Processing method of glutinous yam flour

Abstract

The invention provides a processing method of glutinous Chinese yam powder, and relates to the technical field of Chinese yam processing. The preparation process of the glutinous Chinese yam powder mainly comprises the following steps: slicing glutinous Chinese yams, soaking with acetic acid, carrying out boosting low-temperature half-cooking treatment on the Chinese yam slices, carrying out stepped freezing treatment, carrying out vacuum combined inert gas drying treatment, crushing and the like. The waxy yam flour overcomes the defects in the prior art, effectively reduces the loss of the content of nutritional ingredients in the yam flour, further reduces the content of quickly digestible starch in the waxy yam flour, and improves the eating health of the waxy yam starch; the storage stability of the final glutinous yam flour is comprehensively improved through multi-step operation, moisture absorption and caking are prevented, and the comprehensive quality of the glutinous yam flour is improved.

Description

Technical Field

[0001] The invention relates to the technical field of yam processing, and in particular to a method for processing glutinous yam powder. Background Art

[0002] Chinese yam is a common plant that is both a medicine and food. Its tubers are rich in nutrients such as starch and protein, as well as active ingredients such as polysaccharides, polyphenols, saponins and allantoin. It has the effects of nourishing health, strengthening the spleen and stomach, and improving physical fitness. Modern pharmacological studies have shown that it has the effects of regulating immunity, improving the gastrointestinal barrier, and regulating sugar and lipid metabolism. However, fresh Chinese yam is highly seasonal, has a high moisture content, is easy to rot, and is not resistant to storage, which seriously affects the medicinal and edible value of Chinese yam and the benefits of the Chinese yam planting industry.

[0003] Yam powder has a low water content, is easy to store and transport, and can be added to other foods as a raw material. Therefore, processing fresh yam into yam powder can not only effectively solve the problem of yam's poor storage resistance, but also increase the product variety of yam, providing new ideas for the development of the yam market.

[0004] The existing yam powder making process mainly includes hot air drying, spray drying, freeze drying and other methods, but hot air drying can easily cause problems such as hardening, browning and loss of nutrients on the yam surface; spray drying is due to the high starch content of yam, especially glutinous yam, the starch content of which is significantly higher than that of ordinary yam, and the viscosity will be higher when the whole is ground and pulped, and it is very easy to cause nozzle clogging during spray drying, which seriously affects production efficiency and may also cause equipment damage, and the overall processing continuity is poor. Although freeze drying can guarantee the quality of yam powder to a certain extent, for glutinous yam, the starch content of yam after powdering is relatively high, and the starch in yam powder is mainly divided into fast-digestible starch, slowly-digestible starch and resistant starch, among which fast-digestible starch has a higher blood sugar-raising effect and poor overall healthiness. Direct freeze-drying and grinding will cause the relative content of fast-digestible starch in yam powder to be higher than that of yam powder prepared by other methods. In addition, directly freeze-dried yam powder is also easy to absorb moisture and agglomerate during storage, which is not conducive to long-term storage. Summary of the invention

[0005] In view of the shortcomings of the prior art, the present invention provides a processing method for glutinous yam powder, which can reduce the content of fast-digestible starch in starch while effectively retaining the beneficial ingredients of glutinous yam, and further improve the storage resistance.

[0006] To achieve the above objectives, the technical solution of the present invention is implemented through the following technical solutions: A method for processing glutinous yam powder, the processing method comprising the following steps: S1. Yam pretreatment: Select fresh glutinous yam, wash it, peel it and slice it, then soak it in an acetic acid solution ice water bath for 4-10 minutes, then take it out and rinse it with clean water for 2-3 times to obtain pretreated yam slices; S2, half-cooked treatment: spread the above-pretreated yam slices flat, add water, then increase the pressure to 1.2-1.6Mpa, seal and stand for 20-30min in a water bath at 40-50°C, and then cool naturally to obtain half-cooked yam slices for use; S3, staged freezing: pre-cooling the semi-cooked yam slices at 2-4°C, freezing them at -20°C--30°C for 2-4h, then cooling them to -40°C--60°C, and continuing freezing for 2-4h to obtain frozen yam slices for later use; S4, drying: placing the frozen yam slices in a sealed oven, evacuating the air, heating to 30-40°C and letting it stand, then returning to normal pressure, heating to 45-50°C and blowing with inert gas to constant weight, and obtaining dried yam slices for use; S5, crushing: grinding and crushing the dried yam slices to obtain glutinous yam powder.

[0007] Preferably, the thickness of the slices in step S1 is 0.5-1.0 cm.

[0008] Preferably, the acetic acid mass concentration of the acetic acid solution in step S1 is 4%-6%.

[0009] Preferably, in step S2, water is added after the pretreated yam slices are laid flat, by adding water until the liquid surface is flush with the upper end of the pretreated yam slices.

[0010] Preferably, the pressure increase in step S2 is performed under a nitrogen atmosphere.

[0011] Preferably, the precooling time in step S3 is 1-2 hours.

[0012] Preferably, the standing time in step S4 is until the frozen yam slices lose more than 10% of their weight.

[0013] Preferably, the inert gas in step S4 is nitrogen.

[0014] Preferably, the glutinous yam powder is sieved through an 80-mesh sieve.

[0015] The present invention provides a method for processing glutinous yam powder, which has the following advantages compared with the prior art: The invention peels and slices the glutinous yam in the early stage, then soaks it in acetic acid, then increases the pressure and temperature to process it half-cooked, and then freezes it in stages and then dries it, so as to effectively reduce the loss of nutrient content of the finally prepared glutinous yam powder, further reduce the content of fast-digestible starch in the glutinous yam powder, and improve the healthiness of eating the glutinous yam starch; and through the multi-step operation, comprehensively improves the storage stability of the final glutinous yam powder, prevents moisture absorption and agglomeration, and improves the comprehensive quality of the glutinous yam powder. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 This is a schematic diagram of frozen yam slices obtained in the process of preparing glutinous yam powder using Example 1 of the present invention; Figure 2 This is a schematic diagram of the dried yam slices obtained in the process of preparing glutinous yam powder using Example 1 of the present invention; Figure 3 This is a schematic diagram of frozen yam slices obtained in the process of preparing glutinous yam powder using Comparative Example 1 of the present invention; Figure 4 This is a schematic diagram of the dried yam slices obtained in the process of preparing glutinous yam powder using Comparative Example 1 of the present invention; Figure 5 This is a schematic diagram of the dried yam slices obtained in the process of preparing glutinous yam powder using Comparative Example 2 of the present invention; Figure 6 This is a schematic diagram of freeze-dried yam slices obtained in the process of preparing glutinous yam powder using Comparative Example 3 of the present invention; Figure 7 This is a schematic diagram of freeze-dried yam slices obtained in the process of preparing glutinous yam powder using Comparative Example 4 of the present invention; Figure 8 This is a schematic diagram of the appearance of glutinous yam flour prepared by the methods of Example 1 and Comparative Examples 1-4 of the present invention after being placed open indoors for 7 days. DETAILED DESCRIPTION

[0017] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention is clearly and completely described below in combination with the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0018] Example 1

[0019] Processing method of glutinous yam powder: (1) Select fresh glutinous yam, wash it, peel it and slice it (0.5-1 cm), then soak it in an ice water bath with a concentration of 5% acetic acid solution for 6 minutes, then take it out and rinse it with clean water for 3 times to obtain pretreated yam slices; (2) Spread the above-mentioned pretreated yam slices flat and add water until the liquid surface is flush with the upper end of the pretreated yam slices, increase the pressure to 1.4 MPa in a nitrogen atmosphere, seal and place in a water bath at 45°C for 25 minutes, and then cool naturally to obtain half-cooked yam slices for use; (3) pre-cooling the semi-cooked yam slices at 4°C for 1.5 hours, freezing them at -25°C for 3 hours, then cooling them to -50°C and continuing to freeze them for 3 hours to obtain frozen yam slices for later use; (4) Place the frozen yam slices in a sealed furnace, evacuate the air, raise the temperature to 35±5°C, and let it stand until the frozen yam slices lose more than 10% of their weight, then return to normal pressure, raise the temperature to 45°C, and purge with nitrogen until constant weight is reached, to obtain dried yam slices for later use; (5) Grind the dried yam slices and pass them through an 80-mesh sieve to obtain glutinous yam powder.

[0020] Comparative Example 1

[0021] Processing method of glutinous yam powder: (1) Select fresh glutinous yam, wash it, peel it and slice it (0.5-1 cm), then soak it in an ice water bath with a concentration of 5% acetic acid solution for 6 minutes, then take it out and rinse it with clean water for 3 times to obtain pretreated yam slices; (2) Soak the pre-treated yam slices in 80°C hot water for 5 minutes, and then take out the half-cooked yam slices for later use; (3) pre-cooling the semi-cooked yam slices at 4°C for 1.5 hours, freezing them at -25°C for 3 hours, then cooling them to -50°C and continuing to freeze them for 3 hours to obtain frozen yam slices for later use; (4) Place the frozen yam slices in a sealed furnace, evacuate the air, raise the temperature to 35±5°C, and let it stand until the frozen yam slices lose more than 10% of their weight, then return to normal pressure, raise the temperature to 45°C, and purge with nitrogen until constant weight is reached, to obtain dried yam slices for later use; (5) Grind the dried yam slices and pass them through an 80-mesh sieve to obtain glutinous yam powder.

[0022] Comparative Example 2

[0023] Processing method of glutinous yam powder: (1) Select fresh glutinous yam, wash it, peel it and slice it (0.5-1 cm), then soak it in an ice water bath with a concentration of 5% acetic acid solution for 6 minutes, then take it out and rinse it with clean water for 3 times to obtain pretreated yam slices; (2) Spread the above-mentioned pretreated yam slices flat and add water until the liquid surface is flush with the upper end of the pretreated yam slices, increase the pressure to 1.4 MPa in a nitrogen atmosphere, seal and place in a water bath at 45°C for 25 minutes, and then cool naturally to obtain half-cooked yam slices for use; (3) pre-cooling the semi-cooked yam slices at 4°C for 1.5 hours, freezing them at -25°C for 3 hours, then cooling them to -50°C and continuing to freeze them for 3 hours to obtain frozen yam slices for later use; (4) Dry the frozen yam slices with hot air at 45°C until constant weight is obtained, and the dried yam slices are set aside; (5) Grind the dried yam slices and pass them through an 80-mesh sieve to obtain glutinous yam powder.

[0024] Comparative Example 3

[0025] Processing method of glutinous yam powder: (1) Select fresh glutinous yam, wash it, peel it and slice it (0.5-1 cm), then soak it in an ice water bath with a concentration of 5% acetic acid solution for 6 minutes, then take it out and rinse it with clean water for 3 times to obtain pretreated yam slices; (2) Spread the above-mentioned pretreated yam slices flat and add water until the liquid surface is flush with the upper end of the pretreated yam slices, increase the pressure to 1.4 MPa in a nitrogen atmosphere, seal and place in a water bath at 45°C for 25 minutes, and then cool naturally to obtain half-cooked yam slices for use; (3) freeze-drying the semi-cooked yam slices at -45°C to obtain freeze-dried yam slices; (5) Grind the freeze-dried yam slices and pass them through an 80-mesh sieve to obtain glutinous yam powder.

[0026] Comparative Example 4

[0027] Processing method of glutinous yam powder: (1) Select fresh glutinous yam, wash it, peel it and slice it (0.5-1 cm), then soak it in an ice water bath with a concentration of 5% acetic acid solution for 6 minutes, then take it out and rinse it with clean water for 3 times to obtain pretreated yam slices; (2) Soak the pre-treated yam slices in 80°C hot water for 5 minutes, and then take out the half-cooked yam slices for later use; (3) freeze-drying the semi-cooked yam slices at -45°C to obtain freeze-dried yam slices; (5) Grind the freeze-dried yam slices and pass them through an 80-mesh sieve to obtain glutinous yam powder.

[0028] Detection

[0029] The same batch of Weixi glutinous yam was selected as the experimental material, and the glutinous yam powder was prepared by the preparation methods of the above embodiment 1 and comparative examples 1-4 respectively; 1. Observe the morphology of the yam slices during the preparation process of Example 1 and Comparative Examples 1-4. Figure 1-7 ; in Figure 1 for Figure 3 They are respectively the frozen yam slices of Example 1 and Comparative Example 1, and the appearance difference between the two is not significant; Figure 2 , Figure 4 , Figure 5 Schematic diagrams of dried yam slices of Example 1, Comparative Example 1 and Comparative Example 2, respectively, wherein Figure 2 The particles are obvious, and the overall color is uniform and basically flat, indicating that the heat is basically uniform during drying; Figure 4 The particles are not obvious, the overall color is uniform, and it is basically flat, which means that the heat is basically uniform during drying, but the previous treatment used 80℃ hot blanching, which caused the surface to be uneven. Figure 2 Make a difference; Figure 5 The grains are obvious, and the grooves between the grains are deep in the middle and shallow around them, and there is a certain degree of curling, which means that the heat is not uniform during drying; Figure 6 and Figure 7 The freeze-dried yam slices of Comparative Example 3 and Comparative Example 4 are respectively Figure 6 The freeze-dried yam slices in Comparative Example 3 have a certain granular feel on the surface, while Figure 7 The surface of the freeze-dried yam slices in Comparative Example 4 is smoother.

[0030] 2. The nutritional composition of the glutinous yam powder obtained in each group was tested (the contents of starch, polysaccharides and allantoin in the glutinous yam powder in each group were tested). The specific results are shown in Table 1 below: Table 1

[0031] As can be seen from the above table, the contents of starch, polysaccharide and allantoin in Example 1 and Comparative Example 3 are the highest, and the starch content in each group of yam powder exceeds 75%, accounting for the majority of the yam powder; 3. Verify the digestibility of starch in each group of yam powder and detect the digestibility of starch in each group, that is, the content of fast digestible starch (RDS), slowly digestible starch (SDS), and resistant starch (RS) in each group of starch. The specific operation is as follows: Weigh 0.3 g of yam powder from each group, add 10 mL of 0.2 mol / L acetic acid buffer with a pH of 5.2, boil for 10 min to completely gelatinize, add 10 mL of mixed enzyme solution (the concentrations of porcine pancreatic α-amylase and saccharifying enzyme are 290 U / mL and 15 U / mL, respectively), and shake in a water bath at 37°C. After reacting for 0, 20, and 120 min, take 1 mL of enzymatic solution, add a small amount of deionized water to dilute, immediately boil in water to inactivate the enzyme for 5 min, then centrifuge at 6 000 r / min for 10 min, and take the supernatant to make up the volume. Determination of the content of RDS, SDS and RS:

[0032] Among them G 20is the amount of reducing sugar in the solution after 20 min of reaction (mg), FG is the amount of reducing sugar before the reaction (mg), G 120 is the amount of reducing sugar in the solution after 120 min of reaction (mg), and TS is the total amount of starch in the sample (mg).

[0033] The specific results are shown in Table 2 below: Table 2

[0034] It can be seen from the above table that the content of RDS in Example 1 is the lowest, that is, the yam powder prepared in Example 1 is the most edible and healthy.

[0035] 4. Detect the chromaticity of the yam powder prepared in each group, that is, use UltraScanVIS colorimeter to measure the color of the yam powder to obtain L* value, a* value and b* value, where L* value represents black and white brightness, the larger the value, the whiter and brighter; a* value represents green and red, the larger the value, the redder the sample; b* value represents blue and yellow, the larger the value, the yellower the sample. The specific results are shown in Table 3 below: Table 3

[0036] It can be seen from the above table that the yam powder prepared in Example 1 and Comparative Example 3 has the best color.

[0037] 5. Test the storage stability of each group of yam powder at room temperature. Place each group of yam powder open in the room (room temperature is 10-20℃, air humidity is 40%-60%). After 7 days, observe whether the surface of each group of yam powder is clumping. The specific results are as follows: Figure 8 As shown, there is basically no agglomeration on the surfaces of Example 1, Comparative Example 1 and Comparative Example 2, while obvious agglomeration occurs on the surfaces of Comparative Example 3 and Comparative Example 4.

[0038] From the above tests, it can be seen that the glutinous yam powder prepared in Example 1 has the best quality.

[0039] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that the technical solutions described in the aforementioned embodiments may still be modified, or some of the technical features may be replaced by equivalents. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for processing glutinous yam powder, characterized in that: The processing method comprises the following steps: S1. Yam pretreatment: Select fresh glutinous yam, wash it, peel it and slice it, then soak it in an acetic acid solution ice water bath for 4-10 minutes, then take it out and rinse it with clean water for 2-3 times to obtain pretreated yam slices; S2, half-cooked treatment: spread the above-pretreated yam slices flat, add water, then increase the pressure to 1.2-1.6Mpa, seal and stand for 20-30min in a water bath at 40-50°C, and then cool naturally to obtain half-cooked yam slices for use; S3, staged freezing: pre-cooling the semi-cooked yam slices at 2-4°C, freezing them at -20°C--30°C for 2-4h, then cooling them to -40°C--60°C, and continuing freezing for 2-4h to obtain frozen yam slices for later use; S4, drying: placing the frozen yam slices in a sealed oven, evacuating the air, heating to 30-40°C and letting it stand, then returning to normal pressure, heating to 45-50°C and blowing with inert gas to constant weight, and obtaining dried yam slices for use; S5, crushing: grinding and crushing the dried yam slices to obtain glutinous yam powder.

2. The processing method according to claim 1, characterized in that: The thickness of the slices in step S1 is 0.5-1.0 cm.

3. The processing method according to claim 1, characterized in that: The acetic acid mass concentration of the acetic acid solution in step S1 is 4%-6%.

4. The processing method according to claim 1, characterized in that: In the step S2, water is added after the pre-treated yam slices are laid flat, and water is added until the liquid surface is flush with the upper end of the pre-treated yam slices.

5. The processing method according to claim 1, characterized in that: The pressure increase in step S2 is performed under a nitrogen atmosphere.

6. The processing method according to claim 1, characterized in that: The precooling time in step S3 is 1-2 hours.

7. The processing method according to claim 1, characterized in that: The standing time in step S4 is until the frozen yam slices lose more than 10% of their weight.

8. The processing method according to claim 1, characterized in that: The inert gas in step S4 is nitrogen.

9. The processing method according to claim 1, characterized in that: The glutinous yam powder is passed through an 80-mesh sieve.

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