Monika Gibis

This narrative review aims to provide a comprehensive overview of meat color in vacuum-packaged beef, focusing on intrinsic and extrinsic discoloration mechanisms throughout the whole beef production process. The review describes fundamental knowledge about wet-aging, vacuum-packaging, meat color, consumer acceptance, and postmortem metabolism. It also explains the intrinsic discoloration mechanisms, involving various chemical and biochemical oxidizing processes of myoglobin. These mechanisms are also influenced by muscle type and composition. Further, extrinsic discoloration mechanisms. These mechanisms include microbiology, slaughtering, vacuum packaging and its application, and storage. This review summarizes all fundamentals necessary to understand the biochemistry of meat color and provides a comprehensive overview of possible discoloration mechanisms and causes in beef. The knowledge acquired is applied to the vacuum-packaged beef production chain and offers valuable insights for developing effective prevention strategies. Important findings are that the extrinsic factors are currently easier to influence than intrinsic factors. There are knowledge gaps in relation to discoloration and mitochondrial metabolism, reducing systems of meat, and oxygen concentration in packaging. Also, the influence of the microbiome on discoloration and postmortem metabolism of the meat and the influence of the living conditions and feed on color-stabilizing intrinsic factors of the meat should be further investigated.

Rapeseed (Brassica napus L.) press cake, a side stream of oil production, has gained in-terest as a source of functional protein. While press cake processing, protein extraction, and drying have been studied at laboratory scale, their behavior at industry-relevant scale needs further investigation, and a systematic comparison of pilot-scale spray and freeze drying of rapeseed protein concentrate (RPC) is lacking. This study therefore compared spray- and freeze-dried RPC (SD-RPC, FD-RPC) produced at pilot scale, re-garding their composition, color, secondary structure (FTIR), molecular weight distri-bution (SDS-PAGE), particle size, zeta potential, solubility, and techno-functional properties. Results showed that the drying method did not significantly influence pro-tein chemistry, including protein composition, secondary structure, and isoelectric point (~pH 3.5). Physical properties, in contrast, differed significantly: freeze drying resulted in coarser, bimodally distributed particles with lower residual moisture, while spray drying produced finer, monomodal particles with a lighter color. These differences were reflected in the techno-functional behavior, where FD-RPC showed significantly higher water/oil holding and emulsion capacity, while emulsion stability, foaming, and least gelation concentration were comparable. Spray drying proved a feasible, scalable al-ternative, yielding a concentrate with comparable protein chemistry yet distinct physical functionality, promising for emulsion- and gel-based food applications.

Intrinsic factors of vacuum-packaged, discolored beef samples found in the early stages of wet aging at the slaughterhouse were measured and compared to a control group. The aim was to identify possible differences in intrinsic factors that could explain the discolorations. L *, a *, b * values, and myoglobin redox state levels were measured to characterize the extent of discoloration and the oxidation state of myoglobin. pH value, redox potential, total reducing activity, and the concentrations of lactate, α -tocopherol, β -carotene, and NAD ⁺ /NADH were analyzed to identify differences. Significant ( p < 0.05) differences and correlations were observed in color values and myoglobin redox states between the control and discolored samples, e.g., a * = 11.21 (control) and 9.42 (discolored); metmyoglobin = 0.79 (control) and 1.01 (discolored). Except for directly color-related parameters, only a significant difference in lactate concentration was observed (3.90 mg/g (control) and 5.60 mg/g (discolored) without a significant change in pH [5.60 (control) and 5.61 (discolored)]. Since lactate is reported to stabilize the color of meat rather than causing discoloration, the cause of the discoloration might be attributed to a multifactorial interaction of intrinsic parameters, or extrinsic parameters during the slaughtering, deboning, cutting, and packaging process. Although the cause of the discoloration could not be identified, this study displays important data on the interactions between intrinsic parameters. Therefore, this study can be considered an exploratory investigation that lays the foundation for further research to identify the causes of discoloration.

International trade in egg products has increased in recent decades to meet the rising demands of a global population, the food industry, and consumers. Egg white is a rich source of proteins and peptides suitable for various food applications. Processing egg whites is important in the food industry. This review thoroughly examines different aspects of egg white technology, including the definition of egg white, the natural microflora of eggs, and potential contaminants that may be present during processing. The impact of raw materials on the quality and features of egg products is also discussed, along with traditional and modern processing technologies regarding their applicability and efficiency. The study shows recent advancements and innovative approaches that could enhance egg white processing. Additionally, the fermentation of egg whites is explored as a promising method to modify their functional properties and produce bioactive compounds. The review shows the health benefits and significance of bioactive peptides derived from egg white in the development of functional foods. Overall, this review provides a comprehensive overview of current research in egg white processing, demonstrating how this valuable raw material can be utilized to create innovative products with enhanced nutritional and functional properties.

This study investigates the use of a homopolysaccharide (HoPS)-producing Latilactobacillus sakei strain for the production of protein-enriched plant-based yoghurt analogues based on coconut milk. Formulations varied in added sucrose (2.5% or 5.0% w/w), pea protein isolate (PPI; 0–5.0% w/w), and tapioca starch (0%, 1.5% w/w), and were fermented with either a HoPS-producing strain (L. sakei 1.411), or a non-exopolysaccharide (EPS)-producing control strain (L. sakei 1.2037) with very similar acidification kinetics. Microbial growth and pH were monitored, HoPS content was determined via HPLC, and both firmness and syneresis were assessed during 5 days of storage at 4 °C. EPS yields were significantly higher (p < 0.05) in samples with 5.0% w/w added sucrose compared to those with 2.5% w/w. Fermentation with L. sakei 1.411 generally resulted in firmer gels (p < 0.05) and reduced syneresis (p < 0.05) compared to L. sakei 1.2307 and the enhanced viscosity (sample thickness) was also observed in a sensory analysis. Samples containing starch and 5.0% w/w PPI showed the highest firmness-related values. These findings demonstrate the potential of in situ HoPS production to improve the texture and stability of protein-enriched coconut-based yoghurt analogues. It highlights the importance of matrix formulation, strain selection and process control, which all contribute to the final product quality.

Vacuum‐packaging technologies have been developed over recent decades to extend the shelf‐life of beef and to provide consumers with standardized, high‐quality products. However, muscles stored under vacuum can still undergo discoloration, likely when animals are exposed to adverse pre‐mortem weather conditions (high air humidity and/or large temperature fluctuations). Even if microbial activity is assumed to play a role in discoloration processes, relationships between bacterial populations and beef discoloration remain largely unexplored. This manuscript aims to identify potential microbiological germs related to discoloration in vacuum‐packaged beef. To assess the microbiological basis of beef discoloration, total viable and anaerobic counts were quantified and bacterial identification using MALDI‐TOF MS was performed in both discolored ( n = 12) and control ( n = 12) meat groups. The samples were collected at approximately 5–8 days post‐mortem from the storage facility of a German slaughterhouse. Unexpectedly, the pH values in the control samples were consistently higher than those in the discolored samples, however a significant color difference was found ( p  < 0.05). Discolored muscles appeared to have higher lightness ( L *) values, but had lower redness ( a *) and overall color intensity ( h _a/b ) compared to the control samples, which can also be associated to higher superficial metmyoglobin formation. Principal component analysis (PCA) and network plot were performed using eight different variables of the data matrix. Both statistical tools confirmed that there were differences between discolored and control groups when measured at both test points. It seemed that the microbial activity in both groups of samples could not entirely explain the discoloration processes happening during beef aging in vacuum‐packages.

The influence of a 1% oxygen atmosphere on the color stability of modified atmosphere packaged beef was investigated. Beef silverside slices were packed under 1%, 20%, and 70% oxygen atmospheres and stored at 2 °C for 14 days. Color and reflection data were measured non-invasively. The L*a*b* values were analyzed, the color difference ΔE₂₀₀₀, and the levels of myoglobin (Mb), deoxy-(DMb), oxy-(OMb), and metmyoglobin (MMb) were calculated. The 1% oxygen atmosphere resulted in a rapid MMb formation from 0.63 (day 0) to 1.27 (day 8) (p < 0.05). The other samples showed slight increases from 0.65 to 0.80 MMb (20%) and 0.65 to 0.79 MMb (70%). On day 10, the 20% oxygen sample showed an increased MMb formation (1.33 MMb). The 70% atmosphere resulted in a final value of 0.91 MMb after 14 days. These results show that an oxygen content of 1% accelerates the formation of MMb at an early stage. A higher oxygen content in the packaging delays MMb development through OMb formation, which masks MMb creation, to a certain extent. Measuring the packaged meat pieces over a 14-day storage period provides detailed insights into the development of Mb formation and critical points during storage.