CN112385804A

CN112385804A - Low-glycemic-index pumpkin powder and preparation method and application thereof

Info

Publication number: CN112385804A
Application number: CN202011283993.XA
Authority: CN
Inventors: 李德远; 李玟君; 李玮; 苏喜生; 李宗哲; 姜敬维; 魏海
Original assignee: Hubei University of Technology; Hubei College of Chinese Medicine
Current assignee: Hubei University of Technology; Hubei College of Chinese Medicine
Priority date: 2020-11-17
Filing date: 2020-11-17
Publication date: 2021-02-23
Anticipated expiration: 2040-11-17
Also published as: CN112385804B

Abstract

The invention relates to the technical field of food processing, and discloses low-glycemic-index pumpkin powder as well as a preparation method and application thereof. The method comprises the following steps: (1) cleaning pumpkin, peeling, cutting, removing pulp and seeds, cutting, and mashing tissue to obtain pumpkin slurry; (2) carrying out high-voltage pulse electric field treatment on the pumpkin slurry; (3) sequentially freezing and unfreezing the product obtained in the step (2); (4) repeating the step (2) and the step (3), and performing secondary high-voltage pulse electric field-freeze thawing treatment; (5) vacuum drying, and pulverizing to obtain fructus Cucurbitae Moschatae powder. The method prepares fructus Cucurbitae Moschatae powder by pure physical method, and combines high-voltage pulse electric field as a short-time continuous physical modification technology with freeze thawing treatment, so that the obtained fructus Cucurbitae Moschatae powder has low glycemic index, can be used in low glycemic index food for diabetes patients, and is helpful for improving symptoms of diabetes patients.

Description

Low-glycemic-index pumpkin powder and preparation method and application thereof

Technical Field

The invention relates to the technical field of food processing, in particular to low-glycemic-index pumpkin powder and a preparation method and application thereof.

Background

With the aging of population and the change of life style in China, the incidence rate of diabetes is remarkably improved, from 0.67% in 1980 to 10.4% in 2013, and the data report that the incidence rate of diabetes reaches 11.6% in China, and diabetes is a chronic non-infectious disease which is continuous with cardiovascular and cerebrovascular diseases and threatens human health after tumors. The reasonable diet is an important measure for preventing and assisting the drug treatment of diabetes, and the adjustment of the intake energy, the dietary structure and the meal proportion has better effect on controlling blood sugar, and is also an important measure for the medical nutrition treatment of diabetes. Food with low blood sugar reaction while ensuring energy supply is a food material which should be considered preferentially when a diabetic patient eats. The influence of food on blood sugar is related not only to the content of saccharides but also to the origin, type, physical properties, chemical structure, processing manner, storage conditions, etc. of saccharides. The pumpkin belongs to the cucurbitaceae trailing herbaceous plant, is rich in various nutrient substances such as starch, active polysaccharide and cellulose, has good dietary therapy health care effects, is a good auxiliary food for middle-aged and elderly people, and the pumpkin has the most attention to the prevention effect on diabetes. Research in the Tan Guijun shows that the pumpkin has the effect of preventing and treating diabetes mellitus, wherein the active polysaccharide has a good regulating effect on the diabetes mellitus, but the research shows that the active polysaccharide content of different pumpkin varieties has certain difference, the polysaccharide content of a plurality of different pumpkin varieties is measured to be 13.42mg/g to 74.11mg/g and generally about 27-50mg/g in 2015 years, Chenlongsheng, Chendeng Wen, Penli and the like, the polysaccharide content of different pumpkin varieties is measured and compared, Anhui agricultural science 2015,43(36):149 ion 150). In 2016, the moisture content of the honey pumpkin powder is detected to be 6.28%, the total dietary fiber content is detected to be 20.81%, the insoluble dietary fiber content is detected to be 0.61%, the soluble dietary fiber content is detected to be 19.05%, the crude protein content is detected to be 8.06% [ the analysis of the components of 3 pumpkin powders in Teng and an An, Jiahong water bamboo, Wang Stehang, and 3 pumpkin powders and the application research thereof in pork emulsified sausage, the food technology, 2016,41(02):147 one 152). In 2013, Zucshujing, etc. it was determined that the honey pumpkin powder has 10.8% of moisture, 11.25% of crude protein, 1.32% of fat, 6.84% of ash, 5.8% of soluble dietary fiber and 16.9% of total dietary fiber [ Zucshujing, Guanjian, Zhongming, etc. ], the pumpkin powder has influence on the quality of the nutrition-enriched fine dried noodles, the report of food science and technology, 2013,31(6):46-50,62 ]. In 2017, the dense pumpkin is peeled, de-pulped and made into powder in Zhang and the like, the powder is 100-200 meshes, the moisture content is 10%, the ash content is 5.37%, the crude fat is 3.14%, the protein is 7.2%, the reducing sugar is 0.35%, the total dietary fiber is 9.91%, the soluble dietary fiber is 6.42%, and the insoluble dietary fiber is 3.49%. (Zhang, Rojiani, Church, physicochemical properties and oxidation resistance of dense pumpkin powder with different granularities, food science, 2017,38, (21): 132-137]. In 2017, the sweet pumpkin powder polysaccharide is extracted from the Dengcui orchid by different extraction methods, the optimized extraction rate is 3.83% [ the influence of the different extraction methods on the pumpkin polysaccharide extraction rate and the antioxidant activity, food and grease, 2017,30(9):98-100 ].

Therefore, pumpkin generally has low content of polysaccharide, so that the improvement of the content of resistant starch in natural food is important, and besides the pumpkin polysaccharide, pumpkin contains starch with a certain ratio, including amylose and amylopectin. In 2003, Zhengshichao peeling fructus Cucurbitae Moschatae, extracting fructus Cucurbitae Moschatae starch by water milling precipitation, adding CaCl₂And measuring the starch content by a potentiometric titration method of a KI solution, and meanwhile, comparing and measuring corn starch and tapioca starch, wherein the total mass of the starch is 100, and the amylose content and the amylopectin content of the pumpkin starch are respectively 33.3 percent and 69.7 percent, the corn starch is respectively 28.8 percent and 71.2 percent, and the tapioca starch is respectively 18.2 percent and 81.8 percent. The ratio of amylose to amylopectin in pumpkin starch is 1:2 (Zhengshichao, Tubuwei),song-lai-qing research on pumpkin starch properties, food industry 2003,3:9-11]. In 2018, the preparation method comprises separating pumpkin starch from defatted pumpkin powder, determining the amylose content of the pumpkin powder in the pumpkin 21.64% and the amylopectin content of the pumpkin powder in the pumpkin in 50.19% by mass and the total starch content in the experiment 71.83% [ Lixiao Juan, Lizhugang, Wangqi, etc. ] by a dual wavelength method, and [ J ] and amylopectin contents in the pumpkin in the dual wavelength method]Food industry science and technology 2018,39(8):232-]. In 2013, acid hydrolysis method is adopted to determine the starch content of three varieties of pumpkin powder to be 84.89% -86.48% [ Zhouyei, Yanhui, Yangyi and the like ], and comparison research on physicochemical properties of different varieties of pumpkin starch [ J]2013,29(8):1784-]. Starch belongs to homogeneous polysaccharide, and researches show that the requirement of the body on insulin can be reduced by frequently eating food rich in amylose, which is probably one of the reasons for the blood sugar reducing effect of pumpkin. The ratio of the amylose content to the amylopectin content in the pumpkin is not only a key factor influencing the edible mouthfeel, but also one of the factors influencing the efficacy. Especially amylose therein can form Resistant Starch (Resistant Starch) to play the role of reducing blood sugar and blood fat.

Resistant starch is a special class of carbohydrates, which refers to the generic name for starch and its degradation products that are not digested and absorbed in the small intestine of healthy humans. Compared with digestible starch, the resistant starch has physiological functions of maintaining postprandial blood sugar stability, improving insulin sensitivity of organisms, preventing and treating intestinal diseases, reducing blood fat, controlling weight, promoting mineral absorption and the like. The discovery of resistant starch is considered by the food and agriculture organization and the world health organization of the united nations as an important result in the research of relationship between saccharides and health in recent years. The resistant starch can be widely applied as a novel dietary fiber, and researches show that the insulin resistance of diabetics can be effectively improved by taking high-resistance starch.

In order to make up the defect that the content of natural bioactive polysaccharide of the pumpkin powder is not high at present and improve the effects of reducing blood sugar and blood fat of the pumpkin powder, a new technical method is necessary, so that the improvement of the content of resistant starch in natural food is vital to convert amylose in the pumpkin powder into resistant starch, obtain the pumpkin powder with low Glycemic Index (GI), and further improve the health-care effect of the pumpkin powder.

At present, the method for preparing the resistant starch comprises multiple methods such as autoclaving, irradiation, microwave treatment, complex enzyme treatment and the like, in 2020, Zheng and the like use potato starch as a raw material, respectively adopt 3 methods such as autoclaving, irradiation and microwave to prepare the resistant starch, and research the influence of the resistant starch on the content and the physicochemical characteristics of the potato resistant starch, wherein the determination indexes comprise the content, the solubility, the swelling degree, the transparency and the chain conformation of the resistant starch. The results show that the content of resistant starch is significantly increased after the potato starch is subjected to autoclaving, microwave and irradiation treatment (p)<0.05), and the resistant starch prepared by irradiation treatment has the highest content. Physical and chemical characteristics of potato resistant starch prepared by different methods such as Zhengyan, Caoye and Fangzheng are studied, agricultural products are processed, 2020,14:10-12,18]. Wherein, the autoclave method comprises the following steps: taking potato starch, adding distilled water to prepare 15% (W/V) starch milk solution, mixing uniformly, and pre-gelatinizing for 15min in a boiling water bath; performing heat treatment on the gelatinized starch under the conditions of 0.1MPa and 121 ℃ for 15 min; taking out the starch after the pressure heating, cooling to room temperature, and refrigerating in a refrigerator at 4 ℃ for 24 hours; then culturing in an incubator at 30 ℃ for 24h, and repeating the cycle for 3 times; and finally, freeze-drying, crushing and sieving to obtain the potato resistant starch. The irradiation method comprises the following steps: taking potato starch, adding distilled water to prepare 15% (W/V) starch milk solution, mixing uniformly, and pre-gelatinizing in boiling water bath for 15 min; using gelatinized starch⁶⁰Co is subjected to irradiation treatment, the activity of a radioactive source is 60 ten thousand Curie, the Co is irradiated under the condition of static normal temperature, the total dose is 10kGy, and the dose rate is 5 Gy/min; taking out the irradiated starch, refrigerating in a refrigerator at 4 ℃ for 24h, then culturing in an incubator at 30 ℃ for 24h, and repeating the cycle for 3 times; and finally, freeze-drying, crushing and sieving to obtain the potato resistant starch. The microwave method comprises the following steps: taking potato starch, adding distilled water to prepare 15% (W/V) starch milk solution, mixing uniformly, and pre-gelatinizing in boiling water bath for 15 min; treating the gelatinized starch for 3min under the microwave power of 700W; taking out the starch after the microwave treatment, cooling to room temperature, refrigerating in a refrigerator at 4 ℃ for 24h, then culturing in an incubator at 30 ℃ for 24h, and repeating the cycle for 3 times; and finally, freeze-drying, crushing and sieving to obtain the potato resistant starch.

In 2019, sonjiayu adopts a pressure heating-enzymolysis method to prepare resistant tartary buckwheat and black bean resistant starch [ sonjiayu, modified tartary buckwheat and black bean resistant starch and application research thereof, university of Anhui engineering thesis, 2019], and the optimization conditions are as follows: under the modified conditions that the adding amount of pullulanase is 6.29npun/g dry starch, the autoclaving temperature is 101.16 ℃, the autoclaving time is 30min, and the enzymolysis time is 8.08h, the yield of the tartary buckwheat resistant starch is 19.36 percent; under the modified conditions that the adding amount of pullulanase is 4.10npun/g dry starch, the autoclaving temperature is 90.4 ℃, the autoclaving time is 30min, and the enzymolysis time is 7.26h, the yield of the black bean resistant starch is 12.5 percent. In 2018, the round-shaped pieces of fructus corni and the like are prepared into resistant starch by using sweet potato starch as a raw material and citric acid, propionic acid, lactic acid and hydrochloric acid as acidolysis agents respectively and by an ultrasonic-assisted acidolysis method. The preparation method comprises the steps of carrying out acidolysis on 20 mass percent starch milk by using 1 mass percent propionic acid solution, sequentially carrying out ultrasonic treatment for 15min, carrying out constant-temperature oscillation for 4h, and carrying out freeze drying to obtain the resistant starch with the content of 24.8 percent [ Yangxi, Zhaowei, Chenyouning and the like, preparing the sweet potato resistant starch by using an ultrasonic-assisted acid method and representing the structure thereof, China's food and oil institute, 2018,33(1): 107-.

The method relates to chemical reagents and enzymes, or raw materials or processes such as pressure, heat treatment and the like, and has relatively complex operation flow and high cost.

In 2018, Suiyong, Meixin, He Jianjun and the like, a Chinese patent of a method for preparing resistant starch by using a pressure and heat combined irradiation technology is applied, and the application numbers are as follows: 201811021532.8, publication No.: CN 109456414A. The method for preparing the resistant starch by using the pressure-heat combined irradiation technology comprises the following steps: step one, pre-gelatinization; step two, pressing and heating; step three, irradiation; step four, aging; and step five, drying. Zhengyan, etc. by adopting irradiation method to prepare potato resistant starch with resistant starch content of 12.36% [ Zhengyan, Caozu, Fangzheng, etc., physical and chemical characteristics of the potato resistant starch prepared by different methods are researched, agricultural product processing is 2020,14:10-12,18]. The methods need to prepare starch into 15-20% of starch milk in advance, the water consumption is large, and the subsequent process involves a large amount of dehydration and drying, so that the production efficiency is influenced; simultaneously, by irradiation or pressingThe heat-combined irradiation is used for preparing the resistant starch, does not relate to the use of chemical reagents, enzymes and the like, has relatively simple and convenient process, but adopts⁶⁰The Co radioactive source has high requirements on the conditions of safe production, belongs to resource elements strictly controlled by China, and is inconvenient to use; the pumpkin powder contains a small amount of fat, and radiation flavor is often generated by radiation with the total dose of about 10kGy, so that the subsequent utilization of the pumpkin powder is not facilitated.

Therefore, the invention provides a novel method for preparing pumpkin powder.

Disclosure of Invention

The invention aims to overcome the defects that in the prior art, the use of chemical reagents and enzymes is involved in the process of preparing pumpkin powder, so that the operation process is relatively complicated and the cost is high; the method prepares the pumpkin powder with low raw sugar index by a pure physical method, and combines a high-voltage pulse electric field as a short-time and continuous physical modification technology with freeze-thawing treatment, so that the method has the advantages of high production efficiency, low cost, wide applicability and the like, simplifies the production process, shortens the preparation period, increases the content and yield of resistant starch of the product, and has green and environment-friendly production process and less generated wastewater; the obtained fructus Cucurbitae Moschatae powder has low glycemic index, and can be used in low glycemic index food for diabetes patients to improve diabetes condition.

In order to achieve the above object, the present invention provides a method for preparing low glycemic index pumpkin powder by using a high voltage pulse electric field-freeze thawing dual cycle technology, which comprises the following steps:

(1) cleaning pumpkin, peeling, cutting, removing pulp and seeds, cutting, and mashing tissue to obtain pumpkin slurry;

(2) carrying out high-voltage pulse electric field treatment on the pumpkin slurry;

(3) sequentially freezing and unfreezing the product obtained in the step (2);

(4) repeating the step (2) and the step (3), and performing secondary high-voltage pulse electric field-freeze thawing treatment;

(5) vacuum drying, and pulverizing to obtain fructus Cucurbitae Moschatae powder.

Preferably, the tissue mashing process in step (1) comprises: adding water or not into the cut pumpkin, smashing the pumpkin by a smashing machine, and then fully smashing the pumpkin into a paste shape by a tissue smashing machine.

Preferably, the moisture content in the pumpkin slurry obtained in the step (1) is 20-30 mass%.

Preferably, the pumpkin slurry is conveyed to the high-voltage pulse electric field treatment chamber by a constant flow pump to be subjected to high-voltage pulse electric field treatment.

Preferably, the conveying speed of the constant flow pump for conveying the pumpkin slurry is 500-2000L/h.

Preferably, the conditions of the high-voltage pulse electric field treatment in the step (2) are as follows: the intensity of the pulse electric field is 10-30 kV/cm; the pulse frequency is 100-900 Hz; the pulse width is 1-10 mus; the pulse treatment time is 5-30 min.

Preferably, the conditions of the freezing treatment in the step (3) are: the freezing temperature is-10-0 ℃; the freezing time is 10-36 hours.

Preferably, the conditions of the thawing treatment in the step (3) are: the thawing temperature is 20-45 ℃; the thawing time is 9-20 hours.

In a second aspect, the invention provides a low glycemic index pumpkin powder prepared by the method, wherein the glycemic index of the low glycemic index pumpkin powder is less than or equal to 68.7.

In a third aspect, the invention provides the application of the low glycemic index pumpkin powder in improving diabetes.

The method disclosed by the invention is used for preparing the pumpkin powder by a pure physical method, and the high-voltage pulse electric field is used as a short-time continuous physical modification technology and combined with freeze-thawing treatment, so that the method is simple, high in production efficiency, low in cost and wide in applicability, and the method avoids the use of chemical reagents, enzymes and radioactive sources, is green and environment-friendly, and is safe and convenient. The obtained fructus Cucurbitae Moschatae powder has low glycemic index, can be used in low glycemic index food for diabetes patients, and is helpful for improving symptoms of diabetes patients.

Drawings

FIG. 1 is a graph showing the effect of pumpkin powder treated by different methods on blood sugar of mice obtained in test example 1.

Fig. 2 is a graph showing the effect of pumpkin powder treated by different methods on blood sugar of mice obtained in test example 2.

FIG. 3 is a graph showing the effect of pumpkin powder treated by different methods on blood sugar of mice obtained in test example 3.

Detailed Description

The following describes in detail specific embodiments of the present invention. It should be understood that the detailed description and specific examples, while indicating the present invention, are given by way of illustration and explanation only, not limitation.

The endpoints of the ranges and any values disclosed herein are not limited to the precise range or value, and such ranges or values should be understood to encompass values close to those ranges or values. For ranges of values, between the endpoints of each of the ranges and the individual points, and between the individual points may be combined with each other to give one or more new ranges of values, and these ranges of values should be considered as specifically disclosed herein.

On one hand, the invention discloses a method for preparing low-glycemic index pumpkin powder by using a high-voltage pulse electric field-freeze thawing dual-cycle technology, which is characterized by comprising the following steps:

(3) sequentially freezing and unfreezing the product obtained in the step (2);

In the method, the cut pumpkin is firstly smashed into tissues, then high-voltage pulse electric field treatment and freeze-thaw treatment are combined for use, and the finished product can be obtained after drying and crushing.

The freeze-thaw treatment refers to the steps of freezing and then thawing.

The method adopts a pure physical method for preparation, and has the advantages of simple method, high production efficiency, low cost and wide applicability; in addition, the method avoids the use of chemical reagents, enzymes and radioactive sources, and is green, environment-friendly, safe and convenient.

In the method, water can be added or a small amount of water can be added according to the actual situation in the process of mashing the tissues, so long as the pumpkin can be fully mashed.

In a preferred embodiment, the tissue mashing process in step (1) comprises: adding water or not into the cut pumpkin, smashing the pumpkin by a smashing machine, and then fully smashing the pumpkin into a paste shape by a tissue smashing machine.

In order to facilitate the subsequent operation and not influence the raw sugar index of the obtained pumpkin powder product, water or no water is added into the cut pumpkin according to actual conditions so as to adjust the water content in the pumpkin slurry.

The standard to be achieved for adjusting the water content in the pumpkin slurry is as follows: the moisture content in the pumpkin slurry obtained in the step (1) is 20-30% by mass.

In a specific embodiment, the moisture content in the pumpkin slurry obtained in step (1) may be in a range of any two of 20 mass%, 21 mass%, 22 mass%, 23 mass%, 24 mass%, 25 mass%, 26 mass%, 27 mass%, 28 mass%, 29 mass%, and 30 mass%.

In a preferred embodiment, the moisture content of the pumpkin slurry obtained in the step (1) is 22-28 mass%. In a more preferred embodiment, the moisture content of the pumpkin slurry obtained in the step (1) is 24 to 26 mass%.

In order to ensure that the subsequent stable and uniform high-voltage pulse electric field treatment can be carried out on the pumpkin slurry, in a specific embodiment, a constant flow pump can be adopted to convey the pumpkin slurry to a high-voltage pulse electric field treatment chamber for high-voltage pulse electric field treatment.

Further, the conveying speed of the constant flow pump for conveying the pumpkin slurry is 500-2000L/h.

In a specific embodiment, the conveying speed of the constant-flow pump for conveying the pumpkin slurry is in a range formed by any two of the following point values of 500L/h, 600L/h, 700L/h, 800L/h, 900L/h, 1000L/h, 1100L/h, 1200L/h, 1300L/h, 1400L/h, 1500L/h, 1600L/h, 1700L/h, 1800L/h, 1900L/h and 2000L/h.

In a preferred embodiment, the conveying speed of the constant flow pump for conveying the pumpkin slurry can be 600-1800L/h. In a more preferable embodiment, the conveying speed of the constant flow pump for conveying the pumpkin slurry can be 800-1200L/h.

In the method of the invention, the conditions of the high-voltage pulse electric field treatment in the step (2) are as follows: the intensity of the pulse electric field is 10-30 kV/cm; the pulse frequency is 100-900 Hz; the pulse width is 1-10 mus; the pulse treatment time is 5-30 min.

In a specific embodiment, the pulsed electric field intensity may be in the range of any two of these values of 10kV/cm, 12kV/cm, 14kV/cm, 16kV/cm, 18kV/cm, 20kV/cm, 22kV/cm, 24kV/cm, 26kV/cm, 28kV/cm, and 30 kV/cm.

In a preferred embodiment, the pulsed electric field strength may be in the range of 10-25 kV/cm. In a more preferred embodiment, the pulsed electric field strength may be in the range of 15-20 kV/cm.

In a specific embodiment, the pulse frequency may be in a range of any two of the values 100Hz, 200Hz, 300Hz, 400Hz, 500Hz, 600Hz, 700Hz, 800Hz, 900 Hz.

In a preferred embodiment, the pulse frequency may be 100-500 Hz.

In a specific embodiment, the pulse width may be in a range of any two of these values of 1 μ s, 2 μ s, 3 μ s, 4 μ s, 5 μ s, 6 μ s, 7 μ s, 8 μ s, 9 μ s, and 10 μ s.

In a preferred embodiment, the pulse width may be 1-8 μ s. In a preferred embodiment, the pulse width may be 4-5 μ s.

In a specific embodiment, the pulse processing time may be in a range formed by any two of the values of 5min, 8min, 10min, 12min, 15min, 18min, 20min, 23min, 25min, 27min and 30 min.

In a preferred embodiment, the pulse treatment time may be 5-15 min. In a preferred embodiment, the pulse treatment time may be 8-10 min.

In order to obtain pumpkin powder with a low glycemic index, the freezing treatment condition and the thawing treatment condition need to be reasonably controlled.

The conditions of the freezing treatment in the step (3) are as follows: the freezing temperature is-10-0 ℃; the freezing time is 10-36 hours.

In a specific embodiment, the freezing temperature may be in a range of any two of-10 ℃, -9 ℃, -8 ℃, -7 ℃, -6 ℃, -5 ℃, -4 ℃, -3 ℃, -2 ℃, -1 ℃, and 0 ℃.

In a preferred embodiment, the freezing temperature may be-10-4 ℃.

In a specific embodiment, the freezing time may be in the range of any two of 10 hours, 13 hours, 15 hours, 18 hours, 20 hours, 23 hours, 25 hours, 28 hours, 30 hours, 33 hours, and 36 hours.

In a preferred embodiment, the freezing time may be 12 to 26 hours. In a more preferred embodiment, the freezing time may be 16 to 25 hours.

The conditions of the thawing treatment in the step (3) are as follows: the thawing temperature is 20-45 ℃; the thawing time is 9-20 hours.

In a specific embodiment, the thawing temperature may be in the range of any two of 20 ℃, 23 ℃, 25 ℃, 27 ℃,30 ℃, 32 ℃, 35 ℃,38 ℃, 40 ℃, 42 ℃ and 45 ℃.

In a preferred embodiment, the thawing temperature may be 20-35 ℃.

In a specific embodiment, the thawing time may be in the range of any two of 9 hours, 10 hours, 11 hours, 12 hours, 13 hours, 14 hours, 15 hours, 16 hours, 17 hours, 18 hours, 19 hours, and 20 hours.

In a preferred embodiment, the thawing time may be 10 to 20 hours. In a more preferred embodiment, the thawing time may be 10 to 15 hours.

In a third aspect, the invention provides the application of the low glycemic index pumpkin powder in improving diabetes. The pumpkin powder obtained by the method has low glycemic index, can be used in low glycemic index foods of diabetes patients, and is beneficial to improving relevant symptoms of the diabetes patients.

The present invention will be described in detail by way of examples, but the scope of the present invention is not limited thereto.

The preparation method of the pumpkin powder contrast in the test example of the invention comprises the following steps: cleaning pumpkin, peeling, cutting, removing pulp and seeds, cutting, mashing tissue to obtain pumpkin slurry with water content of 20-30 wt%, and directly vacuum drying at 50 deg.C to obtain pumpkin powder as contrast.

Example 1

Cleaning pumpkin, peeling, cutting, removing pulp and seeds, cutting, smashing a sufficient tissue to obtain pumpkin slurry with the water content of 20-30 mass%, driving the pumpkin slurry forwards through a constant flow pump, conveying the pumpkin slurry into a high-voltage pulse electric field treatment chamber at the speed of 800L/h, simultaneously starting a power supply of 220V/50HZ, controlling the intensity of pulse electric field to be 10-30kV/cm, controlling the pulse treatment time to be 5-30min, controlling the pulse frequency to be 100 plus material of 900Hz and the pulse width to be 1-10 mu s, freezing the pumpkin at the temperature of-10-4 ℃ for 10-15 hours, unfreezing the pumpkin at the temperature of 35-45 ℃ for 15-20 hours after the high-voltage pulse treatment of the material, then repeatedly carrying out secondary high-voltage pulse electric field-freeze thawing treatment, carrying out vacuum drying at the temperature of 50 ℃, and crushing to obtain the pumpkin.

Comparative example 1

The procedure of example 1 was followed except that the high-voltage pulsed electric field treatment was repeated twice without freeze-thaw treatment.

Comparative example 2

The procedure of example 1 was followed except that the freeze-thaw treatment was repeated twice without performing the high-voltage pulsed electric field treatment.

Comparative example 3

The pumpkin powder is prepared by adopting a pressure-heat combined irradiation method (referring to Zhengyan method: Zhengyan, Cao, Fangzheng and the like, physical and chemical characteristics of potato resistant starch prepared by different methods are researched, and agricultural product processing is 2020,14:10-12, 18).

Test example 1

Determination of resistant starch: an appropriate amount of pumpkin powder sample is weighed and incubated with amylopsin and amyloglucosidase in a shaking water bath for 16h at 37 ℃. Adding equal volume of ethanol to terminate the reaction, and centrifuging to recover the resistant starch. The supernatant was centrifuged off after washing 2 times with aqueous ethanol (50% V/V). The precipitate was dissolved in a 2mol/LKOH solution and stirred vigorously in an ice-water bath by means of a magnetic stirrer. The solution was neutralized with acetate buffer and the glucose content was measured with glucose oxidase/peroxidase reagent (GOPOD), the resistant starch content was obtained by coefficient conversion, and the results are shown in Table 1 as an average of the results of three-sample measurements.

And (3) determining the glycemic index: refer to Fangchong's method [ Fangchong, the effect of different additives on glycemic index and properties of extruded reconstituted rice, Master thesis at Jiangnan university, 2018 ]. Weighing 100mg of sample, placing the sample in a 50mL centrifuge tube, adding 2mL of water, gelatinizing in a boiling water bath for 10min, adding 13mL of 0.2mol/L acetic acid-sodium acetate buffer solution with the pH value of 5.2, balancing for 10min in a constant-temperature water bath at 37 ℃, adding 0.2mL of mixed enzyme solution (porcine pancreatic alpha-amylase 290U/mL and glucoamylase 15U/mL), oscillating in the constant-temperature water bath at 37 ℃ (the rotating speed is 150r/min) and timing. Oscillating for reaction for 0min, 30min, 60min, 90min, 120min and 180min, adding 0.1mL of supernatant into 2mL of absolute ethanol for enzyme deactivation, carrying out colorimetric determination on the glucose content at 510nm by using a GOPOD glucose kit, carrying out parallel determination on each sample for 3 times, taking an average value, and drawing a starch hydrolysis curve. The ungelatinized recombinant rice hydrolysis curve was used as a control. The hydrolysis index was calculated according to the fitting equation and Origin software, and the GI value was calculated by the formula, with the results shown in table 2.

Mouse test, modeling and blood sugar measurement, refer to a Monday singing method [ Monday singing, Libaoguo, tourmaline and the like, research on the influence of tartary buckwheat resistant starch on the physiological function of diabetic mice, Chinese food and oil academy 2015, 5:24-28] Kunming mice 115, male, clean level, weight (22 +/-2) g: central for prevention and control of Hubei disease, streptozotocin/STZ (pharmaceutical grade): sigma corporation. 10 were randomly selected as normal control groups, 105 molded, of which 81 were successfully molded, and 70 were randomly selected and divided into seven groups of 10. The common feed for the mice is prepared based on the GB14924.3-2010 standard, and the mice are divided into eight groups: normal control, diabetes control, metformin drug group, 5 different pumpkin powder experimental groups, each group contains 10 pumpkin powder; wherein, the 5 different pumpkin powder experimental group feeds are common powdery feeds for mice, and are prepared by adding 15% of different pumpkin powders; the other groups were given ordinary feed. The metformin drug group was intragastrically administered at 100mg/kg metformin per day. Blood was collected from the tail tip after 12 hours of fasting, and blood glucose was measured with a glucometer, and the test results are shown in table 3 and fig. 1.

Data processing: data processing was performed with SPSS17.0 and results are shown as x + -s, with statistical differences between groups using the t-test with P < 0.05.

TABLE 1 resistant starch content of pumpkin powder (x. + -. s,%) treated by different methods

Measurement index	Comparison of pumpkin powder	Example 1	Comparative example 1	Comparative example 2	Comparative example 3
						Resistant starch	0.32±0.04	3.78±0.43b	2.13±0.12b	1.04±0.06a	3.62±0.52b

Note: a, p <0.05, b, p <0.01, compared with pumpkin powder control.

As can be seen from Table 1, the resistant starch content of the pumpkin powder treated by different methods is significantly higher than that of the pumpkin powder control (p <0.05 or p < 0.01). The content of resistant starch in the pumpkin powder treated by the high-voltage pulse electric field-freeze thawing dual-cycle method is the highest and is 3.78% of that in the pumpkin powder treated by the high-voltage pulse electric field-freeze thawing dual-cycle method, the content of the resistant starch is 11.8 times of that in the pumpkin powder treated by the high-voltage pulse electric field-freeze thawing dual-cycle method, the content of the resistant starch is not statistically different from that in the pumpkin powder treated by the high-voltage pulse electric field-freeze thawing dual-cycle method by 3.62%, and the content of the resistant starch. Therefore, the resistant starch content of the pumpkin powder obtained by the high-voltage pulse electric field-freeze thawing method is higher than that of the pumpkin powder obtained by the pressure-heat combined irradiation method, the high-voltage pulse electric field method, the freeze thawing method and the pumpkin powder contrast.

Table 2 pumpkin powder glycemic index (n ═ 10) processed by different methods

Note: a, p <0.05, compared to pumpkin powder control.

As can be seen from table 2, the glycemic indexes of the pumpkin powders processed by different methods are lower than those of the pumpkin powder control, wherein the glycemic index of the pumpkin powder processed by the high-voltage pulse electric field-freeze-thaw dual cycle method in the embodiment is 67.1% and slightly lower than 68.5% of that of the pressure and heat combined irradiation method, but there is no significant difference; compared with the pumpkin powder control blood glucose generation index of 77.4%, the pumpkin powder control blood glucose generation index and the pumpkin powder control blood glucose generation index reach a significant difference level (p is less than 0.05); the high-voltage pulse electric field-freeze thawing double-circulation method and the pressure-heat combined irradiation method are obviously lower than 73.4 percent of the high-voltage pulse electric field method and 71.3 percent of the freeze thawing method. Therefore, the index of blood glucose generation of the pumpkin powder obtained by the high-voltage pulse electric field-freeze thawing dual-cycle method is lower than that of the pumpkin powder obtained by the pressure-heat combined irradiation method, the high-voltage pulse electric field method, the freeze thawing method and the pumpkin powder contrast.

Table 3 effect of pumpkin powder treated by different methods on blood sugar of mice (mmol/L, n ═ 10)

Note: a, p <0.05, b, p <0.01, compared to diabetes control, c, p <0.05, compared to pumpkin powder control.

As can be seen from Table 3 and FIG. 1, the blood glucose level of the normal control mice was maintained at 4.9-5.0mmol/L during the test period, and after the diabetes molding was successful, the initial blood glucose level of each group reached 17.4-17.6 mmol/L. After the feed is raised for 7-28 days, the blood sugar of the normal control is unchanged, the diabetes control is slowly increased, and other groups have obvious descending tendency. Wherein, the pumpkin powder contrast is reduced from 17.1mmol/L to 14.4mmol/L, the high-voltage pulse electric field-freeze thawing dual-cycle method is reduced from 17.4mmol/L to 10.3mmol/L, the combined autoclaving and irradiation method is reduced from 17.3mmol/L to 11.6mmol/L, the high-voltage pulse electric field method is reduced from 17.6mmol/L to 13.8mmol/L, the freeze thawing method is reduced from 17.5mmol/L to 13.6mmol/L, and on day 14, compared with the diabetes contrast, the blood sugar of each treatment group is obviously reduced to reach the obvious difference level (a, p is less than 0.05, b, p is less than 0.01); by the 28 th day, compared with the pumpkin powder contrast, the high-voltage pulse electric field-freeze thawing dual-cycle method of 10.3mmol/L and the combined autoclaving and irradiation method of 11.6mmol/L in the embodiment achieve significant differences (c, p is less than 0.05); 13.8mmol/L of the high-voltage pulse electric field method and 13.6mmol/L of the freeze-thaw method are slightly lower than 14.4mmol/L of the pumpkin powder control (p is more than 0.05). Therefore, the pumpkin powder obtained by the high-voltage pulse electric field-freeze thawing dual-cycle method has the blood sugar reducing effect superior to that of the combined autoclaving and heating irradiation method, the high-voltage pulse electric field method, the freeze thawing method and the pumpkin powder contrast.

Example 2

Cleaning pumpkin, peeling, cutting, removing pulp and seeds, cutting, fully crushing tissues to obtain pumpkin slurry with the water content of 22-28 mass%, driving the pumpkin slurry forwards by a constant flow pump at the conveying speed of 600-1200L/h, entering a high-voltage pulse electric field treatment chamber, simultaneously starting a power supply of 220V/50HZ, freezing at the temperature of-4-0 ℃ for 12-16 hours, thawing at the temperature of 20-25 ℃ for 9-12 hours after high-voltage pulse treatment of materials, repeatedly performing secondary high-voltage pulse electric field-freeze thawing treatment, and performing vacuum drying at the temperature of 50 ℃ and crushing to obtain the pumpkin powder.

Comparative example 4

The procedure of example 2 was followed except that the high-voltage pulsed electric field treatment was repeated twice without freeze-thaw treatment.

Comparative example 5

The procedure of example 2 was followed except that the freeze-thaw treatment was repeated twice without performing the high-voltage pulsed electric field treatment.

Test example 2

The measurement of resistant starch, the measurement of glycemic index, the mouse test, the modeling, and the blood glucose measurement and the data processing were the same as in test example 1, and the test results are shown in tables 4 to 6 and FIG. 2.

TABLE 4 resistant starch content of pumpkin powder (x. + -. s,%) treated by different methods

Measurement index	Comparison of pumpkin powder	Example 2	Comparative example 4	Comparative example 5	Comparative example 3
						Resistant starch	0.30±0.02	3.85±0.52b	2.42±0.26b	1.11±0.04a	3.57±0.36b

Note: a, p <0.05, b, p <0.01, compared with pumpkin powder control.

As can be seen from Table 4, the resistant starch content of the pumpkin powder treated by different methods is significantly higher than that of the pumpkin powder control (p <0.05 or p < 0.01). The content of resistant starch in the pumpkin powder treated by the high-voltage pulse electric field-freeze thawing dual-cycle method is the highest, 3.85% of the content of the resistant starch in the pumpkin powder treated by the high-voltage pulse electric field-freeze thawing dual-cycle method, which is 12.8 times of the pumpkin powder as compared with the pumpkin powder, and is slightly higher than 3.57% of that of a pressure and heat combined irradiation method, but no statistical difference exists, and the content of the resistant starch in the pumpkin powder treated by the high-voltage pulse electric field-freeze thawing dual-cycle method is higher than 2.42. Therefore, the resistant starch content of the pumpkin powder obtained by the high-voltage pulse electric field-freeze thawing method is higher than that of the pumpkin powder obtained by the pressure-heat combined irradiation method, the high-voltage pulse electric field method, the freeze thawing method and the pumpkin powder contrast.

Table 5 pumpkin powder glycemic index (n ═ 10) processed by different methods

Note: a, p <0.05, compared to pumpkin powder control.

As can be seen from table 5, the glycemic index in the pumpkin powder processed by different methods is lower than that of the pumpkin powder control, wherein the glycemic index in the pumpkin powder processed by the high-voltage pulse electric field-freeze-thaw dual cycle method in the embodiment is 68.3% and slightly lower than 69.1% of that of the pressure and heat combined irradiation method, but there is no significant difference; compared with the pumpkin powder control glycemic index of 76.6%, the pumpkin powder and the pumpkin powder achieve a significant difference level (p is less than 0.05); the high-voltage pulse electric field-freeze thawing double-circulation method and the pressure-heat combined irradiation method are obviously lower than 72.9 percent of the high-voltage pulse electric field method and 71.6 percent of the freeze thawing method. Therefore, the index of blood glucose generation of the pumpkin powder obtained by the high-voltage pulse electric field-freeze thawing dual-cycle method is lower than that of the pumpkin powder obtained by the pressure-heat combined irradiation method, the high-voltage pulse electric field method, the freeze thawing method and the pumpkin powder contrast.

Table 6 effect of pumpkin powder treated by different methods on blood glucose of mice (mmol/L, n ═ 10)

As can be seen from Table 6 and FIG. 2, the blood glucose level of the normal control mice was maintained at 4.9-5.0mmol/L during the test period, and after the diabetes molding was successful, the initial blood glucose level of each group reached 17.4-17.6 mmol/L. After the feed is raised for 7-28 days, the blood sugar of the normal control is unchanged, the diabetes control is slowly increased, and other groups have obvious descending tendency. Wherein, the pumpkin powder contrast is reduced from 17.6mmol/L to 14.6mmol/L, the high-voltage pulse electric field-freeze thawing dual-cycle method is reduced from 17.4mmol/L to 9.8mmol/L, the combined autoclaving and irradiation method is reduced from 17.4mmol/L to 12.0mmol/L, the high-voltage pulse electric field method is reduced from 17.5mmol/L to 14.1mmol/L, the freeze thawing method is reduced from 17.1mmol/L to 14.3mmol/L, and on day 14, compared with the diabetes contrast, the blood sugar of each treatment group is obviously reduced to reach the obvious difference level (a, p is less than 0.05, b, p is less than 0.01); by the 28 th day, compared with the pumpkin powder contrast, the high-voltage pulse electric field-freeze thawing dual-cycle method of 9.8mmol/L and the combined autoclaving and irradiation method of 12.0mmol/L achieve significant differences (c, p is less than 0.05); 14.1mmol/L of the high-voltage pulse electric field method and 14.3mmol/L of the freeze-thaw method are slightly lower than 14.6mmol/L of the pumpkin powder control (p is more than 0.05). Therefore, the pumpkin powder obtained by the high-voltage pulse electric field-freeze thawing dual-cycle method has the blood sugar reducing effect superior to that of the combined autoclaving and heating irradiation method, the high-voltage pulse electric field method, the freeze thawing method and the pumpkin powder contrast.

Example 3

Cleaning pumpkin, peeling, cutting, removing pulp and seeds, cutting, fully crushing tissues to obtain pumpkin slurry with the water content of 20-30 mass%, driving the pumpkin slurry forwards by a constant flow pump at the conveying speed of 1800L/h, entering a high-voltage pulse electric field treatment chamber, simultaneously starting a power supply of 220V/50HZ, enabling the intensity of a pulse electric field to be 15-25kV/cm, the pulse treatment time to be 8-15min, the pulse frequency to be 200 plus materials at 500Hz and the pulse width to be 4-8 mu s, freezing the pumpkin at-10-0 ℃ for 20-26 hours after the high-voltage pulse treatment of the materials, thawing the pumpkin at 20-45 ℃ for 10-15 hours, repeating the secondary high-voltage pulse electric field-freezing and thawing treatment, drying the pumpkin at 50 ℃ in vacuum, and crushing the pumpkin to obtain the pumpkin powder.

Comparative example 6

The procedure of example 3 was followed except that the high-voltage pulsed electric field treatment was repeated twice without freeze-thaw treatment.

Comparative example 7

The procedure of example 3 was followed except that the freeze-thaw treatment was repeated twice without performing the high-voltage pulsed electric field treatment.

Test example 3

The measurement of resistant starch, the measurement of glycemic index, the mouse test, the modeling, and the blood glucose measurement and the data processing were the same as in test example 1, and the test results are shown in tables 7 to 9 and FIG. 3.

TABLE 7 resistant starch content of pumpkin powder (x. + -. s,%) treated by different methods

Measurement index	Comparison of pumpkin powder	Example 3	Comparative example 6	Comparative example 7	Comparative example 3
						Resistant starch	0.33±0.01	3.71±0.22b	2.20±0.09b	1.08±0.12a	3.56±0.45b

Note: a, p <0.05, b, p <0.01, compared with pumpkin powder control.

As can be seen from Table 7, the resistant starch content of the pumpkin powder treated by different methods is significantly higher than that of the pumpkin powder control (p <0.05 or p < 0.01). In the embodiment, the content of the resistant starch in the pumpkin powder treated by the high-voltage pulse electric field-freeze thawing dual-cycle method is the highest, namely 3.71%, which is 11.2 times of that of the pumpkin powder, and has no statistical difference with 3.56% of that of the pressure and heat combined irradiation method, and the high-voltage pulse electric field-freeze thawing method and the pressure and heat combined irradiation method are both higher than 2.20% of that of the high-voltage pulse electric field method and 1.08% of that of the freeze thawing method. Therefore, the resistant starch content of the pumpkin powder obtained by the high-voltage pulse electric field-freeze thawing method is higher than that of the pumpkin powder obtained by the pressure-heat combined irradiation method, the high-voltage pulse electric field method, the freeze thawing method and the pumpkin powder contrast.

Table 8 pumpkin powder glycemic index treated by different methods (n ═ 10)

Note: a, p <0.05, compared to pumpkin powder control.

As can be seen from table 8, the glycemic indexes of the pumpkin powders processed by different methods are lower than those of the pumpkin powder control, wherein the glycemic index of the pumpkin powder processed by the high-voltage pulse electric field-freeze-thaw dual cycle method in the embodiment is 68.7% and slightly lower than 70.2% of that of the pressure and heat combined irradiation method, but there is no significant difference; compared with the pumpkin powder control blood glucose generation index of 79.2%, the pumpkin powder control blood glucose generation index and the pumpkin powder control blood glucose generation index reach a significant difference level (p is less than 0.05); the high-voltage pulse electric field-freeze thawing double-circulation method and the pressure-heat combined irradiation method are obviously lower than 73.1 percent of the high-voltage pulse electric field method and 74.6 percent of the freeze thawing method. Therefore, the index of blood glucose generation of the pumpkin powder obtained by the high-voltage pulse electric field-freeze thawing dual-cycle method is lower than that of the pumpkin powder obtained by the pressure-heat combined irradiation method, the high-voltage pulse electric field method, the freeze thawing method and the pumpkin powder contrast.

Table 9 effect of pumpkin powder treated by different methods on blood glucose of mice (mmol/L, n ═ 10)

As can be seen from Table 9 and FIG. 3, the blood glucose level of the normal control mice was maintained at 4.9-5.1mmol/L during the test period, and after the diabetes molding was successful, the initial blood glucose level of each group reached 17.0-17.9 mmol/L. After the feed is raised for 7-28 days, the blood sugar of the normal control is unchanged, the diabetes control is slowly increased, and other groups have obvious descending tendency. Wherein, the pumpkin powder contrast is reduced from 17.6mmol/L to 15.2mmol/L, the high-voltage pulse electric field-freeze thawing dual-cycle method is reduced from 17.3mmol/L to 11.1mmol/L, the combined autoclaving and irradiation method is reduced from 17.7mmol/L to 12.2mmol/L, the high-voltage pulse electric field method is reduced from 17.9mmol/L to 14.3mmol/L, the freeze thawing method is reduced from 17.2mmol/L to 13.9mmol/L, and on day 14, compared with the diabetes contrast, the blood sugar of each treatment group is obviously reduced to reach the obvious difference level (a, p is less than 0.05, b, p is less than 0.01); by the 28 th day, compared with the pumpkin powder contrast, the high-voltage pulse electric field-freeze thawing dual-cycle method is 11.1mmol/L, and the combined autoclaving and irradiation method is 12.2mmol/L, which all reach significant differences (c, p is less than 0.05); 14.3mmol/L of the high-voltage pulse electric field method and 13.9mmol/L of the freeze-thaw method are slightly lower than 15.2mmol/L of the pumpkin powder control (p is more than 0.05). Therefore, the pumpkin powder obtained by the high-voltage pulse electric field-freeze thawing dual-cycle method has the blood sugar reducing effect superior to that of the combined autoclaving and heating irradiation method, the high-voltage pulse electric field method, the freeze thawing method and the pumpkin powder contrast.

The preferred embodiments of the present invention have been described above in detail, but the present invention is not limited thereto. Within the scope of the technical idea of the invention, many simple modifications can be made to the technical solution of the invention, including combinations of various technical features in any other suitable way, and these simple modifications and combinations should also be regarded as the disclosure of the invention, and all fall within the scope of the invention.

Claims

1. A method for preparing low-glycemic index pumpkin powder by using a high-voltage pulse electric field-freeze thawing dual-cycle technology is characterized by comprising the following steps of:

(3) sequentially freezing and unfreezing the product obtained in the step (2);

2. The method of claim 1, wherein the tissue mashing process of step (1) comprises: adding water or not into the cut pumpkin, smashing the pumpkin by a smashing machine, and then fully smashing the pumpkin into a paste shape by a tissue smashing machine.

3. The method according to claim 1 or 2, wherein the moisture content of the pumpkin slurry obtained in the step (1) is 20-30 mass%.

4. The method of claim 1, wherein the pumpkin slurry is delivered to the high-voltage pulsed electric field treatment chamber for high-voltage pulsed electric field treatment using a constant flow pump.

5. The method as claimed in claim 4, wherein the conveying speed of the pumpkin slurry conveyed by the constant flow pump is 500-2000L/h.

6. The method according to claim 1, wherein the conditions of the high-voltage pulsed electric field treatment in the step (2) are as follows: the intensity of the pulse electric field is 10-30 kV/cm; the pulse frequency is 100-900 Hz; the pulse width is 1-10 mus; the pulse treatment time is 5-30 min.

7. The method according to claim 6, wherein the conditions of the freezing treatment in the step (3) are: the freezing temperature is-10-0 ℃; the freezing time is 10-36 hours.

8. The method according to claim 6, wherein the conditions of the thawing treatment in the step (3) are: the thawing temperature is 20-45 ℃; the thawing time is 9-20 hours.

9. The low glycemic index pumpkin powder produced by the method of any one of claims 1 to 8, wherein the low glycemic index pumpkin powder has a glycemic index of 68.7 or less.

10. The use of the low glycemic index pumpkin powder of claim 9 for ameliorating diabetes.