title: Effects of the beta-glycosidase reaction on bio-conversion of isoflavones and quality during tofu processing.
abstract: BACKGROUND
  Isoflavones are the most common group of phytoestrogens which are present in significantly large amounts in soybean and soy products such as tofu. Isoflavones occur naturally in glycoside forms having lower bioavailability than their aglycone forms. beta-Glycosidase acts as a bio-catalyst for the conversion of isoflavone glycosides to isoflavone aglycones, raising the bioavailability of isoflavones; therefore, it can be used to improve the quality of tofu. We need to establish process conditions for the optimal outcome of the enzyme reaction in tofu.
  
  
  RESULTS
  By using the beta-glycosidase (0.02% w/v) reaction at 55 degrees C for 30 min, a maximum 84.5% conversion of isoflavone glycoside to isoflavone aglycone was obtained. The enzyme reaction caused no significant effects on the sensory acceptability of soft tofu. The hardness of enzyme-treated hard tofu increased with the coagulant amount whereas prolonged heating resulted in decrease of hardness. Incorporation of enzyme reaction before the coagulation process during soft tofu processing provided a sufficient bio-conversion of isoflavones at optimal conditions.
  
  
  CONCLUSIONS
  beta-Glycosidase can be effectively used for the bioconversion of isoflavones in soft tofu manufacturing process at optimal reaction conditions before the onset of coagulation process.
authors.affiliation: R&D Center, Pulmuone Co., Seoul 120-600, Korea.
authors.forename: Young-Gi
authors.initials: YG
authors.lastname: Ryu
authors.forename: Bomi
authors.initials: B
authors.lastname: Won
authors.forename: Hae-Ryung
authors.initials: HR
authors.lastname: Park
authors.forename: Kashif
authors.initials: K
authors.lastname: Ghafoor
authors.forename: Jiyong
authors.initials: J
authors.lastname: Park
mesh_terms: D000328:Adult; D001232:Aspergillus fumigatus / Q000201:enzymology; D055598:Chemical Phenomena; D005260:Female; D005511:Food Handling / Q000379:methods*; D005656:Fungal Proteins / Q000378:metabolism; D006026:Glycoside Hydrolases / Q000378:metabolism*; D006027:Glycosides / Q000378:metabolism*; D006358:Hot Temperature; D006801:Humans; D007529:Isoflavones / Q000378:metabolism*; D008875:Middle Aged; D009994:Osmolar Concentration; D011786:Quality Control; D012677:Sensation; D045730:Soy Foods / Q000032:analysis; D013997:Time Factors
chemical_list: D005656:Fungal Proteins; D006027:Glycosides; D007529:Isoflavones; D006026:Glycoside Hydrolases