Di Martino, Veronica (2016) MICROBIAL CULTURES AND LEAF EXTRACTS OF MYRTUS COMMUNIS L., STRATEGIES DESIGNED TO ENSURE QUALITY, SAFETY AND HEALTHY PROPERTIES OF FOOD PRODUCTS. [Tesi di dottorato]

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Item Type: Tesi di dottorato
Lingua: English
Title: MICROBIAL CULTURES AND LEAF EXTRACTS OF MYRTUS COMMUNIS L., STRATEGIES DESIGNED TO ENSURE QUALITY, SAFETY AND HEALTHY PROPERTIES OF FOOD PRODUCTS
Creators:
CreatorsEmail
Di Martino, Veronicaveronica_dimartino@yahoo.it
Date: 31 March 2016
Number of Pages: 120
Institution: Università degli Studi di Napoli Federico II
Department: Agraria
Scuola di dottorato: Scienze agrarie e agro-alimentari
Dottorato: Scienze e tecnologie delle produzioni agro-alimentari
Ciclo di dottorato: 27
Coordinatore del Corso di dottorato:
nomeemail
Barbieri, Giancarlobarbieri@unina.it
Tutor:
nomeemail
Villani, FrancescoUNSPECIFIED
Ferranti, PasqualeUNSPECIFIED
Date: 31 March 2016
Number of Pages: 120
Uncontrolled Keywords: myrtus communis, bactericin, antimicrobial activity
Settori scientifico-disciplinari del MIUR: Area 07 - Scienze agrarie e veterinarie > AGR/16 - Microbiologia agraria
Date Deposited: 08 Apr 2016 09:40
Last Modified: 06 May 2019 01:00
URI: http://www.fedoa.unina.it/id/eprint/11120

Abstract

Food quality is a wide topic, made up of several attributes such as health and hygiene safety, the correct nutrient intake and the sensory satisfaction. In their totality these properties correspond to the ability to meet the health expectations and answer hedonistic needs. As result of this awareness was the born of a new binomial, often inseparable, well defined by the term "safety-health food", which emphasizes the role of safety as an intrinsic part of the quality from which it cannot be separated due to the great impact on human health. Therefore, it can be affirmed that food security represent a precondition of food quality. This correspond to the absence of any danger to the consumer who uses food properly prepared, stored and handled. Despite the advances in technology, food safety is still an open question, not only for developing countries, but also for the industrialized world. Food represent given their physical and chemical properties a supportive environment for the growth and the proliferation of spoilage and pathogenic microbial species which are able to enter the body through the gastrointestinal tract where the often occur first symptoms of infection. The severity of the food diseases in humans varies, moving from mild symptoms to life-threatening conditions and the hazard intensity depends by several key factors moving from the health state, the immunity system conditions of the host and the antimicrobial resistance of bacteria, corresponding to the ability of microbes to resist the effects of drugs. The risks of contamination are ever present for this reason requires prevention and monitoring throughout the food chain. The food industry increasingly tends to produce food with high organoleptic standards, with a long shelf life and with suitable nutritional values. At the same time the consumer requires intensified food security, food products minimally processed and that improve their state of health, in combination with a reduction of the use of chemical additives. The increasing interest in the substitution of synthetic additives by natural ones and also the awareness that the prolonged use of antibiotics increase the resistance of many microorganisms to drugs, have encouraged research on preservatives coming from natural sources such as secondary metabolites of bacteria and plants. Therefore aim of this PhD thesis was to investigate the antimicrobial properties in vitro and in situ of an hydro-alcoholic extract obtained from leaves of Myrtus communis L. and of Lb. curvatus strain producing-bacteriocin(s). Myrtus communis leaves extract obtained through maceration at ambient temperature for 24 hours was tested against 105 indicators strains tested among which food borne pathogens and spoilage bacteria belonging to different species, evaluating the chance to use it in food system through a development of an active packaging. The in vitro results showed a wide spectrum against both Gram positive (Br. thermosphacta, L. monocytogenes, L. innocua, S. aureus) and Gram negative bacteria (C. jejuni, C. coli and P. fragi). Among the pathogenic Gram positive bacteria Listeria monocytogenes OH was found more sensitive to the myrtle effect with MIC and MLC values respectively of 12.5 and 25 mg DM/ml, recording a diameter of inhibition zone of 26 ± 0.05 mm and a titer of 25600 AU ml-1. Results obtained through in vitro assays have been also confirmed by a challenge study carried out, inoculating L. monocytogenes OH in gorgonzola cheese added of myrtle leaves extract in concentration of 12.5 mg/g and stored at refrigerating temperature for 2 weeks, where the initial concentration of the pathogenic strain gradually decreased during 9 days until to disappear after 15 days. Among Gram negative bacteria, P. fragi and Campylobacter spp. seems to appear equally sensitive to the myrtle leaves hydroalcoholic extract. Surprisingly, in literature there are no previous findings about the effect of myrtle on Campylobacter, in spite of its importance as a foodborne pathogen. Therefore, positive data obtained against this specie result very remarkable and interesting. Polyphenols characterized by mass spectrometry are the main molecules responsible of the antimicrobial activity of this hydroalcoholic myrtle leaves extract. One of their mode of action is the cellular membrane damage which was determined by spectrofluorimetric assay of cell viability assay. Another pertinent objective of this thesis was to study the antagonistic activity Lb. curvatus 54M16 isolated from fermented sausage of Vallo di Diano in vitro and in situ against a pathogen strain of great food interest which is L. monocytogenes. Moreover, the technological characteristics were determined in order to investigate its suitability to be used as starter and protective culture for sausage fermentation. The strain was found to possess the gene that encodes the production of different bacteriocins, including the sakTα, the sakTβ, the curvacina A, the sakX and the SAKP, identified by MALDI-TOF-MS analysis. The production of bacteriocins was monitored in MRS broth and evaluated for different temperature conditions (10, 15, 20, 25 and 30 ° C) and times (0, 24, 48 and 72 hours). The strain was able to produce the bacteriocin(s) and in all the conditions listed above, except when incubated at a temperature of 10 ° C, recording the maximum activity 6400 (AU ml -1) after 24 hours at 20, 25 and 30 ° C . The antilisterial activity has also been investigated in situ, adding the strain to the fermented sausage samples which were intentionally inoculated with the strain of L. monocytogenes ATCC 7644. The results show the end of the maturation period, a reduction of the microbial load of 0.5 Log compared to the sample without the 54M16 strain. Finally, to evaluate the potential use of this strain as a starter culture in the sausage fermentations were also determined its technological characteristics, resulting that L. curvatus 54M16 strain has a good acidifying and proteolytic activities being able to hydrolyze the sarcoplasmic proteins.

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