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.

Impact of Tumbling Process on the Toughness and Structure of Raw Beef Meat Pieces.

Tenderness is a major factor in consumer perception and acceptability of beef meat. Here we used a laboratory tumbling simulator to investigate the effectiveness of the tumbling process in reducing the toughness of raw beef cuts. Twelve Semitendinosus beef muscles from cows were tumbled according to four programs: T1 (2500 consecutive compression cycles (CC), for about 3 h), T2 (6000 CC, about 7.5 h), T3 (9500 CC, about 12 h), and T4 (13,000 CC, about 16 h). The effect of tumbling on the toughness of raw meat was assessed using compression tests (stresses measured at 20% and 80% of deformation ratios) and microscopic observations made at the periphery and centre of meat samples, and compared against non-tumbled controls. Longer tumbling times significantly reduced the stresses measured at 20% and 80% compression rates, which reflected the toughness of muscle fibres and connective tissue, respectively. At the microscopic level, longer tumbling times led to reduced extracellular spaces, increased degradation of muscle structure, and the emergence of amorphous zones. A 12-h tumbling protocol ultimately makes the best compromise between the process time demand and toughness reduction in beef Semitendinosus meat pieces.

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.

Stoichio-Kinetic Modeling of Fenton Chemistry in a Meat-Mimetic Aqueous-Phase Medium.

Fenton reaction kinetics, which involved an Fe(II)/Fe(III) oxidative redox cycle, were studied in a liquid medium that mimics meat composition. Muscle antioxidants (enzymes, peptides, and vitamins) were added one by one in the medium to determine their respective effects on the formation of superoxide and hydroxyl radicals. A stoichio-kinetic mathematical model was used to predict the formation of these radicals under different iron and H2O2 concentrations and temperature conditions. The difference between experimental and predicted results was mainly due to iron reactivity, which had to be taken into account in the model, and to uncertainties on some of the rate constant values introduced in the model. This stoichio-kinetic model will be useful to predict oxidation during meat processes, providing it can be completed to take into account the presence of myoglobin in the muscle.

Relation between crust development and heterocyclic aromatic amine formation when air-roasting a meat cylinder.

The meat crust that develops during cooking is desired by consumers for its organoleptic properties, but it is also where heterocyclic aromatic amines (HAs) are formed. Here we measured HAs formation during the development of a colored crust on the surface of a beef meat piece. HAs formation was lower in the crust than previously measured in meat slices subjected to the same air jet conditions. This difference is explained by a lower average temperature in the colored crust than in the meat slices. Temperature effects can also explain why colored crust failed to reproduce the plateauing and decrease in HAs content observed in meat slices. We observed a decrease in creatine content from the center of the meat piece to the crust area. In terms of the implications for practice, specific heating conditions can be found to maintain a roast beef meat aspect while dramatically reducing HAs content.

Modelling the Maillard reaction during the cooking of a model cheese.

During processing and storage of industrial processed cheese, odorous compounds are formed. Some of them are potentially unwanted for the flavour of the product. To reduce the appearance of these compounds, a methodological approach was employed. It consists of: (i) the identification of the key compounds or precursors responsible for the off-flavour observed, (ii) the monitoring of these markers during the heat treatments applied to the cheese medium, (iii) the establishment of an observable reaction scheme adapted from a literature survey to the compounds identified in the heated cheese medium (iv) the multi-responses stoichiokinetic modelling of these reaction markers. Systematic two-dimensional gas chromatography time-of-flight mass spectrometry was used for the semi-quantitation of trace compounds. Precursors were quantitated by high-performance liquid chromatography. The experimental data obtained were fitted to the model with 14 elementary linked reactions forming a multi-response observable reaction scheme.

Modelling of pepsin digestibility of myofibrillar proteins and of variations due to heating.

Digestibility of myofibrillar proteins by pepsin was determined by in vitro trials and mathematical modelling. A primary model was developed to predict in vitro digestion kinetics, and a secondary model based on the mechanisms of protein denaturation was then added to take into account the effect of meat heating. Model predictions agreed with measurements in the pH and pepsin concentration ranges 1.8-3.8 and 6-50 U mg(-1) respectively. The utility of the model is illustrated by a simple example where meat is assumed to be heated homogeneously, and myofibrillar proteins to be directly in contact with pepsin. The combined effects of heating time, temperature, enzyme concentration and pH modified the digestibility value, which also depends on residence time in the stomach.

Analysis of the juice and water losses in salted and unsalted pork samples heated in water bath. Consequences for the prediction of weight loss by transfer models.

This study has analyzed the effect of different factors on variation of meat weight due to juice loss, and variation of water content of pork samples heated in a water bath. The weight loss (WL) was influenced by initial water content of raw meat which can be connected to meat pH, muscle type, and by pre-salting. WL was also influenced by sample thickness and by nature of the surrounding fluid. These effects were significant at 50°C and in thinner samples but decreased as meat temperature and sample thickness increased. WL showed no significant difference in response to prior freezing, applying a surface constraint during heating or varying meat salt content from 0.8 to 2.0%. The results were interpreted from literature knowledge on protein denaturation, contraction and, transport phenomena. Reliably predicting WL from water content variation during heating hinges on taking into account the loss of dry matter and the possible effects of meat pH, sample size or surrounding fluid.

Towards models for the prediction of beef meat quality during cooking.

Heating of beef muscles modifies the water content, the micronutrient content and the colour of beef meat. Juice expelling and loss of water soluble micronutrients were predicted by combined transfer-kinetics models. Kinetics modeling and crust formation are needed to progress toward a reliable prediction of HAAs formation. HAAs formation in uniformly heated beef meat slices was compared with the values issued from the kinetic models developed in literature in liquid systems. The models of literature were adapted to meat slices but the parameter values were different from those determined in liquid systems. Results in meat slices were confronted to the HAAs formation at the surface of bigger meat pieces subjected to air roasting conditions. The transposition of the results from the meat slices towards the bigger meat pieces was not direct because the formation of HAAs was affected by the thickening of the crust and the migration of precursors.

The effects of low salt concentrations on the mechanism of adhesion between two pieces of pork semimembranosus muscle following tumbling and cooking.

The aim of this research was to gain deeper insight into the effect of salt content on the adhesion between pieces of semimembranosus pork muscle bound by a tumbling exudate gel. Hydrophobic site number, free thiol and carbonyl content were measured in tumbling exudate and meat protein to evaluate the protein-protein interactions involved in the adhesion process. Proteins were far more oxidized in exudate than in meat, and under our experimental conditions, salt content increased protein bonding in the exudate but not in the meat. Breaking stress increased between non-salted meat and 0.8%-salted meat but did not depend on the protein physicochemical properties of the tumbling exudate. Modifying the meat surface by tumbling alone, tumbling and salting, or scarification had no effect on breaking stress. It is suggested that the break between the meat pieces occurred between the tumbling exudate and the meat surface due to weaker chemical bonds at this location.

Combined heat transfer and kinetic models to predict cooking loss during heat treatment of beef meat.

A heat transfer model was used to simulate the temperature in 3 dimensions inside the meat. This model was combined with a first-order kinetic models to predict cooking losses. Identification of the parameters of the kinetic models and first validations were performed in a water bath. Afterwards, the performance of the combined model was determined in a fan-assisted oven under different air/steam conditions. Accurate knowledge of the heat transfer coefficient values and consideration of the retraction of the meat pieces are needed for the prediction of meat temperature. This is important since the temperature at the center of the product is often used to determine the cooking time. The combined model was also able to predict cooking losses from meat pieces of different sizes and subjected to different air/steam conditions. It was found that under the studied conditions, most of the water loss comes from the juice expelled by protein denaturation and contraction and not from evaporation.

Effect of steam and lactic acid treatments on the survival of Salmonella Enteritidis and Campylobacter jejuni inoculated on chicken skin.

Campylobacteriosis and salmonellosis are the most frequently reported zoonotic infectious diseases. The present work evaluated the effectiveness of steam treatment at 100 °C for 8s, a 5% lactic acid treatment for 1 min and their combination for inactivating Salmonella Enteritidis and Campylobacter jejuni inoculated on chicken skin. The impact of each treatment on the total aerobic mesophilic bacteria and the effect of rinsing after contact with lactic acid were also evaluated. Residual bacteria were counted immediately after treatment or after seven days of storage at 4 °C. Results demonstrated the immediate efficiency of the steam and the combined treatments with reductions of approximately 6 and 5 log cfu/cm2 respectively for S. Enteritidis and C. jejuni. They also showed significant reductions (equal to or >3.2 log cfu/cm2) in the total aerobic mesophilic plate count. Lactic acid had a persistent effect on pathogen growth during storage which was significantly higher when the skin was not rinsed, reaching reductions of 3.8 log cfu/cm2 for both S. Enteritidis and C. jejuni. Only the combined treatments significantly reduced the recovery of the total aerobic mesophilic bacteria during storage. The significant reductions in both pathogens and total aerobic mesophilic bacteria on treated chicken skins are possible ways to improve the safety and shelf life of the product although high levels of indigenous non-pathogenic bacteria may be beneficial due to their protective effect against potential re-contamination of chicken skin.

Effect of marination and microwave heating on the quality of Semimembranosus and Semitendinosus muscles from Friesian mature cows.

Semimembranosus (SM) and Semitendinosus (ST) muscles from 8 mature cows were used to evaluate the effect of marination, power of microwave heating, and internal temperature of cooking on the quality of calibrated beef roasts. Four treatments, using combinations of power (182W and 654W) and temperature (60 and 80°C) were applied to marinated (10% added brine: salt, sodium lactate, lactose, and ascorbate) and control roasts from SM (15×5×3cm) and ST (10×4×3cm) muscles in a 2×2×2 factorial arrangement. Microwave cooking was heterogeneous resulting in a gradient of temperatures within the roasts. Either high or low microwave power were appropriate for cooking ST roasts, but SM roasts cooked at 654W showed higher cooking losses, and lighter and less red cooked color than 182W. Cooking to 80°C increased cooking and color losses in both muscles and decreased tenderness of SM roasts compared with 60°C. Marination can be used successfully to enhance beef tenderness of ST and SM muscles cooked in microwave.

In situ imaging highlights local structural changes during heating: the case of meat.

Understanding and monitoring deformation and water content changes in meat during cooking is of prime importance. We show the possibilities offered by nuclear magnetic resonance imaging (MRI) for the in situ dynamic measurement of deformation fields and water content mapping during beef heating from 20 to 75 °C. MRIs were acquired during heating, and image registration was used to calculate the deformation field. The temperature distribution in the sample was simulated numerically to link structural modifications and water transfer to temperature values. During heating, proton density decreases because of a magnetic susceptibility drop with temperature and water expulsion due to muscle contraction. A positive relationship was found between local cumulative deformation and water content. This new approach makes it possible to identify the deformation field and water transfer simultaneously and to trace thermal history to build heuristic models linking these parameters.

Characterization of simultaneous heat and mass transfer phenomena for water vapour condensation on a solid surface in an abiotic environment--application to bioprocesses.

The phenomenon of heat and mass transfer by condensation of water vapour from humid air involves several key concepts in aerobic bioreactors. The high performance of bioreactors results from optimised interactions between biological processes and multiphase heat and mass transfer. Indeed in various processes such as submerged fermenters and solid-state fermenters, gas/liquid transfer need to be well controlled, as it is involved at the microorganism interface and for the control of the global process. For the theoretical prediction of such phenomena, mathematical models require heat and mass transfer coefficients. To date, very few data have been validated concerning mass transfer coefficients from humid air inflows relevant to those bioprocesses. Our study focussed on the condensation process of water vapour and developed an experimental set-up and protocol to study the velocity profiles and the mass flux on a small size horizontal flat plate in controlled environmental conditions. A closed circuit wind tunnel facility was used to control the temperature, hygrometry and hydrodynamics of the flow. The temperature of the active surface was controlled and kept isothermal below the dew point to induce condensation, by the use of thermoelectricity. The experiments were performed at ambient temperature for a relative humidity between 35-65% and for a velocity of 1.0 ms⁻¹. The obtained data are analysed and compared to available theoretical calculations on condensation mass flux.

Kinetic analysis of cooking losses from beef and other animal muscles heated in a water bath--effect of sample dimensions and prior freezing and ageing.

Cooking loss kinetics were measured on cubes and parallelepipeds of beef Semimembranosus muscle ranging from 1 cm × 1 cm × 1 cm to 7 cm × 7 cm × 28 cm in size. The samples were water bath-heated at three different temperatures, i.e. 50°C, 70°C and 90°C, and for five different times. Temperatures were simulated to help interpret the results. Pre-freezing the sample, difference in ageing time, and in muscle fiber orientation had little influence on cooking losses. At longer treatment times, the effects of sample size disappeared and cooking losses depended only on the temperature. A selection of the tests was repeated on four other beef muscles and on veal, horse and lamb Semimembranosus muscle. Kinetics followed similar curves in all cases but resulted in different final water contents. The shape of the kinetics curves suggests first-order kinetics.

Dynamic MRI and thermal simulation to interpret deformation and water transfer in meat during heating.

Understanding and controlling structural and physical changes in meat during cooking is of prime importance. Nuclear magnetic resonance imaging (MRI) is a noninvasive, nondestructive tool that can be used to characterize certain properties and structures both locally and dynamically. Here we show the possibilities offered by MRI for the in situ dynamic imaging of the connective network during the cooking of meat to monitor deformations between 20 and 75 °C. A novel device was used to heat the sample in an MR imager. An MRI sequence was developed to contrast the connective tissue and the muscle fibers during heating. The temperature distribution in the sample was numerically simulated to link structural modifications and water transfer to temperature values. The contraction of myofibrillar and collagen networks was observed at 42 °C, and water began to migrate toward the interfascicular space at 40 °C. These observations are consistent with literature results obtained using destructive and/or nonlocalized methods. This new approach allows the simultaneous monitoring of local deformation and water transfer, changes in muscle structure and thermal history.

Capillary force required to detach micron-sized particles from solid surfaces--validation with bubbles circulating in water and 2 microm-diameter latex spheres.

The adhesion forces holding micron-sized particles to solid surfaces can be studied through the detachment forces developed by the transit of an air-liquid interface in a capillary. Two key variables affect the direction and magnitude of the capillary detachment force: (i) the thickness of the liquid film between the bubble and the capillary walls, and (ii) the effective angle of the triple phase contact between the particles and the interface. Variations in film thickness were calculated using a two-phase flow model. Film thickness was used to determine the time-variation of the capillary force during transit of the bubble. The curve for particle detachment was predicted from the calculated force. This curve proved to be non-linear and gave in situ information on the effective contact angle developing at the particle-bubble interface during detachment. This approach allowed an accurate determination of the detachment force. This theoretical approach was validated using latex particles 2 microm in diameter.

Synchronous front-face fluorescence spectroscopy coupled with parallel factors (PARAFAC) analysis to study the effects of cooking time on meat.

In this study, the potential of synchronous front-face fluorescence coupled with chemometrics has been investigated for the analysis of cooked meat. Bovine meat samples (thin slices of 5 cm diameter) taken from Longissimus dorsi muscle were cooked at 237 degrees C for 0, 1, 2, 5, 7, and 10 min under control conditions. Synchronous front-face fluorescence spectra were collected on meat samples in the excitation wavelength range of 250 to 550 nm using offsets (Delta lambda) of 20, 30, 40, 50, 60, 70, 80, 90, 100, 110, 120, 130, 140, 150, and 160 nm between excitation and emission wavelengths. The synchronous fluorescence landscape containing 360 spectra was analyzed using PARAFAC. The best PARAFAC model presented 2 components since core consistency values for the first 2 components were 100% and the explained variance was 67.98%. The loading profiles of 1st and 2nd components had an optimal Delta lambda of 70 and 40 nm, respectively, allowing to determine the excitation (exc.) and emission (em.) maxima wavelengths of 1st (fluorescence band at about exc.: 340 to 400/em.: 410 to 470 nm, and peak at exc.: 468/em.: 538 nm) and 2nd (exc.: 294 nm/em.: 334 nm) components. As the loading profile of the 1st component of PARAFAC was assigned to Maillard-reaction products formed during cooking, the profile of the 2nd component corresponded with the fluorescence characteristics of tryptophan residues in proteins. Loadings and scores of the PARAFAC model developed from the synchronous fluorescence spectra enabled to get information regarding the changes occurring in meat fluorophores during cooking of meat at 237 degrees C from 0 to 10 min.

Effects of steam and lactic acid treatments on inactivation of Listeria innocua surface-inoculated on chicken skins.

Effectiveness of combined steam (10 and 60 s, 70 degrees C and 98 degrees C) and chemical treatments, using concentrated solutions of lactic acid (1 and 30 min, 5% and 10% lactic acid), on the inactivation of Listeria innocua inoculated on the surface of chicken skins have been studied. Surviving bacteria on the skin were enumerated immediately after treatment, and after 7 days of storage at 4 degrees C. The most effective treatment was the combination of steam of 98 degrees C and 10% lactic acid with its immediate efficacy being mainly attributed to the applied heat treatment. However, after 7-day storage, the treatment's effectiveness was mainly due to the applied acid treatment, which prevented growth of the bacteria that survived the heat treatment. Milder treatments (70 degrees C steam, 5% lactic acid) revealed a genuine synergy between the heat and acid treatments, paving the way for an effective means of reducing bacterial load on the surface of poultry without affecting the product's "raw" appearance.