I am trying to make alkaline water rice dumplings in large batches (about 50 kilos) I bought my glutinous rice grains directly from the producers and thus there are some rice grains mixed into the batch. Alkaline water rice dumplings are not supposed to have rice grains in them. Rice grains could not be cooked and merged together with the rest of the glutinous rice thus they will harden within the dumplings and the taste of the dumplings will be inconsistent.

Traditional methods of separating the rice grain from the glutinous rice grains require manual work in which you "eye" for the transparent grain (rice grain) from a small batch of rice pile and pick it out one grain at a time. This requires a lot of effort and time and is prone to human error. A single rice grain in the dumpling can cause deteriorate the eating experience tremendously.

How can I speed up the process of separating the rice grain and increase the accuracy of the system at the same time without relying on complex industrial machines or robots?

I tried to do research on it and even sought out ChatGPT and it was suggested to use the density separation method. Which places the rice grains in a liquid that relies on the density difference between the glutinous rice grain and the rice grain due to the difference in the amylase contents?

Will this method work? if it works, how do I measure the different densities between rice grain and glutinous rice grain? how do I make the liquid that can cause either rice grain to float as a form of separation?

  • I don't know for sure, but density did spring to mind when I saw the question. I suspect the density difference will be tiny and as a consequence you would have to be prepared for some failure rate -either discarding some wanted grains or still having some unwanted. You could determine the densities empirically using salt solutions of different concentrations, especially if you had of rice of each type to hand. However it is likely to be precision work and you would probably need some fine scales to get the right concentrations of salt at the end-points. cont...
    – bob1
    Commented Jul 18, 2023 at 10:55
  • ...You might also have batch-to-batch variation and have to tweak it for each time you do the separation unless you have a weather independent storage solution (climate controlled room) to avoid humidity variation of water content in the rice. Also you would need a way of drying the rice afterwards if you don't plan on using it all immediately.
    – bob1
    Commented Jul 18, 2023 at 10:59
  • The reason that complex industrial machines exist is that it's a complex task. Designing, establishing and monitoring a process that uses the density method isn't likely to be cheaper or less complex than buying a sorting machine. Before you go by density, have you even checked food regulations? Rice is a hygroscopic food, and when you submerge it in a liquid, you'll have traces of the liquid's contents "contaminating" the rice, is this allowed by regulations where you sell, and under what conditions (e.g. if you have to add a E number on your label, you may lose customers).
    – rumtscho
    Commented Jul 18, 2023 at 13:46

1 Answer 1


Use gentle sideways shaking action to separate them. The concept is known as vibratory fluidization and is easy to replicate at home to a reasonable extend enough to be useful. It will be better if you use a rigid wall container, like a metal bucket, and then you can knock on the outer side with a tool to induce vibrations. The grains differ a little by weight, and shaking them sideways in a container will make the heavier ones sink in the lighter ones.

Avoid asking such questions to techniques like ChatGPT, as those tend to habitually spew bullshit disguised as legitimate advice. Even a broken clock will tell you the right time two times a day, but that's all.

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