Qualitätsvergleich zwischen maschinen- und handgeschälten Nordseegarnelen

After the evaluation of 48 samples consisting of hand and machine-peeled sand shrimps it can be stated that there was no significant difference in quality between both. The quality of the sand shrimps was evaluated by sensorially performed paired comparison as well as by estimating the microbial load and the volatile amines (MMA, DMA, TMA). Additionally, the colour characteristics were measured instrumentally. To characterise the influence of the technological regime measurements of pH and of the salt content were performed. The quality of sand shrimp is further influenced by technological steps as freezing, cooking procedure and preservatives used. From the hygienic point of view the machine-peeling was without any objections. The microbial load was small and below the limit set by EC. Measurement of volatile amines was not suited to make visible difference created be the various peeling methods.

Relation between TMAOase activity and content of formaldehyde in fillet minces and bellyflap minces from gadoid fishes

Minced fish is a significant component of a number of frozen fishery products like fish fingers, cakes and patties. Predominately minced fish is produced from gadoid species (Alaska pollack, cod, saithe, hake and others) possessing the enzyme trimethylamine oxide demethylase (TMAOase, E.C. 4.1.2.32) (Rehbein and Schreiber 1984). TMAOase catalyses the degradation of trimethylamine oxide (TMAO) to formaldehyde (FA) and dimethylamine (DMA), preferentially during frozen storage of products (Hultin 1992). In most gadoid species light muscle contains only low activity of TMAOase, the activity of red muscle and bellyflaps being somewhat higher. In contrast, the TMAOase activity in blood, kidney and other tissues, residues of which may contaminate minced fish flesh, may be higher for several orders of magnitude (Rehbein and Schreiber 1984).

Anwendungsmöglichkeiten instrumenteller Texturanalyse zur Charakterisierung industriell hergestellter Farcen

Commercially processed and for industrial purpose destined minces of several fish species were characterised with regard to their texture using texture profile analysis (TPA) of boiled specimen and by measuring the penetration force on raw minces as well as with regard to their colour by instrumental measurements of CIELab values. Concerning the parameters investigated the minces were in most cases significantly different. It was evident that the fish species is responsible for the functional properties of these intermediate products. For the TPA the influence of the measurement conditions was demonstrated and an appropriate method derived. IEF of proteins was used to verify the declared fish species. Unfortunately, this was not possible in all cases due to the lack of comparable pattern. Both the DMA and FA content were found to be in the normal range except those for saithe.

Variation der Gehalte an flüchtigen stickstoffhaltigen Basen und "TVB-N" in Rotbarsch

Die Gehalte an den flüchtigen stickstoffhaltigen Aminen, Amoniak, Dimethylamin (DMA), Trimethylamin (TMA) sowie Trimethylaminoxid (TMAO) und der durch Direktdestillation nach milder Alkalisierung mit Magnesiumoxid erhaltende Wert an sogenanntem flüchtigen Basenstickstoff (TVB-N) wurden an fangfrischen Exemplaren von Rotbarsch untersucht.

Cryopreservation of sperm of common carp, Cyprinus carpio and silver barb, Barbonymus gonionotus for genetically improved seed production

Experiments were conducted to develop and standardize the protocols for cryopreservation of sperm of common carp, Cyprinus carpio and also for using the cryopreserved sperm for fertilization of eggs. Nine extender solutions as Alsever's solution, kurokura-1, kurokura-2, urea egg-yolk, egg-yolk citrate, 0.6% glucose, 0.9% NaCl, Ma and Mb, and five cryoprotectants namely ethanol, methanol, dimethylsulfoxide (DMSO), dimethylamine (DMA) and glycerol were tested. The cryoprotectants were mixed at 10% concentration of the extenders (v/v) to make the cryodiluents. Milt and cryodiluents were mixed at a ratio of 1:9 for Alsever's solution, kurokura-1, kurokura-2, 0.6% glucose and 0.9% NaCl, 1:4 for urea egg-yolk, egg-yolk citrate, Ma and Mb. Among the cryodiluents Alsever's solution mixed with either ethanol or methanol was found to be suitable and it produced more than 90% and 80% spermatozoan motility at equilibrium and post-thaw periods, respectively. Kurokura-1 and kurokura-2 when mixed with the same cryoprotectants showed good spermatozoan motility at equilibrium period (80-90%) but the motility was reduced (30-55%) at post-thaw state. Other extenders did not produce acceptable sperm-motility and in some cases the frozen milt became clotted. Different dilution ratios (1:1, 1:2, 1:4, 1:5, 1:7, 1:9, 1:12, 1:15, 1:20) were formulated for obtaining a suitable milt dilution, the dilution ratio of 1: 9 (milt : cryodiluent) demonstrated the highest post-thaw spermatozoan motility (80%) in Alserver's solution. The optimum concentration of cryoprotectants in the cryodiluents was determined, 10% concentration level was found to be effective to produce the highest number of spermatozoan motility in comparison to the other concentrations (5%, 15%, 20% 30%). Sperm preserved with the cryodiluent Alsever's solution along with either methanol or ethanol was found to be effective to fertilize eggs and produce hatchlings. The hatching rates ranged between 1.48% and 14.76%, compare to control. The fish produced through use of cryopreserved sperm and normal sperm were found to grow well and no significant (P<0.05) growth difference was observed between them. In case of silver barb, Barbonymus gonionotus, sperm tested against six extenders such as egg-yolk citrate, urea-egg-yolk, kurokura-1, kurokura-2, 0.9% NaCl and modified fish ringer (MFR) solution. Cryoprotectants used were the same as those of C. carpio. Milt was diluted with the cryodiluent at a ratio of 1:4 for egg-yolk citrate and urea-egg-yolk, 1:5 for kurokura-1 and 1:9 for 0.9% NaCl, MFR and kurokura-2. The cryoprotectant concentration was maintained at 10% of the extender (v/v) in all the cases. Among the extenders, egg-yolk citrate and urea-egg-yolk mixed with 10% DMSO, methanol and ethanol produced 50% post-thaw spermatozoan motility, whereas DMA and glycerol provided only 10% motility. Trials on milt dilution ratio and cryoprotectant concentration are being conducted. Fertilization trials are also underway.