Abstract
This study investigated the effects of high hydrostatic pressure (HHP) and ultraviolet radiation (UV-C), individually and combined, on the physical, chemical and bacterial parameters of Nile tilapia (Oreochromis niloticus) fillets stored at 4 °C for 14 days. Tilapia fillets were divided into four groups: control (untreated samples), UV-C, HHP, and UV-C combined with HHP (UV-C+HHP); UV-C was applied at dose of 0.103 ± 0.002 J/cm2, and HHP at a pressure of 220 MPa for 10 min at 25 °C. All samples were analyzed for total aerobic mesophilic count (TAMC), total aerobic psychrotrophic count (TAPC), Enterobacteriaceae count, pH, lipid oxidation, total volatile basic nitrogen (TVB-N), ammonia (NH3), and biogenic amines. Although UV-C accelerated (P ≤ 0.05) the formation of cadaverine, both UV-C and HHP, alone or together, retarded bacterial growth and delayed the increase (P ≤ 0.05) in pH, TVB-N, NH3 and biogenic amines during refrigerated storage, extending the shelf life of refrigerated tilapia fillets at least 2.5 times considering the TAMC counts. Lipid oxidation was unaffected (P > 0.05) by UV-C radiation, and decreased (P ≤ 0.05) by HHP and UV-C+HHP. HHP alone or combined with UV-C showed higher potential benefits for tilapia fillets preservation considering the positive influence on cadaverine levels and lipid oxidation.
Highlights
The present study investigated the effect of High hydrostatic pressure (HHP) and UV-C, individually and combined, on physical, chemical and bacterial parameters of tilapia (Oreochromis niloticus) fillets stored at 4 °C for 14 days
Control samples exceed the limit of 7.0 log cfu/g for TAMC19 on storage day 4, while tilapia fillets treated with HHP, UV-C and UV-C+HHP reached this limit on storage day 14
The presence of Enterobacteriaceae in fish is related mainly to cross contamination during fish processing such as filleting[32], in our study, the initial Enterobacteriaceae counts were below 3 cfu/g indicating that the tilapia fillets used were in good quality[19]
Summary
(Oreochromis niloticus) fillets stored at 4 °C for 14 days. Tilapia fillets were divided into four groups: control (untreated samples), UV-C, HHP, and UV-C combined with HHP (UV-C+HHP); UV-C was applied at dose of 0.103 ± 0.002 J/cm[2], and HHP at a pressure of 220 MPa for 10 min at 25 °C. The effectiveness of HHP varies with the type of matrix and with the microorganisms (genus; specie and strain; positive or negative Gram; spore or vegetative cells; and growth phases – lag, log or stationary phase)[7,11]. Another emerging non-thermal technology is ultraviolet radiation type C (UV-C, wavelengths of 200−280 nm), which acts directly on the microbial DNA and reduces the bacterial load in foods[12]. Studies of UV-C utilization in previously uninvestigated foods such as tilapia fillets may help to encourage its industrial application
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