A green preparation process for cassava sour starch with baking expansibility

Abstract

The present invention provides a green preparation process for cassava sour starch with baking expansibility, which relates to the technical field of food preparation. The process comprises the following steps: (l) preparation of native cassava starch, (2) fermentation and ultraviolet irradiation, and (3) drying. After preparing the native cassava starch, the native cassava starch is denatured by a method combining fermentation and ultraviolet irradiation. Subsequently, combined with the drying process of the present application, the finally obtained cassava sour starch has the characteristic of good baking expansibility.

Description

l A green preparation process for cassava sour starch with baking expansibility TECHNICAL FIELD The present invention relates to the eld of food preparation technology, and in particular to a green preparation process for cassava sour starch with baking expansibility. BACKGROUND Cassava (Manihot esculenta Crantz) is one of the world s three major tuber crops and one of the six major food crops. Because it is rich in starch, it is known as the underground grain and the king of starch, and it has been widely cultivated in tropical and subtropical regions of more than 100 countries in Africa, the Americas, and Asia. Cassava is a staple food for nearly one billion people worldwide. In many countries in Africa and South America, cassava is the third largest food source after rice and maize, contributing signicantly to food security and poverty alleviation. Cassava starch, like starches from wheat, potato, and maize, can provide humans with abundant carbohydrates and serves as an excellent starch-based raw material. However, due to its poor solubility, stability, and resistance to high temperature, shear, and acid-base conditions, cassava starch has low protein quality (low content and lack of structural amino acids) and contains no gluten protein. When used alone, it cannot form a gluten network structure, cannot produce dough with viscoelasticity and extensibility, has poor plasticity, and therefore has certain limitations when directly applied in food processing. Therefore, it has become necessary to develop modied starch with new functions or improved original functions in order to broaden the application range of cassava starch. SUMMARY In View of this, the purpose of the present invention is to provide a green preparation process for cassava sour starch with baking expansibility, in which the native cassava starch is physically modied by fermentation combined with ultraviolet irradiation, and combined with the drying process of the present application, the nal cassava sour starch exhibits good baking expansibility. To solve the above technical problems, the present invention adopts the following technical solution: A green preparation process for cassava sour starch with baking expansibility, comprising the following steps: (1) Preparation of native cassava starch: fresh cassava is peeled and then added to water and blended into a slurry to obtain cassava pulp; an extract solution is added to the sieved cassava pulp to obtain a composite slurry; the composite slurry is sent to a separator for separation to obtain starch milk, which is dehydrated and dried to obtain native cassava starch; (2) Fermentation: the native cassava starch obtained in step (1) is mixed with glucose powder, a fermentation inoculant, and water in a conical ask, sealed, and fermented; then the upper fermentation liquid is poured off to obtain a precipitated slurry, reserved for later use; (3) Drying: the precipitated slurry obtained in step (2) is dried to obtain cassava starch. In the present invention, further, the extract solution is a licorice extract. The licorice extract is obtained by alcohol extraction of licorice raw material. In the present invention, further, the fermentation inoculant in step (2) is lactic acid bacteria, which is a composite strain, supplied by DSM. During use, to achieve more uniform fermentation, the entire package of bacteria can be dissolved in water and then prepared as a lactic acid bacteria solution (the amount of water is adjusted as needed) before use (the calculated usage is 0.0l%0.05% of the mass of native cassava starch). In the present invention, further, in step (2), the amount of glucose powder added is 3%6% of the mass of native cassava starch, the amount of fermentation inoculant is 0.0l%0.05% of the mass of native cassava starch, and the water is distilled water, accounting for 150%300% of the mass of native cassava starch. In the present invention, further, the fermentation in step (2) is carried out in a constant temperature incubator at 3040°C for 3672 hours. In the present invention, further, before drying in step (3), the precipitated slurry is subjected to the following treatment: the precipitated slurry is irradiated under ultraviolet light at a wavelength of 254 nm for 6-12 hours, during which the slurry is stirred to ensure that the UV light reaches different parts of the slurry; after UV irradiation, the precipitated slurry is subjected to hot air drying. In the present invention, further, the hot air drying is performed by placing the precipitated slurry in a stainless steel tray and drying it in an electric hot air circulating oven at 45-65 °C for 20-30 hours until the moisture content is below 14%. The present invention also provides a cassava modied starch with baking expansibility obtained by the above green preparation process. The cassava modied starch can be used for bread preparation. In summary, due to the adoption of the above technical solutions, the benecial effects of the present invention are: The present invention proposes a green preparation process for cassava sour starch with baking expansibility, in which native cassava starch is modied by fermentation combined with ultraviolet irradiation. Enzymatic physical modication is used to treat cassava starch, which is greener and safer compared with chemical modication. Specically, during the fermentation of cassava starch in this application, different microbial populations appear, responsible for the synthesis of amylases and organic acids, resulting in the pH of the fermentation liquid decreasing to 3.2-4.2. The produced organic acids erode the surface morphology of starch granules, creating ssures or micropores on the surface; under acidic conditions, polymer chains depolymerize, forming small linear fragments of starch molecules, which is conducive to forming a uniform and continuous gel network structure during baking. Under ultraviolet irradiation, starch acidied by lactic acid bacteria is exposed to UV radiation, leading to oxidation of the starch, where hydroxyl groups (OH) on C2, C3, and C6 are oxidized to carbonyl (C=O) and carboxyl (COOH) groups. The physicochemical processing properties and multiscale structure of starch are modied, resulting in decreased starch viscosity, reduced longchain content (DP >36), decreased shortrange order, and reduced molecular weight, while DP 612 short chains increase. These structural changes alter the gelatinization behavior of starch at the supramolecular level; at the same time, starch hydration capacity decreases, making it easier to expand and gelatinize, which facilitates gas retention and moisture escape during baking, creating higher steam pressure and lower expansion resistance, thereby increasing baking expansion capacity. After treatment of native cassava starch with the extract solution followed by hot air drying, the nal product is loose, porous, and exhibits excellent baking expansibility. The entire preparation process of this application is short in duration, low in cost, environmentally friendly, and produces controllable product quality, which is favorable for industrial production. During the experimental process, it was found that the drying method has a signicant impact on bulk density, which reects the looseness of the powder. When hot air drying is used, due to prolonged temperature and air circulation, solutes inside the starch migrate to the surface with water, leading to surface crystallization and hardening; therefore, conventional hot air drying results in high bulk density. To solve this problem, licorice extract was added during the preparation of native cassava starch. The initial intention was to provide health benets to the starch, but it was surprisingly found that the addition of licorice extract can reduce the bulk density of the dried modied starch, making the nal product looser. This may be because, after fermentation by lactic acid bacteria, components in licorice, such as glycyrrhizic acid, act on the starch, reducing molecular bonding forces and hindering intermolecular binding. Combined with ultraviolet irradiation, the starch undergoes oxidation, thereby enhancing expansion performance. In addition, since UV irradiation is performed before hot air drying, the efciency of hot air drying is greatly improved, so drying can be completed in a shorter time while ensuring the bulk density of the nal starch product. DETAILED DESCRIPTION OF THE INVENTION The following examples can help those skilled in the art more comprehensively understand the present invention, but they shall not limit the present invention in any way. Example 1 This example provides a green preparation process for cassava sour starch with baking expansibility, specically including the following steps: Preparation of native cassava starch: Fresh cassava is peeled, then water is added, and the mixture is blended into a slurry to obtain cassava pulp; licorice extract is added to the ltered cassava pulp to obtain a composite slurry; the composite slurry is sent to a separator for separation, obtaining starch milk, which is then dehydrated and dried to obtain native cassava starch. Fermentation: The native cassava starch obtained in step (1) is mixed with glucose powder, lactic acid bacteria, and water in a conical ask, fully mixed, sealed, and placed in a constant temperature incubator at 30°C for fermentation for 72 h. The upper fermentation liquid is then poured off to obtain a precipitated slurry, which is reserved; the addition amount of glucose powder is 4% of the mass of native cassava starch, the addition amount of fermentation agent is 0.01% of the mass of native cassava starch, and the water is distilled water, accounting for 150% of the mass of native cassava starch. Ultraviolet irradiation: The precipitated slurry obtained in step (2) is subjected to ultraviolet irradiation, specically placing the precipitated slurry under UV light with a wavelength of 254 nm for 6 h, stirring the slurry during the process to ensure the UV light irradiates different parts of the slurry. Drying: After ultraviolet irradiation, the precipitated slurry is subjected to hot air drying to obtain cassava starch; the hot air drying is performed by placing the precipitated slurry in a stainless steel tray and drying in an electric hot air circulation oven at 45 °C for 30 h, until the moisture content is below 14%. Example 2 This example provides a green preparation process for cassava sour starch with baking expansibility, specically including the following steps: Preparation of native cassava starch: Fresh cassava is peeled, then water is added, and the mixture is blended into a slurry to obtain cassava pulp; licorice extract is added to the ltered cassava pulp to obtain a composite slurry; the composite slurry is sent to a separator for separation, obtaining starch milk, which is then dehydrated and dried to obtain native cassava starch. Fermentation: The native cassava starch obtained in step (1) is mixed with glucose powder, lactic acid bacteria, and water in a conical ask, fully mixed, sealed, and placed in a constant temperature incubator at 35 °C for fermentation for 48 h. The upper fermentation liquid is then poured off to obtain a precipitated slurry, which is reserved; the addition amount of glucose powder is 5% of the mass of native cassava starch, the addition amount of fermentation agent is 0.02% of the mass of native cassava starch, and the water is distilled water, accounting for 200% of the mass of native cassava starch. Ultraviolet irradiation: The precipitated slurry obtained in step (2) is subjected to ultraviolet irradiation, specically placing the precipitated slurry under UV light with a wavelength of 254 nm for 10 h, stirring the slurry during the process to ensure the UV light irradiates different parts of the slurry. Drying: After ultraviolet irradiation, the precipitated slurry is subjected to hot air drying to obtain cassava starch; the hot air drying is performed by placing the precipitated slurry in a stainless steel tray and drying in an electric hot air circulation oven at 55°C for 25 h, until the moisture content is below 14%. Example 3 This example provides a green preparation process for cassava sour starch with baking expansibility, specically including the following steps: Preparation of native cassava starch: Fresh cassava is peeled, then water is added, and the mixture is blended into a slurry to obtain cassava pulp; licorice extract is added to the ltered cassava pulp to obtain a composite slurry; the composite slurry is sent to a separator for separation, obtaining starch milk, which is then dehydrated and dried to obtain native cassava starch. Fermentation: The native cassava starch obtained in step (1) is mixed with glucose powder, lactic acid bacteria, and water in a conical ask, fully mixed, sealed, and placed in a constant temperature incubator at 40°C for fermentation for 36 h. The upper fermentation liquid is then poured off to obtain a precipitated slurry, which is reserved; the addition amount of glucose powder is 6% of the mass of native cassava starch, the addition amount of fermentation agent is 0.05% of the mass of native cassava starch, and the water is distilled water, accounting for 300% of the mass of native cassava starch. Ultraviolet irradiation: The precipitated slurry obtained in step (2) is subjected to ultraviolet irradiation, specically placing the precipitated slurry under UV light with a wavelength of 254 nm for 12 h, stirring the slurry during the process to ensure the UV light irradiates different parts of the slurry. Drying: After ultraviolet irradiation, the precipitated slurry is subjected to hot air drying to obtain cassava starch; the hot air drying is performed by placing the precipitated slurry in a stainless steel tray and drying in an electric hot air circulation oven at 65 °C for 20 h, until the moisture content is below 14%. Experimental Example To illustrate the practical value of the present application, the applicant conducted the following comparative experiments: Experiment 1: Comparing the bulk density of each group of cassava sour starch, with the groups as follows: Group A: cassava sour starch obtained according to the method of Example 2. Group B: cassava sour starch prepared as in Example 2, but without the addition of licorice extract. Group C: cassava sour starch prepared as in Example 2, but without the addition of licorice extract and without ultraviolet irradiation. Group D: cassava sour starch prepared as in Example 2, but without the addition of licorice extract and ultraviolet irradiation, with drying carried out by sun-drying. Group E: cassava sour starch prepared as in Example 2, with drying carried out by sun-drying. Group F: cassava sour starch prepared as in Example 2, but without the fermentation step. The bulk density of the cassava sour starch obtained from the above groups was compared. Bulk density measurement: The bulk density of the samples was measured using the graduated cylinder lling method: A 10 mL graduated cylinder was weighed and recorded as ml; the sample (cassava sour starch) was placed into the cylinder and lled to the 10 mL mark, then weighed and recorded as m2. The bulk density was calculated using the following formula: Bulk density (g / mL) = (mzm1) / 10. Record the data for each group as shown in Table 1: Table 1 Bulk density of tapioca starch __ According to the data in Table 1, the tapioca starch prepared by the method of the present application has a relatively low bulk density, indicating that the product has a loose and porous structure and good quality. Experiment 2: The tapioca starch of the present application can be used for bread preparation. In order to illustrate the effect, the applicant compared the cross-sectional pore parameters and specic volume of the bread obtained after using different cassava ours (including tapioca starch and native cassava starch) to prepare bread. That is, the following groups of cassava ours were used as raw materials for bread preparation: Group 1: tapioca starch obtained by the method of Example 2 of the present application; Group 2: the fermentation operation was removed, and the other methods were the same as the rst group; Group 3: the drying method was sun drying, and the other methods were the same as the rst group; Group 4: the ultraviolet treatment operation was removed, and the other methods were the same as the rst group; Group 5: the drying method was vacuum freeze drying, and the other methods were the same as the rst group; Group 6: native cassava starch obtained by the method of step (1) of Example 2. In this experiment, bread was prepared as follows: 5 g high-gluten our, 20 g milk, 5 g corn oil, 0.2 g salt, 6 g granulated sugar, and 12 g egg were mixed thoroughly and brought to a boil, stirring constantly to prevent burning. The mixture was reduced to a semisolid paste. Removed from heat, tapioca our was immediately added and stirred until no dry powder remained. 12 g egg was then added in small increments, stirring constantly after each addition, until the mixture formed an inverted triangle. The mixture was piped into a piping bag and squeezed into balls, which were then divided into three equal portions. The mixture was baked in an oven at 200 °C (top heat) and 160°C (bottom heat) for 15 minutes. After baking, the crosssectional pore parameters and specic volume of the bread were measured for each group. The cross-sectional pore parameters of the bread were measured by cutting the bread into uniform slices and scanning the cross section with a scanner. The measurement was repeated six times for each sample. The specic volume of bread was determined by weighing the mass (g) of the bread using a balance and measuring its volume (mL) using the rapeseed displacement method. Specic volume (mL / g) = volume (mL) / mass (g). The measurement was repeated three times for each sample. The cassava our (including tapioca starch and native cassava starch) was obtained using the same methods as listed above. Aside from the different cassava ours, the other raw materials and processes used in bread preparation were identical. This yielded multiple groups of bread, and their cross-sectional pore parameters and specic volumes were compared, as shown in Table 2: Table 2 Comparison of pore parameters and volume of bread Average pore area ( Pore density ( Bread volume ( mmz) unit / m2) mL / g) 4.60d:0.04C 35.74:l:l .40a 4.76i0.l la 9.051009b 18.61i0.82° 2.61i0.16°l 5.151007d 33.44i0.84b 4.671013a 8.01jz0.llc 23.47i0.91d 2.98:t0.l3C 5.25i0.10d 29.47i0.57c 4.17:1:0.07b 11.41j:0.l8a 15.71j:1.06f 22110.08e The results in Table 2 indicate that the tapioca starch prepared using the method of this application produces bread of good quality and uffy texture, demonstrating that the tapioca starch prepared using the method of this application exhibits baking expansibility. Although the present invention has been described in detail above using general descriptions and specic embodiments, it will be readily apparent to those skilled in the art that modications or improvements may be made based on the present invention. Therefore, such modications or improvements, without departing from the spirit of the present invention, fall within the scope of the present invention.

Claims

1. A green cassava acid starch preparation process with baking expansion, characterized because it comprises the following steps: (1) preparation of native cassava starch: fresh cassava is peeled, then water is added and the cassava is mixed into a suspension to obtain cassava pulp; extract is added to the gelled cassava pulp to obtain a compound suspension; the compound suspension is sent to a separator for separation treatment to obtain starch milk, and the starch milk is dehydrated and dried to obtain native cassava starch; (2) fermentation: the native starch obtained in step (1) cassava starch is mixed with glucose powder, fermentation agent and water in a conical flask, sealed and fermented; then the top fermentation liquid is decanted to obtain a precipitated suspension, which is saved for later use; (3) drying: the precipitated suspension obtained in step (2) is dried to obtain cassava starch.

2. Method according to claim 1, characterised in that the extract is liquorice extract.

3. Method according to claim 1, characterised in that the fermentation agent in step (2) are lactic acid bacteria.

4. Method according to claim 1, characterized in that in step (2) the added amount of glucose powder constitutes 36% of the mass of the native cassava starch, the fermentation agent 0.010.05% of the mass of the native cassava starch consists of, and the water distilled water ISO300% of the mass of the native cassava starch is included.

5. Method according to claim 1, characterised in that in step (2) the fermentation is carried out performed in a constant temperature incubator at 3040 °C for 3672 o'clock.

6. A method according to claim 1, characterised in that in step (3), before drying, the the following treatment is carried out: the precipitated suspension is exposed to ultraviolet light at a wavelength of 254 nm for 6-12 hours, and The suspension is stirred during the process to ensure that the UV light reaches different parts of the suspension; after UV irradiation the precipitated suspension dried with hot air.

7. Method according to claim 6, characterised in that the drying is carried out with hot air performed by placing the settled suspension in a stainless steel bowl and Dry these in an electric hot air oven at 45-65 °C for 20-30 hours.

8. Cassava starch with baking expansion capacity, prepared according to the method of one of conclusions 1-7.