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Steffi Sonia, Fiastuti Witjaksono, Rahmawati Ridwan | PubMed | (2015)
Key Takeaways
Sample Definition And Size
The study analyzed resistant starch content in three preparations of cooked white rice: freshly cooked (control), cooled for 10 hours at room temperature (test rice I), and cooled for 24 hours at 4 °C then reheated (test rice II). The clinical portion involved 15 healthy adult subjects in a randomized, single‑blind crossover design.
Study Type
Randomized, single‑blind crossover clinical trial, preceded by laboratory analysis of resistant starch content in rice preparations.
Conflicts Of Interest
No conflicts of interest or funding sources are declared in the PubMed record.
Results Summary
Resistant starch contents were: control rice 0.64 g/100 g; test rice I 1.30 g/100 g; test rice II 1.65 g/100 g. In the clinical study, glycemic response (measured as mmol·min/L) was significantly lower for test rice II compared with control rice (125 ± 50.1 vs 152 ± 48.3; p = 0.047).
Abstract
Cooling of cooked starch is known to cause starch retrogradation which increases resistant starch content. This study aimed to determine the effect of cooling of cooked white rice on resistant starch content and glycemic response in healthy subjects. Resistant starch contents were analyzed on freshly cooked white rice (control rice), cooked white rice cooled for 10 hours at room temperature (test rice I), and cooked white rice cooled for 24 hours at 4°C then reheated (test rice II). The results showed that resistant starch contents in control rice, test rice I, and test rice II were 0.64 g/100 g, 1.30 g/100 g, and 1.65 g/100 g, respectively. Test rice II had higher resistant starch content than test rice I, hence used in the clinical study along with control rice to characterize glycemic response in 15 healthy adults. The clinical study was a randomized, single-blind crossover study. In the clinical study, test rice II significantly lowered glycemic response compared with control rice (125±50.1 vs 152±48.3 mmol.min/L, respectively; p=0.047). In conclusion, cooling of cooked white rice increased resistant starch content. Cooked white rice cooled for 24 hours at 4°C then reheated lowered glycemic response compared with freshly cooked white rice.
Very cool. My immediate question was "how exactly to make this rice?".
Found this study with one "recipe". The researchers tested 3 types of rice: freshly cooked rice, rice left in room temperature for 10 hours, and rice refrigerated at 4 degrees for 24 hours (and then reheated before eaten).
They found the refrigerated rice won.
Specifically, testing on 15 adults, the refrigerated rice lowered glycemic response compared with the fresh rice (i.e. the refrigerated rice was digested more slowly).
(The researchers also found the refrigerated rice had higher resistant starch content vs the room temperature rice -- and so only tested "refrigerated" vs "fresh" on the 15 adults.)
So there you go -- we've been doing it right with overnight fried rice all this while (minus the oil)! But yes, just refrigerate your rice!
(P.S. did anyone compare refrigerated to frozen? Or 24 hours to 48?)