Effectiveness of blue light-emitting diode illumination in the inactivation of histamine-producing bacteria

• Main Authors: CHEN, YI-YIN, 陳乙尹
• Other Authors: HUANG, YU-RU
• Format: Others
• Language: zh-TW
• Published: 2019
• Online Access: http://ndltd.ncl.edu.tw/handle/5w65hf

碩士 === 國立澎湖科技大學 === 食品科學系碩士班 === 107 === Scombroid poisoning is a food-borne intoxication caused by the consumption of seafood containing a relatively high histamine content; this intoxication has been reported worldwide. Visible light-emitting diodes (LEDs) that have antibacterial effects afford a novel method for food preservation. Nevertheless, little information is available on the effectiveness of blue LEDs (470 nm) in the inactivation of various histamine-producing bacteria. The objective of this study was to evaluate the antibacterial effects of blue LEDs on Enterobacter aerogenes, Morganella morganii, Raoultella ornithinolytica, and Staphylococcus capitis and on histamine formation. A blue LED light source providing a photosynthetic photon flux density of 430 µmol/m2/s was used for illumination. Bacterial cultures suspended in 1% L-histidine (TSBH) tryptic soy broth were illuminated by 0.38 mW/cm2 blue LEDs at a distance of 4.5 cm at 10, 20, and 30 °C for 12 h. The initial suspension culture of M. morganii (5 log CFU/ml) was almost completely inactivated to <1 log CFU/ml. However, regarding the photodynamic inactivation of bacteria, blue LEDs exerted only slight effects on E. aerogenes, R. ornithinolytica, and S. capitis in that they resulted in only 0.73-1.29 and 0.93-2.75 log CFU/ml reductions in the bacterial populations after 12 h at 10 and 20 °C, respectively. Bacterial cultures (3 log CFU/ml) suspended in TSBH broth were also illuminated by 0.38 mW/cm2 blue LEDs at a distance of 4.5 cm at 30±2°C. The bacterial populations significantly increased to 7.53–8.64 log CFU/ml, but illumination with blue LEDs could significantly inhibit histamine formation. These results thus demonstrate that the antibacterial effect of the LEDs was highly dependent on the bacterial species, illumination time, and temperature. In addition, the blue LEDs exhibited enhanced antibacterial effects under acidic (pH 4.5) and alkaline pH (pH 9.5) condition. Moreover, 0.25% lactic acids at pH 4.5 combined the blue LEDs illumination have synergistic effect to greatly enhance the photodynamic inactivation (PDI) efficacy. Since gallic acid is a food ingredient, it’s supposed to be safe for humans. The objective of this study was to investigate the antibacterial effect of the 470 nm LEDs illumination with 24 mmole gallic acid at 30±2°C for 12 h at pH 6.0 on E. aerogenes. The population of E. aerogenes reached below 1 log CFU/ml to detection limit within 8 h. The results of this study elucidate the effectiveness of blue LEDs (470 nm) in inhibiting histamine formation and thus demonstrate their suitability as a novel method for reducing the risk of histamine poisoning. When a commercial blue LEDs clamp was used (0.46 mW/cm2) 5.01 J/cm2 inactivated 2.61-4.75 log CFU/25 cm2 of the E. aerogenes on Polypropylene cutting board, Wood cutting board, Basic white ceramic tile, and stainless steel. These results indicate that routine use of blue LEDs during food processing would provide workers and consumers some protection against histamine fish poisoning.