Developing a decision support tool for heat process optimization of cod filet

Marthe Jordbrekk Blikra

Research output: Book/ReportPh.D. thesis

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To ensure bacterial safety, high heat loads are frequently applied during preparation of cod in industrial settings and at institutional kitchens. This renders the fish overcooked, dry and tough, and may contribute to unnecessary amounts of food waste. How can we contribute to optimal heating practices for cod, yielding a safe, tasty and healthy meal? In this thesis work, a physics-based mathematical model for coupled transport of heat and moisture during cooking in a convection oven was developed from first principles. Properties and variables needed were measured for untreated and lightly salted cod (1-3 g/100 g NaCl), correlated with the measured protein denaturation, and used to predict the temperature distribution and moisture loss during heating. The model was validated with good agreements between measured and predicted temperature profiles and average concentration of retained water during heating. The model predicted increased retention of moisture with increasing salt concentration in the samples, which was in agreement with experimental data obtained in other studies. During cooking of cod loins, the temperature rise in the loin is coupled with loss of moisture either through evaporation and/or as liquid exudate. The liquid expelled is not pure water and has different properties from those of water. The relative amounts, components and properties of the liquid, referred to as cook loss, was investigated as a function of heating temperature to gain further insight regarding which processes occur during heating. It was found that roughly 10 % of the cook loss was protein, and that the liquid permeability through the muscle tissue was in the order of 10-16 to 10-15 m2, which is higher than reported values for meat. Simultaneously with the transfer of heat and moisture, the cod loin undergoes change in dimensions, which is a complex phenomenon rooted in changes in the muscle structure at microscale. In this work, dimensional change of minced samples was investigated and modeled using a kinetic approach. The degree of changes in properties and dimension depend on raw material quality, including concentration of salt and freeze storage temperature. Unsalted, minced samples stored at a stable, low freezing temperature tend to undergo shrinkage in length and swelling in height. The models developed in this thesis work can be applied as optimization tools to create heating regimes aimed at providing safe, nutritious and tasty meals with cod.
Original languageEnglish
PublisherTechnical University of Denmark
Number of pages139
Publication statusPublished - 2019


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