Modified atmosphere packaging of filleted rainbow trout

Shelf‐lives of filleted rainbow trout (Oncorhynchus mykiss) packaged in over‐wrap, vacuum and gas mixture conditions and stored at 1 ± 1 °C were compared by measurement of pH, total volatile bases (TVB), hypoxanthine content, lipid oxidation (TBARS value), superficial counts of aerobic psychrotrophic flora and sensory analysis (colour, odour and flavour). The gas mixtures evaluated were 10% O₂ + 50% CO₂ + 40% N₂, 10% O₂ + 50% CO₂ + 40% Ar, 20% O₂ + 50% CO₂ + 30% N₂, 20% O₂ + 50% CO₂ + 30% Ar, 30% O₂ + 50% CO₂ + 20% N₂ and 30% O₂ + 50% CO₂ + 20% Ar. Sensory quality deterioration was delayed and bacterial growth as well as increases in pH, TVB and hypoxanthine levels were reduced by modified atmosphere packaging (MAP). Lipid oxidation was higher in gas packages with 20 and 30% O₂ than in those with 10% O₂. Vacuum‐packed fillets presented the lowest TBARS values. In summary, MAP gave rise to a significant extension of shelf‐life when compared with vacuum and over‐wrap packaging. No significant differences were found between the packages containing either N₂ or Ar. The best evaluated atmosphere consisted of 10% O₂ + 50%CO₂ + 40% N₂/Ar. © 2002 Society of Chemical Industry     

不同保鲜剂结合微冻技术对虹鳟鱼块在贮藏期间品质的影响

为延长虹鳟鱼块货架期,本实验将新鲜虹鳟鱼块分别用蒸馏水、乳酸链球菌素(0.5 g/kg)、虾仁宝(2.5 g/kg)、海淡水鱼虾蟹贝通用保鲜剂(3.0 g/kg)处理30 min后,结合微冻技术(-3℃贮藏30 d),探究3种保鲜剂对虹鳟鱼块微生物指标、理化指标及质构特性的影响。研究结果表明:在30 d微冻货架期内,乳酸链球菌素在贮藏前23 d抑菌效果明显,23 d后三种保鲜剂抑菌效果基本相同,在相同条件下通用保鲜剂在前20 d贮藏过程中相比于其它两种保鲜剂在降低2-硫代巴比妥酸反应物(TBARS)、挥发性盐基氮(TVB-N)、pH、汁液损失方面有显著效果,保证了较好的质构特性,保鲜鱼肉品质效果最佳。本研究结果为虹鳟鱼肉在贮藏期的品质保持技术的发展提供了参考依据。     

Impact of dietary carotenoid and packaging during frozen storage on the quality of rainbow trout (Oncorhynchus mykiss) fed carotenoids

BACKGROUND: The storage life of frozen salmonids is often limited primarily by oxidation and flesh discolouration due to carotenoid degradation. The objective of this research was to determine the carotenoid changes and therefore the muscle colour modifications during 6 months of frozen storage (?18 °C) of whole rainbow trout fed astaxanthin (100 ppm) or canthaxanthin (80 ppm), kept under two different packagings: plastic film and cardboard box. RESULTS: After 6 months of frozen storage, the carotenoid type effect was seen for dry matter while there was no packaging material effect on carotenoid, total lipids, and TBARS contents of trout fillets. The time under frozen storage had an effect on carotenoid and TBARS fillet concentration. The carotenoid‐type effect was noted for the four colour parameters (lightness difference, chroma difference, hue angle difference, and total colour difference) of rainbow trout fillet, while the packaging material effect was observed only for chroma. Frozen storage time had an effect on the four colour parameters of rainbow trout fillet. CONCLUSION: Carotenoid and packaging material effects were more marked for colour parameters than for biochemical parameters. In this study, as fish were frozen and stored as whole fish, fish skin provided good protection against oxidation. Copyright © 2011 Society of Chemical Industry     

The impact of strawflower and mistletoe extract on quality properties of rainbow trout fillets

Many plants, including strawflower and mistletoe, contain antioxidants and antimicrobials, which can increase the shelf life of seafood. The main aim of this study was to investigate the effect of mistletoe and strawflower extracts at doses of 0.5% (w/v) on the sensory, chemical and microbiological properties of rainbow trout fillets during 27 days of storage at 2 ± 1 °C. The phenolic compounds in these plants have been studied, but their effects on food quality and storage properties have not been reported. We found that extract of mistletoe did not extend the shelf life of the fillets; however, the strawflower extract show high antimicrobial activity in fish fillets. The shelf life of rainbow trout was 20 days for the control and fish treated with mistletoe extract and 23 days for fish treated with strawflower extract. The antioxidant effect of extracts on fish fillets was weak, whereas strawflower extract had high antimicrobial effect. Peroxide value (PV) and thiobarbituric acid (TBA) values fluctuated during storage periods around main values below 14 meq O₂ kg^?1 and 0.6 MA kg^?1, respectively. Putrescine, cadaverine, spermine, spermidine, serotonin, tyramine and dopamine were main amine, whereas histamine accumulated at low levels (<2 mg per 100 g). Strawflower suppressed biogenic amine accumulation in fish fillets. At the limit of acceptability, total viable count (TVC), Enterobacteriaceae and lactic acid bacteria count remained below 7.6, 6.83 and 8.01 log CFU g^?1, respectively. The results of this study show that ethanol extracts of strawflower improve the shelf life of rainbow trout.     

Effect of sexual maturation on thermal stability, viscoelastic properties, and texture of female rainbow trout, Oncorhynchus mykiss, fillets

The nutrient and energy demand of sexual maturation in many fish cultivars causes structural change to key contractile proteins and thereby, affects fillet firmness. Thermal denaturation and viscoelastic properties of white muscle from diploid (2N; fertile) and triploid (3N; sterile) female rainbow trout were investigated at 6 age endpoints from July 2008 through spawning in March 2009. Differential scanning calorimetry showed, in March, that the actin denaturation temperature (T(max,actin)) of 2N females was higher than that observed in 3N females (78.17 versus 77.27 °C). From 35 to 45 °C, viscoelastic measurement revealed that muscle from 2N females and younger fish (July, 16 mo) had greater elasticity (lower tan δ) than muscle from 3N females and older fish (November to March; 20 to 24 mo), respectively. The highest elastic response and the firmest fillets were observed in July. Raw fillets were softer (Allo-Kramer shear; P < 0.05) from September to January (288.77 g/g on average) than those collected in July (475.15 g/g) and March (366.79 g/g). Soft fillets became firmer after cooking except for January samples. Greater cook yield and softer fillets were observed in January compared to December. Lipid accumulation in 3N females may lubricate muscle fibers and protect them from losing functionality during the spawning season for animals on a high plane of nutrition. PRACTICAL APPLICATION: The relationship between fish maturation, measured as egg development, and chemical characteristics of fillets from fertile and sterile fish was evaluated. Thermal denaturation and viscoelastic characterization revealed changes in stability and gelling properties of muscle proteins that were related to changes in fillet texture.     

Effect of dietary vitamin E supplementation and refrigerated storage on quality of rainbow trout fillets

Rainbow trout were fed a low vitamin E (200 mg/kg; LVE) or a high vitamin E (5000 mg/kg; HVE) diet for 9 wk to characterize the effect of vitamin E supplementation at 5000 mg/kg on fillet quality. Fish were sampled at 2, 3, 4, 5, 7, and 9 wk of the trial. Fillets were stored at 2 °C for 0, 7, and 14 d, and analyzed for pH, psychrotrophic counts, color, cook yield, shear force, crude fat and moisture content, α-tocopherol, fatty acid composition, and lipid oxidation. There was a significant feeding duration by fillet storage time interaction for psychrotrophic counts, crude fat content, cook yield, and shear force. Fillet L* value was not affected by diet, feeding duration or storage time. Fillet a* was lowest at 14-d storage, and b* values increased with fillet storage time. High vitamin E diet increased fillet α-tocopherol from 33 to 155 mg/kg. High vitamin E decreased palmitic acid and increased linoleic acid and omega-6 fatty acids. Feeding through 9 wk increased the relative proportions of unsaturated, polyunsaturated, and omega-3 fatty acids, and decreased saturated and omega-6 fatty acids. At 0-d storage, HVE diet did not affect thiobarbituric acid-reactive substances (TBARS) at any sampling week, and fasted fish generated fewer TBARS compared to non-fasted fish.     

Effect of gamma irradiation and frozen storage on chemical and sensory characteristics of rainbow trout (Oncorhynchus mykiss) fillet

The present study was conducted to evaluate the combined effect of low‐dose gamma irradiation (1, 3 and 5 kGy) and frozen storage (5 months at ?20 °C) on chemical and sensory characteristics of rainbow trout (Oncorhynchus mykiss) fillet. Our statistical analysis showed that irradiation process and frozen storage time had a significant effect (P < 0.05) on total volatile nitrogen (TVN), peroxide value (PV), thiobarbituric acid (TBA) and pH. The level of all of these factors increased with increasing frozen storage time. At the end of the fifth month of frozen storage, the lowest and the highest level of TVN, PV and TBA were corresponding to the irradiated samples at 3 and 5 kGy, respectively. In terms of the overall acceptability of their texture, odour, colour and taste, irradiated samples at 3 kGy had the best quality and remained acceptable after 5 months frozen storage. The optimum dose of gamma radiation of rainbow trout fillets according to chemical and sensory analysis was obtained at 3 kGy.     

Relating instrumental texture, determined by variable-blade and Allo-Kramer shear attachments, to sensory analysis of rainbow trout, Oncorhynchus mykiss, fillets

Texture is one of the most important quality attributes of fish fillets, and accurate assessment of variation in this attribute, as affected by storage and handling, is critical in providing consistent quality product. Trout fillets received 4 treatments: 3-d refrigeration (R3), 7-d refrigeration (R7), 3-d refrigeration followed by 30-d frozen storage (R3F30), and 7-d refrigeration followed by 30-d frozen storage (R7F30). Instrumental texture of raw and cooked fillets was determined by 3 approaches: 5-blade Allo-Kramer (AK) and variable-blade (VB) attachment with 12 blades arranged in perpendicular (PER) and parallel (PAR) orientations to muscle fibers. Correlation between instrumental texture and sensory hardness, juiciness, elasticity, fatness, and coarseness was determined. Muscle pH remained constant at 6.54 to 6.64. Raw fillets lost 3.66% of their original weight after 30-d frozen storage. After cooking, weight loss further increased to 15.97%. Moisture content decreased from 69.11 to 65.02%, while fat content remained constant at 10.41%. VBPER detected differences in muscle sample strength (P= 0.0019) and demonstrated effect of shear direction reported as maximum force (g force/g sample). AKPER detected differences in energy of shear (g × mm; P= 0.0001). Fillets that received F30 treatments were less extensible. Cooking increased muscle strength and toughness. Force determined by VBPER was correlated with sensory hardness (r= 0.423, P= 0.0394) and cook loss (r= 0.412, P= 0.0450). VB attachment is accurate, valid, and less destructive in fillet texture analysis. PRACTICAL APPLICATION: A new shearing device was validated with sensory analysis. Settings and parameters obtained could be used to define fillet texture quality associated with muscle fiber orientation.     

虹鳟鱼油的酶法提取工艺及其脂肪酸组成分析

以虹鳟鱼内脏为原料,采用酶法提取虹鳟鱼油。以虹鳟鱼油提取率为指标,在单因素实验的基础上,由响应面法优化酶法提取虹鳟鱼油工艺条件,并对虹鳟鱼油的脂肪酸组成进行分析。结果表明:酶法提取虹鳟鱼油的最佳工艺条件为采用木瓜蛋白酶、酶解温度61℃、酶解时间61 min、酶解pH 7. 0、加酶量2. 2%、液料比4∶1,在此条件下虹鳟鱼油提取率为88. 67%;提取得到的虹鳟鱼油呈浅黄色、稍有浑浊,具有鱼油腥味、无酸败味,酸价(KOH)和过氧化值分别为3. 68 mg/g和1. 75 mmol/kg,符合SC/T 3502—2016粗鱼油一级标准;虹鳟鱼油的主要不饱和脂肪酸为油酸19. 99%、亚油酸26. 75%、亚麻酸8. 93%、DHA 4. 48%、EPA 0. 97%。     

Quality assessment of salted, modified atmosphere packaged rainbow trout under treatment with oregano essential oil

The present study evaluated the effect of oregano essential oil (EO) on fresh salted, packaged (45%CO(2)/5%O(2)/50%N(2)) rainbow trout fillets and stored for a period of 21 d at 4 °C. Treatments included the following: M1 (control without added EO), M2 (EO 0.2%, v/w), and M3 (0.4%, v/w). Populations of lactic acid bacteria (LAB), H(2)S-producing bacteria (including Shewanella putrefaciens), Enterobacteriaceae, and Pseudomonas spp. reached higher final numbers in control (M1) than for M2 and M3 samples. Under treatments M2 and M3, total volatile basic nitrogen (TVBN) and trimethylamine nitrogen (TMAN) values were lower than for M1 samples, whereas lipid oxidation, as judged by determination of thiobarbituric acid values (TBA), did not occur during the refrigerated storage period. Interestingly, treatment M2 resulted in a shelf-life extension of 7 to 8 d for the fresh trout fillets, whereas treatment M3 proved unsuitable (due to strong odor) for trout fillet preservation, as determined by sensory evaluation. PRACTICAL APPLICATION: The use of an essential oil such as oregano oil in fresh fish preservation may be considered an alternative "natural" additive, enhancing the sensory characteristics and extending the shelf life of the product.     

The effect of liquid smoking of fillets of trout (Salmo gairdnerii) on sensory,microbiological and chemical changes during chilled storage

The storage time at 4 ± 1 °C of liquid smoked fillets of trout (Salmo gairdnerii) produced with a new smoking technique, using a combination of liquid smoke and steaming at 2 bar pressure for 30, 45 and 60 min, was studied. Maximum total viable counts (TVC) were reached after 25 days in the samples processed for 30 min and after 48 days in those processed for 45 and 60 min. However, panellists rejected the samples long after maximum TVC was observed. The increase of TVC was also confirmed using a particle size analyser, indicating a possible direct detection of microbial growth. A reduction of about 50% in the C22:6n − 3/C16:0 ratio was found across the whole period of storage, indicating lipid oxidation. The hypoxanthine/inosine (Hx/Ino) ratio showed a good relationship with both TVC and sensory results. Thus, when the Hx/Ino ratio was higher than 1.3, the products had reached their maximum acceptable TVC and were approaching their rejection time by the panellists, indicating that the Hx/Ino ratio is a good indicator of the shelf-life of smoked products of trout (S. gairdnerii).     

Microstructure and instrumentally measured textural changes of rainbow trout (Oncorhynchus mykiss) gravads during production and storage

BACKGROUND: Gravad fish belong to a group of low‐processed products obtained from fresh fish by rubbing fillets with a mixture of sugar and salt and then placing them in cold storage. Little is known about changes in the tissue during the production and storage of gravads. The aim of the present study was to investigate the microstructural and textural changes in rainbow trout (Oncorhynchus mykiss) gravad during processing and vacuum storage at 3 °C and ?30 °C. RESULTS: Microscopic observations of gravad showed greater compactness of structure when compared with raw trout muscle, characterised by the disappearance of the divisions between adjoining myofibrils in gravad. Freezing, on the other hand, caused the myofibrils to again become more clearly distinguishable despite being partly agglomerated into lamellae. The above changes in structure were accompanied by changes in the textural and rheological properties of the product. It was observed that the texture profile (TPA) changed, resulting in an increase in the cohesiveness and chewiness of the gravads when compared to the raw fillets. There was also a lowering of stress decay during the relaxation test and a decrease in the value of the storage modulus (G′) as analysed by oscillatory rheometry. Further changes observed during storage were mainly concerned with an increase in the hardness and chewiness of gravads. CONCLUSION: Gravading significantly changes the rainbow trout fillets by making the microstructure more compact. This process is accompanied by changes in texture and rheological properties, which next are running during the storage of a chilled or frozen product. These changes are significant enough for potential consumers to be made aware of the fact that the texture of the product changes considerably during its shelf life. Copyright © 2009 Society of Chemical Industry     

Peppermint essential oil-loaded solid lipid nanoparticle in gelatin coating: Characterization and antibacterial activity against foodborne pathogen inoculated on rainbow trout (Oncorhynchus mykiss) fillet during refrigerated storage

The present study was conducted to determine the characterization and antibacterial activity of peppermint essential oil-loaded solid lipid nanoparticle (PEO–SLN) and its impact on the quality of trout fillet stored at 4 ± 1°C for 12 days. The SLNs were prepared through a bath sonication technique. PEO–SLNs contained 0.2% (w/v) PEO in 2% of lipid phase glycerol monostearate (GMS) and tween 80 (1% w/v) used as a surfactant in the aqueous phase. The characterization parameter of PEO–SLN was evaluated, and the antibacterial activity of PEO–SLNs was conducted under in vitro conditions. Trout samples were analyzed for inoculated Pseudomonas aeruginosa, Listeria monocytogenes, and Escherichia coli O157:H7 during refrigerated storage. The mean particle size of PEO–SLNs was 154.83 ± 1.21 nm with a polydispersity index (PDI) of 0.35 ± 0.01 and zeta potential was about −24.16 ± 0.51 mV. The results indicated that PEO–SLN had higher antibacterial activity than the free form of PEO and also when used in combination with gelatin coating (gel + PEO–SLN) had a significant effect on preventing microbial growth in trout fillets (p < 0.05). The most decreasing rate of P. aeruginosa (1.92 log CFU/g), E. coli O157:H7 (0.71 log CFU/g), and L. monocytogenes count (1.69 log CFU/g) was seen in gel + PEO–SLN. These findings illustrated that PEO–SLNs could potentially be utilized in the food industry to increase the shelf life of fish fillets.     

复合发酵剂对发酵猪肉干品质的影响

以清酒乳酸杆菌(Lactobacillus sakei)和木糖葡萄球菌(Staphylococcus xylosus)为复合发酵剂发酵猪肉干,研究复合发酵剂对肉干品质的影响。结果表明:添加复合发酵剂和自然发酵组的p H分别为5.21和5.48,水分活度(aw)分别为0.876和0.896。添加复合发酵剂和自然发酵组的亮度值(L*)分别为33.17和31.21,红度值(a*)分别为13.38和9.89,添加复合发酵剂显著改善肉干的色泽(p<0.05)。添加复合发酵剂使肉干硬度、内聚性和弹性分别降低37.8%、10%和20%,提高了肉干的嫩度,改善了肉干的咀嚼性。添加复合发酵剂组的组织状态、滋味、气味和色泽等感官评分均高于自然发酵组,具备优良的感官特性。      

3种保鲜剂及其复配对虹鳟鱼片冷藏品质的影响

以贮藏期间虹鳟鱼片的感官评分、挥发性盐基氮(total volatile basic nitrogen,TVB-N)值及菌落总数为评价指标,探究茶多酚、壳聚糖及柠檬汁处理对4℃冷藏虹鳟鱼片品质的影响,并通过响应面试验对3种保鲜剂进行配比优化。结果表明,与对照组比较,3种保鲜剂均能抑制虹鳟鱼片品质的劣变,其保鲜效果依次为:壳聚糖茶多酚柠檬汁;3种保鲜剂的最佳配比浓度为:壳聚糖1.75%,茶多酚0.25%,柠檬汁4.98%。经复配保鲜剂处理的虹鳟鱼片与对照组相比,可有效延缓贮藏期间其感官变质,鱼肉蛋白质等含氮物质的分解,同时对微生物生长具有一定的抑制作用。     

低场核磁结合电子鼻判定复合保鲜剂对冷藏虹鳟鱼片品质变化的影响

以质构、pH值、硫代巴比妥酸(TBA)值、挥发性盐基氮(TVB-N)值及菌落总数为评价指标,同时采用低场核磁共振(LF-NMR)及电子鼻技术对鱼片贮藏期间的水分和挥发性成分变化进行检测,研究复合保鲜剂(壳聚糖、茶多酚及柠檬汁)对虹鳟鱼片贮藏期间品质的影响。结果表明,复合保鲜剂组能较好地维持鱼片质构特性,同时可延缓鱼片TBA值、TVB-N值及菌落总数的增加。低场核磁测得两组鱼片贮藏期间T21幅值逐渐降低,在贮藏后期(12~14d),保鲜剂组鱼片自由水比例显著低于对照组(P0.05),且两组鱼片自由水比例与初期比较均增加。电子鼻PCA分析及LDA分析均可较好地区分贮藏期间鱼片的品质变化,LA分析发现引起鱼片新鲜度变化的主要成分为氮氧化合物、无机硫化物、芳香成分物质和乙醇等,而PCA分析结果表明对照组鱼片第6天开始发生腐败变质,保鲜剂组鱼片第10天开始趋于腐败。综上表明,低场核磁及电子鼻检测结果与理化指标结果具有一致性。     

清酒乳杆菌对发酵风干肠品质的影响

该研究采用清酒乳杆菌（Lactobacillus sakei，L. sakei）作为发酵菌株制备发酵风干肠，研究其对发酵风干肠品质的影响，以自然发酵产品作为对照组，在发酵成熟过程中的第0、3、6、9天测定产品的菌落总数、乳酸菌数、pH值、水分含量、水分分布、嫩度、色差、过氧化物值（Peroxide Value，POV）、硫代巴比妥酸值（Thiobarbituric Acid Value，TBARS）、脂肪酸含量和感官评分等指标，研究发酵菌株对风干肠品质的影响。试验表明，L. sakei接种组的乳酸菌数和菌落总数显著高于对照组（P<0.05），L*值、a*和b*显著低于对照组（P<0.05）；L. sakei接种组在发酵终点时，水分含量降至32.15%，pH值降至4.41，保证了发酵风干肠的安全性；POV值和TBARS值显著低于对照组（P<0.05），表明L. sakei具有较好的抑制脂肪氧化作用；L. sakei接种组的总体可接受性更高，发酵后期酯类物质种类和含量均高于对照组。综上，L. sakei的添加改善了产品的品质和风味。