Low-GI bread and preparation method thereof

Abstract

The invention belongs to the technical field of food, and particularly relates to low-GI bread and a preparation method thereof, and the low-GI bread is prepared from the following raw materials: high gluten wheat flour, rhizoma polygonati powder, black tea water, stevioside, salt, yeast, vital gluten, milk powder, a modifier for improving bread elasticity, and butter. The mass of the rhizoma polygonati powder is 4-10% of the mass of the wheat flour; the high-gluten wheat flour is used as a main raw material, the rhizoma polygonati flour is used as a main raw material, the high-gluten wheat flour is used as a main raw material, the rhizoma polygonati flour is used as a main raw material, the black tea water, the stevioside, the salt, the yeast, the vital gluten, the milk powder and the modifier for improving the elasticity of the bread account for 50%-55% of the total mass of the high-gluten wheat flour and the rhizoma polygonati flour, the salt is 1%-1.5% of the total mass of the black tea water, the stevioside, the yeast, the milk powder, the vital gluten, the modifier for improving the elasticity of the bread, and the butter accounts for 6%-8% of the total mass of the high-gluten wheat flour and the rhizoma polygonati flour. And the bioactive substances in the Keemun black tea are combined to synergistically reduce the glycemic index of the bread.

Description

Technical Field

[0001] The invention belongs to the technical field of food, and in particular relates to a low GI bread and a preparation method thereof. Background Art

[0002] Bread, as a convenient food, is deeply loved by consumers. Ordinary white bread has a high glycemic index (GI). Long-term consumption of ordinary white bread will lead to increased blood sugar levels, especially for people with diabetes, which is not good for health. Currently, low-GI bread uses whole grains such as barley, whole wheat, buckwheat, and potatoes as raw materials to reduce the glycemic index. However, different whole grains will affect the sensory quality of the product due to their large addition amount. Therefore, it is necessary to provide a bread with low GI and good sensory quality. Summary of the invention

[0003] In order to solve the above problems, the present invention provides a low GI bread and a preparation method thereof.

[0004] A low GI bread, the low GI bread is made from the following raw materials: high-gluten wheat flour, polygonatum powder, black tea, stevia, salt, yeast, milk powder, glutinous rice flour, a improver for improving bread elasticity, and butter; Among them, the mass of Polygonatum odoratum powder is 4%~10% of the mass of wheat flour; The percentages of black tea water, stevia, salt, yeast, milk powder, glutinous rice flour, improver for improving bread elasticity, and butter in the total mass of high-gluten wheat flour and polygonatum powder are: black tea water 50%~55%, stevia 0.02%~0.05%, salt 1%~1.5%, yeast 1%~2%, milk powder 3%~5%, glutinous rice flour 1%~3%, improver for improving bread elasticity 0.1%~0.5%, and butter 6%~8%.

[0005] Preferably, the improver for improving bread elasticity is any one of sodium stearoyl lactylate, calcium propionate and glucose oxidase.

[0006] Preferably, the method comprises the following steps: Preparation of polygonatum sibiricum powder: dry, crush and sieve the polygonatum sibiricum that has been steamed and dried nine times; Preparation of black tea water: grind black tea, sieve, add water and mix, heat, extract, filter and cool to obtain black tea water; Preparation of dough: weigh high-gluten wheat flour, add polygonatum powder and auxiliary materials, mix well, add black tea water, mix well, add butter, and take out the dough after mixing well; wherein the auxiliary materials are stevia, salt, yeast, milk powder, glutinous rice flour, and improver for improving bread elasticity; The low GI bread is obtained by fermentation and baking.

[0007] Preferably, the mass ratio of black tea to water is 1:5-15, the extraction temperature is 80°C-100°C, and the extraction time is 30min-60min.

[0008] Preferably, the black tea is Keemun black tea.

[0009] Preferably, in the preparation of the dough, the mixing method is stirring; Add polygonatum powder and auxiliary materials and stir at low speed; After adding the black tea, stir at a low speed for 3-5 minutes, then stir at a high speed for 10-12 minutes until the dough can be torn into a film. After adding the butter, stir at a low speed for 2-3 minutes until the butter and dough are evenly mixed, then stir at a high speed for 3-5 minutes until the edge of the film torn from the dough is smooth; The low-speed stirring rate is 40 rpm to 60 rpm, and the high-speed stirring rate is 100 rpm to 150 rpm.

[0010] Preferably, the fermentation specifically comprises: cutting and shaping after the first fermentation, and then performing the second fermentation; The temperature of the first fermentation is 35°C to 38°C, the relative humidity is 75% to 80%, and the fermentation time is 80min to 100min; The temperature of the second fermentation is 35° C. to 38° C., the relative humidity is 80% to 85%, and the fermentation time is 30 min to 45 min.

[0011] Preferably, the upper heating temperature of the baking is 160°C to 170°C, the lower heating temperature is 170°C to 180°C, and the baking time is 20min to 25min.

[0012] Preferably, when preparing the polygonatum sibiricum powder, it is sieved through a 60-80 mesh sieve.

[0013] Compared with the prior art, the present invention has the following beneficial effects: The invention uses high-gluten wheat flour, 4%-10% polygonatum powder, 50%-55% black tea water, 0.02%-0.05% stevioside, 1%-1.5% salt, 1%-2% yeast, 3%-5% milk powder, 1%-3% glutinous rice flour, 0.1%-0.5% improver for improving bread elasticity, and 6%-8% butter as raw materials. The prepared bread has low GI and ensures the sensory quality of the bread. The bioactive components in polygonatum are used to inhibit starch degradation, thereby increasing the content of resistant starch. The bioactive substances such as tea polyphenols in black tea inhibit the activities of alpha-amylase and glucosidase. And it can form a complex with amylose to hinder starch degradation. After polygonatum increases the content of resistant starch, the resistant starch slowly releases glucose in the stomach and small intestine, and the starch in the stomach and small intestine will not be quickly decomposed into glucose, which will cause the starch to stay in the digestive system for a longer time, thereby slowing down its digestion and absorption rate. At the same time, black tea hinders starch degradation and promotes the slowing down of starch digestion and absorption process, slowing down the rising rate of blood sugar, thereby reducing the glycemic index. When the amount of polygonatum powder and black tea water exceeds or is lower than the amount of the present invention, the sensory quality is significantly reduced.

[0014] The low GI bread of the present invention has been verified through experiments. By adding polygonatum powder at 4% to 10% of the mass of wheat flour to replace part of the wheat flour, and cooperating with black tea water, low GI bread can be produced. The bread has a delicate texture, a unique flavor of polygonatum, a long shelf life, and excellent sensory quality. DETAILED DESCRIPTION

[0015] The specific embodiments of the present invention are described in detail below, but it should be understood that the protection scope of the present invention is not limited by the specific embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work belong to the protection scope of the present invention. The experimental methods described in the embodiments of the present invention are conventional methods unless otherwise specified.

[0016] The high-gluten wheat flour and butter used in the present invention are from Yihai Kerry Cereals and Oils Industry Company, Jiuhua Polygonatum: Qingyang County Jiuhua Chinese Medicinal Materials Technology Co., Ltd., Keemun Black Tea: Anhui Keemun Black Tea Industry Group Co., Ltd., Stevia: Hebei Yulongxiang Biotechnology Co., Ltd., Refined Salt: Anhui Salt Industry Group Co., Ltd., Yeast: Angel Yeast Co., Ltd., Milk Powder: Yili Dairy Group Co., Ltd., Guyuan Powder: Fengqiu County Huafeng Powder Co., Ltd., Sodium Stearoyl Lactylate, Calcium Propionate, Glucose Oxidase: Shanghai McLean Biochemical Technology Co., Ltd.

[0017] Example 1 This embodiment provides a method for preparing low GI bread, comprising the following steps: S1. Preparation of polygonatum sibiricum powder: cut the nine-steamed and nine-dried Jiuhua polygonatum sibiricum into small pieces of 0.5 cm in size, dry them in a drying oven at 60° C. to constant weight, then grind them and pass them through an 80-mesh sieve.

[0018] S2. Preparation of black tea water: grind the Keemun black tea through a 60-mesh sieve, mix it with water at a solid-liquid ratio of 1:5, and soak it at 90° C. for 45 minutes. Then, filter and cool it to obtain black tea water for later use.

[0019] S3, preparation of dough: weigh 192g of high-gluten wheat flour, add 8g of Polygonatum sibiricum powder, accounting for 4% of Polygonatum sibiricum powder, then add stevia, salt, yeast, milk powder, glutinous rice flour, sodium stearoyl lactylate, stir at 50 rpm until the raw materials and auxiliary materials are evenly mixed, add the black tea water in step S2, first stir at 50 rpm for 5min, then stir at 150 rpm for 10min, stir until the dough can be torn into a film, then add butter, and continue stirring (first at 50 rpm The mixture was stirred at 150 rpm for 2 min until the butter and the dough were evenly mixed, and then stirred at 150 rpm for 5 min until the edge of the film torn from the dough was smooth, and then the dough was taken out; wherein, the percentages of black tea water, stevioside, salt, yeast, milk powder, glutinous rice flour, sodium stearoyl lactylate, and butter in the total mass of high-gluten wheat flour and polygonatum powder were: black tea water 55%, stevioside 0.03%, salt 1%, yeast 1.2%, milk powder 5%, glutinous rice flour 3%, sodium stearoyl lactylate 0.3%, and butter 6%, respectively.

[0020] S4, fermentation: After the first fermentation, cut and shape, and then ferment for the second time. The first fermentation is specifically: put the prepared dough into a proofing box for fermentation at a temperature of 36°C, a relative humidity of 75%, and a time of 90 minutes. The second fermentation: exhaust, divide, and round the dough from the first fermentation, and then put it into a proofing box for fermentation at a temperature of 36°C, a relative humidity of 80%, and a time of 30 minutes.

[0021] S5, baking: putting the dough in step S4 into an oven for baking, with the upper temperature being 160° C., the lower temperature being 170° C., and the baking time being 25 min.

[0022] S6, cooling and packaging the bread in step S5 to obtain a finished product.

[0023] Example 2 This embodiment provides a method for preparing low GI bread, comprising the following steps: S1. Preparation of polygonatum sibiricum powder: cut the nine-steamed and nine-dried Jiuhua polygonatum sibiricum into small pieces of 0.5 cm in size, dry them in a drying oven at 60° C. to constant weight, then grind them and pass them through an 80-mesh sieve.

[0024] S2. Preparation of black tea water: grind the Keemun black tea through a 60-mesh sieve, mix it with water at a solid-liquid ratio of 1:10, set the temperature to 100° C., soak for 30 minutes, filter, cool and obtain the black tea water for later use.

[0025] S3, preparation of dough: weigh 188g of high-gluten wheat flour, add 12g of polygonatum powder, accounting for 6% of polygonatum powder, then add stevioside, salt, yeast, milk powder, glutinous rice flour, and calcium propionate, stir at 50 rpm until the raw and auxiliary materials are evenly mixed, add the black tea water in step S2, first stir at 50 rpm for 5min, then stir at 150 rpm for 10min, stir until the dough can be torn into a film, then add butter, continue stirring (first stir at 50 rpm for 2min until the butter and dough are evenly mixed, then stir at 150 rpm for 5min) until the edge of the film torn from the dough is smooth, then take out the dough; wherein, the percentages of black tea water, stevioside, salt, yeast, milk powder, glutinous rice flour, calcium propionate, and butter in the total mass of high-gluten wheat flour and polygonatum powder are: black tea water 50%, stevioside 0.02%, salt 1.2%, yeast 1%, milk powder 3%, glutinous rice flour 1%, calcium propionate 0.1%, and butter 7%, respectively.

[0026] S4, fermentation: After the first fermentation, cut and shape, and then ferment for the second time. The first fermentation is specifically: put the prepared dough into a proofing box for fermentation at a temperature of 36°C, a relative humidity of 75%, and a time of 90 minutes. The second fermentation: exhaust, divide, and round the dough from the first fermentation, and then put it into a proofing box for fermentation at a temperature of 36°C, a relative humidity of 80%, and a time of 30 minutes.

[0027] S5, baking: putting the dough in step S4 into an oven for baking, with the upper temperature being 160° C., the lower temperature being 170° C., and the baking time being 25 min.

[0028] S6, cooling and packaging the bread in step S5 to obtain a finished product.

[0029] Example 3 This embodiment provides a method for preparing low GI bread, comprising the following steps: S1. Preparation of polygonatum sibiricum powder: cut the nine-steamed and nine-dried Jiuhua polygonatum sibiricum into small pieces of 0.5 cm in size, dry them in a drying oven at 60° C. to constant weight, then grind them and pass them through an 80-mesh sieve.

[0030] S2. Preparation of black tea water: grind the Keemun black tea through a 60-mesh sieve, mix it with water at a solid-liquid ratio of 1:15, and soak it at 95° C. for 60 minutes. Then, filter and cool it to obtain black tea water for later use.

[0031] S3, preparation of dough: weigh 184g of high-gluten wheat flour, add 16g of polygonatum powder, the proportion of polygonatum powder is 8%, then add stevia, salt, yeast, milk powder, glutinous rice flour, glucose oxidase, stir at 50 rpm until the raw materials and auxiliary materials are evenly mixed, add the black tea water in step S2, first stir at 50 rpm for 5min, then stir at 150 rpm for 10min, stir until the dough can be torn into a film, then add butter, continue stirring (first stir at 50 rpm for 2min until the butter and dough are evenly mixed, then stir at 150 rpm for 5min) until the edge of the film torn from the dough is smooth, then take out the dough; wherein, the percentages of black tea water, stevia, salt, yeast, milk powder, glutinous rice flour, glucose oxidase, and butter in the total mass of high-gluten wheat flour and polygonatum powder are: black tea water 53%, stevia 0.05%, salt 1.5%, yeast 2%, milk powder 5%, glutinous rice flour 2%, glucose oxidase 0.5%, and butter 8%, respectively.

[0032] S4, fermentation: After the first fermentation, cut and shape, and then ferment for the second time. The first fermentation is specifically: put the prepared dough into a proofing box for fermentation at a temperature of 36°C, a relative humidity of 75%, and a time of 90 minutes. The second fermentation: exhaust, divide, and round the dough from the first fermentation, and then put it into a proofing box for fermentation at a temperature of 36°C, a relative humidity of 80%, and a time of 30 minutes.

[0033] S5, baking: putting the dough in step S4 into an oven for baking, with the upper temperature being 160° C., the lower temperature being 170° C., and the baking time being 25 min.

[0034] S6, cooling and packaging the bread in step S5 to obtain a finished product.

[0035] Example 4 This embodiment provides a method for preparing low GI bread, comprising the following steps: S1. Preparation of polygonatum sibiricum powder: cut the nine-steamed and nine-dried Jiuhua polygonatum sibiricum into small pieces of 0.5 cm in size, dry them in a drying oven at 60° C. to constant weight, then grind them and pass them through a 60-mesh sieve.

[0036] S2. Preparation of black tea water: grind the Keemun black tea through a 60-mesh sieve, mix it with water at a solid-liquid ratio of 1:15, and soak it at 95° C. for 60 minutes. Then, filter and cool it to obtain black tea water for later use.

[0037] S3, dough preparation: weigh 180g high-gluten wheat flour, add 20g Polygonatum sibiricum powder, the proportion of Polygonatum sibiricum powder is 10%, then add stevia, salt, yeast, milk powder, glutinous rice flour, sodium stearoyl lactylate, stir at 50 rpm until the raw materials and auxiliary materials are evenly mixed, add the black tea water in step S2, first stir at 50 rpm for 5min, then stir at 150 rpm for 10min, stir until the dough can be torn into a film, then add butter, and continue stirring (first at 50 rpm The mixture was stirred at 150 rpm for 2 min until the butter and the dough were evenly mixed, and then stirred at 150 rpm for 5 min until the edge of the film torn from the dough was smooth, and then the dough was taken out; wherein, the percentages of black tea water, stevioside, salt, yeast, milk powder, glutinous rice flour, sodium stearoyl lactylate, and butter in the total mass of high-gluten wheat flour and polygonatum powder were: black tea water 55%, stevioside 0.03%, salt 1%, yeast 1.5%, milk powder 5%, glutinous rice flour 3%, sodium stearoyl lactylate 0.3%, and butter 6%, respectively.

[0038] S4, fermentation: After the first fermentation, cut and shape, and then ferment for the second time. The first fermentation is specifically: put the prepared dough into a proofing box for fermentation at a temperature of 36°C, a relative humidity of 75%, and a time of 90 minutes. The second fermentation: exhaust, divide, and round the dough from the first fermentation, and then put it into a proofing box for fermentation at a temperature of 36°C, a relative humidity of 80%, and a time of 30 minutes.

[0039] S5, baking: putting the dough in step S4 into an oven for baking, with the upper temperature being 160° C., the lower temperature being 170° C., and the baking time being 25 min.

[0040] S6, cooling and packaging the bread in step S5 to obtain a finished product.

[0041] Comparative Example 1 This comparative example provides a method for preparing low GI bread, which differs from Example 1 in that no polygonatum powder is added and no black tea water is used. The specific preparation steps are as follows:

[0042] S1. Preparation of dough: Weigh 200 g of high-gluten wheat flour, add stevia, salt, yeast, milk powder, glutinous rice flour, sodium stearoyl lactylate, stir at 50 rpm until the raw materials and auxiliary materials are evenly mixed, add tap water, stir at 50 rpm for 5 min, then stir at 150 rpm for 10 min, stir until the dough can be torn into a film, then add butter, continue stirring (first stir at 50 rpm for 2 min until the butter and dough are evenly mixed, then stir at 150 rpm for 5 min) until the edge of the film torn from the dough is smooth, then take out the dough; wherein, the mass percentages of tap water, stevia, salt, yeast, milk powder, glutinous rice flour, sodium stearoyl lactylate, and butter in the high-gluten wheat flour are: tap water 55%, stevia 0.03%, salt 1%, yeast 1.2%, milk powder 5%, glutinous rice flour 3%, sodium stearoyl lactylate 0.3%, and butter 6%, respectively.

[0043] S2, fermentation: After the first fermentation, cut and shape, and then ferment for the second time. The first fermentation is specifically: put the prepared dough into a proofing box for fermentation at a temperature of 36°C, a relative humidity of 75%, and a time of 90 minutes. The second fermentation: exhaust, divide, and round the dough from the first fermentation, and then put it into a proofing box for fermentation at a temperature of 36°C, a relative humidity of 80%, and a time of 30 minutes.

[0044] S3, baking: putting the dough in step S2 into an oven for baking, with the upper temperature of 160° C. and the lower temperature of 170° C. for 25 min.

[0045] S4, cooling and packaging the bread in step S3 to obtain a finished product.

[0046] Comparative Example 2 This comparative example provides a method for preparing low GI bread, which differs from Example 4 only in that black tea water is not used. The specific preparation steps are as follows:

[0047] S1. Preparation of polygonatum sibiricum powder: cut the nine-steamed and nine-dried Jiuhua polygonatum sibiricum into small pieces of 0.5 cm in size, dry them in a drying oven at 60° C. to constant weight, then grind them and pass them through an 80-mesh sieve.

[0048] S2. Preparation of dough: Weigh 180g high-gluten wheat flour and 20g Polygonatum sibiricum powder (10%), then add stevia, salt, yeast, milk powder, glutinous rice flour, and sodium stearoyl lactylate, stir at 50 rpm until the raw materials and auxiliary materials are evenly mixed, add tap water, stir at 50 rpm for 5 min, then stir at 150 rpm for 10 min, stir until the dough can be torn into a film, then add butter and continue stirring (stir at 50 rpm for 10 min). 2min until the butter and dough are evenly mixed, then stir at 150 rpm for 5min) until the edge of the film torn from the dough is smooth and then the dough is taken out; wherein, the percentages of tap water, stevioside, salt, yeast, milk powder, glutinous rice flour, sodium stearoyl lactylate, and butter in the total mass of high-gluten wheat flour and polygonatum powder are: tap water 55%, stevioside 0.03%, salt 1%, yeast 1.5%, milk powder 5%, glutinous rice flour 3%, sodium stearoyl lactylate 0.3%, and butter 6%.

[0049] S3, fermentation: After the first fermentation, cut and shape, and then ferment for the second time. The first fermentation is specifically: put the prepared dough into a proofing box for fermentation at a temperature of 36°C, a relative humidity of 75%, and a time of 90 minutes. The second fermentation: exhaust, divide, and round the dough from the first fermentation, and then put it into a proofing box for fermentation at a temperature of 36°C, a relative humidity of 80%, and a time of 30 minutes.

[0050] S4, baking: putting the dough in step S3 into an oven for baking, with the upper temperature being 160° C., the lower temperature being 170° C., and the baking time being 25 min.

[0051] S5, cooling and packaging the bread in step S4 to obtain a finished product.

[0052] Comparative Example 3 This comparative example provides a method for preparing low GI bread, wherein no polygonatum powder is added and only black tea water is added. The specific preparation steps are as follows:

[0053] S1. Preparation of black tea water: grind Keemun black tea through a 60-mesh sieve, mix with water at a solid-liquid ratio of 1:10, soak at 100° C. for 60 minutes, filter, cool and obtain black tea water for later use.

[0054] S2, preparation of dough: weigh 200g of high-gluten wheat flour, add stevioside, salt, yeast, milk powder, glutinous rice flour, sodium stearoyl lactylate, stir at 50 rpm until the raw and auxiliary materials are evenly mixed, add the black tea water in step S1, first stir at 50 rpm for 5min, then stir at 150 rpm for 10min, stir until the dough can be torn into a film, then add butter, continue stirring (first stir at 50 rpm for 2min until the butter and dough are evenly mixed, then stir at 150 rpm for 5min) until the edge of the film torn from the dough is smooth, then take out the dough; wherein the percentages of black tea water, stevioside, salt, yeast, milk powder, glutinous rice flour, sodium stearoyl lactylate, and butter in the mass of high-gluten wheat flour are: black tea water 55%, stevioside 0.03%, salt 1%, yeast 1.2%, milk powder 5%, glutinous rice flour 3%, sodium stearoyl lactylate 0.3%, and butter 6%, respectively.

[0055] S3, fermentation: After the first fermentation, cut and shape, and then ferment for the second time. The first fermentation is specifically: put the prepared dough into a proofing box for fermentation at a temperature of 36°C, a relative humidity of 75%, and a time of 90 minutes. The second fermentation: exhaust, divide, and round the dough from the first fermentation, and then put it into a proofing box for fermentation at a temperature of 36°C, a relative humidity of 80%, and a time of 30 minutes.

[0056] S4, baking: putting the dough in step S3 into an oven for baking, with the upper temperature being 160° C., the lower temperature being 170° C., and the baking time being 25 min.

[0057] S5, cooling and packaging the bread in step S4 to obtain a finished product.

[0058] Comparative Example 4 This comparative example provides a method for preparing low GI bread, wherein the amount of Polygonatum odoratum powder in the preparation method is 2%. The specific preparation steps are as follows:

[0059] S1. Preparation of polygonatum sibiricum powder: cut the nine-steamed and nine-dried Jiuhua polygonatum sibiricum into small pieces of 0.5 cm in size, dry them in a drying oven at 60° C. to constant weight, then grind them and pass them through an 80-mesh sieve.

[0060] S2. Preparation of black tea water: grind the Keemun black tea through a 60-mesh sieve, mix it with water at a mass ratio of 1:5, and soak it at 80° C. for 60 minutes. Then, filter and cool it to obtain the black tea water for later use.

[0061] S3, preparation of dough: weigh 196g of high-gluten wheat flour, add 4g of polygonatum powder, that is, the polygonatum powder accounts for 2%, then add stevioside, salt, yeast, milk powder, glutinous rice flour, glucose oxidase, stir at 50 rpm until the raw and auxiliary materials are evenly mixed, add the black tea water in step S2, first stir at 50 rpm for 5min, then stir at 150 rpm for 10min, stir until the dough can be torn into a film, then add butter, continue stirring (first stir at 50 rpm for 2min until the butter and dough are evenly mixed, then stir at 150 rpm for 5min) until the edge of the film torn from the dough is smooth, then take out the dough; wherein, the percentages of black tea water, stevioside, salt, yeast, milk powder, glutinous rice flour, glucose oxidase, and butter in the total mass of high-gluten wheat flour and polygonatum powder are: black tea water 55%, stevioside 0.03%, salt 1%, yeast 1.2%, milk powder 5%, glutinous rice flour 3%, glucose oxidase 0.3%, and butter 6%.

[0062] S4, fermentation: After the first fermentation, cut and shape, and then ferment for the second time. The first fermentation is specifically: put the prepared dough into a proofing box for fermentation at a temperature of 36°C, a relative humidity of 75%, and a time of 90 minutes. The second fermentation: exhaust, divide, and round the dough from the first fermentation, and then put it into a proofing box for fermentation at a temperature of 36°C, a relative humidity of 80%, and a time of 30 minutes.

[0063] S5, baking: putting the dough in step S4 into an oven for baking, with the upper temperature being 160° C., the lower temperature being 170° C., and the baking time being 25 min.

[0064] S6, cooling and packaging the bread in step S5 to obtain a finished product.

[0065] Comparative Example 5 This comparative example provides a method for preparing low GI bread, wherein the proportion of polygonatum odoratum powder in the preparation method is 12%. The specific preparation steps are as follows:

[0066] S1. Preparation of polygonatum sibiricum powder: cut the nine-steamed and nine-dried Jiuhua polygonatum sibiricum into small pieces of 0.5 cm in size, dry them in a drying oven at 60° C. to constant weight, then grind them and pass them through an 80-mesh sieve.

[0067] S2. Preparation of black tea water: grind the Keemun black tea through a 60-mesh sieve, mix it with water at a solid-liquid ratio of 1:10, and soak it at 95° C. for 60 minutes. Then, filter and cool it to obtain black tea water for later use.

[0068] S3, preparation of dough: weigh 176g of high-gluten wheat flour and 24g of polygonatum powder, with the polygonatum powder accounting for 12%, then add stevia, salt, yeast, milk powder, glutinous rice flour, and calcium propionate, stir at 50 rpm until the raw and auxiliary materials are evenly mixed, add the black tea water in step S2, first stir at 50 rpm for 5min, then stir at 150 rpm for 10min, stir until the dough can be torn into a film, then add butter, continue stirring (first stir at 50 rpm for 2min until the butter and dough are evenly mixed, then stir at 150 rpm for 5min) until the edge of the film torn from the dough is smooth, then take out the dough; wherein, the percentages of black tea water, stevia, salt, yeast, milk powder, glutinous rice flour, calcium propionate, and butter in the total mass of high-gluten wheat flour and polygonatum powder are: black tea water 55%, stevia 0.03%, salt 1%, yeast 1.2%, milk powder 5%, glutinous rice flour 3%, calcium propionate 0.3%, and butter 6%, respectively.

[0069] S4, fermentation: After the first fermentation, cut and shape, and then ferment for the second time. The first fermentation is specifically: put the prepared dough into a proofing box for fermentation at a temperature of 36°C, a relative humidity of 75%, and a time of 90 minutes. The second fermentation: exhaust, divide, and round the dough from the first fermentation, and then put it into a proofing box for fermentation at a temperature of 36°C, a relative humidity of 80%, and a time of 30 minutes.

[0070] S5, baking: putting the dough in step S4 into an oven for baking, with the upper temperature being 160° C., the lower temperature being 170° C., and the baking time being 25 min.

[0071] S6, cooling and packaging the bread in step S5 to obtain a finished product.

[0072] Effect verification 1. Determination of starch content in samples ①. Determination of glucose standard curve: Pipette 0.2, 0.4, 0.6, 0.8, and 1 mL of glucose standard solution into test tubes respectively, make up to 1 mL with distilled water, add 2 mL of DNS respectively, boil in boiling water bath for 2 min, cool to room temperature, add 12 mL of distilled water and mix well, measure the absorbance at 540 nm, and determine the standard curve.

[0073] ②. Determination of free glucose content in samples: Accurately weigh 1g of sample into a 50mL Erlenmeyer flask, add 20mL of distilled water, put it into a rotor for 10min, centrifuge and take the supernatant, and use the DNS method to measure the free glucose content in the sample.

[0074] ③. Starch digestion characteristics: Accurately weigh 1g sample and add 10mL distilled water. After mixing, boil in a water bath for 30min, put in a 37℃ water bath, add 10mL pepsin solution, shake in a water bath for 30min, add sodium acetate buffer (pH=5.2) and 5mL mixed enzyme (amylase, pancreatin), take the supernatant at 20min and 120min respectively, mix 1mL supernatant with 4mL ethanol, inactivate the enzyme in a boiling water bath, and measure the glucose content by the DNS method.

[0075] RDS% = (T 20 -FSG)×0.9 / M SDS% = (T 120 -T 20 )×0.9 / M RS%=(M-(RDS+SDS)) / M Among them, RDS: rapidly digestible starch, SDS: slowly digestible starch, RS: resistant starch, T 20 : Glucose production at 20 min, T 120 : Glucose production at 120 min, FSG: free glucose content in the sample, M: total starch content.

[0076] 2. Determination of GI value of bread by in vitro digestion test ① Take 1g of fresh sample freeze-dried powder, put it in a 100mL conical flask, add 15mL of simulated oral fluid (mainly containing α-amylase) preheated at 37℃, oscillate for 2min, then add a certain amount of 5mol / L HCl solution to adjust the pH to 1.5 to terminate the reaction. Take 5mL of mixed digestive fluid and add simulated gastric fluid (containing pepsin) to start gastric digestion, oscillate at 37℃ for 2h, add a certain amount of 1mol / L NaOH solution to adjust the pH to 6.9 to terminate the reaction. Finally, add simulated intestinal fluid (containing α-amylase and pancreatin) to start intestinal digestion, add distilled water to 50mL, oscillate at 37℃, and react for 3h. Take 1mL of sample at 0, 5, 10, 20, 30, 60, 90, 120, 150, and 180min respectively and put it into 4mL of 95% ethanol solution (preheated to 60℃), inactivate the enzyme in a boiling water bath, cool naturally, centrifuge at 4000r / min for 10min, and take the supernatant to determine the content of reducing sugar using the DNS reduction method.

[0077] ②Take 1 mL of the supernatant of the sample, add 2 mL of DNS, boil in a boiling water bath for 2 min, cool to room temperature, add 12 mL of distilled water and mix well, measure the absorbance at 540 nm, and calculate the amount of reducing sugar according to the standard curve.

[0078] ③ Starch hydrolysis index HI = sample digestion curve area within 3 hours / starch digestion curve area within 3 hours * 100.

[0079] ④GI=8.20+0.86HI.

[0080] The GI value and starch composition of bread are shown in Table 1.

[0081] 3. Sensory quality evaluation of bread The sensory quality of the bread prepared in Examples 1 to 4 and Comparative Examples 1 to 5 was evaluated, with bread specific volume, elasticity and hardness as evaluation indicators. Bread specific volume is the ratio of bread volume to its mass, and bread volume is measured by rapeseed substitution method; 3 slices of 30 mm thick bread were cut from each bread as test samples, and bread hardness and elasticity were tested. The final result was the average of the three samples. The test instrument was CT3 10K texture analyzer, and the results are shown in Table 2.

[0082] Table 1 GI value and starch composition Table 2 Bread sensory quality determination Comparative Example 1 is a bread obtained without adding polygonatum powder and without using black tea water. Examples 1 to 4 are based on this and optimize the process and parameters of adding polygonatum powder and adding black tea water to achieve the purpose of lowering the glycemic index. The specific results are as follows: It can be seen from Examples 1 to 4 and Comparative Examples 4 to 5 that with the increase in the amount of Huangjing powder added, the GI value of bread gradually decreases. When the amount of Huangjing powder added is 2%, the GI value of bread is greater than 55, and when the amount of Huangjing powder added is 4%, the GI value of the bakery is less than 55; when the amount of Huangjing powder added reaches 12%, the GI value does not decrease significantly. From the sensory quality of bread, it can be seen that with the increase in the amount of Huangjing powder added, the specific volume and elasticity of the bread are reduced, while the hardness increases, and the sensory quality of the bread decreases. Therefore, it is more appropriate to add 4% to 10% of Huangjing powder, so that low GI bread can be obtained and good sensory quality can be maintained.

[0083] From Comparative Examples 1 and 2, it can be seen that the addition of Polygonatum sibiricum powder alone increased the resistant starch by 51.3%, reduced the slowly digestible starch by 13.7%, and reduced the GI value from 87.5 to 58.2. From Comparative Examples 1 and 3, it can be seen that the use of black tea water instead of tap water alone increased the resistant starch by 21.6%, reduced the slowly digestible starch by 8.2%, and reduced the GI value from 87.5 to 78.6. Comparative Examples 1, 2, and 3 show that Polygonatum sibiricum powder plays a major role in inhibiting starch digestion and reducing the GI value, and black tea water plays a minor role.

[0084] It can be seen from Example 4 and Comparative Example 1 that adding Polygonatum sibiricum powder and replacing tap water with black tea water has a synergistic effect, which increases the resistant starch content by 58.5%, reduces the slowly digestible starch by 9.0%, and reduces the GI value from 87.5 to 50.5.

[0085] It should be noted that when the claims of the present invention involve numerical ranges, it should be understood that the two endpoints of each numerical range and any numerical value between the two endpoints can be selected. In order to avoid redundancy, the present invention describes a preferred embodiment.

[0086] Although the preferred embodiments of the present invention have been described, those skilled in the art may make other changes and modifications to these embodiments once they have learned the basic creative concept. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications that fall within the scope of the present invention.

[0087] Obviously, those skilled in the art can make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to include these modifications and variations.

Claims

1. A low GI bread, characterized in that: The low GI bread is made of the following raw materials: high-gluten wheat flour, polygonatum powder, black tea, stevia, salt, yeast, milk powder, glutinous rice flour, a improver for improving bread elasticity, and butter; Among them, the mass of Polygonatum odoratum powder is 4%~10% of the mass of wheat flour; The percentages of black tea water, stevia, salt, yeast, milk powder, glutinous rice flour, improver for improving bread elasticity, and butter in the total mass of high-gluten wheat flour and polygonatum powder are: black tea water 50%~55%, stevia 0.02%~0.05%, salt 1%~1.5%, yeast 1%~2%, milk powder 3%~5%, glutinous rice flour 1%~3%, improver for improving bread elasticity 0.1%~0.5%, and butter 6%~8%.

2. The low GI bread according to claim 1, characterized in that The improver for improving bread elasticity is any one of sodium stearoyl lactylate, calcium propionate and glucose oxidase.

3. A method for preparing low GI bread according to claim 1, characterized in that: The following steps are involved: Preparation of polygonatum sibiricum powder: dry, crush and sieve the polygonatum sibiricum that has been steamed and dried nine times; Preparation of black tea water: grind black tea, sieve, add water and mix, heat, extract, filter and cool to obtain black tea water; Preparation of dough: weigh high-gluten wheat flour, add polygonatum powder and auxiliary materials, mix well, add black tea water, mix well, add butter, and take out the dough after mixing well; wherein the auxiliary materials are stevia, salt, yeast, milk powder, glutinous rice flour, and improver for improving bread elasticity; The low GI bread is obtained by fermentation and baking.

4. The method for preparing low GI bread according to claim 3, characterized in that: The mass ratio of black tea to water is 1:5-15, the extraction temperature is 80°C-100°C, and the extraction time is 30min-60min.

5. The method for preparing low GI bread according to claim 3, characterized in that: The black tea is Keemun black tea.

6. The method for preparing low GI bread according to claim 3, characterized in that: In the preparation of dough, the method of mixing is stirring; Add polygonatum powder and auxiliary materials and stir at low speed; After adding the black tea, stir at a low speed for 3-5 minutes, then stir at a high speed for 10-12 minutes until the dough can be torn into a film. After adding the butter, stir at a low speed for 2-3 minutes until the butter and dough are evenly mixed, then stir at a high speed for 3-5 minutes until the edge of the film torn from the dough is smooth; The low-speed stirring rate is 40 rpm to 60 rpm, and the high-speed stirring rate is 100 rpm to 150 rpm.

7. The method for preparing low GI bread according to claim 3, characterized in that: The fermentation specifically comprises: cutting and shaping after the first fermentation, and then performing the second fermentation; The temperature of the first fermentation is 35°C to 38°C, the relative humidity is 75% to 80%, and the fermentation time is 80min to 100min; The temperature of the second fermentation is 35° C. to 38° C., the relative humidity is 80% to 85%, and the fermentation time is 30 min to 45 min.

8. The method for preparing low GI bread according to claim 3, characterized in that: The upper heating temperature of the baking is 160° C. to 170° C., the lower heating temperature is 170° C. to 180° C., and the baking time is 20 min to 25 min.

9. The method for preparing low GI bread according to claim 3, characterized in that: When preparing Polygonatum sibiricum powder, pass it through a 60-mesh sieve to an 80-mesh sieve.

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