Optimization and anthocyanin extraction from purple yam (Dioscorea alata) peels for food colorant and antimicrobial
2023
Sandoval, A.L.C. | Sumague, Ma.J.V. | Santiago, D.M.O. | Cirunay, A.R.T. | Galang, M.B.B. | Felismino, R.M. | Avorque, F.L.D.
Purple yam (Dioscorea alata) is known to possess a vivid purple color due to the substantial amounts of anthocyanins that it contains. This study utilized purple yam peels (PYP), an often-discarded part of purple yam processing, to investigate its potential as a colorant and as an antimicrobial, for future food applications. Response surface methodology (RSM) was used to generate the levels of the factors (solute/solvent ratio, ethanol concentration, and citric acid concentration) that would result in an optimum total monomeric anthocyanin content (TAC) of the extract. It was found that the optimum conditions for anthocyanin extraction from purple yam peels were 1:5 SSR, 40% EtOH, and 2% CA, resulting to an observed TAC value of 74.243 mg/L After establishing the optimum extraction conditions, the color stability and antimicrobial activity of the optimized PYP extract was then evaluated. A significant decrease in the intensity (C*) of the extract was observed after two weeks of storage at 4 deg C. A very distinct difference in its perceivable color (Delta E = 6.03) was also observed by the end of the 28-day storage period. Antimicrobial testing revealed that the crude, optimized PYP extract showed inhibition against the test microorganisms (E. coli, S. typhimurium, and S. aureus). However, determination of minimum inhibitory concentration (MIC) revealed that only the E. coli and S. aureus were inhibited when the optimized extract was diluted to 50%.
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