Vaishnavi Jijore
MVSc Department of Livestock Products Technology,
Mumbai Veterinary College, Mumbai
Awareness of human health when using chemical preservatives in food has increased, resulting in the use of alternative strategies for preserving food and enhancing its shelf-life. Fresh foods and minimally processed foods present a new challenge to food safety and security by inhibiting food-borne pathogens and other microbes. Processed food in the food industry are expected to be safe to consume. But, depending on the precautions taken by food handlers, foods can become microbially contaminated. It made research interest on the natural and effective preservatives. Biopreservation, is a sustainable approach to food safety and quality that uses microorganisms or their metabolites to inhibit spoilage and pathogenic bacteria, extending the shelf life of food products., (stiles et al., 1996).
As we all know that, Meat is highly desirable, nutritious and rich in protein, highly perishable. (Talukder et al., 2014). So there are some major concerns of meat preservation meat should be safe from the infectious agents, toxic chemicals and foreign objects. Food should be desirable to consumer i.e. good taste, colour and texture.(Nath et al., 2024).
TYPES
- Lactic acid Bacteria and Bacteriocins
- Bacteriophages
- Fermentates
- Natural Antimicrobials and Enzymes
Lactic acid Bacteria and Bacteriocins
Lactic acid bacteria (LAB) are a diverse group of microorganisms commonly found in a wide range of environments, including foods, the gastrointestinal and mucous membranes of humans and animals, and many other ecological niches where fermentable carbohydrates are present. In food fermentations—such as those involved in yogurt, cheese, salami, sourdough bread, and wine—LAB are the principal organisms responsible for creating desired sensory attributes, extending shelf life, and improving product safety by inhibiting spoilage and pathogenic microbes. LAB achieve bioprotection i.e. biopreservation primarily through the production of antimicrobial compounds such as lactic acid, bacteriocins (like nisin), hydrogen peroxide, and other organic acids including acetic and succinic acids. These metabolites acidify the food matrix, disrupt the membranes of competing microorganisms, and outcompete them for nutrients, collectively suppressing the growth of spoilage organisms and pathogens. This ability makes LAB the most widely used microorganisms for natural food preservation and safety enhancement. (Björkroth & Koort, 2016).
Bacteriocins are ribosomally synthesized antimicrobial peptides produced by lactic acid bacteria (LAB), exhibiting broad-spectrum antibacterial activity that makes them critical in food fermentation and preservation. These compounds enhance food safety by inhibiting pathogens like Listeria monocytogenes and spoilage organisms while improving sensory qualities in dairy products, fermented meats, and vegetables. Rapidly degraded by human digestive proteases, they pose no risk to gut microbiota balance. First identified in 1925 by André Gratia, bacteriocins such as Nisin – effective against Gram-positive bacteria including Staphylococcus aureus and Listeria monocytogenes serve as sustainable alternatives to antibiotics and synthetic preservatives, aligning with consumer demand for natural food additives. Bacteriocins are employed in dairy products, canned foods, and processed meats for extended shelf life. (Joerger et al., 2003).
Bacteriocins are antimicrobial peptides synthesized by bacteria that exhibit diverse mechanisms of action, primarily targeting the membranes of susceptible bacteria. Typically, bacteriocins function by forming pores in the bacterial cell membrane, resulting in the efflux of ions and molecules and ultimately causing cell lysis.
Class I Bacteriocins (Lantibiotics):
Lantibiotics, such as nisin, create pores in the membrane through a wedge-like mechanism. They often interact with lipid II, an essential component in peptidoglycan synthesis, thereby disrupting both cell wall formation and membrane integrity.
Class II Bacteriocins:
These bacteriocins form pores using models such as barrel stave or carpet-like mechanisms. Their activity frequently depends on binding to specific receptors on the cell membrane, such as components of the mannose phosphotransferase system in the case of pediocins. The primary receptors for bacteriocins are generally found on the bacterial cell membrane, not in the cytoplasm. For example, lipid II serves as a key receptor for lantibiotics, while other bacteriocins may target specific membrane-associated proteins.
Methods of Bacteriocin Application in Meat and Meat Products
1. Inoculation with Bacteriocin-Producing Lactic Acid Bacteria (LAB). LAB can be introduced as starter or protective cultures during the production of fermented meats. These bacteria produce bacteriocins in situ, helping to control spoilage and pathogenic microorganisms throughout fermentation and storage.
2. Addition of Purified or Semi-Purified Bacteriocins. Purified or partially purified bacteriocins can be directly added to meat products as natural preservatives. This approach is particularly useful when live LAB cultures are not effective or suitable for the specific meat matrix.
3. Use of Previously Fermented Meat with Bacteriocin-Producing Strains. Incorporating meat that has been previously fermented with bacteriocin-producing LAB can introduce both the bacteria and their antimicrobial peptides into new batches, enhancing preservation and safety.
4. Incorporation into Edible Films and Coatings. Bacteriocins can be embedded in edible cellulosic or other biopolymer-based films and coatings, which are applied to the surface of meat products. This method provides a controlled release of antimicrobial agents, extending shelf life and inhibiting surface contamination.
5. Commercial Preparations and Multi-Hurdle Strategies. Commercial products containing crude or semi-purified bacteriocins (often combined with organic acids) are used in meat processing, especially for products like salami and cured meats. These are frequently integrated with other preservation techniques such as curing, drying, and smoking to enhance overall efficacy.,(Thomas et al., 2000).
Nisin is currently the only bacteriocin approved by the FAO/WHO (since 1969) for use in meat and meat products. (Devlieghere, et al., 2004). It is widely studied and applied due to its effectiveness against Gram-positive pathogens such as Listeria monocytogenes and Staphylococcus aureus. Other bacteriocins, such as pediocin, enterocin AS-48, enterocin A and B, and leucocin A., (Saeed et al., 2018), have demonstrated strong antimicrobial activity (notably against Listeria), but are not yet approved for commercial use in meat products. The effectiveness of bacteriocins can be influenced by factors such as meat matrix composition, pH, and the presence of competing microorganisms. To date, nisin, produced by Lactococcus lactis subsp. lactis, is the only bacteriocin that has achieved widespread commercial approval and use as a food preservative, registered as E234 (Nisaplin) and endorsed by regulatory agencies such as FAO/WHO. Pediocin PA-1, produced by Pediococcus acidilactici, has also been commercially produced and is available in products like ALTATM 2341, but it has not yet received broad regulatory approval for use in foods in many countries. Other bacteriocins such as subtilin, cerein, and plantaricin have been isolated and characterized from various bacteriocin-producing strains, but they have not yet reached commercial status or widespread regulatory acceptance.
The application of bacteriocin-producing cultures, such as LAB and Pediococcus acidilactici, has demonstrated effectiveness in controlling pathogens like Listeria monocytogenes in vacuum-packed beef, especially when combined with modified atmosphere packaging (MAP) using high concentrations of CO₂. Bio-preservation techniques using these bacteriocins can inhibit a range of spoilage and pathogenic microorganisms, including L. monocytogenes, E. coli O157:H7, Salmonella spp., and Pseudomonas fluorescens.
FERMENTATION
Fermentation is a metabolic process in which microorganisms like yeast and bacteria convert sugars into acids (e.g., lactic acid), gases, or alcohol. This process relies on the growth of microbes in foods, which may occur naturally or through the intentional addition of starter cultures. Lactic acid bacteria (LAB) are the primary microorganisms involved, producing organic acids and other bioactive compounds that act as natural preservatives by inhibiting spoilage organisms and pathogens.
Fermentation of meat using protective cultures
Selection Criteria for Protective Cultures: Must be Generally Recognized As Safe for human consumption. Capable of synthesizing inhibitory compounds (e.g., bacteriocins) within the meat matrix. Minimize alterations to flavor, texture, and aroma of the final product. Generate sufficient acid for preservation without over-acidification. Avoid excessive protein degradation to maintain meat texture. Prevent unwanted gas pockets or texture defects. Starter Cultures in Meat Fermentation: Starter cultures are microbial formulations (active or dormant) designed to initiate and guide fermentation by performing specific metabolic roles in the meat, such as acid production, flavor development, and pathogen inhibition. Meat products such as pepperoni, summer sausage, dry sausages, bologna, and salami are commonly fermented using starter cultures like Pediococcus cerevisiae (for pepperoni, summer sausage, dry sausages, and bologna), Lactobacillus plantarum (for pepperoni and summer sausage), and Micrococcus spp. (for salami) to ensure controlled fermentation, flavor development, and microbial safety. (Hammes et al., 1990). The general process for preparing fermented meat products involves preparing the meat emulsion, stuffing it into casings, adding starter cultures, fermenting through lactic acid production, followed by cooking or drying to obtain the final fermented meat product.
Effect of Culture on Meat and Meat Products: Fermented Sausages: Lactic acid bacteria (LAB) play a crucial role in fermented sausages by fermenting added sugars and producing organic acids, which lower the pH. This acidification inhibits the growth of spoilage and pathogenic bacteria, making the product safer and extending its shelf-life. LAB also contribute to flavor and texture development in these products.
Raw Ham and Ready-to-Eat Meats: Adding psychrotrophic LAB to these products, even in the presence of oxygen, helps suppress harmful bacteria like Listeria monocytogenes, especially under vacuum packaging. This biopreservation effect enhances the safety of ready-to-eat meats during refrigerated storage.
Semi-Processed Raw Meat: Specific LAB strains can improve the shelf-life and freshness of products like bacon and sausages by producing antimicrobial substances (such as organic acids and bacteriocins). These inhibit spoilage and pathogenic microorganisms, helping maintain product quality during storage.
Salted Semi-Processed Raw Meat: Starter cultures like Pediococcus species ferment sugars to produce acids in salted meats. This acidification prevents the growth of dangerous bacteria such as Clostridium botulinum, thereby extending shelf-life and ensuring product safety.,(Lucke et al., 1998).
Bacteriophage
Bacteriophages are viruses that specifically infect and replicate within bacteria by hijacking the bacterial biosynthetic machinery. They are harmless to humans, animals, and plants, targeting only their specific bacterial hosts. Application of Bacteriophage in Meat and Meat Products: Bacteriophages have been approved for use in the meat industry as a natural and highly specific antimicrobial intervention. The FDA has permitted the safe application of a lytic bacteriophage preparation as an anti-listerial agent in ready-to-eat (RTE) meat and poultry products. This preparation is typically sprayed directly onto the surface of meat products at a concentration of 0.1 ppm, with a dosage of 1 milliliter per 500 cm² of surface area before packaging. The bacteriophages remain inactive unless they encounter their specific target, such as Listeria monocytogenes, at which point they infect and destroy the bacteria, thereby enhancing food safety without affecting other organisms or the sensory qualities of the food., (Kathy walker et al., 2006).
Endolysin: What are Endolysins?
Endolysins, also known as lysins, are hydrolytic enzymes produced by bacteriophages (phages). During the final stage of the phage lytic cycle, these enzymes cleave the peptidoglycan layer of the bacterial cell wall, causing cell lysis and releasing new phage particles. When applied externally, especially to Gram-positive bacteria, endolysins can degrade the bacterial cell wall, making them effective antibacterial agents., (Jhamb and Spardha et al., 2014). Application of Endolysin: Endolysins have a broad killing spectrum because they cleave specific linkages in the peptidoglycan of bacterial membranes. They are highly potent, exhibiting antimicrobial activity at nanogram levels. This makes them promising alternatives to traditional antibiotics, especially against drug-resistant bacteria. However, the production cost of endolysins is high, mainly due to the use of genetically modified organisms in their manufacture.
Natural Antimicrobials and Enzymes
Natural antimicrobials are derived from: Plants: Herbs, spices, and essential oils (e.g., oregano, thyme, cinnamon, clove, rosemary) are rich in bioactive compounds like phenolics, terpenes, and aldehydes. These compounds exhibit strong antimicrobial and antioxidant properties, making them effective against a wide range of spoilage and pathogenic microorganisms, including Salmonella, Listeria monocytogenes, Escherichia coli, and Staphylococcus aureus. They also inhibit fungal growth and mycotoxin production. Animals: Lysozyme (from egg white), lactoferrin (from milk), and chitosan (from shrimp shells) are commonly used animal-derived antimicrobials. Lysozyme disrupts bacterial cell walls, while lactoferrin binds iron, making it unavailable to microbes and thus inhibiting their growth. Microorganisms: Bacteriocins (such as nisin, pediocin, and reuterin) produced by lactic acid bacteria inhibit closely related bacteria and some foodborne pathogens. Other microbial-derived antimicrobials include organic acids (lactic, acetic, citric) and enzymes that disrupt bacterial biofilms and cell walls.
Plant-derived antimicrobials: Essential oils and extracts from herbs and spices are widely used in meat products to control spoilage and pathogenic bacteria, reduce oxidative deterioration, and extend shelf life. For example, clove and cinnamon essential oils are noted for their effectiveness in reducing bacterial load and oxidative rancidity in meat. Animal-derived antimicrobials: Lysozyme and lactoferrin are incorporated into food systems to target specific bacteria, enhancing safety and shelf life. Chitosan is used as a coating or additive to inhibit microbial growth. Microbial-derived antimicrobials: Bacteriocins are used in fermented meat products and as preservatives to inhibit pathogens like Listeria monocytogenes. Organic acids and their salts are added to increase acidity and prevent microbial growth. Benefits of Natural Antimicrobials and Enzymes – Extend shelf life of meat and meat products, reduce transmission of foodborne pathogens, minimize the need for synthetic chemical preservatives, effectively control resistant organisms, such as L. monocytogenes.,( rameez et.al., 2023).
Conclusion
The use of natural or controlled microbiota, along with antimicrobial compounds, plays a vital role in extending the shelf life and enhancing the food safety of meat and meat products. These biological preservation methods, when combined with other preservation strategies, can be effectively integrated into hurdle technology to provide a multi-layered approach against spoilage and pathogenic microorganisms. This integrated preservation approach not only improves product quality and safety but also reduces reliance on synthetic chemicals, meeting consumer demand for natural and safe food products.