Predicting the Oxidative Degradation of Raw Beef Meat during Cold Storage Using Numerical Simulations and Sensors-Prospects for Meat and Fish Foods.

Preventing animal-source food waste is an important pathway to reducing malnutrition and improving food system sustainability. Uncontrolled color variation due to oxidation is a source of waste as it prompts food rejection by consumers. Evaluation of oxidation-reduction potential (ORP) can help to predict and prevent oxidation and undesirable color changes. A new sensor and two modeling approaches-a phenomenological model and a reaction-diffusion model-were successfully used to predict the oxidative browning of beef ribeye steaks stored under different temperature and oxygen concentration conditions. Both models predicted similar storage durations for acceptable color, although deviating for higher and lower redness levels, which are of no interest for meat acceptance. Simulations under higher oxygen concentrations lead to a few days of delay in the redness change, as observed in practice, under modified atmosphere packaging. In meat juice, variation in ORP measured by the sensor correlated with the redness variation. However, in meat, sensors promote oxidation in the adjacent area, which is unacceptable for industrial use. This paper discusses the potential, limits, and prospects of the mathematical models and sensors, developed for beef. A strategy is proposed to couple these approaches and include the effect of microorganisms.

Structural changes in local Thai beef during sous-vide cooking.

Thai beef (Bos indicus) samples were sous-vide-cooked at temperatures of 60°C, 70°C or 80°C for 2 to 36 hrs and prepared for microstructure characterization by light and electron microscopy. Muscle fibers showed a first phase of lateral shrinkage during the first 6 hrs of cooking at 60-70°C and the first 2 hrs at 80°C followed by a second phase of significant alternations of shrinkage and swelling independently of water transfers. Swelling peaked at 12 hrs. Microstructural changes were more variable for samples cooked at 60-70°C than for samples cooked at 80°C that showed a larger cross-sectional myofibrillar mass area (CSA). Hypercontracted fibers were evidenced at all temperature-time combinations and were associated with adjacent wavy fibers and a characteristic structural evolution in the mitochondria. The role of thermal denaturation of proteins and the ultrastructural analogy of hypercontracted fibers with cold-shortened fibers are discussed.

Simulation of the gastric digestion of proteins of meat bolus using a reaction-diffusion model.

A reaction-diffusion mathematical model has been developed to predict the gastric digestion of meat proteins. The model takes into account pepsin diffusion and proton diffusion in bolus particles and the pH buffering capacity of meat. The computations show that the size of bolus particles and the change in gastric pH have a substantial effect on the percentage of protein digested in the stomach and that the pH buffering capacity of meat has to be accounted for to properly calculate the gastric digestibility of meat. The intensity of surface transfers between stomach fluid and bolus particles has a significant impact on protein digestibility, whereas the variation in pepsin content in the stomach between individuals appears to have little effect on protein digestibility. From a nutritional standpoint, the simulations show that meat protein digestibility is high under normal physiological stomach conditions. However, in a situation where masticatory capacity, hydrochloric acid secretion and gastric motor function performances are reduced, such as with advancing age, protein digestibility rapidly decreases, ultimately leading to near-zero digestibility value in the stomach in extreme cases.

In situ characterization of acidic and thermal protein denaturation by infrared microspectroscopy.

Foods meet acid pH during gastric digestion after cooking. An in situ infrared microspectroscopy approach was developed to detect the effects of heat and acid treatments on protein structure separately. Infrared spectra were obtained from meat samples treated with heat and/or acid, and wavenumbers accounting independently for the treatments were extracted by principal component regression. Extreme-acid treatment (pHinitial 2.0) was well predicted (0.5% error) by a simple ratio of as-observed spectral intensities at 1211 and 1396 cm-1, reflecting a perturbation in the vibration of amino acid residues (phenylalanine, tyrosine and aspartic acid) by protein unfolding and protonation. Using the imaging mode of an IR microscope, meat protein acidification was evidenced with high spatial resolution. The heat effect was well discriminated from the acid effect by the ratio of as-observed intensities at 1666 and 1697 cm-1 (0.9% error), indicating content of aggregated ß-sheets relative to α-helix structure.