Effect of Cryoprotectants on Frozen Burbot Fillets and a Comparison with Whitefish Fillets

Burbot fillets (Lota lota) were injected with sodium tripolyphosphate (STP), sodium glutamate (MSG), a high pH buffer or an antioxidant mixture (BHA, propyl gallate and citric acid) under high pressure, then frozen and stored at ?12°C. Control samples included untreated fillets stored at ?12°C and ?60°C, and STP dipped fillets. Samples treated with STP or the high-pH buffer had better textural properties than untreated control samples. Samples injected with STP exhibited no improvement as compared to the dipped STP samples and in some respects were worse. Burbot and whitefish have very different textural properties; however, the patterns of change during frozen storage are quite similar.     

Effect of Processing and Storage on The Antioxidant Activity of Frozen and Pasteurized Shadblow Serviceberry (Amelanchier canadensis)

Serviceberry fruits were pasteurised in glass jars at two temperatures, 85 and 100°C, while another batch was packed in polyethylene bags and frozen at a temperature of ?20 ± °C. Processed fruits were stored for 10 months: frozen fruit at ?20 ± 1°C; and pasteurised fruit at room temperature without access to light. Refrigerated storage and pasteurization lowered the DPPH antioxidant activity of serviceberry fruit. In the former, the change was not great, whilst pasteurisation caused an approximately twofold increase in EC50. On the basis of total anthocyanin content and total polyphenolic content measurements, it would appear that the antioxidant properties of serviceberry were affected mainly by anthocyanins. Pasteurising at 100°C allowed slightly better preservation of these compounds during long-term storage.     

Effect of Cryoprotectants on Frozen Whitefish Fillets

Whitefish fillets (Coregonus cupleaformis) were treated with sodium tripolyphosphate (STP), monosodium glutamate (MSG) or a high-pH buffer by high pressure injection, then frozen and stored at ?12°C. Control samples included untreated fillets stored at ?12°C and ?60°C, and STP-dipped fillets (?12°C). Samples treated with STP or high-pH buffer showed better textural properties (reduced centrifugal drip, cooked drip and firmness) than untreated control samples. High pressure injection of STP was not significantly better and sometimes less effective than surface application. Sensory analysis at 18 wk revealed that STP-treated samples (?12°C) were significantly preferred over untreated control samples (?12°C) but not over ?60°C control samples.     

Rheological Behavior of Frozen and Thawed Low-Moisture, Part-Skim Mozzarella Cheese

Stress relaxation and dynamic profiles of low-moisture, part-skim (LMPS) Mozzarella cheese cylinders refrigerated 14 days (control), frozen and thawed, and stored frozen and refrigerated up to 90 days were compared. Samples were frozen at ?30°C and stored at ?20°C. Thawing and refrigerated storage were at 5°C. Stress relaxation tests were conducted at 20°C and dynamic spectrometry at 20°C and 60°C. The frozen and thawed Mozzarella cheese tested at 20°C became harder and more elastic with storage time, while refrigerated stored samples became softer and more elasticoviscous with time. Upon melting, both go-day-frozen and go-day-refrigerated cheeses were less elastic and less viscous than 14-day-refrigerated samples.     

Color stability of frozen whole tilapia exposed to pre‐mortem treatment with carbon monoxide

BACKGROUND: Color of muscle foods plays a major role in consumer perception of meat quality. Carbon monoxide (CO) has been successfully used for improving color of packaged meat and fish products. In this study, we wanted to investigate pre‐mortem treatment of live tilapia using 100% CO for its ability to improve the color of frozen whole tilapia. We compared untreated and CO‐treated whole, gutted tilapia, frozen for 2 and 4 months at ? 20 °C. Frozen tilapia samples were thawed overnight at 4 °C, filleted and analyzed for their color, heme peak wavelength and CO concentration. RESULTS: Euthanasia using CO significantly increased redness (a* value) and lightness (L* value) of tilapia white and red muscle. Frozen storage significantly (P < 0.05) decreased redness of both CO‐treated and untreated tilapia. However, even after 4 months of frozen storage, a*‐value of CO‐treated tilapia was similar to fresh untreated tilapia fillets. Heme peak wavelengths of CO‐euthanized tilapia were higher than in untreated tilapia and there was no significant (P > 0.05) decrease in heme peak wavelengths of CO‐treated tilapia white and red muscle during frozen storage. The CO content of frozen euthanized tilapia fillets was significantly (P > 0.05) higher than in untreated fillets. In general, red muscle tissue of euthanized tilapia had a higher concentration of CO than white muscle. CONCLUSION: Color stability of tilapia fillets was significantly improved by pre‐mortem CO treatment. The color of CO‐treated fillets was retained during frozen storage compared to untreated fillets. Hence, pre‐mortem CO treatment could be used as a new method for improving color of tilapia. Copyright © 2008 Society of Chemical Industry     

Continuous dense‐phase CO2 processing of a coconut water beverage

Effects of dense‐phase CO₂ (DPCD) on microbial, physical, chemical and sensorial quality of coconut water (CW) beverage were evaluated. Pressure during DPCD treatment was not significant in microbial reduction whereas temperature and % CO₂ levels were significant. DPCD‐treated (34.5 MPa, 25 °C, 13% CO₂, 6 min), heat‐pasteurised (74 °C, 15 s) and untreated CW beverages were evaluated during 9 weeks of refrigerated storage (4 °C). Total aerobic bacteria of DPCD and heat‐treated samples decreased whereas that of untreated samples increased to >10⁵ CFU mL^?1 after 9 weeks. DPCD increased titratable acidity but did not change pH (4.20) and °Brix (6.0). Likeability of DPCD‐treated CW was similar to untreated. Heat‐treated samples were less liked (α = 0.05) at the beginning of storage. Off flavour and taste‐difference‐from‐control scores of heated samples were higher than DPCD during the first two weeks. DPCD extended shelf life of acidified, sweetened and carbonated CW over 9 weeks at 4 °C.     

Effect of modified atmosphere packaging on oxidative changes in frozen stored cold water shrimp (Pandalus borealis)

Shrimps caught at sea were boiled in seawater, air blast or nitrogen frozen, glazed and then packed in plastic bags with a low oxygen transmission rate. The bags were either flushed with nitrogen (modified atmosphere packaging) or with atmospheric air before sealing. The shrimps were then stored for up to 12 months in a freezer cabinet at −17°C with fluctuating temperatures. During storage they were either exposed to fluorescent light or kept in darkness. To investigate the effect of fluctuating temperatures some of the modified atmosphere-packed shrimps were stored in darkness in a cold store at a constant temperature of −18°C. Quality changes were determined by sensory evaluation combined with chemical/physical analyses, including determination of the pigment astaxanthin and measurement of the oxidative stability by determination of thiobarbituric acid-reactive substances (TBARS). Packaging in modified atmosphere resulted in overall better quality in relation to colour fading, development of rancid flavour and toughening of the meat. Light exposure influenced both colour fading and lipid oxidation negatively. Temperature fluctuations resulted in very pronounced formation of frost in the packages. After 6 to 9 months of frozen storage, the amount of frost corresponded to the weight of the glazing layer applied before storage.     

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.     

Elucidation of protein aggregation in frozen cod and haddock by transmission electron microscopy/immunocytochemistry,light microscopy and atomic force microscopy

Polyclonal antibodies raised to both native cod myosin and actin as well as to aggregated proteins obtained from frozen cod stored for 11 months at ?10 °C were used to investigate disposition of muscle proteins in frozen cod and haddock fillets by transmission electron microscopy. Specimens from cod and haddock fillets, stored at ?10 °C, treated with anti‐aggregate antibody as the primary antibody, showed significantly more gold particles, especially around the protein aggregates and muscle fibres compared with fish stored at ?30 °C. Samples that were treated with anti‐myosin or anti‐actin antibody showed opposite results. Similar binding properties were observed in ELISA experiments involving the reaction of actin and myosin to both native and aggregate antibodies; thus immunological tests can be used for monitoring aggregate and texture changes in frozen stored fish. In addition, atomic force microscopy images obtained from cod muscle also indicated structural changes in frozen cod muscle proteins. The mica surface was covered with a continuous layer of muscle proteins comprising mainly small globular particles and a few large particles for the control cod sample stored at ?30 °C for 11 months. In contrast, cod fillets stored at ?10 °C showed a thin layer of proteins with small holes and an increased number of large particles denoting aggregates. Formation of ice crystals between the muscle fibres of frozen cod and haddock muscle was monitored without thawing by light microscopy at ?20 °C. The micrographs showed a greater proportion of large ice crystals and extensive protein fibre changes in fillets stored at ?10 °C compared with the control at ?30 °C. Copyright © 2004 Society of Chemical Industry     

Culinary herbs inhibit lipid oxidation in raw and cooked minced meat patties during storage

The effect of dried spices and the ethanol extract of those spices was studied on the stability of fresh chicken minced meat, and fresh and cooked pork patties pretreated with NaCl during refrigerated and frozen storage. The antioxidant activities of the spices were measured by thiobarbituric acid reactive substances (TBARS) and peroxide value (POV) in meat samples. The lipid oxidation was effectively inhibited in the chicken meat treated with several dry spices diminishing the TBARS to a range of 32% and 83% of those found in the control samples in frozen stored meat for 6 months. Marjoram, wild marjoram and caraway were the most effective dry spices. Ethanolic extracts of the same spices were more potent as antioxidants by lowering the concentration of the TBARS to a range of 20–27% of those found in the control samples. Addition of sodium salt to the minced pork resulted very high concentrations of the oxidation products originated from the polyunsaturated fatty acids. The treatment with ethanolic extract of spices (sage, basil, thyme and ginger) significantly inhibited the lipid peroxidation in refrigerated and chilled pork patties pretreated with NaCl by reducing both POV and TBARS. Heat treatment with microwaves produced significantly elevated levels of both lipid peroxides and TBARS, but the amount of these oxidation products was less than 10% in spice‐treated salted meat samples compared to that in untreated ones. Lipid peroxidation also grew continuously during the storage period at −18°C in raw and cooked samples. Ethanolic extracts of spices had a very strong antioxidative effect inhibiting lipid peroxidation in heat‐treated meat products during frozen storage. The highest antioxidant activity was observed in the case of ginger. High correlation coefficients were found between TBARS and POV both in raw and cooked pork patties (0.86, 0.91, respectively) during frozen storage. It is supposed that these compounds originated from the polyunsaturated fatty acids during oxidation processes but at different stages. Utilization of spices, spice mixtures or spice extracts in semi‐prepared meat products intended to be frozen for up to 6 months or more before consumption is proved to be advantageous in regard of shelf life of the food, as well as of human health, because of the beneficial effect of spices in inhibition of lipid peroxidation during heat treatment and chilling storage. © 1999 Society of Chemical Industry     

QUALITY CHANGES OF BLUE CRAB (CALLINECTES SAPIDUS) MEAT DURING FROZEN STORAGE

The aim of the investigation was to determine the quality changes of blue crab (Callinectes sapidus) meat during frozen storage. Blue crabs were obtained directly from fishing boats in the Gulf of Antalya, Turkey and immediately transferred to the laboratory alive. Whole crabs were placed into polyethylene polyamide (PE/PA) pouches, shrunk and stored at ?18C for 10 months. The main changes that take place in blue crabmeat were investigated by means of sensory assessments (odor, appearance), chemical analyses (total volatile bases (TVB‐N), trimethylamine (TMA‐N)) and physical measurements (pH). TVB‐N, TMA‐N values and pH were significantly (P < 0.01) different following frozen storage. Moreover, it was observed that the differences in odor values were significant (P < 0.05), while appearance values were not. All of the measurements indicated that blue crabmeat kept its good quality at ?18C for 10 months.     

Peroxidase and Polyphenoloxidase Activities in Papaya During Postharvest Ripening and After Freezing/Thawing

Changes in peroxidase (POD) and polyphenoloxidase (PPO) activities of papaya (Caricu papava), cv Sunrise, during ripening, freezing and short frozen storage were studied. Fruits were stored at 14°C and 85 90 % RH until maturity for processing was reached (about 21 days). Fruit were frozen cryogenically and frozen slices were stored at — 18°C. POD activity increased in pulp tissue up to the ripe stage, showing a maximum value after 7 days cold storage. Similarly, PPO activity showed an important increase (4 × initial value) on the same date. The quantity of extractable proteins was at a maximum after 15 days storage at 14°C. Freezing and frozen storage (-18°C) produced an increase of POD activity while EPO activity was only slightly affected.     

Effect of lipid oxidation and frozen storage on muscle proteins of Atlantic mackerel (Scomber scombrus)

The effect of storage on the lipids and proteins in Atlantic mackerel stored for up to 24 months at ?20 and ?30 °C was studied. Traditional methods including the peroxide value, thiobarbituric acid‐reactive substances (TBARS) and a reverse phase HPLC method were used to determine the primary and secondary lipid oxidation products. All tests showed an increase in lipid oxidation products with storage time and at a higher storage temperature of ?20 °C compared with samples stored at ?30 °C. Antioxidants had a significant effect (P < 0.01) on the inhibition of lipid oxidation, as shown by the reduction in peroxide value and hydroxides, and malondialdehyde formation. Similarly, deterioration of protein structure and functionality in mackerel stored for 3, 6, 12 and 24 months was greater at ?20 than ?30 °C. ATPase activity in the myosin extract of Atlantic mackerel showed a significant decrease (P < 0.01) with progressive frozen storage. Protein solubility in high salt concentration (0.6 M NaCl) decreased (P < 0.01) during storage at both ?20 and ?30 °C but was greater at ?20 °C. Interestingly, antioxidants BHT, vitamin C and vitamin E protected the proteins against complete loss of ATPase activity and protein solubility to a significant level (P < 0.01) for up to 1 year at ?20 °C compared with samples stored without antioxidants. This study confirms the deleterious effect of lipid oxidation products on protein structure and function in frozen fatty fish. © 2002 Society of Chemical Industry     

Effects of sodium chloride and lactates on chemical and microbiological changes in refrigerated and frozen fresh ground pork

Changes in fat oxidation and color of freshly ground pork, 14% fat, during storage at 2?°C for 15 days and at -20?°C for up to 70 days were determined. The fresh meat was further treated with NaCl (1 and 2%, by weight), sodium or potassium lactate (2%), and combinations of NaCl and lactates. The microbial stability of the refrigerated meat was enhanced by the lactates, and their combinations with NaCl were more effective than lactates alone in delaying the onset of spoilage. Changes in TBARS were seen in the untreated meat only after it was judged spoiled when stored at 2?°C (day 7), and after 69 days at -20?°C. Among treatments, fat stability was highest in lactate-treated meat, and TBARS values were generally similar to those in untreated meat. NaCl enhanced fat oxidation, and the effects of 2% salt were significantly higher than those of 1% (P<0.05). Combinations with lactates reduced the prooxidant effects of NaCl at both storage temperatures, and the effects were more pronounced in meat with 2% NaCl stored at -20?°C. The red color (a* value) was enhanced by NaCl and lactates immediately after their addition to the meat. However, values for all treatments, including the untreated meat, declined rapidly after 4 days at 2?°C, and were 50-70% lower than the initial values after 8 days. Color stability in the frozen meat was highest in control and lactate-treated samples throughout the storage period. It was lowest in samples with 2% NaCl, whether alone or in combination with lactates. Sodium or potassium lactate (2%) enhanced the microbial stability of refrigerated pork without deleterious effects on its color or fat stability. Combinations of lactates with NaCl improved the fat stability, particularly during storage at -20?°C, by reducing the prooxidant activity of NaCl.     

Study of chemical changes in pasteurised orange juice during shelf-life: A fingerprinting-kinetics evaluation of the volatile fraction

The current work used fingerprinting-kinetics for the first time to monitor shelf-life changes in a low-pH, pasteurised, shelf-stable product, more particular in orange juice. Orange juice samples were stored as a function of time at four different storage temperatures (20, 28, 35 and 42 °C). To obtain insight into chemical changes in the volatile food fraction, samples were fingerprinted with headspace GC–MS. The objectives of this work were twofold: (i) to identify major chemical changes of pasteurised orange juice during shelf-life and (ii) to study the kinetics of selected shelf-life compounds in the context of accelerated shelf-life testing (ASLT). At 20 °C, changes in terpenes and a decrease in aldehydes were observed. Oxides and sulphur compounds increased and esters decreased at increased storage temperatures (at 28 °C and above). Concerning ASLT, four volatile compounds had clear temperature and time dependent kinetics within the investigated temperature range.     

Quality characteristics of fresh blue crab meat held at 0 and 4 degrees C in tamper-evident containers.

There has been a regulatory movement toward the required use of tamper-evident containers for fresh blue crab meat. North Carolina passed tamper-evident regulations in 1993. Blue crab processors had little information on possible changes in head-space gases, microbial growth, chemical decomposition, sensory quality, or shelf life caused by the new containers. Chemical, microbiological, physical, and sensory changes in fresh crab meat were monitored during 18 days of storage in ice and 13 days of storage refrigerated at 4 degrees C. "Special" blue crab meat, chosen for the study, is the least expensive commercial form of white crab meat. The crab meat was packaged in four retail containers: copolymer polyethylene cups with polyethylene snap-on lids, copolymer polyethylene cups with snap-on polyethylene lids fastened to the cup with heat-shrink low-density polypropylene seals, copolymer polyethylene cans with aluminum easy-open ends, and copolymer polypropylene cups with a tamper-evident pull-tab on the lid. Control samples packaged in industry standard copolymer polyethylene cups maintained higher oxygen levels than meat stored in tamper-evident containers. No consistent differences in quality or shelf life were detected among the containers. Market shelf life was limited to 6 days for meat held at 4 degrees C and 15 days for meat held at 0 degrees C. Sensory quality deteriorated 6 days earlier for crab meat held at 4 degrees C than meat held at 0 degrees C. Collateral work showed that toxin production by Clostridium botulinum neither occurred following 18 days of storage at 4 degrees C nor after 15 days of storage at 10 degrees C. Definite spoilage occurred before any toxin production. The study suggests that blue crab processors can safely use the new tamper-evident packaging, which has little or no effect on product quality or shelf life. Processors may choose appropriate packaging options using price, packaging quality, market appearance, and ease of production as the deciding criteria.     

Changes in some quality factors of frozen ginger as affected by the freezing storage conditions

The effects of types of ginger root, the freezing storage temperature and time on quality factors associated with color, off‐odor and acceptability of frozen ginger were evaluated to establish the freezing storage conditions of ginger roots. Whole and ground ginger was packed in Nylon/polyethylene (PE) bags and stored at ?5, ?20 and ?40 °C. The quality of the ginger was determined at the following times and storage temperatures: the ginger stored at ?5 °C, ?20 °C, and ?40 °C was sampled at 30‐day intervals for 4 months, at 90‐day intervals for 12 months, and at 120‐day intervals for 16 months, respectively. The content of free sugars, free amino acids (FAAs), unsaturated fatty acids (FUFAs) and volatile compounds noticeably decreased during the storage period, while the total color difference (ΔE) increased, and the temperature effect was significant. The changes in these compounds were generally less in the whole ginger samples. The overall preference of ginger roots stored at ?5, ?20 and ?40 °C was significantly different after 2–3, 9 and 16 months of storage, respectively. The increase of ΔE with decreases of free sugars, FAAs and sensory color indicated the discoloration of frozen ginger was due to the browning reaction. The sensory off‐odor scores were closely associated with the decrease of FUFAs, suggesting that the oxidation of FUFAs caused the development of off‐odor in the frozen ginger. Multiple regression analysis between the overall preference scores and other determined quality factors indicated that FAAs, FUFAs and volatile compounds significantly affected the overall preference scores of ground ginger samples stored at ?5 °C or ?20 °C. The sensory off‐odor and overall preference scores showed that whole ginger could be stored for 2 or 9 months at ?5 or ?20 °C, respectively, maintaining a good overall quality. Copyright © 2006 Society of Chemical Industry     

Rheological and differential scanning calorimetry studies on structural and textural changes in frozen Atlantic mackerel (Scomber scombrus)

The viscoelastic behaviour and thermal stability of Atlantic mackerel fillets stored at ?20 and ?30 °C for up to 2 years were investigated. An increase in elastic (G′) and viscous (G″) modulus values, reflecting protein aggregation, was observed in samples stored at ?20 °C compared with those stored at ?30 °C, as well as with storage time. The results indicate that toughening on frozen storage is not just limited to lean gadoid fish but also occurs in fatty fish, leading to texture deterioration. Differential scanning calorimetry of fillets stored at ?20 °C showed a shift to a lower transition temperature (T_m) and a decrease in enthalpy (ΔH) compared with control fillets stored at ?30 °C; this change was enhanced when fillets were stored for a longer period of time, confirming protein denaturation and the formation of aggregates reported previously by the authors (J Sci Food Agric 82: 579–586 (2002)). The contribution of lipid oxidation to protein aggregation was shown by storing minced mackerel with or without the antioxidant vitamin E at ?10 °C. The G′ and G″ values were higher in samples stored without vitamin E than in samples stored with vitamin E; thus antioxidants may be used to minimise protein aggregation in fatty fish. The role of lipid oxidation in promoting protein aggregation and deterioration in the texture of fatty fish has not been reported hitherto. Antioxidants such as vitamin E may be used not only to prevent lipid oxidation but also to minimise protein damage in order to prolong the shelf‐life of fatty fish. Copyright © 2004 Society of Chemical Industry     

The effect of glaze uptake on storage quality of frozen shrimp

Ice-glazing is applied to protect the frozen shrimp from undesirable quality changes during frozen storage. Effects of initial frozen shrimp temperature on glaze uptake; glazing time on glaze uptake; and different glaze percentage on physical and chemical changes of frozen shrimp during storage were investigated. Shrimps were frozen in a spiral freezing machine (?35 °C/15 min); transferred to the air blast freezer until the core temperature reached ?18 °C, ?25 °C and ?30 °C; submitted to glazing process; and stored at ?18 °C for 180 days. The glazing percentage, pH and N-TVB levels were monitored every 45 days. This study has demonstrated the effectiveness of the glazing process as a protecting agent for frozen shrimp. A reasonable range of water uptake could be between 15% and 20% to guarantee the final quality. Therefore, it is important to prevent temperature fluctuations during transportation and storage to maintain the quality of the frozen shrimps.     

Temperature conditions for the frozen storage of representative marine products in Japan

Abstract

Four representative seafoods in Japan were examined for quality changes during frozen storage up to 1 year, and reasonable temperature conditions for their frozen storage were determined.

Tuna meat was stored at ‐20 ～ ‐80°C for 1 year and its quality changes were followed by using parameters such as the metmyoglobin to total myoglobin ratio, water‐holding capacity, and pH. Ikura, a salted product of salmon eggs, was stored frozen. Quality changes were followed by using the following parameters: toughness of the egg membrane, carotenoid content, and TBA value. Surimi, meat paste from Alaska pollack, was kept frozen, and the quality changes were followed by analyzing protein composition, SDS‐gel electrophoretic and ultracentrifugal patterns, and the gel strength of kamaboko processed therefrom. Finally, prawn was stored frozen. At selected time intervals, the meat was analyzed for changes in water‐holding capacity, pH, tyrosine content, protein composition, and SDS‐gel electrophoretic pattern.

From the present experiments, it was concluded that ‐20°C is low enough for frozen storage to keep the quality unchanged for 2–3 months, irrespective of the types of seafood tested. In frozen storage for 1 year, however, lower temperatures are needed to maintain the quality. Temperatures between ‐30 and ‐40°C seemed to be more reasonable from the viewpoint of energy saving.