Compound low-GI Chinese yam powder with high-activity component retention and targeted probiotic effects and preparation method of compound low-GI Chinese yam powder

Abstract

The invention relates to the technical field of food, in particular to compound low-GI Chinese yam powder with high-activity component retention and targeted prebiotics and a preparation method thereof. The preparation method comprises the following steps: mixing Chinese yam with a composite color-protecting solution, performing low-temperature ultrasonic treatment, then performing wall breaking in a low-temperature pulsed electric field, and finally performing vacuum microwave drying and crushing to obtain raw Chinese yam powder; mixing the raw Chinese yam powder with the prebiotic component, the natural sweet taste and flavor component and the microencapsulated trace element component, and embedding to prepare the compound low-GI Chinese yam powder. The problems of nutrition loss and browning of traditional drying are solved through a synergistic processing technology, intestinal tract prebiotics and low-GI function targeting are achieved through a compound system, and flavor and component stability are guaranteed through a microcapsule technology; the final product is pure white, free of browning and good in stable storage performance, and has the triple functions of intestinal tract benefiting, trace element supplementing and low-GI diet.

Description

Technical Field

[0001] This invention relates to the field of food technology, and in particular to a compound low-GI yam powder with high retention of active ingredients and targeted probiotics, and its preparation method. Background Technology

[0002] With the increasing demand for healthy eating, low-GI foods are gaining more attention. Yam, a food and medicine of the same origin, is rich in functional components such as mucoprotein, yam polysaccharides, and diosgenin, offering benefits such as strengthening the spleen and stomach and aiding in blood sugar regulation. It is an excellent raw material for developing low-GI functional foods. However, fresh yams have a high water content, making them difficult to store and prone to spoilage. Current technologies mostly use drying processes to produce yam powder, which preserves flavor and nutrients and facilitates storage and transportation. Currently, yam powder processing and products suffer from several core technological challenges, including significant loss of heat-sensitive components, prominent issues with enzymatic browning and oxidation, limited functionality and poor palatability, and insufficient flavor and component stability.

[0003] While existing technologies have improved the process by using single color protection or low-temperature drying, they have not formed a collaborative innovation across the entire chain of "pretreatment-drying-compounding-encapsulation," and cannot simultaneously address the four core requirements of "high activity retention, low GI characteristics, targeted probiotics, and stable storage." There is an urgent need to develop an integrated innovative technology solution. Summary of the Invention

[0004] The purpose of this invention is to provide a method for preparing raw yam powder, which can significantly improve the retention rate of heat-sensitive components. It also provides a compound low-GI yam powder with high retention of active ingredients and targeted probiotics. This compound low-GI yam powder is white without browning, has good storage stability, and has the triple functions of "intestinal probiotics, trace element supplementation, and low-GI diet".

[0005] To achieve the above-mentioned objectives, the present invention provides the following technical solution: This invention provides a method for preparing raw yam powder, comprising the following steps: (1) Mix the yam with the compound color-protecting solution and sonicate it at 30~40℃ to obtain the treated yam; (2) The processed yam was treated in a pulsed electric field for 5-10 minutes to obtain the cell wall broken yam; (3) Dry and pulverize the broken yam to obtain raw yam powder.

[0006] Preferably, in step (1), the composite color-protecting liquid, using water as a solvent, comprises the following components at final concentrations: 0.1%~0.3% L-cysteine, 0.2%~0.5% ascorbic acid, and 0.3%~0.6% citric acid; The mass-to-volume ratio of the yam and the compound color-protecting liquid is 1g:3-5mL.

[0007] Preferably, in step (1), the power of the ultrasonic treatment is 200~300W; and the time of the ultrasonic treatment is 15~25min.

[0008] Preferably, in step (2), the electric field strength of the pulsed electric field is 20~30kV / cm; and the pulse frequency of the pulsed electric field is 50~100Hz.

[0009] Preferably, in step (3), the drying is vacuum microwave drying; the vacuum degree of the drying is 0.08~0.09MPa; the microwave power of the drying is 400~600W; the drying temperature is 50~60℃; and the drying time is 2~3h. The moisture content of the raw yam powder is 5% to 8%; the particle size of the raw yam powder is 80 to 100 mesh.

[0010] This invention also provides a compound low-GI yam powder with high retention of active ingredients and targeted probiotics, comprising a functional compound powder and a composite wall material; the mass ratio of the functional compound powder to the composite wall material is 100:5~8; The functional compound powder comprises the following components in parts by weight: 70-85 parts of raw yam powder, 10-20 parts of prebiotic components, 3-5 parts of natural sweetness and flavor components, and 1-2 parts of microencapsulated trace element components; The raw yam powder is prepared by the aforementioned preparation method.

[0011] Preferably, the composite wall material includes gum arabic, β-cyclodextrin, yam natural flavor extract, and water; The prebiotic component comprises resistant dextrin and inulin; the mass ratio of resistant dextrin to inulin is 1:1~2; The natural sweetness and flavor components include mogrosides and konjac flour; the mass ratio of mogrosides to konjac flour is 1:3~5. The microencapsulated trace element component includes microencapsulated ferric citrate and microencapsulated calcium carbonate; the mass ratio of microencapsulated ferric citrate to microencapsulated calcium carbonate is 1:0.8~1.2.

[0012] The present invention also provides a method for preparing the aforementioned compound low-GI yam powder, comprising the following steps: 1) Mix raw yam powder, prebiotic components, natural sweeteners and flavorings, and microencapsulated trace element components to obtain a functional compound powder; 2) The functional compound powder is coated with a composite wall material to obtain compound low-GI yam powder.

[0013] Preferably, in step 1), the mixing speed of the raw yam powder, prebiotic component, natural sweetness and flavor component, and microencapsulated trace element component is 15-20 rpm; the mixing time is 10-15 min.

[0014] Preferably, in step 2), the inlet air temperature of the coating treatment is 40~50℃; the atomization pressure of the coating treatment is 0.2~0.3MPa; and the spraying rate of the coating treatment is 5~8mL / min.

[0015] The beneficial effects of this invention are: This invention provides a method for preparing raw yam powder. This method, through the synergistic effect of "ultrasound-composite color-protecting solution treatment" and "low-temperature pulsed electric field-vacuum microwave combined drying," improves the retention rate of heat-sensitive components such as mucoprotein and yam polysaccharides by more than 30% compared to traditional processes, achieving a stable GI value <55, meeting low-GI food standards. Furthermore, the low-temperature pulsed electric field-vacuum microwave combined drying method is twice as efficient as traditional hot air drying, reducing energy consumption by 45%. This invention combines raw yam powder, prebiotic components, natural sweeteners and flavor components, and microencapsulated trace element components to prepare a functional compound powder. The functional compound powder is then coated with a composite wall material to obtain a compound low-GI yam powder. The prepared compound low-GI yam powder is white and free from browning (browning degree ΔE < 1.5), has a dissolving time of < 30 seconds, a smooth and sweet taste, and requires no added sucrose. It possesses three functions: intestinal health (probiotic proliferation rate > 2 times), trace element supplementation (bioavailability increased by 40%), and low-GI diet, making it suitable for people with diabetes, intestinal dysfunction, and trace element deficiencies. The compound low-GI yam powder retains > 88% of its flavor and < 5% of its functional components over 6 months, extending its shelf life to 12 months with good storage stability, meeting the needs of industrial distribution. Furthermore, the mixing and encapsulation processes allow for continuous production, making it valuable for large-scale promotion. Detailed Implementation

[0016] This invention provides a method for preparing raw yam powder, comprising the following steps: (1) Mix the yam with the compound color-protecting solution and sonicate it at 30~40℃ to obtain the treated yam; (2) The processed yam was treated in a pulsed electric field (PEF) for 5-10 minutes to obtain yam with broken cell walls; (3) Dry and pulverize the broken yam to obtain raw yam powder.

[0017] In this invention, yam is prepared by "ultrasonic color protection-low temperature combined drying" process, and its mucoprotein retention rate is >88%, yam polysaccharide retention rate is >90%, and the product GI value is <55.

[0018] In this invention, in step (1), the yam needs to be washed, peeled and cut into yam slices 3-5 mm thick before mixing with the compound color-protecting liquid; the thickness of the yam slices is preferably 4 mm. The preferred yam is the iron yam, with a starch content of 12% to 15%. The composite color-protecting liquid uses water as a solvent and comprises the following components at the following final concentrations: L-cysteine ​​0.1%~0.3%, preferably 0.2%, Ascorbic acid 0.2%~0.5%, preferably 0.3%~0.4%, more preferably 0.35%. Citric acid 0.3%~0.6%, preferably 0.4%~0.5%, more preferably 0.45%; The water is preferably deionized water; The mass-to-volume ratio of the yam and the compound color-protecting liquid is 1g:3-5mL, preferably 1g:4mL; Citric acid can inhibit browning of fresh-cut fruits and vegetables by lowering pH and inhibiting the activity of related oxidases. Ascorbic acid (AA) is a reducing agent that can reduce quinones to phenolic substances, thus serving as an effective browning inhibitor. L-cysteine ​​(L-cys), as a biologically active natural amino acid, has been widely used by researchers in the preservation of fresh-cut fruits and vegetables due to its highly efficient browning inhibitory effect.

[0019] In this invention, in step (1), the power of the ultrasonic treatment is 200~300W, preferably 230~270W, and more preferably 250W; the time of the ultrasonic treatment is 15~25min, preferably 18~22min, and more preferably 20min; the temperature of the ultrasonic treatment is preferably 33~37℃, and more preferably 35℃. The combination of compound color-protecting liquid and ultrasonic treatment can inhibit the activity of polyphenol oxidase (PPO) in yam by more than 92% and remove more than 80% of the free starch on the surface.

[0020] In this invention, in step (2), the electric field strength of the pulsed electric field is 20~30kV / cm, preferably 23~27kV / cm, and more preferably 25kV / cm; the pulse frequency of the pulsed electric field is 50~100Hz, preferably 65~85Hz, and more preferably 75Hz; the processing time in the pulsed electric field is preferably 7~8min, and more preferably 7.5min. After the processed yam was treated in a pulsed electric field, the cell wall disruption rate of the yam was >90%.

[0021] In this invention, in step (3), the drying is vacuum microwave drying; the vacuum degree of the drying is 0.08~0.09MPa, preferably 0.085MPa; the microwave power of the drying is 400~600W, preferably 450~550W, more preferably 500W; the drying temperature is 50~60℃, preferably 53~57℃, more preferably 55℃; the drying time is 2~3h, preferably 2.5h. Vacuum microwave drying is twice as efficient as traditional hot air drying and reduces energy consumption by 45%. The moisture content of the raw yam powder is 5%~8%, preferably 6%~7%, and more preferably 6.5%; the particle size of the raw yam powder is 80~100 mesh, preferably 85~95 mesh, and more preferably 90 mesh.

[0022] The present invention also provides a compound low-GI yam powder with high retention of active ingredients and targeted probiotics, comprising a functional compound powder and a composite wall material; the mass ratio of the functional compound powder and the composite wall material is 100:5~8, preferably 100:6~7, and more preferably 100:6.5; The functional compound powder comprises the following components in parts by weight: The raw yam powder contains 70-85 parts, preferably 75-80 parts, and even more preferably 77.5 parts; The prebiotic component is 10-20 parts, preferably 13-17 parts, and more preferably 15 parts. 3 to 5 parts of natural sweetness and flavor components, preferably 4 parts. 1-2 parts of microencapsulated trace element components, preferably 1.5 parts; The raw yam powder is prepared by the aforementioned preparation method; The synergistic effect of native yam powder, prebiotic components, natural sweeteners and flavorings, and microencapsulated trace element components enables the integration of functions such as high retention of mucoprotein and polysaccharides, low GI properties, intestinal health benefits, and stable supplementation of trace elements.

[0023] In this invention, the composite wall material comprises gum arabic, β-cyclodextrin, natural flavor extract of yam, and water; The water is preferably deionized water; The preparation method of the composite wall material includes the following steps: mixing gum arabic and β-cyclodextrin at a mass ratio of 2:1, adding water to prepare a 10%~15% composite solution, and adding 0.5%~1% of yam natural flavor extract to prepare the composite wall material. The concentration of the composite solution is preferably 12% to 13%, more preferably 12.5%; The amount of the yam natural flavor extract added is preferably 0.7% to 0.8%, more preferably 0.75%; The natural flavor extract of yam can directly replenish and lock in the characteristic flavor substances of yam lost during processing. At the same time, it forms a "active adsorption-slow release" synergistic effect with β-cyclodextrin (which has a hydrophobic cavity structure), thereby improving the "homogeneous compatibility" of the wall material and functional compound powder and avoiding the conflict of flavors from different sources: β-cyclodextrin firmly adsorbs the flavor molecules in the extract through the cavity, preventing them from volatilizing during the coating process; during subsequent storage, the flavor substances in the extract can be slowly released by relying on the microcapsule membrane (the dense barrier formed by gum arabic), ultimately ensuring that the product maintains a rich and pure yam flavor throughout the entire process.

[0024] The preparation method of the yam natural flavor extract is as follows: After washing and slicing the yam, mix it with a color-protecting solution (using deionized water as solvent, including the following components at final concentrations: 0.2% L-cysteine, 0.35% ascorbic acid, and 0.45% citric acid) at a mass-to-volume ratio of 1g:4mL. The mixture is then ultrasonically extracted for 7.5min at a power of 75Hz and a temperature of 35℃ to obtain the yam extract pulp. The yam extract pulp is then microwave-dried at a microwave power of 500W and a temperature of 55℃ for 2.5h, and then passed through a 90-mesh sieve to obtain the yam natural flavor extract.

[0025] This invention uses gum arabic encapsulation, which can avoid complexation reaction with yam polysaccharides and increase the bioavailability of trace elements by more than 40%. The prebiotic component comprises resistant dextrin and inulin; the mass ratio of resistant dextrin to inulin is 1:1 to 2, preferably 1:1.5; The prebiotic component can increase the proliferation rate of intestinal bifidobacteria and lactic acid bacteria by more than 2 times, and resistant dextrin can further reduce the product's GI value; The natural sweetness and flavor components include mogrosides and konjac flour; the mass ratio of mogrosides to konjac flour is 1:3~5, preferably 1:4; Mogroside, also known as monk fruit glycoside (or monk fruit sweetener), is abundant in plants and highly water-soluble. Its sweetness is 300 times that of sucrose. It has the effects of clearing heat, moistening the lungs, relieving cough, and promoting bowel movements. It also has preventive and therapeutic effects on obesity, constipation, and diabetes. It provides a high-sweetness, zero-calorie, low-GI sweetness; its sweetness is 200-300 times that of sucrose, requiring only a very small amount to achieve the desired sweetness, perfectly meeting the requirements of low-GI foods. Konjac powder can physically coat taste buds, delay the release of sweetness, and significantly mask unpleasant aftertastes. In addition, glucomannan in konjac powder can improve solubility and smooth texture after mixing, while also enhancing satiety. The microencapsulated trace element component includes microencapsulated ferric citrate and microencapsulated calcium carbonate; the mass ratio of microencapsulated ferric citrate to microencapsulated calcium carbonate is 1:0.8~1.2, preferably 1:0.9~1.1, and more preferably 1:1; The preparation method of the microencapsulated ferric citrate includes the following steps: a. Mix gum arabic and β-cyclodextrin at a mass ratio of 2:1, add deionized water to prepare a 10%~15% wall material solution, and stir at 40~50℃ until completely dissolved; b. Mix the iron citrate powder and the wall material solution at a mass ratio of 1:1~2 (core: wall material), and emulsify in a high-speed shear machine at 8000~10000 rpm for 5~10 minutes to form a uniform suspension; c. Spray dry the suspension, with the inlet temperature controlled at 150~180℃, the outlet temperature at 70~90℃, and the atomization pressure at 0.2~0.3MPa, to obtain microencapsulated iron citrate powder with a particle size distribution of 80~100 mesh. The concentration of the wall material solution is preferably 12% to 13%, more preferably 12.5%; The stirring temperature is preferably 43~47℃, and more preferably 45℃; The preferred mass ratio of ferric citrate powder to wall material solution is 1:1.5; The emulsification speed is preferably 8500~9500 rpm, more preferably 9000 rpm; The emulsification time is preferably 7-8 minutes, more preferably 7.5 minutes; The inlet temperature is preferably 160~170℃, and more preferably 165℃; The outlet temperature is preferably 75~85℃, and more preferably 80℃; The preferred atomization pressure is 0.25 MPa; The preferred particle size distribution is 85-95 mesh, more preferably 90 mesh; The preparation method of the microencapsulated calcium carbonate includes the following steps: a. Mix gum arabic and β-cyclodextrin at a mass ratio of 2:1, add deionized water to prepare a 10%~15% wall material solution, and stir at 40~50℃ until completely dissolved; b. Mix calcium carbonate powder and wall material solution at a mass ratio of 1:1~2 (core: wall material), and emulsify in a high-speed shear machine at 8000~10000 rpm for 5~10 minutes to form a uniform suspension; c. Spray dry the suspension, with the inlet temperature controlled at 150~180℃, the outlet temperature at 70~90℃, and the atomization pressure at 0.2~0.3MPa, to obtain microencapsulated calcium carbonate powder with a particle size distribution of 80~100 mesh; The concentration of the wall material solution is preferably 12% to 13%, more preferably 12.5%; The stirring temperature is preferably 43~47℃, and more preferably 45℃; The preferred mass ratio of ferric citrate powder to wall material solution is 1:1.5; The emulsification speed is preferably 8500~9500 rpm, more preferably 9000 rpm; The emulsification time is preferably 7-8 minutes, more preferably 7.5 minutes; The inlet temperature is preferably 160~170℃, and more preferably 165℃; The outlet temperature is preferably 75~85℃, and more preferably 80℃; The preferred atomization pressure is 0.25 MPa; The preferred particle size distribution is 85-95 mesh, more preferably 90 mesh; The present invention also provides a method for preparing the aforementioned compound low-GI yam powder, comprising the following steps: 1) Mix raw yam powder, prebiotic components, natural sweeteners and flavorings, and microencapsulated trace element components to obtain a functional compound powder; 2) The functional compound powder is coated with a composite wall material to obtain compound low-GI yam powder.

[0026] In this invention, in step 1), the mixing speed of the raw yam powder, prebiotic component, natural sweetness and flavor component, and microencapsulated trace element component is 15-20 rpm, preferably 17-18 rpm, and more preferably 18 rpm; the mixing time is 10-15 min, preferably 12-13 min, and more preferably 12 min.

[0027] The uniformity variation coefficient of the mixed powder is <3%, the mixing and dissolving time is shortened to 25~30s, and there is no clumping.

[0028] In this invention, in step 2), the inlet air temperature of the coating treatment is 40~50℃, preferably 43~47℃, and more preferably 45℃; the atomization pressure of the coating treatment is 0.2~0.3MPa, preferably 0.25MPa; and the spray rate of the coating treatment is 5~8mL / min, preferably 6~7mL / min, and more preferably 6.5mL / min.

[0029] In this invention, composite wall material is uniformly sprayed onto the surface of functional compound powder to form a microcapsule membrane with a thickness of 5-10 μm, which can maintain the characteristic flavor of yam for 6 months with a retention rate of >88% and a trace element loss rate of <5%. The coating thickness is preferably 7~8μm, and more preferably 7.5μm.

[0030] The technical solutions provided by the present invention will be described in detail below with reference to the embodiments, but they should not be construed as limiting the scope of protection of the present invention.

[0031] In the embodiments and comparative examples of the present invention, the preparation methods of microencapsulated ferric citrate, microencapsulated calcium carbonate, natural flavor extract of yam, and composite wall material are as follows: The microencapsulated ferric citrate: a. Mix gum arabic and β-cyclodextrin at a mass ratio of 2:1, add deionized water to prepare a 10% wall material solution, and stir at 45°C until completely dissolved; b. Mix the iron citrate powder and the wall material solution at a mass ratio of 1:1, and emulsify them at 9000 pm for 10 min in a high-speed shear machine to form a uniform suspension; c. Spray dry the suspension with the inlet temperature controlled at 165℃, the outlet temperature at 80℃, and the atomization pressure at 0.3MPa to obtain microencapsulated iron citrate powder with a particle size distribution of 100 mesh. Microencapsulated calcium carbonate: a. Mix gum arabic and β-cyclodextrin at a mass ratio of 2:1, add deionized water to prepare a 10% wall material solution, and stir at 45°C until completely dissolved; b. Mix calcium carbonate powder and wall material solution at a mass ratio of 1:1, and emulsify in a high-speed shear machine at 9000 rpm for 10 min to form a uniform suspension; c. Spray dry the suspension, with the inlet temperature controlled at 165℃, the outlet temperature at 80℃, and the atomization pressure at 0.3MPa, to obtain microencapsulated calcium carbonate powder with a particle size distribution of 100 mesh. Yam natural flavor extract: After washing and slicing yam, mix it with color-protecting solution (using deionized water as solvent, including the following components at final concentrations: 0.2% L-cysteine, 0.35% ascorbic acid, and 0.45% citric acid) at a mass-to-volume ratio of 1g:4mL. Extract the extract using ultrasound at 75Hz and 35℃ for 7.5min to obtain yam extract pulp. Microwave dry the yam extract pulp at 500W and 55℃ for 2.5h, then pass it through a 90-mesh sieve to obtain the yam natural flavor extract. Composite wall material: Gum arabic and β-cyclodextrin are mixed at a mass ratio of 2:1, and deionized water is added to prepare a 10% composite solution. At the same time, 0.75% of yam natural flavor extract is added to prepare the composite wall material.

[0032] Example 1: A compound low-GI yam powder with high retention of active ingredients and targeted probiotics

[0033] Raw yam powder: (1) Take 1000g of fresh iron yam, wash and peel it, and cut it into 3mm thick yam slices. Then, soak it in a compound color-protecting solution (using deionized water as solvent, including the following components at the final concentration: 0.1% L-cysteine, 0.2% ascorbic acid, and 0.3% citric acid) at a mass-volume ratio of 1g:3mL. Place it in an ultrasonic device and ultrasonically treat it for 25min at a power of 200W and a temperature of 30℃ to obtain the treated yam. (2) The processed yam was transferred into a PEF device and treated for 10 minutes under the conditions of electric field strength of 20kV / cm and pulse frequency of 50Hz to obtain the cell wall broken yam; (3) Place the broken yam in a vacuum microwave dryer and dry it for 3 hours under the conditions of vacuum degree 0.08MPa, microwave power 400W and temperature 55℃. Then, pulverize it to a particle size of 80 mesh using an ultra-micro pulverizer to obtain raw yam powder (moisture content 8%). Highly active ingredient retention and targeted probiotic blend of low-GI yam powder: 1) Place 850g of raw yam powder, 50g of resistant dextrin, 50g of inulin, 7.5g of mogroside, 22.5g of konjac powder, 10g of microencapsulated ferric citrate, and 10g of microencapsulated calcium carbonate in a three-dimensional high-speed vortex mixer and mix at 15 rpm for 15 min to obtain a functional compound powder (uniformity variation coefficient 2.8%). 2) The functional compound powder is added as the core into the fluidized bed coating machine. The air inlet temperature is controlled at 40℃, the atomization pressure is 0.2MPa, and the spraying rate is 5mL / min. The composite wall material is uniformly sprayed on the surface of the functional compound powder to form a 5μm thick microcapsule membrane, thus obtaining compound low-GI yam powder.

[0034] Example 2: A compound low-GI yam powder with high retention of active ingredients and targeted probiotics

[0035] Raw yam powder: (1) Take 1000g of fresh iron yam, wash and peel it, and cut it into 4mm thick yam slices. Then, soak it in a compound color-protecting solution (using deionized water as solvent, including the following components at the final concentration: 0.2% L-cysteine, 0.3% ascorbic acid, and 0.4% citric acid) at a mass-volume ratio of 1g:4mL. Place it in an ultrasonic device and ultrasonically treat it for 20min at a power of 250W and a temperature of 35℃ to obtain the treated yam. (2) The processed yam was transferred into a PEF device and treated for 8 minutes under the conditions of electric field strength of 25kV / cm and pulse frequency of 80Hz to obtain the cell wall broken yam; (3) Place the broken yam in a vacuum microwave dryer and dry it for 2.5 hours under the conditions of vacuum degree 0.085MPa, microwave power 500W and temperature 55℃. Then, pulverize it to a particle size of 90 mesh using an ultra-micro pulverizer to obtain raw yam powder (moisture content 6.5%). Highly active ingredient retention and targeted probiotic blend of low-GI yam powder: 1) Place 800g of raw yam powder, 60g of resistant dextrin, 90g of inulin, 8g of mogroside, 32g of konjac powder, 5g of microencapsulated ferric citrate and 5g of microencapsulated calcium carbonate in a three-dimensional high-speed vortex mixer and mix at 18 rpm for 12 minutes to obtain functional compound powder (uniformity variation coefficient 2.1%). 2) The functional compound powder is added as the core into the fluidized bed coating machine. The air inlet temperature is controlled at 45℃, the atomization pressure is 0.25MPa, and the spraying rate is 6.5mL / min. The composite wall material is uniformly sprayed on the surface of the functional compound powder to form an 8μm thick microcapsule membrane, thus obtaining compound low-GI yam powder.

[0036] Example 3: A compound low-GI yam powder with high retention of active ingredients and targeted probiotics

[0037] Raw yam powder: (1) Take 1000g of fresh iron yam, wash and peel it, and cut it into 5mm thick yam slices. Then, soak it in a compound color-protecting solution (using deionized water as solvent, including the following components at the final concentration: 0.3% L-cysteine, 0.5% ascorbic acid, and 0.6% citric acid) at a mass-volume ratio of 1g:5mL. Place it in an ultrasonic device and ultrasonically treat it for 15min at a power of 300W and a temperature of 40℃ to obtain the treated yam. (2) The processed yam was transferred into a PEF device and treated for 5 minutes under the conditions of electric field strength of 30kV / cm and pulse frequency of 100Hz to obtain the cell wall broken yam; (3) Place the broken yam in a vacuum microwave dryer and dry it for 2 hours under the conditions of vacuum degree 0.09MPa, microwave power 600W and temperature 60℃. Then, pulverize it to a particle size of 100 mesh using an ultra-micro pulverizer to obtain raw yam powder (moisture content 5%). Highly active ingredient retention and targeted probiotic blend of low-GI yam powder: 1) Place 700g of raw yam powder, 100g of resistant dextrin, 100g of inulin, 8.34g of mogroside, 41.67g of konjac powder, 5g of microencapsulated ferric citrate, and 5g of microencapsulated calcium carbonate in a three-dimensional high-speed vortex mixer and mix at 20 rpm for 10 minutes to obtain a functional compound powder (uniformity variation coefficient 1.9%). 2) The functional compound powder is added as the core into the fluidized bed coating machine. The air inlet temperature is controlled at 50℃, the atomization pressure is 0.3MPa, and the spraying rate is 8mL / min. The composite wall material is uniformly sprayed on the surface of the functional compound powder to form a 10μm thick microcapsule membrane, thus obtaining compound low-GI yam powder.

[0038] Comparative Example 1

[0039] Raw yam powder: Take 1000g of fresh iron yam, wash and peel it, and cut it into 4mm thick yam slices. Place the yam slices in a 70℃ hot air drying oven and dry for 6 hours. Then, pulverize them with an ultra-fine pulverizer to a particle size of 90 mesh to obtain raw yam powder (moisture content 6.5%). The preparation steps of the yam powder are the same as those in Example 2 (preparation steps of compound low-GI yam powder with high activity retention and targeted probiotics).

[0040] Comparative Example 2

[0041] The preparation method of raw yam powder is the same as in Example 2; Yam powder: Referring to Example 2, the components of the functional compound powder were adjusted to: 950g of raw yam powder, 8g of mogroside, 32g of konjac powder, 5g of microencapsulated ferric citrate and 5g of microencapsulated calcium carbonate (without adding prebiotic components). Other components and preparation steps were the same as in Example 2 (preparation steps of compound low-GI yam powder with high-activity ingredients retention and targeted probiotics).

[0042] Comparative Example 3

[0043] The preparation method of raw yam powder is the same as in Example 2; Yam powder: Place 800g of raw yam powder, 60g of resistant dextrin, 90g of inulin, 8g of mogroside, 32g of konjac powder, 5g of ferric citrate and 5g of calcium carbonate in a three-dimensional high-speed vortex mixer and mix at 18 rpm for 12 minutes to obtain yam powder (uniformity variation coefficient 2.1%).

[0044] Comparative Example 4

[0045] The preparation method of raw yam powder is the same as in Example 2; Yam powder: Refer to Example 2, the difference from Example 2 is that the amount of raw yam powder added is adjusted to 650g, the amount of resistant dextrin added is adjusted to 120g, the amount of inulin added is adjusted to 180g (the amount of prebiotic component added is adjusted to 30%), the amount of other components added and the preparation steps are the same as in Example 2 (the preparation steps of compound low-GI yam powder with high activity retention and targeted probiotics).

[0046] Experimental Example 1

[0047] The results of the retention rates of active ingredients (mucoprotein retention rate and yam polysaccharide retention rate), GI value, intestinal probiotic properties (bifidobacterium proliferation rate), stability properties (6-month flavor retention rate and trace element utilization rate), sensory and practical properties (browning degree ΔE, reconstitution and dissolution time) of the compound low-GI yam powder described in Examples 1-3 and the yam powder prepared in Comparative Documents 1-4 are shown in Table 2.

[0048] The specific measurement method is as follows: Mucin retention rate (%): determined using the Bixbio Bradford method protein content assay kit.

[0049] Yam polysaccharide retention rate (%): The retention rate before and after processing was calculated with reference to NY / T 1676-2008 "Determination of crude polysaccharide content in edible fungi".

[0050] Determination of starch hydrolysis index and predicted glycemic index: Buffer 1: Take 1.75 mL of concentrated hydrochloric acid and dilute to 1 L with deionized water; Buffer 2: Dissolve 11.8 mL of glacial acetic acid in 800 mL of deionized water, add 2 mol / L NaOH solution to adjust the pH to 6, then add 4 mL of 1 mol / L CaCl2 solution and 100 μL of 4.9 mol / L MgCl2 solution, and bring the volume to 1 L with deionized water. Enzyme A: Dissolve 6.25 mg of pepsin (P6887) in 50 mL of Buffer 1; Enzyme B: Dissolve 75 mg of pancreatic mixed enzyme (P1750) and 0.3 mL of α-glucosidase solution in 25 mL of Buffer 2; Using the compound low-GI yam powder obtained in the examples and comparative examples as samples, 150-200 mg (based on the carbohydrate content of the sample) of the sample was placed in a 25 mL centrifuge tube with three glass beads. After adding 2 mL of enzyme A, the sample was placed in a constant temperature shaker at 37 °C and 150 r / min for 30 min. Then, 4 mL of buffer 2 was added and shaken for 5 min. After that, 1 mL of enzyme B was added and the timing was started. 100 μL of digestion solution was taken out at 0, 30, 60, 90, 120 and 180 min respectively. The enzyme was inactivated by boiling water bath for 5 min. 150 μL of DNS solution was added and the sample was boiled in water bath again for 5 min for color development. The glucose content was then determined. Sample size (μg) = 5000 ÷ carbohydrate content; Starch hydrolysis rate = glucose content at sampling point / total starch content; With the hydrolysis time of the sample as the x-axis and the starch hydrolysis rate as the y-axis, the area under the hydrolysis curve (AUC1) was analyzed using Origin 2019, and the area under the hydrolysis curve of pregelatinized starch was used as the control (AUC0). The starch hydrolysis index HI and the predicted glycemic index (pGI) were calculated. HI = (AUC1 / AUC0) × 100%; pGI = 0.862HI + 8.192.

[0051] Bifidobacterium proliferation rate (fold): The proliferation rate of Bifidobacterium was determined according to GB 4789.34-2016. Using the sample as the sole carbon source, Bifidobacterium was inoculated under anaerobic conditions and cultured at 37℃ for 24 h. Samples were taken at 0 h and 24 h of culture, and plate counting was performed using the MRS medium specified in this standard to calculate the proliferation fold (N24 / N0).

[0052] 6-month flavor retention rate (%): Flavor intensity retention rate (%) = (Average flavor intensity score after 6 months / Initial average flavor intensity score) × 100%; The method for calculating the average flavor intensity score is as follows: Evaluation personnel: Ten professionally trained sensory evaluators (aged 20-50, male-to-female ratio 1:1) with no history of allergy to yam or related components; Sample preparation: Take 12g of each sample, add 160mL of 25℃ deionized water, stir at 150rpm until dissolved, place in a uniform white container, label it, and conduct blind evaluation; Scoring calculation: Score for each dimension = (sum of scores from 10 evaluators / 10) × weight, total sensory score = sum of scores for each dimension (maximum score 10); the evaluation criteria are shown in Table 1; The qualification standard is: the total sensory score is ≥8.0 points, and the individual scores of the three dimensions of color and appearance, mixing characteristics and flavor and taste are all ≥7.5 points, which meets the core requirements of the patented product of "good palatability and stable quality".

[0053] Table 1 Sensory Evaluation Form

[0054] Micronutrient utilization rate (%): Micronutrient utilization rate was determined by in vitro simulated gastrointestinal digestion; the digestion process was carried out according to the low GI determination method mentioned above; after digestion, the dialysate was digested and the contents of iron and calcium were determined according to the first method (inductively coupled plasma mass spectrometry) of GB 5009.268-2016 "National Food Safety Standard - Determination of Multiple Elements in Food".

[0055] Browning degree ΔE: Browning degree ΔE was measured using a colorimeter.

[0056] Dissolution time (s): Pour 12g of the test substance into 160mL of water at 25℃, stir at 150rpm, and record the time for complete dissolution.

[0057] Table 2 Test Results

[0058] As shown in Table 2, Comparative Example 1, lacking the "ultrasound-PEF-vacuum microwave" process, had a mucoprotein / polysaccharide retention rate of only 58.6% / 62.3% (compared to 92.5% / 94.8% in Example 2), and its browning degree ΔE increased to 4.8, proving that the process is the core of "high activity retention + anti-browning". Comparative Example 2, lacking prebiotics, had a GI value of 68.7 (>55), and its Bifidobacterium proliferation rate decreased by 1.2 times, proving that prebiotics are the key to "low GI + gut health". Comparative Example 3, without encapsulation, had a flavor retention rate of only 42.8% and a trace element utilization rate of 45.3% after 6 months (compared to 91.5% / 86.7% in Example 2), verifying the role of microcapsules in stability. Comparative Example 4 had excessive prebiotics, increasing the dissolution time to 58s (compared to 26s in Example 2), and decreasing sensory quality, proving that only the 10%~20% prebiotic range claimed can balance function and practicality.

[0059] As can be seen from the above embodiments, the present invention provides a compound low-GI yam powder with high retention of active ingredients and targeted probiotics, and its preparation method. The present invention solves the problems of nutrient loss and browning caused by traditional drying through a synergistic processing technology. The compound system achieves targeted intestinal probiotics and low-GI functions, and microencapsulation technology ensures flavor and component stability. The final product exhibits improved retention rates of mucoprotein and polysaccharides, with a GI value <55 and a flavor retention rate >88% after 6 months, making it suitable for people with gut health and low-GI dietary needs.

[0060] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing raw yam powder, characterized in that, Includes the following steps: (1) Mix the yam with the compound color-protecting solution and sonicate it at 30~40℃ to obtain the treated yam; (2) The processed yam was treated in a pulsed electric field for 5-10 minutes to obtain the cell wall broken yam; (3) Dry and pulverize the broken yam to obtain raw yam powder.

2. The preparation method according to claim 1, characterized in that, In step (1), the composite color-protecting liquid, using water as a solvent, comprises the following components at final concentrations: 0.1%~0.3% L-cysteine, 0.2%~0.5% ascorbic acid, and 0.3%~0.6% citric acid; The mass-to-volume ratio of the yam and the compound color-protecting liquid is 1g:3-5mL.

3. The preparation method according to claim 1, characterized in that, In step (1), the power of the ultrasonic treatment is 200~300W; the time of the ultrasonic treatment is 15~25min.

4. The preparation method according to claim 1, characterized in that, In step (2), the electric field strength of the pulsed electric field is 20~30kV / cm; the pulse frequency of the pulsed electric field is 50~100Hz.

5. The preparation method according to claim 1, characterized in that, In step (3), the drying is vacuum microwave drying; the vacuum degree of the drying is 0.08~0.09MPa; the microwave power of the drying is 400~600W; the drying temperature is 50~60℃; and the drying time is 2~3h. The moisture content of the raw yam powder is 5% to 8%; the particle size of the raw yam powder is 80 to 100 mesh.

6. A compound low-GI yam powder with high-activity ingredient retention and targeted probiotics, characterized in that, It includes functional compound powder and composite wall material; the mass ratio of the functional compound powder and composite wall material is 100:5~8; The functional compound powder comprises the following components in parts by weight: 70-85 parts of raw yam powder, 10-20 parts of prebiotic components, 3-5 parts of natural sweetness and flavor components, and 1-2 parts of microencapsulated trace element components; The raw yam powder is prepared by the preparation method described in any one of claims 1 to 5.

7. The compound low-GI yam powder according to claim 6, characterized in that, The composite wall material includes gum arabic, β-cyclodextrin, natural flavor extract of yam and water; The prebiotic component comprises resistant dextrin and inulin; the mass ratio of resistant dextrin to inulin is 1:1~2; The natural sweetness and flavor components include mogrosides and konjac flour; the mass ratio of mogrosides to konjac flour is 1:3~5. The microencapsulated trace element component includes microencapsulated ferric citrate and microencapsulated calcium carbonate; the mass ratio of microencapsulated ferric citrate to microencapsulated calcium carbonate is 1:0.8~1.

2.

8. The method for preparing the compound low-GI yam powder according to claim 6 or 7, characterized in that, Includes the following steps: 1) Mix raw yam powder, prebiotic components, natural sweeteners and flavorings, and microencapsulated trace element components to obtain a functional compound powder; 2) The functional compound powder is coated with a composite wall material to obtain compound low-GI yam powder.

9. The preparation method according to claim 8, characterized in that, In step 1), the mixing speed of the raw yam powder, prebiotic component, natural sweetness and flavor component, and microencapsulated trace element component is 15-20 rpm; the mixing time is 10-15 min.

10. The preparation method according to claim 9, characterized in that, In step 2), the inlet air temperature for the coating treatment is 40~50℃; the atomization pressure for the coating treatment is 0.2~0.3MPa; and the spray rate for the coating treatment is 5~8mL / min.

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