Thermal inactivation kinetics of hepatitis A virus in spinach Hayriye Bozkurt, Xiaofei Ye, Federico Harte, Doris H. D'Souza ⁎, P. Michael Davidson Department of Food Science and Technology, The University of Tennessee, 2600 River Drive, Knoxville, TN 37996-4591, USA abstract article info Article history: Received 9 June 2014 Received in revised form 10 October 2014 Accepted 12 October 2014 Available online 22 October 2014 Keywords: Spinach Thermal inactivation D and z values Arrhenius activation energy Leafy vegetables have been recognized as important vehicles for the transmission of foodborne viral pathogens. To control hepatitis A viral foodborne illness outbreaks associated with mildly heated (e.g., blanched) leafy vegetables such as spinach, generation of adequate thermal processes is important both for consumers and the food industry. Therefore, the objectives of this study were to determine the thermal inactivation behavior of hepatitis A virus (HAV) in spinach, and provide insights on HAV inactivation in spinach for future studies and industrial applications. The D-values calculated from the first-order model (50–72 °C) ranged from 34.40 ± 4.08 to 0.91 ± 0.12 min with a z-value of 13.92 ± 0.87 °C. The calculated activation energy value was 162 ± 11 kJ/mol. Using the information gen- erated in the present study and the thermal parameters of industrial blanching conditions for spinach as a basis (100 °C for 120–180 s), the blanching of spinach in water at 100 °C for 120–180 s under atmospheric conditions will provide greater than 6 log reduction of HAV. The results of this study may be useful to the frozen food industry in designing blanching conditions for spinach to inactivate or control hepatitis A virus outbreaks. © 2014 Published by Elsevier B.V. 1. Introduction Hepatitis A virus (HAV) is the leading cause of acute viral hepatitis which may occasionally be fatal. Thus, it constitutes a serious concern for public health authorities (Coudray-Meunier et al., 2013). Even though the effectiveness of HAV vaccine is high and overall HAV cases have de- clined, outbreaks still continue to occur (Kingsley and Chen, 2009). HAV is able to replicate in the human gastro-intestinal tract and is dispersed by shedding in high concentrations into the stool. The stability of HAV with regard to several physical stresses, such as low pH and elevated tem- peratures, contributes significantly to its persistence in the environment (D'Souza et al., 2007). Transmission of these viruses occurs by the fecal– oral route, primarily through direct person-to-person contact, but they are also efficiently transmitted by ingestion of contaminated drinking water or contaminated food (D'Souza et al., 2007). The foods most likely to be contaminated by HAV are leafy vegeta- bles, fruits, shellfish and ready-to-eat foods (i.e., those with no lethality step prior to consumption) (CDC, 2014a). Gould et al. (2013) investigat- ed foodborne disease outbreaks in the United States from 1998 to 2008, and found that among individual food categories, leafy vegetables were the second most commonly reported food vehicle associated with foodborne illness, accounting for 13% of outbreaks. Leafy vegetables are often consumed raw or mildly heated (e.g., blanched) and thus may become vehicles for viral transmission if contamination occurs anywhere from farm to fork (Brassard et al., 2011). Therefore, for mildly heated leafy vegetables, such as those blanched prior to freezing, the ap- plication of a precise thermal process to inactivate HAV would improve the microbiological safety of the products. Recent foodborne outbreaks of HAV in frozen berries and pomegranate kernels also underline the need to investigate proper means to inactivate this virus in food prod- ucts that will be frozen (CDC, 2014b). In the current literature, several studies have investigated the survival of HAV in leafy vegetables such as lettuce (Bidawid et al., 2000, 2001; Croci et al., 2002; Fino and Kniel, 2008; Fraisse et al., 2011), green onions (Fino and Kniel, 2008; Laird et al., 2011; Sun et al., 2012), and parsley (Butot et al., 2008). Until now, there are lim- ited studies (Hida et al., 2013; Jones et al., 2009; Shieh et al., 2009) involving the survival of HAV in spinach. Among these studies, only Shieh et al. (2009) investigated the survival of HAV in spinach at re- frigeration temperature (5.4 ± 1.2 °C) for up to 42 days. To our knowledge, thermal inactivation kinetics of HAV in spinach has not been reported so far. The first step in designing any thermal process is defining the ther- mal resistance of the target pathogen (Solomon et al., 2002). A precise understanding of thermal inactivation kinetics is potentially useful for optimizing thermal treatments to eliminate the risk associated with foodborne pathogens while avoiding over-processing of the food mate- rial and thus resulting in optimal energy utilization. Thus, generation of correct thermal process data and establishment of proper thermal pro- cesses for inactivating HAV are important both for consumers and in- dustry. Therefore, the objective of this study was to determine the thermal inactivation behavior of hepatitis A virus in spinach in order to provide insights on HAV inactivation for future studies and industrial applications. International Journal of Food Microbiology 193 (2015) 147–151 ⁎ Corresponding author. Tel.: +1 865 974 7331; fax: +1 865 974 7332. E-mail address: ddsouza@utk.edu (D.H. D'Souza). http://dx.doi.org/10.1016/j.ijfoodmicro.2014.10.015 0168-1605/© 2014 Published by Elsevier B.V. Contents lists available at ScienceDirect International Journal of Food Microbiology journal homepage: www.elsevier.com/locate/ijfoodmicro