DETERMINATION OF GLASS TRANSITION TEMPERATURE OF RAINBOW TROUT (ONCORHYNCHUS MYKISS) AND EFFECTS OF VARIOUS CRYOPROTECTIVE BIOPOLYMER BLENDS ON SOME CHEMICAL CHANGES

Sucrose  +  sorbitol  +  gum arabic (2  +  2  +  0.15%), sucrose  +  sorbitol  +  carrageenan (2%  +  2%  +  0.15%), sucrose  +  mannitol  +  gum arabic (2%  +  2%  +  0.15%), sucrose  +  mannitol  +  carrageenan (2%  +  2%  +  0.15%), sorbitol  +  mannitol  +  gum arabic (2%  +  2%  +  0.15%) and sorbitol  +  mannitol  +  carrageenan (2%  +  2%  +  0.15%) were blended with ground rainbow trout and stored at glass transition temperature ( T _g) of rainbow trout ( − 13C), determined by differential scanning calorimetry at − 9 and − 18C for 6 months. Total volatile basic nitrogen (TVB-N) and thiobarbituric acid-reactive substances (TBARS) were determined at 1st, 3rd and 6th months of storage periods. Biopolymer blends and storage period had a significant effect ( P <  0.05) on the TVB-N and TBARS values. T _g and − 18C showed same effect on TVB-N and TBARS values but − 9C has statistically different effect on them.

PRACTICAL APPLICATIONS

The T_g value was found as −13C for rainbow trout. This value is higher than commercial storage temperature (−18C). This has a great importance in terms of economical viewpoint. It was determined that TVB-N values were same and TBARS values were similar at the end of 6 months storage at T_g and −18C. When considering these two parameters, it can be accepted that −13C could be an indicator of usability instead of −18C.     

Determination of glass transition temperature of beef and effects of various cryoprotective agents on some chemical changes

Sucrose (2%), sorbitol (2%), mannitol (2%), gum arabic (0.15%), carrageenan (0.15%) and meat stabilizer (0.5%) were blended with ground beef and stored for 6 months separately at -9°C, -13°C (glass transition temperature (T(g)) of beef determined by Differential Scanning Calorimetry (DSC)) and -18°C. Total volatile basic nitrogen (TVB-N) and Thiobarbituric acid-reactive substances (TBARS) were determined at 1, 3 and 6th months of storage. Cryoprotectants and storage period had a significant effect (P<0.05) on the TVB-N and TBARS values. Although there were no statistically significant differences between storage at -13°C (T(g)) and -18°C, storage at -9°C had different effects on TVB-N and TBARS.     

Canthaxanthin as an Antioxidant in a Liposome Model System and in Minced Patties from Rainbow Trout

Canthaxanthin (CX) delayed formation of thiobarbituric acid reactive substances (TBARS) in a concentration-dependent manner in a ferrous chloride (FeCl₂)-initiated liposome system at 37 °C (p < 0.05). CX delayed TBARS formation in minced flesh from rainbow trout (Oncorhynchus mykiss) at 6 d of 4 °C storage in trial 1, and at 0, 2, 4 and 6 d in trial 2 when compared with controls at 4 °C (p < 0.05). Day 0 TBARS values in trial 2 were equivalent to d 6 of trial 1. CX concentration and a* value decreased in minced trout flesh during 6 days of 4 °C storage (p < 0.05). Overall, CX demonstrated antioxidant activity in vitro and in the minced tissue of CX-supplemented rainbow trout.     

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     

Quality Assessment of Farmed Rainbow Trout (Oncorhynchus mykiss) during Chilled Storage

ABSTRACT:  The quality changes of farmed rainbow trout ( Oncorhynchus mykiss ) stored in ice for a period of up to 20 (0, 4, 8, 12, 16, and 20) d were determined by chemical (total volatile basic nitrogen [TVB-N], free fatty acid (FFA), thiobarbituric acid (TBA), peroxide value (PV), heme iron), microbiological (total viable counts, TVC), and sensory methods. The TVB-N level showed fluctuations during storage, indicating that TVB-N could not be a good indicator of rainbow trout quality. The TBA values remained low and were found to fluctuate during storage. The PV values and the release of FFA increased ( P < 0.05), while heme iron content decreased during storage. The total viable counts of rainbow trout increased ( P < 0.05) from the initial value of 4.0 log CFU/g (day 0) to 7.04 log CFU/g (day 20) over the period of storage. This study showed that sensory analysis of rainbow trout correlated well with the microbiological analysis. The results of this study according to microbiological and sensorial data indicated that the shelf life of rainbow trout stored in ice was approximately 9 to 11 d.     

Effects of modified atmosphere and vacuum packaging on microbiological and chemical properties of rainbow trout (Oncorynchus mykiss) fillets

Microbial (psychrotrophic, mesophilic aerobic bacteria and Enterobacteriacae counts), and chemical analysis [pH, total volatile bases nitrogen (TVB-N), lipid oxidation (Thiobarbituric acid reactive substance, TBARS)] of rainbow trout (Oncorynchus mykiss) fillets in air (control), vacuum and modified atmosphere packaging (MAP) with various gas mixtures conditions at 4+/-1 degrees C were determined. The gas mixtures evaluated were 100% CO2, 2.5% O2+7.5% N2+90% CO2 and 30% O2+30% N2+40% CO2. Psychrotrophic bacteria count was above 1 x 10(7) cfu/g on the 12th day in 100% CO2. However; mesophilic bacteria count was below 1 x 10(6) cfu/g at the end of the 14-day storage period. Enterobacteriaceae count was significantly lower in samples packaged with MAP. Lipid oxidation increased rapidly after 6 days of storage in the samples containing 30% O2. While minimum TBARS values were recorded in fillets containing 100% CO2 and vacuumed fillets, the lowest TVB-N values were obtained in fillets with 100% CO2.     

Acid hydrolysis of kappa‐carrageenan as a way of gaining new substances for freezing process modification and protection from excessive recrystallisation of ice

The effects of κ‐carrageenan and its hydrolysates on modification of the freezing process and also on inhibition of excessive recrystallisation of ice in sucrose solutions during storage were compared. Acid hydrolysis of κ‐carrageenan was carried out using sulphuric (H₂SO₄) and hydrochloric acid (HCl). Most effective in the hydrolysis process turned out to be H₂SO₄, which degraded κ‐carrageenan to a molecular mass of around 3 × 10⁶ Da, after 1.5 h of hydrolysis. Addition of 0.005% of the new poligeenan (degraded carrageenan), to a sucrose solution (30%), frozen at ?20 °C, caused a nearly 50% reduction in the phase‐change stages, and consequently, the total time of freezing was shorter. Significant retardation of recrystallisation was observed for both types of poligeenan, but a stronger effect was observed for the oligosaccharides obtained after HCl hydrolysis, and after 96 h of storage at ?8 °C, the equivalent diameter of ice crystals was not greater than 11 μm.     

Spray-Drying of Probiotic Cashew Apple Juice

Data on spray-drying of fruit juices containing probiotic bacteria are scarce. The main challenge is to avoid the viability losses of the microorganism during drying and storage. In the presented study, the dehydration by spray-drying of cashew apple juice containing Lactobacillus casei NRRL B-442, and the influence of the storage temperature (25 and 4 °C) on the viability of L. casei NRRL B-442 and on the physical properties of the powder during 35 days of storage were evaluated. Probiotic cashew apple juice was dehydrated according to the following conditions: inlet temperature of the drying air (120 °C), feed flow rate of juice (0.3 L/h), hot air flow (3.0 m³/min), and pressurized air flow (30 L/min). The outlet temperature was 75 °C. The carriers used were 20 % (w/v) maltodextrin or 10 % (w/v) maltodextrin + 10 % (w/v) gum arabic. Microbial survival rates higher than 90 % were obtained for the powder stored at 4 °C for 35 days (both carriers) and higher than 70 % up to 21 days for the powder obtained using only maltodextrin at 25 °C. Higher yields were obtained only by maltodextrin which was used as carrier (72 %) compared to the yield obtained when the mixture of maltodextrin and gum arabic was applied (60 %). The water activity was kept low (Aw?<?0.30) during the storage, and the characteristic color of the product was maintained.     

Color Stability of Rainbow Trout Fillets during Frozen Storage

The effects of frozen storage (3 and 6 months at ?20 and ?80°C) on stability of carotenoids and color [CIE, (1976) L*a*b* and H(°)_ab] in vacuum-packed fillets of rainbow trout were studied in a paired-sample experiment. The trout were fed diets containing astaxanthin or canthaxanthin at different water salinities and temperatures. Carotenoids in the flesh were stable (up to 5% loss) for 6 months at ?20 or ?80°C, regardless of carotenoid sources and rearing conditions. Frozen storage resulted in increased L* (lightness), a* (redness) and b* (yellowness), and decreased H(°)_ab (hue) values. Color characteristics from different parts of the fillet differed significantly.     

The effects of nanoemulsions based on citrus essential oils (orange,mandarin, grapefruit,and lemon) on the shelf life of rainbow trout (Oncorhynchus mykiss) fillets at 4 ± 2°C

This study investigated the antioxidant and antimicrobial effects of nanoemulsions of orange, grapefruit, mandarin, and lemon essential oils on rainbow trout fillets stored at 4 ± 2°C in refrigerator. The results demonstrated that the shelf life of the rainbow trout fillets was determined as 10 days for the control group, 12 days for the tween 80 (surfactant), 14 days for orange and lemon treatment groups, and 16 days for mandarin and grapefruit groups. Nanoemulsions based on essential oils removed the fishy odor and had a positive effect on organoleptic quality. The use of citrus essential oil-based nanoemulsions decreased the values of biochemical parameters and slowed the growth of bacteria compared to the control group. Among all treatment groups, only the control group exceeded the TVB-N limit value on the 12th day of storage. PV and FFA values in fillets treated with mandarin and grapefruit nanoemulsions developed more slowly during the storage period. In addition, the lowest bacteria counts were found in the mandarin and grapefruit treatment groups. It can be concluded that especially mandarin and grapefruit EOs in all citrus essential oils can be recommended for preparing nanoemulsions in the preservation of rainbow trout fillets.     

Textural Changes and Functional Properties of Cod Mince Proteins as Affected by Kidney Tissue and Cryoprotectants

The addition of cryoprotectants, e.g., a mixture of sucrose and sorbitol or polydextrose (PDT) with sodium hexametaphosphate (SHMP), to improve the texture and water retention properties of cod mince with kidney tissue (modified mince) was studied at ?47°C. Kidney tissue provided trimethylamine oxide (TMAO) demethylase to accelerate dimethylamine (DMA) and formaldehyde formation. Expressible moisture (EM), water uptake ability (WUA), protein solubility, cook loss, DMA production, and textural profile analysis were determined to detect changes in modified mince during frozen storage. Modified mince with SHMP and sucrose/sorbitol or PDT at ?14°C had improved EM, WUA, and cook loss and was more tender.     

Effects of ozonation on microbiological,chemical and sensory attributes of vacuum-packaged rainbow trout stored at 4±0.5°C

The effects of ozone in aqueous solution on the shelf life of whole, vacuum-packaged rainbow trout, stored under refrigeration (4±0.5°C) were studied by monitoring the microbiological, chemical and sensory changes for a period of 15 days. Vacuum-packaged non-ozonated trout served as the control sample. Ozonation affected populations of bacteria namely, mesophilic aerobic bacteria, Pseudomonas spp. and H₂S-producing bacteria until day 11 of storage, Brochothrix thermosphacta, lactic acid bacteria and Enterobacteriaceae until day 8 of storage. Trimethylamine (TMA) values of all rainbow trout samples remained low (<3 mg N/100 g) until day 11 of storage, and then increased to 12.2, 8.9 and 4.7 mg N/100 g for the control and the samples ozonated for 60 and 90 min, respectively on day 15 of storage. Total volatile basic nitrogen (TVB-N) values remained relatively constant (20–25 mg N/100 g) until day 11 of storage, but increased to 61.1, 37.6 and 39.4 mg N/100 g flesh for the control and ozonated specimen for 60 and 90 min, respectively on day 15 of storage. Thiobarbituric acid (TBA) values remained relatively constant (1–3 mg MA/kg flesh) until day 12 of storage but increased to 8.4, 6.4 and 3.8 mg MA/kg flesh on day 15 of storage for the control and the ozonated trout for 60 and 90 min, respectively. Sensory evaluation (odor, taste and texture) of cooked rainbow trout showed a very good correlation with bacterial populations. On the basis of both sensory and microbiological data, a shelf life of 10 and 12 days was obtained for ozonated, vacuum-packaged and refrigerated rainbow trout at 60 and 90 min, respectively.     

Rheological properties of commercial chestnut flour doughs with different gums

Rheology of chestnut flour (CF) doughs with arabic gum (AG), carboxymethyl cellulose (CMC), guar gum (GG) and tragacanth gum (TG) at different concentrations (up to 2.0%) were determined at 30 °C using a controlled stress rheometer. The mixing characteristics at 30 °C were achieved using Mixolab^® apparatus. Shear (0.01–10 s^?1), oscillatory (1–100 rad s^?1 at 0.1% strain), creep‐recovery (50 Pa for 60 s) and temperature sweep (30–100 °C) tests were performed. Rheological properties were significantly modified by gum added. Apparent viscosity of CF doughs, storage and loss moduli increased at content of AG (above 0.5%), CMC (at 1.0%), GG (above 1.5%) and TG (at 1.0%). Flow curves and mechanical spectra were fitted using Cross model and power models, respectively. The gelatinisation temperatures increased with gums. The same pasting trend was noticed using Mixolab^®. Creep‐recovery data, fitted by Burgers model, showed that elasticity of CF doughs improved with GG.     

The effect of selected hydrocolloids on the rheological properties of processed cheese analogues made with vegetable fats during the cooling phase

The aim of this work was to observe the influence of different hydrocolloids on changes in the rheological properties of processed cheese and their analogues within the process of cooling depending on the type of the fat used (butter, coconut fat and palm oil). κ‐carrageenan, ι‐carrageenan, λ‐carrageenan, arabic gum and locust bean gum were used at a concentration of 1.0% w/w. With the decreasing temperature during the cooling period, an increase in the complex modulus (G*) was observed in all samples tested. Within the cooling period, the sample with the addition of κ‐carrageenan showed both the most significant increase in G* in comparison with the control and the highest values of hardness after a 7‐day storage period regardless of the type of the fat used. The samples with coconut fat were assessed as the hardest. On the other hand, the samples with palm oil showed the lowest hardness (with the same hydrocolloid used). In the gelling hydrocolloids (κ‐ and ι‐carrageenan), only small changes in temperature of coil‐to‐helix transition were observed (in range of 2–7 °C) as a result of the addition of different types of fat.     

Effects of marination, cooking and storage on physico-chemical and microbiological properties of ready to eat trout döner kebab

The aim of this work was to investigate the use of rainbow trout (Oncorhynchus mykiss) in ready to eat döner kebab production and determine the effects of marination, cooking and storage conditions (4 and ?18 °C) on physico-chemical and microbiological properties of döner kebab. The raw trout meat, raw, cooked and stored döner kebab samples were subjected to moisture, protein, fat, ash, color, pH, cholesterol, biogenic amines, lipid oxidation, fatty acids profile, texture, microbiological and sensory analysis. The results indicated that the major fatty acids in trout döner kebab were palmitic, stearic, oleic, omega-3 and omega-6 fatty acids and unsaturated fatty acids were higher than saturated fatty acids (p < 0.05). Low biogenic amine and cholesterol contents were determined in döner kebab. It was found that ?18 °C of storage temperature was more effective than 4 °C for inhibition of lipid oxidation and microbial growth in trout döner kebab (p < 0.05). While cooking affected parameters evaluated (p < 0.05), marination did not have any significant effect. The study results indicated that using rainbow trout meat in döner kebab production could be beneficial to provide healthy meat products without posing any acceptability problems in terms of quality factors. This is the first paper to be reported on physico-chemical and microbiological properties of döner kebab produced with rainbow trout and effects of marination, cooking and different storage temperatures on these physico-chemical and microbiological properties.     

Effect of the presence of gum arabic on the thermostability of thaumatin

Summary The objective of this research was to evaluate the effect of gum arabic on thermostability of thaumatin. Thermodegradation of solutions of thaumatin with gum arabic at various temperatures (50, 70 and 90 °C) was studied. This degradation appeared to follow first‐order kinetics at whatever temperature was used for thermodegradation. The experiments revealed an activation energy (E_a) of 41.4 kJ mol^?1 and a t_90% (time necessary to obtain a decrease of 10% of the initial concentration) of about 24 days for thaumatin with gum arabic, at 20 °C, at pH 4.90.     

Heat-induced Gelation of Minced Rainbow Trout (Salmo gairdneri:) Effect of pH, Sodium Chloride and Setting

The structure formation of minced rainbow trout was monitored during heating from 30°C to 85°C by a dynamic rheological method. The maxima of storage modulus (G') were found at 37°C and in the range of 45°C to 60°C. The largest differences in rigidity resulted from seasonal variations. Firmest protein matrix was obtained by using well-fed fish as raw material, by setting the gels at 35°C and using a pH value around 6.1. Sodium chloride in the range 1–2% had little effect on the final rigidity of the minced rainbow trout gels.     

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。     

Comparison of chitosan–gelatin composite and bilayer coating and film effect on the quality of refrigerated rainbow trout

The effect of chitosan–gelatin coating and film on the rancidity development in rainbow trout (Oncorhynchus mykiss) fillets during refrigerated storage (4 ± 1 °C) was examined over a period of 16 days. Composite and bilayer coated and film wrapped fish samples were analysed periodically for microbiological (total viable count, psychrotrophic count) and chemical (TVB-N, POV, TBARS, FFA) characteristics. The results indicated that chitosan–gelatin coating and film retained their good quality characteristics and extend the shelf life of fish samples during refrigerated storage .The coating was better than the film in reducing lipid oxidation of fillets, but there was no significant difference between them in control of bacterial contamination.     

Stability of hydroperoxide lyase activity from Amaranthus tricolor (Amaranthus mangostanus L.) leaves: influence of selected additives

BACKGROUND: Hydroperoxide lyase (HPL) has potential value for the flavour additive industry. Currently, the production and application of HPL suffer from stability problems. The objective of this study was to investigate the stabilisation of HPL preparation from Amaranthus tricolor leaves by the addition of selected chemical additives. RESULTS: Amaranthus tricolor leaves were identified as a particularly rich source of 13‐HPL activity. The addition of 100 g L^?1 sucrose and trehalose to microsomal HPL prior to lyophilisation could retain nearly 100% enzymatic activity, compared to only 20% for the lyophilised control. The lyophilised microsomal HPL containing sucrose maintained full activity for even 40 days storage at ? 20 °C. For HPL solution, glycerol was effective for long‐term stability at ? 20 °C. Moreover, poyols (sucrose and trehalose) and amino acid (glycine) enhanced the thermostability of HPL, while KCl and polyol mannitol decreased the thermostability of HPL. CONCLUSION: The flavour‐producing enzyme HPL, found in the leaves of Amaranthus tricolor, was stabilised by the addition of chemical additives. Copyright © 2010 Society of Chemical Industry