Use of Gamma Radiation to Inactivate Stressed Salmonella Spp., Escherichia Coli O157:H7 and Listeria Monocytogenes in Tahini Halva T
Total Page:16
File Type:pdf, Size:1020Kb
LWT - Food Science and Technology 98 (2018) 438–443 Contents lists available at ScienceDirect LWT - Food Science and Technology journal homepage: www.elsevier.com/locate/lwt Use of gamma radiation to inactivate stressed Salmonella spp., Escherichia coli O157:H7 and Listeria monocytogenes in tahini halva T ∗ Tareq M. Osailia,b, , Anas A. Al-Nabulsia, Taqwa F. Aljaafreha, Amin N. Olaimatc a Department of Nutrition and Food Technology, Faculty of Agriculture, Jordan University of Science and Technology, Irbid 22110, Jordan b Department of Clinical Nutrition and Dietetics, College of Health Sciences, University of Sharjah, Sharjah, United Arab Emirates c Department of Clinical Nutrition and Dietetics, Faculty of Allied Health Sciences, Hashemite University, Jordan ARTICLE INFO ABSTRACT Keywords: Tahini halva or its major ingredient, tahini, have been implicated in several foodborne outbreaks in Europe and Irradiation USA. The aim of the study was to i) assess the effect of desiccation and heat stresses on the sensitivity of Tahini halva Salmonella spp., Listeria monocytogenes and Escherichia coli O157:H7 in tahini halva to gamma radiation, and ii) Low water activity evaluate effect of irradiation on chemical (acid, peroxide, and p-anisidine values) and physical (color) char- Foodborne pathogens acteristics of the product. Tahini halva samples were inoculated with fresh, desiccation stressed or heat stressed Stresses cocktail cultures of the tested microorganisms separately then exposed to gamma radiation at doses of 0–4 KGy to determine D10-value. Desiccation stress decreased the resistance ratio of Salmonella and L. monocytogenes toward gamma radiation to 0.85 and 0.73; respectively, compared to unstressed cells, while it did not affect the resistance of E. coli O157:H7. On the other hand, heat stress increased the resistance ratio of E. coli O157:H7 and L. monocytogenes to 1.14 and 1.18, respectively. However, the resistance ratio of heat stressed Salmonella was significantly reduced to 0.9. Irradiation dose of 4.0 KGy did not affect significantly the color and acid value whereas, peroxide and p-anisidine values increased significantly as the irradiation doses increased. 1. Introduction (CDC), 2013). Contamination of these products may occur from raw materials or during production, filling and storage from workers, In the recent years, low water activity (aw) foods have been im- equipment and processing environment (Kahraman et al., 2010; World plicated in several foodborne diseases and food recalls, although these Health Organization WHO, 2008). Furthermore, it has been found that food products are unable to support the microbial growth (Beuchat Salmonella can survive the roasting process of sesame seeds if the seeds et al., 2013). An example of these products is tahini halva which is a are at low aw (Zhang, Keller, & Grasso-Kelley, 2017). Therefore, it is popular traditional confectionery ready-to-eat product and mainly important to apply a further process such as irradiation to eliminate consumed in the Middle East, Mediterranean, North Africa and Balkan foodborne pathogens in the fragile, brittle texture of tahini halva. Io- regions (Öğütcü, Arifoğlu, & Yilmaz, 2017; Kahraman, Issa, Ozmen, & nizing radiation could be a potential method for inactivation of food- Buyukunal, 2010). However, the consumption of tahini halva or it's borne pathogens in tahini halva as it can be applied on packaged pro- major ingredient, tahini (sesame seeds paste), have increased in other ducts without rising product temperature or changing product quality countries including USA and European countries due to their high nu- (Ban & Kang, 2014; Farkas, 2006; Osaili, Al-Nabulsi, Abubakar, tritional value and health properties (Narasimhulu, Selvarajan, Alaboudi, & Al-Holy, 2016). Litvinov, & Parthasarathy, 2015; Research & Markets, 2017). In gen- Recently, irradiation has become one of the most effective tech- eral, tahini halva composed of > 45% tahini, 45–55% sugar, < 2% ash nologies to control foodborne pathogens, and extend shelf-life of food and < 2.5% moisture (World Health Organization WHO, 2008). products. It has been approved to control foodborne pathogens in meat, Tahini halva and tahini have a low aw level of ca. 0.19 with a long poultry, fresh fruits, vegetables and spices (Food and Drug shelf life up to 2 years at ambient temperature. However, these products Administration (FDA), 2009). Moreover, it has been found that ionizing have been linked to foodborne outbreaks, particularly salmonellosis radiation is effective against E. coli O157:H7 and Salmonella in tahini diseases (Unicomb et al., 2005; Centers for Disease Control and (Osaili & Al-Nabulsi, 2016; Osaili et al., 2016). Food composition is one Prevention (CDC), 2012; Centers for Disease Control and Prevention of the main factors that affects microorganism's resistance toward ∗ Corresponding author. Department of Nutrition and Food Technology, Faculty of Agriculture, Jordan University of Science and Technology, Irbid 22110, Jordan. E-mail addresses: [email protected], [email protected] (T.M. Osaili). https://doi.org/10.1016/j.lwt.2018.09.017 Received 31 March 2018; Received in revised form 14 July 2018; Accepted 9 September 2018 Available online 10 September 2018 0023-6438/ © 2018 Elsevier Ltd. All rights reserved. T.M. Osaili et al. LWT - Food Science and Technology 98 (2018) 438–443 ionizing radiation (Osaili, Shaker, Abu Al-Hasan, Ayyash, & Martin, divided into 25 μL portions in a sterile Petri dish and placed without a 2007; Osaili et al., 2008b; Osaili et al., 2016). Osaili et al. (2007) found lid, in a biosafety cabinet for 2 h. After that, the desiccated cells were that chemical composition and aw of the medium affected the irradia- collected from the plate by adding 10 ml of potassium phosphate buffer tion resistance of Cronobacter sp. They found that Cronobacter sp. were (PPB) (0.1M, pH 6.8) into the plate. The PPB was moved over the entire more resistant to ionizing radiation in rehydrated infant milk formula plate several times to collect the cells. than in brain heart infusion broth due to the presence of fat, proteins and carbohydrates. In addition, they found that Cronobacter sp. were 2.2.2. Heat stress more resistant in dehydrated infant milk formula than rehydrated in- For Salmonella and E. coli O157:H7, heat stressed culture was pre- fant milk formula due to low aw level of the dried formula. pared as described by Gurtler and Beuchat (2005). One milliliter of a In general, pathogens may be exposed to a variety of sublethal en- freshly prepared cocktail culture of each pathogen was added to 9 ml of vironmental stresses such as heat, pressure, radiation or osmotic shocks, sterile PPB in a 15 ml screw-cap test tube which was placed and the addition of chemicals like acids, salts, and oxidants or biological maintained then at 50 °C in a shaking water bath (Jeio Tech, Seoul, stresses as competition, microbial metabolites and antagonism during Korea). After 10 min, the test tube was removed and cooled im- harvesting, processing and storage of food products, which may affect mediately under running tap water. Whereas, heat stressed L. mono- their response to subsequent treatments such as irradiation (Osaili cytogenes was prepared as described by Lou and Yousef (1997). L. et al., 2008a, 2008c; Yousef & Courtney, 2003). For example, Osaili monocytogenes cocktail culture was placed in a shaking water bath at et al. (2016) found that cold stress increased Salmonella susceptibility to 45 °C for 1 h and cooled with tap water. irradiation in tahini, while heat and starvation stresses did not affect behavior of Salmonella toward irradiation. In another study, Osaili and 2.3. Sample preparation and inoculation Al-Nabulsi (2016) reported that heat, cold, salt, acid, alkaline and ethanol stresses significantly reduce the E. coli O157:H7 resistance to Tahini halva mixed with pistachio samples produced within 2 irradiation in tahini. However, no information is available on the effect months before the time of experiments were purchased from a local of environmental stresses on irradiation of halva. Therefore, the ob- market in Amman, Jordan. The chemical composition of the tested jectives of the current study were to (i) assess the effect of desiccation samples (3 different batches) is fat 35.6% ± 0.13, protein and heat stresses on the sensitivity of Salmonella spp., Listeria mono- 15.92% ± 0.06, ash 1.98% ± 0.01, moisture 1.64% ± 0.16 and aw cytogenes and Escherichia coli O157:H7 in tahini halva to gamma irra- 0.18 ± 0.01. Tahini halva samples checked to be free of Salmonella, E. diation and (ii) investigate the effect of irradiation on the chemical coli O157:H7, and L. monocytogenes before the experiments. Inoculation (acid, peroxide, and p-anisidine values) and physical (color) char- of tahini halva samples was performed as described by Osaili. Al- acteristics of tahini halva. Nabulsi, Nazzal, & Shaker (2017). The samples (100 g) were mashed and spread on a sterile tray (diameter 30 cm) then 1 ml of unstressed, 2. Materials and methods desiccation stressed or heat stressed cocktail cultures were inoculated into the sample by spraying method using a thin layer chromatography 2.1. Bacterial strains and culture preparation sprayer and mixed very well with a sterile spatula to obtain an initial inoculation level of 106–107 CFU/g. Inoculated tahini halva was di- Four strains of each of Salmonella spp. (S. Typhimurium T123, S. vided into 10-g samples which were placed in sterile stomacher bags Typhimurium T231, S. Aberdeen T069, S. Cubana T109) isolated from pressed by hand to remove air, and heat sealed. tahini and tahini halva samples, mutated E. coli O157:H7 (00:3581, 02:0304, 02:0627, 02:0628) and L. monocytogenes (Lm 023, Lm 075, Lm 2.4. Gamma radiation 120, Lm 190) isolated from food items (foul, falafel, salad and mashed potato) were used in this study. The cultures were kept at −40 °C in Tahini halva samples were exposed to gamma radiation in a re- Brain Heart Infusion (BHI, Oxoid Ltd, Basingstoke, UK) Broth with 20% search gamma unit (Gamma-facility PX-γ −30, Issledovatelj, glycerol.