A method for preparing low-lead tapioca flour

Abstract

The application discloses a preparation method of low-lead cassava powder and belongs to the technical field of food processing. The method comprises the following steps: (1) screening a cassava variety with low lead accumulation; (2) planting the cassava in soil to which a composite soil modifier is applied, cultivating until maturity, and harvesting tubers; (3) uniformly homogenizing the cassava tubers by mixing and crushing, adjusting the pH to 3-9, adding curcumin-chitosan adsorption material, and then treating the adsorbed homogenate with ultrasonic waves with a combination power of 5-20 w / mL to adsorb free-state metal lead, and then removing the curcumin-chitosan adsorption material by filtration, centrifugation, and drying the precipitate to obtain the low-lead cassava powder. The application realizes the reduction and control of heavy metal lead in cassava by using a cassava variety with low lead accumulation and a soil modifier, and the lead content in the cassava powder is reduced by using ultrasonic waves combined with adsorption material in the cassava processing process. The application intervenes in the whole process from planting to processing, and provides a systematic solution for the control and removal of heavy metals in cassava.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of food processing, in particular to a preparation method of low-lead cassava flour. BACKGROUND

[0002] Cassava is a widely planted crop, and its tubers are rich in starch and can be used to make cassava flour. Cassava flour is an important food raw material and can be used to make cassava noodles, cassava balls, etc. The quality of food raw materials will affect the quality of the products obtained, and food safety not only needs to effectively control the quality and quantity of active ingredients, but also should effectively control toxic and harmful ingredients in the preparation, such as heavy metals and pesticide residues.

[0003] Lead is a heavy metal element with neurotoxicity, which has different degrees of damage to many organs and tissues in the human body, especially the hematopoietic system, nervous system and kidney. Lead is widely distributed in the environment and can easily accumulate in the human body through the food chain. Lead exposure can affect multiple systems of the body, and the harm to young children and women of childbearing age is particularly serious. Lead in the body is distributed in the brain, liver, kidneys and bones, and can also be stored in teeth and bones, accumulating over time. Lead in the bones can be released into the blood during pregnancy, becoming a source of exposure for developing fetuses. Lead can also cause long-term damage to adults, including increasing the risk of high blood pressure, cardiovascular problems and kidney damage.

[0004] Cassava is a large biomass energy plant with strong stress resistance, relative tolerance to pollution and easy accumulation of heavy metals (Shen Shil, et al. Feasibility of large biomass plants for remediation of heavy metal contaminated sites [J]. Journal of Agricultural Environment Science, 2013, 32(3): 572-578.), when the planting environment is contaminated by heavy metals, it is easy to cause the accumulation of heavy metals in cassava tubers, which will inevitably affect the quality and safety of cassava flour, which is extremely disadvantageous to food production.

[0005] Therefore, how to reduce the content of lead in cassava and further reduce the content of lead in cassava flour is a problem that needs to be solved at present. SUMMARY

[0006] The purpose of the present application is to provide a low-lead cassava flour production method, which takes measures in germplasm screening, soil improvement, product processing, etc. to jointly control, effectively reduce the content of heavy metal lead, and improve the edible safety of cassava flour.

[0007] To achieve the above purpose, the technical scheme adopted by the present application is as follows:

[0008] The present application provides a preparation method of low-lead cassava flour, comprising the following steps:

[0009] (1) screening cassava varieties with low lead accumulation;

[0010] (2) planting cassava in soil applied with a composite soil conditioner, cultivating to maturity, and harvesting tubers; the composite soil conditioner comprises, by weight fraction, 15-20 parts of nitrogen-phosphorus-potassium compound fertilizer, 5-10 parts of calcium-magnesium compound, 5-10 parts of nano-silicon, and 3-5 parts of quicklime;

[0011] (3) mixing and grinding cassava tubers with water to obtain a homogenate, adjusting the pH to 3-9, adding curcumin-chitosan adsorption material, and treating the adsorption homogenate with ultrasonic treatment at a combined power of 5-20 w / mL to adsorb free metal lead, then removing the curcumin-chitosan adsorption material by filtration, centrifuging, and drying the precipitate to obtain the low-lead cassava powder.

[0012] In step (1), the cassava variety with low lead accumulation is screened from numerous cassava varieties to control the lead content from the source.

[0013] Further, the cassava variety with low lead accumulation is GR10.

[0014] In step (2), the composite soil conditioner is used to increase the pH value of the soil, reduce the effective lead content in the soil, ensure the yield of cassava, reduce the absorption of lead during the growth of cassava, and will not have other negative effects on the environment.

[0015] In the present application, the nitrogen-phosphorus-potassium compound fertilizer, calcium-magnesium compound, nano-silicon, and quicklime are used to prepare the composite soil conditioner, wherein the nitrogen-phosphorus-potassium compound fertilizer can supplement the elements required for plant growth such as nitrogen, phosphorus, and potassium; the calcium-magnesium compound has the characteristics of acid adjustment, soil improvement, and mineral element supplementation; the nano-silicon has the characteristics of soil purification, mineral element supplementation, and heavy metal ion adsorption; and the quicklime can adjust the soil acidity and provide mineral elements.

[0016] The preparation method of the composite soil conditioner comprises: first, forming the nitrogen-phosphorus-potassium compound fertilizer, calcium-magnesium compound, nano-silicon, and quicklime into granules with a diameter of 2-4 mm, mixing, adding polyvinyl alcohol and chitin as a coating, and drying and cooling.

[0017] Further, the surface of the granules is wetted with polyvinyl alcohol aqueous solution, and then chitin is added and uniformly mixed, wherein the amount of polyvinyl alcohol accounts for 10-15% of the total mass of the components of the composite soil conditioner, and the amount of chitin accounts for 20-30% of the total mass of the components of the composite soil conditioner.

[0018] Further, the application amount of the composite soil conditioner is 300-400 kg / acre. The application method is deep application into the soil to a depth of 20-30 cm.

[0019] In step (3), the homogenate of cassava is treated by ultrasonic, and the hydroxyl groups of cassava starch are protonated under low pH conditions, so that the hydrogen bonds between lead and starch are effectively destroyed, and the lead is dissolved in the form of ions. Then, the curcumin-chitosan adsorption material is used to adsorb and fix the lead ions after the lead ions are dissolved, so as to destroy the concentration balance of lead dissolution and further promote the dissolution of lead.

[0020] Further, the homogenization conditions are as follows: the mass ratio of cassava tuber to water is 1:1.5-2, the rotation speed of the homogenizer is set to 10000-12000r / min, and the homogenization time is 3-5min.

[0021] When adjusting the pH value, citric acid solution and NaOH with a concentration of 0.50mol / L-1.0mol / L are used. Further, the pH value is adjusted to 6.

[0022] The preparation method of the curcumin-chitosan adsorption material comprises the following steps: dissolving chitosan in 0.2-0.4mol / L acetic acid solution, heating and stirring to obtain a 4-8% chitosan solution, adding 6-10% curcumin to the solution, then dropping the mixed solution into 1-1.5mol / L NaOH solution, stirring and hardening to obtain the curcumin-chitosan adsorption material.

[0023] Further, the amount of curcumin-chitosan adsorption material accounts for 0.1-2% of the homogenate, and the treatment time is 0.5-2h.

[0024] Further, the amount of curcumin-chitosan adsorption material accounts for 1.5-2% of the homogenate, the ultrasonic power is 15-20w / mL, and the treatment time is 0.5h.

[0025] After the treatment is completed, the curcumin-chitosan adsorption material is removed by filtration, and then the precipitate is obtained by centrifugation. Further, the centrifugation conditions are 10000-12000g and the centrifugation time is 15-30min. Further, the precipitate is dried at 50-70℃.

[0026] The present application has the following beneficial effects:

[0027] (1) The preparation method provided by the present application realizes the reduction and control of heavy metal lead in cassava at a low cost by selecting low-lead accumulation cassava varieties and using composite soil conditioner, thereby reducing the harm of lead in cassava from the source of food processing.

[0028] (2) In the present application, the heavy metal lead in cassava tuber is extracted in the form of free state by adjusting the pH of cassava homogenate and using ultrasonic in the process of cassava processing; then, the curcumin-chitosan adsorption material is added to adsorb the free state metal lead, so as to destroy the adsorption-desorption balance of lead ions and cassava matrix, and improve the removal efficiency of lead in the process of cassava powder processing.

[0029] (3) The present application has the characteristics of green and high efficiency from planting to processing. The organic combination of variety selection, soil improvement and cassava powder processing greatly reduces the content of lead in cassava powder and its harm from the aspect of industrial chain, and further improves the application range of cassava powder. BRIEF DESCRIPTION OF DRAWINGS

[0030] Figure 1 The difference in lead enrichment coefficient of five different cassava varieties.

[0031] Figure 2 The effective state content of soil lead and pH under the treatment of composite soil conditioner.

[0032] Figure 3 The removal rate of heavy metals in cassava under different adsorption material addition conditions.

[0033] Figure 4 The removal rate of heavy metals in cassava under different ultrasonic power treatment conditions. DETAILED DESCRIPTION

[0034] In order to make the purpose, technical scheme and advantages of the embodiments of the present application clearer, the technical scheme in the embodiments of the present application will be described clearly and completely below in combination with the drawings in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present application.

[0035] The test methods used in the following examples are conventional methods unless otherwise specified; the materials, reagents, etc. used are reagents and materials available from commercial channels unless otherwise specified.

[0036] Example 1: Effect of different cassava germplasm on heavy metal lead content in cassava

[0037] 1. Variety collection: A large number of cassava varieties with excellent qualities such as high yield, low hydrocyanic acid, strong stress resistance, etc. are collected, and a total of 5 cassava varieties are collected. The specific ones are as follows:

[0038] (1) GR10 is a variety with excellent characteristics such as low hydrocyanic acid, fresh eating, high amylopectin, strong waxy, wide adaptability, strong drought resistance, etc.

[0039] (2) SC9 is a variety with excellent characteristics such as no bitterness, high starch content, low fiber content, rich protein and vitamin C content, low hydrocyanic acid content, and rich in minerals such as calcium, phosphorus and potassium.

[0040] (3) Shatin bread is a variety with excellent characteristics such as low hydrocyanic acid, high starch content, high yield and strong resistance.

[0041] (4)SC6068 is a traditional and widely planted cassava variety with excellent characteristics such as high starch content, high yield and strong resistance.

[0042] (5)GR13 is a variety with excellent characteristics such as early maturity, high yield, high starch content, low hydrocyanic acid content, and wide adaptability.

[0043] 2. Field Trial: The trial was conducted in a large field, with an area of ​​no less than 200 square meters. Each experimental plot was divided into 12 strips (each strip following the shape of the farmland and not necessarily of uniform size). Five varieties—GR10, SC9, Shatin Bread, SC6068, and GR13—were planted, with each variety replicated three times. Direct seeding was used. After the cassava matured, cassava tubers and corresponding soil samples were collected, and the Pb content of each sample was analyzed according to national standard methods.

[0044] 3. Calculate the enrichment factor of lead in cassava based on the lead content of the sample. The specific calculation formula is as follows:

[0045]

[0046] 4. Results Analysis

[0047] like Figure 1 As shown, among the five cassava varieties screened, GR10 had the lowest lead enrichment coefficient of 0.004, making it the target variety for screening. This variety was used in the following experiments.

[0048] Example 2: Effects of compound soil conditioner on heavy metal content in cassava

[0049] 1. Site selection: Select sites contaminated with lead for screening of soil conditioners, with a lead content of 350-400 mg / kg.

[0050] 2. Raw material composition of compound soil conditioner: 20kg nitrogen, phosphorus and potassium compound fertilizer, 5kg calcium and magnesium compound, 5kg nano silicon, and 3kg quicklime.

[0051] 3. Preparation method of compound soil conditioner: First, make nitrogen, phosphorus and potassium compound fertilizer, calcium and magnesium compound, nano silicon and quicklime into granules with a diameter of 2mm, then mix them evenly with a mixer, add 5kg of polyvinyl alcohol solution with a mass concentration of 20% to wet the surface of the compound soil conditioner, then add 10kg of chitin as a coating, and then dry and cool.

[0052] 4. Experimental grouping: The experimental site was divided into 6 plots, and in the experiment, it was divided into 2 treatments according to whether the composite soil conditioner was applied, and each treatment had 3 replicates. The specific grouping is as follows:

[0053] Table 1 Experimental grouping scheme

[0054]

[0055] 5. Judgment criteria: According to the proportion of available lead, the target soil conditioner concentration is screened out, and the formula is as follows:

[0056]

[0057] 5. Results analysis

[0058] As shown in Figure 2 , the application of composite soil conditioner can significantly improve the physical and chemical properties of soil, in which the pH is increased from 5.1 to 5.6, and the available lead content in soil is reduced from 14.2 ppm to 12.9 ppm. The change of soil physical and chemical properties is more helpful to the low enrichment of heavy metals in cassava.

[0059] Example 3: Effect of curcumin-chitosan adsorption material on lead content in cassava powder.

[0060] 1. Preparation of curcumin-chitosan adsorption material

[0061] Chitosan was dissolved in 0.2 mol / L acetic acid solution, and stirred at 80°C for 5h, and the bubbles were removed by ultrasonic oscillation to obtain a chitosan solution with a mass fraction of 4%. Then 8% curcumin was added to the solution. Then the mixed solution was dropped into 1 mol / L NaOH solution, and stirred for 30 min to obtain curcumin-chitosan adsorption material.

[0062] 2. Preparation of cassava powder

[0063] 100g fresh cassava was weighed, 1:1.5 water was added, and homogenized. The pH of the homogenate was adjusted to 6, and then 0, 0.5%, 1.0%, 1.5%, and 2% curcumin-chitosan adsorption material was added, respectively. The ultrasonic power was set to 15w / mL, and the ultrasonic treatment was 30 min. The curcumin-chitosan adsorption material was filtered out. Centrifugation was performed at 12000g for 10 min. The precipitate was taken and dried at 60°C for 24h to obtain cassava powder.

[0064] 3. Detection of heavy metal content

[0065] 0.2-0.5g of cassava powder was weighed, 5mL of nitric acid and 0.5mL of perchloric acid were added, and the digestion was completed. The volume was adjusted, and the content of heavy metals in cassava powder was determined by graphite furnace atomic absorption method.

[0066] 4. Results analysis

[0067] As shown in Figure 3 , with the increase of the addition amount of curcumin-chitosan adsorption material, the removal rate of lead in cassava homogenate first increased and then stabilized, and the best addition ratio was 1.5%.

[0068] Example 4: Effect of ultrasonic power on lead content in cassava powder.

[0069] In example 3, the ultrasonic power was set to 0, 5, 10, 15, and 20 w / mL, respectively, and other conditions remained unchanged.

[0070] The results are shown in Figure 4 , with the increase of the ultrasonic power, the removal rate of lead in cassava powder first increased and then stabilized, and the best ultrasonic power was 15 w / mL.

Claims

1. A method of preparing low lead tapioca flour, characterized by, The method comprises the following steps: (1) planting cassava in soil applied with a composite soil conditioner, cultivating to maturity, and harvesting tubers; the composite soil conditioner comprises, by weight fraction, 15-20 parts of nitrogen-phosphorus-potassium compound fertilizer, 5-10 parts of calcium-magnesium compound, 5-10 parts of nano silicon, and 3-5 parts of quicklime; (2) mixing and crushing the cassava tubers with water to obtain a homogenate, adjusting the pH to 6, adding curcumin-chitosan adsorption material, and treating the homogenate with ultrasonic treatment at a power of 5-20 W / mL to adsorb free-state lead, then removing the curcumin-chitosan adsorption material by filtration, centrifuging, and drying the precipitate to obtain the low-lead cassava powder; The preparation method of the curcumin-chitosan adsorption material comprises: dissolving chitosan in a 0.2-0.4 mol / L acetic acid solution, heating and stirring to obtain a 4-8% chitosan solution, adding 6-10% curcumin to the solution, then dropping the mixed solution into a 1-1.5 mol / L NaOH solution, and stirring to harden to obtain the curcumin-chitosan adsorption material.

2. The method of producing low-lead tapioca flour according to claim 1, characterized in that, The cassava variety is GR10.

3. The method of producing low-lead tapioca flour according to claim 1, wherein The preparation method of the composite soil conditioner comprises: respectively preparing nitrogen-phosphorus-potassium compound fertilizer, calcium-magnesium compound, nano silicon, and quicklime into granules with a diameter of 2-4 mm, mixing, and adding polyvinyl alcohol and chitin as a coating film, and drying and cooling.

4. The process for the preparation of low lead tapioca flour as claimed in claim 3 wherein, The adding of polyvinyl alcohol and chitin as a coating film specifically comprises: adding a polyvinyl alcohol aqueous solution to wet the surface of the granules, and then adding chitin and mixing uniformly, wherein the amount of polyvinyl alcohol accounts for 10-15% of the total mass of the components of the composite soil conditioner, and the amount of chitin accounts for 20-30% of the total mass of the components of the composite soil conditioner.

5. The process for the preparation of low lead tapioca flour as claimed in claim 1, wherein, In step (1), the application amount of the composite soil conditioner is 300-400 kg / acre, and the application method is deep application to 20-30 cm in the soil.

6. The method of producing low-lead tapioca flour according to claim 1, wherein In step (2), the mass ratio of cassava tubers to water is 1:1.5-2.

7. The process for the preparation of low lead tapioca flour as claimed in claim 1, wherein, The amount of curcumin-chitosan adsorption material accounts for 0.1-2% of the homogenate, and the treatment time is 0.5-2 h.

8. The process for the preparation of low lead tapioca flour as claimed in claim 7, wherein, The amount of curcumin-chitosan adsorption material accounts for 1.5-2% of the homogenate, the ultrasonic power is 15-20 W / mL, and the treatment time is 0.5 h.

9. The process for the preparation of low lead tapioca flour as claimed in claim 1, wherein, In step (2), the drying temperature is 50-70°C.

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