Production of Isoflavone Aglycone-enriched Tempeh with <i>Rhizopus stolonifer</i>

Abstract

The regional standard for tempeh recently established by the Codex Alimentarius defines the use of Rhizopus oligosporus, Rhizopus oryzae, and/or Rhizopus stolonifer as soybean tempeh starters. However, there has been little comparative study on the tempeh prepared with these Rhizopus species. This study compared the contents and compositions of isoflavones in tempeh prepared with these Rhizopus species. The contents of total isoflavone aglycones (daidzein and genistein) and the ratio of total aglycones to total isoflavones in the tempeh fermented with R. stolonifer were higher than those with other Rhizopus species. In the isoflavone-enriched tempeh-like fermented soybeans made using hypocotyls and dehulled soybeans, the total aglycone contents and the ratio of total aglycones to total isoflavones were also higher for R. stolonifer than for the other species. These findings highlight the importance of R. stolonifer as the most appropriate Rhizopus species for the production of isoflavone aglycone-enriched tempeh.