# Applications of Pulsed Light Decontamination Technology in Food Processing: An Overview
## 5 Role of Pulsed Light Technology in Food Safety
### Microbial Decontamination in Food Products
Exposure to PL of fluence levels of 2.1 J/cm\({}^{2}\) led to inactivation of Salmonella cells (5 log reductions per eggshell) on the egg surface [89]. [PERSON] et al. [63] performed PL treatment of shell eggs using 12 J/cm\({}^{2}\) fluence. They obtained about 2.49 log reduction of _S._ Enteritidis on eggshell. The discrepancy between the results of the latter in spite of using higher fluence could be due to the employment of different cell recovery methods after treatment. [PERSON] et al. [89] used a shell rinse method for recovery of cells from shell surface, while [PERSON] et al. [63] used the shell crush method, indicating the former to be an inefficient cell recovery method [124]. Nevertheless, solid foods ranging from fruits, vegetables, and poultry to marine products have been treated successfully by PL. However, surface irregularities remain a challenge for their decontamination. Liquid sample treatment with PL is more challenging because microorganisms dwell in the whole volume of liquids. So, PL efficacy is particularly based on several factors like sample distance from lamp, exposure, turbidity, and optical and physicochemical properties of the sample, as well as sample depth [16; 110]. A higher exposure time of liquid food leads to higher inactivation. Also, the sample distance from lamp determines treatment efficiency, i.e., lower the distance, the better Optical properties like transparency, and turbidity affect the PL efficacy. Turbid liquid foods might hinder process efficiency because of light scattering. On the other hand, transparent liquids like clear juices are treated by PL efficiently [23]. [PERSON] et al. [125] treated water using PL at 0.25 J/cm\({}^{2}\) and obtained reductions in bacteria _Klebsiella terrigena_ of more than 7.4 logs, and in viruses (Poliovirus and Rotavirus) and parasite (_Cryptosporidium parvum_) of above 4 logs. Milk was shown to be effectively treated by the exposure of 56 s to PL at a dose of 25.1 J/cm\({}^{2}\)[77]. _S. aureus_ was reduced by 7.26 logs at 1.27 J/cm\({}^{2}\) when subjecting milk to PL treatment [52]. This shows that the higher fluence values required for opaque food like milk as compared to water. Food composition also affects the PL processing. [PERSON] et al. [95] carried out PL treatment of milk (concentrated milk, whole milk, skim milk) and showed that PL efficiency decreased as the content of milk fat and total solids increased. They obtained highest inactivation for skim milk and concluded that the presence of milk fat scattered light by fat globules. Other liquid foods like Apple juice and orange juice (inoculated with _E coli_ DH5-\(\alpha\) and _L. innocua_ 11,288) were subjected to continuous PL system with fluence of 4 J/cm\({}^{2}\)[88]. They the inactivation levels of 4.00 and 2.90 log reductions respectively in apple and orange juices for _Escherichia coli_. Similarly, 2.98 and 0.93 logs for _L. innocua_ were obtained for apple and orange juices, respectively. Higher turbidity and cloudiness in orange juice lowered the microbial inactivation by PL. [PERSON] and [PERSON] [24] obtained 0.97 log reductions of _C. sporogenes_ spores inoculated in 2 mm depth of honey after 135 pulses intense PL treatment of 5.6 J/cm\({}^{2}\) per pulse. They concluded that microbial inactivation increased by varying the process parameters (lamp distance, number of pulses, sample depth), but complete inactivation was not achieved due to poor penetration of pulsed UV system in honey. Thus, the depth of liquid foods too affects the PL treatment. As light energy decreases with depth, thin film or profiles are suitable for PL processing. The physico-chemical properties like viscosity and density affect the flow properties of liquid foods and thus have to be considered while designing a continuous PL treatment system for them. Nevertheless, most of the studies show that PL is equally efficient and has great potential for the processing of several liquid foods.