Enzymolysis method for starchy material and method for preparing citric acid

Abstract

The invention provides an enzymolysis method for a starchy material, which is characterized by comprising the following steps of: (1) mixing starch slurry prepared from the starchy material and partial amylase to obtain a mixture, contacting the mixture with steam, ensuring that the mixture contacted with the steam has the temperature of 100 to 120DEG C, and keeping at the temperature for 4 to 10 minutes; and (2) flashing the mixture contacted with the steam in the step (1), cooling to the temperature of between 85 and 99DEG C, and mixing with the rest amylase for enzymolysis. By the method, the protein flocculation effect can be improved, so that solid and liquid are easy to separate, the content of residual starch in enzymolysis residue is reduced, and the dextrose equivalent (DE) value of enzymolysis clear liquid is effectively improved; in addition, the sugaring yield is improved, the sugaring grain consumption is reduced, and the grain consumption and cost for producing citric acid are reduced.

Description

Technical field [0001] The invention relates to an enzymatic hydrolysis method of starch material and a preparation method of citric acid. Background technique [0002] Citric acid is an organic acid widely used in beverage, food and medicine industries. At present, citric acid is mainly prepared by fermentation. For example, it is generally necessary to pulverize the starch material first, mix the pulverized product with water to obtain a starch slurry, and mix the starch slurry with enzymes for enzymatic hydrolysis to obtain an enzymatic hydrolysis product (enzymatic hydrolysis). Liquefaction solution), and inoculate Aspergillus niger into the fermentation broth containing the enzymatic hydrolysis product to ferment to produce citric acid. [0003] In the above process, the enzymatic hydrolysis (liquefaction) of starch raw materials is very important. The current enzymatic hydrolysis (liquefaction) process of starch raw materials mostly uses a secondary jet liquefaction process...

AI Technical Summary

Problems solved by technology

[0004] This process has the following defects: (1) gelatinization is not complete: after many starchy raw material granules with larger particle sizes absorb water and swell, they are only shown to be hydrolyzed by starch on the surface; Granules, only the amorphous region of starch and the crystalline region on the surface swell, and the inner crystalline region is difficult to achieve gelatinization

(2) Incomplete liquefaction: As we all know, it is difficult for amylase to interact with unswollen starch crystal regions. Therefore, although more amylase has been added, the starchy raw material is still difficult to liquefy, even if the liquefied liquid is finally tried with iodine. Qualified, but liquefied hydraulic filtration is difficult, the filter residue is viscous and has high water content, which not only brings part of the sugar liquid into the filter residue, but also causes waste of amylase

(3) High residual starch: the ungelatinized crystalline starch is finally trapped in the filter residue during the press filtration process, resulting in high residual starch detected by the enzymatic method of the filter residue

(4) High turbidity of liquefied supernatant: due to poor protein flocculation, it is difficult to press filter, resulting in the mixture of protein and starch adhering to the filter cloth, making press filtration difficult, and the turbidity of the supernatant coming out is too high

(5) Low yield of liquefied supernatant: Since part of the starch and sugar solution are trapped in the filter residue, the yield of supernatant becomes low

(6) The DE value (the content of reducing sugar than dry matter) of the prepared clear liquid is higher, which is unfavorable for citric acid fermentation: due to incomplete gelatinization, liquefaction is more difficult, and the iodine test is not easy to pass. In order to make the iodine test pass, just More amylase must be added, and under the same conditions, the DE value increases with the increase of amylase, and the DE value of the liquefied serum obtained by this method is 28-30%

(7) High grain consumption for sugar production: Since the filter residue contains a certain amount of starch and sugar, the grain consumption for sugar production is high

[0005] There is a certain correlation between the above defects, which are directly or indirectly caused by incomplete enzymatic hydrolysis of starchy raw materials. Therefore, it is necessary to develop a method for improving the enzymatic hydrolysis process of starchy raw materials

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