Recent approaches in food bio-preservation - a review (2024)

Abstract

Bio-preservation is a technique of extending the shelf life of food by using natural or controlled microbiota or antimicrobials. The fermentation products as well as beneficial bacteria are generally selected in this process to control spoilage and render pathogen inactive. The special interest organism or central organism used for this purpose is lactic acid bacteria (LAB) and their metabolites. They are capable to exhibit antimicrobial properties and helpful in imparting unique flavour and texture to the food products. The major compounds produced by LAB are bacteriocin, organic acids and hydrogen peroxide. Bacteriocin is peptides or proteins with antimicrobial activity. On the basis of size, structure and post-translational modification, bacteriocin is divided into four different classes. Due to non-toxic, non-immunogenic, thermo-resistance characteristics and broad bactericidal activity, LAB bacteriocins are considered good bio-preservative agents. The most common LAB bactriocin is nisin which has wider applications in food industry and has been Food and Drug Administration (FDA) approved. Nisin and other bacteriocin are being used in vegetables products, dairy and meat industries. Apart from LAB metabolites, bacteriophages and endolysins has promising role in food processing, preservation and safety. Bacteriocins and endolysins are more suitable for DNA shuffling and protein engineering to generate highly potent variants with expanded activity spectrum. Genetically modified bacteriophages may also be helpful in bio-preservation, however; their safety issues must be addressed properly before selection as bio-preservative agent.

Keywords: Bacteriocins, Bacteriophages, Bio-preservation, Endolysins, Lactic acid bacteria

Introduction

The foods of animal origin are highly perishable due to high nutritional content, moisture and neutral pH. These foods require proper preservation to maintain quality and safety. Failing which leads to human illnesses and disease outbreaks. These food borne illnesses are serious and costly public health concern worldwide. So to maintain the quality and safety of foods various measures are generally adopted in food industry i.e. good manufacturing practices, good hygienic practices tec. But preservation of food by a suitable means is the key of food quality and safety. There are number of preservation techniques started from low temperature preservation like refrigeration, freezing etc. and thermal preservation techniques like pasteurization, sterilization and preservation using certain chemicals. Now a day modern preservation techniques like bio-preservation, irradiation and hurdle technologies are also common. In traditional preservation techniques food alters their status and loss some nutrients. So the modern techniques are more suitable to achieve the safety and quality of foods. It is also relevant in today world due to globalization of food market, introduction of novel foods, innovations of new technologies, demand of minimally processed products with ready–to-eat quality and longer shelf life. Among all the preservation techniques adopted now bio-preservation is more reliable from ‘farm to fork’ concept. It is capable to enhance shelf life with great quality, hygienic status with minimal nutritional and organoleptic losses.

Bio-preservation is a technique of food preservation in which antimicrobial potential of naturally occurring organisms and their metabolites are exploited. It is capable to harmonize and rationale the necessary safety standards with traditional means of preservation and modern demand of the food safety and quality. The bio-preservation techniques of various foods are mainly relying on the quality of biological antimicrobial systems such as lactic acid bacteria (LAB) and/or their bacteriocins, bacteriophages and bacteriophage-encoded enzymes. They are widely used in food industry to get a typical texture and flavour of the food products. They are helpful in maintaining the quality and safety of foods and are common bio-preservatives in industrialized world.

Use of bacteriocins in food systems

The bacteriocins in general have broad spectrum activity against number of micro-organisms. The application of bacteriocins, particularly nisin, in food systems is influenced by inadequate physical conditions and chemical composition of food including pH, temperature, nutrients, etc. It is also affected by spontaneous loss in production capacity, inactivation by phage of producing strain and antagonism effect of other microorganisms in foods. The negative factors in its effectivity include resistance against certain pathogens, biological activity interference by certain environmental conditions, higher retention of bacteriocin molecules like fat by food system components, inactivation by other additives, slower diffusion and solubility and/or irregular distribution of bacteriocin molecules in the meat matrix. The pre-requisites for use of bacteriocins in food are its production from GRAS micro-organisms, high specific activity of bacteriocins, thermostability, capability to enhance quality and flavour. Bacteriocins must be safe to human health and bio-preservation must fulfill the GRAS regulations. The common bacteriocin named nisin was first time used in 50´s to inhibit the outgrowth of Clostridiumtyrobutyricum responsible for late cheese blowing. However, the major role of bacteriocin is in inhibition of pathogenic and spoilage bacteria during food processing. Nisin has an immediate pH dependent bactericidal effect and it is further increases with decrease in pH values (Salem, 2012). The bactericidal effect is obtained by the effect of Lactobacillus acidophilus growth. Thus it can be interpreted that nisin and L. acidophilus is more effective together as compared to the single use.

The commonly used bacteriocins in foods like dairy, meat and vegetable products are lantibiotics nisin and lacticin, pediocin-like bacteriocins and, enterocin AS-48 etc. in foods bacteriocins can be applied in three forms i.e. in situ production by starter or protective cultures, as an ingredient of fermentation of a bacteriocinogenic strain and as an additive in a semi- or purified preparation. Among all In situ production is considered cost-effective. Nisin-producing dairy starters are generally designed to specifically inhibit Staphylococcus aureus in acid-coagulated cheeses and C. tyrobutyricum in semi-hard cheeses (Rilla et al., 2003, 2004). Whereas, protective cultures is mainly used to enhance the hygienic quality of raw meat and fish products and do not contribute to sensory attributes of food (Devlieghere et al., 2004). The use of bacteriocins as ingredients or additives requires low-cost food-grade media such as lacticin 3147 and the enterocin AS-48 can best produced in media containing whey (Ananou et al., 2008). It is because whey as a substrate is an attractive option of recycles a by-side product of the dairy industry. Besides bio-preservation bacteriocins have been shown to accelerate cheese ripening by promoting the release of intracellular enzymes to the cheese matrix. Some volatile compounds are responsible for sensory attributes of the matured cheese. Bacteriocins also ensures hom*ogenous fermented products (Ryan et al., 2001) and bacteriocins based food grade markers (immunity proteins) offer the possibility to replace antibiotic selective markers for genetic engineering of food-related bacteria (Brede et al., 2007). The list of commonly occurring bacteriocins and their possible uses are enumerated in Table 3.

A new bacteriocin named sonorensin belongs to heterocycloanthracin subfamily of bacteriocins is found effective against both active and non-multiplying cells of gram +ve as well as gram –ve bacteria. It is showing marked inhibition against biofilm of Staphylococcus aureus. The growth inhibition property of sonorensin is due to increased membrane permeability. Low Density Polyethylene (LDPE) film coated with sonorensin is proved to be effectively control growth of spoilage bacteria like Listeria monocytogenes and Staphylococcus aureus (Chopra et al., 2015). It may be suggested as good alternative to current antibiotics and biopreservative mean for chicken meat and tomato samples.

Bacteriophages

Bacteriophages or phages are most abundantly found microorganisms on earth and wide spreaded on foods of various origins (Brüssow and Kutter, 2005). They are viruses that specifically infect and multiply in bacteria and are usually harmless to humans, animals, and plants. Most of the bacteriophages are belong to the Caudovirales order and conatins icosahedral head and a double-stranded 179 DNA tail.

Based on tail structures bacteriophages can be classified under three families: Myoviridae with contractile tail, Siphoviridae contains long non contractile tail and Podoviridae family having extremely short tail. Although some of the other bacteriophages are cubic, filamentous or pleomorphic phages with dsDNA, single-stranded DNA, double-stranded RNA or single-stranded RNA (Ackermann, 2007). They may further be classified as virulent and temperate depending on their life cycle. Virulent are generally following the lytic life cycle while temperate enters in lysogenic cycle by inserting their DNA into the bacterial chromosome (prophage). Virulent bacteriophages are capable to lyse the host bacterium and exerted antimicrobial activity (Sulakvelidze and Kutter, 2005; Hanlon, 2007).

Utilization of bacteriophages in food system

Bacteriophages can suitably be utilized in prevention or inhibition of colonization, control of diseases in livestock through phage therapy, decontamination of carcasses and other raw products such as fresh fruit and vegetables, and to disinfect equipment and contact surfaces by phage bio-sanitation and enhance the shelf life of manufactured foods by phage bio-control. Bacteriophages can be successfully utilized for reduction of pathogen carriage in livestock farming and after slaughter or milking. Bacteriophages are effective against Salmonella (Fiorentin et al., 2005) and Campylobacter (Atterbury et al., 2005) in chicken and pathogenic E. coli (Raya et al., 2006) in ruminants. To achieve biosanitation reduction in biofilm can be obtained (Azeredo and Sutherland, 2008) by reducing or eradication of S. aureus nasal or skin colonisation in food handlers (Mann, 2008).

In bio-preservation, bacteriophages can work symbiotically with fermentation organisms during fermentation. It is quite effective method in preparation of food processing’s and reduces effectively the like Salmonella in cheddar production (Modi et al., 2001), S. aureus growth in curd manufacturing (García et al., 2007; 2009) and complete eradication of Listeria monocytogenes during ripening, and storage of acid coagulated and semi-hard cheeses (Carlton et al., 2005) and inhibition of Enterobacter sakazakii in reconstituted infant formula milk (Kim et al., 2007) and Salmonella typhimurium on chicken frankfurters (Whichard et al., 2003).

Some of the commercially available phage preparations have got approval from FDA like Listex and LMP 102 for ready-to-eat meat, anti-E. coli and anti-Salmonella phage-based product to treat live animals prior to slaughtering.

It also helps in detection of food borne pathogens in which phage specificity and the efficacy of host recognition is generally exploited.

Endolysins

Endolysins are also called phage lysins which are phage-encoded peptidoglycan hydrolases employed by the majority of bacteriophages to enzymatically degrade the peptidoglycan layer of the host bacterium. Bacteriophages are utilizing the endolysins at the end of their replication cycle to degrade the peptidoglycan of the bacterial host.

Endolysins are good antimicrobials because of absence of an outer membrane in the Gram-positive bacterial cell wall and its easy accessibility to peptidoglycan (Young et al., 2005). Structurally most of the endolysins lack secretory signals and their access to peptidoglycan inside the cell is dependent on small hydrophobic proteins, named holins. Endolysins are mostly having narrow spectrum lytic activity and often restricted to phage host bacterial activity from which they are originally derived. However, some exceptions are also existed like Enterococcal phage lysin whch are capable to lyse enterococci as well as Streptococcus pyogenes, group B streptococci and S. aureus (Yoong et al., 2004).

Role of Endolysins in food system

The role of endolysins in food bio-preservation is still in infancy. But there are number of endolysins are isolated to work against several zoonotic and food-borne pathogens. The good thing in this regard is the non-existence of resistance against endolysins till date. It is suggested by several scientists now that transgenic cows expressing endolysins have less chances of mastitis and S. aureus milk contamination (Donovan et al., 2006). Similarly Staphylococcal endolysin is found capable to reduce S. aureus biofilms (Sass and Bierbaum, 2007). Endolysins are also having suggested roles in dairy processing particularly purified endolysins are found to destroy S. aureus in pasteurized milk.

Reports suggested that recombinant LAB are capable to release active Listeria endolysin but their antagonistic activity in milk still requires authentication (Turner et al., 2007). It has also been indicated in food safety and has specificity against CBDs.

Conclusion

Overall bio-preservation of food by bacteriocins, bacteriophages and endolysins has promising role in food processing, preservation and food safety. Bacteriocins and endolysins are believes to have more suitability for DNA shuffling and protein engineering to generate highly potent variants with expanded activity spectrum. Genetically modified bacteriophages may also be helpful in bio-preservation but their safety issues must be addressed properly before selection as bio-preservative agent. The bacteriocins may be a good hurdle agent and successfully can be incorporated into packaging films and combined with modified atmosphere packaging (MAP). Similarly phages and endolysins have been successfully combined with nisin and high hydrostatic pressure enhances endolysin activity Bacteriophages and endolysins has also been advocated as good disinfectants in food environments, including food handlers, but delivery strategies have to be implemented. So to attain bio-preservation in most holistic manner it is mandatory to prove the freeness from resistance particularly of bacteriocins and bacteriophages. However, endolysisn has no such problem indicated till date. But phages mutate at frequencies significantly higher than that of bacteria. But new phage selection might easily overcome bacterial resistance. Lysogeny process is quite deteriorative because of it bacterial resistant becomes superinfection. Thus temperate phages should always be avoided. But on revolution in genetic technology and advancement in molecular techniques it is expected that bacteriocins, bacteriophages and endolysins will prove the future bio-preservative.

References