Elsevier

Food Microbiology

Volume 93, February 2021, 103596
Food Microbiology

Efficacy of combinations of lactic acid and potassium sorbate against Listeria monocytogenes in chicken stored under modified atmospheres

https://doi.org/10.1016/j.fm.2020.103596Get rights and content

Highlights

  • Combinations of lactic acid (LA) and potassium sorbate (PS) are effective against psychrotrophs.

  • Combinations of lactic acid and potassium sorbate are effective against L. monocytogenes.

  • Chicken packaged in MAP has an extended shelf life, but L. monocytogenes is not inhibited.

  • Treatment with combinations of LA and PS reduce growth of L. monocytogenes in chicken packaged in MAP.

Abstract

The combined effect of lactic acid and potassium sorbate on the growth of L. monocytogenes on chicken legs packaged under modified atmospheres (MAP) and stored at 4 °C was evaluated. An extended lag phase and a lower maximum growth rate for psychrotrophs and mesophiles was found in those samples packaged in 20%CO2/80%N2 and washed with different combinations of lactic acid and potassium sorbate compared to those non-treated with organic acids. Legs packaged in 20%CO2/80%N2 and washed with 3.75% lactic acid- 3.75% potassium sorbate showed a significant (p < 0.05) reduction in L. monocytogenes compared to untreated chicken legs packaged in MAP, which were approximately 2.63 log units lower in the first ones after 8 days of storage. Moreover, this treatment was the most effective in decreasing the maximum growth rate of L. monocytogenes. The chicken legs packaged in atmospheres containing 20%CO2/80%N2, had an extended shelf life, but these atmospheres were not able to reduce L. monocytogenes, thus underlining the need for preventive measures so as to control this pathogen. The immersion of chicken legs in a solution containing 3.75% lactic acid- 3.75% potassium sorbate can reduce L monocytogenes populations on fresh chicken packaged in a modified atmosphere.

Introduction

Poultry and poultry products are frequently involved in foodborne disease outbreaks. Listeria monocytogenes is often present in chicken and the multiplication and spread of this pathogen on chicken meat can easily occur. The higher pH in leg meat, compared to other chicken portions such as breasts, provides more favourable conditions for the growth of L. monocytogenes. Moreover, the shelf life of raw chicken is very short and it would undoubtedly be useful in extending shelf-life to meet commercial requirements (González-Fandos and Dominguez, 2007; ICMSF, 1998).

Organic acids have been traditionally used as antimicrobials in foods, since they are generally considered as safe (GRAS) (Simón et al., 2010). High levels of organic acids are needed to reduce bacterial populations, but those concentrations can have adverse effects on product quality (Samant et al., 2015). Several studies have addressed the use of lactic acid or sorbate on chicken (González-Fandos and Dominguez, 2007; Zeitoun and Debevere, 1991).

The effectiveness of lactic acid in controlling L. monocytogenes in chicken has been studied in a previous work (González-Fandos and Dominguez, 2006). It was observed that chicken legs treated with 5% lactic acid showed a significant inhibitory effect on L. monocytogenes, although colour was negatively affected. (González-Fandos and Dominguez, 2006).

In a previous work, the efficacy of potassium sorbate against L. monocytogenes in chicken meat was investigated (González-Fandos and Dominguez, 2007). It was observed that treatment with 5% potassium sorbate reduced L. monocytogenes counts.

Washing with organic acid combinations has been reported as being effective in reducing bacterial counts in pork (Reynolds and Carpenter, 1974). The effect of different organic acid combinations (lactic/citric) on microbial quality of poultry were studied by Zhu et al. (2016). Combinations of lactic and acetic acid were reported as being effective in controlling Salmonella in poultry (Ramirez et al., 2018). However, few authors have investigated the effect of mixtures of organic acids in washing solutions to combat L. mococytogenes on meat (Dubal et al., 2004).

The increased consumer preference for fresh foods has led to the use of modified atmosphere packaging (MAP) as a technique to extend the shelf life of various foods including chicken (Chmiel et al., 2018; McMillin, 2008). Nevertheless, there is a great concern about the microbiological safety of MAP products because of the ability of L. monocytogenes to grow, due to this bacteria being a facultative anaerobe (McMillin, 2008). L. monocytogenes are able to grow on MAP foods before spoilage becomes evident. Therefore, additional measures have had to be addressed in MAP foods in order to control L. monocytogenes.

The combined effects of mixtures of organic acids and modified atmospheres on L. monocytogenes in chicken meat have scarcely been investigated. Some studies deal solely with the effect of a single organic acid along with packaging under modified atmospheres (Elliot et al., 1985; Zeitoun and Debevere, 1991).

This study was undertaken to evaluate the effectiveness of different mixtures of lactic acid and potassium sorbate against L. monocytogenes on fresh chicken legs packaged under modified atmospheres and stored at 4 °C.

Section snippets

Preparation of bacterial inoculum

The L. monocytogenes serotype 1/2a strain CECT 932 was grown in Tryptone Soya Broth (Oxoid, Hampshire, UK) at 30 °C for 18h to achieve a viable cell population of 9 log cfu/ml. The culture was then transferred to a sterile centrifuge bottle and centrifuged at 10000g for 10 min at 4 °C. The supernatant was decanted and the pellet resuspended in sterile 0.1% peptone solution (Merck, Darmstadt, Germany) (pH 6.2) by vortexing. The washing step was repeated twice. The suspension of washed cells was

Modified atmosphere packaging

The effect of packaging in modified atmospheres on mesophile and psychrotroph counts can be seen in Fig. 1a and b, respectively. Significant differences (p < 0.05) in mesophile counts were found between the legs packaged in 20%CO2/80%N2 (oxygen free) (Batch A1) and the control legs packaged in air (Batch AC), except on days 0 and 10. No significant differences (p > 0.05) in mesophile counts were observed in legs packaged in 10%O2/20%CO2/70%N2 (Batch A2) compared to the control ones (Batch AC).

Discussion

Different modified atmospheres have been used for meat and poultry packaging. In order to maintain the color of meat, oxygen concentration between 5 and 13% has been recommended. Although, atmospheres containing 20–40% of CO2 and 80-60% N2 are normally used in the packaging of fresh chicken, atmospheres containing oxygen have also been applied (McMillin, 2008). The main reason for using oxygen is to preserve the red colour in red meat. Chicken meat has a low quantity of myoglobin and is

Conclusions

Chicken legs packaged in atmospheres containing 20%CO2/80%N2, had an extended shelf life, but these atmospheres are not able to reduce L. monocytogenes, thus underlining the need for preventive measures to control this pathogen. The immersion of chicken legs in a solution containing 3.75% lactic acid- 3.75% potassium sorbate can reduce L. monocytogenes populations in fresh chicken packaged in a modified atmosphere. This treatment showed the greatest ability to increase the lag phase and reduce

Declaration of competing interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Acknowledgments

The authors would like to thank the University of La Rioja (Spain) (Project Reference PROFAI 13/24 and REGI2018/06) for its financial support.

References (39)

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