44E-22 |
Use of chitosan as a coagulant in tofu preparation |
H. K. NO, Department of Food Science and Technology & Research Center for Processing and Application of Agricultural Products, Catholic University of Daegu, 330 Geumnak 1-ri, Hayang-eup, Gyeongsan-si, 712-702, South Korea and S. P. Meyers, Department of Food Science, Louisiana State University, Baton Rouge, LA 70803. Tofu is quite perishable due to presence of rich nutrients and high moisture, with a shelf-life of 1-2 days even under commercial refrigeration. Spoilage of tofu is associated with bacterial growth. Recently, chitosan has attracted considerable attention due to its coagulating ability for protein and biological activities such as antimicrobial, antitumor, and hypocholesterolemic activities. Therefore, it is realized that chitosan, with its partial positive charge, can be used for coagulation of soymilk in tofu preparation. Use of chitosan as a coagulant may enhance the shelf-life of tofu due to antimicrobial activity of chitosan. The objective of the present research was to evaluate chitosan as a coagulant in tofu preparation. The coagulating ability of seven chitosans with different molecular weights was compared and optimal processing conditions (chitosan solvent, chitosan solution to soymilk ratio, chitosan concentration, coagulation temperature and time, and combination of chitosan with calcium chloride) for tofu preparation with a selected chitosan were investigated. Initial optimal processing conditions for tofu preparation were established as follows: chitosan with Mw 59 kDa; chitosan solution type, 1% chitosan/1% acetic acid; chitosan solution to soymilk ratio, 1:8; coagulation temperature, 80 C; coagulation time, 15 min. The sensory quality of tofu prepared under optimal conditions was improved by using a mixture of 1% acetic acid and 1% lactic acid=50:50 (% v/v) instead of 1% acetic acid as a chitosan solvent. Combination of chitosan with CaCl2could reduce the usage of an inorganic salt as a coagulant. Quality of tofu prepared in the laboratory was compared with that of commercial tofu. This study has demonstrated that chitosan can be used as an effective coagulant for tofu preparation, replacing entirely or partly the inorganic salts presently being used in commercial tofu plants. The chitosan-tofu may have a longer shelf-life than tofu made with inorganic salts due to the antimicrobial activity of chitosan.
Session 44E, Nutraceuticals & Functional Foods
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