Influence of prebrining treatments on microbial and biochemical changes during the baceman stage in Indonesian kecap (soy sauce) production

Abstract

Prior to the baceman stage or brine fermentation in Indonesian kecap (soy sauce) production, the soybeans undergo a number of treatments, such as soaking, cooking and a fungal solid state fermentation ( bungkil stage). The influence of these prebrining steps on the baceman stage was investigated. Acidification during soaking inhibited bacterial growth during the solid state fermentation, causing lower initial numbers of bacteria in and a slower acidification of the baceman. Cooking time influenced the softness of the beans and thus fungal growth during the bungkil stage. Increasing the cooking time from 1 to 3 h resulted in a better solubility of macromolecules and gave higher final concentrations of fermentation products and formol nitrogen in baceman. When cooking time was increased from 3 to 5 h only slight differences could be observed. Length of the bungkil stage had some minor influences; the amount of fermentation products and residual monosaccharides decreased by 16% when the length was increased from 2 to 7 d. The highest amounts of formol nitrogen were found with 5 d of bungkil fermentation. The addition of rice flour showed that the absence of yeast fermentation in baceman is related to the lack of sugars after the previous lactic acid fermentation. In addition to yeast fermentation, the growth of fungi during the bungkil stage was also positively influenced by the addition of rice flour. Sun drying and crumbling bungkil caused lower enzyme activities and resulted in lower amounts of formol nitrogen and glycerol. Growth of Pediococcus halophilus during the baceman stage was faster when bungkil was sun dried, although the final concentrations of fermentation products were lower due to a lower content of amino acids which resulted in less buffering. Increasing the amount of bungkil added to salty water caused a similar increase in formol nitrogen and fermentation products.