Comparative evaluation of coated and uncoated rainbow trout (Oncorhynchus mykiss) fillets treated with phycocyanin: Antioxidant, antimicrobial, and shelf-life properties

The present study aimed to investigate the combine effects of salting and thyme oil on chemical and sensory changes of rainbow trout (Oncorhynchus mykiss) during storage (4°C) was investigated over a period of 24 days. There groups were constituted: group A-control salted, group B-salted samples with 0.4% of thyme oil and group C-salted samples with 0.8% of thyme oil. Fillets were subject to chemical (thiobarbituric acid reactive substances-TBARS, total volatile base nitrogen-TVB-N) and sensory analyses on certain days (0, 3, 6, 9, 12, 15, 18, 21 and 24th days) of storage. Five experienced panelists, academic staff who were trained in sensory descriptors for fishes, were employed to evaluate the quality of trout fillets during storage. Rainbow trout fillets were assessed on the basis of appearance, taste, texture and odour characteristics using a nine point descriptive scale. TVB-N and TBARS values increased in the duration of storage time in all groups. TVB-N and TBARS values in control groups were higher than other groups. Group C samples were assessed as the most acceptable products by the panellists. Difference in chemical and sensory changes between samples was found to be significant (p<0.05) during storage period.

In this study, it was aimed to determine the microbial and sensory properties of rainbow trout (Oncorhynchus mykiss) fillets by applying tea tree oil. The samples are divided into 3 groups. 1st group (the control group), 2nd group, 1% tea tree oil applied group (B), 3rd group 3% tea tree oil applied (C) group. The fillets were stored at 4±1ºC for 12 days. Fillets were then subjected to pH, microbiological (total aerobic mesophilic bacteria, psychrotrophic bacteria, yeast-mould) and sensory (appearance, general acceptability, odor and color) analysis. It was found that the use of tea tree oil in rainbow trout fillets had a significant (p&amp;lt;0.01) effect on total aerobic mesophilic bacteria, psychrotrophic bacteria, yeast-mould counts and pH values. In terms of the sensory parameters, the most liked group was the control group. As a result of the research, it was determined an inhibitory effect on bacteria depending on the concentration of tea tree oil.

The Klunzinger’s ponyfish (Equulites klunzingeri) protein powder extracted with acid or alkali aided process as a biodegradable coating material for rainbow trout (Oncorhynchus mykiss) fillets during cold (+2°C) and frozen storage (–18°C) were investigated. The coating with alkaline treated protein (AlPC) and acid treated protein (AcPC) extended the shelf life of fillets from 11 to 14 days in cold storage and improved the quality parameters in three months frozen storage period. According to total viable count and total psychrophile count results, bacteria grew more quickly in uncoated fillets than coated fillets. The protein-based coating did prevent spoilage of the rainbow trout fillets as reflected by a decrease in pH, total volatile base-nitrogen and free fatty acids during cold and frozen storage period. Therefore, this study demonstrated that fish protein-based coating had a positive effect on maintaining the rainbow trout fillets quality, and edible coatings from discard fish can offer a promising alternative for preserving fish fillets.

Usage of edible films and coatings alone or incorporated with natural extracts are a new approach to preservation and packaging of food. In this study, therefore, the microbiological, chemical quality, and sensorial changes of rainbow trout fillets coated with gelatin films supplemented with propolis extract (PE) (2, 8, 16%), as a source of polyphenols, were determined during 15 days of refrigerated storage (4 ± 1 °C). According to peroxide value (PV) and thiobarbituric acid reactive substances (TBARS) assays, lipid oxidation was delayed in the fillets coated with gelatin films incorporated with PE comparing with the control and gelatin-coated (without PE) fillets. The total volatile basic nitrogen (TVB-N) value of rainbow trout fillets showed an increase in all groups at the end of storage, observing the lowest values in the fillets coated with gelatin films prepared with 16% PE. Gelatin films enriched with PE had great inhibitory effects on the microbial growth in rainbow trout fillets. The addition of PE enhanced the effectiveness of gelatin films and delayed the lipid oxidation and sensory and microbial deterioration in trout fillets coated with these films. Thus, PE can be recommended to be used as a natural antioxidant and antimicrobial additive with gelatin films to maintain rainbow trout fillet quality.

The effects of Caper (Capparis spinosa L.) extracts on microbiological, chemical and sensory changes of rainbow trout (Oncorhynchus mykiss) fillets stored at 4 ˚C were evaluated. Trout fillets were dipped in Caper extracts (0.2 and 0.5%), packaged with or without modified atmosphere packaging (MAP; O2 5%, CO2 20%, N2 75%) and stored at 4 ˚C for 28 days. The data showed that lipid oxidation and spoilage of the samples were significantly delayed in the samples treated with Caper extract associated with MAP (p<0.05). The acceptability limit (7 log CFU g-1) of the psychrophilic bacterial counts was observed for MAP+Caper (0.5%) treatment in 7 and 14 days of storage time while it was reported for other treatments only in day 7. The use of 0.5 % Caper+MAP had the best antioxidative and antimicrobial effects, as well as sensory scores in the trout fillets during refrigerated storage (28 days) (p<0.05). This study determined that the Caper associated with MAP had significant effects on shelf-life extension of fresh rainbow trout at cold storage period and could be a natural preservative for extending shelf life of fish fillets.

Effect of quince seed mucilage edible films incorporated with oregano or thyme essential oil on shelf life extension of refrigerated rainbow trout fillets

This study explores the potential application of hyperspectral imaging (HSI; 430–1,010 nm) coupled with different linear and nonlinear models for rapid nondestructive evaluation of thiobarbituric acid‐reactive substances (TBARS) value in rainbow trout (Oncorhynchus mykiss) fillets during 12 days of cold storage (4 ± 2°C). HSI data and TBARS value of fillets were obtained in the laboratory. The primary prediction models were established based on linear partial least squares regression (PLSR) and least squares support vector machine (LS‐SVM). In full spectral range, the prediction capability of LS‐SVM (RP2 = 0.829; RMSEP = 0.128 mg malondialdehyde [MDA]/kg) was better than PLSR (RP2 = 0.748; RMSEP = 0.155 mg MDA/kg) model and LS‐SVM model exhibited satisfactory prediction performance (RP2 > 0.82). To simplify the calibration models, a combination of uninformative variable elimination and backward regression (UB) was used as variable selection. Nine wavelengths were selected. Various chemometric analysis methods including linear PLSR and multiple linear regression and nonlinear LS‐SVM and back‐propagation artificial neural network (BP‐ANN) were compared. The simplified models showed better capability than those were built based on the whole dataset in prediction of TBARS values. Moreover, the nonlinear models were preferred over linear models. Among the four chemometric algorithms, the best and weakest models were LS‐SVM and PLSR model, respectively. UB‐LS‐SVM model was the optimal models for predicting TBARS value in rainbow trout fillets (RP2 = 0.831; RMSEP = 0.125 mg MDA/kg). The establishing of lipid‐oxidation prediction model in rainbow trout fish was complicated, due to the fluctuations of TBARS values during storage. Therefore, further researches are needed to improve the prediction results and applicability of HIS technique for prediction of TBARS value in rainbow trout fish.

Rainbow trout fillet is susceptible to microbial and oxidative spoilage. Therefore, it is essential to use preservatives to extend its shelf life. Date extract has significant antibacterial and antioxidant properties. This research was conducted to study the effect of aqueous date extracts on chemical, microbial and sensory properties of farmed rainbow trout during refrigeration. Total phenolic and flavonoid content were determined through Folin-Ciocalteu and colorimetric method. The first step of study was performed for determination the antimicrobial activity of date extracts against the inherent flora of fish fillet, lactic acid bacteria, Pseudomonas and Enterobacteriaceae by disc diffusion method. In parallel with antimicrobial tests, sensory evaluation was also performed for choosing the best concentration of extracts in order to applying on fish fillets. In the second step of study, fish fillet samples were immersed in date extracts (3% w/v for 5 minute), packaged in zip–bags and stored at 4 oC over a period of 17 days. The extract-free fillet was used as control. The samples were analyzed for microbiological (mesophilic, lactic acid bacteria, Pseudomonas and Enterobacteriaceae counts) and chemical (PV, TBARS and TVB-N) parameters. The 5-point hedonic method was carried out for sensory evaluation by 30 trained panelists. Analyses were conducted at 2 h after preparation and 1, 3, 5, 7, 9, 11, 13, 15 and 17 days of storage. Phenolic and flavonoids contents showed no significant differences between date extracts (p>0.05). Total bacterial counts, Enterobacteriaceae, Pseudomonas, TBARS, PV and TVB-N showed no significant difference in test samples (p>0.05). These parameters were within an acceptable range up to 15 days for test samples while the control samples had a shelf life of 5 days. Samples preserved by Piaroum extract had the longest shelf life while samples preserved by the combination of extracts had the shortest. According to the results, the Piaroum, Zahedi, Mozafati extracts and their combination could be used as natural preservatives for trout fillet shelf-life extension.

ABSTRACTIn the present study, the effect of fish gelatin coating (FG; 4%, w/v) containing oregano (Origanum vulgare L.) essential oil (OEO; 1.2% w/v) on shelf-life extension of rainbow trout (Oncorhynchus mykiss) fillet stored under refrigerated storage (4 ± 1ºC) was investigated. The control and the treated fish samples were analyzed periodically for chemical (pH; total volatile basic nitrogen, TVB-N; peroxide value, PV; thiobarbituric acid, TBA) and microbiological (total viable count, TVC; psychrotrophic count) characteristics. The FG + OEO treatment produced significantly lower (p < 0.05) TVB-N values as compared to control and FG-coated samples after Day 6 and until the end of the storage period. The TBA values remained low and were found to fluctuate during storage. Results showed that TVC exceeded 6 log CFU g−1 on Day 8 of storage for control and FG-coated samples and Day 12 for samples coated with FG + OEO. The reduction of 1.05 and 0.83 log CFU g−1 of psychrotrophic counts was achieved by FG + OEO coating in trout fillet (p < 0.05) as compared with control and FG-coated samples, respectively. Therefore, the incorporation of OEO into FG coating may be a promising method of maintaining the storage quality of the rainbow trout fillet stored at refrigerated temperature.

This study investigated the effects of oxygen-scavenger packaging and UV-C radiation at two doses, alone or in combination, on lipid oxidation (malondialdehyde levels), protein oxidation (carbonyl content), instrumental color and texture parameters in rainbow trout fillets stored at 4 ± 1 °C for 9 days. The treatments were AP (air packaging), OSP (oxygen-scavenger packaging), AUV1 (air packaging + UV-C at 0.102 J/cm2), OSUV1 (oxygen-scavenger packaging + UV-C at 0.102 J/cm2), AUV3 (air packaging + UV-C at 0.301 J/cm2), and OSUV3 (oxygen-scavenger packaging + UV-C at 0.301 J/cm2). Lipid oxidation, protein oxidation, lightness and yellowness increased, while redness, hardness and chewiness decreased during storage in all treatments (p &lt; 0.05). OSP, OSUV1 and OSUV3 exhibited lower yellowness, total color difference (ΔE), lipid and protein oxidation, and higher redness, hardness and chewiness than air packaging (AP; p &lt; 0.05), being similar to each other concerning these parameters throughout storage (p &gt; 0.05). AUV3 showed higher lipid oxidation, protein oxidation, yellowness, ΔE, and lower redness, hardness and chewiness followed by AUV1 than AP (p &lt; 0.05). UV-C at these doses was not adequate for refrigerated trout fillets by inducing oxidative degradation. O2 scavenger was effective in preventing the adverse effects from storage period and UV-C, independently of the dose, and could be a simple and powerful alternative to make feasible the industrial application of UV-C at 0.102 and 0.301 J/cm2 in refrigerated rainbow trout fillets, which has proven antimicrobial effect and it is a promising non-thermal technology for the fish production chain.

Ameliorating effects of dietary Haematococcus pluvialis on arsenic-induced oxidative stress in rainbow trout (Oncorhynchus mykiss) fillet

A total of 72 male and 50 female trout (Oncorhynchus mykiss) fillets were weighed (range 328-794g, mean 546.2±101.8g; and range 426-994g, mean 672.2±106.1g, respectively), the pictures of whom were taken in a light box, and image analysis was done to measure pixel colors, length, and view area of the fillets. Weight (W) was predicted using view area (V) obtained by image analysis using linear (W=A+BV), and power (W=AVB ) equations. R2 values were between 0.823 and 0.937. Although there was no difference between mean L* and a* values of male and female fillets, significant differences were found between mean b* values (p<0.05). The colors of SalmoFan™ (SF) mini were also measured by image analysis and their mean L*, a*, b* values, and their entire color index (ECI) and reduced RGB values from 122 images were calculated. A total of 96 untrained panelists were asked to select the SF color of 5 representative fillets and to designate which point on the fillet image best described the SF color chosen. To predict SF numbers of the fillets by image analysis, four cases were considered: (1) whole fillet, (2) whole fillet with pixels a*>25, (3) a rectangle along the length of the fillet to approximate panelists' selection, and (4) pixels in this rectangle with a*>25. Mean L*a*b* values, mean reduced RGB values, and mean ECI of the four cases were used to predict fillet SF numbers. Different results obtained imply that image analysis can do repeatable and objective SF color classification of fillets, depending on the pixel selection method, and the color representation. PRACTICAL APPLICATION: Rainbow trout fillets can be assigned SalmoFan (SF) numbers using image analysis of the fillets. However, the selection of pixels and the color representation method affect the results. If these are standardized, SF numbers can be assigned objectively and automatically.

The aim of this study is to produce edible films with antimicrobial properties by using the discarded fruit peels (orange and lemon) as extracts and to determine the effect on shelf life of rainbow trout fillets and squid rings. For this purpose, antimicrobial edible films were performed the orange and lemon peels extracts by using xanthan, locust bean and carrageenan gums. Rainbow trout fillets (Oncorhynchus mykiss 1792) and squid rings (Loligo vulgaris 1798) were covered with this antimicrobial edible films from discarded fruit peels to extend the shelf-life of these products. As a result, total mesophilic bacteria count (TMC) of squid rings (CS) exceeded the microbiological limit of the consumption on day 6, whereas TMC of squid rings covered with limon peel+locust bean (LLS) and limon peel+carrageenan (LKS) did not exceed this limit on day 8. This study gave rise to not only can be produced of functional products from the fishery products but also the fruit peels residues can also be evaluated for this purpose. The results of this study can be evaluated by seafood and fruit juice processing plants as well as food producers.

In this research, the effect of thyme essential oil (EO) and packaging treatments (vacuum and modified atmosphere) on fresh rainbow trout fillets during storage for a period of 18 days at 4°C was investigated. Fillets were subjected to microbiological (total viable count(TVC), Pseudomonas, lactic acid bacteria, Enterobacteriaceae) and chemical [pH,thiobarbituric acid reactive substances (TBARS), total volatile basic nitrogen (TVB-N)] analyses on certain days (0, 3, 6, 9, 12, 15, 18th) of storage. TBARS and TVB-N values ​​increased in the duration of storage. Bacterial growth was inhibited in samples with increased concentration of thyme oil due to the antimicrobial activity of thyme oil. Overall, the combined use of thyme EO (0.8%, v/w) and modified atmosphere packaging (MAP) showed a synergistic effect for shelf-life extension of rainbow trout fillets. Key words: Modified atmosphere packaging (MAP), rainbow trout, shelf life, thyme essential oil, vacuum.

This study aimed to examine activating sodium alginate‐based edible coating (AL) with resveratrol (RE) as a dietary supplement for increasing the shelf life of rainbow trout (Oncorhynchus mykiss) fillet during refrigerated storage. Administered treatments were AL, AL–RE 0.1%, AL–RE 0.2%, and control. Samples were stored at 4 °C for 15 days and analyzed at 3‐day intervals. All treatments indicated a significant decrease (p ≤ .05) in their total viable counts, psychrotrophic bacteria, Enterobacteriaceae, Pseudomonas spp., lactic acid bacteria, and yeasts–molds compared to the control in the storage period. Thiobarbituric acid value and total volatile basic nitrogen were significantly lower in all treatments (p ≤ .05) compared to the control. RE improved the alginate effects on increasing the shelf life of the samples. In conclusion, RE can be considered as a replacement to the synthetic antimicrobials and synthetic antioxidants in the rainbow trout fillets with more health benefits.Practical applicationsSince fish fillets are very perishable products, improving preservation techniques for enhancing their shelf‐life seems quite necessary. Besides bacterial growth, oxidation reactions can induce the spoilage of fish meat in the storage period. The various synthetic preservatives are generally undesired by consumers because of their adverse effects. Resveratrol, a dietary supplement, can be used as a natural antioxidant and antimicrobial in the rainbow trout fillet with added health benefits.