عنوان

Meyve suyu pastörizasyonu için UV ışık yayan diyotların etkinliğinin (UV-LED) değerlendirilmesi

TLpq2524375293

انگلیسی

Meyve suyu pastörizasyonu için UV ışık yayan diyotların etkinliğinin (UV-LED) değerlendirilmesi

[Thesis]

Akgün, Merve

Ünlütürk, Sevcan

Izmir Institute of Technology (Turkey)

2019

170

Ph.D.

Izmir Institute of Technology (Turkey)

2019

The objectives of this thesis are to evaluate the application of ultraviolet light emitting diodes (UV-LEDs) with various wavelengths for pasteurization of cloudy (CAJ) and clear apple juices (AJ), to assess the disinfection efficiency of combined UV-LED irradiation and mild heat (UV-LED+MH) treatments, to investigate the effect of individual and combined processes on the activity of enzyme, physicochemical and microbiological quality of AJ, to determine the shelf life of UV-LED irradiated juice during storage, to reveal the reactivation potential of target microorganism (E. coli K12) in juice medium with different optical properties, and to elucidate the mechanism of microbial inactivation by UV-LEDs. 280/365 nm UV-LED irradiation assisted by mild heat at 55ºC and 15 min exposure time enhanced the inactivation of E. coli K12 and polyphenoloxidase and satisfied the 5-log reduction pasteurization criterion in apple juice. UV-LED+MH treatment extended the shelf life of CAJ from 3 to 30 days and increased its total phenolic content. However, the color properties were slightly affected by ultraviolet treatment. Subsequent photoreactivation of E. coli K12 after inactivation by UV-LEDs was observed in both CAJ and AJ. Contrarily, dark repair was repressed at 4ºC and 22ºC, furthermore, a decrease in the survival ratio was recorded in both medium. It was revealed that the damage of DNA repair enzymes and the proteins that form the outer cellular membrane of bacteria was highly induced by UV-C light at 280 nm. Additionally, the bactericidal effect of 365 nm (UV-A) wavelength was attributed to enhanced production of reactive oxygen species (ROS) resulting in oxidative damage to cellular lipids, proteins and DNA. The combination of these two wavelengths provided more efficient disinfection than that of UV-C light used alone. UV-LED irradiation assisted by mild heat has a potential to be used as an alternative technique to traditional thermal pasteurization process for juice products. This study leads to useful information for the future design of UV-LED treatment systems.

Food science

Fruit juices

Light emitting diodes

Pasteurization

Ultraviolet radiation

Akgün, Merve

Ünlütürk, Sevcan

p

[Thesis]

276903

a

Y