Preparation method of rice products with low content of heavy metal

Abstract

The invention discloses a preparation method of rice products with a low content of heavy metal. The method comprises the following steps of performing pulp mixing, performing enzymolysis, performing complexing, performing washing separation and performing drying treatment on rice flour or rice protein flour, so that the rice flour or the rice protein flour with a low content of metal is finally prepared. According to the method disclosed by the invention, an enzyme method and a chemical method are used, so that the heavy metal in the rice flour or the rice protein flour is dissociated out in a complexing manner; then solid-liquid separation is performed by a physical method of the stepwise gradient separation of rotational flow, so that the purpose of reducing the content of the heavy metal in the rice flour or the rice protein flour is realized, and a deeply processed product, namely the rice flour or the rice protein flour, with high quality and high added value is prepared. The method is simple to operate and low in cost.

Description

technical field [0001] The invention belongs to the technical field of grain deep processing, and in particular relates to a treatment method for reducing heavy metal content in rice flour and rice protein powder. Background technique [0002] China is the world's largest rice producer. In 2008, the rice output was 189 million tons. Rice is my country's largest food crop. However, the quality of the soil in various places is directly related to the quality of edible rice. However, the adsorption of heavy metal pollution by rice It is obviously stronger than other crop varieties such as corn and soybean. Therefore, the rice is processed through deep processing to obtain high-quality products while removing heavy metals, which also increases the added value of rice utilization. [0003] Heavy metals in rice are mainly combined with amino acids in a chelated state. It is reported that heavy metals in plants are mainly combined with ligands formed by metallothionein, and some of...

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Problems solved by technology

[0004] The invention patent of CN201310140019.1 discloses a decadmium-depleted rice protein and its preparation method and application. The main steps are to use rice as raw material, remove starch with high-temperature amylase to obtain rice dregs, and then use acid solution for decadmium treatment , the acid used is one of food-grade acetic acid, citric acid, malic acid, lactic acid, tartaric acid, oxalic acid, and phosphoric acid. It only plays the role of adjusting the pH value; the acid solution with a large amount of acid and pH<4 has a negative effect on the quality of the protein; the rice protein obtained by centrifugation is directly washed with water, due to the increase of the pH value, the dissolved in the solution Cadmium ions are recombined with rice protein, reducing the efficiency of cadmium removal in the final product; and the supernatant and washing liquid also contain more acid solution, which is not considered in the invention patent that its discharge will pollute the environment a little

[0005] The invention patent of CN103340414A discloses a method for removing cadmium from rice protein. The invention includes the following steps: slurry mixing, acid hydrolysis reaction, impurity removal, sterilization, dehydration, and drying to obtain rice protein powder. The acid hydrolysis reaction of the invention uses Citric acid adjusts the pH value to 3.8-4.2, and then adjusts the pH value back to 5.8-6.2 with alkaline solution. The cadmium ions dissolved under acidic conditions recombine with rice protein as the pH value increases, which reduces the cadmium removal. efficiency; although the invention uses a cyclone scrubber, its main purpose is to separate and remove impurities, and to separate the supernatant from the solid phase after alkali adjustment

[0006] The invention patent of CN104000085A discloses a preparation method of decadmium-removed rice starch and decadmium-removed rice protein powder. In the step of cadmium in rice protein, at least one of acetic acid, lactic acid, oxalic acid, citric acid, tartaric acid, and citric acid with pH<4.2 is mainly used to react according to the volume ratio of rice raw material to acid of 1:3-5. In the invention, the acid is mainly used to adjust the pH value, and this addition has a negative impact on the quality of rice protein and rice starch; then rinse twice with acidic water with a pH value of 6.0-6.5. This step takes into account the The dissolved cadmium ions will recombine with the protein when the pH value increases, but the pH value of 6.0-6.5 will still make part of the dissolved cadmium recombine with the protein and cannot be separated, which reduces the removal rate of cadmium ; After the rinsing step, add an acid with a pH of 2.8-3.0 in the slurry, and, in the next sterilization step, adopt 2-3h under the condition of 80-85° C., such a treatment step is harmful to rice protein, especially rice The quality of starch will have a serious impact. Therefore, the comparative invention patent does not take into account the impact of process steps on product quality while removing cadmium, and the cadmium ions dissolved in the cadmium removal process do not use effective means to separate them. come out

[0007] The invention patent of CN103549234A discloses a method for reducing heavy metals in grains. The invention uses heavy metal-contaminated grains such as rice, wheat, and corn, and by-products of grain processing such as rice bran and bran as raw materials, and obtains heavy metals that meet national standards through several steps. Cereal protein, corn starch or polysaccharide products with cadmium, lead, arsenic, mercury and nickel content, the step of removing heavy metals from cereal protein in this comparative invention patent is mainly to swell the material, adjust the pH value to 2-3, and then go through membrane separation, The solution in the membrane is separated by settling with a solution with a pH value of 4-6, then stirred and washed with tap water, and precipitated and dried. The by-products of grain processing such as bran and bran have complex components, and the efficiency of membrane separation is low, and it is easy to clog, complicated to clean up, and difficult to realize large-scale production and application; For removing heavy metals, the acids used are inorganic or organic acids such as hydrochloric acid, phosphoric acid, acetic acid, citric acid, tartaric acid, etc. Its main purpose is to dissolve heavy metals in starch or polysaccharides, but then directly add tap water for washing, so that the dissolved heavy metals The combined state is re-formed, and the removal efficiency of heavy metals is reduced

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