How Can You Make Sweet Potatoes Sweeter?

🍠There are many varieties of sweet potatoes in Japan, and they are all sweet and delicious. In particular, sweet potatoes baked slowly at a low temperature using stones are exceptionally sweet and delicious. In Japan, there are kitchen cars selling sweet potatoes roasted with stones. How is this sweetness produced?

🍠The key to sweetness is maltose, which is produced by the decomposition of starch. This decomposition reaction is catalyzed by beta-amylase, but the starch must be gelatinized. Gelatinization usually occurs at 70-75 °C, depending on the variety. On the other hand, the activity of β-amylase decreases significantly at temperatures above 80°C. In summary, heating at ~75 °C will result in a sweeter product. Heating by the microwave oven will not produce enough maltose because the temperature rises so quickly.

🍠If you just want to sweeten, heat at ~75 °C. However, if cooked at this temperature for a long time, the sweet potatoes may become hard. This is due to the hardening of pectin. Note that at lower temperatures, hardening is more likely to occur.

Source of graph: Reference 2

#food science #chemsitry #organic molecule

📖Reference

1. Y. Nakamurai, et al. “The Effects of β-Amylase Activity andStarch Pasting Temperature on Maltose Generation in SteamedStorage Roots of Sweet Potato” Nippon Shokuhin Kagaku Kogaku Kaishi, 2014, 61, 577.

2. K. Katayama “「焼き芋」の甘さの秘密” 化学と教育, 2019, 67, 318.

3. M. Fuchigami “Changes in Pectic Substances of Vegetables and Fruit during Cooking” 日本家政学会誌, 2014, 65, 479.

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