Pulsed strong light is a new non-thermal physical sterilization technology that uses instant high-intensity, broad-spectrum pulsed light from a xenon lamp to kill nutrient bacteria and spores, fungi and fungal spores, viruses and protozoa in solid surfaces, gases and transparent liquids Other spoilage pathogenic microorganisms have the advantages of low energy consumption, high sterilization efficiency, and low negative impact on product quality and nutrition.
After the input city power is boosted by the equipment transformer, the capacitor of the high-voltage DC generator is charged, and the high-voltage DC is formed through the strong light generator (both ends of the xenon lamp). A high-voltage pulse is generated by the system trigger. After the boost, the current is triggered to generate an instantaneous inductance to make the xenon gas ionize and conduct to form a flash with a very short duration. After the capacitor is discharged, the high voltage drops to accumulate energy for the next flash. The earliest commercial equipment is PureBrightTM system, currently mainly SteriBeam system in Germany and Xenon system in the United States. In my country, Zhou Wanlong, Ma Fengming, etc. independently designed PL sterilization devices for research.
The UV band is generally considered to be the main area where PL exerts its bactericidal effect, and DNA denaturation is the main cause of sterilization. Microbial DNA absorbs UV wavelengths (200 ~ 280 nm) under PL irradiation, DNA gradually begins to crack, changes in structure, and forms thymine dimers that are unfavorable to DNA, hindering DNA replication and cell division, and the microbial’s own metabolic function is impeded. , Genetic problems, leading to cell death or inactivation of spores. The most important antimicrobial effect in the UV spectrum is the UV-C band (200～275 nm). After PL flash treatment, the lyase activity of the photorepair mechanism of L. innocua still exists. The lyase activity of the photorepair mechanism depends not only on light, but also on time. Due to the transient nature of PL, the repair time obtained from the visible light portion of the PL is limited, so the photorepair of the PL is limited.
The near-infrared light in PL radiates energy, which increases the local temperature of the cell surface to 50-150 ℃, destroys the cell wall of bacteria, evaporates the cell fluid, completely destroys the cell structure, and leads to death.
In addition to photochemical and photothermal effects, PL also has photophysical effects. The penetrating and transient impact properties of PL damage cell walls and other cell components, leading to cell death.
In order to effectively extend the shelf life of fruits and vegetables, many scholars apply PL to the processing of fruits and vegetables. The results show that: PL combined with different treatment methods can maximize the shelf life.
PL can also be applied to the photodegradation of pesticide residues in fruits and vegetables. Due to the short-term nature of PL, high pulses prevent the formation of substances required for harmful by-product derivatives, so PL can be applied to the degradation of agricultural residues.
Fresh-cut fruits and vegetables are favored by consumers because of their convenience. PL can effectively reduce microorganisms and inactivate enzyme activity. The application of PL to the preservation of fruits and vegetables should control the irradiation dose within a certain range. While reducing microorganisms, inactivating enzyme activity and extending shelf life, it is also necessary to prevent high pulse doses from causing browning and other unfavorable factors.
In addition to ensuring the safety of fruits and vegetables, PL is also beneficial to improve the quality of fruits and vegetables, such as increasing the content of resveratrol in grapes and mushrooms, and the non-enzymatic antioxidant activity in mangoes.
The above information is provided by the pulse light sterilization equipment supplier.