So my kids like to take 'sushi' (that is, variations without raw fish) and sushi-like dishes (onigiri/onigiraza, musubi etc) to school for lunch. However in the mornings I don't have time to fully make them. So I have to make them the evening before. Over the, say, 15 hours between preparation and consumption, the rice tends to dry out quite noticeably. Are there any tricks to keep the rice fresh longer? Is there any difference between using plain vs seasoned (rice vinegar, mirin) rice? I've tried wrapping the dish tightly in cling film, which helps a little, but not as much as I would have expected. I've also tried doing prep (including cooking rice) the night before, and assembly in the morning. In that case the rice is less dry (I presume because the surface area is smaller) but by the time it's lunchtime, most gains seem to have been lost - plus it's quite time consuming/stressful doing even only the assembly in the morning.

I've thought about making the rice more moist but I'm not quite sure how to go about that in a way that it doesn't turn it into a mush, and most of the excess water would be absorbed by the nori anyway - which brings its own set of problems. (the nori going soft is already a problem when storing for more than say an hour)

Are there any other tricks?

  • This isn’t necessarily a duplicate of the other question as you have other issues (whatever is with the rice in the sushi), and may have other options as you have the su (salt, sugar, vinegar mixture) to work with
    – Joe
    Sep 26, 2023 at 11:33
  • And the top of answer in the ‘duplicate’ question of rinsing the rice will not work for sushi, as you need it sticky
    – Joe
    Sep 26, 2023 at 11:34
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    Part of the issue isn’t actually drying out— it’s starch retrogradation (the starch changes into a different form, which is firmer). There must be a way to deal with this, as Japanese convenience stores sell pre-made onigiri (rice balls), although there may also just be the expectation that pre-made stuff will be slightly sub-par compared to fresh.
    – Joe
    Sep 26, 2023 at 11:46
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    Thank you, 'starch retrogradation' is the magic term that lead me to many more resources. This seems to be a widely studied problem without obvious working solution even for the commercial food industry, let alone accessible to the home cook. I especially found jstage.jst.go.jp/article/jnsv/65/Supplement/65_S134/_article an interesting overview, although I have yet to dive into its references. Practically speaking it seems that my best bet for the short term is to not cool the rice at all (I can program my rice cooker so that it's done in the morning) and to assemble last minute.
    – Roel
    Sep 28, 2023 at 7:37
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    I suspect that it will be okay if you work in a clean environment, but make sure to use salt and vinegar as a preservative as you don’t want to run into ‘fried rice syndrome’. Maybe also check some of the bento (Japanese packed lunch) websites for suggestions/advice? NHK has an English language show ‘Bento Expo’: www3.nhk.or.jp/nhkworld/en/tv/bento
    – Joe
    Sep 28, 2023 at 10:00

1 Answer 1


You can significantly improve the texture of slightly stale rice by sprinkling water on it and then sticking it in the microwave for thirty-ish seconds (the exact time probably depends on your microwave). I do this all the time to day-old refrigerated white rice.

Like you mentioned, cling-wrap helps too, as does putting the rice in an airtight container. Maybe you could try making the rice the night before, microwaving it in the morning before you pack it, and then packing it in a good airtight container? Usually I find a thermos retains moisture better than a regular plastic tupperware box.

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