JP7124488B2 - Baked sweet potato having two-layer structure and method for producing the same - Google Patents

Description

TECHNICAL FIELD The present invention relates to a two-layer baked sweet potato which is not sticky even when held in the hand and which can be eaten without staining the hand, and a method for producing the same.

In recent years, there has been an increase in the number of products in the line-up of foods that appeal to "ingredients and health." Products such as a wide variety of dried fruits, chestnut products, and potato products have been developed and the market is expanding. Among them, sweet potato (sweet potato) is particularly rich in dietary fiber and vitamin C and has high nutritional value, so that consumers are increasingly interested in it as a material with a sense of health. Products that make use of sweet potato ingredients include dried sweet potatoes, sweet potato snacks, and baked sweet potatoes.

However, making roasted sweet potatoes at ordinary homes is hardly done at present. Reasons for this include the lack of suitable cooking utensils, and the fact that cooking in a microwave oven takes a relatively long time and is complicated. Therefore, consumers often purchase and eat roasted sweet potatoes sold at retail stores such as supermarkets and specialty stores. Baked sweet potatoes sold in stores are very convenient, but they usually have a short shelf life, so there is a limit to when to buy them.

On the other hand, there are frozen products and processed retort foods that have a longer shelf life. Frozen food needs to be thawed and returned to room temperature before being eaten, so it is not possible to eat it easily when you want to eat it, it is not suitable for carrying around, and it requires freezing equipment for storage. Etc. Lack of convenience. In addition, retort pouch foods are easy to carry around because they can be eaten when you want to eat them and can be stored at room temperature. However, since the sterilization treatment is performed at high temperature and high pressure, there is a problem that water is likely to separate from the baked sweet potato and the surface becomes sticky. In view of this situation, research has been actively conducted on roasted sweet potatoes that can be stored at room temperature, have a non-sticky surface, and are easy to eat.

For example, in Patent Document 1, a raw potato with skin is heated by a method such as steaming, boiling, frying, or baking (paragraph [0020]), and the portion covered with the skin is removed from the raw potato with skin after heating. Cut so that the surface area ratio of the part consisting of the (skin part) and the cut surface (cut surface part) is 1: 1 to 2, and fluid-dry the obtained cut piece at 1 to 45 ° C. The dried piece obtained is stored in a heat-resistant container and sterilized by hot water retort.

In Patent Document 2, a step of washing and sterilizing raw potatoes with skins, a step of performing primary baking at 100 to 130 ° C. and secondary baking at 200 to 230 ° C., A step of putting it in a thermoplastic packaging material that slightly exceeds the amount of the remaining end and sealing the remaining end, steam sterilizing the baked sweet potato while it is stored in the packaging material, and then rapidly cooling the inside of the packaging material. A roasted sweet potato that can be stored for a long time at room temperature, including a step of condensing moisture and concentrating the condensation on the remaining end of the packaging material by centrifugal separation, and a step of heat-sealing the base of the remaining end and cutting off the remaining end. is described. This method involves a large number of steps and requires a special packaging material and a centrifuge, which is relatively costly and is not suitable for food processing.

Patent Document 3 describes a sweet potato obtained by dehumidifying and drying a roasted sweet potato, which has approximately the same surface hardness and internal hardness under a compressive force of 5 to 15 N and a sugar content of approximately 60% or more. ing. The sweet potato of Patent Document 3 is similar to dried sweet potato, and is not baked sweet potato.

Patent Document 4 describes a two-stage pressurized heating method in which baked sweet potato with skin is placed in a barrier heat-resistant packaging material, sealed with an inert gas exchange, heated to 100 to 105 ° C., and then rapidly heated to 123 to 130 ° C. A method for producing a sterilized roasted sweet potato that can be stored at room temperature for a long period of time is described. Although the surface of the roasted sweet potato obtained by this method is dry immediately after production, moisture seeps into the surface over time, and the surface tends to become sticky.

Patent Document 5 describes a processed sweet potato similar to roasted sweet potato, which is obtained by subjecting a raw material sweet potato having a cut surface to decompression treatment, impregnating the cut surface with sugars not derived from the sweet potato from the cut surface, and then heat-treating the sweet potato in an oven or the like. It is A roasted sweet potato-like processed sweet potato contains a relatively large amount of saccharides not derived from the sweet potato, and therefore its texture tends to differ from the actual texture of the roasted sweet potato.

Patent Documents 6 to 11 describe roasted sweet potato-like processed foods and sweet potato processed foods that are baked or frozen after molding dough containing mashed or powdered sweet potatoes as the main raw material into a predetermined shape. However, these processed foods do not have the original texture of roasted sweet potatoes because they use mashed or powdered sweet potatoes obtained by destroying the structure of the sweet potatoes.

Patent Literatures 12 and 13 describe apparatuses for baking sweet potatoes to produce roasted sweet potatoes. These roasted sweet potato production apparatuses cannot be easily installed in general households, cannot produce roasted sweet potatoes at low cost, and are not apparatuses for obtaining roasted sweet potatoes whose surface is less sticky.

Japanese Patent No. 4175448 Japanese Patent Publication No. 7-2076 Japanese Patent No. 5622888 JP-A-8-214769 JP 2005-168394 A JP-A-2001-346539 Japanese Patent No. 3275086 JP 2004-16174 A Japanese Patent Application Laid-Open No. 2002-360209 Japanese Patent Application Laid-Open No. 2002-360210 Japanese Patent Publication No. 2-43466 Patent No. 5693777 publication JP 2016-171940 A

In Patent Document 1, a cooked potato with skin has a moisture value of 43, 43, 41, 46 or 35% by weight in a skin portion (outer layer portion) having a thickness of 5 mm, and a central portion (inner layer portion) having a diameter of 5 mm. of 47, 47, 46, 47 or 46% by weight, respectively (Examples 1-5). In addition, although the preferred range of the moisture value difference between the epidermis portion and the central portion (hereinafter simply referred to as "moisture value difference") is described as 2 to 5% by weight (paragraph [0027]), Example 5 A water content difference of 11% by weight is also described. However, Patent Document 1 does not describe the moisture value of the whole cooked potato with skin.

According to the studies of the present inventors, the cooked potato with skin, which is composed of a skin part and a central part with different moisture values, suppresses the stickiness of the surface at the beginning of production, but after a long time after production, It was found that there is a tendency that the stickiness of the surface cannot be sufficiently suppressed. It is presumed that one of the reasons for this is that the water content of the whole cooked potato with skin is not adjusted to be within a predetermined range.

An object of the present invention is to provide a roasted sweet potato which can be stored at room temperature, has a non-sticky surface, can be easily eaten, and has the original flavor and texture of roasted sweet potato, using raw sweet potato as a raw material.

As a result of intensive research by the present inventors to solve the above problems, surprisingly, in baked sweet potatoes obtained by baking raw sweet potatoes, an outer layer and an inner layer having different moisture values are provided, By adjusting the difference between the moisture value of the thickness region from the outer surface of the outer layer to a predetermined thickness and the moisture value of the inner layer to 5 to 28% by weight and the total moisture value to 30 to 60% by weight, It is possible to obtain a baked sweet potato with a two-layer structure that can be stored at room temperature, has a non-sticky surface even after long-term storage, and can be easily eaten. The inventors have found that baked sweet potatoes with a dual structure having different moisture values can be easily produced, and have completed the present invention.

The present invention provides a two-layer baked sweet potato described in (1) to (3) below and a method for producing a two-layer baked sweet potato described in (4) to (5) below.

(1) Raw sweet potato raw material is dried, then baked and sterilized, wherein the raw sweet potato is a cut piece with a thickness of 10 to 30 mm, and the outer layer portion is a surface layer region including the outer surface. and an inner layer portion, which is an internal region other than the outer layer portion and has a higher moisture value than the outer layer portion, wherein the moisture value of the thickness region from the outer surface of the outer layer portion to a predetermined thickness and the moisture value of the inner layer portion A two-layer baked sweet potato, characterized by a difference of 5 to 28% by weight and a total moisture value of 30 to 60% by weight .
(2 ) A cylindrical plunger with a diameter of 2 mm is penetrated from the outer surface of the baked sweet potato into the inside at a temperature of 20 ° C. at a penetration distance of 200% and a penetration speed of 2 mm / sec. The two-layer baked sweet potato according to (1) above, wherein the outer layer weighs 100 to 2000 g and the inner layer weighs 20 to 200 g.
( 3 ) The method for producing a two-layer baked sweet potato according to (1) or (2 ) above, wherein the raw sweet potato is fluid-dried or dried under reduced pressure at a temperature of 1 to 70 ° C. to obtain a dried sweet potato with a dry surface. A method for producing a double-structured roasted sweet potato, comprising a drying step of obtaining dried sweet potato, a baking step of baking a dried sweet potato to obtain a baked sweet potato, and a sterilization step of sterilizing the baked sweet potato.
( 4 ) The method for producing a double-structured roasted sweet potato according to ( 3 ) above, further comprising a cutting step of cutting the raw sweet potato into a predetermined shape to obtain cut sweet potatoes before the drying step.

The two-layered baked sweet potato of the present invention can be stored at room temperature, has a non-sticky surface even after long-term storage, can be easily eaten, and has the original flavor and texture of the baked sweet potato. In addition, since the double-structured baked sweet potato of the present invention is rich in dietary fiber and vitamin C, it can be appealed to consumers who are highly health-conscious and can be expected to develop a new market for baked sweet potato.

BRIEF DESCRIPTION OF THE DRAWINGS It is a cross-sectional perspective view which shows typically one Embodiment of the roasted sweet potato which has a double structure of this invention.

The baked sweet potato having a two-layer structure of the present invention (hereinafter also simply referred to as "the baked sweet potato of the present invention") is made from raw sweet potatoes and consists of an outer layer portion and an inner layer portion having different moisture values. The moisture value difference is 5-28% by weight, and the total moisture value is 30-60% by weight. In the present specification, the water content (% by weight) is a value measured by a vacuum drying method.

Here, the moisture value of the outer layer part is the moisture content in the thickness region from the outer surface of the outer layer part to a predetermined thickness, preferably from the outer surface to 1 to 5 mm, more preferably from the outer surface to 2.5 to 3.5 mm. value. The reason for the change in the thickness from the outer surface of the outer layer where the moisture value is measured is that the thickness of the outer layer changes depending on the variety and production area of the sweet potato used as the raw material, the heating conditions in the drying process and baking process, etc. and so on. The outer layer portion and the inner layer portion differ in color, hardness, etc., and can be clearly distinguished by visual observation of the cross section. The inner layer has, for example, the color of the general roasted sweet potato interior, which is a mixture of a clear yellow region and a milky white region, and the outer layer has, for example, a slightly whitish color than the milky white region of the inner layer, and these boundaries are Clear. Also, the outer layer and the inner layer can be easily separated by applying a slight force while being careful not to break the structure of the roasted sweet potato. When at least part of the epidermis is separated from the outer layer, measure the moisture value of the region from the outer surface of the epidermis to a predetermined thickness while lightly pressing the epidermis against the outer layer, and measure the moisture content of the outer layer. value. The moisture value of the outer layer portion is within a predetermined range described later, regardless of whether the outer surface of the outer layer portion has a skin or not.

As described above, the baked sweet potato of the present invention comprises an outer layer and an inner layer having a higher moisture content than the outer layer. The outer layer portion is the surface layer region including the outer surface of the baked sweet potato of the present invention, and the inner layer portion is the entire inner region excluding the outer layer portion. The roasted sweet potato of the present invention has a form in which the entire outer surface is covered with the skin (skin after baked sweet potato, hereinafter the same), a form in which a part of the outer surface is covered with the skin, and a form in which the outer surface is entirely covered with the skin. It encompasses all forms. When the skin (skin after baked sweet potato) is present on the outer surface, the surface layer region including the outer surface of the skin is the outer layer portion. For example, FIG. 1 is a perspective view schematically showing a roasted sweet potato 1 having a double structure, which is produced using sliced raw sweet potatoes. The roasted sweet potato 1 is cut in half here and shown in cross section, but as a whole, it has a structure in which the entire surface of a substantially cylindrical plate-shaped inner layer 11 is covered with an outer layer 10 having substantially the same thickness.

In the present invention, the water content of the outer and inner layers and the water content of the whole are adjusted in order to suppress the surface stickiness of the roasted sweet potato. Although the exact mechanism of action for suppressing stickiness has not been sufficiently clarified at present, it is presumed as follows.

In the present invention, as described later, the drying and baking of raw sweet potatoes are performed in this order, and the drying conditions and baking conditions are adjusted to reduce the moisture value of the outer layer than the inner layer. The starch inside does not undergo alpha conversion or enzymatic decomposition reaction by β-amylase, and solidifies in the state of raw starch to form a film. In addition, it is considered that enzymatic decomposition reaction by β-amylase occurs in the inner layer part where the moisture content is maintained, and saccharification occurs in the same manner as in ordinary roasted sweet potato. As described above, it is considered that the structure of the inner layer portion and the structure of the outer layer portion are different from each other, resulting in a baked sweet potato having a two-layer structure. As a result, since a film of starch is formed on the outer layer, it is possible to prevent water from seeping out from the inner layer to the surface. Furthermore, it is presumed that the stickiness of the surface can be suppressed by controlling the baking temperature and baking time so that the total moisture content falls within the range of 30 to 55% by weight.

The moisture value of the outer layer portion, that is, the moisture value in the thickness region from the outer surface of the outer layer portion to a predetermined thickness is usually 20 to 50% by weight, preferably 25 to 50% by weight, more preferably 28 to 48% by weight. . The moisture content of the inner layer is usually 40-60% by weight, preferably 42-59% by weight, more preferably 45-58% by weight). The difference in water content between the outer layer portion and the inner layer portion is usually 5 to 28% by weight, preferably 5 to 25% by weight, more preferably 8 to 25% by weight, still more preferably 10 to 25% by weight. If the moisture value difference is less than 5% by weight, moisture derived from the roasted sweet potato seeps out from the inner layer over time, tending to make the surface sticky. If the moisture value difference is more than 25% by weight, the skin, if present in the outer layer, becomes too hard and tends to impair the texture and flavor. .

The overall moisture value is the moisture value of the roasted sweet potato of the present invention. The total moisture content is usually 30-60% by weight, preferably 33-58% by weight, more preferably 35-58% by weight. If the moisture content of the whole is less than 30% by weight, the texture of the roasted sweet potato becomes hard and loses its moist texture, and tends to deviate from the original texture and flavor of the roasted sweet potato. If the total moisture value is more than 55% by weight, the surface tends to be sticky even if the moisture value difference between the outer layer portion and the inner layer portion is within the predetermined range.

In the present invention, if the baked potato has an outer layer and an inner layer with different moisture values, the difference in moisture value between the outer layer and the inner layer is 5 to 25% by weight, and the total moisture value is 30 to 55% by weight, the thickness of the roasted sweet potato is not limited. However, 10 to 30 mm is preferable, and the size is easy to eat, and the flavor is also good.

In the present invention, when measuring the moisture value of the outer layer portion and the inner layer portion, the entire outer layer portion may be removed from the roasted sweet potato of the present invention, and the moisture value may be measured as it is. Also, the remaining inner layer portion can be used for measurement as it is. The outer layer portion and the inner layer portion can be separated relatively easily due to the difference in hardness caused by the difference in water content. Further, from the roasted sweet potato of the present invention, a plurality of samples (fragments) of a predetermined size including the outer layer and the inner layer are collected, these samples are separated into the outer layer and the inner layer, and the moisture value is measured. Each moisture value of the outer layer portion and the inner layer portion may be obtained as an average value of the values. In the roasted sweet potato of the present invention, both the outer layer portion and the inner layer portion have a substantially uniform moisture value, so the moisture value of each part of the outer layer portion and the inner layer portion is taken as the moisture value of the entire outer layer portion and the inner layer portion. Even if it is substituted, it is almost accurate.

In the baked sweet potato of the present invention, the hardness value of the outer layer portion is greater than the hardness value of the inner layer portion. The hardness of the outer layer portion and the inner layer portion can be measured using, for example, a texture analyzer (trade name: Texture Analyzer TA.XT.plus, manufactured by Stable Micro Systems). That is, a cylindrical plunger with a diameter of 2 mm is brought into contact with the outer surface of the baked sweet potato, and penetrated into the baked sweet potato at a temperature of 20 ° C. at a penetration distance of 200% and a measurement speed of 2 mm / s, and the cylindrical plunger is pressed against the baked sweet potato. The maximum value (g) when penetrating from the outer surface is the hardness of the outer layer, and the maximum value (g) when the cylindrical plunger penetrates the outer layer and then penetrates the inner layer is the hardness of the inner layer. Harden. The hardness of the inner layer portion thus measured is 100 to 2000 g, and the hardness of the inner layer portion is 20 to 200 g. When the hardness of the outer layer portion and the inner layer portion are each within the above range, it is possible to sufficiently maintain the texture that is peculiar to baked sweet potatoes, with the outside being hard and the inside being warm and moderately soft.

When the cylindrical plunger penetrates the outer layer and the inner layer in order, the measured value gradually increases and reaches a predetermined maximum value (hardness of the outer layer). A predetermined maximum value (hardness of the inner layer) is reached. Therefore, when the first maximum value is reached, the penetration into the outer layer is almost completed, and when the measured value drops, the penetration into the inner layer begins. Thus, it can be seen that the roasted sweet potato of the present invention has a double structure consisting of an outer layer portion and an inner layer portion, also from the change in the magnitude of the measured value.

The roasted sweet potato of the present invention includes, for example, a drying step, a baking step, and a sterilization step, and a first production method in which each step is performed in this order, a cutting step, a drying step, a baking step, and a sterilization step. It is manufactured by the second manufacturing method or the like in which each step is performed in this order. In the first and second manufacturing methods, the drying step, baking step, and sterilization step are the same steps. In the first and second production methods, in particular, the raw sweet potato is dried by fluid drying or reduced pressure drying, and then baked, so that each moisture value of the baked potato as the final product (moisture value of the outer layer, inner layer It is possible to adjust the moisture value of the part and the moisture value of the whole) and the moisture value difference within a predetermined range. Details of each step will be described below.

The cutting step is a step that is performed before the drying step as necessary from the viewpoint of the ease of eating and portability of the baked sweet potato of the present invention, which is the final product, and cuts the raw sweet potato into a predetermined shape. , cut to size to obtain fresh sweet potato cut pieces.

In the present invention, the raw sweet potato as a raw material is a sweet potato that has not been subjected to heat treatment such as baking, steaming, boiling, microwave cooking, etc., or homogenization treatment to make powder, paste, mash, etc. be. The raw sweet potato may be one that retains its size and shape as it is, or may be cut into pieces from the viewpoint of ease of eating and portability.

The variety of raw sweet potato used as a raw material is not particularly limited, and any conventionally known variety can be used. No. 14, Kurimasari, Beni Satsuma, Beni Azuma, Beni Haruka, Miyazaki Beni, Beni Komachi, Purple Sweet Road (Purple Sweet Potato), Quick Sweet, Hime Ayaka, Silk Sweet, Ayakomachi (Orange Potato), Tamatoyo, Izumi, Tamaotome, Aikomachi, Carrot Potato, Anno Potato, Ayamurasaki (Purple Potato), Kintoki Potato, Hoshikirari, Beni Masari, Daiei Amusume, Tanegashima Potato (Purple Potato), Beni Hayato, Kogane Sengan, Naruto Kintoki, Gorojima Kintoki, etc. Among them, Norin No. 1, Takakei No. 14, Beni Satsuma, Beni Azuma, Beni Asari, Anno Potato, Beni Komachi, Beni Haruka, and the like, which are suitable for baked sweet potato, are preferable. The baked sweet potato of the present invention can be produced using one or two or more varieties.

The method of cutting the raw sweet potato is not particularly limited as long as it is a cutting method that does not destroy the structure of the sweet potato. From the viewpoint of ease of eating and portability, a cutting method such as round slicing or half-moon slicing is preferable, and the resulting cut piece preferably has a thickness of 10 mm to 30 mm. Moreover, the raw sweet potato may be one from which at least a part of the epidermis has been removed, or one from which the epidermis has been left.

In the drying step, uncut raw sweet potatoes or cut pieces thereof are impregnated with a desired seasoning liquid, if necessary, and then dried to obtain dried sweet potatoes. Drying is carried out by fluid drying or vacuum drying at a temperature of 1-70°C. The optimum drying temperature differs depending on the drying method. Fluid drying is preferably carried out by blowing hot air of about 30 to 70° C. onto uncut raw sweet potatoes or cut pieces thereof for about 0.5 to 20 hours. The drying under reduced pressure is preferably carried out at a temperature of about 1 to 60° C. and a reduced pressure of about -1 MPa to -0.5 MPa for about 0.5 to 10 hours.

The seasoning liquid impregnated into the uncut raw sweet potato or its cut piece as needed is each moisture value of the baked potato (moisture value of the outer layer, moisture value of the inner layer, and moisture value of the whole), It may be used as long as it does not affect the effect of suppressing the stickiness of the surface when cooked, or the flavor and texture of the baked sweet potato. Examples of the liquid seasoning include sugars such as sugar, brown sugar, and sorbitol, sweeteners, organic acids, amino acids, flavorings, salts, spices, soy sauce, sake, mirin, fruit juice, vegetables, miso, and the like. A seasoning liquid adjusted to a desired flavor by using a combination of two or more types can be mentioned. In addition, for the purpose of improving quality and workability, cereals, animal and vegetable proteins, gelling agents such as gelatin and polysaccharides, color formers, pH adjusters, emulsifiers, coloring agents, preservatives, and chelating agents are used. , enzymes, etc., can be combined according to the purpose to prepare the seasoning liquid. The uncut raw sweet potato or cut pieces thereof are flavored with a seasoning liquid, for example, by immersion in the seasoning liquid, application of the seasoning liquid, or the like.

In the baking step, the dried sweet potato is preferably baked at a temperature of 150° C. or higher, more preferably 150° C. to 250° C. for about 0.5 to 5 hours (preferably about 0.5 to 2 hours). , to obtain a baked sweet potato. The baked sweet potato is substantially a roasted sweet potato. At this time, the baking temperature and the baking time are appropriately adjusted so that each moisture value (the moisture value of the outer layer portion, the moisture value of the inner layer portion, and the moisture value of the entire portion) falls within a predetermined range. The firing temperature and firing time can be easily adjusted by conducting a preliminary experiment using cut pieces having different sizes for each product type. The heating equipment for baking the dried sweet potato is not particularly limited, but equipment capable of heating in a temperature range of 150° C. or higher, such as a Dutch oven, a deck oven, a rack oven, or a tunnel oven, is preferable from the viewpoint of flavor.

The sterilization step is a step of thermally sterilizing the baked sweet potato in order to distribute the baked sweet potato as a roasted sweet potato at room temperature. The heat sterilization method is not particularly limited, and examples thereof include boiling sterilization, retort sterilization, and ultra-high pressure sterilization. In addition, heat sterilization conditions may be appropriately set depending on the sweet potato variety, size, facility capacity, sterilization method, and the like.

Next, the present invention will be described in detail with reference to Examples, but the present invention is not limited to these Examples. In the following examples and comparative examples, parts and % indicate parts by weight and % by weight, respectively, unless otherwise specified. In the following examples and comparative examples, the method for measuring the water content (%) and the method for sensory evaluation are as follows.

<Moisture value (moisture content)>
Moisture content (% by weight) was measured by a vacuum drying method.

<Measurement point of moisture value>
The moisture value (A) of the outer layer is about 3 mm from the outer surface of the baked potato (the outer surface of the skin and the outer surface of the cut surface) of the outer layer. Moisture value in the thickness region.
The moisture value (B) of the inner layer portion is the moisture value (B) of the inner region of the baked sweet potato excluding the outer layer portion.
The moisture value difference (C) is a value obtained by subtracting the moisture value (A) of the outer layer portion from the moisture value (B) of the inner layer portion.
The whole moisture value (D) is the moisture value of the whole roasted sweet potato.

Using a texture analyzer (trade name: Texture Analyzer TA.XT.plus, manufactured by Stable Micro Systems), a cylindrical plunger with a diameter of 2 mm was measured at a penetration distance of 200%, a measurement speed of 2 mm/s, and a measurement temperature of 20°C. was used for the measurement. A specific measurement method was in accordance with the manual attached to the texture analyzer. The hardness of the outer layer was the maximum value (g) when the cylindrical plunger penetrated from the outer surface. The hardness of the inner layer was defined as the maximum value (g) when the cylindrical plunger penetrated the inner layer after penetrating the outer layer.

<Sensory evaluation>
For the sensory evaluation of the baked sweet potato, five panelists evaluated the stickiness of the surface when the baked sweet potato was pinched by hand according to the following criteria, and the average value of each score of the five panelists was calculated to the first decimal place. It was rounded off and used as a score.
(Surface stickiness)
5: No stickiness at all, no stickiness even after storage at room temperature for 1 year.
4: Almost no stickiness, almost no stickiness even after storage at room temperature for 1 year.
3: Slightly sticky immediately after production 2: Sticky immediately after production 1: Quite sticky immediately after production

In addition, in the present invention, the flavor and texture of the obtained baked sweet potato were evaluated according to the following criteria, and the average value of the 10 panelists (the average value was rounded to the first decimal place) was "5" or "4". were judged to be acceptable products, and other products were judged to be unacceptable products.
5: In terms of flavor, the sweetness peculiar to sweet potato is very strong, and in terms of texture, the texture and its hardness are uniform, and it has a strong warm feeling peculiar to roasted sweet potato.
4: In terms of flavor, the sweetness peculiar to sweet potato is strong, and in terms of texture, the texture and its hardness are almost uniform, and it has a warm feeling peculiar to roasted sweet potato.
3: Although the sweet potato has a strong sweetness peculiar to sweet potatoes in terms of flavor, the structure and its hardness are slightly uneven in terms of texture, and there are regions that have a warm feeling peculiar to roasted sweet potatoes and regions that do not. exist.
2: Sweet potato peculiar to sweet potato can be felt in terms of flavor, but the structure and its hardness are uneven in terms of texture, and there are few regions having the warm feeling peculiar to roasted sweet potato.
1: In terms of flavor, the sweetness peculiar to sweet potato is weak, and in terms of texture, the structure and its hardness are uneven, and there are almost no areas with the warm feeling peculiar to roasted sweet potato.

(Example 1)
An unheated sweet potato with skin (approximately 4 cm in diameter) was sliced into 20 mm-thick slices to obtain slices weighing approximately 25 g. Then, the cut piece of sweet potato was fluid-dried with a hot air blower at 50° C. for 2 hours. After drying, the obtained dried pieces of sweet potato were baked at 200° C. for 1 hour using a convection oven. After standing to cool, the resulting baked sweet potato pieces (baked sweet potato) were filled in a retort pouch, heat-sealed, and heat-treated with hot water at 85°C for 30 minutes to obtain a baked sweet potato.

(Example 2)
An unheated sweet potato with skin (approximately 4 cm in diameter) was cut into chunks of 20 mm in thickness to obtain cut pieces weighing about 25 g. Then, the sweet potato cut pieces were fluid-dried with a hot air blower at 60° C. for 3 hours. After drying, the obtained dried pieces of sweet potato were baked at 200° C. for 1 hour using a convection oven. After standing to cool, the resulting baked sweet potato pieces (baked sweet potato) were packed in a retort pouch, heat sealed, and autoclaved at 600 MPa and 17° C. for 5 minutes to obtain a baked sweet potato product.

(Example 3)
An unheated sweet potato with skin (approximately 4 cm in diameter) was sliced into 20 mm-thick slices to obtain slices weighing approximately 25 g. Then, the cut piece of sweet potato was dried under reduced pressure at 40° C. and −0.1 MPa for 1 hour. After drying, the resulting dried pieces of sweet potato were baked at 200° C. for 4 hours using a convection oven. After standing to cool, the resulting baked sweet potato pieces (baked sweet potato) were filled in a retort pouch, heat-sealed, and heat-treated in a hot water retort at 121° C. for 25 minutes to obtain a baked sweet potato product.

(Comparative example 1)
An unheated sweet potato with skin (about 4 cm in diameter) was baked at 200° C. for 1 hour using a convection oven. After standing to cool, the baked sweet potato was sliced into 20 mm-thick slices to obtain baked sweet potato pieces weighing about 25 g. This was filled into a retort pouch, heat-sealed, and then heat-treated with hot water at 85° C. for 30 minutes to obtain a roasted sweet potato product.

(Comparative example 2)
An unheated sweet potato with skin (approximately 4 cm in diameter) was sliced into 20 mm-thick slices to obtain slices weighing approximately 25 g. Then, the cut piece of this sweet potato was fluid-dried with a hot air blower at 60° C. for 30 minutes. After drying, the obtained dried pieces of sweet potato were baked at 200° C. for 1 hour using a convection oven. After standing to cool, the resulting baked sweet potato pieces (baked sweet potato) were packed in retort pouches, heat-sealed, and autoclaved at 600 MPa and 17° C. for 5 minutes to obtain baked sweet potato products.

(Comparative Example 3)
An unheated sweet potato with skin (about 4 cm in diameter) was sliced into 20 mm-thick slices to obtain cut pieces weighing about 25 g. Then, the sweet potato cut pieces were fluid-dried with a hot air blower at 70° C. for 6 hours. After drying, the obtained dried pieces of sweet potato were baked at 200° C. for 1 hour using a convection oven. After standing to cool, the resulting baked sweet potato pieces (baked sweet potato) were filled in a retort pouch, heat-sealed, and then heat-treated with hot water at 85°C for 30 minutes to obtain a baked sweet potato product.

Table 1 shows the moisture content, hardness, surface stickiness evaluation, and flavor/texture evaluation of the baked sweet potatoes obtained in Examples 1-3 and Comparative Examples 1-3.

From the results in Table 1, it can be seen that the roasted sweet potatoes obtained in Examples 1 to 3 have no stickiness on the surface and have a flavor and texture typical of roasted sweet potatoes.

On the other hand, in Comparative Example 1, the baked sweet potato was cut after making it into a baked potato, and it was found that the surface stickiness occurred due to the small moisture value difference between the outer layer and the inner layer and the high overall moisture value. .
In Comparative Example 2, raw sweet potatoes were cut, then fluid-dried and baked. Compared to Example 1, the fluid-drying time was shortened, so the difference in moisture value between the outer layer and the inner layer was reduced. It turned out that it became small and the stickiness of the surface generate|occur|produced.
In Comparative Example 3, raw sweet potatoes were cut, then fluid-dried and baked. Compared to Example 1, the fluid-drying time was longer, so the difference in water content between the outer layer and the inner layer was is large and the overall moisture value is small, so the surface is not sticky, but the flavor is improved. I found that it tasted bad .

1 baked sweet potato having a double structure 10 outer layer 11 inner layer

Claims (4)

A roasted sweet potato obtained by drying raw sweet potatoes, then baking and sterilizing them,
The raw sweet potato is a cut piece with a thickness of 10 to 30 mm,
An outer layer portion that is a surface layer region including an outer surface, and an inner layer portion that is an inner region other than the outer layer portion and has a higher moisture value than the outer layer portion, and a predetermined thickness from the outer surface of the outer layer portion A baked sweet potato with a two-layer structure, characterized in that the difference between the moisture value of the thickness region and the moisture value of the inner layer is 5 to 28% by weight, and the moisture value of the whole is 30 to 60% by weight. A cylindrical plunger with a diameter of 2 mm is penetrated from the outer surface of the baked sweet potato into the inside at a temperature of 20 ° C. at a penetration distance of 200% and a penetration speed of 2 mm / sec. The two-layer baked sweet potato according to claim 1 , which weighs 100 to 2000 g and the inner layer weighs 20 to 200 g. A method for producing a two-layer baked sweet potato according to claim 1 or 2 ,
A drying step of fluid drying or vacuum drying the raw sweet potato at a temperature of 1 to 70 ° C. to obtain a dried sweet potato with a dry surface;
a baking step of baking the dried sweet potato to obtain a baked sweet potato;
A sterilization step of sterilizing the baked sweet potato body;
A method for producing a double-structured roasted sweet potato, comprising: 4. The method for producing a double-structured roasted sweet potato according to claim 3 , further comprising a cutting step of cutting the raw sweet potato into a predetermined shape to obtain cut sweet potatoes before the drying step.

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