Barbosa, Joana

Gomes, Joana

Teixeira, Paula

English

Repositório Institucional da Universidade Católica Portuguesa

Natural antimicrobial agents and their potential on the preservation of foodCBQF - Centro de Biotecnologia e Química Fina, Laboratório Associado, Escola Superior de Biotecnologia, Universidade Católica Portuguesa, Porto, Portugal*Corresponding author: pcteixeira@porto.ucp.ptAcknowledgementsThe authors acknowledge the financial support in the framework of the project “Biologicaltools for adding and defending value in key agro-food chains (bio – n2 – value)”, nº NORTE-01-0145-FEDER-000030, funded by Fundo Europeu de Desenvolvimento Regional (FEDER), underPrograma Operacional Regional do Norte - Norte2020. We would also like to thank thescientific collaboration under the FCT project UID/Multi/50016/2013. Financial support forauthor J. Barbosa was provided by a post-doctoral fellowship SFRH/BPD/113303/2015 (FCT).IntroductionResultsConclusionsJoana Gomes, Joana Barbosa, Paula Teixeira*Microbiological quality of food is of considerable concern to the food industry, since the activity of microorganisms can cause deterioration and, more seriously,affect the health of consumers [1]. Therefore, chemical additives are added to most of the foods with the purpose of maintaining certain properties orprolonging their shelf life [2]. However, there are several health-related problems associated with the use of these additives. Due to the problem ofdemonstrated or potential toxicity to the consumers, the number of chemical compounds allowed as food preservatives is limited [3]. Although, currently, mostpreservatives have no side effects and are classified as safe, there have been problems with the safety of some of these chemicals.The objective of this work was to determine the minimum inhibitory concentrations of three natural antimicrobial agents (ethanolic extract of propolis, chitosanand nisin) against 32 microorganisms (15 Gram-positive and 15 Gram-negative bacteria and two fungi) in order to compare with the minimum inhibitoryconcentrations of the chemical compound sodium nitrite, alone and in combination with sodium chloride. The inhibition of microorganisms was also tested atdifferent pH values and temperatures of incubation to simulate the presence of the pathogens in different foods stored at different conditions.Natural AntimicrobialsEthanolic Extract of PropolisChitosanNisinChemical AntimicrobialSodium nitrite, alone and in combination with sodium chlorideComparison of the antimicrobial activity of natural and chemical compounds21 Gram-positivebacteria15 Gram-negativebacteria2 FungiAntimicrobial activity of the compounds was tested in 38 different microorganismsAntimicrobial activity was evaluated under different conditionsDrop agar diffusionDetermination of the minimum inhibitory concentration by two methodsAgar dilutionFigure 1. Comparison of the total number of inhibitedmicroorganisms by the different compounds, by agar dilutionmethod (blue) and drop agar diffusion method (orange), at pH 6and 37°C.Figure 2. Number Gram + (blue), Gram - (orange) and fungi(gray) inhibited by the different compounds, at pH 6 and 20°C.The natural compounds tested had greater inhibitory effect against the various microorganisms compared with the sodium nitrite alone and in combinationwith sodium chloride, in the different conditions of pH and temperature. Chitosan at 0.65% (w/v) inhibited most of the tested microorganisms. At 10 mg/mL ofpropolis, fungi, most of the Gram-positive and some of the Gram-negative bacteria were inhibited. At 25 µg/mL of nisin it was possible to inhibit most of theGram-positives. Sodium nitrite, individually or in combination with sodium chloride, did not inhibit most microorganisms. The minimum inhibitoryconcentrations of several microorganisms were different depending on the methodology.With these in vitro results, it seems that the natural compounds investigated are good alternatives to chemical antimicrobials used in food production.[1] Casquete R, Castro SM., Jácome S, Teixeira P. Antimicrobial activity of ethanolic extract of propolis in “Alheira”, a fermented meat sausage. Cogent FoodAgric 2016a; 2: 7.[2] Branen AL, Haggerty RJ. Introduction to Food Additives. In: Food Additives (Eds. Branen, A.L., Davidson, P.M., Salminen, S. & Thorngate, J.H.), MarcelDekker, Nova Iorque. 2002.pp. 1-9.[3] Russell AD. Mechanisms of bacterial resistance to non-antibiotics: food additives and food and pharmaceutical preservatives. J Appl Microbiol 1991; 71: 191-201.

Natural antimicrobial agents and their potential on the preservation of food

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Natural antimicrobial agents and their potential on the preservation of food

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Repositório Institucional da Universidade Católica Portuguesa