Optimization of the antioxidant and antimicrobial response of the combined effect of nisin and avocado byproducts

- Avocado byproducts extracts scavenged OH, H2O2, ONOO−, and O2− in in vitro assays.
- Polyphenols such as epicatechin and chlorogenic acid were found in both extracts.
- Avocado peel extract showed higher antioxidant activity than that of the seed or nisin.
- Synergic effect was observed in the antimicrobial response with nisin and extracts.
- Nisin and peel mixture presented maximum antioxidant and antimicrobial responses.

This study is focused on optimizing, by surface response methodology, the mixture of natural additives: nisin (an antimicrobial peptide) in combination with avocado seed or avocado peel extracts (both with antioxidant capacities) in order to maximize the antioxidant activity and antimicrobial response against some food-borne bacteria such as Listeria. The peel or seed extracts used in the mixture showed radical scavenging capacity and antioxidant activity due to their polyphenol composition, including kaempferide, epicatechin, chlorogenic acid, epicatechin gallate, among others. During optimization, the results showed that the major antioxidant response in the mixture was mainly provided by the peel extract compared with nisin, seed and their combinations in different proportions. In the antimicrobial response, a synergic effect was observed in the mixtures of each avocado byproduct extract with nisin. Maximum antioxidant and antimicrobial response were obtained with the mixture of 61% of peel extract with 39% of nisin (p < 0.5, desirability 0.76) at concentrations of 1 mg/mL for each.