Production of prickly pear (Opuntia ficus-indica) vinegar in submerged culture using Acetobacter malorum and Gluconobacter oxydans: Study of volatile and polyphenolic composition

Abstract

Prickly pear (Opuntia ficus-indica (L). Mill.) vinegar has been produced by submerged culture using scale laboratory fermenters at three acetification temperatures (30 °C, 37 °C, and 40 °C). Pure thermotolerant Acetic Acid Bacteria (AAB) which had been previously submitted to molecular identification by PCR–RFLP of the 16S–23S rDNA regions and 16S–23S ITS rDNA sequencing, were used. The AAB used were identified as Acetobacter malorum and Gluconobacter oxydans. The acetic fermentation achieved by A. malorum at 30 °C and 37 °C was more efficient, in terms of acidity, than that accomplished by G. oxydans. The chemical analysis revealed the presence of 85 individual volatile compounds and 17 polyphenolic compounds. The concentration of approximately half the volatile compounds was significantly affected by fermentation temperature, with clearly lower concentrations as temperature increased, whereas few significant differences were observed when comparing the vinegars produced by the two AAB species. Regarding phenolic compounds, significant increases were registered when temperature changed from 30 °C to 40 °C. Furthermore, the vinegars produced by A. malorum presented a greater concentration of phenolic compounds than those produced by G. oxydans.