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The formation of biogenic amines in flesh of selected fish species
MATĚJKOVÁ, Kateřina
The thesis deals with the use and effectiveness of some less common methods of conservation of fish meat. The formation of biogenic amines in meat is observed in connection with the non-traditional preservative methods. Amines can serve as indicators of protein degradation. The quality of fish was considered in connection with the increasing content of selected biogenic amines (putrescine, cadaverine, spermidine, spermine, 2-fenylathylamine, histamine, tyramine and tryptamine). Ultra performance liquid chromatography (UPLC) was used as the method for determination of biogenic amines. Amines were derivatized by dansylchloride before their UPLC separation. The fish flesh was vacuum-packed. Samples were stored for several weeks in a thermostat at the selected storage temperature after the application of selected preservative technique. Beta-irradiation and high hydrostatic pressure were used for the preservation of fish flesh. Control samples were not exposed to the â-irradiation and high pressure. The organoleptic properties were studied for all samples (smell/odor, insight and shape). Beta-irradiation was applied to fish meat of common carp (Cyprinus carpio) and rainbow trout (Oncorhynchus mykiss). Both these species of freshwater fish are economically significant. Carp and trout are the species being mostly consumed in the Czech Republic. Fish meat is considered to be provided the flesh is fresh. A testing series of samples was created with common carp to determine the appropriate dose of â-irradiation. The maximum permissible dose of irradiation for fish meat is 3 kGy. Fish samples were exposed this dose in the first experiment. The dose of irradiation was reduced in following experiments based on the experience from the initial experiment. The doses of 0.25, 0.5, 0.75, 1.0 and 2.0 kGy were applied to rainbow trout. The value of 0.75 kGy of â-irradiation or higher (1.0, 2.0 and 3.0 kGy) prolonged the shelf life of fish meat, which was stored for three months (98 days). Prolonging of the shelf life of fish meat to approximately 98 days at 3.5 °C is redundant from technical point of view. For that reason lower doses 0.25, 0.5 and 0.75 kGy were tested in more detail in the repeated experiment with carp meat. Lower doses of â-irradiation are considered to be more acceptable and-at the same time-sufficiently effective for delaying the beginning of degradation processes. 6 High hydrostatic pressure was applied to meat of common carp (Cyprinus carpio), rainbow trout (Oncorhynchus mykiss) and pike (Exos lucius). Pike is another very popular kind of freshwater fish. Pike flesh is very tasty, but in spite of this, pike is not so much popular among consumers compared to carp and trout. The cause is its high price. Samples of pike were stored at standard temperature 3.5 °C and also at higher temperature 12 °C (unlike experiments with â-irradiation). Lower temperature of storage (3.5 °C) followed the conditions of storing of fish meat in industrial refrigeration facilities and households. The high pressure might not be sufficient for preservation at higher storage temperatures. This assumption was based on available information. Samples were treated by high pressure and stored at both 3.5 °C and 12 °C to verify this assumption. Higher temperature simulated either failure of refrigeration equipment or unsuitable store temperature of meat. In all species selected freshwater fish two levels of high pressure were applied ? 300 and 500 MPa. Both levels had significantly reduced the formation of biogenic amines, especially in samples stored at 3.5 °C. At this temperature, the effect of 300 and 500 MPa delayed start of degradation processes in fish meat by 3?4 weeks. At 12 °C and 500 MPa, high pressure extended the sustainability of meat by no more than one week. 500 MPa is effective treatment at the lower temperature of 3.5 °C. High pressure is not reliable preservative techniques at higher temperature.
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The Demembranation as a Tool to Study a Movement and Physiology of Activation of Fish Spermatozoa
BLAŽKOVÁ, Jaroslava
The aim of the thesis was the summarization of information about the demembranation method as a means of study of the physiology of activation and motility of fish spermatozoa. A simple demonstration of the method is also presented. The demembranation of fish sperm is a method, in which cytoplasmic membrane (the phospholipid bilayer, which separate intercellular and extracellular environments) is destroyed. A mild non-ionic detergent, TrintonX-100, was used in the study. Common carp (Cyprinus carpio) as a representative member of Teleost fish and sterlet as a member of Chondrostean (elasmobranch) fish were studied in the thesis.
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Damages caused by predation of invertebrates on the earliest development stages of fish
LOŽEK, Filip
Cílem bakalářské práce bude zjistit do jaké míry je přítomnost bezobratlých predátorů pro raná stádia ryb nebezpečná a má vliv na míru jejich přežívání. Většina hospodářsky chovaných druhů ryb se do rybníků nasazuje ve stádiu váčkového plůdku a nedochází k předchozímu rozkrmování na vacích či jiných odchovných zařízeních s pozdějším vysazením již silnějšího rozkrmeného plůdku. V prvních dnech po nasazení dochází také k největším ztrátám, které mohou být způsobeny ať už nedostatečnou potravní nabídkou nebo zejména predací bezobratlými predátory. Mezi ně mohou patřit tzv. "dravé" buchanky, larvy vážek nebo vodních brouků, a i některé druhy vodních ploštic. Student v průběhu bakalářské práce uskuteční několik laboratorních pokusů na rozplavaném plůdku kaprovitých, případně i okounovitých ryb, které bude konfrontovat s dravci, tedy dravými larvami hmyzu, vodními plošticemi či buchankami. Na základě pokusů vyhodnotí potenciální nebezpečnost jednotlivých dravců vzhledem k plůdku ryb.
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Monitoring of gains in weight of Caps fed with cereals in the pond of Fishery Chlum u Třeboně
CEPÁK, Miloš
Pond management in the Czech Republic uses semi-intensive methods to produce market carp in fishing ponds. Natural food complemented with cereals play an important role in this economical and environment-friendly method of fish breeding. The system makes it possible to increase weight gains of carps in comparison with natural production. At this level of production the market carp maintains high quality meat and therefore it is highly valued also on markets abroad. Every year approximately one half of the market carp production is exported from the Czech Republic and the rest is sold in this country. The purpose of my work is to assess the existing technology of additional feeding of market carp in Fishery Chlum u Třeboně, where I have monitored the stock, spring and , losses, individual weights, weight increases, used feed and feed coefficients. I have also cooperated on monitoring of pilot plant tests in the system of Humlenské ponds where the carps were fed with various cereals
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Utilization of cereals on suplementary carp feeding on Ponds Fishery Lomnice nad Lužnicí
EISERT, Zdeněk
Theme of my Diploma work refers about possibility of feeding up the common carp with the cereal food in the ponds. Research was monitor on 4 ponds in Naděje ponds system. The ponds have 2,4 ha together. Three of them were used for research and fourth pond was for control. This control pound had only a natural food. During the research was every year plant into the ponds 363 carps type (K 3) for 1 ha and after fish out was this sort K 4. For the research were very pilot fish outs. Fish out carp were for weight, length of the body and perimeter of the body monitoring. This data was use for a statistics evaluation. Feeding run 3 days in a week (Monday, Wednesday, Friday) in a day ration 2 % of the fish weight in a pound.
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