Effects of salt substitute and Nisin on the flavor development of salt-reduced Pixian douban (broad bean paste)

The high salt content in Pixian douban (PXDB) poses potential health risks. Therefore, this study proposed a salt substitute combined with Nisin to partially replace salt during mold petal fermentation. The effects of different salt-reducing strategies on microbial safety, physicochemical properties, sensory characteristics, and nonvolatile and volatile flavor compounds were systematically investigated. Results showed that, compared to traditional fermentation (17% NaCl), the combination of 15% salt substitute and 0.15 g/kg Nisin (SS + Nisin) during mold petal fermentation, reducing 62.23% of NaCl, significantly inhibited microbial growth and acid production and increased 1.32-fold amino acid nitrogen. During subsequent post-fermentation with 26.91% of NaCl reduction, besides 14.77% of saltiness decrease, it enhanced the reddish-brown color (1.27-fold), umami taste (1.19-fold), sauce (1.18-fold), and mellow aromas (1.17-fold). This was attributed to the increase in umami Glu and Asp, and in various free amino acids and organic acids as precursors for aroma compound development. Meanwhile, salt-reducing fermentation produced more key aroma compounds (especially SS + Nisin), such as 4-ethylphenol, nonanal, linalool, benzaldehyde, and phenylacetaldehyde with their odor-active values over 10 after 90 days of fermentation, thereby benefitting stronger characteristic aromas. Correlation analysis revealed that increased developments of most key aroma compounds were positively correlated with tartaric, lactic, and malic acids, whereas aldehydes were strongly related to free amino acids. These results provided scientific evidence and technical support for the production of low-salt and high-umami PXDB.

Practical Application

The successful application of salt substitutes combined with Nisin in PXDB salt reducing could provide a scientific basis for the industrial production of salt-reduced PXDB and other fermented seasonings with the expectation of ensuring food safety, meeting health trends, and retaining traditional flavors.