Biodegradable gelatin-based films with nisin and EDTA that inhibit Escherichia coli.

Romina L Abarca,Bernardo Carrillo López,Javiera Medina,Pablo A Ortiz,Nancy Alvarado,Marcos Pileggi

doi:10.1371/journal.pone.0264851

Abstract

In this study, we developed gelatin-based films for active packaging with the ability to inhibit E. coli. We created these novel biodegradable gelatin-based films with a nisin-EDTA mix. FT-IR, TGA, and SEM analysis showed that nisin interacted with the gelatin by modifying its thermal stability and morphology. The use of nisin (2,500 IU/mL) with concentrations of Na-EDTA (1.052 M stock solution) distributed in the polymer matrix generated a significant decrease in the growth of E. coli when compared to the control. In freshly made films (t0), the growth of E. coli ATCC 25922 was reduced by approximately 3 logarithmic cycles. Two weeks after the films were made, a reduction in antimicrobial activity was observed in approximately 1, 1 and 3 logarithmic cycles of the films with 5%, 10% and 20% of the compound (nisin/Na-EDTA) distributed in the polymer matrix, respectively. This evidences an antimicrobial effect over time. Also, biodegradation tests showed that the films were completely degraded after 10 days. With all these results, an active and biodegradable packaging was successfully obtained to be potentially applied in perishable foods. These biodegradable, gelatin-based films are a versatile active packaging option. Further research on the barrier properties of these films is needed.

Highlights

One of the major challenges for the food industry, for the perishable food processing industries—such as the meat and dairy industries—is conservation, that is, avoiding the proliferation of microorganisms that break down food, generating economic losses and serious damage to consumers’ health
Sangcharoen et al [36] reported similar results against Salmonella enteritidis ATCC 13076 when combining the same concentrations based on the active agent; in this regard, it is relevant to consider that Salmonella enteritidis is a Gram-negative microorganism, which shows the effectiveness of Na-EDTA as an agent that enhances the activity of nisin
Active films for inhibiting Escherichia coli were successfully obtained after the incorporation of nisin into the gelatin films, as a significant antimicrobial effect was found through in vitro assays

Summary

Introduction

One of the major challenges for the food industry, for the perishable food processing industries—such as the meat and dairy industries—is conservation, that is, avoiding the proliferation of microorganisms that break down food, generating economic losses and serious damage to consumers’ health. Given its high perishability condition caused by its high water content, it requires different processes for its conservation that, over time and depending on technological availability, have been changing and improving its shelf life [3, 4]. Some products are handled under poor hygiene standards; the presence of this microorganism in meat and meat products indicates a deficiency in the quality assurance program [6]. This last microorganism is one of the most recurrent concerning contaminations within the meat industry [7–9]. The need for improving preservation and extend the shelf life of food has led to the need for innovating through a new packaging concept: active packaging. The active components of the container can generate changes at the organoleptic or chemical level, so it’s fundamental to take care that it remains within the regulations of each country [13]

Methods

Results

Discussion

Conclusion