This technique considers both responses as equal in weight and
importance. Fig. 1E and F presents the estimated surface response
and contour plot in which the maximum effect is observed in the
interaction of nisin with peel (p < 0.5, desirability 0.76); with regard
to numbers, a mixture of 39% of nisin and 61% peel maximized
both effects (ORAC value of 194 mg of trolox equivalents/mL,
and lag time of 22.4 h). The seed extract was discarded because it
did not provide a good antioxidant or antimicrobial response
compared with those of nisin or peel. It could be added that
perhaps this mixture requires a final color, such as a natural color
additive similar to curcumin (Dabas, Elias, Lambert, & Ziegler,
2011).
4. Conclusion
Peel extract presents more antioxidant and radical scavenging
capacity than seed extract due to its polyphenols content, such as
procyanidins, epicatechin and other non-identified compounds.
These were mainly responsible for the antioxidant response in the
mixture of the three natural additives utilized in this study. The
peel or seed extract, in combination with nisin, presents a synergic
effect in the antimicrobial response. The mixture of nisin and avocado
peel comprises the optimal mixture that maximizes the
antioxidant and antimicrobial response. The use of a natural antioxidant
such as avocado peel, in combination with a natural conservative
such as nisin, provides a novel combination that may
reduce the amount of nisin employed at the industrial level, not
only reducing costs, but also promoting the use of natural compounds
that are derived from agro-industrial byproducts with good
antioxidant and antimicrobial effects. This mixture also favors the
trend towards the use of natural additives.
Acknowledgments
The authors thank to CONACyT for the scholarship (230991) of
Mariel Calderon-Oliver during her Ph.D. studies.