Acknowledgments: This research has been co‐financed by the European Regional Development Fund of the European Union and Greek national funds through the Operational Program Competitiveness, Entrepreneurship and Innovation, under the call RESEARCH–CREATE–INNOVATE (Project code:T1EDK-03942).
Several novel antimicrobials with different concentrations of olive, pomegranate and orange fruit pulp extracts were produced from agricultural byproducts and, after lyophilization, their antimicrobial activity and potential synergistic effects were evaluated in vitro and in food samples against foodborne pathogenic and spoilage bacteria spoilage bacteria and fungi.
The Minimum Inhibitory of the tested bacteria was 7,5% or 10%, while fungi were inhibited at a concentration of 10% or above. Τhe optical density of bacterial and yeast cultures was reduced to different extend with all tested antimicrobial powders, compared to a control without antimicrobials, and mycelium growth of fungi was also restricted with extracts containing at least 90% olive extract.
In food samples with inoculated pathogens and spoilage bacteria and fungi, the 100% olive extract was most inhibitory against E. coli, S. typhimurium and L. monocytogenes in fresh burger and cheese spread samples (by 0.6 to 1.8 log cfu/g), except that S. typhimurium was better inhibited by a 90% olive and 10% pomegranate extract in burgers. The latter extract was also the most effective in controlling the growth of inoculated fungi (Αspergillus niger, Penicillium italicum, Rhodotorula mucilaginosa) in both yogurt and tomato juice samples, where it reduced fungal growth by 1-2,2 log cfu/g at the end of storage period.
The results demonstrate that these novel encapsulated extracts could serve as natural antimicrobials of wide spectrum, in order to replace synthetic preservatives in foods and cosmetics.
In the context of the present research work, a comprehensive investigation is carried out to determine potential antimicrobial synergism of mixed liquid olive fruit extract and solid pomegranate juice and/or orange juice industry solid waste extracts. The ultimate aim of the project is by mixing them at optimized proportions to obtain liquid natural plant protection products for application in organic farming or alternatively encapsulated powders of the mixed extracts for use as natural preservatives in food and cosmetics to replace the currently used hazardous chemical preservatives (e,g, sorbates, sodium benzoate, parabens etc).
The industrial production of the novel liquid plant protection products as well as the encapsulated natural antimicrobial powders after their fore coming development and optimization will be carried out by the natural plant products industry POLYHEALTH S.Alink. which is the beneficiary of the project. The manufacturing of the novel products will be performed by mixing concentrated olive polyphenol extract, which is currently produced and commercialized by the company under the trade mark MEDOLIVA with extracts of solid wastes of pomegranate and orange juice industry to obtain antimicrobial synergism.
On the other hand, University of Thessaly-Laboratory of Food and Biosystems Engineering (www.fabe.grlink) acting as subcontractor, was assigned by the optimization of the state-of-the-art industrial scale vacuum microwave assisted extraction on economic grounds and by using advanced mathematical methods, in order to provide to POLYHELTH S.A. the required optimal extraction conditions for its future commercial production of the pomegranate and orange pomace extracts.
In the context of the present project, the liquid extracts produced by economically optimized VMAE are aimed to be used as raw material to produce natural phytochemical in liquid form and in addition encapsulated powders by mixing them with various edible and clean label encapsulation agents followed by intensive ultrasonic homogenization and final drying by using cryogenic freeze drying in a totally optimized production process.
After the production of liquid synergistic products, the subcontractor, University of Thessaly, will investigate, in vitro, their activity against plant and tree soil and foliar phytopathogens in order to determine the optimal mixing composition. Subsequently, by using this optimal composition obtained by in vitro tests UTH will carry out in vivo tests to determine the optimal concentration of field application and suggest potential utilities required to ensure better performance during the applications (e.g. addition of hydrocolloids or surfactants).
Similarly, the novel encapsulated powders are programmed to be tested by University of Thessaly initially in vitro and by using three respective antimicrobial activity evaluation methods for potential antimicrobial activity against pathogenic and/or spoilage microorganisms of food and cosmetics. Afterwards in a second stage the best performing powders according to in vitro tests for the various yeast fungi and bacteria is programmed to be tested in vivo by addition to selected food and cosmetics in order to determine their minimum concentrations required to achieve effective preservation of the tested foods and cosmetics.
POLYHEALTH A.E. (www.polyhealth.gr)
UNIVERSITY OF THESSALY
POLYHEALTH S.A. and the other participating bodies in this project express their gratitude for the financial support granted by the European Union and the Greek State through the monitoring body EYDE-ETAK within the Framework of the NATIONAL ACTION programme: “RESEARCH-CREATE-INNOVATE” Project code: Τ1ΕΔΚ-03942