Oil uptake by beef during pan frying: impact on fatty acid composition.

Fat entering food during frying needs to be monitored to control the nutritional properties of the products: fat penetration and fatty acid (FA) composition. The large difference between the apparent diffusion coefficients of lipids and meat fibers allows the use of diffusion-weighted magnetic resonance imaging (DWI) to measure oil uptake profiles. This method, in association with analysis of FAs by gas-liquid chromatography, predicts nutritional changes. Beef samples from finishing cows given control feed or high FA supplemented feed were fried in olive oil at 130 °C and 180 °C. Frying oil penetration was quantified by computing oil signal profiles from 3D DWI. Oil penetration was deeper at 180 °C (5 mm) than at 130 °C (2.5 mm), consistent with oil penetration processes. Oil penetration evaluated with DWI was correlated (R²=0.82) with biochemical analysis of FA composition. These results highlight the predominance of oil uptake over animal feed effects in the first millimeters of in-plane fried meat.

Sarcomere length determination using front-face fluorescence polarization.

Tryptophan is the major intrinsic fluorophore in muscle and is a constituent of proteins that have two preferential alignments both parallel and perpendicular to muscle fibre direction. A simple theoretical model and an experimental method based on front-face fluorescence polarization technique for tryptophan fluorescence anisotropy measurements were used for the estimation of post-rigor sarcomere length in beef in the range 1.6-3.4µm. Fluorescence anisotropy and structure-related model variables displayed changes in cold-shortened samples compared with normal and stretched ones. The anisotropy of contracted samples was lowered by misalignment of fibres in the sample. This method can therefore be used for in-line detection of cold shortening which has meat toughness as a consequence.