisp texture even when eaten in a frozen state, and to a method for producing the same. [Background technology]

[0002] In recent years, demand for frozen foods has increased due to their convenience, the ability to be eaten whenever desired, and their long-term storage, which helps reduce food waste. While traditional frozen foods were primarily consumed after cooking or thawing, fruits and sweets that can be eaten frozen have recently been developed. Because frozen fruits have a high water content, ice crystals form within the fruit when frozen, making them hard and significantly impairing their texture. For this reason, attempts have been made to prevent the fruit from freezing by impregnating the fruit with sugars or alcohol, thereby lowering its freezing point. However, this method is insufficient, and when people try to eat frozen fruit, it is too hard to bite into and has a poor texture.

[0003] To address these issues, for example, Patent Document 1 discloses frozen strawberries with a soft, chewable texture despite being frozen by controlling the breaking load and strain rate within specific ranges. The method for producing the frozen strawberries includes a heating step in which fresh strawberries are heated in water at 70°C to 100°C for 1 second to 180 seconds, a sugar-soaking step in which the heated strawberries are immersed in a sugar solution at 0°C to 20°C for 32 hours to 7 days, and a freezing step in which the strawberries are frozen after the sugar-soaking step. However, the resulting frozen strawberries are sticky in the frozen state and lack a crisp texture. Furthermore, in the examples, the sugar concentration in the sugar-soaking step is as low as 45% by mass, and the soaking time is as short as 32 hours, resulting in an overly sweet taste that is completely different from fresh strawberries. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2020-178606 Summary of the Invention [Problem to be solved by the invention]

[0005] To provide frozen strawberries which are not too sweet, have a moderate hardness and a crispy texture even when eaten in a frozen state, and a method for producing the same. [Means for solving the problem]

[0006] As a result of extensive research to solve the above problems, the inventors discovered that frozen strawberries prepared so that the crushing load and deformation strain rate measured under specific conditions fall within specific ranges are not too sweet, have a moderate hardness, and a crisp texture even when eaten in a frozen state, and have completed the present invention.

[0007] That is, the first aspect of the present invention relates to frozen strawberries that have been measured using a texture analyzer ("TA.XT PLUS" manufactured by STABLE MICRO SYSTEMS) by placing a strawberry cut in half lengthwise on a sample stage with the cross section facing downwards and inserting a plunger into the highest part of the strawberry. A wedge-shaped plunger measuring 30 mm wide x 30° is used, and the measurement speed is 2 mm / s, the compression strain rate is 90%, and the crushing load is 2000 to 10000 g at a temperature of -16 to -18°C, and the deformation strain rate is 8 to 18%. A preferred embodiment of the present invention relates to the frozen strawberries with a Brix of 12 to 17%. The second aspect of the present invention relates to frozen strawberries that have been measured using a texture analyzer ("TA.XT PLUS" manufactured by STABLE MICRO SYSTEMS) by inserting a plunger into the highest part of the strawberry. A method for producing frozen strawberries in a frozen strawberry tester ("Frozen Strawberry Tester"), in which a strawberry cut in half lengthwise is placed on a sample stage with its cross section facing downwards, and a plunger is set so as to penetrate the highest part of the strawberry, the plunger is wedge-shaped and 30 mm wide x 30°, the measurement speed is 2 mm / s, the compression strain rate is 90%, and the crushing load is 2000 to 10000 g and the deformation strain rate is 8 to 18% under conditions of a temperature of -16 to -18°C, and the strawberries are immersed in an acid solution of pH 1 to 3 at 5 to 25°C for 30 to 100 minutes. a method for producing frozen strawberries, the method comprising: soaking 100 parts by weight of the washed strawberries in 80 to 120 parts by weight of a sugar solution containing 20 to 35% by dry weight of sugars and 0.00002 to 0.005% by dry weight of an antifreeze substance at 3 to 25°C for 10 to 40 hours; flash-freezing the strawberries after soaking in the sugar solution; and storing the flash-frozen strawberries at -60 to -15°C for 1 to 450 days. A preferred embodiment relates to the method for producing frozen strawberries, wherein the sugar is at least one selected from the group consisting of fructose, glucose, and sucrose, and the antifreeze substance is an extract derived from a basidiomycete and / or an extract of a plant belonging to the Brassicaceae family. [Effects of the Invention]

[0008] According to the present invention, frozen strawberries that are not too sweet, have a moderate hardness, and have a light texture even when eaten in a frozen state, and a method for producing the same can be provided. DETAILED DESCRIPTION OF THE INVENTION

[0009] The present invention will be described in further detail below. The frozen strawberries according to the embodiment of the present invention are characterized by having a crushing load and deformation strain rate measured under specific conditions within specific ranges, and by having a crisp texture, without being too sweet, with a moderate hardness, even when eaten in a frozen state. Note that a crisp texture means a texture that is easy to bite into and without unpleasant stickiness.

[0010] The crushing load is a value measured using a texture analyzer ("TA.XT PLUS" manufactured by STABLE MICRO SYSTEMS) by placing a strawberry cut in half lengthwise on a sample stage with the cross section facing downwards and placing the plunger so that it penetrates the highest part of the strawberry, using a wedge-shaped plunger with a width of 30 mm and an angle of 30°, at a measurement speed of 2 mm / s, a compression strain rate of 90%, and a temperature of -16 to -18°C. Note that a strawberry cut in half lengthwise refers to a strawberry cut in half in the direction passing through the flower stalk and core of the strawberry.

[0011] The crushing load of the frozen strawberries is preferably 2000 to 10000 g, more preferably 3000 to 7000 g, and even more preferably 4000 to 6000 g. If the crushing load is less than 2000 g, the strawberries may be too soft and not have a crisp texture. If the crushing load is more than 10000 g, the strawberries may be too hard and difficult to bite into.

[0012] The deformation rate is a value obtained when measured under the same conditions as the crushing load, and is calculated as (H2 / H1) × 100 (%), where (H1) is the height of the strawberry before measurement in mm and (H2) is the distance the plunger pushed in during compression deformation in mm. The deformation rate is preferably 8 to 18%, more preferably 8 to 14%, and even more preferably 8 to 12%. If the deformation rate is less than 8%, the strawberry may be too hard to bite into, and a crispy texture may not be obtained. If the deformation rate exceeds 18%, the strawberry may become sticky, and a crispy texture may not be obtained.

[0013] The variety of strawberry used for the frozen strawberries is not particularly limited as long as it can be adjusted to fall within the range of the crushing load and deformation strain rate, and examples include domestic strawberries such as Yayoihime, Amaou, Tochiotome, Tochiaika, Sagahonoka, Nyoho, Toyonoka, Benihoppe, Yumenoka, Sachinoka, Niko Niko Berry, Kirapika, Sakuramomo Ichigo, Sanukihime, Shiroichigo, Summer Princess, Summer Lyrical, and Pechka, as well as strawberries from overseas countries such as the United States, China, Turkey, Mexico, Egypt, and Spain. From the viewpoint of texture, the size of the strawberries is preferably medium to 2L size (10 to 28 g / each), and more preferably medium to large size (10 to 20 g / each).

[0014] From the perspective of sweetness, the frozen strawberries preferably have a Brix of 12 to 17%, more preferably 13 to 16%, and even more preferably 15 to 16%. By adjusting the Brix to within the above range, frozen strawberries with a better balance of sweetness and sourness, similar to the sweetness of high-quality strawberries, can be obtained. The Brix can be measured using a sugar refractometer (ATAGO Co., Ltd. "RX-5000").

[0015] The pH of the frozen strawberries is preferably 3 to 3.7, more preferably 3 to 3.4, and even more preferably 3 to 3.3. By adjusting the pH to within the above range, frozen strawberries can be obtained that have a more natural strawberry sourness. The pH can be measured by thoroughly blending five frozen strawberries in a blender and measuring the resulting strawberry juice using a glass electrode hydrogen ion concentration indicator (HORIBA, Ltd.'s "LAQUA F-71").

[0016] The following is an example of a method for producing the frozen strawberries. Specifically, the strawberries can be produced by soaking them in an acid solution, washing them with water, soaking them in a sugar solution, flash-freezing them, and storing them frozen. Details of each step are explained below, but the method for producing frozen strawberries is not limited to the following description.

[0017] (Immersion in an acid solution) First, the strawberries to be used for the frozen strawberries are soaked in an acid solution to obtain acid-soaked strawberries. The pH of the acid solution is preferably 1 to 3, more preferably 1 to 2, even more preferably 1 to 1.8, and particularly preferably 1.3 to 1.8. If the pH is less than 1 or more than 3, the crisp texture of the frozen strawberries may be lost. It is preferable to remove the stems from the strawberries and wash them with water before soaking them in the acid solution.

[0018] The acid that can be used in the acid solution is not particularly limited as long as it is edible, and examples thereof include organic acids such as citric acid, gluconic acid, succinic acid, tartaric acid, lactic acid, fumaric acid, malic acid, adipic acid, phosphoric acid, phytic acid, and acetic acid; and inorganic acids such as phosphoric acid and hydrochloric acid. From the viewpoints of flavor and safety, citric acid and dilute hydrochloric acid are preferred, and citric acid is more preferred.

[0019] The temperature of the acid solution during the acid immersion is preferably 5 to 25° C., more preferably 10 to 20° C., and even more preferably 15 to 20° C. The time for the acid immersion is preferably 30 to 100 minutes, more preferably 30 to 60 minutes, even more preferably 30 to 50 minutes, and particularly preferably 30 to 40 minutes. If the temperature or time is outside the above ranges, the crispy texture of the frozen strawberries may be inferior.

[0020] From the viewpoint of hygiene of the final frozen strawberries, it is preferable to sterilize the washed strawberries with hypochlorous acid water, sodium hypochlorite solution, or the like before immersing them in the acid solution.

[0021] (Wash with water) The strawberries after soaking in the acid solution are then washed to obtain washed strawberries. Washing can be carried out at a temperature of, for example, 5 to 30°C, and is preferably continued until no residual acid is detected. Specifically, the strawberries after soaking in the acid solution are thoroughly drained, placed in a bowl, and washed with running water for 5 minutes until the pH of the water in the bowl reaches 6 to 8.

[0022] (Immersion in sugar solution) The washed strawberries are then immersed in a sugar solution containing sugars and an antifreeze agent to obtain immersed strawberries. The sugars are not particularly limited as long as they are edible, and examples include white sugar, sucrose, lactose, glucose, fructose, granulated sugar, maltose, powdered sugar, liquid sugar, isomerized sugar, invert sugar, enzyme-saccharified starch syrup, isomerized liquid sugar, sucrose-bound starch syrup, reduced starch syrup, fructooligosaccharides, soybean oligosaccharides, galactooligosaccharides, lactofructose oligosaccharides, raffinose, lactulose, and palatinose oligosaccharides, as well as sugar alcohols such as sorbitol, trehalose, xylose, xylitol, maltitol, erythritol, and mannitol. Among the sugars, it is preferable to use at least one selected from the group consisting of fructose, glucose, and sucrose, from the viewpoint of sweetness.

[0023] The sugar content is preferably 20 to 35% by dry weight, more preferably 22 to 32% by weight, and even more preferably 25 to 30% by weight, of the total sugar solution. If the sugar content is less than 20% by weight, the frozen strawberries may be too hard or have a strong sour taste. If the sugar content exceeds 35% by weight, the frozen strawberries may be too sweet.

[0024] The antifreeze substance refers to a substance that has the function of inhibiting the growth of ice crystals and contributes to maintaining the quality of various processed foods containing water during frozen storage. Examples of such substances include extracts derived from vegetables (including mushrooms), fish, yeast, etc., and from the standpoint of ease of availability, extracts derived from basidiomycetes and / or extracts of plants belonging to the Brassicaceae family are preferred, with extracts derived from basidiomycetes being more preferred.

[0025] The content of the antifreeze substance in the total sugar solution is preferably 0.00002 to 0.005% by dry weight, more preferably 0.00005 to 0.002% by weight, and even more preferably 0.00008 to 0.001% by weight. If the content of the antifreeze substance is less than 0.00002% by weight, frozen strawberries may not have a crispy texture. If the content exceeds 0.005% by weight, the effect may plateau.

[0026] The pH of the sugar solution is preferably 3 to 8, more preferably 5 to 7.5, and even more preferably 6 to 7, in terms of texture and sweetness.

[0027] When soaking strawberries in the sugar solution, the amount of sugar solution is preferably 80 to 120 parts by weight, more preferably 90 to 110 parts by weight, per 100 parts by weight of strawberries. If the amount of sugar solution is less than 80 parts by weight, the soaking of strawberries in the sugar solution may be inconsistent. If the amount of sugar solution is more than 120 parts by weight, the amount of sugar solution may be too much for the strawberries, which may increase production costs and reduce productivity.

[0028] The soaking time in the sugar solution is preferably 10 to 40 hours, more preferably 12 to 36 hours, even more preferably 15 to 32 hours, and particularly preferably 18 to 28 hours. If the soaking time is less than 10 hours, the frozen strawberries may be too hard or have a strong sour taste. If the soaking time exceeds 40 hours, the frozen strawberries may become too sweet.

[0029] The temperature at which the strawberries are soaked in the sugar solution is preferably 3 to 25° C., more preferably 5 to 20° C., even more preferably 5 to 15° C., and particularly preferably 5 to 10° C. If the soaking temperature is outside the range of 3 to 25° C., the crispy texture of the frozen strawberries may be impaired.

[0030] (Flash-freeze) The strawberries immersed in the sugar solution are then rapidly frozen to obtain rapidly frozen strawberries. Rapid freezing refers to a method of freezing at a cooling rate that causes the product temperature to pass through a temperature range of -5 to -1°C within 30 minutes. For example, the strawberries can be stored in a rapid freezer set to -30°C for 90 minutes.

[0031] (Keep frozen) The quick-frozen strawberries can be stored at -60 to -15°C for 1 to 450 days to obtain the frozen strawberries according to an embodiment of the present invention. The temperature for the frozen storage is preferably -45 to -20°C, more preferably -30 to -20°C. If the freezing temperature is lower than -60°C, the amount of utilities (equipment that supplies electricity, fuel, water, and other necessary equipment for freezing) used will increase, which may increase production costs. Furthermore, if the temperature is higher than -15°C, the quality of the frozen strawberries may deteriorate, resulting in a loss of their crispy texture and a loss of the original strawberry flavor.

[0032] The frozen strawberries may be eaten as they are in the frozen state, or may be used in a variety of foods such as frozen desserts, frozen cakes, strawberry sauces, and strawberry jams.

[0033] Examples of the frozen desserts include ice creams defined by JAS (Japanese Agricultural Standards) as ice cream (milk solids 15% or more, milk fat 8% or more), ice milk (milk solids 8% or more, milk fat 3% or more), and lacto ice (milk solids 3% or more, no milk fat content restrictions), as well as ice creams known as popsicles, shaved ice, cracked ice, sherbet, etc. Methods for using the composition in frozen desserts include, for example, adding the composition to the frozen dessert or topping it on top of the dessert.

[0034] The frozen cake may be used as a topping for a frozen cake to be eaten after thawing or for sandwiches, and frozen strawberries may be thawed and used in a cake in the same manner. [Example]

[0035] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples. In the examples, "parts" and "%" are by weight.

[0036] The materials used in the examples and comparative examples are as follows. 1) "New Fract R30" manufactured by Showa Sangyo Co., Ltd. (Fructose content: 42% by weight, Glucose content: 2% by weight, Sucrose content: 30% by weight, Moisture content: 26% by weight) 2) "Fruitose" manufactured by Garam Co., Ltd. (Fructose content: 99.5% by weight, Moisture content: 0.5% by weight) 3) "Citric acid (crystalline)" manufactured by Iwata Chemical Industry Co., Ltd.

[0037] <Measurement of crushing load and deformation strain rate> Using a texture analyzer ("TA.XT PLUS" manufactured by STABLE MICRO SYSTEMS), a strawberry cut vertically in half was placed on the sample stage with the cross-section facing down, and the plunger was installed so that it penetrated the highest part. A wedge-shaped plunger with a width of 30 mm and an angle of 30° was used, and the measurement was performed at a measurement speed of 2 mm / s, a compression strain rate of 90%, and a temperature of -16 to -18°C.

[0038] <Measurement of breaking load and breaking strain rate> Based on Japanese Patent Application Laid-Open No. 2020-178606 The measurement was performed using a texture analyzer ("TA.XT PLUS" manufactured by STABLE MICRO SYSTEMS). Also, a cylindrical plunger with a diameter of 0.5 inches (model number: P / 0.5R) was used. The measurement was performed at a measurement speed of 2 mm / sec and a compression strain rate of 80% at a temperature of -16 to -18°C. The strawberry was cut vertically in half and placed on the sample stage with the cross-section facing down, and the measurement was performed so that the plunger penetrated the highest part.

[0039] <Measurement of Brix> Five frozen strawberries were thoroughly stirred with a blender, and the resulting strawberry juice was measured using a sugar refractometer (Atago Co., Ltd. "RX-5000") five times in total, and the average value was used to obtain the result.

[0040] <Measurement of pH of frozen strawberries> Five frozen strawberries were thoroughly stirred with a blender, and the resulting strawberry juice was measured using a glass electrode type hydrogen ion concentration indicator (Horiba, Ltd. "LAQUA F-71").

[0041] <Sensory evaluation of frozen strawberries> Ten experienced panelists were asked to take each of the frozen strawberries obtained in the Examples and Comparative Examples out of a -20°C freezer and eat them immediately. They then conducted a sensory evaluation of each strawberry in terms of firmness, crispness, and sweetness, and the average scores are shown in each table as the sensory evaluation score. The evaluation criteria were as follows:

[0042] (Hardness) 5 points: Better than Example 1, moderate hardness and extremely good 4 points: Equivalent to Example 1, not too hard or too soft, good hardness 3 points: Slightly inferior to Example 1, slightly hard or slightly soft, but no problem with marketability 2 points: Worse than Example 1, hard or soft, and has marketability issues 1 point: Clearly worse than Example 1, too hard or too soft, completely unsuitable for sale

[0043] (Crispy texture) 5 points: Better than Example 1, very crispy texture 4 points: Equivalent to Example 1, with a crispy texture 3 points: Slightly inferior to Example 1, slightly hard or slightly soft, but with a crisp texture 2 points: Worse than Example 1, hard or soft, not very crispy texture 1 point: Clearly worse than Example 1, very hard or very soft, no crispy texture at all

[0044] (sweetness) 5 points: Better than Example 1, moderately sweet and extremely good 4 points: Equivalent to Example 1, not too sweet or too sour, and has a good sweetness 3 points: Slightly inferior to Example 1, slightly sweet or slightly sour, but no problem with marketability 2 points: Worse than Example 1, with a strong sweetness or sourness, and problems with marketability 1 point: Clearly worse than Example 1, too sweet or too sour, completely unmarketable

[0045] (comprehensive evaluation) An overall evaluation was made based on the evaluation results of hardness, crispy texture, and sweetness. The evaluation criteria were as follows: A: Hardness, crispy texture, and sweetness all meet the criteria of 4.0 to 5.0 points. B: Hardness, crispy texture, and sweetness are all rated at 3.5 to 5.0 points, with at least one being rated at 3.5 to 4.0 points. C: Hardness, crispy texture, and sweetness are all rated at 3.0 to 5.0 points, with at least one being rated at 3.0 to 3.5 points. D: Hardness, crispy texture, and sweetness are all rated at 2.0 to 5.0 points, with at least one being rated at 2.0 to 3.0 points. E: At least one of the following evaluations was less than 2.0 points: hardness, crispy texture, and sweetness

[0046] (Production Example 1) Production of antifreeze substance (basidiomycete-derived extract) 9.1 parts by weight (wet weight) of commercially available enokitake mushrooms were extracted with 90.9 parts by weight of a 15 wt% aqueous potassium hydroxide solution at 100°C for 2 hours. After filtering using a filter paper (manufactured by Advantec), the collected filtrate was concentrated under reduced pressure using an ultrafiltration concentrator (manufactured by Advantec, model number: UHP-150) to obtain approximately 48.5 parts by weight of a concentrate. This was centrifuged at 10,000 × g for 10 minutes to recover a supernatant with a solids concentration of 1.5 mg / ml. This supernatant was used as an antifreeze substance (enokitake mushroom extract).

[0047] (Production Example 2) Production of antifreeze substance (extract of plants belonging to the Brassicaceae family) 770 g (wet weight) of commercially available radish sprouts (Murakami Farm) was added to 2.5 L of distilled water and extracted at 100°C for 1 hour. After filtering using filter paper (Advantec), the collected filtrate was concentrated under reduced pressure using an ultrafiltration concentrator (Advantec, model number UHP-150) to obtain approximately 200 mL of concentrate. This was centrifuged at 10,000 × g for 10 minutes to collect a supernatant with a solids concentration of 0.7 mg / mL. This supernatant was used as an antifreeze substance (radish sprouts extract).

[0048] (Example 1) Production of frozen strawberries Fresh strawberries (American variety, medium size) were washed with 0.01% hypochlorous acid solution, the stems removed, and then immersed in a citric acid solution (pH 1.5) at 20°C for 40 minutes. One hundred parts by weight of the immersed, rinsed strawberries and 100 parts by weight of a sugar solution containing 30% sugar by dry weight (a mixture of 40.5 parts by weight of isomerized liquid sugar, 0.067 parts by weight of antifreeze agent (Production Example 1), and 59.5 parts by weight of water) adjusted to 20°C were placed in a plastic bag and stored at 5°C for 24 hours (strawberries immersed in the sugar solution). The water from the immersed strawberries was drained, laid flat in a plastic bag, and then flash-frozen in a -30°C flash freezer for 90 minutes. The frozen strawberries were then stored at -20°C for 30 days to obtain frozen strawberries. The crushing load, deformation strain rate, breaking load, breaking strain rate, Brix and pH of the resulting frozen strawberries, as well as the results of the sensory evaluation, are shown in Table 1.

[0049] [Table 1]

[0050] (Examples 2-3, Comparative Examples 1-2) Production of frozen strawberries Frozen strawberries were obtained in the same manner as in Example 1, except that the pH of the acid solution was changed to 1.0 (Example 2), 3.0 (Example 3), 0.5 (Comparative Example 1), or 4.0 (Comparative Example 2) according to the formulation in Table 1. The crushing load, deformation strain rate, breaking load, breaking strain rate, Brix, and pH measurements of the obtained frozen strawberries, as well as the results of the sensory evaluation, are shown in Table 1.

[0051] (Example 4, Comparative Example 3) Production of frozen strawberries Frozen strawberries were obtained in the same manner as in Example 1, except that the acid solution immersion temperature was changed to 10°C (Example 4) or 30°C (Comparative Example 3) according to the formulation in Table 1. The crushing load, deformation strain rate, breaking load, breaking strain rate, Brix, and pH measurements of the obtained frozen strawberries, as well as the results of the sensory evaluation, are shown in Table 1.

[0052] (Examples 5 to 6, Comparative Example 4) Production of frozen strawberries Frozen strawberries were obtained in the same manner as in Example 1, except that the immersion time in the acid solution was changed to 30 minutes (Example 5), 60 minutes (Example 6), or 180 minutes (Comparative Example 4) according to the formulation in Table 1. The crushing load, deformation strain rate, breaking load, breaking strain rate, Brix, and pH measurements of the obtained frozen strawberries, as well as the results of the sensory evaluation, are shown in Table 1.

[0053] (Example 7) Production of frozen strawberries Frozen strawberries were obtained in the same manner as in Example 1, except that the type of acid in the acid solution was changed to hydrochloric acid according to the formulation in Table 1. The crushing load, deformation strain rate, breaking load, breaking strain rate, Brix, and pH measurements of the obtained frozen strawberries, as well as the results of the sensory evaluation, are shown in Table 1.

[0054] (Comparative Example 5) Production of frozen strawberries Frozen strawberries were obtained in the same manner as in Example 1, except that they were not soaked in a sugar solution, according to the manufacturing method in Table 1. The crushing load, deformation strain rate, breaking load, breaking strain rate, Brix, and pH of the obtained frozen strawberries were measured, as well as the results of a sensory evaluation, and are shown in Table 1.

[0055] As is clear from Table 1, the frozen strawberries (Examples 1 to 7) obtained by immersing strawberries in acid solutions of pH 1 to 3 at 5 to 25°C for 30 to 100 minutes all had a crushing load of 2000 to 10,000 g and a deformation strain rate in the range of 8 to 18%, and the evaluation results for hardness, crisp texture, and sweetness were good.

[0056] On the other hand, frozen strawberries obtained by immersion in a low-pH acid solution of 0.5 (Comparative Example 1) and frozen strawberries obtained by immersion in a high-pH acid solution of 4.0 (Comparative Example 2) both had large distortion rates and poor crispness evaluation results, resulting in an overall rating of D or E. Furthermore, frozen strawberries obtained by immersion in an acid solution at a high temperature of 30°C (Comparative Example 3) had a large distortion rate of 18.4%, poor crispness evaluation results, and an overall rating of D. Furthermore, frozen strawberries obtained by immersion in an acid solution for a long period of 180 minutes (Comparative Example 4) had a slightly sour taste, a large distortion rate of 20.0%, poor crispness evaluation results, and an overall rating of D. Additionally, frozen strawberries obtained without immersion in an acid solution (Comparative Example 5) had a large distortion rate of 20.6%, poor crispness evaluation results, and an overall rating of E.

[0057] (Example 8, Comparative Examples 6 and 7) Production of frozen strawberries Frozen strawberries were obtained in the same manner as in Example 1, except that the sugar content of the sugar solution was changed to 21.6% by weight (Example 8), 14.4% by weight (Comparative Example 6), or 50.4% by weight (Comparative Example 7) according to the formulation in Table 2. The crushing load, deformation strain rate, breaking load, breaking strain rate, Brix, and pH measurements, as well as the results of the sensory evaluation, of the obtained frozen strawberries are shown in Table 2.

[0058] [Table 2]

[0059] (Example 9) Production of frozen strawberries Frozen strawberries were obtained in the same manner as in Example 1, except that the antifreeze substance (Production Example 1) in the sugar solution was replaced with the antifreeze substance (Production Example 2) and the amount of antifreeze substance and water added were changed according to the formulation in Table 2. The crushing load, deformation strain rate, breaking load, breaking strain rate, Brix, and pH measurements of the obtained frozen strawberries, as well as the results of the sensory evaluation, are shown in Table 2.

[0060] (Comparative Example 8) Production of frozen strawberries Frozen strawberries were obtained in the same manner as in Example 1, except that no antifreeze substance (Production Example 1) was added to the sugar solution, according to the formulation in Table 2. The crushing load, deformation strain rate, breaking load, breaking strain rate, Brix, and pH of the obtained frozen strawberries were measured, as well as the results of a sensory evaluation, and are shown in Table 2.

[0061] (Example 10) Production of frozen strawberries Frozen strawberries were obtained in the same manner as in Example 1, except that the sugar solution soaking temperature was changed from 5°C to 20°C and the soaking time was changed from 24 hours to 12 hours according to the production conditions in Table 2. The crushing load, deformation strain rate, breaking load, breaking strain rate, Brix, and pH measurements of the obtained frozen strawberries, as well as the results of the sensory evaluation, are shown in Table 2.

[0062] (Example 11, Comparative Example 9) Production of frozen strawberries Frozen strawberries were obtained in the same manner as in Example 1, except that the soaking time in the sugar solution was changed from 24 hours to 36 hours (Example 11) or 2 hours (Comparative Example 9) according to the production conditions in Table 2. The crushing load, deformation strain rate, breaking load, breaking strain rate, Brix, and pH measurements of the obtained frozen strawberries, as well as the results of the sensory evaluation, are shown in Table 2.

[0063] As is clear from Table 2, the frozen strawberries (Examples 1, 8 to 11) obtained by immersing strawberries in a sugar solution containing 20 to 35% by dry weight of sugars and 0.00002 to 0.005% by dry weight of antifreeze substances at 3 to 25°C for 10 to 40 hours had a crushing load of 2000 to 10,000 g and a deformation strain rate of 8 to 18%, and were evaluated as having good hardness, crispy texture, and sweetness.

[0064] On the other hand, frozen strawberries obtained by immersion in a sugar solution with a low sugar content (dry weight) of 14.4% by weight (Comparative Example 6) had a large crushing load of 10,765 g, a hard texture, and poor evaluation results for hardness and sweetness, resulting in an overall rating of E. Frozen strawberries obtained by immersion in a sugar solution with a high sugar content (dry weight) of 50.4% by weight (Comparative Example 7) had a large deformation strain rate of 30.8%, a sticky texture, and poor evaluation results for crisp texture and sweetness, resulting in an overall rating of E.

[0065] Furthermore, frozen strawberries obtained by immersion in a sugar solution without added antifreeze (Comparative Example 8) had a large deformation strain of 21.8%, a sticky texture, and a poor evaluation result in terms of crispness, resulting in an overall rating of D. In addition, frozen strawberries obtained by immersion in the sugar solution for a short time of 2 hours (Comparative Example 9) had a large crushing load of 12,387 g, a hard texture, and poor evaluation results in terms of hardness and sweetness, resulting in an overall rating of E.

[0066] (Examples 12 to 15) Production of frozen strawberries Frozen strawberries were obtained in the same manner as in Example 1, except that the strawberry variety was changed to Benihoppe (Example 12), Sanukihime (Example 13), Tochiotome (Example 14), or Summer Lyrical (Example 15) according to the formulations in Table 3, and the soaking time was further changed from 24 hours to 12 hours for Examples 12 to 14. The measurement results of the crushing load, deformation strain rate, breaking load, breaking strain rate, Brix and pH of the obtained frozen strawberries, as well as the results of the sensory evaluation, are shown in Table 3.

[0067] [Table 3]

[0068] As is clear from Table 3, regardless of the strawberry variety, the frozen strawberries (Examples 1, 12-15) obtained by immersion in an acid solution of pH 1 to 3 at 5 to 25°C for 30 to 100 minutes and in a sugar solution containing 20 to 35% by dry weight of sugars and 0.00002 to 0.005% by dry weight of antifreeze substance in the total sugar solution at 3 to 25°C for 10 to 40 hours all had a crushing load of 2000 to 10,000 g and a deformation strain rate in the range of 8 to 18%, and the evaluation results for firmness, crisp texture, and sweetness were all good.

[0069] (Comparative Example 10) Production of frozen strawberries Frozen strawberries were obtained in the same manner as in Example 1, except that the soaking in the acid solution and the soaking in the sugar solution were not performed according to the conditions in Table 3. The crushing load, deformation strain rate, breaking load, breaking strain rate, Brix, and pH measurements of the obtained frozen strawberries, as well as the results of the sensory evaluation, are shown in Table 3.

[0070] (Comparative Example 11) Production of frozen strawberries Frozen strawberries were obtained in the same manner as in Example 1, except that they were not immersed in a sugar solution, according to the conditions in Table 3. The crushing load, deformation strain rate, breaking load, breaking strain rate, Brix, and pH of the obtained frozen strawberries were measured, as well as the results of a sensory evaluation, and are shown in Table 3.

[0071] As is clear from Table 3, both the frozen strawberries that were not soaked in an acid solution or a sugar solution (Comparative Example 10) and the frozen strawberries that were not soaked in a sugar solution (Comparative Example 11) had a high crushing load and a hard texture, and were poor in the evaluation results for hardness and sweetness, earning an overall rating of E.

[0072] (Comparative Example 12) Production of frozen strawberries (based on Example 6 of JP 2020-178606 A) Fresh strawberries (American variety, medium size) were de-stemmed and washed with water. They were then heated in a water bath at 85°C for 60 seconds and then cooled in water for 1 minute. 100 parts by weight of the heated strawberries and 80 parts by weight of a sugar solution (45.0 parts by weight of fructose, 0.3 parts by weight of citric acid, and 54.7 parts by weight of water) containing 44.5% sugar by dry weight, preheated to 20°C, were placed in a plastic bag and stored at 5°C for 32 hours (strawberries were immersed in the sugar solution). The water from the immersed strawberries was drained, laid flat in a plastic bag, and then flash-frozen in a deep freezer at -30°C for 90 minutes. After storage at -20°C for 30 days, frozen strawberries were obtained. Measurements of the crushing load, deformation strain, breaking load, breaking strain, Brix, and pH of the resulting frozen strawberries, as well as sensory evaluation results, are shown in Table 3.

[0073] (Comparative Example 13) Production of frozen strawberries (based on Example 6 of JP 2020-178606 A) Frozen strawberries were obtained in the same manner as in Comparative Example 12, except that the strawberry variety was changed from American to Tochiotome according to the formulation in Table 3. The crushing load, deformation strain rate, breaking load, breaking strain rate, Brix, and pH measurements, as well as the results of the sensory evaluation, of the obtained frozen strawberries are shown in Table 3.

[0074] (Comparative Example 14) Production of frozen strawberries (based on Example 7 of JP 2020-178606 A) Frozen strawberries were obtained in the same manner as in Comparative Example 12, except that the soaking time in the sugar solution was changed from 32 hours to 48 hours according to the conditions in Table 3. The crushing load, deformation strain rate, breaking load, breaking strain rate, Brix, and pH measurements of the obtained frozen strawberries, as well as the results of the sensory evaluation, are shown in Table 3.

[0075] As is clear from Table 3, all of the frozen strawberries (Comparative Examples 12 to 14) produced in accordance with the examples of JP 2020-178606 A had a large deformation strain rate and a sticky texture, and the evaluation results for crispness and sweetness were poor, resulting in an overall rating of D or E.

[0076] (Comparative Example 15) Production of frozen strawberries (based on Example 1 of JP-A-06-245692) Fresh strawberries (American variety, medium size) were de-stemmed and washed with water. 100 parts by weight of the strawberries were placed in a plastic bag with 100 parts by weight of a sugar solution (a mixture of 94.5 parts by weight of isomerized liquid sugar, 0.5 parts by weight of citric acid, and 5.0 parts by weight of water) containing 70.0% sugar by dry weight. The sugar solution was adjusted to 20°C and stored at 25°C for 5 hours (strawberries were immersed in the sugar solution). The immersed strawberries were drained, laid flat in a plastic bag, and flash-frozen for 90 minutes at -30°C. After 30 days at -20°C, frozen strawberries were obtained. Table 3 shows the crushing load, deformation strain, breaking load, breaking strain, Brix, and pH of the resulting frozen strawberries, as well as the sensory evaluation results.

[0077] (Comparative Example 16) Production of frozen strawberries Frozen strawberries were obtained in the same manner as in Comparative Example 15, except that the sugar solution used for immersion was a sugar solution containing 30.0% sugar by dry weight (a mixed solution of 40.5 parts by weight of isomerized liquid sugar, 8.0 parts by weight of citric acid, and 59.5 parts by weight of water) with a pH of 2.2, and the immersion conditions were changed from 5 hours at 25°C to 24 hours at 5°C, according to the conditions in Table 3. The crushing load, deformation strain rate, breaking load, breaking strain rate, Brix, and pH measurements of the obtained frozen strawberries, as well as the results of the sensory evaluation, are shown in Table 3.

[0078] (Comparative Example 17) Production of frozen strawberries Frozen strawberries were obtained in the same manner as in Comparative Example 16, except that an antifreeze substance was added to the sugar solution according to the conditions in Table 3. The crushing load, deformation strain rate, breaking load, breaking strain rate, Brix, and pH measurements of the obtained frozen strawberries, as well as the results of the sensory evaluation, are shown in Table 3.

[0079] As is clear from Table 3, the frozen strawberries produced in accordance with the example of JP 06-245692 A (Comparative Example 15) had a high crushing load and a hard texture, and were poor in the evaluation results for hardness and sweetness, resulting in an overall rating of E. Furthermore, frozen strawberries obtained by changing the sugar concentration and pH of the sugar solution and the temperature and time of immersion in the sugar solution compared to Comparative Example 15 (Comparative Example 16), and frozen strawberries obtained by adding an antifreeze substance to the sugar solution compared to Comparative Example 16 (Comparative Example 17), both had large deformation strain rates of 18.8% and 19.5%, respectively, and had a sticky texture, with poor evaluation results for crispness, resulting in an overall rating of D.

Claims

1. Using a texture analyzer ("TA.XT PLUS" manufactured by STABLE MICRO SYSTEMS), a strawberry was cut in half lengthwise and placed on a sample stage with the cross section facing downwards, with the plunger positioned so that it penetrated the highest part of the strawberry. A wedge-shaped plunger measuring 30 mm wide x 30° was used, and the measurement speed was 2 mm / s, the compression strain rate was 90%, and the frozen strawberry had a crushing load of 2,000 to 10,000 g at a temperature of -16 to -18°C and a deformation strain rate of 8 to 18%.

2. 2. The frozen strawberries according to claim 1, wherein the Brix is ​​12 to 17%.

3. A method for producing frozen strawberries in a texture analyzer ("TA.XT PLUS" manufactured by STABLE MICRO SYSTEMS) is provided, in which a strawberry cut in half lengthwise is placed on a sample stage with its cross section facing downwards, and a plunger is set so as to penetrate the highest part of the strawberry, the plunger being wedge-shaped with a width of 30 mm and an angle of 30°, the measurement speed being 2 mm / s, the compression strain rate being 90%, and the crushing load at a temperature of -16 to -18°C being 2,000 to 10,000 g, and the deformation strain rate being 8 to 18%; Immersing strawberries in an acid solution having a pH of 1 to 3 at 5 to 25°C for 30 to 100 minutes; Washing the strawberries after soaking in the acid solution; 100 parts by weight of washed strawberries are soaked in 80 to 120 parts by weight of a sugar solution containing 20 to 35% by dry weight of sugars and 0.00002 to 0.005% by dry weight of an antifreeze substance at 3 to 25°C for 10 to 40 hours; Quickly freezing the strawberries after soaking in the sugar solution; and The method is characterized in that the strawberries after quick freezing are stored at -60 to -15 ° C for 1 to 450 days. How to make frozen strawberries.

4. 4. The method for producing frozen strawberries according to claim 3, wherein the sugar is at least one selected from the group consisting of fructose, glucose, and sucrose, and the antifreeze substance is an extract derived from a basidiomycete and / or an extract of a plant belonging to the Brassicaceae family.

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