JP7483229B2 - Sweet potato juice and juice - Google Patents

Description

The present invention relates to a method for producing sweet potato juice and sweet potato juice using sweet potatoes as a raw material.

Conventionally, sweet potato juice using juice obtained by squeezing juice from sweet potatoes has been known. Natural oligosaccharides contained in sweet potatoes, and colored sweet potatoes contain purple pigments such as anthocyanidins and yellow and red pigments such as maltose, maltose, and maltose.
Some contain high amounts of the orange pigment β-carotene, and are attracting attention as a food ingredient that allows easy intake of these nutrients.

Generally, pressing and centrifugation are used to separate juice from vegetables and fruits, but sweet potatoes are rich in fiber and starch, and in order to maintain an appropriate viscosity, it was necessary to effectively remove these substances while separating the juice. However, simply removing the fiber and starch by centrifugation or filtration was not enough to effectively bring out the sweetness and flavor of the sweet potatoes, and the yield also decreased.

In relation to such problems, for example, Patent Document 1 discloses a sweet potato beverage that is characterized by containing an enzymatic hydrolysis product of sweet potatoes that have been hydrolyzed using a combination of a fiber-degrading enzyme and a starch-degrading enzyme. Also, for example, Patent Document 2 discloses a method for producing sweet potatoes under conditions that substantially inactivate the polyphenol oxidase contained therein but activate amylase, so that the maltose content of the sweet potatoes is reduced to 1.
The present invention discloses a method for producing sweet potato juice, which comprises a first step of heat-treating the sweet potatoes to a concentration of 0 to 10% by weight, a second step of squeezing the heat-treated sweet potatoes to extract juice, and a third step of treating the squeezed juice fraction so as to reduce the viscosity caused by starch granules in the juice fraction.

Japanese Patent Application Laid-Open No. 9-107934 Japanese Patent Application Laid-Open No. 10-215835

According to the above-mentioned Patent Documents 1 and 2, it is said that a method utilizing enzymes for fibrous and starchy substances can produce high-quality sweet potato juice or sweet potato juice.

However, according to the research of the present inventors, it was found that it was difficult to adjust the sweetness of the sugars produced by enzymatic decomposition, and this affected the flavor when sweet potato juice was prepared.

Therefore, an object of the present invention is to provide a sweet potato juice using the juice obtained by squeezing juice from sweet potatoes, which has a moderate sweetness, and a method for producing sweet potato juice using the same.

The inventors conducted extensive research to achieve the above objective and have now completed the present invention.

That is, in a first aspect, the present invention provides a juice obtained from sweet potatoes, containing carbohydrates in an amount of 70% by mass or more and 98% by mass or less based on the total solid content, the starch content being 10% by mass or less based on the total solid content, and the glucose content being 10% by mass or less based on the total solid content.
The present invention provides a sweet potato juice characterized by the following:

The sweet potato juice preferably contains anthocyanin compounds in an amount of 0.75% by mass or more, calculated as aglycone, based on the total solid content.

The sweet potato juice preferably has a Brix value of 45 or more and 55 or less.

In a second aspect, the present invention provides a method for producing sweet potato juice, which comprises a step of mixing the above-described sweet potato juice with other raw materials.

In the above-mentioned method for producing sweet potato juice, it is preferable that the other ingredients are one or more selected from the group consisting of water, lemon juice, acidulants, and flavorings.

According to the present invention, maltotriose-producing amylase is used in the preparation of sweet potato juice,
It is possible to provide a sweet potato juice in which the content of glucose, a sweet component, among the sugars produced by starch decomposition can be reduced without causing a deterioration in flavor or nutritional components, thereby providing a sweet potato juice with a moderate sweetness.

The sweet potato juice according to the present invention has a carbohydrate content of 70% by mass to 98% by mass based on the total solid content.
A squeezed juice containing the following, wherein the starch content is 10% by mass or less based on the total solid content:
The glucose content is 10% by mass or less based on the total solid content.

There is no particular limitation on the variety of sweet potato used as the raw material. For example, it may be a commonly available product such as Beni-Azuma or Benisatsuma, or it may be a variety such as Ayamurasaki, Murasakimasari, Yamakawamurasaki, Tanegashimamurasaki, Chiranmurasaki, Kyushu 109, J-Red, which are rich in anthocyanin compounds.
The sweet potato may be a so-called colored sweet potato, such as purple sweet potato, such as Benihayato, Sunny Red, Akemurasaki, or orange sweet potato, such as Benihayato, Healthy Red, Kyushu 120, Higashiyama, etc., which are rich in carotene compounds. Among them, Ayamurasaki, which is rich in anthocyanin compounds known to have various physiological effects, is preferred.

The method for obtaining the sweet potato juice according to the present invention will be described in detail below. However, the scope of the present invention is not limited in any way by the method described below, and the sweet potato juice according to the present invention can also be obtained by other methods similar to the method described below.

In the method for obtaining sweet potato juice according to the present invention, sweet potatoes are first subjected to treatments of blanching, adding water and crushing.

By subjecting sweet potatoes to a blanching treatment, the enzymes present in the sweet potatoes can be inactivated and the starch contained in the sweet potatoes can be gelatinized. This prevents the sweet potato components from being decomposed in an uncontrolled manner, and allows for the production of squeezed juice of stable quality. Furthermore, gelatinizing the starch makes it easier to react with the enzymes, promoting efficient decomposition. The conditions for the blanching treatment are not particularly limited, and typically include, for example, steam or 90 to 1000°C.
This can be done by steaming or soaking the raw sweet potatoes in water heated to 100°C, so that the center of the raw sweet potatoes is preferably at 70°C or higher, more preferably at 75°C or higher, and processing for 5 to 30 minutes.

In addition, by subjecting sweet potatoes to a hydration treatment, the enzymatic treatment can be carried out more efficiently. The amount of water to be added is not particularly limited, and typically, for example, is preferably 0.5 to 20 times the amount of the sweet potato raw material, more preferably 1 to 10 times, and more preferably 3 to 5 times.
Six times the amount is even more preferred.

In addition, by subjecting sweet potatoes to crushing treatment, the enzyme treatment can be carried out efficiently. The crushing means is not particularly limited, and typically, for example, a hammer crusher, a mixer, a chopper, a stone mill type crusher, a cutter such as a disk cutter or a fruit cutter, or an ultra-precise high-speed crusher may be used. The degree of crushing may be arbitrarily selected, but it is preferable to crush the treated product in the above-mentioned water-added state until it has fluidity to the extent that the contents can be well mixed and dispersed. In addition, in order to allow the enzyme to act uniformly, it is desirable to select a means for crushing more finely. In addition, the term "crushing" in such a crushing process includes cases generally referred to as "crushing", "grinding", "shredding", etc.

There is no particular restriction on the order of the above-mentioned treatments of the raw materials, but from the viewpoint of work efficiency, it is preferable to carry out the blanching treatment first, and more preferably to carry out the treatments in the order of blanching, hydration, and crushing. These treatments may be carried out at the same time.

The raw sweet potato may be cut into an appropriate shape, for example, into strips of 20 to 40 mm thickness using a device such as a slicer, or into random pieces of a specified size.
Furthermore, the raw sweet potato may be peeled using a device such as a steam peeler. By subjecting the raw sweet potato to such a shape-changing process, the efficiency of preparation of the processed product obtained through at least the above-mentioned blanching, hydration, and crushing processes can be increased. The timing of subjecting the raw sweet potato to such a shape-changing process is not particularly limited, and typically may be, for example, before the above-mentioned blanching process, before the above-mentioned hydration process, or before the above-mentioned crushing process. However, if it is desired to recover components contained in the skin or the vicinity of the skin of the sweet potato, it is preferable not to perform the peeling process.

In addition, the raw sweet potatoes after the above-mentioned blanching treatment can be temporarily stored in a frozen state or the like so that they can be used for producing sweet potato juice at any other time.

In the method for obtaining sweet potato juice according to the present invention, the treated product obtained through the above-mentioned blanching, hydration and crushing treatments is subjected to an enzymatic treatment with maltotriose-forming amylase.

The maltotriose-producing amylase used in the enzymatic treatment may be an enzyme having an activity of acting on starch to produce mainly maltotriose. Specifically, it may be an enzyme having an activity of producing maltotriose using polysaccharides having an α(1→4)-glucan structure, such as amylose, amylopectin, and glycogen, as a substrate. More specifically, it may be an enzyme having an activity of producing maltotriose using glucan
1,4-α-maltotriohydrolase (EC 3.2.1.116, also known as maltotriose-forming enzyme
For example, Japanese Patent Publication No. 57-6915 discloses a maltotriose-producing amylase derived from a microorganism belonging to the genus Streptomyces griseus. Japanese Patent Publication No. 60-15315 discloses a maltotriose-producing amylase derived from a microorganism belonging to the genus Bacillus. Japanese Patent Laid-Open No. 3-251 discloses a maltotriose-producing amylase derived from a microorganism belonging to the genus Bacillus.
JP 2012-016309 A describes a maltotriose-producing amylase derived from a microorganism belonging to the genus Microbacterium. Furthermore, JP 2012-016309 A describes a maltotriose-producing amylase derived from a microorganism belonging to Streptomyces cinnamonensis. Furthermore, commercially available enzyme preparations include, for example, those under the trade name "AMT1.
2L" (Amano Enzyme Co., Ltd.) and others are on the market.

By enzymatic treatment with maltotriose-forming amylase, the starch contained in sweet potatoes is broken down to produce lower molecular weight sugars. However, maltotriose-forming amylase has a low efficiency in producing glucose, at least, which reduces the sweetness.

The maltotriose-producing amylase may be used alone or in combination of two or more kinds.

The conditions for the enzyme treatment are not particularly limited and may be appropriately selected according to the enzyme used. Typically, the treated raw sweet potato is placed in a suitable container such as a tank together with the enzyme to be used, and heated for 35 to 60 minutes while being stirred by agitation.
The enzyme treatment can be carried out by reacting the mixture at 5°C, more typically at 50 to 60°C, for 15 to 120 minutes. After the enzyme treatment, the mixture may be heated to 70°C or higher, more preferably 90°C or higher, to inactivate the enzyme used. As another example, the enzyme may be added first, and the liquid may be gradually accumulated over 15 to 60 minutes, and juicing may be started when the entire amount has been accumulated. When two or more types of enzymes are used in combination, the treatment with different enzymes may be carried out in stages, or different enzymes may be added together to the processed raw sweet potato product and the enzyme treatment may be carried out.

In the method for obtaining sweet potato juice according to the present invention, in a preferred embodiment, the enzymatic treatment may be carried out using a fiber- or protein-degrading enzyme (hereinafter sometimes simply referred to as a "fiber-degrading enzyme") in addition to the maltotriose-forming amylase.
The fiber of sweet potato is efficiently decomposed, and the amount of juice obtained from the raw material, i.e., the squeezing rate (yield in terms of solid content) is improved, and thus the yield is improved. Examples of the fiber-decomposing enzyme include cellulase, hemicellulase, pectinase, protease, etc. One type of fiber-decomposing enzyme may be used alone, or two or more types may be used in combination.

The conditions for the enzyme treatment when using the above-mentioned fibrous enzyme are not particularly limited, as in the conditions for the enzyme treatment with the above-mentioned maltotriose-forming amylase, and may be appropriately performed under conditions suitable for the enzyme used. Typically, for example, the raw sweet potato processed product is placed in an appropriate container such as a tank together with the enzyme to be used, and while stirring with a stirring means, the reaction can be performed for 15 to 120 minutes at 35 to 65°C, more typically 50 to 60°C, by a heating means. After the enzyme treatment, the enzyme used may be inactivated by, for example, increasing the temperature to 70°C or higher, more preferably 90°C or higher. As another example, the enzyme may be added first, and the liquid may be gradually accumulated over 15 to 60 minutes, and squeezing may be started when the entire amount is accumulated. In addition, when two or more types of enzymes are used in combination, the treatment with different types of enzymes may be performed stepwise, or the enzyme treatment may be performed by adding different types of enzymes together to the raw sweet potato processed product. When the maltotriose-forming amylase and the fibrous enzyme are treated separately, the order of the treatments may be arbitrary, and the treatments with the maltotriose-forming amylase and the fibrous enzyme may be repeated.

It should be noted that the use of enzymes other than the above-mentioned maltotriose-forming amylase or the above-mentioned enzyme treatment with decomposing enzymes for fiber or protein is not excluded, and other enzymes can also be used as desired.

In the method for obtaining sweet potato juice according to the present invention, the processed sweet potato obtained through the processes of blanching, hydration, and crushing is subjected to the enzyme treatment as described above, and then juice is extracted. The juice is obtained by removing juice residue such as pulp by the juice extraction process.

The means for squeezing is not particularly limited, and for example, centrifugal type squeezing machines such as a decanter or a separator, and squeezing type squeezing machines such as a filter press, a belt press or a screw press are known, and an appropriate means may be selected from these depending on the purpose.

After the squeezing process, various processes such as sterilization, concentration, filtration, homogenization, etc. may be carried out to obtain the squeezed juice according to the present invention.

In a preferred embodiment of the method for obtaining sweet potato juice according to the present invention, the juice may be concentrated after squeezing to obtain a juice having a Brix value of 45 to 55, more preferably 47.5 to 52.5, and even more preferably 49 to 51. This is convenient for use in the form of temporarily storing the juice as a concentrated sweet potato juice by freezing or the like and using it at any time to produce sweet potato juice. In this case, the quality of each lot of the juice may be inspected to control the quality of the sweet potato juice to be produced, or in some cases, different lots may be mixed to adjust the quality of the sweet potato juice to be produced.

The concentration means is not particularly limited, and for example, concentrators such as single-effect boilers and multi-effect boilers are known, and an appropriate means may be selected from these depending on the purpose.

The sweet potato juice obtained as described above typically contains carbohydrates in an amount of 70% by mass to 98% by mass, more typically 80% by mass to 97% by mass, and even more typically 90% by mass to 96% by mass, based on the total solid content. Also, the sweet potato juice typically contains maltotriose as a product of the action of maltotriose-producing amylase in an amount of 1% by mass to 20% by mass, more typically 1% by mass to 15% by mass, even more typically 2% by mass to 7.5% by mass, and especially typically 3% by mass to 5% by mass, based on the total solid content. The starch content in the sweet potato juice is preferably 10% by mass or less, and the glucose content is preferably 10% by mass or less, based on the total solid content, and more preferably 7.5% by mass or less, and 7.5% by mass or less, based on the total solid content. The anthocyanin compound is preferably contained in an aglycone equivalent of 0.75% by mass or more, and more preferably 1% by mass or more, based on the total solid content. There is no particular limit to the lower limit of the starch or glucose content, but usually, starch is contained in at least 1% by mass or more, more typically at least 3% by mass or more, based on the total solid content of the sweet potato juice. Alternatively, glucose is contained in at least 0.5% by mass or more, more typically at least 1% by mass or more, based on the total solid content of the sweet potato juice. Furthermore, although there is no particular upper limit to the content of anthocyanin compounds, based on the content naturally contained in sweet potatoes, the upper limit is generally considered to be at most about 5% by mass of anthocyanin compounds, calculated as their aglycones, relative to the total solid content of sweet potato juice, and more typically at most about 3% by mass.

The sweet potato juice obtained as described above has a flavor and nutritional components derived from sweet potatoes, while the starch content is within the above range, so the juice does not have a powdery mouthfeel when prepared. In addition, since the glucose content is within the above range, a sweet potato juice with a moderate sweetness is obtained without being too strong. If the carbohydrate content per solid content of the sweet potato juice is less than the above range, it tends to be difficult to maintain the sweet potato flavor generally exhibited by the sweet potato-derived components.

On the other hand, in the method for producing sweet potato juice according to the present invention, sweet potato juice is produced using the sweet potato juice obtained as described above. The raw materials used in the production of the sweet potato juice are not particularly limited as long as they are raw materials generally used in the production of juice products. Typical examples include water, lemon juice, flavorings, plant-derived extracts, acidulants, thickeners, sweeteners, citrus juices, and the like. Among these, from the viewpoint of compatibility with the flavor of sweet potatoes, it is preferable to use lemon juice, acidulants, and flavorings. From the viewpoint of improving storage stability, it is preferable to adjust the pH to 3.60 to 4.00 by blending a pH adjuster such as an organic acid as necessary. In order to obtain a straight feeling of sweet potato flavor, it is preferable that the sweet potato juice obtained as described above accounts for 30% by mass or more and less than 100% by mass (as Brix value 50) of the total mass of the raw materials for sweet potato juice, more preferably 40% by mass or more and 80% by mass or less, and more preferably 40% by mass or more and 80% by mass or less.
It is even more preferable that the content is from 10% by mass to 70% by mass.

The sweet potato juice obtained as described above is, for example, 65 mL or more and 30 mL or less in a single serving container.
In this case, the anthocyanin compound may be provided in a form of a packaged beverage containing 200 mg or more and 550 mg or less of the anthocyanin compound in terms of its aglycone in one container, and more preferably 230 mg or more and 450 mg or less of the anthocyanin compound in terms of its aglycone in one container.

The contents of various components in this specification can be analyzed, for example, as follows.

Moisture: 105°C constant weight drying method Carbohydrates: The total mass excluding the sum of the quantitative values for moisture, protein (by Kjeldahl method), lipids (by acid hydrolysis method), and ash (by incineration method) was treated as the carbohydrate content.
Starch: Modified Somogyi method Glucose: HPLC method Anthocyanin compounds: Bilberry extract In accordance with the Food Standards and Criteria, the glycosides are desugared by heating under reflux in hydrochloric acid. The amount of anthocyanidins is then calculated from the specific absorbance using the delphinidin amount as the standard.
Maltotriose: HPLC method

The Brix value can also be measured using a commercially available sugar content meter.

The present invention will be described in detail below with reference to examples, but the scope of the present invention is not limited to these examples.

(enzyme)
The contents of the enzyme preparations used in the test are summarized in Table 1.

(Brix value)
The Brix of the sample at 20° C. was measured using a saccharometer (Atago RX-5000α, manufactured by Atago Co., Ltd.).

(Preparation Example 1-1)
A concentrated juice for sweet potato juice (set Brix value: Bx50) was produced using Ayamurasaki, a colored sweet potato, as a raw material. Specifically, the raw sweet potato was washed in a drum-type washing machine, peeled using a steam peeler, and cut into 20 mm thick pieces using a slicer. This was placed in a blanching tank and heated at 93°C for 15 minutes for blanching treatment, and water was added to the same amount as the raw material, and then crushed using a hammer crusher. After crushing, the liquid was sent to a tank and subjected to enzyme treatment. As enzymes, (1) product name "Gluczyme AF6" (manufactured by Amano Enzyme Co., Ltd.), (2) product name "Gluc SBG" (manufactured by Amano Enzyme Co., Ltd.), and (3) product name "Hemicellulase M" (manufactured by HBI Co., Ltd.) were used, which are among the enzyme preparations shown in Table 1.
The enzyme preparation (1) is added in an amount of 0.125 parts by mass per 100 parts by mass of raw sweet potato, the enzyme preparation (2) is added in an amount of 0.125 parts by mass per 100 parts by mass of raw sweet potato, and the enzyme preparation (3)
The mixture was reacted at 50 to 55°C for 15 minutes while being stirred with a stirring device installed in the tank, and then the juice was extracted with a decanter type juice extractor. The obtained primary juice was sterilized with UHT and then sterilized in a triple effect canister until the Brix value reached Bx50.
(The final Brix value was approximately Bx 50.10 to 50.30).

(Preparation Example 1-2)
A concentrated juice for sweet potato juice (set Brix value: Bx50) was produced using Ayamurasaki, a colored sweet potato, as the raw material. Specifically, the raw sweet potato was washed in a drum-type washer, peeled using a steam peeler, and cut into 20 mm thick pieces using a slicer. This was placed in a blanching tank and heated at 93°C for 15 minutes for blanching treatment, and water was added so that the amount was three times the amount of the raw material, and then crushed using a hammer crusher. After crushing, the liquid was sent to a tank and subjected to enzyme treatment. As the enzyme, (4) product name "AMT1" from the enzyme preparations shown in Table 1 was used.
(2) "Cellulase TP-5" (manufactured by Kyowa Kasei Co., Ltd.) and (3) "Cellulase TP-5" (manufactured by Amano Enzyme Co., Ltd.) were used, and 0.125 parts by mass of enzyme preparation (4) was added per 100 parts by mass of raw sweet potato, and 0.125 parts by mass of enzyme preparation (5) was added per 100 parts by mass of raw sweet potato. After reacting at 50 to 55°C for 15 minutes, the juice was squeezed using a decanter type juicer, and the obtained primary juice was UHT sterilized and concentrated in a triple effect canister to a set Brix value of Bx50 (the final Brix value was approximately Bx50.10 to 50.30).

(Preparation Example 1-3)
Concentrated juice for sweet potato juice (set Brix value: Bx50) was produced in the same manner as in Preparation Example 1-2, except that raw materials harvested at different times were used as the Ayamurasaki raw materials (final Brix value was approximately Bx50.10 to 50.30).

(Preparation Example 1-4)
A concentrated juice for sweet potato juice (set Brix value: Bx50) was produced using Ayamurasaki, a colored sweet potato, as the raw material. Specifically, the raw sweet potato was washed in a drum-type washer, peeled using a steam peeler, and cut into 40 mm thick pieces using a slicer. This was placed in a blanching tank and heated at 93°C for 15 minutes for blanching treatment, and water was added so that the amount was six times the amount of the raw material, and then crushed using a hammer crusher. After crushing, the liquid was sent to a tank and subjected to enzyme treatment. As the enzyme, (4) product name "AMT1" from the enzyme preparations shown in Table 1 was used.
(4) was added in an amount of 0.125 parts by mass per 100 parts by mass of raw sweet potatoes, and (5) was added in an amount of 0.03 parts by mass per 100 parts by mass of raw sweet potatoes.
After reacting at 50 to 55°C for 15 minutes, the juice was extracted using a decanter-type juice extractor. The obtained primary juice was sterilized with UHT and then concentrated in a triple-effect concentrate to a set Brix value of Bx 50 (the final Brix value was approximately Bx 50.10 to 50.30).

(Preparation Example 1-5)
Concentrated juice for sweet potato juice (set Brix value: Bx50) was produced in the same manner as in Preparation Example 1-4, except that raw materials harvested at different times were used as the Ayamurasaki raw materials (final Brix value was approximately Bx50.10 to 50.30).

(Preparation Example 1-6)
The same raw materials as in Preparation Example 1-5 were used at the same harvest time, but the peeling treatment was not performed.
In the same manner as in -5, concentrated juice for sweet potato juice (set Brix value: Bx 50) was produced (final Brix value was approximately Bx 50.10 to 50.30).

Table 2 shows the combinations and amounts of enzyme preparations used in the preparation of the concentrated juices obtained in Preparation Examples 1-1 to 1-6.

<Test Example 1>
The concentrated juices obtained in Preparation Examples 1-1 to 1-6 were analyzed for sugar composition and anthocyanin content. The analysis methods used were the modified Somogyi method for starch content, and the saccharide contents of glucose, fructose, galactose, sucrose, lactose, and maltose were determined by HPLC.
The quantitative values were obtained by the C method. The total solid content was calculated by calculating the moisture content by the 105°C constant weight drying method and calculating the difference from the total amount. Furthermore, for carbohydrates, the total mass was treated as the carbohydrate content except for the total amount of the quantitative values for moisture (by the 105°C constant weight drying method), protein (by the Kjeldahl method), lipids (by the acid decomposition method), and ash (by the incineration method). On the other hand, for the anthocyanin content, the amount of anthocyanidin after desugaring by heating under hydrochloric acid acidity was calculated from the specific absorbance by the absorbance method based on the amount of delphinidin, in accordance with the bilberry extract food standard. The results are shown in Table 3.

As a result, in Preparation Example 1-1, in which glucoamylase and α-amylase were used in the enzyme treatment, the glucose content was 29.0 g/100 g (60.3% by mass relative to the total solid content), whereas in Preparation Examples 1-2 to 1-6, in which maltotriose-producing amylase and cellulase were used in the enzyme treatment, the glucose content was 1.0 g/100 g to 2.9 g/100 g.
The concentrated juice obtained was diluted with water to the same concentration as sweet potato juice, and the taste was evaluated separately.
The sweetness of Preparation Example 1-1 was strong, whereas the sweetness of Preparation Example 1-2 to Preparation Example 1-6 was moderate. On the other hand, the anthocyanidin content was 345 mg in Preparation Example 1-1.
/100g (0.7% by mass relative to the total solid content), whereas in Preparation Examples 1-2 to 1-6 it was 505 mg/100g to 669 mg/100g (1.0% by mass to 1.4% by mass relative to the total solid content).

<Test Example 2>
From the results of Test Example 1, it was considered that the type of enzyme used in producing sweet potato juice may affect the taste and anthocyanin content of the sweet potato juice. Therefore, various conditions such as the amount of water added to the raw material during enzyme treatment and the amount of enzyme preparation added were set, and the influence of the type of enzyme was investigated. Therefore, in this test example, the sugar composition and anthocyanin content were investigated when the type of enzyme was changed for sweet potato juice prepared on a laboratory scale, not using equipment for producing concentrated sweet potato juice.

Specifically, 1 to 2 kg of raw material (unpeeled) Ayamurasaki is washed by hand and cut into pieces about 4 times with a knife.
The meat was sliced into about 10 mm thick pieces, immersed in boiling water and heated at 98°C for 15 minutes for blanching, and then water was added to the meat so that the amount was six times the amount of the raw material. The meat was then crushed in a biaxial crusher and then in a mixer. After crushing, the meat was transferred to a container and treated with enzymes in the combinations and amounts shown in Table 4.

As the enzymes, (2) trade name "Gluc SBG" (manufactured by Amano Enzyme Inc.), (4) trade name "AMT1.2L" (manufactured by Amano Enzyme Inc.), and (5) trade name "Cellulase TP-5" (manufactured by Kyowa Kasei Co., Ltd.) were used among the enzyme preparations shown in Table 1, in the combinations and amounts added shown in Table 4. After reaction at 55°C for 1 hour while stirring with a tabletop stirrer, the mixture was centrifuged (3,000 rpm, 10 minutes) to recover the supernatant, which was passed through a 60-mesh sieve to obtain a crude filtrate, which was then heated to 95°C to inactivate the enzymes, and sweet potato juice was obtained.

The obtained juice was evaluated for each property such as Brix value (Bx sugar content), pH, and juice extraction rate (according to the following formula (1)).
The degree of color change was evaluated using a titrant for the iodine-starch reaction, and the taste was evaluated for off-flavors and sweetness.

(Juice extraction rate)
Juice yield (%) = (mass of juice obtained / total mass after adding water to raw material) x 1
00 ... (1)

(Starch Decomposition)
The color change due to the addition of a titrant for the iodine-starch reaction (a 95% aqueous ethanol solution containing 10 w/v % iodine) was observed.

○ No change △ Some change × Change

(taste)
○ Good △ Slightly poor × Poor

The results are shown in Table 5.

As a result, no difference was observed in the properties of the sweet potato juice obtained between Preparation Example 2-1, in which maltotriose-producing amylase, cellulase, esterase, and tannase were used in combination as the enzymes used for the enzymatic treatment, and Preparation Example 2-2, in which only maltotriose-producing amylase was used, and both starch hydrolysis and taste were good.

On the other hand, in Preparation Example 2-3, in which only cellulase, esterase, and tannase were used in combination as enzyme treatment, and no maltotriose-producing amylase was used, the starch was poorly decomposed and the viscosity was considered to be too high for use in juice. In addition, the taste was slightly strange compared to Preparation Examples 2-1 and 2-2.

On the other hand, in Preparation Example 2-4, in which glucoamylase and α-amylase were used as the enzymes for the enzymatic treatment, the obtained sweet potato juice was very sweet and was considered to be too sweet for use as juice (the proportion of glucose in the solids was 16.2% by mass).

The sugar composition and anthocyanidin content of the juice of Preparation Example 2-1 and the juice of Preparation Example 2-4 were examined in the same manner as in Test Example 1. In addition, the Brix value of the prepared juice was multiplied by a factor to give Bx50 to calculate the Bx50 content. The results are shown in Table 6.

As a result, in Preparation Example 2-1, in which maltotriose-producing amylase was used as the enzyme for the enzymatic treatment, the anthocyanidin content was about 1.6 times higher when converted to Bx50 than in Preparation Example 2-4, in which glucoamylase was used, even though the contents in the prepared juice were about the same. This is because the Brix value was higher due to the enzyme, and the Bx
This was thought to be because the concentration was lower when converted to 50.

<Test Example 3>
Sweet potato juice was prepared on a laboratory scale in the same manner as in Test Example 2, except that the enzymes were used in the combinations and amounts added shown in Table 7.

The obtained juice was evaluated for each property such as Brix value (Bx sugar content), pH, and juice extraction rate (according to the above formula (1)). The results are shown in Table 8.

As a result, in Preparation Example 3-1, in which maltotriose-producing amylase and cellulase were used in combination as the enzymes used for enzymatic treatment, no significant differences were observed in the Brix value or pH properties of the resulting sweet potato juice compared to Preparation Example 3-2, in which only maltotriose-producing amylase was used. However, the juice extraction rate in Preparation Example 3-1 was 97.5%, which was significantly higher than the 89.9% juice extraction rate in Preparation Example 3-2.

From the above, it became clear that by increasing the amount of cellulase added, the juice extraction rate can be improved, and ultimately the yield can be improved.

Claims (5)

A sweet potato juice obtained from sweet potatoes, containing carbohydrates at 70% by mass or more and 98% by mass or less based on the total solid content, characterized in that the starch content is 10% by mass or less based on the total solid content, the glucose content is 10% by mass or less based on the total solid content, the maltotriose content is 1% by mass or more and 20% by mass or less based on the total solid content, and the anthocyanin compound is 0.75% by mass or more based on the total solid content in terms of its aglycone. The sweet potato juice according to claim 1, having a Brix value of 45 or more and 55 or less. The sweet potato juice according to claim 1 or 2, wherein the maltotriose is produced by a maltotriose -producing amylase. A method for producing sweet potato juice, comprising a step of mixing the sweet potato juice according to any one of claims 1 to 3 with other raw materials. The method for producing sweet potato juice according to claim 4, wherein the other ingredients are one or more selected from the group consisting of water, lemon juice, acidulants, and flavorings.