title: Effects of koji-making with mixed strains on physicochemical and sensory properties of Chinese-type soy sauce.
abstract: BACKGROUND
  Two kinds of soy sauces were prepared with Aspergillus oryzae koji (SSAO) and mixed koji (SSAOM, A. oryzae mouldstarter:Monascus purpureus mouldstarter = 1:2, w/w) respectively. The effects of mixed koji on the essential indices, oxygen radical absorption capacity, color indices, free amino acids and volatile compounds of soy sauce have been studied, followed by a sensory evaluation between SSAO and SSAOM.
  
  
  RESULTS
  The contents of non-salt soluble solid, reducing sugar, total acid, total nitrogen and amino nitrogen in SSAOM increased by 21.50%, 9.88%, 15.35%, 5.98% and 41.43%, respectively, compared with the control SSAO, owing to the higher activities of acid protease and glucoamylase in the mixed koji. Moreover, SSAOM showed higher antioxidant activity, higher levels of free amino acids and much more attractive color. Meanwhile, flavor groups such as esters, aldehydes, pyrazines and sulfur-containing compounds in SSAOM were also improved. The contents of free amino acids and aroma compounds were consistent with the sensory evaluation. According to descriptive sensory analysis, SSAOM showed higher intensity for sweet and umami attributes; in addition, higher flowery, burnt, fruity and caramel-like attributes were perceived in SSAOM, while SSAO showed higher ethanolic and sour attributes.
  
  
  CONCLUSIONS
  The investigated soy sauce prepared with mixed koji can be considered as an effective method to accelerate the fermentation process and improve the flavor of soy sauce.
authors.affiliation: College of Light Industry and Food Science, South China University of Technology, Guangzhou 510640, China.|Sericulture and Agri-food Research Institute, Guangdong Academy of Agricultural Sciences, Guangzhou 510610, China.
authors.forename: Zhi-Yao
authors.initials: ZY
authors.lastname: Chen
authors.affiliation: College of Light Industry and Food Science, South China University of Technology, Guangzhou 510640, China.
authors.forename: Yun-Zi
authors.initials: YZ
authors.lastname: Feng
authors.affiliation: College of Light Industry and Food Science, South China University of Technology, Guangzhou 510640, China.
authors.forename: Chun
authors.initials: C
authors.lastname: Cui
authors.affiliation: College of Light Industry and Food Science, South China University of Technology, Guangzhou 510640, China.
authors.forename: Hai-Feng
authors.initials: HF
authors.lastname: Zhao
authors.affiliation: College of Light Industry and Food Science, South China University of Technology, Guangzhou 510640, China.
authors.forename: Mou-Ming
authors.initials: MM
authors.lastname: Zhao
mesh_terms: D001236:Aspergillus oryzae / Q000502:physiology*; D002681:China; D005285:Fermentation; D005511:Food Handling / Q000379:methods*; D032741:Monascus / Q000502:physiology*; D045730:Soy Foods / Q000032:analysis*; D013649:Taste
keywords: Aspergillus oryzae; Chinese-type soy sauce; Monascus purpureus; flavor volatile; free amino acid; sensory attributes