Rhizoma polygonati crisp chips and preparation method thereof

Abstract

The invention belongs to the technical field of food processing, and particularly relates to rhizoma polygonati crisp chips and a preparation method thereof. The invention provides a pretreatment method of polygonatum sibiricum. The pretreatment method comprises the following steps: pretreating polygonatum sibiricum by utilizing steaming and drying circulation; the steaming time is 2 to 4 hours, and the steaming temperature is 90 to 110 DEG C; the drying temperature ranges from 40 DEG C to 50 DEG C, and the drying time ranges from 1.5 h to 2 h. The pretreatment method is simple to operate and low in cost, nutritional ingredients such as polysaccharide, saponin, flavone and polyphenol can be effectively reserved, and the prepared rhizoma polygonati crisp chips are crisp in taste, easy to chew and free of irritation.

Description

Technical Field

[0001] The invention belongs to the technical field of food processing, and particularly relates to a polygonatum crisp slice and a preparation method thereof. Background Art

[0002] As a traditional Chinese medicine with both medicinal and edible properties, Polygonatum sibiricum has a long history of use as a tonic in my country. Polygonatum sibiricum contains characteristic active ingredients such as polysaccharides, saponins, flavonoids, polyphenols, etc., and has a wide range of pharmacological activities. With the advancement of science and technology, the medicinal and edible value of Polygonatum sibiricum in lowering blood sugar, lowering blood lipids, and enhancing immunity has been confirmed by a large number of studies.

[0003] Polygonatum sibiricum has a relatively high total sugar content, with the total sugar content of raw Polygonatum sibiricum reaching 50% to 60%. The inventor has tried to use the traditional "nine steaming and nine processing" method of Polygonatum sibiricum, that is, repeated steaming combined with drying cycles, but since the drying process generally adopts the form of long-term natural air drying or hot air drying, wrinkling is very likely to occur; the high sugar content causes the taste of Polygonatum sibiricum slices to become hard, and there is a sticky taste after chewing, affecting the ready-to-eat quality of Polygonatum sibiricum slices; at the same time, the repeated steaming and drying process leads to the loss of active ingredients in Polygonatum sibiricum, and the content of some nutrients such as polysaccharides is significantly reduced.

[0004] At present, the prior art also discloses some methods for improving the taste of polygonatum crispy slices, such as the invention patent with publication number CN112841641A, which improves the taste by adding enzyme preparations during the processing to enzymatically hydrolyze cellulose and other components that affect the taste of polygonatum; however, the cost of adding enzyme preparations and other reagents is high and the processing efficiency is low. In addition, the invention patent application with publication number CN114747762A uses steam explosion pretreatment, micro-pressure steaming combined with microwave drying to process low-HMF polygonatum products; however, the steam explosion pretreatment operation is complicated and the cost is also high. Summary of the invention

[0005] The object of the present invention is to provide a polygonatum crisp slice and a preparation method thereof. The pretreatment method is simple to operate, low in cost, and can effectively retain nutrients such as polysaccharides, saponins, flavonoids and polyphenols. The prepared polygonatum crisp slice has a crisp taste, is easy to chew, and is non-irritating.

[0006] The invention provides a method for pretreating polygonatum, comprising the following steps: pretreating polygonatum by steaming and drying cycles; the steaming time is 2-4 hours, the steaming temperature is 90-110 DEG C; the drying temperature is 40-50 DEG C, and the drying time is 1.5-2 hours.

[0007] As a preferred embodiment, the number of cycles is 1 to 3 times.

[0008] As a preferred solution, the relative humidity of the steaming is 80% to 90%.

[0009] The present invention provides application of the above-mentioned pretreatment method in preparing polygonatum sibiricum products.

[0010] As a preferred solution, the polygonatum product includes: polygonatum slices.

[0011] The invention provides a method for preparing polygonatum crisp slices, comprising the following steps: pretreating polygonatum by the above-mentioned pretreating method, and freeze-drying to obtain polygonatum crisp slices.

[0012] As a preferred solution, the water content of the polygonatum crisp slices is 6% to 7%.

[0013] As a preferred embodiment, the freeze-drying temperature is -60 to -50°C, and the freeze-drying time is 40 to 50 hours.

[0014] As a preferred embodiment, the freeze-drying process further includes pre-freezing; the pre-freezing temperature is -85 to -75°C, and the pre-freezing time is 20 to 30 hours.

[0015] The invention provides polygonatum crispy slices prepared by the above-mentioned preparation method.

[0016] Beneficial effects: The present invention provides a method for pretreating polygonatum, which utilizes steaming and drying cycles to pretreat polygonatum. The operation is simple and the cost is low. It not only effectively retains nutrients such as polysaccharides, saponins, flavonoids, polyphenols, etc., but also effectively improves the taste of instant polygonatum crisps. The present invention breaks the traditional processing concept of polygonatum, that is, only polygonatum that has been steamed nine times and dried nine times has high medicinal value and nutritional value. The present invention utilizes steaming and drying cycles to pretreat polygonatum, and only needs 1 to 3 cycles. The irritation of raw polygonatum can also be eliminated. The polygonatum crisps prepared from the treated polygonatum are rich in nutrition, crisp in taste, easy to chew, and non-irritating.

[0017] The present invention provides an application of the above-mentioned pretreatment method in the preparation of polygonatum products. The polygonatum after processing using the pretreatment method of steaming and drying cycles provided by the present invention can effectively retain nutritional components such as polysaccharides, saponins, flavonoids, polyphenols, etc.

[0018] The present invention provides a method for preparing polygonatum crisp slices, and provides a method for preparing polygonatum crisp slices by combining steaming and drying cycles with freeze drying. While retaining the nutrients such as polysaccharides, saponins, flavonoids, and polyphenols through the pretreatment method of the steaming and drying cycles, the freeze drying technology significantly improves the taste of the instant polygonatum crisp slices, and effectively solves the problem that polygonatum slices are prone to shrinkage during the drying process due to the high sugar content, thereby causing the polygonatum slices to have a poor taste and stick to the teeth when chewed. The preparation method of the present invention has a simple process, concise steps, simple operation, low requirements on production equipment, and reduced energy consumption, and is more suitable for industrial production.

[0019] The invention provides polygonatum crisp slices prepared by the preparation method. The prepared polygonatum crisp slices are rich in nutrition, crisp in taste, easy to chew, non-irritating, green and healthy, and low in cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 The polygonatum crisp slices prepared in Examples 1 to 4;

[0021] Figure 2 The polygonatum crisp slices are prepared in comparative examples 1 to 4. DETAILED DESCRIPTION

[0022] The invention provides a method for pretreating polygonatum, comprising the following steps: pretreating polygonatum by steaming and drying cycles; the steaming time is 2-4 hours, the steaming temperature is 90-110 DEG C; the drying temperature is 40-50 DEG C, and the drying time is 1.5-2 hours.

[0023] As a specific implementation method, the method also includes washing and slicing the polygonatum before pretreatment. In the present invention, fresh rhizomes of polygonatum from Jiuhua Mountain can be selected for washing. The example of washing is to remove the roots and sludge on the surface of polygonatum. The example of slicing is to slice the washed rhizomes of polygonatum. The thickness of the slices can be 2 to 4 mm. Drying at this thickness is conducive to uniform heating of the polygonatum slices, which in turn helps the migration and diffusion of internal moisture and reduces energy consumption. If the thickness is increased, it may cause the finished product to shrink and have a sticky taste. In one embodiment, a slicer can be used for slicing.

[0024] As a specific implementation method, the sliced ​​polygonatum is first steamed, and then the steamed polygonatum is dried, and then steamed again, and then dried, and so on. The steaming time of the present invention can be 2 to 4 hours, such as 2 hours, 2.5 hours, 3 hours, 3.5 hours, and 4 hours; the steaming temperature can be 90 to 110°C, such as 90°C, 95°C, 100°C, 105°C, and 110°C; the relative humidity of the steaming can be 80% to 90%, such as 85%; the steaming process has a certain effect on the enrichment of nutrients such as flavonoids, saponins, and free phenols, as well as the reduction of the texture hardness of the slices. If the steaming time is too short or too long, the nutrient content will be reduced and the taste quality of the slices will be reduced. The temperature of the drying of the present invention can be 40-50°C, for example, 40°C, 45°C, 50°C; the time of the drying can be 1.5-2h, for example, 1.5h, 1.8h, 2h; the relative humidity of the drying can be 5%-15%, for example, 10%; by drying for a short time, part of the moisture of the slices is removed, which is convenient for subsequent processing. If the drying time is too long, the shrinkage of the slice surface will be aggravated, and if the time is too short, the nutrient enrichment effect will be weakened, affecting the nutrient content. In one embodiment, hot air drying can be used for drying. The number of cycles of the present invention can be 1-3 times, for example, it can be 1 time, it can also be 2 times, and it can also be 3 times. The steaming and drying cycle pretreatment of the present invention is an important process for the processing of polygonatum sibiricum slices, which has the effect of cooking polygonatum sibiricum and improving the taste. The Polygonatum crispy slices that have not undergone the steaming and drying cycle feel irritating after eating. This is related to the fact that the Polygonatum mucus contains calcium oxalate needles. The calcium oxalate needles irritate the mouth when eaten, causing a numb taste in the tongue and affecting the quality of the Polygonatum slices. The steaming and drying cycle can effectively remove the calcium oxalate needles and avoid the formation of an irritating taste.

[0025] In the present invention, the above-mentioned pretreatment method can be used to prepare polygonatum products, and the products include food, medicine or health care products. As a specific embodiment, the polygonatum products include: polygonatum slices, common but not limited to, polygonatum Chinese medicine tablets, polygonatum tablet tea or instant polygonatum crispy slices.

[0026] As a specific embodiment, after the polygonatum is pretreated by the above-mentioned pretreatment method, it is first placed in a refrigerator for pre-freezing, and then the pre-frozen polygonatum is placed in a machine for freeze-drying. The pre-freezing temperature of the present invention can be -85 to -75°C, for example, -80°C; the pre-freezing time can be 20 to 30 hours, for example, 24 hours. The freeze-drying temperature of the present invention can be -60 to -50°C, for example, -54°C; the freeze-drying time can be 40 to 50 hours, for example, 45 hours; the pressure during the freeze-drying process can be maintained at 0.100±0.005mbar. The water content of the polygonatum crisp slices of the present invention can be 6% to 7%, and the polygonatum has moderate crispness at this moisture content and is easy to store.

[0027] The invention provides polygonatum crisp slices prepared by the preparation method, which are rich in nutrition, have a good taste, are easy to chew, do not stick to teeth, and are non-irritating.

[0028] In order to further illustrate the present invention, a polygonatum crisp slice and a preparation method thereof provided by the present invention are described in detail below in conjunction with embodiments, but they should not be construed as limiting the scope of protection of the present invention.

[0029] The examples of the present invention and the comparative examples are samples from the same batch to avoid the influence caused by sample differences.

[0030] Example 1

[0031] (1) Cleaning: Select fresh rhizomes of Polygonatum sibiricum from Jiuhua Mountain for cleaning, and remove the roots and mud on the surface of Polygonatum sibiricum.

[0032] (2) Slicing: Slice the cleaned Polygonatum rhizome into slices with a thickness of 3 mm.

[0033] (3) Steaming: Steam the sliced ​​Polygonatum sibiricum slices for 4 h at a temperature of 100° C. and a relative humidity of 85%.

[0034] (4) Hot air drying: The steamed Polygonatum sibiricum slices are dried with hot air at a temperature of 40° C. for 2 h and a relative humidity of 10%.

[0035] (5) Repeat the steaming and hot air drying cycle: Repeat the steaming and hot air drying cycle three times in the order and requirements of (3) and (4).

[0036] (6) Freeze drying: The slices of Polygonatum sibiricum after the last steaming were directly freeze dried. The freeze drying conditions were as follows: pre-freeze in a -80°C refrigerator for 24 hours, transfer the pre-frozen samples to a freeze dryer for the main drying process, and set the cold trap temperature of the freeze dryer to -54°C. During the drying process, the pressure was maintained at 0.100±0.005 mbar, and the drying time was 45 hours, until the moisture content of the slices of Polygonatum sibiricum reached 6%.

[0037] Example 2

[0038] The process is carried out in the manner of Example 1, except that the repeated steaming and hot air drying cycle in step (5) is replaced by 2 times.

[0039] Example 3

[0040] The process is carried out in the manner of Example 1, except that the steaming time in step (3) is replaced with 2 h and the temperature is replaced with 100° C.

[0041] Example 4

[0042] The process is carried out in the manner of Example 1, except that the hot air drying time in step (4) is replaced with 2 h and the temperature is replaced with 50° C.

[0043] Comparative Example 1: Hot air drying instead of freeze drying

[0044] The process was carried out in the manner of Example 1, except that the freeze drying in step (6) was replaced by hot air drying at a temperature of 50° C. for 12 h.

[0045] Comparative Example 2 did not perform steaming and drying cycles

[0046] The method of Example 1 is followed, except that steps (3) to (5) are omitted, that is, the steaming and drying cycle is omitted, and the polygonatum sibiricum sliced ​​in step (2) is directly freeze-dried in step (6).

[0047] Comparative Example 3: Adjusting the steaming and drying sequence

[0048] The method of Example 1 is followed, except that the order of steps (3) and (4) is exchanged, that is, the steaming and drying cycle sequence is adjusted to first perform hot air drying and then steaming.

[0049] Comparative Example 4: Increase the number of steaming and drying cycles

[0050] The process is carried out in the same manner as in Example 1, except that the number of steaming and drying cycles in step (5) is replaced with 4 times.

[0051] Test Example 1

[0052] The determination method involved in the present invention is as follows:

[0053] 1. Polysaccharide content determination method

[0054] Extraction method: accurately weigh 0.5g sample powder and place it in a 100mL conical flask, use 30mL deionized water to extract at 80℃ while stirring for 1h, then centrifuge at 5000r / min for 15min, extract three times with the above method, combine the extracts, and place them in an evaporating dish for evaporation and concentration. After the extract is concentrated, add three times the volume of anhydrous ethanol to precipitate overnight, then centrifuge at 5000r / min for 15min, collect the polysaccharide precipitate, evaporate the ethanol, and make up to 100mL to obtain the sample polysaccharide extract.

[0055] Determination method: Phenol-sulfuric acid method is used. Dry the glucose standard at 105°C to constant weight, then weigh 0.10g and dilute to 100mL to obtain a 1.00mg / mL glucose standard solution. Pipette 0mL, 0.1mL, 0.2mL, 0.3mL, 0.4mL, and 0.5mL of the standard solution into a 10mL colorimetric tube, add water to 1mL, and slowly add 1mL of 5% phenol solution (fresh) and 5mL of concentrated sulfuric acid in turn, shake well, let stand for 5min, heat in a 30°C water bath for 15min, and then measure the absorbance at 490nm. With mass concentration (mg / mL) as the horizontal coordinate and absorbance as the vertical coordinate, the standard curve is calculated as y=13.091x+0.032, R 2 =0.999. Take 0.1mL of sample extract in a colorimetric tube, add water to 1mL, and determine the sample absorbance value according to the above method.

[0056] The sample polysaccharide content is calculated by: w1 (mg / g) = [(A1-0.032) × D1)] / [(13.091 × m × (1-W)]

[0057] Among them, A1 is the absorbance value of the sample reaction solution;

[0058] D1 is the dilution multiple of the extract, D1 = 100 × 10 = 1000;

[0059] m is the sample mass, m = 0.5 g;

[0060] W is the moisture content, W=6%.

[0061] 2. Flavonoid content determination method

[0062] Extraction method: Accurately weigh 0.5g of sample powder and place it in a 100mL beaker, and use 30mL of 70% ethanol solution to extract for 40min at 30℃ while stirring. After three extractions using the above method, the extracts are combined, then centrifuged at 5000r / min for 15min, and the supernatant is evaporated to dryness using a rotary evaporator at 55℃. Finally, the extract is fixed to 10mL with 70% ethanol solution to obtain the sample flavonoid extract.

[0063] Determination method: Accurately weigh 10 mg of rutin standard, dissolve it in ethanol and make up to 10 mL to obtain a rutin standard solution with a concentration of 1 mg / mL. Accurately pipette 0.1 mL, 0.2 mL, 0.3 mL, 0.4 mL, and 0.5 mL of rutin standard solution into a 10 mL stoppered test tube, add ethanol to 1 mL, mix with 0.5 mL of 5% NaNO2 solution and react for 5 minutes, then add 0.3 mL of 10% Al(NO3)3 solution to react for 6 minutes, and finally add 2.5 mL of 4% NaOH solution and make up to 10 mL with distilled water. After reacting for 12 minutes in the dark at room temperature, measure its absorbance at a wavelength of 510 nm. With mass concentration (mg / mL) as the horizontal coordinate and absorbance as the vertical coordinate, the standard curve is calculated as y=1.356x-0.061, R 2 =0.999. Take 1 mL of sample extract and measure the sample absorbance according to the above method. Take mass concentration (mg / mL) as the horizontal axis and absorbance as the vertical axis. The standard curve is calculated as y=1.356x-0.061, R 2 =0.999.

[0064] The formula for the sample flavonoid content is: w2 (mg / g) = [(A2 + 0.061) × D2)] / [(1.356 × m) × (1-W)], where A2 is the absorbance of the sample reaction solution;

[0065] D2 is the dilution multiple of the extract, D2 = 10;

[0066] m is the sample mass, m = 0.5 g;

[0067] W is the moisture content of the sample, W=6%.

[0068] 3. Saponin content determination method

[0069] Extraction method: Accurately weigh 0.5g of sample powder and place it in a 100mL beaker, and use 30mL of 90% ethanol solution to extract at 80°C while stirring for 40min. After three extractions using the above method, the extracts are combined, and then centrifuged at 5000r / min for 15min, and the supernatant is evaporated to dryness using a rotary evaporator at 55°C, and finally the extract is fixed to 10mL with 70% ethanol solution to obtain the total saponin extract of Polygonatum cyrtonema.

[0070] Determination method: Accurately weigh 10 mg of diosgenin standard, dissolve it in ethanol and make up to 10 mL to obtain a diosgenin standard solution with a concentration of 1 mg / mL. Accurately pipette 0.1 mL, 0.2 mL, 0.3 mL, 0.4 mL, and 0.5 mL of diosgenin standard solution into a 10 mL stoppered test tube, evaporate the ethanol, add 0.2 mL of 5% vanillin-glacial acetic acid solution (fresh), add 0.8 mL of perchloric acid solution during ice bath, shake well, place in a 60°C water bath for 15 min, ice bath for 2 min, add 5 mL of glacial acetic acid, shake well, let stand for 5 min, and then measure the absorbance at 550 nm. With mass concentration (mg / mL) as the horizontal coordinate and absorbance as the vertical coordinate, the standard curve is calculated as y=1.582x+0.247, R 2 =0.999. Take 1 mL of sample extract and measure the sample absorbance value according to the above method.

[0071] The formula for the saponin content of the sample is: w3 (mg / g) = [(A3-0.247) × D2)] / [(1.582 × m) × (1-W)], where A3 is the absorbance of the sample reaction solution;

[0072] D3 is the dilution factor of the extract, D2 = 10;

[0073] m is the sample mass, m = 0.5 g;

[0074] W is the moisture content of the sample, W=6%.

[0075] 4. Determination of free phenol content

[0076] Extraction method: The specific operation is the same as the flavonoid extraction method.

[0077] Determination method: Using the Folin phenol method, weigh 10 mg of gallic acid standard, add a small amount of water to dissolve, transfer to a 100 mL volumetric flask, dilute and shake to obtain a 0.1 mg / mL gallic acid standard solution. Accurately pipette 0.1, 0.2, 0.3, 0.4, and 0.5 mL of the standard solution into a 10 mL colorimetric tube, add distilled water to 1.0 mL, add 0.5 mL of Folin phenol reagent, mix well, then add 1.5 mL of 7.5% Na2CO3 solution, and place the colorimetric tube in a 70°C water bath and heat for 30 minutes. After cooling, dilute the solution to 10 mL with deionized water, and measure its absorbance at 760 nm. Use concentration (mg / mL) as the horizontal coordinate and absorbance as the vertical coordinate to establish a standard curve y=11.770x+0.047, R 2 =0.999. At the same time, take 0.5mL of sample extract and measure the absorbance value according to the above operation.

[0078] The formula for the free phenol content of the sample is: w4 (mg / g) = [(A4-0.047) × D4)] / [(11.770 × m) × (1-W)], where A4 is the absorbance of the sample reaction solution;

[0079] D4 is the dilution multiple of the extract, D4 = 10 × 2 = 20;

[0080] m is the sample mass, m = 0.5 g;

[0081] W is the moisture content of the sample, W=6%.

[0082] 5. Texture hardness determination

[0083] The hardness of dried Polygonatum sibiricum slices was measured using a TA-XT2i texture analyzer. The slices were punctured using a P-2N probe, and the instrument simultaneously recorded and analyzed the mechanical data during the puncture process to obtain the hardness value of the sample. The specific test parameters are as follows: the speed before, during, and after the test is 2 mm / s, the trigger force is 10 g, and the puncture depth is 5 mm.

[0084] 6. Sensory evaluation method (see Table 1 for details)

[0085] Table 1 Sensory evaluation table

[0086]

[0087]

[0088] The slices of Polygonatum sibiricum prepared by the methods described in Examples 1 to 4 and Comparative Examples 1 to 4 (see Figure 1 and 2 ) were used to measure the content of polysaccharides, flavonoids, saponins, polyphenols and other nutrients, texture hardness, and sensory evaluation. The specific results are shown in Table 2. All tests were repeated at least three times independently, and the content of active substances was calculated on a dry basis.

[0089] Table 2 Results of determination of nutrient content, texture hardness and sensory evaluation of Polygonatum sibiricum slices

[0090]

[0091] From the data in Table 2, it can be seen that the instant polygonatum crisps of Example 1 have a polysaccharide content of 74.312 mg / g, a flavonoid content of 7.467 mg / g, a saponin content of 3.025 mg / g, and a free phenol content of 2.526 mg / g; the hardness is the lowest and the sensory score is the highest. Compared with Comparative Example 1, more polygonatum polysaccharides are retained, while the hardness is greatly reduced and the sensory score is higher. This may be because during the freeze-drying process, the material is pre-frozen below the eutectic point, and the water in the material is removed by solid ice sublimation in a vacuum environment, which retains the polygonatum slice polysaccharide to a greater extent, so that the polygonatum crisps maintain a good appearance and crisp taste.

[0092] The instant polygonatum crispy slices of Example 2 have a higher polysaccharide content, but the content of nutrients such as flavonoids, saponins, free phenols and the sensory scores are not as good as those of Example 1, indicating that the number of steaming combined with hot air drying cycles plays an important role in the enrichment of nutrients in polygonatum slices, and the number of hot air drying cycles will affect the quality of polygonatum slices to a certain extent.

[0093] The instant polygonatum crisp slices of Example 3 have an increased polysaccharide content, but the content and sensory scores of nutrients such as flavonoids, saponins, and free phenols are low, and the hardness is high. This may be because the steaming process has a certain effect on the enrichment of nutrients such as flavonoids, saponins, and free phenols, and the reduction of the texture and hardness of the slices. Prolonging the steaming time appropriately can achieve better results, so a processing method with a steaming time of 4 hours is adopted.

[0094] The content of nutrients such as flavonoids, saponins, and free phenols in the instant polygonatum crisp slices of Example 4 was improved, but the polysaccharide content was lost, the hardness was large, and the sensory score was low. This may be because the hot air drying process affected the polysaccharide retention of the polygonatum slices. Figure 1 It can be seen that since the hot air drying time is longer than that in Example 1, the degradation of the polygonatum sibiricum slices is more serious, which is not conducive to improving the taste. Therefore, a shorter hot air drying time of 1.5h is adopted.

[0095] The instant sliced ​​Polygonatum sibiricum of Comparative Example 1 has a high content of nutrients such as flavonoids, saponins, and free phenols, but at the same time, the loss of polysaccharides is high, the hardness increases significantly, and the sensory evaluation score is low. This may be because hot air drying relies on conduction and convection processes to transfer heat energy from the heat source to the material, and too high a drying temperature is not conducive to the retention of polysaccharides. Figure 2 It can be seen that the Maillard reaction occurred during the hot air drying process, which made the slices brown more obviously. However, it was also easy to cause the slices to shrink and deform seriously, harden the texture, and deteriorate the color, which affected the sensory score of the slices. Therefore, freeze drying technology was used directly after the last steaming process to remove a large amount of water.

[0096] The polysaccharide content of the instant polygonatum crisp slices of comparative example 2 is increased, but the content of nutrients such as flavonoids, saponins, and free phenols is low, and the sensory score is low. This may be because the steaming and drying cycle is an important process for processing polygonatum slices, which has the effect of cooked polygonatum and improving the taste. The polygonatum crisp slices that have not been steamed and dried have a sense of irritation after entering the mouth, which is related to the fact that the polygonatum mucus contains calcium oxalate needle crystals. The calcium oxalate needle crystals stimulate the oral cavity when eaten, causing a numb tongue taste and affecting the quality of the polygonatum slices. Therefore, the steaming and drying cycle can effectively remove the calcium oxalate needle crystals and avoid the formation of an irritating taste.

[0097] The instant polygonatum crisps of comparative example 3 have lower nutrient content, higher hardness and lower sensory score than those of example 1. This may be because the processing order of steaming and hot air drying has a significant effect on polygonatum slices, so steaming first and then hot air drying is more helpful to improve the quality of polygonatum crisps.

[0098] The instant polygonatum crisps of comparative example 4 have high hardness, low sensory score, and poor retention of polysaccharide components. This indicates that too many cycles of steaming combined with hot air drying cause great damage to the polygonatum slices, which is not conducive to the retention of nutrients and improvement of taste of instant polygonatum crisps, so the number of cycles is 3.

[0099] It can be seen that the method provided by the present invention has a significant effect on improving the taste of the instant polygonatum crispy slices and improving the poor taste phenomenon occurring during the drying process; at the same time, the nutritional components of the instant polygonatum crispy slices are retained.

[0100] Although the above embodiment describes the present invention in detail, it is only a part of the embodiments of the present invention, not all of the embodiments. People can also obtain other embodiments based on this embodiment without creativity, and these embodiments all fall within the protection scope of the present invention.

Claims

1. A method for pretreating Polygonatum sibiricum, characterized in that: The following steps are involved: The polygonatum sibiricum is pretreated by steaming and drying cycles; the steaming time is 2 to 4 hours, the steaming temperature is 90 to 110° C.; the drying temperature is 40 to 50° C., and the drying time is 1.5 to 2 hours.

2. The pretreatment method according to claim 1, characterized in that The number of cycles is 1 to 3 times.

3. The pretreatment method according to claim 1, characterized in that: The relative humidity of the steaming is 80% to 90%.

4. Use of the pretreatment method according to any one of claims 1 to 3 in the preparation of polygonatum products.

5. The use according to claim 4, characterized in that: The polygonatum product includes: polygonatum tablets.

6. A method for preparing polygonatum crisp slices, characterized in that: The following steps are involved: The polygonatum sibiricum is pretreated by the pretreatment method described in any one of claims 1 to 3, and then freeze-dried to obtain polygonatum sibiricum crisp slices.

7. The preparation method according to claim 6, characterized in that: The water content of the polygonatum crisp slices is 6% to 7%.

8. The preparation method according to claim 6, characterized in that: The freeze drying temperature is -60 to -50°C, and the freeze drying time is 40 to 50 hours.

9. The preparation method according to claim 6, characterized in that: The freeze drying process also includes pre-freezing; the pre-freezing temperature is -85 to -75°C, and the pre-freezing time is 20 to 30 hours.

10. Polygonatum sibiricum crispy slices prepared by the preparation method according to any one of claims 6 to 9.

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