Application of high-pressure processing and polylactide/cinnamon oil packaging on chicken sample for inactivation and inhibition of Listeria monocytogenes and Salmonella Typhimurium, and post-processing film properties

Highlights

• High-pressure and biodegradable active packaging used for chicken meat.

• Cinnamon oil significantly enhanced the microbial inactivation.

• No revival of pathogens occur in post-process sample during storage.

• Packaging materials remained intact after high-pressure treatment.

Abstract

The synergistic effects of combined high-pressure (HP) treatment and active packaging consisting of polylactide (PLA), polyethylene glycol (PEG) and cinnamon oil (CIN) on the inactivation and inhibition of Listeria monocytogenes and Salmonella Typhimurium in chicken samples during the refrigerated storage were assessed. The target was to decrease the treatment pressure intensity of the traditional HP technology and cinnamon oil concentration so that the process becomes more economically viable. The CIN concentration was varied from 7 to 17% in the plasticized film (PLA/PEG 80/20). It was observed that the most effective treatment was the combination of a pressure treatment at a level of 300 MPa, and packaging the chicken sample in an active packaging containing 17% CIN, which reduced the population of the pathogens to a safe level during 21 days of refrigerated storage. Furthermore, the impact of HP and CIN on the thermal, rheological and mechanical properties of those films was evaluated. Time-temperature superposition principle indicated that the mechanical properties of those films remained intact after the HP-treatment, and at high temperature. Therefore, the developed films could be used for packaging of chicken samples under high-pressure, and high-temperature with maintaining the packaging integrity and the food safety at the highest level.

Introduction

Poultry meat is an important food commodity, and the production has increased significantly from 58.5 million tonnes in 2000 to about 108 million tonnes in 2013 (FAO, 2016). Among chicken meat producing countries, the US occupies the top position which accounts for 18.5% of the total world production followed by the China (16.8%) and Brazil (11.8%) (FAO, 2012). It has been projected that the poultry meat production will attain a target of 134.5 million tons in the next 10 years, and secures the top the chart among all types of meat production. The poultry meat is highly perishable, and consider is an optimum medium for the growth of microorganisms. There is a high chance of contamination with pathogens in the poultry processing units which might occur during post-processing manipulation from equipment or food handlers. Poultry meat is mostly infected by Salmonella and causes outbreaks of food-borne disease (Bryan and Doyle, 1995, Newell et al., 2010). Incidences of Listeria monocytogenes, Campylobacter jejuni, and Escherichia coli contamination in chicken are a public health issue (Altekruse et al., 1999, Anang et al., 2007, Rodrigo et al., 2005). It has been reported that Salmonella causes for 11% of illnesses, 35% of total hospitalizations, and 28% of deaths linked with foodborne illnesses each year in the US (Scallan et al., 2011).

Numerous approaches have been tested to control the growth of microorganisms during transportation and storage of the fresh poultry meat. Active packaging is one of the emerging areas where the antimicrobial agents (e.g. essential oils, nisin, nanoparticles) are embedded on the packaging materials so those agents can interact with the packaged food in a desirable way to control the growth of microbes. Essential oils (EO) which are rich in the bioactive compounds such as phenolics and terpenoids have drawn great attention due to their proven health benefits (Burt, 2004). On the other hand, the green packaging based on biodegradable materials have lesser impact on the environment. Therefore, the research in the field of developing eco-friendly packaging materials from natural polymers is on verge in order to get a partial alternative to the plastic packaging. Polylactides (PLA) is a biodegradable polymer obtained from sugar beet or corn starch, and has a commercial success in developing biomedical devices, and packaging.

A series of publication come out from our laboratory on the development of packaging materials based on plasticized PLA [using Polyethylene glycol (PEG) as a plasticizer], metallic nanoparticles (e.g. ZnO, Ag-Cu and graphene oxide), and essential oils (cinnamon, garlic, clove) either individually or in a combination. Additionally, the applicability of those composite materials have been examined for a wide range of food packaging. A complete zone of inhibition against C. jejuni was exhibited by PLA/cinnamon and PLA/clove films (PLA/PEG/CIN and PLA/PEG/CLO) at the highest concentration (1.6 mL per 2 g PLA/PEG blend) (Ahmed, Hiremath, & Jacob, 2016). It was also observed that an incorporation of 50% cinnamon oil (CIN) in the PLA-based packaging material completely inhibited the growth of L. monocytogenes and S. Typhimurium in chicken samples (Ahmed, Mulla, & Arfat, 2016). Based on our previous works, it is inferred that a complete inactivation of pathogens required a significant quantity of EO. However, a higher oil concentration has a detrimental effect on the sensory quality of the chicken sample, and it also increased the manufacturing cost substantially. To address those challenges, a combination of biodegradable antimicrobial film with a lower concentration of EO, and high-pressure processing a novel technology can be explored leading to a complete inhibition of pathogens in the chicken samples.

Inactivation of the vegetative cells including Listeria monocytogenes, Staphylococcus aureus, Escherichia coli, and Salmonella Typhimurium have been achieved through the application of HP at the pressure level of 500–600 MPa (Jofré et al., 2009, Rendueles et al., 2011). Cheah and Ledward (1997) reported that a pressure level above 300 MPa induced the lipid oxidation as well as irreversible changes including the denaturation of myoglobin in muscle proteins. Additionally, a larger change in the packaging materials including PLA and PET-based films were observed at 500 MPa for 15 min at 50 °C (Galotto, Ulloa, Guarda, Gavara, & Miltz, 2009). These studies forecast that a lower pressure level is required during the HP treatment so that the product quality as well the mechanical properties of the packaging materials can sustain. The synergistic effects of antimicrobial alginate films containing enterocins and a pressure level of 400 MPa for 10 min achieved the inactivation of L. monocytogenes and Salmonella spp. on cooked ham (Marcos, Aymerich, Monfort, & Garriga, 2008). Similarly, a combined effect of polyamide/polyethylene/coriander oil film and a pressure level of 500 MPa for 1 min caused a complete inhibition of L. monocytogenes for 60 days in ready-to-eat chicken breast samples (Stratakos, Delgado-Pando, Linton, Patterson, & Koidis, 2015). It has been reported that HP-induced sublethally injured pathogens are more susceptible to antimicrobial compounds (Kalchayanand, Sikes, Dunne, & Ray, 1994), so the use of HP-treatment in combination with active packaging could be an interesting alternative. Therefore, it is hypothesized that a combination of lower concentration of EO in PLA-based film in conjunction with lower intensity of pressure could achieve the microbial inactivation effectively with excellent quality retention of meat, and above all, augment the commercial applicability of the developed film and the HP-treatment for the poultry industry.

To date, to our knowledge the application HP-treatment and EO-based active packaging on chicken sample inoculated with both Gram-positive and Gram-negative pathogens has not been investigated. Therefore, an attempt was made to examine the potential for inactivation of L. monocytogenes and S. Typhimurium in chicken meat by high-pressure treatment combined with the PLA/cinnamon oil based active packaging, and their impact on the survival of those microorganisms at refrigerated storage for up to 21 days. Additionally, the thermomechanical properties of the films were tested before and after the pressure treatment based on the film which showed the least survival of pathogens.