# The effect of citrus essential oil encapsulation on antioxidant capacity and bacterial growth in a milk matrix during storage

## TL;DR

Encapsulating citrus essential oil in particles helps preserve its antioxidant and antibacterial effects in milk during storage.

## Contribution

A novel encapsulation method using zein particles with a slow-release mechanism is shown to preserve bioactive properties in milk.

## Key findings

- Slow-release encapsulated citrus essential oil showed significant DPPH scavenging activity in milk.
- Slower release rates of citrus essential oil led to greater bacterial inhibition compared to fast-release versions.
- Milk components influenced the antioxidant capacity and antibacterial effectiveness of encapsulated substances.

## Abstract

The functionality of food can be improved by supplementing it with bioactive substances. However, the interactions between these substances and food components can compromise their functional efficacy. This study investigated the potential to reduce functional losses by encapsulating citrus essential oil (CEO) in zein particles (ZPs). We examined the antibacterial and antioxidant efficacy of these encapsulates at different CEO release rates in skimmed and whole milk samples. Slow CEO‐releasing ZPs were developed by coating CEO‐loaded ZPs with calcium phosphate and alginate gel (CaP‐AlgGel‐CEO/ZPs), while fast CEO‐releasing ZPs served as controls.

The solubilization of CEO was enhanced in milk probably by hydrophobic interactions and colloidal stabilization provided by milk components. This increased solubilization of CEO facilitated its release from CEO encapsulates. Free CEO exhibited no DPPH scavenging activity when dissolved in milk. In contrast, CEO encapsulates, especially those with a slow‐release rate, demonstrated significant DPPH scavenging activity. In comparison with the fast‐release counterparts, the slower CEO release caused greater bacterial inhibition. Principal component analysis revealed that the type of matrix influenced the antioxidant capacity of supplemented bioactive substances, while storage time affected their antibacterial effectiveness.

This study underscores the advantages of encapsulation techniques in preserving the functional efficacy of bioactive substances by mitigating adverse interactions with food components. © 2025 The Author(s). Journal of the Science of Food and Agriculture published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.