Optimization of the acid treatment of yacon for the inactivation of polyphenoloxidase with maintenance of the functional properties

<p></p><p>Abstract Yacon is a tuberous root that stands out for its high concentration of prebiotic oligosaccharides, mainly fructooligosaccharides (FOS), and some specific phenolic compounds such as chlorogenic acid. However, the presence of these phenolic compounds makes yacon susceptible to enzymatic browning, due mainly to the activity of polyphenoloxidases (PPO). The action of these enzymes can decrease the nutritional value of the product, and also affect its appearance and taste, making it unacceptable for consumption. Thus the objective of the present work was to determine the optimum pH for the activity and for the stability of the yacon PPO, and establish the conditions that result in lower activity of this enzyme using a mild acid treatment, since FOS are susceptible to acid hydrolysis. Following this, a CCRD (Central Composite Rotatable Design) was used to evaluate the effect of different concentrations of citric acid (CA) and different immersion times in the treatment of yacon roots, aiming to inactivate the PPO. It was observed that CA was effective for the partial inactivation of PPO, and that only the CA concentration (linear and quadratic terms) was statistically significant (p < 0.10). The percentage of variance explained (R2) by the model was 85.6%. The treatment selected by the experimental design (2.4% of citric acid for 540 seconds) resulted in a 15% loss of the FOS contents. However, the final product presented 6.84 g FOS/100 g, higher than the minimum amount required by the relevant legislation (2.5 g FOS/portion of product) for a food to claim a functional property, making the technological process proposed in the present work feasible.</p><p>