Soy sauce cake as novel flavour enhancer and salt-reducing agent and its application in bakery formulations

Soy sauce cake (SSC) is the underexploited co-product remaining after pressing of fermented soybeans. This study assessed the potential of SSC as flavour enhancer and salt-reducing agent. The nutritional, metabolomic and electronic tongue profiles of SSC were determined. Four bread and oatcake formulations were characterised by sensory and instrumental analyses: full salt (FS), full salt with SSC (FS-SSC), reduced salt (RS) and reduced salt with SSC (RS-SSC). SSC displayed high saltiness and medium umami taste scores. SSC proved suitable as salt-reducing agent in bread, with RS-SSC matching the saltiness, savouriness and acceptability of full-salt products, and as flavour enhancer in oatcake, with RS-SSC exhibiting lower saltiness but similar savouriness and taste intensity to FS. SSC showed high concentrations of flavour-enhancing compounds including aspartate, glutamate and carboxylic acids, which compensated for flavour loss at reduced salt level. This study demonstrated the potential to upcycle SSC as a novel sustainable flavouring ingredient.