Journal of Food: Microbiology, Safety & Hygiene
Open Access

Anti-Salmonella Activity and Protein Stability of Egg White

Kyoyuki Shang^{* *}Correspondence: Kyoyuki Shang, Department of Food Science and Food Microbiology, University of Guelph, Guelph, Canada, Email:

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Description

Egg white, primarily composed of water and proteins, is a vital component of avian biology and has garnered significant attention in food science and nutrition. Known for its versatility in culinary applications, egg white also possesses interesting biochemical properties, including its stability and antimicrobial activities, particularly against pathogens like Salmonella. This article delves into the protein stability of egg white and its potential anti-Salmonella activity, highlighting the underlying mechanisms and implications for food safety.

Composition of egg white

Egg white, or albumen, constitutes approximately 60% of the total egg weight. It is primarily made up of water (about 90%) and proteins (about 10%), with the most notable proteins being ovalbumin, ovotransferrin, ovomucoid, and lysozyme. These proteins serve various functions, including providing nutrition for the developing embryo and protecting against microbial invasion.

Major proteins in egg white

Ovalbumin: The most abundant protein, comprising about 54% of the total protein content. It serves as a storage protein and is also involved in the defense against pathogens.

Ovotransferrin: This glycoprotein functions primarily as an iron- binding protein, inhibiting the growth of bacteria that require iron for survival, including Salmonella.

Ovomucoid: A major allergen, ovomucoid is a trypsin inhibitor that plays a role in the protease inhibition, contributing to the overall stability of the egg white proteins.

Lysozyme: An enzyme that hydrolyzes bacterial cell walls, lysozyme exhibits significant antimicrobial properties, making it a key player in the egg’s defense against bacterial contamination.

Protein sability in egg white

The stability of egg white proteins is important for maintaining their functional properties during storage and processing. Factors influencing protein stability include pH, temperature, and ionic strength. Understanding these factors is vital for ensuring the safety and quality of egg white in food applications.

pH and temperature: Egg white proteins are generally stable at a neutral pH (around 7.0), but can undergo denaturation at extremes of pH. The denaturation process involves the unfolding of protein structures, which can lead to aggregation and loss of functionality. Additionally, high temperatures can induce thermal denaturation, affecting the solubility and functional properties of the proteins.

Ionic strength: The presence of salts can stabilize proteins by shielding electrostatic interactions that promote aggregation. For instance, Sodium Chloride (NaCl) can enhance the solubility of egg white proteins, thereby maintaining their functionality during food processing.

Effects of storage: Over time, egg white proteins can undergo changes in structure and solubility due to oxidative stress and microbial contamination. Storage conditions, such as refrigeration and packaging, play an important role in preserving protein stability. Studies have shown that vacuum packaging and low temperatures significantly extend the shelf life of liquid egg products by reducing microbial load and slowing protein degradation.

Anti-salmonella activity: Salmonella spp. are a leading cause of foodborne illness globally, often associated with undercooked or contaminated eggs. The presence of antimicrobial components in egg white offers a natural defense mechanism against these pathogens.

Mechanisms of action

Lysozyme activity: Lysozyme's ability to hydrolyze the peptidoglycan layer of bacterial cell walls is one of the primary mechanisms by which egg white exhibits antimicrobial properties. This enzyme can effectively inhibit the growth of Salmonella by compromising the integrity of the bacterial cell, leading to lysis.

Ovotransferrin’s iron sequestration: By binding iron, ovotransferrin deprives Salmonella of an essential nutrient, inhibiting its growth and proliferation. Iron is a critical factor for many bacterial pathogens, and its unavailability can significantly reduce their virulence.

pH influence: The natural pH of egg white (around 7.6) can also inhibit the growth of Salmonella. When egg white is subjected to processing, such as pasteurization, the pH can be altered, further enhancing its antimicrobial efficacy.

Synergistic effects: The combined action of various proteins in egg white can produce a synergistic effect against Salmonella. For example, while lysozyme disrupts bacterial cell walls, ovotransferrin's iron-binding capacity limits bacterial growth, creating a multifaceted defense strategy.

Implications for food safety: The anti-Salmonella properties of egg white proteins have important implications for food safety, particularly in the poultry industry. Understanding these mechanisms can help develop strategies to mitigate the risk of contamination in egg products.

Pasteurization: Pasteurization is an essential control point in reducing microbial load in egg products. The process not only kills pathogenic bacteria but also preserves the functional properties of egg white proteins, making them safe for consumption while maintaining their nutritional benefits.

Functional food development: The unique properties of egg white proteins can be harnessed in the development of functional foods. By incorporating egg white into products designed to be safe from microbial contamination, food manufacturers can enhance the safety and nutritional profile of their offerings.

Conclusion

Egg white is a fascinating subject of study in the fields of food science and microbiology. Its unique protein composition, stability under various conditions, and potent anti-Salmonella activity present numerous opportunities for enhancing food safety and quality. As research continues to uncover the intricacies of egg white proteins, their applications in food technology, preservation, and functional food development will likely expand, contributing to safer and more nutritious food products. Understanding these properties is crucial for mitigating the risks associated with Salmonella and promoting public health through effective food safety practices.