用大豆和葡萄糖酸-δ内酯为原料制作水豆腐。制作过程中加入吊白块，用酸碱滴定法分别测定水豆腐压滤液、离浆液和蒸馏液中甲醛含量。相同实验条件下，单位质量豆腐的蒸馏液、压滤液和离浆液中甲醛含量依次减小。该法测定甲醛回收率在90%以上（未计豆腐中残留量），操作简便易行，结果准确。

Formaldehyde was used in the production process of the beancurd using soybean and gluconic acid-δ lactone as main materials. The formaldehyde contents in tofu filtrate, liquid separated from beancurd and the distillate of beancurd were measured by acid-base titration. Under the same experimental conditions and in the tofu samples with same weight, formaldehyde contents in the distillate, filtrate and liquid separated from beancurd were reduced in turn. The recovery rate of formaldehyde with this method was higher than 90 % (not including the beancurd residue). This research provided a simple and accurate method for the determination of formaldehyde in the production of beancurd.