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  1. 1. DIFFERENT KIND OF LIGHT PULSES AND USAGE IN REAL TIME B.SURYA
  2. 2. Introduction • As the human evolution progressed, the way food being consumed and their priorities have also been evolved. The consumption of processed foods is on the rise due to change in lifestyle, particularly in urban areas. Traditional thermal-based food-processing methods such as appertization, pasteurization,and canning have been dependent on high temperature,to ensure prolonged shelf life and food safety. Although thermal processes are efficient tools for microbial inactivation, they also contribute to undesirable changes in food matrix such as structural alterationof proteins and polysaccharides, production of free radicals, affecting the functionality of food and flavour, textural softening, and destruction of colours and vitamins (Devlieghere et al., 2004).
  3. 3. • High-temperature short-time processes, electromagnetic radiation-based microwave, radio frequency heating, and ohmic heating techniques have gained focus in the recent past as alternative and rapid heating techniques to minimize the severity of heat treatment and thereby enhance product quality. • Over the past few years, consumer demand for fresh, natural, and minimally processed foods with better quality has increased. To address this, researchers are working on developing alternative techniques that not only meet the consumer demand but also energy-efficient, cost- effective, and rapid. Many novel technologies that do not involve heat processing have been developed to inactivate microorganisms
  4. 4. PL Processing • PL technology is a non-thermal technology, where decontamination of foods such as fruit juices, meat products, vegetables, and fruits is achieved by using high- intensity light pulses for a short duration of time. The PL includes a wide wavelength range of 200–1100 nm, which includes ultraviolet (UV): 200–400 nm, visible (VIS): 400–700 nm, and near-infrared region (IR): 700–1100 nm (Elmnasser et al., 2007; Palgan et al., 2011).
  5. 5. • The term pulsed light is known since 1980 and was first adopted by the US Food and Drug Administration (FDA) for food processing in 1996 (FDA, 1996). • To increase the safety of fruit and vegetable juices, US FDA regulation has implemented 5-log pathogen reduction process (US FDA, 2004). • Significant microbial reduction in very short treatment time, low environmental impact, and its high flexibility are some of the major benefits of PL (Uesugi and Moraru, 2009; Oms-Oliu et al., 2010b).
  6. 6. • Even though the PL processing is considered as ‘non- thermal’, it has the limitation of sample heating due to longer treatment time, which may cause thermal inactivation of microbes. • Significant temperature increase caused due to longer PL treatments has an extra effect on microbial reductions depending on the matrix properties (Bialka and Demirci, 2008; Huang and Chen, 2014). • PL has potential applications in food processing that requires a rapid disinfection where surface contamination is a concern for microbial contamination such as fresh whole fruit and vegetable commodities, hard cheeses or meat slices, and so on.
  7. 7. PL TreatmentSystemsfor Microbial Load Reduction • The pioneer company producing PL equipment for application in water purification systems and virus inactivation systems for biopharmaceutical manufacturers is Purepulse Technologies Inc. (San Diego, California), a subsidiary of Xenon Corp., which commercialized the PureBright™ system (Dunn et al., 1995).
  8. 8. Mode of Action of PL on Microbes • UV was the only agent responsible for the inactivation of pathogens and no antibacterial effect attributed to IR or VIS light was found (Paškevičiūtė and Lukšienė, 2009; Ramos-Villarroel et al., 2014; Kramer et al., 2015). • In addition, it has been shown that both the VIS and IR regions of PL in combination with its high peak power also contribute to the destructive effect on microorganisms (Elmnasser et al., 2007).
  9. 9. • The antimicrobial properties of UV light on bacteria are attributed to absorption of radiation by conjugated carbon–carbon double bonds in nucleic acids and proteins, and subsequent DNA structural changes (Ramos-Villarroel et al., 2012). • Cheigh et al. (2013) identified the cell damage on the foodborne pathogen, L. monocytogenes treated with UV-C and IPL with the help of transmission electron microscopy (TEM). • UV-C–treated L. monocytogenes cells were similar in structure to that of untreated cells except for a blurry and indistinct cell wall (Figure 3). • In contrast, IPL-treated cells showed the destruction of cell wall structures, cytoplasm shrinkage, and rupture of the internal organization leading to leakage of cytoplasmic content and ultimately to cell death (Cheigh et al., 2012).
  10. 10. Effect of PL on Liquid Foods • PL processing is being applied on various liquid products for decontaminatingthe foodborne pathogens that affect the human health status. • Inactivation of these pathogens on liquid food complexes are mentioned in Table 1. PL processing is influenced by various factors that dictate its efficiency on microbial inactivation, retention of quality, and other properties of the product. • Importantfactors that determine the effectiveness of PL is the fluence level applied on the sample, the amount of energy (dose or number of pulses) and wavelength of light/compositionof the spectrum (Ramos-Villarroel et al., 2012).
  11. 11. • Inactivation of microbes is higher for PL treatment with higher pulse number and higher intensity (MacGregor et al., 1998; Maftei et al., 2014; Ramos-Villarroel et al., 2014). • It is indicated that when the spectral range of the PL treatments, particularly the UV component, is altered by using filters, the inactivation of E. coli and Listeria innocua is lower (Ramos-Villarroel et al., 2012). • And among the sub-divisions of UV, UV-C–containing spectrum was more effective in inactivating B. subtilis and A.

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