PURPOSE: To obtain a high-purity caramel at a low cost by discharging high- voltage current in a stock liquid produced by adding sulfuric acid to a liquid of a carbohydrate of e.g., sweet potato and contacting the super-heat of the generated park flame in vacuum, thereby converting the semilose and cellulose in the stock liquid into caramel.

CONSTITUTION: An electric current of >200V is passed through a hydrated liquid containing semilose and cellulose in a carbohydrate of sweet potato, beet, etc., as a caramel raw material to effect the electric discharge in a liquid. The heat of the spark flame generated by a liquid-spark apparatus for the above treatment is directly contacted to the stock liquid by the vacuum contact action without leaving a space between the flame and the stock liquid. The polymer compounds comprising the semilose and cellulose in the stock liquid are quickly converted into caramel by the asymmetric carbonization action to obtain the objective caramel without generating solid carbonaceous material.