Production of Tofu Using Electrocoagulation Technique for Protein Precipitation

Protein precipitation is a necessary process for a production of tofu. Normally, adding chemical coagulants such as MgCl, CaSO4 and Na2SO4 to separate protein from aqueous phase is a traditional method. However, some previous studies reported that consumption of these chemical coagulants for a long term might cause urinary stone disease. In this study, electrocoagulation (EC) was proposed to solve this problem. During this technique, electrical current was applied into the system for changing of the protein surface charge resulting in agglomeration of suspended protein. Since level of voltages and processing time could affect the tofu quality, this research was therefore aimed to study the effects of different voltages at 10, 20 and 30 V and processing times at 30, 60, 90, 120, 150, 180 and 210 min on a percent yield of curd, texture and color of tofu. The comparison between tofu produced by electrocoagulation and commercial tofu in the terms of texture, color and sensory test was also determined to investigate the suitable condition of electrocoagulation for protein precipitation. The results showed that increase in voltage led to higher percent yield of curd. The voltage of 30 V with processing time at 180 min exhibited the highest percent yield of curd (46.24%). It was also observed that color and texture value of tofu produced using electrocoagulation at 30 V for 180 min were not significantly different when compared to that of commercial tofu with the color value of L* (78.00 ± 1.19), a* (0.64 ± 0.07), b* (20.44 ± 0.34) and the total color difference (3.54 ± 0.97) and the textural properties of hardness (5,113.83 ± 15.10 N), springiness (0.87 ± 0.01 s/s) and gumminess (2,697.77 ± 5.26 N). Moreover, sensory evaluation score of tofu produced by EC at 30 V exhibited the highest value when compared to that at 10 and 20 V.