A 3D MRI-based Numerical Model Dedicated to Industrial Thawing of Large Tuna Fishes

ABSTRACT

Industrial thawing of raw tuna fishes for the canning industry is of great importance in the global economy. Due to the heat transfer limitations within large sample pieces, these processes need to be improved to reduce fluid and energy consumption. In this work, the water immersion thawing process of yellowfin tuna was studied from both experimental and numerical approaches. First, the heat transfer model is validated with precooked tuna samples undergoing forced-air convection thawing. Then, the water immersion thawing process of yellowfin was studied with temperature measurements performed under an industrial environment. The numerical model considers the real geometry of the yellowfin using magnetic resonance imaging (MRI) integrated into a 3D finite element model. Overall, good agreement was found between experimental and predicted temperatures by considering a uniform convective heat transfer coefficient. A simplified 2D model can accurately predict the thawing time, but a 3D model is needed to predict the spatiotemporal temperature distribution in the product. The results have also shown the strong influence of the ambient temperature on the thawing time. This original approach considering the real fish geometry could now be used with different sized-tuna and various thawing kinetics to reach optimal processing conditions while improving product quality.

KEYWORDS:

• Thawing
• tuna
• 3D MRI
• modelling
• heat transfer

Nomenclature

ρ	=	= density, kg.m−3
Capp	=	= apparent specific heat capacity, J.kg−1.K−1
k	=	= thermal conductivity, W.m−1.K−1
h	=	= convective heat transfer coefficient, W.m−2.K−1
$H{R}_z$	=	= orthogonal conductive heat flux, W
$H{R}_{tot}$	=	= inward heat flux throughout the overall surface, W
S	=	= surface, m2
T0	=	= initial temperature, K
Text	=	= external temperature, K
X, Y, Z	=	= spatial coordinates, m
$x_{fi}$	=	= frozen water mass fraction, %
$x_{fw}$	=	= freezable water mass fraction, %
fi	=	= frozen water mass fraction $x_{fi}$ divided by the freezable water mass fraction $x_{fw}$
$\mathrm{\Delta }{H}_w$	=	= latent heat of melting for pure water, J/kg
$H_{Ti}$	=	= enthalpy of the product at a temperature ranging from −5 to 0°C
$X_w$	=	= initial water content (wet basis)

Acknowledgments

The authors are grateful to the research team “In Vivo Imaging Auvergne” – IVIA IMoST U1240 – INSERM (L. Mazuel, J.M. Bonny) for their assistance concerning the MRI scans. The authors would also like to thank M. Volz and E. Goffier from “Plate-Forme d’Innovation Nouvelles Vagues” (PFINV) for their technical assistance during experimental investigations.

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

This work was supported by FranceAgriMer and CITPPM (National Organization for French fish processors) in the framework of “Decongelathon” project.