Determination of soluble and salt-free solids in soy sauce by refractive method

The content of other substances other than water, salt, and insoluble substances in soy sauce is mainly proteins, amino acids, peptides, sugars, organic acids, etc., and is an important indicator affecting flavor.

Key words : refractive method, soluble salt-free solids, soy sauce, determination

The content of soluble salt-free solids in soy sauce refers to the difference between the total soluble solids content and the salt content, which is an important indicator for determining the quality of soy sauce. National standards as well as industry standards stipulate that the total soluble solids content in soy sauce is determined gravimetrically. Although the gravimetric method is relatively accurate, the operation is cumbersome and rapid measurement cannot be achieved. The content of soluble solids is related to the refractive index of the solution. The application of refractive index to the determination of soluble solids in soy sauce is more. The technical engineer uses ATAGO's Brix meter or Abbe refractometer and online concentration meter to determine the solubility in soy sauce. The content of salt-free solids is basically consistent with the national standard method.

l Main instruments :

Brix meter: PAL-α

Abbe refractometer: NAR-3T

Online concentration meter: CM-800α

Soy sauce samples: available in supermarkets on the market

l Determination method: refractive method

    Take 1-2 drops of soy sauce, drop and hand-held digital display sugar meter or Abbe refractometer, immediately read the content of soluble solids, and subtract the salt content from this value to get the content of soluble solids.

    The Abbe refractometer is easy to operate, the sample is not pre-treated, the inspection cost is low, and the analysis is fast. It takes only 10-20 seconds to measure a sample. Therefore, the refractometry method is suitable for rapid determination of large-volume samples, and is also convenient for the base layer and the site. use.

    When the soy sauce is processed during the production process and the finished product concentration value is controlled to ensure the quality consistency, the online concentration meter can be used instead of the Abbe refractometer for measurement.

l Detection significance:

The higher the content of soluble solids in soy sauce, the higher the content of sugars, organic acids, amino acids and the like in the surface soy sauce. The sugars and amino acids in soy sauce are added in addition to the brewing process, and some are added for the purpose of seasoning. Therefore, it cannot be said that the higher the content of soluble salt-free solids, the better the quality of soy sauce, and the level of soy sauce needs to be combined. Other indicators of soy sauce are judged comprehensively.

l conclusion

The content of soluble and salt-free solids in soy sauce is determined by refractive method, and the accuracy is high, and the operation is simple, the analysis speed is fast, the experiment cost is low, and the method is easy to popularize.