Nanoencapsulated Clove Oil Applied as an Anesthetic at Slaughtering Decreases Stress, Extends the Freshness, and Lengthens Shelf Life of Cultured Fish.

Amanda Esperanza López-Cánovas,María Ros-Chumillas,Elena Chaves-Pozo,Alfonsa García-Ayala,Laura Navarro-Segura,Jorge M O Fernandes,Antonio López-Gómez,Jorge Galindo-Villegas,Isabel Cabas

doi:10.3390/foods9121750

Abstract

In the aquaculture industry, fish are stunned using a wide range of methods, but all of them trigger stress responses and affect the fish flesh quality. Chilled water is considered one of the most efficient methods, but even this is not a stress-free experience for the fish. Anesthetics included in the ice slurry or in water could decrease this stress and delay the loss of flesh quality. In this work, we analyze the effect of clove oil (CO) nanoencapsulated in β-cyclodextrins (β-CD) (CO + β-CD), incorporated in the stunning bath, on the stress response and the organoleptic attributes of fresh marine and freshwater fish from four economically important fish species: Atlantic salmon, European seabass, Nile tilapia, and Rainbow trout. CO + β-CD reduces the time required to induce anesthesia, independently of water salinity, habitat or water temperature. The plasmatic glucose and cortisol levels decreased in all four species, although the concentrations of CO varied between species. Moreover, plasmatic lactate level differed between the marine and freshwater fish. The use of CO + β-CD extended the shelf life of fish from all the species studied (by 3–7 days). In conclusion, using CO encapsulated in β-CD for anesthetizing fish can be regarded as an improved fish-stunning technique that reduces the anesthesia-induction time, decreases the stress response, and extends the shelf life of fresh fish.

Highlights

In aquaculture, it is well-known that fish are exposed to several levels of stress during handling and transport, and as a result of stocking density and pre-slaughter procedures [1,2,3,4]
When clove oil (CO) + β-CD/L FW (β-CD) was incorporated in the water a decrease in both parameters was observed in both species (Figure 1A,B)
In Atlantic salmon, a decrease of the time to reach loss of equilibrium was correlated with the increase of CO + β-CD dose (2.39 ± 0.13 min, 1.73 ± 0.12 min, or 1.21 ± 0.12 min with 40, 50, or 60 mg/L, respectively) (Figure 1A)

Summary

Introduction

It is well-known that fish are exposed to several levels of stress during handling and transport, and as a result of stocking density and pre-slaughter procedures [1,2,3,4]. Foods 2020, 9, 1750 axis, which releases corticosteroids (mainly cortisol) and catecholamines into the circulatory system [4]. The release of these hormones drives metabolic and ionic changes that help fish to survive under stress conditions, but can cause alteration in the flesh quality [1]. Chilled water is frequently used for decreasing the stunning time and minimizing the physiological alterations that may occur because of the stress experienced by fish, improving fish welfare and the quality of the resulting product [1]. The immersion of fish in ice slurry is not a stress-free experience [5] and the inclusion of a proper anesthetic is necessary to decrease such stress and to minimize the induced misbalance of several biological systems. As long ago as 2005, the Canadian Council of Animal Care [12] pointed to the need to study the use of natural agents, such as clove oil (CO), as a viable alternative to chemical anesthesia

Methods

Results

Discussion

Conclusion