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    Predictive modelling for the growth kinetics of Pseudomonas spp. on button mushroom (Agaricus bisporus) under isothermal and non-isothermal conditions
    (Elsevier, 2020) Tarlak, Fatih; Ozdemir, Murat; Melikoglu, Mehmet
    Baranyi model was fitted to experimental growth data of Pseudomonas spp. on the button mushrooms (Agaricus bisporus) stored at different isothermal conditions (4, 12, 20 and 28 degrees C), and the kinetic growth parameters of Pseudomonas spp. on the button mushrooms were obtained. The goodness of fit of the Baranyi model was evaluated by considering the root mean squared error (RMSE) and the adjusted coefficient of determination (adjusted-R-2). The Baranyi model gave RMSE values lower than 0.193 and adjusted-R-2 values higher than 0.975 for all isothermal storage temperatures. The maximum specific growth rate (mu(max)) was described as a function of temperature using secondary models namely, Ratkowsky and Arrhenius models. The Ratkowsky model described the temperature dependence of mu(max) better than the Arrhenius model. Therefore, the differential form of the Baranyi model was merged with the Ratkowsky model, and solved numerically using the fourth-order Runge-Kutta method to predict the concentration of Pseudomonas spp. populations on button mushrooms under non-isothermal conditions in which they are frequently subjected to during storage, delivery and retail marketing. The validation performance of the dynamic model used was assessed by considering bias (B-f) and accuracy (A(f)) factors which were found to be 0.998 and 1.016, respectively. The dynamic model developed also exhibited quite small mean deviation (MD) and mean absolute deviation (MAD) values being - 0.013 and 0.126 log CFU/g, respectively. The modelling approach used in this work could be an alternative to traditional enumeration techniques to determine the number of Pseudomonas spp. on mushrooms as a function of temperature and time.
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    The combined effect of exposure time to sodium chlorite (NaClO2) solution and packaging on postharvest quality of white button mushroom (Agaricus bisporus) stored at 4 °C
    (Soc Brasileira Ciencia Tecnologia Alimentos, 2020) Tarlak, Fatih; Ozdemir, Murat; Melikoglu, Mehmet
    Agaricus bisporus was washed with 1 g/L sodium chlorite (NaClO2) (SC) solution for 30, 60 and 120 s, packed with a non-perforated polyvinyl chloride (PVC) film and stored at 4 degrees C for 12 days. Washing the mushrooms with the SC solution and packaging with the PVC film slowed down the change in colour and firmness of the mushrooms, but treating the mushrooms with the SC solution longer than 60 s adversely affected the mushroom texture. After 12 days of storage, the weight loss of the mushrooms packed with the PVC film was less than 10% compared to the control. Headspace O-2 concentration decreased while CO2 concentration increased throughout 12 days of storage and reached about 15% and 4%, respectively. Pseudomonas spp. counts for unwashed and unpacked mushrooms reached 10.30 log 10 CFU/g after 12 days of storage while the mushrooms washed with the SC solution and packaged with the PVC film had Pseudomonas spp. counts as low as 6.62 log 10 CFU/g. Treating the mushrooms with the SC solution for 60 s and packaging with the PVC film were found to be the most appropriate treatment to minimize the change on the postharvest quality of white button mushroom.