Change in Iron, Zinc, and Copper Concentrations during Vinegar Production
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Abstract:
Iron-, zinc- and copper-producing pathways and factors influencing vinegar fermentation were examined in this study. Iron, zinc, and copper content at different stages of fermentation during the production of Zhenjiang fragrant vinegar were analyzed using atomic absorption spectrometry. The results showed that these three minerals were mainly present in the soluble state in the liquid phase during various stages of fermentation and were enriched due to precipitate formation. The key factors that influenced the increase in the mineral content in vinegar fermentative substrates originated from corrosion of the fermentation equipment or pipes due to long-term exposure to acetic acid and organic acid, as well as from materials containing iron, zinc, and copper, which might be added during the fermentation process. Iron was introduced into the process mainly at the acetic acid fermentation stage and during sealing for maturation. Furthermore, iron concentration reached highest levels, of 59.69 mg/L at the leaching stage during vinegar production. In addition, alcohol fermentation was the main stage for enrichment of zinc and copper, where their concentrations in vinegar reached 18.12 mg/L and 0.60 mg/L, respectively. The fermentative substrates for vinegar had a strong ability to absorb elemental iron, zinc, and copper, thus contributing regulatory effects on the metal concentration in vinegar. The results indicate that the metal content during vinegar production could be controlled by improving the quality of equipment, optimizing filtering methods, or use of metal ion adsorbents.
