Factors affecting methanol content of fermented plant beverage containing <i>Morinda citrifolia</i>

Abstract

Pectin extraction of fresh Morinda citrifolia Linn or Noni using HCl at various concentrations was studied. The highest pectin yield (9.89% w/w) was achieved by using 20 mM HCl. Pectinmethylesterase (PME) activity and specific activity of raw M. citrifolia were 0.276 (μmol/ml. min) and 1.48 (Units/mg), respectively whereas, in the ripen M. citrifolia, they were 1.006 (μmol/ml. min) and 2.96 (Units/mg), respectively. Four formulas (F1, F2, F3 and F4) of the fermented plant beverage (FPBs) were prepared by varying material size (blended and diced) and sterilization process [72°C and using potassium metabisulfite (KMS)] using factorial design. Soluble pectin in FPBs using blended material (F3 and F4) was higher than in FPBs using diced material (F1 and F2). Soluble pectin in FPBs using pasteurization (F1 and F3) was also higher than FPBs using KMS (F2 and F4). At 24 h fermented period, methanol concentration in FPBs using blended material (F3 and F4) was higher than FPBs using diced material (F1 and F2). Methanol concentration in FPBs using KMS (F2 and F4) was also higher than FPBs using pasteurization (F1 and F3). After 24 h fermentation time, methanol concentration in FPBs using blended material (F3 and F4) could not be detected until the end of the fermentation whereas, in FPBs using diced material, methanol was found throughout the fermentation (F1 and F2). The study indicates that the most influencial factor on methanol production in FPBs was raw material size. Other factors were sterilization, PME and pectin, respectively. Thus, the recommended procedure of the fermentation of plant beverage was the use of blended raw M. citrifolia and pasteurization at 72°C for 15 s. These conditions prevent methanol production in FPBs. Therefore, quality and safety of the FPBs will be accepted by consumers.

Keywords: Morinda citrifolia, methanol, pectin, pectinmethylesterase (PME), fermented plant beverage (FPB)

African Journal of Biotechnology Vol. 12(27), pp. 4356-4363