Calcium-containing rare sugar syrup, and production method of the same by microwave heating

Abstract

To provide a method for producing calcium-containing rare sugar syrup in the presence of commonly found shells or eggshells by using reducing sugar as a raw material and by microwave heating treatment.SOLUTION: In the presence of shells or eggshells, reducing sugar is heated by microwave under pressure to efficiently isomerize into rare sugar, and thus various kinds of calcium-containing rare sugar syrup can be produced.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a method for producing calcium-containing rare sugar syrup by using reducing monosaccharides, disaccharides or oligosaccharides as raw materials and subjecting them to microwave heating in the presence of commonly occurring shells or eggshells. [Background technology]

[0002] Rare sugars are sugars that exist only in small amounts in nature. They are sweet, low in calories, and known to have various beneficial physiological functions, such as suppressing body fat accumulation and blood sugar level elevation, as well as antioxidant effects (Non-Patent Documents 1 and 2), and are therefore attracting attention as functional food ingredients.

[0003] Several methods for producing rare sugars have been investigated, and reported methods include biotechnological techniques using microorganisms and enzymes, isomerization methods using alkali, isomerization methods using subcritical aqueous alcohol, and isomerization methods using subcritical buffer solutions. Specifically, known biotechnological techniques include a method in which microorganisms of the genus Rhizopus are cultured in the presence of D-psicose and D-tagatose is recovered from the culture medium (Patent Document 1), and a method in which 3-ketodisaccharides are produced using an oxidation reaction in which an oxidase derived from a microorganism of the genus Agrobacterium acts on a disaccharide as a raw material (Patent Document 2).

[0004] Known isomerization methods using alkaline treatment include isomerization of reducing sugars under alkaline conditions using sodium hydroxide or calcium hydroxide (Non-Patent Documents 3 and 4) or germanium compounds (Patent Document 3). A derivative of alkaline treatment has also been reported, in which rare sugars are produced by isomerizing reducing sugars through treatment with subcritical aqueous alcohol or a subcritical buffer solution (Patent Documents 4 and 5). Specifically, the common monosaccharide galactose can be isomerized into the rare monosaccharides tagatose and talose by treating aqueous alcohol in subcritical aqueous alcohol heated above its boiling point under pressure, or in a subcritical buffer solution.

[0005] However, the various biotechnological techniques described above require sophisticated process control for culturing and preparing microorganisms or enzymes. Furthermore, while the isomerization method using alkaline treatment is easy to control, it produces many by-products and requires the effort of treating alkaline waste liquid. The method using subcritical aqueous alcohol treatment is simple and does not require waste liquid treatment, but it requires the use of flammable hazardous materials. Furthermore, the method using a subcritical buffer solution can be easily carried out, but does not achieve a high yield due to the generation of acidic substances as a side reaction. Furthermore, dedicated equipment is required for subcritical water treatment. Thus, there is a lack of knowledge about whether rare sugars can be produced efficiently, which is an obstacle to industrial production. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Patent 3840538 [Patent Document 2] Patent 5356704 [Patent Document 3] JP 7-196678 [Patent Document 4] Patent Publication No. 2016-20310 [Patent Document 5] Patent Publication No. 2021-66710 [Non-patent literature]

[0007] [Non-Patent Document 1] J. Agric. Food Chem.,56,4789-4796(2008). [Non-patent document 2] J. Funct. Food.,2,152-159(2014). [Non-patent document 3] Applied Glycoscience, 6, 37-42(2016). [Non-patent document 4] Journal of the Agricultural Chemical Society of Japan, 40,35-40(1966). Summary of the Invention [Problem to be solved by the invention]

[0008] An object of the present invention is to provide a method for simply and efficiently producing calcium-containing rare sugar syrup by microwave heating treatment. [Means for solving the problem]

[0009] The present inventors have conducted studies to solve the above-mentioned problems and have found that commonly occurring sugars can be isomerized into rare sugars simply and efficiently by immediately neutralizing acidic substances produced as by-products during microwave heating of sugars with shells or eggshells. Furthermore, they have also found that calcium in shells or eggshells is solubilized by neutralization. Based on these findings and further studies, the present invention has been completed as a method for producing calcium-containing rare sugar syrup. [Effects of the Invention]

[0010] According to the present invention, calcium-containing rare sugar syrup can be produced using inexpensive and commonly available reducing sugars and seashells or eggshells under easy process control, at low cost, in a short time, and with low environmental impact. DETAILED DESCRIPTION OF THE INVENTION

[0011] The method for producing calcium-containing rare sugar syrup of the present invention is characterized by comprising a step of isomerizing commonly occurring reducing sugars by simple microwave heating in the presence of shells or eggshells. The method for producing calcium-containing rare sugar syrup of the present invention is described in detail below.

[0012] The production method of the present invention can use a commonly occurring reducing sugar (monosaccharide, disaccharide, oligosaccharide, or polysaccharide) as a raw material. In the present invention, the commonly occurring sugar may be purified or unpurified, or may be contained in other substances, contain other substances, or be present in foods.

[0013] To produce calcium-containing rare sugar syrup using the production method of the present invention, a reducing sugar solution is subjected to microwave heating in the presence of shells or eggshells. Specifically, a suspension containing water, reducing sugar, and shells is prepared, and the suspension is heated using a microwave heating device.

[0014] The microwave heating device used in the production method of the present invention is not particularly limited as long as it can heat water. The device may be a batch type or a continuous type in which the treatment liquid flows continuously, and a known microwave heating device for organic synthesis or, more simply, a microwave oven or the like can be used.

[0015] In the production method of the present invention, the concentration of reducing sugars subjected to microwave heating is not particularly limited, but may be, for example, 0.1 to 30 wt%. From the viewpoint of more efficient isomerization of common sugars into rare sugars, the common sugar concentration is preferably 20 wt%. In addition, the pH of the raw material suspension should be 6 or higher, preferably 7 or higher.

[0016] In the manufacturing method of the present invention, the shells or eggshells may be unbaked, but baked shells can also be used. The water used in the microwave heating treatment may contain an organic solvent such as alcohol or a buffer solution, but preferably has a pH of 6 or higher. The type of shell or eggshell is not particularly limited, but examples include readily available shells of clams, cockles, scallops, or turban shells, as well as chicken eggshells and quail eggshells. These shells may be used alone or in combination of two or more. The shells may be in either crushed or powder form.

[0017] The microwave heating time in the production method of the present invention is appropriately set depending on the type and concentration of the reducing sugar, the properties of the shell or eggshell, the temperature, and the pressure, but is usually preferably about 1 minute.

[0018] The microwave output in the production method of the present invention may be appropriately set depending on the concentration of reducing sugar, processing time, etc. For example, the microwave output may be 700 W or 200 W, but it may be changed during processing.

[0019] After microwave heating, the solution is cooled and then recovered. The solution contains calcium ions and rare sugars derived from the shells or eggshells, and may be used as a calcium-containing rare sugar syrup as is, for example, as a sweetener, functional food material, or pharmaceutical raw material. However, if necessary, the solution may be subjected to concentration, drying, purification, or the like to be used as a higher-purity calcium-containing rare sugar syrup. [Example]

[0020] The present invention will be described in detail below with reference to examples, but the present invention is not limited to these examples.

[0021] [Example 1 and Comparative Example 1] In Example 1, galactose (0.2 mol / L) and 0.5 g of shell powder were mixed with deionized water (5 mL) to prepare a raw material suspension. In Comparative Example 1, a 0.2 mol / L aqueous galactose solution was prepared using deionized water and used as the raw material solution. The raw material suspension or raw material solution was placed in a pressure-resistant container and subjected to microwave heating treatment at a constant output of 700 W for 1 minute using a microwave irradiation device. After heating, the reaction mixture was filtered through a membrane filter (pore size 0.2 μm). The component concentrations in the filtrate were measured by high-performance liquid chromatography, and the yield of each rare sugar was calculated. In Example 1, the yields of tagatose, talose, and sorbose were 17%, 1.5%, and 1.5%, respectively. On the other hand, in Comparative Example 1, in which shells were not present, the yield of tagatose was 0.5%, and talose and sorbose were not detected. From these results, it was found that microwave heating of reducing sugar (galactose) in the presence of shells reduced the residual rate of galactose and produced rare sugars (tagatose, talose, and sorbose). Thus, it was revealed that shells produce tagatose, talose, and sorbose from galactose. Furthermore, the calcium ion concentration in the resulting treatment solution was 200 ppm. On the other hand, in Comparative Example 1, the calcium ion concentration was below the detection limit. Thus, it was revealed that the addition of shells significantly increased the calcium ion concentration.

[0022] Example 2 A 0.2 mol / L maltose solution (50 mL) and 0.5 g of shell powder were placed in a pressure vessel and microwaved at a constant output of 700 W for 105 seconds using a microwave irradiation device. After heating, the reaction mixture was filtered. The maltulose concentration in the filtrate was measured, and the yield was calculated to be 31%.

[0023] Example 3 A 0.2 mol / L lactose solution (50 mL) and 0.5 g of shell powder were placed in a pressure vessel and microwaved at a constant output of 700 W for 105 seconds. After heating, the reaction mixture was filtered. The lactulose concentration in the filtrate was measured, and the yield was calculated to be 25%.

[0024] Example 4 A 0.2 mol / L ribose solution (50 mL) and 0.5 g of shell powder were placed in a pressure vessel and microwaved at a constant output of 700 W for 105 seconds. After heating, the reaction mixture was filtered. The ribulose concentration in the filtrate was measured, and the yield was calculated to be 10%.

[0025] Example 5 A 0.2 mol / L maltose solution (50 mL) and 0.5 g of shell powder were placed in a pressure vessel and microwaved at a constant output of 200 W for 450 seconds using a microwave irradiation device. After heating, the reaction mixture was filtered. The maltulose concentration in the filtrate was measured, and the calculated yield was approximately 29%, with the yield of the by-product glucose being approximately 3.5%.

[0026] Example 6 A 5% aqueous galactose solution (40 mL) and 4.0 g of eggshell powder were placed in a pressure vessel and microwaved at a constant output of 200 W for 270 seconds. After heating, the reaction mixture was filtered. The concentrations of tagatose, talose, and sorbose in the filtrate were measured, and the yields were calculated to be approximately 17%, 1.7%, and 1.2%, respectively.

[0027] As shown in Examples 2 to 5, it was revealed that rare sugars can also be produced from disaccharides and pentoses by similar microwave heating treatment. Furthermore, as shown in each example, it was revealed that aldoses or ketoses, which are epimers at the 2- or 3-position of the sugar molecule, are produced by microwave heating sugars in the presence of shells or eggshells.

Claims

1. A calcium-containing rare sugar syrup obtained by isomerizing reducing monosaccharides, disaccharides, or oligosaccharides by microwave heating in the presence of shells or eggshells.

2. A method for producing the calcium-containing rare sugar syrup according to claim 1 by microwave heating.