Abstract
This study investigated the physicochemical, instrumental and bacterial parameters of tilapia fillets subjected to oxygen-scavenger packaging, alone or in combination with UV-C radiation at two doses (0.102 and 0.301 J/cm2), stored at 4 ± 1 °C for 23 days. The oxygen scavenger, both UV-C doses, and the oxygen scavenger combined with UV-C, independently of the dose, extended the shelf life in 5, 6 and 7 days, respectively, by decreasing the bacterial growth rate and the formation of degradation compounds (e.g., TVB-N and ammonia). Oxygen-scavenger packaging, alone or in combination with UV-C at 0.102 J/cm2 and 0.301 J/cm2 showed lower amounts of free amino acids (FAA; 34.39, 34.49 and 34.50 mg L-lysine/kg fish tissue, 3.63, 3.57 and 3.61 mg L- ornithine/kg fish tissue, 27.52, 27.63 and 27.67 mg L-arginine/kg fish tissue), biogenic amines (BA; 3.81, 3.87 and 3.89 mg cadaverine/kg fish tissue, 12.88, 12.91 and 12.86 mg putrescine/kg fish tissue, 2.41, 2.44 and 2.47 mg spermidine/kg fish tissue), redness (2.53, 2.55 and 2.59), yellowness (6.65, 6.69 and 6.72), lipid oxidation (1.52, 1.53 and 1.58 mg malondialdehyde/kg fish tissue) and protein oxidation (5.06, 5.11 and 5.18 nmol carbonyls/mg protein), with higher hardness (3273.41, 2652.98 and 2687.57 g) than control (air packaging; 41.97 mg L-lysine/kg fish tissue, 4.83 mg L- ornithine/kg fish tissue, 37.33 mg L-arginine/kg fish tissue, 4.82 mg cadaverine/kg fish tissue, 16.56 mg putrescine/kg fish tissue, 3.21 mg spermidine/kg fish tissue, 4.26 of redness, 8.17 of yellowness, 2.88 mg malondialdehyde/kg fish tissue, 9.44 nmol carbonyls/mg protein and 2092.58 g of hardness), respectively, on day 13 of storage when the control fillets were unfit for consumption (7 log CFU/g) (p < 0.05). However, in the same day of storage, both UV-C doses had similar values for BA (p > 0.05), higher amounts of FAA (44.28 and 44.13 mg L-lysine/kg fish tissue, 5.16 and 5.12 mg L- ornithine/kg fish tissue, 40.20 and 40.28 mg L-arginine/kg fish tissue), redness (4.86 and 5.33), yellowness (9.32 and 10.01), lipid oxidation (3.09 and 3.52 mg malondialdehyde/kg fish tissue) and protein oxidation (10.27 and 11.93 nmol carbonyls/mg protein), as well as lower hardness (1877.54 and 1767.39 g), respectively, than control fillets (p < 0.05). The combined preservation methods were the most effective in extending the shelf life and prolonging the physicochemical quality of the refrigerated tilapia fillets and the O2 scavenger proved to be a potential alternative to prevent the negative changes induced by both UV-C doses.
Highlights
Fish is rich in nutrients, but is highly perishable due to rapid endogenous enzyme and bacterial activity in the postmortem period, resulting in the production of undesirable metabolites, limited shelf life and loss of quality[1,2]
After the O2 scavenger sachets were placed and the samples were radiated with UV-C, they were stored at 4 ± 1 °C and analyzed for total aerobic mesophilic count (TAMC), total aerobic psychrotrophic count (TAPC), Enterobacteriaceae count, free amino acids, biogenic amines, total volatile basic nitrogen (TVB-N), ammonia (NH3), lipid oxidation, protein oxidation, and instrumental color and texture parameters
The number of colonies in the stationary phase of the fillets treated with the oxygen scavenger and/or UV-C radiation (0.102 or 0.301 J/cm2) was higher than in the fillets in air packaging (AP), these emerging techniques alone or in combination extended the www.nature.com/scientificreports shelf life of the tilapia fillets by decreasing (p < 0.05) the exponential growth rate (EGR) of the microorganisms (Table 1)
Summary
Fish is rich in nutrients, but is highly perishable due to rapid endogenous enzyme and bacterial activity in the postmortem period, resulting in the production of undesirable metabolites (e.g., total volatile basic nitrogen, ammonia and biogenic amines), limited shelf life and loss of quality[1,2]. In general, the UV-C doses needed to significantly extend the shelf life may lead to the production of reactive oxygen species (ROS), which remove a hydrogen atom from a weak C-H bond, initiating a free-radical chain reaction and intensifying the oxidative processes, changes in texture and color during refrigerated storage[1,19]. This effect depends mainly on the type and load of microorganisms present in the food matrix and the food composition[1,11,17] and UV-C is not necessarily dose-dependent[20]. This study investigated the effect of an O2 scavenger and two different doses of UV-C radiation (0.102 and 0.301 J/ cm2), alone or in combination, on the quality attributes of Nile tilapia fillets stored at 4 ± 1 °C for 23 days
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