The effects of freezing on flesh proteins

Metabolomic profile of muscles from tilapia cultured in recirculating aquaculture systems and traditional aquaculture in ponds and protein stability during freeze-thaw cycles

Muscle protein stability during freeze-thaw (F-T) cycles was investigated with tilapia cultured in recirculating aquaculture systems (RAS) and traditional aquaculture in ponds (TAP). This study found that fatty acids (eg., palmitic acid) were enriched in TAP, while antioxidants (eg., glutathione) were enriched in RAS. Generally, proteins in the RAS group exhibited greater stability against denaturation during the F-T cycle, suggested by a less decrease in haem protein content (77% in RAS and 86% in TAP) and a less increase in surface hydrophobicity of sarcoplasmic protein (63% in RAS and 101% in TAP). There was no significant difference in oxidative stability of myofibrillar protein between the two groups. This study provides a theoretical guide for the quality control of tilapia cultured in RAS during frozen storage.

Evidence of myofibrillar protein oxidation and degradation induced by exudates during the thawing process of bighead carp fillets

Oxidation of myofibrillar proteins (MPs) is considered as an important reason for the quality deterioration of frozen stored fish fillets, but the impact of the thawing process on the oxidation and thereby property changes of MPs has been largely neglected. In this study, we incubated MPs for 24 h at 4 °C with thawing exudates collected from fish fillets stored at -20 °C for 0-5 months to mimic the thawing process. Exudates treatment induced the increased content of carbonyls, Schiff bases, and dityrosine, structural changes, and the decreased water-holding capacity of MPs. SDS-PAGE and LC-MS/MS results indicated that exudates caused the degradation of MPs with the potential involvement of lipid oxidation products, hemoglobin, and proteases. Prolonged frozen storage decreased antioxidant enzyme activity and increased lipid oxidation products in exudates, which might be the reason for exudates from fillets frozen for longer periods can cause more severe oxidation and degradation of MPs.

Postmortem histological freeze-thaw artifacts: a case report of a frozen infant and literature review

Freezing and thawing have the potential to alter the gross and histologic appearance of tissues, causing damage to individual cells and disrupting the overall architecture. In forensic investigations, freezing and thawing can play a crucial role in cases of unknown cause of death. Perpetrators may use freezing preservation to conceal the body or obscure the time of death. Freezing can also occur naturally when a body is exposed to the elements, sometimes even leading to death itself. We present a case report involving an autopsy performed on an infant, who died of natural causes, after undergoing freezing and thawing. The objective of this study was to identify and discuss the histological artifacts observed in different tissues as a result of the freeze-thaw process. Histologically, the infant's tissues exhibited the most common features described in the literature. Ice crystal artifacts, characterized by expansion of the extracellular space and tissue clefts, were found in the heart, brain, liver, lungs, and kidneys. On the contrary, adipose tissue was not affected, likely due to the scarcity of water. Freeze-thaw artifacts should be taken into account whether a body is known to have been frozen or to add further data if found already defrosted.

Effects of Ultrasound-Assisted Immersion Freezing on the Protein Structure, Physicochemical Properties and Muscle Quality of the Bay Scallop (Argopecten irradians) during Frozen Storage

In this study, the comparison effects of ultrasound-assisted immersion freezing (UIF) at different ultrasonic power, immersion freezing (IF), and air freezing (AF) on the protein thermal stability, protein structure, and physicochemical properties of adductor muscle of scallop (Argopecten irradians) (AMS) during frozen storage were investigated. Principal component analysis and the Taylor diagram were used to comprehensively analyze all the indicators tested. The results showed that the UIF at 150 W (UIF-150) treatment was the most effective way to delay the quality deterioration of AMS during 90-day frozen storage. This was mainly because, compared to AF and IF treatments, UIF-150 treatment more effectively minimized the changes in the primary, secondary and tertiary structures of myofibrillar proteins, and it preserved the protein thermal stability of AMS by producing small and regular ice crystals in the AMS tissue during the freezing process. Moreover, the results of physicochemical properties indicated that UIF-150 treatment significantly inhibited the fat oxidation and microbiological activities of frozen AMS, and it finally maintained the microstructure and texture of AMS during frozen storage. Overall, UIF-150 has potential industrial application prospects in the rapid freezing and quality preservation of scallops.

Identification of freeze-thaw artifact in fresh and decomposed black rockfish (Sebastes melanops) and steelhead trout (Oncorhynchus mykiss)

Identification of freeze-thaw artifact in fish can help to determine whether they have been harvested within the appropriate season and monitor adherence to fishing regulations. Recognition of freeze-specific changes will also prevent potential misinterpretation due to decomposition, disease, injury, or species variation. An initial survey using black rockfish (Sebastes melanops) identified which tissues reliably exhibit freeze artifact. Tissues were exposed to different treatments: immediate formalin fixation; refrigeration or storage at room temperature for 24, 48, or 72 hours; or freezing for 1, 8, or 28 days. Three fish underwent a combination of treatments. Tissue changes in each treatment group were compared macroscopically and microscopically. Macroscopic changes in frozen-thawed and never-frozen fish overlapped somewhat; however, microscopic findings of skeletal myocyte cavitation, lens liquefaction, and brain tissue fractures were consistent findings only in frozen-thawed tissues. A validation study was then done to establish the accuracy of microscopic analysis. Brain and paired ocular and skeletal muscle samples from 61 steelhead trout (Oncorhynchus mykiss) were fixed in formalin either fresh or after being frozen for 4 weeks. Weighted kappa values showed both high observer accuracy and interobserver agreement in the identification of freeze-thaw status. Based on these findings, microscopic changes in the skeletal muscle, eye, and brain are considered consistent and easily identifiable indicators of a previous freeze-thaw cycle and should not be confused with a pathologic process.

Metal deposition and shape reproduction at biological temperatures on cell-level samples

The use of metal deposition has been limited to a limited number of applicable samples due to the increased temperature caused by accelerated electron impact on the substrate surface. The surfaces of various biological samples have a nanoscale structure with specific properties, which have been simulated in numerous studies. However, no examples of nano/microscale reproductions of biological surface features have used moulds. In this study, a mould that imitates the surface shape of a cellular-level biological material was fabricated, for the first time, and the shape was successfully reproduced using the mould. Al thin films were deposited on bovine sperm using magnetron sputtering without thermal denaturation with a cathode operating at a biological temperature. It is difficult to deposit films used as metal coatings on pre-treated biological materials at temperatures below 40 °C during evaporation. The Al thin film was peeled off and used as a mould to reproduce the shape of the sperm with high accuracy using a polymer. The results of this study represent a major innovation in reproducible biomimetic moulding technology, demonstrating biological temperature sputtering. We expect our non-destructive metal deposition and metal nano-moulding methods for biological samples to be the basis for the effective utilization of various biological structures.

Freeze-Chilling of Whitefish: Effects of Capture, On-Board Processing, Freezing, Frozen Storage, Thawing, and Subsequent Chilled Storage-A Review

The current review investigates how whitefish quality is affected by capture at sea, on board handling, freezing, double freezing, frozen storage, thawing, and chilled storage. Packaging of fillets in MAP and vacuum are also covered. The main goal was to evaluate the freeze-chilling concept as a possible method for the fishing industry for all-year-round marketing of fish captured during the relatively short fishing period. The review covers both the effect of each processing step in the supply chain as well as the combined effect of all steps in the chain from sea to consumer, including post-thawing chilled storage, defined as the freeze-chilling method.

Freezing of meat and aquatic food: Underlying mechanisms and implications on protein oxidation

Over the recent decades,protein oxidation in muscle foods has gained increasing research interests as it is known that protein oxidation can affect eating quality and nutritional value of meat and aquatic products. Protein oxidation occurs during freezing/thawing and frozen storage of muscle foods, leading to irreversible physicochemical changes and impaired quality traits. Controlling oxidative damage to muscle foods during such technological processes requires a deeper understanding of the mechanisms of freezing-induced protein oxidation. This review focus on key physicochemical factors in freezing/thawing and frozen storage of muscle foods, such as formation of ice crystals, freeze concentrating and macromolecular crowding effect, instability of proteins at the ice-water interface, freezer burn, lipid oxidation, and so on. Possible relationships between these physicochemical factors and protein oxidation are thoroughly discussed. In addition, the occurrence of protein oxidation, the impact on eating quality and nutrition, and controlling methods are also briefly reviewed. This review will shed light on the complicated mechanism of protein oxidation in frozen muscle foods.

A freeze-and-thaw-induced fragment of the microtubule-associated protein tau in rat brain extracts: implications for the biochemical assessment of neurotoxicity

Tau is a microtubule-associated protein (MAP) responsible for controlling the stabilization of microtubules in neurons. Tau function is regulated by phosphorylation. However, in some neurological diseases Tau becomes aberrantly hyperphosphorylated, which contributes to the pathogenesis of neurological diseases, known as tauopathies. Western blotting (WB) has been widely employed to determine Tau levels in neurological disease models. However, Tau quantification by WB should be interpreted with care, as this approach has been recognized as prone to produce artifactual results if not properly performed. In the present study, our goal was to evaluate the influence of a freeze-and-thaw cycle, a common procedure preceding WB, to the integrity of Tau in brain homogenates from rats, 3xTg-AD mice and human samples. Homogenates were prepared in ice-cold RIPA buffer supplemented with protease/phosphatase inhibitors. Immediately after centrifugation, an aliquot of the extracts was analyzed via WB to quantify total and phosphorylated Tau levels. The remaining aliquots of the same extracts were stored for at least 2 weeks at either −20 or −80°C and then subjected to WB. Extracts from rodent brains submitted to freeze-and-thaw presented a ∼25 kDa fragment immunoreactive to anti-Tau antibodies. An in-gel digestion followed by mass spectrometry (MS) analysis in excised bands revealed this ∼25 kDa species corresponds to a Tau fragment. Freeze-and-thaw-induced Tau proteolysis was detected even when extracts were stored at −80°C. This phenomenon was not observed in human samples at any storage condition tested. Based on these findings, we strongly recommend the use of fresh extracts of brain samples in molecular analysis of Tau levels in rodents.

Comparative effect of a previous 150-MPa treatment on the quality loss of frozen hake stored at different temperatures

BACKGROUND

This study addresses the quality loss of European hake (Merluccius merluccius) during frozen storage. Its objective was to comparatively analyse the effect of a previous high-pressure processing (HPP) (150 MPa for 2 min) when different storage temperatures (-10, -18 and -30 °C) were employed.

RESULTS

Most chemical quality indices (trimethylamine, TMA; dimethylamine, DMA, formaldehyde, FA; free fatty acids, FFAs) provided a marked content increase with freezing and frozen storage time, values being higher by increasing the storage temperature. Previous HPP led to an inhibitory (P < 0.05) effect on the TMA, DMA, FA and FFA formation in frozen fish kept at -10 and -18 °C, the preservative effect being higher at the highest temperature tested; however, in agreement to the low damage development, no effect could be proved on samples stored at -30 °C. Concerning lipid oxidation, peroxides formation was found low, although a slight increasing effect (P < 0.05) was implied in fish corresponding to all temperatures as a result of the previous HPP; furthermore, an inhibitory effect (P < 0.05) on fluorescent compounds formation (tertiary lipid oxidation) was evident after freezing and at month 9 for -10 °C samples.

CONCLUSION

It is concluded that a 150-MPa high-pressure treatment may inhibit the formation of degradative molecules such as DMA, FA, TMA and FFAs during the frozen storage at -18 °C (maximum recommended) and -10 °C. However, results have indicated that lowering the storage temperature showed to be more effective than the current HPP (150 MPa for 2 min). © 2020 Society of Chemical Industry.

Differentiation of fresh and thawed Atlantic salmon using NMR metabolomics

NMR metabolomics approach was used to distinguish fresh and thawed Atlantic salmon. Statistical analysis revealed significant differences in the concentration of some metabolites in reference and frozen-thawed fish during its storage. It was found that salmon freezing/thawing caused a significant increase in the concentration of fumarate and phenylalanine in stored salmon muscle. The concentration of fumarate increased until the 3rd-5th day after thawing and then gradually decreased, reaching zero after two weeks of storage. The concentration of phenylalanine was constantly increased during the storage time. Furthermore, it was detected that aspartate was formed in the flesh of only thawed fish after the second day of storage. Its concentration followed the same trend as fumarate reaching its maximal concentration on the 3rd-5th day after thawing (up to 3.8 mg in 100 g of muscle) and gradually decreased to zero. Aspartate formation was influenced by storage time after thawing and not by the time after slaughter. We propose to use the formation of aspartate in stored salmon flesh as a marker of salmon freezing/thawing.

Impact of pretreatment and atmosphere on quality of lipids extracted from cephalothorax of Pacific white shrimp by ultrasonic assisted process

Impacts of different pretreatment conditions and atmosphere on yield and oxidative stability of lipids from Pacific white shrimp (Litopenaeus vannamei) cephalothorax using ultrasonic assisted extraction (UAE) process were studied. Cephalothorax was subjected to vacuum-microwave (VM) heating prior to UAE using a mixture of isopropanol/n-hexane (1:1) as solvent. Nitrogen gas was flushed at two flow rates; low (2.15 l/min) and high (4.35 l/min) into the system during ultrasonication. Vacuum-microwave heating resulted in the increase of lipid yield and highest yield was observed in the samples extracted by a combination of VM and UAE. Tannic acid (TA) was incorporated into cephalothorax at three different levels (0.05, 0.1 and 0.2%) in combination with VM, followed by nitrogen flushing. Nitrogen flushing during ultrasonication process resulted in the increased oxidative stability of lipids as confirmed by low PV, TBARS and FFA. Furthermore, astaxanthin content in the lipid was found to be increased by aforementioned treatments.

Changes in the Quality of Chicken Breast Meat due to Superchilling and Temperature Fluctuations during Storage

The aim of this study was to determine the changes in chicken breast meat quality (water-holding capacity, color, texture, myofibrillar fragmentation index (MFI), total protein solubility, thiobarbituric acid reactive substances (TBARS), total viable count (TVC), and lactic acid bacteria (LAB) count) due to storage under superchilling conditions (−1.3°C) and fluctuating temperatures (ranging from −20°C to −5°C) as compared to the quality of meat stored at chilled (2–4°C) and frozen (−20°C) temperatures, respectively. Results indicated that the TVC and LAB count of the chilled and superchilled breast meat increased with storage time. TVC of the chilled and superchilled breast meat reached the safety level of 7 log cfu/g at approximately day 8 and18, respectively. This suggested that the superchilling method extended the storage duration by 10 days. Weight loss and TBARS of the chilled and superchilled samples tended to increase with increasing storage time. The color, texture, protein solubility, and MFI were stable throughout the entire storage period of the chilled (9 days) and superchilled (28 days) samples. Results indicated that while three cycles of storage temperature fluctuation influenced the weight loss and dry matter of the meat, they did not affect the TVC, LAB count, texture, color, pH, MFI, and protein solubility. The superchilling technique (−1.3°C) could extend the shelf-life of meat and maintain the quality of chicken breast meat. Fluctuations in temperature during frozen storage decreased the water-holding capacity of chicken breast meat, indicating that temperature stability should be maintained during frozen storage.

Stability of Golden redfish (Sebastes marinus) during frozen storage as affected by raw material freshness and season of capture

Physicochemical changes of Icelandic golden redfish (Sebastes marinus) as affected by seasonal variation (June and November) and raw material freshness (processed 4 and 9 days postcatch) during frozen storage (at -25°C for 20 months) were studied to find optimal conditions for production of high-quality frozen products. Thawing loss, cooking yield, and color of the fillets as well as chemical composition, water holding capacity, pH, total volatile basic nitrogen, lipid oxidation, and hydrolysis of the light and dark muscle were analyzed every 4 months of frozen storage. Lipid hydrolysis was the main degradation process in the light muscle, while the dark muscle was more affected by lipid oxidation. Fish caught in November showed greater instability in the analyzed parameters during storage than fish caught in June, which could be linked to differences in individual poly unsaturated fatty acids between the two seasons. The quality attributes of fish processed on day 9 were similar to fish processed 4 days postcatch, except slightly higher thawing loss and yellowness, were observed in fish processed 9 days postcatch. Stability of golden redfish through frozen storage was higher in the fish caught in June than in November.

A comparative study of quality and safety of Atlantic cod (Gadus morhua) fillets during cold storage, as affected by different thawing methods of pre-rigor frozen headed and gutted fish

BACKGROUND

The catch of marine whitefish is typically seasonal, whereas the land-based processing industry has a need for all-year stable supply of raw materials. This challenge can be met by applying fish frozen at sea. When using frozen fish, the methods employed for thawing may influence the safety and quality of the final product. This study aimed to investigate the applicability of novel thawing strategies in order to provide an all-year supply of high-quality and safe cod products.

RESULTS

Comparative investigations of quality and safety factors after thawing in water, with and without air circulation, and contact thawing were performed. The parameters included water-holding capacity, thawing loss, drip loss, cooking yield, sensory evaluation and microbiological analyses (including total volatile bases nitrogen). Water thawing with air circulation provided faster thawing than water thawing without air circulation and contact thawing. For all three methods, the quality of the thawed fish was acceptable and the shelf life of the fillets during chilled storage was between 10 and 14 days post-filleting.

CONCLUSION

The results show that controlled freezing of cod, followed by appropriate thawing, may provide the processing industry with an all-year delivery of raw materials, without compromising quality and safety of the final product. © 2017 The Authors. Journal of The Science of Food and Agriculture published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Review: Loss of Quality during the Manufacture of Canned Fish Products

From the moment the fish is caught till it arrives at the consumer as a canned product, raw matter is submitted to a variety of industrial steps. Thus, a storage process (namely, chilling or freezing) is needed for holding the raw material to be canned; a cooking step is normally employed for reducing moisture and inactivating endogenous enzyme activity; a rigorous thermal treatment (sterilization) is undertaken to inactivate micro-organisms; and a proper canned storage is necessary to guarantee good palatability of the product. As a result, labile and essential nutrients (proteins, vitamins, lipids, minerals) present in the raw fish are exposed to different processing conditions that can reduce the nutritional and sensory values of the final product. In the present work, detrimental changes produced in each of the steps involved in the manufacture of canned products are mentioned. This review is focused on nutritional and sensory losses in species commonly employed for canning preparation, and special attention is given to research concerning the effect of varying conditions of previous processing (chilling, freezing and frozen storage and cooking) on the quality of the final canned product. New and current technological strategies are recommended to increase the shelf life of previously stored material and to retain sensory and nutritional quality in the final canned product.

Inhibition of lipid oxidation in frozen farmed ovate pompano (Trachinotus ovatus L.) fillets stored at -18 °C by chitosan coating incorporated with citric acid or licorice extract

BACKGROUND

Lipid oxidation can occur in fish fillets during long-term frozen storage and cause quality and nutrition loss, which is a major concern in the seafood industry. Our previous study showed that chitosan combined with citric acid or licorice extract can have a preserving effect on fresh fish fillets stored at 4 °C. It is of interest to further study their antioxidant effects on fish fillets during frozen storage.

RESULTS

Chitosan, chitosan and citric acid, chitosan and licorice extract can inhibit primary and secondary lipid oxidation, as indicated by lower peroxide value (PV) and thiobarbituric acid reactive substances (TBARS) values compared to the control samples. In addition, drip loss was decreased in the treatment samples. Both citric acid and licorice extract enhanced the antioxidant effects of chitosan. Among all the three treatments, chitosan and licorice extract showed the best antioxidant effects, reducing both PV and TBARS significantly at the end of storage.

CONCLUSION

The combination of chitosan and citric acid or licorice extract showed significant antioxidant effects on ovate pompano fillets at -18 °C during 6 months of storage. They could be applied as natural antioxidant preservatives for use in seafood products or other meat products. © 2015 Society of Chemical Industry.

REVISÃO: SÍNDROME DO OSSO NEGRO EM FRANGOS DE CORTE

Alguns fatores envolvidos na incidência de síndrome do osso negro e suas consequências na qualidade e aceitação da carne de coxas e sobrecoxas de frangos de corte estão descritos nesta revisão. Sabe-se que a conservação de coxas e sobrecoxas pelo congelamento leva à formação de cristais de gelo que rompem as células da medula óssea, causando extravasamento da hemoglobina presente na mesma, quando o osso está frágil ou poroso acentua-se o extravasamento de sangue que ocorre principalmente pela região proximal na tíbia e no fêmur. O escurecimento causado na carne adjacente ao osso é chamado de síndrome do osso e tem implicações na qualidade da carne, alterando principalmente a aparência da mesma devido ao escurecimento causado. O escurecimento decorrente do sangue extravasado na carne tem implicações na qualidade da mesma e pode resultar em problemas na aceitação de carne de coxa e sobrecoxa. Assim, torna-se necessário providências a longo prazo, com seleção genética focada na estrutura óssea e a curto prazo, com adição de nutrientes que podem melhorar a qualidade óssea.

Effect of multiple freeze-thaw cycles on the quality of chicken breast meat

The objective of this study was to determine the effects of repeated freeze-thaw cycles (0-6) on any physico-chemical changes and lipid and protein oxidation in chicken breast. The results showed that meat colour, a(∗) (redness) and b(∗) (yellowness) values decreased while L(∗) values (lightness) increased with increasing cycle numbers. Increasing freeze-thaw cycles resulted in a greater degree of lipid and protein oxidation, as evidenced by higher contents of malondialdehyde and carbonyl compounds, and lower contents of sulfhydryl groups. Differential scanning calorimetry profiles and SDS-PAGE banding patterns of myofibrillar proteins indicated slight denaturation of myosin and actin with repeated freeze-thaw cycles. The structural changes occurring in proteins caused by oxidation directly affected the ability of muscles to retain water, as confirmed by the nuclear magnetic resonance relaxometery profile. In conclusion, multiple freeze-thaw cycles increased lipid and protein oxidation and decreased water holding capacity and colour stability of broiler chicken breast.

Effect of frozen storage on the characteristics of a developed and commercial fish sausages

The effect of frozen storage on the physiochemical, chemical and microbial characteristics of two types of fish sausages was studied. Fish sausages developed (DFS) with a spice-sugar formulation and commercial fish sausages (CFS) were stored at -20 °C for 3 months. Fresh DFS contained 12.22% lipids and had a 3.53 cfu/g total bacteria count (TBC) whereas, CFS contained 5.5% lipids and had a 4.81 cfu/g TBC. During storage, TBC decreased significantly (p < 0.05) in DFS whereas it did not change (p > 0.05) in CFS. A peroxide value (PV) was not detectable until week four and eight of storage in CFS and DFS, respectively. The salt-soluble proteins (SSP) level was stable in DFS but in CFS it declined significantly (p < 0.05). Colour values did not change significantly (p > 0.05) in both sausage types. This study showed that the effect of storage at -20 °C on fish sausages characteristics varied between formulations and depended on the ingredients of fish sausages.