Abstract
In the pre-farming period, wild acorns, potatoes and herbs were the most important foodstuffs for our ancestors. The main nutritional component of acorns and potatoes is starch, and they were the staple foodstuffs, while those of herbs are vitamins, minerals and dietary fiber, and they were the subsidiary foodstuffs. But the potatoes and herbs contain harsh components such as alkaloids, saponins, tannins, organic and inorganic salts, and the acorns alone contain tannins with an astringent taste. The harsh components are water-soluble components in the vacuoles of cells. People changed the wild materials to edible foodstuffs by removing harshness with techniques of water-extraction, heat-treatment or dilute acid and alkali-treatment, etc. But the starchy foodstuffs must be heated below 60 ℃ , because the onset temperature of starch gelatinization is about 60 ℃ . Further, the acorns are a nut with a hard pericarp and the tannins are contained in the cotyledon of the seeds. Therefore, people need to grind acorns with a mortar and pestle before removal of tannins. They established the techniques of removal of tannins from the acorns though trial and error.
