Effects of Different Coagulants on Quality Characteristics and Flavor Components of Tofu

To study the quality characteristics and flavor components of tofu made with different coagulants, the effects of MgCl₂, CaSO₄, lactic acid, acetic acid, GDL and fermented soy whey (FSW) on the yield, texture, chromatic aberration, microstructure and volatile flavor compounds of tofu were analyzed by texture profile and scanning electron microscopy analysis and solid phase microextraction coupled with gas chromatography-mass spectrometry (SPME-GC-MS). The moisture content and yield of the FSW tofu and GDL tofu were significantly higher than those of other coagulants tofu (P<0.05). The acetic acid tofu had the highest hardness (244.04 mN) and chewiness (176.34 mJ) and the lowest L^* value (82.77). CaSO₄ tofu and GDL tofu had dense network structure, while lactic acid tofu had rough surface and pores. In addition, a total of 100 volatile flavor compounds of soymilk and tofu made with different coagulants, including alcohols, aldehydes, ketones, esters, acids and phenols, were detected. The total volatile compounds in soy milk were significantly higher than those in tofu with different coagulants (P<0.05). FSW tofu had higher numbers of volatile compounds and lower total amount of the compounds of beany flavor. The cluster analysis showed that the volatile flavor characteristics of lactic acid tofu, acetic acid tofu and MgCl₂ tofu had high similarity, while CaSO₄ tofu and GDL tofu had high similarity. The principal components analysis shows that the volatile flavor compounds contributed greatly to the flavor of tofu were 2, 4-nonadienal, (E)-2-octenal, 1-hexanol, (E)-2-decenal and (E, E)-2, 4-decadienal. Sensory evaluation showed that CaSO₄ tofu and FSW tofu were superior to other coagulants tofu. Therefore, the type of coagulant has significant effects on the yield, texture, chromatic aberration, microstructure and volatile flavor compounds of tofu, and CaSO₄ and FSW can make tofu with better quality and flavor, and their tofu have higher consumption appeal.