The effect of lactic acid fermentation in antioxidant activity and total polyphenol contents of the banana (Musa acuminate Linn) juice

Abstract

Fermentation by lactic acid bacteria (LAB) is one promising alternative to improve the benefits of various food and beverages. This research aims to examine the consequence of lactic acid fermentation of banana juice to antioxidant activity, total polyphenol contents, total LAB, pH, titratable acidity, reducing sugar and dissolved protein. The identification of gallic acid and lactic acid monomers was conducted on the most optimal condition of the fermentation by using LC-MS. Banana juice underwent fermentation for 48 hours at 37°C using 2 distinctive cultures: Bifidobacterium bifidum and mixed cultures of LAB. The application of cultures in test subject modified the properties of banana juice with respect to the observed parameters. Mixed cultures of LAB introduced for 32 hours resulted in the highest DPPH (2,2-Diphenyl-1-Picrylhydrazyl) inhibition activity (67.95%) compared to unfermented fresh banana juice (30.66%) and juice fermented using Bifidobacterium bifidum (51.16%). Significant improvement of total polyphenol content was also observed in juice fermented with mixed cultures for 32 hours. Sample’s pH decreased following the increased total LAB and total acid during fermentation. Meanwhile, the values of reducing sugar and dissolved protein tended to fluctuate. Identification of gallic acid monomer at optimal condition revealed the dominant monomer had molecular weight of 171.34 Da whereas identification of lactic acid monomer found that the dominant monomer had molecular weight of 91.27 Da. Our research proposes that fermentation of banana juice using lactic acid bacteria can improve the polyphenol content and antioxidant activity of the juice.