Several ready-to-eat foods (RTE), including cheeses, are considered to be at high risk of contamination by Listeria monocytogenes. This pathogen can get higher contamination levels, even at refrigeration temperatures, and pose a risk to the consumer. Probiotic Lactic Acid Bacteria (LAB), like bioprotective cultures, can be regarded as an interesting opportunity to control the growth of Listeria monocytogenes in sheep's milk cheeses. However, in order to respect the specifications provided for the protected designation of origin (PDO) cheese, only autochthonous microorganisms can be used as bioprotective cultures. At the same time, most of the commercial protective cultures are composed by mesophilic bacteria, while some cheesemaking processes promote primary fermentation from thermophilic microorganisms. With this in mind, the present study aimed to evaluate two bio-preservative approaches to control L. monocytogenes growth during the PDO cheese production process: (I) use of a commercial protective culture (PC) composed by a selected L. plantarum bacteriocins producer; (II) use of a thermophilic LAB isolated from sheep milk. The study included the assessment of the in vitro antimicrobial activity of a PC and autochthonous LAB against L. monocytogenes, and their adaptability to the cheese production process. A challenge test was conducted to assess the growth potential of L. monocytogenes in artificially contaminated Pecorino Sardo PDO cheese and inoculated with the best performing autochthonous LAB, Lactobacillus delbrueckii subsp. sunkii, and the PC. Results showed that L. sunkii and PC limited the growth of L. monocytogenes under storage at 4°C and 10°C (<2 Log UFC/g) at the end of the shelf-life, that is, 70 days after artificially contamination. Results of qualitative analysis, at the end of the shelf life, showed the presence of L. monocytogenes in 26,8% of samples inoculated with L.sunkii and in 29,3% of samples inoculated with PC. 43,9% of L. monocytogenes isolates came from samples without bioprotective culture inoculum. It can therefore be said that both cultures tested showed anti-listerial activity with a slightly higher efficacy for L. sunkii than L. plantarum (PC). This modelling approach, in association with a strict application of hygiene procedures, could be a successful strategy in counteracting the presence of L. monocytogenes in foods. The technological innovation proposed, has important repercussions on sheep dairy industries that will be able to take advantage of this strategy to give further evidence on cheese safety.

Adozione di colture bioprotettive per migliorare la sicurezza e la conservabilità dei formaggi a base di latte ovino / Meloni, Maria Pina. - (2022 May 05).

Adozione di colture bioprotettive per migliorare la sicurezza e la conservabilità dei formaggi a base di latte ovino

MELONI, Maria Pina
2022-05-05

Abstract

Several ready-to-eat foods (RTE), including cheeses, are considered to be at high risk of contamination by Listeria monocytogenes. This pathogen can get higher contamination levels, even at refrigeration temperatures, and pose a risk to the consumer. Probiotic Lactic Acid Bacteria (LAB), like bioprotective cultures, can be regarded as an interesting opportunity to control the growth of Listeria monocytogenes in sheep's milk cheeses. However, in order to respect the specifications provided for the protected designation of origin (PDO) cheese, only autochthonous microorganisms can be used as bioprotective cultures. At the same time, most of the commercial protective cultures are composed by mesophilic bacteria, while some cheesemaking processes promote primary fermentation from thermophilic microorganisms. With this in mind, the present study aimed to evaluate two bio-preservative approaches to control L. monocytogenes growth during the PDO cheese production process: (I) use of a commercial protective culture (PC) composed by a selected L. plantarum bacteriocins producer; (II) use of a thermophilic LAB isolated from sheep milk. The study included the assessment of the in vitro antimicrobial activity of a PC and autochthonous LAB against L. monocytogenes, and their adaptability to the cheese production process. A challenge test was conducted to assess the growth potential of L. monocytogenes in artificially contaminated Pecorino Sardo PDO cheese and inoculated with the best performing autochthonous LAB, Lactobacillus delbrueckii subsp. sunkii, and the PC. Results showed that L. sunkii and PC limited the growth of L. monocytogenes under storage at 4°C and 10°C (<2 Log UFC/g) at the end of the shelf-life, that is, 70 days after artificially contamination. Results of qualitative analysis, at the end of the shelf life, showed the presence of L. monocytogenes in 26,8% of samples inoculated with L.sunkii and in 29,3% of samples inoculated with PC. 43,9% of L. monocytogenes isolates came from samples without bioprotective culture inoculum. It can therefore be said that both cultures tested showed anti-listerial activity with a slightly higher efficacy for L. sunkii than L. plantarum (PC). This modelling approach, in association with a strict application of hygiene procedures, could be a successful strategy in counteracting the presence of L. monocytogenes in foods. The technological innovation proposed, has important repercussions on sheep dairy industries that will be able to take advantage of this strategy to give further evidence on cheese safety.
5-mag-2022
biopreservation; Protective cultures; Lactic Acid Bacteria; cheese; L. monocytogenes
L. monocytogenes
Adozione di colture bioprotettive per migliorare la sicurezza e la conservabilità dei formaggi a base di latte ovino / Meloni, Maria Pina. - (2022 May 05).
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11388/287116
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