Techniques for sorting out bad (rice) grains by hand

Appropriate Technology Food Processing and Preservation
#1

Hi ECHO family,

Greetings from Panama!

Is there any type of appropriate technology that would help sort out rice grains affected by what I believe is false smut (Ustilaginoidea virens)? Has anyone seen anyone with cool tricks of how to do so, without just going through the entire rice crop and picking it out by hand? Even just one in the cooked rice is not fun to bite into, so lots of man hours are put into this process, even just for a small infection rate.

Thanks,
Laura

1 Like
#2

Hello Laura,

I don’t have expertise in this but was intrigued by your question. Do grains affected by smut have a little more surface area than non-infected grains? If so, am wondering if they could be winnowed out somehow.

In searching for do-it-yourself grain cleaning equipment ideas, I came across the videos below:

—designs in which debris/chaff is separated from good seed by blowing air with a fan: https://www.youtube.com/watch?v=4spHykduUfQ
https://www.youtube.com/watch?v=15GsruCkPXA

—a similar idea using vacuum with a shop vac instead of a blower fan:

There are probably a number of designs people have come up with. Those mentioned above could be modified in various ways (e.g., larger fans with variable speeds). The key is whether or not the affected grains are altered by smut in such a way that they could be separated with moving air.

Any other thoughts out there?

Tim Motis

#3

You need to look for differences in shape, size, or density between the affected seeds and the good seeds. If there are shape or size differences then a sieve or screen could work. A slotted sieve gives separation by the minor (shortest) diameter and a round hold sieve gives separation by intermediate diameter (not the longest or shortest, but the one in between) . If there are differences in seed density and shape or perhaps just seed density then separation with an air stream (described by Tim) could work. If you can allow the seeds to get wet, then density separation can sometimes be achieved by using a solution of the correct density. Solution density can be adjusted by adding the appropriate amount of a salt (sodium chloride may work but there are probably better salts to use).