Disinfection of Iceberg Lettuce by Titanium Dioxide–UV Photocatalytic Reaction

Abstract

Securing the physical quality and microbial safety of fresh foods has been a major focus in the food industry. To improve quality and increase the shelf life of fresh produce, disinfection methods have been developed. Titanium dioxide (TiO2) photocatalytic reactions under UV radiation produce hydroxyl radicals that can be used for disinfection of foodborne pathogenic bacteria. We investigated the effects of TiO2-UV photocatalytic disinfection on the shelf life of iceberg lettuce. Counts of natural microflora (total aerobic bacteria, coliforms, psychrotrophic bacteria, and yeasts and molds) and inoculated pathogenic bacteria (Escherichia coli, Listeria monocytogenes, Staphylococcus aureus, and Salmonella Typhimurium) on iceberg lettuce were determined after 20-min treatments with TiO2-UV, UV radiation, a sodium hypochlorite (NaOCl) solution, and tap water. TiO2-UV treatment reduced the number of microorganisms by 1.8 to 2.8 log CFU/g compared with reductions of 0.9 to 1.4 and 0.7 to 1.1 log CFU/g obtained with UV radiation and NaOCl treatments, respectively. Treatment with tap water was used as a control and resulted in no reductions. Counts of microflora for iceberg lettuce at 4 and 25 degrees C were determined during a 9-day period. TiO2-UV treatment resulted in 1.2- and 4.3-log increases in the counts of total aerobic bacteria at 4 and 25 degrees C, respectively, compared with 1.3- to 1.6-log and 4.4- to 4.8-log increases due to UV radiation and NaOCl treatments.

Listeria monocytogenes Behaviour in Presence of Non-UV-Irradiated Titanium Dioxide Nanoparticles

“…So far, the only studies about TiO 2 NPs and L. monocytogenes concerned the photocatalytic activity of TiO 2 NPs against bacteria, as alternative means of disinfecting surfaces or food contaminated by planktonic or biofilm bacteria [24] [25] [26] [27]. Since no data yet are available on the effects of non UV-irradiated TiO 2 nanoparticles on listeria cells, the aim of present study was to explore interaction between bacteria and nano-sized TiO 2 , with special focus on biofilm formation and CaCo-2 cell colonization.…”

Effects of TiO2–UVC photocatalysis and thermal pasteurisation on microbial inactivation and quality characteristics of the Korean rice‐and‐malt drink sikhye

“…Kim et al . () reported that TUVP processing reduced counts of natural microflora and inoculated pathogenic bacteria on iceberg lettuce immediately after treatment, as well as during storage at different temperatures, and prolonged the product shelf life. Gündüz et al .…”

Inactivation of pathogenic bacteria inoculated onto a Bacto™agar model surface using TiO2-UVC photocatalysis, UVC and chlorine treatments

“…a) following a previous study (Kim et al . ). The reactor consisted of a stainless steel vessel (30 l), an air pump and six UVC lamps (254 nm, 35 W, 25 mW cm −2 , Sankyo Denki, Tokyo, Japan) in TiO 2 ‐coated quartz tubes (38 cm length, 24·5 mm outer diameter, TiO 2 coating thickness 0·7–0·9 mm; Taekyeong UV Co., Namyangju, South Korea).…”

“…The use of chlorinated water that may be insufficient for inactivation of all bacterial pathogens can cause health hazards due to generation of trihalomethanes (Kim et al . , ) and can also result in undesirable by‐products and, at the same time, create disposal problems. Treated products may also require water rinsing before use to remove residual chlorine.…”