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Gaia Muratore

Phd thesis

Project title: Agro-industrial by-products with bioactive effects: an eco-friendly strategy to improve food safety and quality

Background:

Prevention of food spoilage and control of foodborne diseases are major challenges facing food
industries today. Given the increasing demand of environmentally friendly food production systems, several researches have been conducted in last decades to identify new and green  alternatives to chemical preservatives (1,2). Extracts derived from agricultural by-products might be a promising strategy to improve food safety and extend the shelf-life of food products (3,4,5).

 

Aims

Studies on biological activities of extracts from agricultural wastes, obtained with green and foodgrade extraction methods, are performed:
- in vitro, to evaluate antibacterial and antibiofilm activities on selected bacterial strains;
- in vivo, to assess the effect on safety and shelf-life of meat preparations.

 

Materials and Methods:

It was employed a subcritical water extract from hazelnut pericarp.
Gram positive (B. cereus, E. faecium, L. innocua, L. monocytogenes and S. aureus) and Gram negative (E. coli, P. fluorescens and S. enterica) bacteria were used to screen antibacterial activity of hazelnut extract. Minimum Inhibitory Concentration (MIC) values were determined by using the broth microdilution method described by Clinical and Laboratory Standards Institute (CLSI), suitably modified. The new protocol was validated on reference strains.

The panel of bacteria was also used to check the ability of biofilm formation following the protocol of Stepanovic et al. (6) beforehand the antibiofilm assay.

In vivo experimental trials were conducted on control and treated burger meats, prepared with different quantities of hazelnut extract (2% and 4%), to evaluate the effect on sensory characteristics and shelf-life. Total Viable Count, Enterobacteriaceae and Pseudomonas spp. were determined after 0, 3 and 6 days of refrigerated storage. Colorimetric and spectro-colorimetric evaluations, pH measurements and cooking weight loss were also carried out.

 

Preliminary results:

Hazelnut extract revealed antimicrobial activity mainly against the tested Gram positive bacteria; S. enterica and P. fluorescens were not sensitive to all the assayed concentrations while E. coli responded at 40 mg/mL. 

Concerning the screening of biofilm formation, strong and no biofilm producers were identified. 

In regard of in vivo trial results, there are not noticeable differences between the variously treated and control samples for al the items analyzed. In fact, the microbial content resulted slightly lower (0,1 log - 0,4 log) in treated groups than in control ones at 3 and 6 days of storage. In addition, in the second trial, there was also a higher increase in Enterobacteriacee count of treated burgers, due to the presence of a psychotrophic Hafnia alvei, identified with MALDI TOF technology, whose growth was not inhibited by the two extract concentrations tested. 

The addition of 4% of hazelnut extract in treated burgers did not affect pH values, while weight loss of treated samples increased more than upon cooking.

With regard to colorimetric evaluations, lightness (L*) values increases as the amount of extract decreases. Although, results of instrumental color evaluations are still being analyzed. 

 

Future developments:

MICs determination on further pathogenic bacterial strains will be carried out, given the strain-dependent response. 

The evaluation of antibiofilm potential will be performed following the Minimum Biofilm Eradication Concentration assay, as described by Innovotech guidelines.

Furthermore, new extracts from hazelnut skins and freeze-dried apple pomace using a supercritical CO2 fluid extractor (SCF-100; Separeco s.r.I., Pinerolo, Italy), wil be employed on "in vitro" and "in vivo" tests: the same protocol used in the first part of the trial wil therefore be applied.

A further step will be the development of challenge tests using the extract with the best in vivo performance. 

 

References:

1. Bouarab Chibane L, Degraeve P, Ferhout H, Bouajila J, Oulahal N. Plant antimicrobial polyphenols as potential natural food preservatives. Journal of the Science of Food and Agriculture. 2019;99(4):1457-74.

2. Reguengo LM, Salgaço MK, Sivieri K, Maróstica Júnior MR. Agro-industrial by-products: Valuable sources of bioactive compounds. Food Research International. 1 Febbraio 2022;152:110871.

3. Gonelimali FD, Lin J, Miao W, Xuan J, Charles F, Chen M, et al. Antimicrobial Properties and
Mechanism of Action of Some Plant Extracts Against Food Pathogens and Spoilage Microorganisms. Front Microbiol. 2018;9:1639.

4. Lemes AC, Egea MB, Oliveira Filho JGD, Gautério GV, Ribeiro BD, Coelho MAZ. Biological
Approaches for Extraction of Bioactive Compounds From Agro-industrial By-products: A Review. Frontiers in Bioengineering and Biotechnology. 2022;9.

5. Mostafa AA, Al-Askar AA, Almaary KS, Dawoud TM, Sholkamy EN, Bakri MM. Antimicrobial activity of some plant extracts against bacterial strains causing food poisoning diseases. Saudi Journal of Biological Sciences. 1 Febbraio 2018;25(2):361-6.

6. Stepanovic S, Vukovic D, Hola V, Di Bonaventura G, Djukic S, Cirkovic I, et al. Quantification of biofilm in microtiter plates: overview of testing conditions and practical recommendations for assessment of biofilm production by staphylococci. APMIS. Agosto 2007;115(8):891-9.

Research activities

Co supervisor

Pierluigi Di Ciccio 

Abstract

 

Pattono D., Muratore G., Catania A. M., Ala U., Dalmasso A., Rossetto P., Bottero M. T. (2023). Evaluation of bacterial translocation in routine and emergency slaughtering; in proceeding of the 76th SISVET Congress, Bari (Italy); 21-23/06/2023. 

 

Poster

- Muratore G., Di Ciccio P. A., Troisi E., Forte C., Civera T. (2023). Evaluation in vitro and in vivo antimicrobial activity of hazelnut waste extract. In proceeding of the 3rd Turin edition of Game of Research, Turin (Italy); 14/12/2023. 

 

Last update: 25/01/2024 12:44

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