Application of essential oils as antimicrobial agents against spoilage and pathogenic microorganisms in meat products

Highlights

• A wide variety of valuable compounds can be obtained from essential oils (EOs).

• The application of EOs allows to inhibit the growth of several pathogenic bacteria.

• Phenolic compounds are the main responsible for their microbial activity of essential oils.

• The application of EOs is conditioned by their suitability and their potential toxicological effects.

Abstract

Meat and meat products are perishable products that require the use additives to prevent the spoilage by foodborne microorganisms and pathogenic bacteria. Current trends for products without synthetic preservatives have led to the search for new sources of antimicrobial compounds. Essential oils (EOs), which has been used since ancient times, meet these goals since their effectiveness as antimicrobial agents in meat and meat products have been demonstrated. Cinnamon, clove, coriander, oregano, rosemary, sage, thyme, among others, have shown a greater potential to control and inhibit the growth of microorganisms. Although EOs are natural products, their quality must be evaluated before being used, allowing to grant the Generally Recognized as Safe (GRAS) classification.

The bioactive compounds (BAC) present in their composition are linked to their activity, being the concentration and the quality of these compounds very important characteristics. Therefore, a single mechanism of action cannot be attributed to them. Extraction technique plays an important role, which has led to improve conventional techniques in favour of green emerging technologies that allow to preserve better target bioactive components, operating at lower temperatures and avoiding as much as possible the use of solvents, with more sustainable processing and reduced energy use and environmental pollution. Once extracted, these compounds display greater inhibition of gram-positive than gram-negative bacteria. Membrane disruption is the main mechanism of action involved.

Their intense characteristics and the possible interaction with meat components make that their application combined with other EOs, encapsulated and being part of active film, increase their bioactivity without modifying the quality of the final product.

Introduction

Recently, the harmful effects associated with synthetic preservatives have led to the search new alternatives in natural products (Alirezalu et al., 2020; Aminzare et al., 2016). A wide variety of valuable compounds can be obtained from plants (Munekata et al., 2020). Essential oils (EOs) are secondary metabolites obtained from plants of Asteraceae, Lamiaceae, Lauraceae, Myrtaceae, Rutaceae, Umbelliferae, Zingiberaceae families, among others (Wińska et al., 2019), which are composed by a complex mixtures of volatile compounds of low molecular weight. These valuable substances can be obtained from different parts of the plants like bark, flowers and fruits, leaves, roots and stems (Nikmaram et al., 2018). Most are characterized by being liquid at room temperature, while some could have a solid or resinous appearance. Regarding their colour, this varies greatly, from pale yellow to emerald green and from blue to dark brownish red (Saranraj and Devi, 2018).

Their beneficial effects are mainly attributed to the presence of bioactive compounds (BAC), which are accountable for their anticarcinogenic, anti-diabetic, anti-inflammatory, antimutagenic, antioxidant and antiproliferative properties (Giacometti et al., 2018; Leyva-López et al., 2017). A huge number of preclinical studies have demonstrated these activities, showing their mechanism of action and pharmacological effects (Costa et al., 2020; de Lima et al., 2020). In contrast, there exists a paucity of human clinical trials, which would limit the potential of some essential oils as effective and safe phytotherapeutic agents (Sharifi-Rad et al., 2017).

There are many valuable compounds that are part of their composition, terpenoids and phenylpropanoids are the main, but fatty acids, oxides and sulfur derivatives are also part of their composition. The antimicrobial properties of EOs derived from many plants have been recognized, what becomes in an interesting strategy to extend the shelf life of meat and meat products. The application of EOs allows inhibiting the growth of several pathogenic bacteria and spoilage microorganisms that synthetic compounds are sometimes unable to eliminate. Moreover, they confer beneficial properties with fewer side effects and functional properties. Although EOs have been used since ancient times, their natural origin does not necessarily imply that their use are safe. To ensure this it is necessary to check their efficacy, safety, toxicity, and mechanism of action (Žuntar et al., 2018). The results of these strict quality controls have recognized them as Generally Recognized as Safe (GRAS), allowing their use in food products as safe additives (FDA, 2020). However, sometimes it is necessary to use them in higher concentrations to achieve the same effect as commercial additives, which could cause undesirable effects on the product or even toxicity problems (Ju et al., 2019). This makes necessary to consider their use combined with other preservatives, looking for a synergistic effect that allows achieving a better activity at a lower concentration but sufficient to avoid the appearance of undesirable effects (Pateiro et al., 2018).

The most common extraction techniques involve in the obtaining of EOs are decoction, digestion, drying, hydro and steam distillation, infusion, maceration, percolation, and solvent extraction. However, several disadvantages are associated with these conventional methods. Therefore, using emerging green technologies such as microwave-assisted extraction, supercritical fluid extraction, and ultrasound-assisted extraction, higher quality compounds are achieved, since these technologies allow to preserve BAC of EOs, since they operate at lower temperatures and avoid as much as possible the use of solvents (Chemat et al., 2020; Dima and Dima, 2015; Pateiro et al., 2018; Putnik et al., 2017, Putnik et al., 2018).

However, the possible application of EOs as antimicrobials in meat and meat products has not been studied much yet, since it is necessary to carry out more studies that allow to deepen in their technological and organoleptic effects, their synergistic behaviour and their functionality (bioavailability and bioaccessibility studies). The aim of this review focuses on evaluating the antimicrobial effect of EOs against major meat spoilage microorganisms and pathogenic bacteria, as well as their implication in the sensory characteristics of the product.