Inactivation of Morganella morganii by high hydrostatic pressure combined with lemon essential oil.

Hsien-Feng Kung,Chiu-Chu Hwang,Ching-Yu Hsieh,Ying-Chuan Wu,Yi-Chen Lee,Yung-Hsiang Tsai

doi:10.1002/fsn3.1626

Abstract

The inactivation and damage of histamine‐forming bacterium, Morganella morganii, in phosphate buffer and tuna meat slurry by high hydrostatic pressure (HHP) alone or in combination with 0.2% lemon essential oil (LEO) treatments were studied using viability measurement and scanning electron microscopy (SEM). HHP alone or in combination with LEO treatments showed first‐order destruction kinetics to M. morganii during pressure holding period. The D values of M. morganii (200 to 600 MPa) in phosphate buffer ranged from 16.4 to 0.08 min, whereas those in tuna meat slurry ranged from 51.0 to 0.10 min, respectively. M. morganii in tuna meat slurry had higher D values and were more resistant to HHP treatments than in phosphate buffer. In addition, the D values of HHP in combination with LEO treatment were lower than those of HHP treatment alone at <400 MPa of pressure, indicating that it is more effective to inactivate M. morganii under the same pressure. The results showed the M. morganii at HHP in combination with LEO treatment was more susceptible to pressure treatment alone. HHP with or without LEO treatments can be used to inactivate M. morganii by causing disruption to bacterial cell membrane and cell wall as demonstrated by SEM micrographs.

Highlights

Histamine fish poisoning, or scombroid poisoning, is an allergy-like form of food poisoning resulting from consumption of mishandled scombroid fish that contains high contents of histamine (Lehane & Olley, 2000)
The first-order model fits the destruction kinetics of high hydrostatic pressure (HHP) treatment on M. morganii during the hold period, indicating that pressure destruction of M. morganii complied with the semilogarithmic model
The computed D values of M. morganii in phosphate buffer showed that HHP treatments alone had higher D values (16.4 min, 3.23 min, and 0.48 min, respectively), and more resistant, than HHP in combination with lemon essential oil (LEO) treatments (14.2 min, 3.11 min and 0.45 min, respectively) (p < .05) when treated with HHP at 200, 300, and 400 MPa (Table 1)

Summary

| INTRODUCTION

Scombroid poisoning, is an allergy-like form of food poisoning resulting from consumption of mishandled scombroid fish that contains high contents of histamine (Lehane & Olley, 2000). LEO was reported to be capable of inhibiting food-borne microorganisms such as Salmonella typhimurium, E. coli, and L. monocytogenes in media and on foods (Lin, Sheu, Hsu, & Tsai, 2010; Espina et al, 2013) It can act as a natural preservative for improving food safety and shelf life. The fish mince was blended with 0.1% peptone water (1:4, w/w) for 2 min in a blender (Omni International, Waterbury, CT, USA) Both the sterile phosphate buffer (0.1 M, pH 6.8, 99 ml) and the tuna meat slurry (99 ml) were inoculated with 1 ml of M. morganii inoculum (109 CFU/mL) to get a final bacterial population of 107 CFU/mL. The test samples were added to sterile vacuum bags in 10 ml portions, vacuum packaged and heat-sealed, and subject to HHP treatments immediately

| MATERIALS AND METHODS

| RESULTS AND DISCUSSION

| CONCLUSIONS