Food ©2007 Global Science Books Food Preservation – A Biopreservative Approach Iraj Rasooli Department of Biology, Shahed University, Opposite Imam Khomeini’s Shrine, Tehran-Qom Express Way, Tehran, Iran Correspondence : * [email protected] ABSTRACT Preservative agents are required to ensure that manufactured foods remain safe and unspoiled. Antimicrobial properties of essential oils (EOs) reveal that Gram-positive bacteria are more vulnerable than Gram-negative bacteria. A number of EO components have been identified as effective antibacterials, e.g. carvacrol, thymol, eugenol, cinnamaldehyde and cinnamic acid, having minimum inhibitory concentrations (MICs) at higher dilutions in vitro. EOs comprise a large number of components and it is likely that their mode of action involves several targets in the bacterial cell. The potency of naturally occurring antimicrobial agents or extracts from plants, ranges of microbial susceptibility and factors influencing antimicrobial action and their antioxidative properties, aimed at food preservation, are reviewed in this article. Methods employed for estimation of inhibitory activity, mode of action and synergistic and antagonistic effects are evaluated. The potential value of these agents as natural and biological preservatives is considered. _____________________________________________________________________________________________________________ Keywords: essential oils, food safety, natural antimicrobials, natural flavor complexes, toxicity CONTENTS INTRODUCTION...................................................................................................................................................................................... 111 INFLUENCE OF CHEMICAL COMPOSITION OF ESSENTIAL OILS ON THEIR ANTIMICROBIAL ACTIVITIES ...................... 113 IN VITRO ANTIMICROBIAL ACTIVITIES OF ESSENTIAL OILS....................................................................................................... 114 IN VITRO ANTIMICROBIAL ASSAY METHODS.................................................................................................................................. 116 AFLATOXIN THREAT AND HERBAL CONTROL................................................................................................................................ 117 ANTIOXIDATIVE PROPERTIES............................................................................................................................................................. 118 ESSENTIAL OILS IN FOOD.................................................................................................................................................................... 121 Meat products........................................................................................................................................................................................ 122 Dairy products ....................................................................................................................................................................................... 123 Vegetables and fruits.............................................................................................................................................................................. 123 Organoleptic aspects.............................................................................................................................................................................. 124 Other factors.......................................................................................................................................................................................... 124 ESSENTIAL OILS, SYNERGISTIC, AND ANTAGONISTIC VIEW...................................................................................................... 124 DAMAGE TO MICROBIAL CELLS........................................................................................................................................................ 125 GENOTOXICITY OF ESSENTIAL OILS AND SAFETY CONCERNS ................................................................................................. 128 FUTURE RESEARCH .............................................................................................................................................................................. 129 ACKNOWLEDGEMENTS ....................................................................................................................................................................... 130 REFERENCES........................................................................................................................................................................................... 130 _____________________________________________________________________________________________________________ INTRODUCTION nutritious, natural and easy-to-handle food products. Im- provements in the cold distribution chain have made inter- Many food products are perishable by nature and require national trade of perishable foods possible, but refrigeration protection from spoilage during their preparation, storage alone cannot assure the quality and safety of all perishable and distribution to give them desired shelf-life. Because foods. food products are now often sold in areas of the world far The most common classical preservative agents are the distant from their production sites, the need for extended weak organic acids, for example acetic, lactic, benzoic and safe shelf-life for these products has also expanded. sorbic acid. These molecules inhibit the outgrowth of both The development of food preservation processes has bacterial and fungal cells and sorbic acid is also reported to been driven by the need to extend the shelf-life of foods. inhibit the germination and outgrowth of bacterial spores. Food preservation is a continuous fight against microorga- In the production of food it is crucial that proper mea- nisms spoiling the food or making it unsafe. Several food sures are taken to ensure the safety and stability of the pro- preservation systems such as heating, refrigeration and duct during its whole shelf-life. In particular, modern con- addition of antimicrobial compounds can be used to reduce sumer trends and food legislation have made the successful the risk of outbreaks of food poisoning; however, these attainment of this objective much more of a challenge to the techniques frequently have associated adverse changes in food industry. Firstly, consumers require more high quality, organoleptic characteristics and loss of nutrients. Within the preservative-free, safe but mildly processed foods with disposable arsenal of preservation techniques, the food extended shelf-life. For example, this may mean that foods industry investigates more and more the replacement of tra- have to be preserved at higher pH values and have to be ditional food preservation techniques by new preservation treated at mild-pasteurization rather than sterilization tem- techniques due to the increased consumer demand for tasty, peratures. As acidity and sterilization treatments are two Received: 13 June, 2007. Accepted: 18 July, 2007. Invited Review Food 1(2), 111-136 ©2007 Global Science Books crucial factors in the control of outgrowth of pathogenic scientific interest in these substances (Tuley 1996). Besides spore-forming bacteria, such as Clostridium botulinum, ad- antibacterial properties (Mourey and Canillac 2002; Rasooli dressing this consumer need calls for innovative approaches and Razzaghi 2004; Rasooli and Owlia 2005), EOs or their to ensure preservation of products. Secondly, legislation has components have been shown to exhibit antiviral (Bishop restricted the use and permitted levels of some currently 1995), antimycotic (Mari et al. 2003), anti oxidative (Gach- accepted preservatives in different foods. This has created kar et al. 2006; Yadegarinia et al. 2006; Bektas et al. problems for the industry because the susceptibility of some 2007a; Bektas et al. 2007b), antitoxigenic (Akgul et al. microorganisms to most currently used preservatives is 1991; Juglal et al. 2002; Ultee and Smid 2001), antiparasitic falling. (Pandey et al. 2000; Pessoa et al. 2002), and insecticidal An increasing number of consumers prefer minimally (Karpouhtsis et al. 1998) properties. These characteristics processed foods, prepared without chemical preservatives. are possibly related to the function of these compounds in Many of these ready-to-eat and novel food types represent plants (Mahmoud and Croteau 2002). The antibacterial pro- new food systems with respect to health risks and spoilage perties of EOs and their components are exploited in such association. Against this background, and relying on im- diverse commercial products as dental root canal sealers proved understanding and knowledge of the complexity of (Manabe et al. 1987), antiseptics (Cox et al. 2000) and feed microbial interactions, recent approaches are increasingly supplements for lactating sows and weaned piglets (van directed towards possibilities offered by biological presser- Krimpen and Binnendijk 2001; Ilsley et al. 2002). It is vation. therefore scientifically sound to evaluate the impact of EOs Throughout the development of both Western and Eas- on food and food products safety. tern civilization, plants, plant parts, and derived oils and Natural flavor complexes (NFCs) are mixtures of extracts have functioned as sources of food and medicine, mainly low molecular