The influence of different cooling techniques (dry ice/ice packs) and storage temperature (-2°C/3°C) to prolong the shelf life of Arctic charr (Salvelinus alpinus) fillets were evaluated by sensory analysis, physical methods, chemical and microbial analysis. The effects of storage temperature were stronger than of different cooling agents. Superchilling (-2°C) of fillets packed with dry ice resulted in 6 days extension of shelf life compared to chilling (3°C). The use of dry ice parallel to superchilling prolonged shelf life for 1 day compared to fillets stored with ice packs. No negative effects on quality of the fillets where detected that could be linked to cell destruction caused by partial freezing or to sour taste, caused by absorption of CO2 gas in fish flesh.
Flokkur: Greinar
Since the early 1990’s, HACCP-based programs are being implemented as a means of preventing food hazards in fish and seafood products. From an engineering perspective, a system designed to control a manufacturing process is expected to result in final product that consistently meet requirements. Although audits are used to verify program implementation, there is a need for some product monitoring to measure the effectiveness and performance of the control systems. This paper discusses the need to monitor final product in seafood HACCP-based programs to measure effectiveness from a systems approach. Information time series of audits and inspections conducted are shown to be more indicative of program performance than snapshot inspections of the final product.
This study aims to evaluate the performances of the membrane processes during the treatment of blue whiting peptide hydrolysates.
Ultrafiltration with high molecular weight cut-off (MWCO) can be used for the separation between peptides and non-hydrolyzed proteins. A membrane of MWCO 20 kDa was tested on hydrolysates containing 11.4 g of peptides per liter of solution. Steady fluxes were satisfactory (100 l/h/m2 at 12 bars and 15 °C) but the nitrogenized matter retention is approximately 30%, which leads to a considerable peptide loss in the permeate.
In addition, ultrafiltration with intermediate MWCO is considered for the enrichment of fractions of peptides of a definite molecular weight range. Two membranes of MWCO 4 and 8 kDa were selected; allowing easy separation between peptides of high and low molecular weight. Moreover, they show variable rejection rates according to classes of molecular weight, which gives hope for a possible fractionation in the range of 1000–7000 Da.
Lastly, the nanofiltration enables the concentration of peptides of low molecular weight by avoiding an excessive concentration of salts. The results with a membrane of MWCO 300 Da are very encouraging because the retention of peptides bigger than 1000 Da is total so that the concentration of the retentate up to about 300 g/l can be reached.
The aim of this work was to evaluate the effects of freezing and frozen storage at –24 °C on the quality of Icelandic herring fillets, focusing on protein solubility and viscosity at pH 2.7 and 11 used for pH-aided protein isolation. The evaluation of quality was based on chemical analyses, protein degradation measurements, and changes in protein solubility and viscosity at pH 2.7 and 11 after up to 6-mo frozen storage of the herring fillets. Lipid oxidation measured as TBARS values increased significantly during the frozen storage (P < 0.05). Protein solubility at pH 2.7 decreased during frozen storage for 6 mo, where the solubility was about 10% lower after 6-mo frozen storage compared to the beginning (P < 0.05). At pH 11, the solubility became approximately 15% lower after 6-mo frozen storage compared to initial solubility (P < 0.05). Viscosity, measured at pH 2.7, increased after 3 mo of frozen storage (P < 0.05). At pH 11, the viscosity increased significantly after 1-wk frozen storage, compared to fresh herring fillets, but did not increase significantly with further storage (P < 0.05). Changes found in solubility and viscosity indicated protein degradation due to freezing and frozen storage. SDS-PAGE analysis did not reveal any protein cross-linking or aggregation formation, either with frozen storage or due to exposure to low pH.
The microbial safety and stability of most food, are based on an application of preservative factors called hurdles. Each hurdle implies putting microorganisms in a hostile environment, which inhibits their growth or causes their death (Leistner, 2000). Some of those hurdles have been empirically used for years to stabilize meat, fish, milk and vegetables. This sometimes leads to completely different product with its own new taste characteristics. Examples of hurdles in marine products are salt (salted cod, klipfish), smoke (cold or hot smoked salmon, herring), acids (marinated products, pickles), temperature (high or low), fermentative microorganisms (traditional Asian sauces) and more recently redox potential (vacuum-packed products). Those preservative factors have been studied for years, but a large amount of potential hurdles for food have already been described including organic acids, bacteriocins, chitosan, nitrate, lactoperoxidase, essential oil, modified atmosphere packaging… , as well as novel decontamination technologies such as microwave and radio frequency, ohmic and inductive heating, high pressure, pulsed electric field, high voltage arc discharge, pulsed light, oscillation magnetic field, ultraviolet light, ultrasound, X-ray, electrolyse NaCl water, ozone… (Kim et al, 1999 ; Weber, 2000 ; Mahmoud et al, 2006). Hurdles that have a positive effect by inhibiting microorganisms may have a negative one on other parameters such as nutritional properties or sensory quality, depending on their intensity. As an example, salt content in food must be high enough to inhibit pathogens and spoilage microorganisms, but not so high to impair taste. In order to lower the preservative level, the hurdle technology concept has been developed (Leistner, 1985), consisting in using combined hurdles to establish an additive antimicrobial effect, and even sometimes a synergetic one, thus improving the safety and the sensory quality of food.
Various studies have shown that two-phase slurry ice is more efficient than ordinary flake ice for chilling fresh fish. In most of the studies only one type of slurry ice has been applied, most often prepared in commercial ice-machines. The objective of this work was to investigate both chilling and maintenance of low temperature utilising flake ice and different kinds of ice slurries, both from commercial ice-machines and also manually prepared by mixing crushed ice and brine. The slurry ice particles are smaller when produced in the ice machines than in the latter method and this small size of the ice particles is widely accepted as one of the predominant factors for rapid cooling of fish. Both saithe and a cylinder made of agar were used as specimen in the experiments. As in other similar studies the cooling rate of all of the different slurry ice types was superior compared to flake ice. Very similar cooling rates were gained using different ice slurries of the same temperature. Therefore, the most important property of the chilling medium was concluded to be temperature since the size of the ice particles seemed to have only minor influence on the cooling rate. The importance of distributing the ice medium evenly when packing fish and ice medium in fish tubs became evident in this work. In order to maintain low temperature during storage, ice slurries are only better than ordinary flake ice for the first few days of storage. After a few days the faster melting of the ice slurries results in inferior cooling capacity so the flake ice, in general, maintains lower temperature in fish through long storage. 1 Introduction Numerous papers showing comparison of chilling of fish with flake ice vs. chilling of fish with two-phase ice slurries have been published. Figure 1 shows the results of an experiment in which a 350 L insulated container was half filled with slurry ice and 30 kg of small to medium sized cod (Davies, 2005). The slurry ice was made of 3 wt. % salt brine with an ice fraction of 35 wt. % and a temperature of-2.6 °C. A second container was packed with cod and flake ice and the temperature evolution in the centre of fish specimen was recorded as in the first container. The performance of the slurry ice is obviously much better. However, the initial temperature of the flake iced fish actually seems to have been higher in the flake iced fish than in the slurry iced fish. More rapid cooling and higher heat transfer rates are explained by larger contact area between the fish and ice particles but also by the fact that the temperature difference between the chilling medium and the fish is larger in the slurry ice case. Similar studies have been done with plaice (Paul, 1998). The fish was cooled in boxes and the results, presented in Figure 2, show that the time required to chill the plaice below 2 °C was more than three times shorter for the slurry ice than for the flake ice. Other similar studies (e.g. Egolf el at., 2005) also show a superior cooling rate of slurry ice compared to flake ice for chilling fish. Figure 1. Cooling of cod using flake ice and slurry ice (Davies, 2005). Figure 2. Cooling of plaice using flake ice and slurry ice (Paul, 1998). Comparison between different slurry ice-and liquid ice types was not found in the literature. Neither has much been published about the cooling capacity of the different ice media. Therefore it was considered useful to include more than one type of slurry ice in the model studies in the present study and not only investigate cooling, but also the maintenance of low temperature during storage.
Bismuth compounds are widely used in industrial processes and products. In medicine, bismuth salts have been applied in combination with antibiotics for the treatment of Helicobacter pylori infections, for the prevention of diarrhea, and in radioimmunotherapy. In the environment, bismuth ions can be biotransformed to the volatile bismuth compound trimethylbismuth (Me3Bi) by methanobacteria. Preliminary in-house studies have indicated that bismuth ions are methylated in the human colon by intestinal microflora following ingestion of bismuth-containing salts. Information concerning cyto- and genotoxicity of these biomethylated products is limited. In the present study, we investigated the cellular uptake of an organic bismuth compound [monomethylbismuth(III), MeBi(III)] and two other bismuth compounds [bismuth citrate (Bi-Cit) and bismuth glutathione (Bi-GS)] in human hepatocytes, lymphocytes, and erythrocytes using ICP-MS. We also analyzed the cyto- and genotoxic effects of these compounds to investigate their toxic potential. Our results show that the methylbismuth compound was better taken up by the cells than Bi-Cit and Bi-GS. All intracellularly detected bismuth compounds were located in the cytosol of the cells. MeBi(III) was best taken up by erythrocytes (36%), followed by lymphocytes (17%) and hepatocytes (0.04%). Erythrocytes and hepatocytes were more susceptible to MeBi(III) exposure than lymphocytes. Cytotoxic effects of MeBi(III) were detectable in erythrocytes at concentrations >4 µM, in hepatocytes at >130 µM, and in lymphocytes at >430 µM after 24 h of exposure. Cytotoxic effects for Bi-Cit and Bi-GS were much lower or not detectable in the used cell lines up to a tested concentration of 500 µM. Exposure of lymphocytes to MeBi(III) (250 µM for 1 h and 25 µM/50 µM for 24 h) resulted in significantly increased frequencies of chromosomal aberrations (CA) and sister chromatid exchanges (SCE), whereas Bi-Cit and Bi-GS induced neither CA nor SCE. Our study also showed an intracellular production of free radicals caused by MeBi(III) in hepatocytes but not in lymphocytes. These data suggest that biomethylation of bismuth ions by the intestinal microflora of the human colon leads to an increase in the toxicity of the primary bismuth salt.
Antioxidative activity of hydrolyzed protein prepared from alkali-solubilized catfish protein isolates was studied. The isolates were hydrolyzed to 5, 15, and 30% degree of hydrolysis using the protease enzyme, Protamex. Hydrolyzed protein was separated into hydrolysates and soluble supernatants, and both of these fractions were studied for their metal chelating ability, 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging ability, ferric reducing antioxidant power (FRAP), oxygen radical absorbance capacity (ORAC), and their ability to inhibit the formation of thiobarbituric acid reactive substances (TBARS) in washed tilapia muscle containing tilapia hemolysate. Both hydrolysates and supernatants were characterized using sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Results showed that DPPH radical scavenging ability and reducing power of catfish protein hydrolysates decreased, whereas the ORAC value, metal chelating ability, and ability to inhibit TBARS increased, with an increase in the degree of hydrolysis. Hydrolysate samples showed higher DPPH radical scavenging ability and Fe3+ reducing ability, and supernatant samples had higher metal chelating ability. In general, low molecular weight (MW) peptides had high ORAC values and high metal chelating ability, and high MW peptides had a higher reducing power (FRAP) and were more effective in scavenging DPPH radicals. In a washed muscle model system, the ability of catfish protein hydrolysates and their corresponding supernatants to inhibit the formation of TBARS increased with an increase in the degree of hydrolysis.