Chitosan and Protein Coatings Affect Yield, Moisture Loss, and Lipid Oxidation of Pink Salmon (Oncorhynchus gorbuscha) Fillets During Frozen Storage

The effects of chitosan (CH1 = 1% and CH2 = 2% solution), egg albumin (EA), soy protein concentrate (SPC), pink salmon protein powder (PSP), and arrowtooth flounder protein powder (AFP) as edible coatings on quality of skinless pink salmon fillets were evaluated during 3 mo frozen storage. Coating with 2% chitosan (CH2) resulted in significantly higher yield than coating with PSP and AFP. The thaw yield of salmon fillets coated with CH2 was higher than those of the control and fillets coated with AFP. The noncoated, CH1‐, and CH2‐coated fillets had similar drip loss (0.4% to 1.2%), which was lower than those observed for PSP‐ and AFP‐coated fillets. All fillet samples had similar cook yield (84.2% to 88.8%). The fillet coated with CH1, CH2, SPC, and EA had significantly higher (P < 0.05) moisture content after thawing than the control noncoated fillets. Coating with CH1 and CH2 was effective in reducing about 50% relative moisture loss compared with the control noncoated fillets. Chitosan (CH1 and CH2) and SPC delayed lipid oxidation. There were no significant (P > 0.05) effects of coating on a*, b*, and whiteness values for cooked fillets after 3 mo frozen storage.     

Prefreezing application of whey protein‐based edible coating to maintain quality attributes of strawberries

Prefreezing application of whey protein concentrate (WPC)‐based edible coating to maintain quality attributes of strawberries was studied. Beeswax (BW) was added to the solutions (0%, 20% and 40% with respect to the solids contained in the mixture WPC/glycerol). Coated and control fruits were frozen, stored at ?20 °C and thawed. After thawing, weight loss, firmness, microstructure and colour parameters were measured. Coating with 20% BW reduced strawberries weight loss after thawing (55%). Strawberries firmness was maintained equally in all groups analysed although a slight improvement at the cell microstructure alterations caused by the freezing process was observed in coated fruits. Strawberries brightness was similar in all groups. Colour parameter a* showed a tendency to decrease with the increasing BW concentration, and only b* of coated fruits was lower than controls. The application of whey protein coating could be an attractive treatment to maintain quality attributes of strawberries undergoing the freezing process.     

Effects of microbial transglutaminase added edible coatings based on heated or ultrasound-treated whey proteins in physical and chemical parameters of frozen Atlantic salmon (Salmo salar)

The effects of the addition of transglutaminase to heated or ultrasound-treated whey protein coatings on quality parameters of frozen Atlantic salmon (Salmo salar) were evaluated. The influence of the type of denaturation treatment (heating or sonication) was also studied. The addition of microbial transglutaminase to the coatings did not significantly modify the yields, drip losses, colour and chemical composition of the fish fillets. The yields were higher in the samples protected with heated coatings than in those with ultrasound-treated ones. Transglutaminase addition to heated whey protein coatings delayed lipid oxidation. Ultrasound-treated coatings with or without enzyme addition were equally effective for lipid oxidation reduction after frozen storage of Atlantic salmon than heated-treated transglutaminase-added coatings.     

Freezing, thawing and cooking effects on quality profile assessment of green beans (cv. Win)

Results are presented of the effect of freezing followed by thawing (air and water immersion, both at environmental temperature) and cooking (traditional boiling in a covered pot) on quality profile (in terms of objective texture, colour, chlorophylls and pheophytins and sensory attributes) and structure of green beans (cv. Win). Freezing was carried out at three different rates by forced convection with liquid nitrogen vapour. Kramer shear cell (KSC) and Warner–Bratzler (WB) tests were used for objective assessment of the texture. The highest parameter values occurred in beans frozen at the highest rate and air-thawed at the slowest rate. Also, minimum alteration of the rheological behaviour of cooked beans was achieved by freezing at the highest rate. The best parameter for assessing the texture of frozen green beans after thawing and cooking was the Warner–Bratzler slope (S _WB). Coefficients of softening estimated for S _WB in the thawed beans showed that the texture of the beans frozen at −24 °C was almost four and almost five times softer than that of the beans frozen at −70 °C, for air and water thawing respectively. Frozen and thawed green beans were darker than fresh control, whereas freezing prior to cooking produced lighter-coloured beans than direct cooking. The freezing rate affected colour parameters differently depending on the process that followed. When beans were thawed, increasing the freezing rate produced lighter-coloured beans, whereas when beans were cooked, increasing the rate produced darker-coloured beans. No difference was found in sensory assessments between cooked samples frozen at −24 °C, −35 °C and −70 °C, which probably reflects the panellists' mixed preferences for quickly and slowly frozen samples. Scanning electron microscopy (SEM) revealed different degrees of mechanical damage to tissue structure, which accounted for the rheological behaviour of the beans.     

复合无磷保水剂对反复冻融鲟鱼片理化特性及微观结构的影响

为研究反复冻融条件下复合无磷保水剂对鲟鱼片理化特性及微观结构的影响,以蒸馏水处理作为空白对照组,将碳酸氢钠、柠檬酸钠和山梨糖醇浸泡的鲟鱼片作为处理组,分别进行5 次冻融,并对不同处理组鲟鱼片的解冻损失率、蒸煮损失率、pH值、硫代巴比妥酸（thiobarbituric acid,TBA）值、肌原纤维蛋白溶解度、Ca2＋-ATPase活性、质构特性等指标进行测定,同时比较鲟鱼片的微观组织结构。结果显示,随着冻融次数的增加,鲟鱼片的解冻损失率、蒸煮损失率、TBA值均显著上升（P＜0.05）,保水剂速冻处理组上升速率低于缓冻处理组低于空白对照组;各组鱼片pH值均呈现出先下降后升高趋势;水分含量、肌原纤维蛋白溶解度、Ca2＋-ATPase活性、硬度和弹性均显著降低（P＜0.05）,保水剂处理组各项指标下降速率均低于空白对照组;组织切片图显示保水剂处理能较好地保持鲟鱼片的微观组织结构。因此,使用由碳酸氢钠、柠檬酸钠和山梨糖醇复合的无磷保水剂对反复冻融条件下鲟鱼片的品质劣变有明显抑制作用。     

Freezing/defrosting/frying of sardine fillets. Influence of slow and quick defrosting on protein quality

The effect of sequential freezing/defrosting/frying on protein quality is not well known. With this in mind, fillets of fresh sardine were stored frozen, then thawed, either conventionally at 4 °C in a refrigerator or with the use of a microwave oven, and subsequently deep‐fried. Proximate and amino acid compositions, protein solubility in sodium dodecyl sulphate/β‐mercaptoethanol (SDS/β‐ME), total ? SH group content and amino acid chemical score were determined. The lowest protein concentration was observed in frozen/4 °C‐thawed sardines (CR), whilst the lowest fat content was found in both fresh/fried sardines (F) and 4 °C‐thawed/fried sardines (CF). Every step of each process studied caused a decrease in cyst(e)ine; the most important loss was recorded in CF samples and in frozen sardines fried without defrosting (Fro‐F). The lowest solubility in SDS/β‐ME and the lowest total ? SH group content were observed for Fro‐F samples and microwave‐thawed/fried sardines (MF). On the other hand, the lowest chemical score was found for Fro‐F, CF and MF samples. Although weight loss and proximate composition seemed to change less when defrosting sardine fillets using a microwave oven rather than at 4 °C, the results for SDS/β‐ME solubility and total ? SH group content suggest that a slow defrosting process (refrigerator at 4 °C) is preferable to a much quicker process (microwave oven) for thawing frozen sardine fillets before frying. Copyright © 2003 Society of Chemical Industry     

Composition, Liquid Leakage, and Mechanical Properties of Farmed Rainbow Trout: Variation Between Fillet Sections and the Impact of Ice and Frozen Storage

ABSTRACT: Variation in quality characteristics within rainbow trout fillets, and changes in liquid leakage (LL) and mechanical properties during ice or frozen storage was studied. Fat, water, protein, and ash content, determined in frozen thawed samples, varied significantly among fillet sections. LL increased in the cranial-caudal direction, and it was highest following freezing. Dorsally, compression and puncturing resistance increased towards the tail (raw and baked), but puncture resistance of raw fillets was highest in the belly flap. The results indicated pronounced softening of the tail-half upon freezing. It is suggested that sectioning of trout fillets for different products or markets may improve utilization of intrinsic quality characteristics.     

Effects of Freezing on Quality of Cold-smoked Salmon Based on the Measurements of Physiochemical Characteristics

ABSTRACT: How the quality of cold-smoked Atlantic salmon ( Salmo salar ) is affected by freezing the raw fish as whole fish, as gutted fish, and as fillets before smoking, and by freezing the finished product after smoking was studied. Freezing before smoking resulted in increased product yield and water content, but softer texture and increased K-value. Freezing reduced the content of astaxanthin but increased the lightness and the color intensity of the flesh. Gaping increased when the fish was frozen as fillets before smoking. Freezing only after smoking led to fewer changes in quality than freezing before smoking, whereas refreezing the finished products had little additional effect on quality.     

Comparison of physicochemical and sensory changes in fresh and frozen herring (Clupea harrengus L.) during marinating

BACKGROUND: The influence of freezing on the changes during ripening is better described for salted fish than marinades. Therefore in the present study the effect of preliminary freezing of raw material on the ripening of carcasses and fillets marinated during 18 days at a temperature of 10 °C, in brine with 6% salt and 5% acetic acid was examined. RESULTS: In both cases the marinating of thawed frozen material resulted in larger mass losses and decrease of the value of meat colour parameters. The semi‐marinades from raw herring were characterised by higher values of total estimation based on sensory analysis. The statistical analysis showed weak correlation between the discriminants of sensory assessment and the studied physicochemical parameters of semi‐marinades. CONCLUSIONS: These results suggest that the semi‐marinades from raw fish are characterised by higher sensory quality, better colour parameters and higher yield than those from frozen thawed fish. Copyright © 2010 Society of Chemical Industry     

TEXTURE OF CULTURED GILTHEAD SEA BREAM (SPARUS AURATA): INSTRUMENTAL AND SENSORY MEASUREMENT

The texture of twelve samples of farmed gilthead sea bream (Sparus aurata) from experimental and commercial cultures, fresh and frozen, was determined by instrumental texture profile analysis (TPA) of whole raw fish and by sensory analysis of the corresponding cooked fish fillets. Average values of TPA hardness and chewiness were higher for fresh samples (78.0 N and 41.9 N, respectively) than for frozen and thawed samples (43.5 N and 21.5 N, respectively). The effect of freezing on springiness and cohesiveness values was different depending on the sample (a significant sample × freezing interaction). By sensory analysis, higher firmness, chewiness and fibrousness, and less juiciness were detected in frozen samples. Only one sample was perceived as less chewy, less fibrous and more juicy than the rest, and that corresponded to the smallest (less mature) fish. High percentages of the variability of sensory firmness (92%), chewiness (91%) or juiciness (85%) were explained by several of the TPA parameters measured on the raw whole fish using a fast nondestructive test.     

THE BIOCHEMICAL AND SENSORY PROPERTIES OF GILTHEAD SEA BREAM (SPARUS AURATA) FROZEN AT DIFFERENT CHARACTERISTIC FREEZING TIMES

ABSTRACT

Skinned, vacuum‐packed, postrigor gilthead sea bream fillets were frozen individually with characteristic freezing times of 2, 18, 74 and 640 min (times to cool the thermal center of the fillets from ?1 to ?7C). Immediately after freezing, the fillets were thawed, and their quality was evaluated with tests related to muscle integrity, myofibrillar protein denaturation and aggregation, lipid degradation and changes in tenderness. The muscle integrity indices (activities of α‐glucosidase, β‐N‐acetyl‐glucosaminidase and (β‐hydroxy‐acyl‐coenzyme‐A dehydrogenase and the amount and protein content of centrifugal tissue fluids) showed that the freezing process itself clearly affected the integrity of muscles. Freezing of fillets with characteristic freezing time of 74 min caused more damage to muscles and hydrolysis of lipids than the other freezing times. Adenosine triphosphatase (ATP) ase activities and Ca²⁺ sensitivity of actomyosin extracts suggested that the freezing process itself, but not the freezing times, caused structural damage to myofibrillar proteins. No difference in the levels of salt‐soluble proteins and sulfhydryl contents in actomyosin extracts was found between the fresh and frozen fillets. Sensory evaluations showed that the cooked frozen fillets were less tender than the cooked fresh ones.

PRACTICAL APPLICATION

In commercial seafood industries, seafoods are frozen at a range of freezing times (rates) that depends mostly on the type of seafood, the type of freezer and freezer's operating conditions. Based on the work reported in the literature, freezing of seafoods at different freezing times may furnish favorable conditions for alterations in muscle structure, muscle proteins and lipids, and textural properties in general. These changes are related to alterations in quality of frozen seafoods and may affect their market. Therefore, knowledge of optimal conditions with respect to freezing rates for freezing commercially important seafoods, as farmed gilthead seabream is, is relevant to the seafood industry. This information can be obtained by experimental studies on changes in the chemical, biochemical, physical and sensory properties of seafoods frozen at different freezing times.

     

Effect of freezing on the physicochemical, textural and sensorial characteristics of salmon (Salmo salar) smoked with a liquid smoke flavouring

This study reports the effect of different refrigeration/freezing treatments on the physicochemical, textural and sensorial properties of farmed Atlantic salmon (Salmo salar) treated with a commercial liquid smoke flavouring. Observations were made on three groups of fillets - group RFS: salted, smoked and stored at 4 °C; group BFS: frozen at −25 °C for 24 h, thawed, salted, smoked and stored at 4 °C; and group AFS: salted, smoked and frozen at −25 °C for 24 h and stored at −18 °C - over a period of 45 days. Scores (on a scale of 1-9) were provided for different sensorial attributes by a panel of 10 trained tasters. Sixty percent of the panellists consistently preferred the AFS fillets. The maximum shelf life associated with each treatment was defined as the last sampling day on which a mean score of ≤5 was awarded for the fillet sensorial attributes by ≥50% of the panellists. Freezing the salmon for 24 h before smoking (BFS) did not increase its shelf life (30 days) over that of refrigerated smoked salmon (RFS). In addition, the former treatment had a negative effect on the adhesiveness, cohesiveness, smoke odour intensity and colour intensity of the flesh. However, maintaining the fish frozen at −18 °C (AFS) increased its shelf life (>45 days) and invested the flesh with greater firmness, cohesiveness and colour intensity.     

Effect of freezing/thawing conditions and long‐term frozen storage on the quality of mashed potatoes

The effects of freezing temperature (−80, −40 or −24 °C) and thawing mode (microwave or overnight at 4 °C) on quality parameters of mashed potatoes made from tubers (cv Kennebec) and from potato flakes were examined, as was the effect of long‐term frozen storage on the quality of mashed potatoes. Mashed potatoes were tested for texture profile analysis (TPA) and cone penetration, oscillatory and steady rheometry, colour, dry matter, Brix and sensory analyses. In natural mashed potatoes, TPA hardness and oscillatory parameters showed that processing resulted in a softer product than the fresh control. The parameters were lower in the samples thawed at 4 °C than in those thawed by microwave at all the freezing temperatures used, which may be ascribed to gelatinisation of the starch released from damaged cells. Differences from the freshly prepared product decreased when the samples were frozen at −80 °C and thawed by microwave. No difference was found in sensory acceptability between samples frozen at −80 and −40 °C, which probably reflects the panellists' mixed preferences for air‐thawed versus microwave‐thawed samples. Increasing the time in frozen storage led to a natural mash with a firmer texture, higher L*/b* value and Brix; nonetheless, panellists found the samples at 0, 3 and 12 months of frozen storage equally acceptable. In commercial mash, penetration and oscillatory parameters showed that processing made for a firmer product than the fresh control, probably owing to retrogradation of gelatinised starch. Thawing mode had a significant effect on parameters, which were lower in the samples thawed at 4 °C. The structure and quality of commercial mash was more detrimentally affected by freezing and, therefore, we would not recommend either freezing or frozen storage of this mashed potato in the used conditions. Natural mash made from Kennebec potatoes should be frozen quickly and thawed by microwave in the conditions described to obtain a product more similar to that freshly made. If the samples are frozen by air blasting at −40 °C, the product can withstand frozen storage for one year. Copyright © 2005 Society of Chemical Industry     

Effect of modified starch concentration and freezing and thawing rates on properties of mashed potatoes (cv. Kennebec)

Effects of modified cornstarch concentration, freezing rate and thawing mode on quality properties of mashed potatoes were examined. The product was tested by oscillatory rheometry, instrumental texture profile analysis (ITPA) and cone penetration, colour, dry matter (DM) and sensory analyses. Oscillatory parameters showed that increasing starch concentration resulted in a softer product in which gel strength decreased in direct proportion to concentration in quick‐frozen and microwave‐thawed product. Quick freezing made for firmer mashed potatoes, whereas oscillatory, ITPA and penetration parameters were lower in the samples thawed at 4 °C. Starch concentration and instrumental consistency and firmness were directly proportional to one another. Adding starch at the highest concentration, quick freezing and slow thawing produced a lighter‐coloured mashed potato, although the loss of colour in the processed product was not detected by panellists in the microwave‐thawed samples. DM was higher in the quick‐frozen samples and lower in air‐thawed samples. The factors studied affected different sensory texture parameters but had hardly any effect on attributes perceived during final and residual phases of mastication. Only starch concentration had a significant effect on sensory acceptability, but interactions between factors showed that starch addition followed by quick freezing was judged undesirable by the panellists due to excessive softening. Oscillatory parameters correlated well with sensory texture attributes and proved quite precise. They would therefore appear to be the best test to monitor properties of frozen mashed potatoes. Copyright © 2007 Society of Chemical Industry     

A method for identification of frozen meat used for production of cooked ham

A simple method to distinguish if the meat used for production of cooked hams was frozen or unfrozen was developed. Several analytical parameters of quality in meat products (general and colour parameters and protein fraction) were determined in two types of cooked hams: one elaborated with refrigerated (R) and another with frozen and thawed (F/T) raw hams. Student's t-test was applied to compare both groups, but it could not be concluded if R and F/T cooked hams had the same quality or not. For this reason two multivariate statistical analyses, Factor (FA) and Discriminant Analysis (DA), were applied. The application of FA resulted in the separation of the two groups of cooked hams and allowed the selection of the parameters which were used in Discriminant Analysis (DA). A discriminant function, that is both easy to use and to interpret, was obtained.     

Quality changes during the frozen storage of sea bass (Dicentrarchus labrax) muscle after pressure shift freezing and pressure assisted thawing

Quality of frozen sea bass muscle stored (1, 3 and 5 months) at two levels of temperature (−15 and −25 °C) after a pressure shift freezing process (200 MPa) — PSF — and/or a pressure assisted thawing process (200 MPa) — PAT — was evaluated in comparison with samples frozen and thawed using conventional methods (air-blast AF and AT, respectively). Frozen storage of high-pressure treated samples did not significantly affect initial quality of frozen muscle. Thus, parameters related to protein denaturation and extractability, water holding capacity and color presented similar values than those obtained for not stored samples. In addition, the improvement of the microstructure achieved by PSF application remains unchanged during frozen storage. On the other hand, conventional treated samples experienced significant changes during frozen storage, such as protein denaturation, and water holding capacity and color modifications. Storage temperatures did not have influence in the quality of PSF and PAT samples, but it showed some effects in AF muscle.Industrial relevance: This work demonstrates the potential application and benefits of high pressure (HP) in the freezing and thawing of fish meat in comparison to conventional methods, due to an improvement on the cellular integrity of the tissue. Although some negative effects are produced during processing with HP, no additional modifications occur during the frozen storage. The studied methodologies seemed to be very suitable for fish freezing and thawing, especially for products which will be frozen stored and/or cooked.     

Development of an enzymatic method to differentiate fresh and sea-frozen and thawed fish fillets. I. Comparison of the applicability of some enzymes of fish muscle

The activities of mitochrondrial and lysosomal enzymes in press juices of fresh and frozen and thawed fillets were compared. It was demonstrated that several lysosomal enzymes are suitable for the detection of thawed fillets, because their activities in press juice increased considerably in consequence of freezing and thawing fish fillets.     

Effects of freezing/thawing on the microstructure and the texture of smoked Atlantic salmon (Salmo salar)

The changes in microstructure and texture during smoking of fresh and frozen/thawed Atlantic salmon was studied in fish from three different origins; ocean-ranched Atlantic salmon (Salmo salar) from Iceland and two groups of farmed Atlantic salmon from northern and western Norway. The muscle fibers from the frozen and thawed fish shrank, and the extracellular space increased compared to the fresh muscle. The muscle fibers from salmon fillets with smaller fiber diameter shrank to a less extent than fibers from salmon material with a larger fiber diameter. After smoking the space between the fibers and the fiber shrinkage increased to a higher extent in the muscle from the salmon that were frozen prior to smoking than muscle smoked from fresh salmon. The initial cross-sectional area of the fibers was not found to be related to the yield during smoking.     

Effect of Freezing of Beef on Subsequent Postmortem Aging and Shear Force

Seventy-two steaks were used to determine effects of freezing postrigor muscle on aging of meat and shear force. Steaks were removed from each carcass 24 hr postmortem and aged at 2°C for 2 or 6 days; or frozen at ? 30°C for 27 days, thawed 24 hr and aged 2 or 6 days at 2°C. After aging, steaks were cooked and shear force determinations made. Aging of meat reduced shear force values; however, meat aged after freezing had lower (P < 0.03) shear force values than meat aged before freezing. Meat cooked after freezing had greater (P < 0.05) cooking losses. Freezing enhances the aging process and improves shear values of meat.     

Effect of Phosphate Blends on Stability of Cod Fillets in Frozen Storage

Atlantic cod fillets were dipped in commercial tripoly or metaphosphate solutions, frozen and stored at either –12 ° 0.5°C or –30°C (constant or with daily programmed fluctuations to ?26°C) for up to 26 wk. Phosphate treatments at both storage temperatures decreased thaw drip and cooked drip and yielded a product with higher raw and cooked moisture. Protein content of cooked drip from fillets stored at –12°C was reduced by phosphate treatment; no significant difference was found between treated and control samples at –30°C. Although salt extractable protein was lowered, phosphate treatment did not affect dimethylamine/formaldehyde formation. Sensory evaluation of treated fillets stored at –30°C (with daily fluctuation to –26°C) revealed phosphated fillets to be the most tender and, after 26 wk storage, the most highly acceptable. Tripolyphosphate treatment significantly retarded the increase of expressible fluid under abusive conditions of frozen storage.