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Biopreservation: Re-discovering a 'Forgotten' Concept
Age-old Wisdom - Neglected

Fermentation is one of the first food preservation techniques known to man. Since ancient times, it has been observed that the activity of microorganisms on certain fresh foods improved their taste, texture and aroma at the same time making the food last longer. However, with the advent of novel chemical and physical methods, fermentation lost its mark as a food preservation technique although it is used for the production of a wide variety of foods including dairy products, vegetable and fruit products and meat products.

The modern chemical and physical methods of food preservation are more effective than the traditional methods, nonetheless, not without drawbacks. Most chemical preservatives such as nitrites have shown to be toxic, and often accused of being carcinogenic. The physical treatments such as application of high temperature destroy the essential nutrients and they may also alter the organoleptic properties of foods. Hence the consumers demand for the foods minimally processed, drawing the attention back on the traditional food preservation techniques.

Food Biopreservation versus Fermentation

Biopreservation is more or less similar to fermentation in the sense that it uses microorganisms- endogenous or added- and/or their natural antimicrobial products to extend the shelf life of foods. In fact, many food-grade bacteria serve as biopreservatives as well as fermenters.

Nevertheless, the term biopreservation is used in a broader sense than fermentation. Some biopreservative microorganisms may not ferment foods although they may produce inhibitory substances against pathogenic or spoilage microflora. Moreover, the new trend of using bacteriophages as biopreservatives also places biopreservation a step further ahead traditional fermentation.

Biopreservation of foods is mainly achieved through two approaches;

1. the addition of protective cultures i.e. live microorganisms and
2. the addition of antimicrobial compounds produced by the microorganisms

Protective Cultures versus Starter Cultures

Some live microorganisms added to foods serve a bioprotective function by safeguarding the foods against undesirable microorganisms. These bacterial cultures are termed as Protective Cultures.

This strategy is based on the concept of microbial antagonism where microbes hinder the growth of other microorganisms either by competing for space and nutrients or by releasing inhibitory substances such as organic acids, hydrogen peroxide, and bacteriocins. In the case of bacteriophages, they control the undesirable bacteria by invading the cells by destroying them or hindering their metabolism.

In order to be considered as a protective culture, a selected bacterial species has to meet certain criteria.

1. They have to be nonpathogenic as well as non-toxigenic.
2. They have to inhibit the growth of undesirable microorganisms.
3. They should not impart any undesirable characteristics in the food.

These protective cultures do not necessarily have to ferment foods in order to produce a preserving effect. Thus they stand apart from the ‘starter cultures’ which are used in the fermentation processes that always cause a sensory alteration of the food.

Apart from hindering the growth of other spoilage and pathogenic microorganisms, some bacteria may serve as indicators of temperature abuse of some refrigerated foods. Types of bacteria used for this purpose cannot grow under refrigeration temperatures therefore an increase of temperature would be indicated by the increase of population of the said bacterial species.

Some Common Biopreservative Bacteria

Lactic Acid Bacteria are the most widely studied group of microorganisms for biopreservation of foods. Many species of lactic acid bacteria are considered GRAS (Generally Regarded as Safe) and are currently used as biopreservatives. Lactic acid bacteria of the genera Lactococcus, Lactobacillus, and Pediococcus have successfully demonstrated their potential of controlling pathogens such as Clostridium botulinum, Salmonella, and Staphylococcus aureus in milk, meat and seafood products.

Moreover, certain yeasts, including strains of Saccharomyces cerevisiae have also been reported to produce antimicrobial proteins suggesting the possibility of using them as biopreservatives.

Furthermore, bacteriophages have also proposed as a potential biopreservatives against bacteria such as E. coli O157:H7, Salmonella and Listeria monocytogenes which are common culprits of food spoilage and food-borne illnesses.

Bacterial Metabolites as Biopreservatives

Antimicrobial substances produced mainly by lactic acid bacteria including organic acids, acetaldehyde, ethanol, hydrogen peroxide, carbon dioxide, diacetyl, reuterin and bacteriocins are important as biopreservatives.

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These substances may be produced by the viable bacterial cells added as protective cultures while some of them can be added independently to control spoilage and pathogenic flora of foods. Such natural preservatives include organic acids such as acetic and propionic acid which are produced by Acetobacter aceti and Propionibacterium spp. respectively. Acetic acid its salts are inhibitory against a broad range of bacteria- both Gram-positive and negative as well as yeasts, and moulds. Propionic acid and its salts mainly have a fungistatic effect.

Bacteriocins, a type of antimicrobial peptides, are another important group of biological preservatives. Nisin, a Class I bacteriocin produced by Lactococcus lactis, is commercially available as a food preservative in purified form and is widely used in products such as processed cheese, dairy products and canned foods. It inhibits pathogens like L. monocytogenes and many Gram-positive bacterial species causing food spoilage.

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1. Ananou, S., Maqueda, M., Martínez-Bueno, M., & Valdivia, E. (2007). Biopreservation, an ecological approach to improve the safety and shelf-life of foods. Communicating current research and educational topics and trends in applied microbiology, 1, 475-486.

2. Garcia, P., Martinez, B., Obeso, J. M., & Rodriguez, A. (2008). Bacteriophages and their application in food safety. Letters in applied microbiology, 47(6), 479-485.
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Bacteriophages and food preservation

The original article in this thread outlined the history of biopreservation of food. The article alluded to use of bacteriophages in this field. Bacteriophages are viruses that kill bacteria. Some recent studies have focused in particular on the use of bacteriophages in defence against Salmonella species. Salmonella is the major international cause of food-borne diseases so strategies to combat it need further development.

A study from Konkuk University in South Korea examined the capacity of bacteriophage ΦCJ07 to combat Salmonella enteritidis (SE) infection in chickens. Chicks challenged with SE were placed in contact with other chicks and treated with three different concentrations of bacteriophage ΦCJ07 plaque forming units (PFU) in their feed for 21 days. Intestinal Salmonella infection was measured at 1,2 and 3 weeks and it was observed that all three concentrations of bacteriophage reduced intestinal SE concentrations in both challenged and contact birds, with 107 and 109 PFU/g giving significant reductions compared to untreated controls. Treatment of contact chicks with 109 PFU/g protected them from cross-infection with SE. Thus this bacteriophage is indicated as a potentially useful tool in protection of poultry from SE infection with a knock-on effect on the incidence of Salmonella food poisoning.

Other studies from Universitat Autònoma de Barcelona have examined uses of bacteriophage cocktails in animal models as well as in food matrices. A cocktail of three bacteriophages (UAB_Phi20, UAB_Phi78, and UAB_Phi87) was prepared and found to be more effective than anyn of the three separately in inducing lysis of S. Enteritidis and S. Typhimurium in vitro, as well as being able to lyse the Salmonella enterica serovars Virchow, Hadar, and Infantis. In both a mouse model and a White Leghorn chicken specific-pathogen-free (SPF) model the most effective reduction of Salmonella infection concentration was obtained when the bacteriophage cocktail was administered at about the time of bacterial infection and then again on different days post infection. The same bacterial cocktail was examined in four food matrices, namely pig skin, chicken breasts, fresh eggs, and packaged lettuce, which were infected under experimental conditions with Salmonella enterica serovar Typhimurium and S. enterica serovar Enteritidis. In environmental conditions similar to how they would be normally stored, the bacteriophage cocktail was found to induce significant bacterial reduction in pig skin, chicken breasts and lettuce, but was relatively ineffective for fresh eggs.

The use of bacteriophages in food preservation will continue to gain acceptance against the background of consumer demand for decreased chemical preservation and continuing research is essential to help realise their potential.


BARDINA, C. et al., 2012. Significance of the bacteriophage treatment schedule in reducing Salmonella colonization of poultry. Applied and Environmental Microbiology, 78(18), pp. 6600-6607

LIM, T. et al., 2012. Use of bacteriophage for biological control of Salmonella Enteritidis infection in chicken. Research in veterinary science, 93(3), pp. 1173-1178

SILLANKORVA, S.M., OLIVEIRA, H. and AZEREDO, J., 2012. Bacteriophages and their role in food safety. International Journal Of Microbiology, 2012, pp. 863945-863945

SPRICIGO, D.A. et al., 2013. Use of a bacteriophage cocktail to control Salmonella in food and the food industry. International journal of food microbiology, 165(2), pp. 169-174

SULAKVELIDZE, A., 2013. Using lytic bacteriophages to eliminate or significantly reduce contamination of food by foodborne bacterial pathogens. Journal of the science of food and agriculture, 93(13), pp. 3137-3146

WALMAGH, M. et al., 2012. Characterization of modular bacteriophage endolysins from Myoviridae phages OBP, 201f2-1 and PVP-SE1. Plos One, 7(5), pp. e36991-e36991
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Biopreservation: Re-discovering a 'Forgotten' Concept00