The Effect of Pulsed Electric Fields (PEF) Combined with Temperature and Natural Preservatives on the Quality and Microbiological Shelf-Life of Cantaloupe Juice.

Li Li,Ruijin Yang,Wei Zhao

doi:10.3390/foods10112606

Abstract

Pulsed electric field (PEF) is an innovative, non-thermal technology for food preservation with many superiorities. However, the sub-lethally injured microorganisms caused by PEF and their recovery provide serious food safety problems. Our study examined the effects of pH, temperature and natural preservatives (tea polyphenols and natamycin) on the recovery of PEF-induced, sub-lethally injured Saccharomyces cerevisiae cells, and further explored the bactericidal effects of the combined treatments of PEF with the pivotal factors in cantaloupe juice. We first found that low pH (pH 4.0), low temperature (4 °C), tea polyphenols and natamycin inhibited the recovery of injured S. cerevisiae cells. Then, the synergistic effects of PEF, combined with cold-temperature storage (4 °C), a mild treatment temperature (50 and 55 °C), tea polyphenols or natamycin, on the inactivation of S. cerevisiae in cantaloupe juice were evaluated. Our results showed that the combination of PEF and heat treatment, tea polyphenols or natamycin enhanced the inactivation of S. cerevisiae and reduced the level of sub-lethally injured cells. Moreover, PEF combined with 55 °C heat treatment or tea polyphenols was applied for cantaloupe juice. In the practical application, the two combined PEF methods displayed a comparable inactivation heat pasteurization ability, prolonged the shelf life of juice compared with PEF treatment alone, and better preserved the physicochemical properties and vitamin C levels of cantaloupe juice. These results provide valuable information to inhibit the recovery of PEF-injured microbial cells and shed light on the combination of PEF with other factors to inactivate microorganisms for better food preservation.

Highlights

There is a growing interest in the applications of non-thermal technologies in food processing and preservation, which display a good capacity for microbial inactivation and can save the natural nutritional and sensory properties of foods [1,2,3]
Our results showed that the combination of pulsed electric field (PEF) and heat treatment, tea polyphenols or natamycin enhanced the inactivation of S. cerevisiae and reduced the level of sub-lethally injured cells
The results indicate that S. cerevisiae cells are sensitive to a low pH, and the PEF resistance of the tested strain depends on the pH of the treatment medium

Summary

Introduction

There is a growing interest in the applications of non-thermal technologies in food processing and preservation, which display a good capacity for microbial inactivation and can save the natural nutritional and sensory properties of foods [1,2,3]. The pulsed electric field (PEF), as an innovative non-thermal technology, has been investigated in a wide range of fields, including food preservation, undesirable enzyme deactivation and an improvement in juice extraction yield [1,4,5]. It exhibits many advantages for food preservation and quality improvement, especially for the preservation of liquid foods containing heat-sensitive nutrients [4,5]. Electroporation of microbial cell membranes has been regarded as a main reason for microbial inactivation by PEF treatment [7]. The repair of sub-lethal membrane damage in Escherichia coli cells after

Methods

Results

Conclusion