Application of response surface methodology in process optimization of Soytofu and their sensory evaluation

Abstract

The objective of investigation was to optimize the levels of four salt and three acid coagulants and coagulating temperature of soy milk so as to prepare quality soytofu by employing Response Surface Methodology (RSM) and to select an ideal one among the seven coagulants.  To optimize the level of coagulant and temperature, Three Level Factorial Design was used. This included three levels of salt (0.2, 0.4 and 0.6%, w/v on soy milk basis) and acid (0.15, 0.25 and 0.35%, w/v on soy milk basis) coagulants with three levels of coagulating temperature (75, 82.5 and 90^oC). Thus 13 RSM experiments including five central and eight axial points were conducted to produce soytofu samples with each of the coagulant. Soytofu samples were evaluated organoleptically on the nine point hedonic rating scale. Results revealed that the optimum concentration of coagulants (% w/v, on soymilk basis) and coagulating temperature (^oC) of soymilk for making quality soytofu was 0.6, 86.55, 0.57, 84.9, 0.6, 87.23, 0.46, 86.18, 0.35, 89.33, 0.3, 80.25 and 0.15%, 87.45^oC, respectively for CaCl₂, CaSO₄, MgCl₂, MgSO₄, lactic acid, acetic acid and citric acid coagulants. Preparation of soytofu sample from RSM optimized level and their organoleptic evaluation indicated that among the seven coagulants calcium chloride was best for making quality soytofu and it contained 68.59, 50.3, 12, 5.9 and 15.35% moisture, protein, crude fat, ash and carbohydrates, respectively.