title: Change in texture improvement of low-fat tofu by means of low-fat soymilk protein denaturation.
abstract: BACKGROUND
  Tofu made from low-fat soy flour is a nutritional food for consumers and economically benefits the food processor. However, low-fat tofu has poor textural quality, especially insufficient firmness. Stepwise heating (heating at 75 °C, followed by holding at 95 °C) of full-fat soymilk increases gel properties. Therefore we evaluated the two-step heating of low-fat soymilk to improve tofu texture.
  
  
  RESULTS
  The denaturation enthalpy and temperature of β-conglycinin and glycinin were higher in low-fat tofu compared to high-fat tofu. The viscosity of low-fat soymilk and texture of tofu by one-step heating were weaker than full-fat soymilk and tofu. However, the two-step heating increased free sulfhydryl groups and viscosity of low-fat soymilk to a value higher or similar to conventional soymilk. The syneresis of low-fat tofu was reduced about 30% and hardness was higher (131.0 N) by the two-step process compared to one-step heating of full-fat tofu (101.4 N) by the one-step process. The microstructure of low-fat tofu became finer, denser and more homogeneous by the two-step heat process.
  
  
  CONCLUSIONS
  Low-fat tofu produced by denaturing the two major soy proteins separately had improved textural qualities similar to full-fat tofu as a result of increased hydrophobic interactions between denatured protein molecules.
authors.affiliation: Department of Human Ecology, Graduate School, Korea University, Seoul, Korea 136-701.
authors.forename: Woo-kyoung
authors.initials: WK
authors.lastname: Shin
authors.forename: Wallace H
authors.initials: WH
authors.lastname: Yokoyama
authors.forename: Wook
authors.initials: W
authors.lastname: Kim
authors.forename: Louise
authors.initials: L
authors.lastname: Wicker
authors.forename: Yookyung
authors.initials: Y
authors.lastname: Kim
mesh_terms: D052179:Antigens, Plant / Q000737:chemistry; D055598:Chemical Phenomena; D003545:Cysteine / Q000032:analysis / Q000737:chemistry; D003553:Cystine / Q000032:analysis / Q000737:chemistry; D018752:Diet, Fat-Restricted; D005511:Food Handling; D063427:Food Quality; D005782:Gels; D005916:Globulins / Q000737:chemistry; D006244:Hardness; D006358:Hot Temperature; D006801:Humans; D057927:Hydrophobic and Hydrophilic Interactions; D055595:Mechanical Phenomena; D014674:Plant Proteins, Dietary / Q000737:chemistry*; D011489:Protein Denaturation; D056910:Republic of Korea; D055314:Seed Storage Proteins / Q000737:chemistry; D045730:Soy Foods / Q000032:analysis*; D041942:Soy Milk / Q000737:chemistry*; D030262:Soybean Proteins / Q000737:chemistry*; D013499:Surface Properties; D014783:Viscosity
chemical_list: D052179:Antigens, Plant; D005782:Gels; D005916:Globulins; D014674:Plant Proteins, Dietary; D055314:Seed Storage Proteins; D030262:Soybean Proteins; C013894:beta-conglycinin protein, Glycine max; D003553:Cystine; C011474:glycinin; D003545:Cysteine
keywords: gelling; low-fat soymilk; low-fat tofu; stepwise denaturation