CHANNEL CATFISH INDUSTRY IN THE USA AND THE OFF-FLAVOR PROBLEM

Abstract

Prikazani su povijest i razvoj tehnologije gojidbe kanalnog soma u ribnjacima te statistički podaci o proizvodnji, doradi i vrijednosti proizvoda u tijeku posljednjih 15 godina. Povećanje potrošnje u pučanstvu te sadašnje niske cijenež žitarica i soje povoljni su čimbenici za daljnje povećanje proizvodnje. Stalan razvoj industrije potiče nekoliko čimbenika: pionirski napori uzgajivača, istraživanja na sveučilištima i u državnim istraživačkim centrima od kojih neki imaju brojne pokusne ribnjake, rad kooperativne savjetodavne službe za ribnjačare, aktivnost udruga uzgajivača soma, suvremeni marketing, visoku kvalitetu proizvoda dorade i vertikalno povezivanje industrije. Neprikladna okusno-mirisna kakvoća soma uzrokovana metabolitima algi jedna je od glavnih poteškoća u industriji. Spomenuti su najvažniji rodovi algi koje proizvode takve metabolite, pojave mirisno-okusne neprikladnosti u drugih riba i u akumulacijama za pitku vodu, te sadašnji sustav sprečavanja dolaska kontaminirane ribe na tržište. Od nepoželjnih metabolita algi najvažniji su hlapljivi alkoholi geosmin i 2-methylisorborneol (MIB). Naglašena je potreba jeftinijih i bržih metoda određivanja tih metabolita. Istraživanja na Sveučilištu Arkansas u Pine Bluffu, SAD, o kontroliranju nepoželjnih vrsta algi u pokusnim ribnjacima s pomoću bijelog glavaša (Hypophthalmichthys molitrix Val.) i tilapija u kavezima pokazala su da taj pristup obećava uspješnost.The history, the production technology in channel catfish pond farming industry as well as the statistical data on production, processing and product value during past 15 years are presented. The trend of increasing consumption by the population and the presently low prices of grain and soybeans are conductive to further expansion of production. The steady growth of the industry is stimulated by several factors: innovative efforts by farmers, research at the universities and at government institutions some of which have numerous experimental ponds, cooperative extension service for farmers, modern marketing, activities of catfish farming associations, high quality of products from processing plants and vertical integration. The off-flavor in catfish caused by algal metabolites is a major problem in the industry. Genera of algae producing such metabolites, their accumulation in other fish and occurrence in drinking water reservoirs as well as the current emphasis on preventing the entrance of off-flavor contaminated catfish onto the market were reviewed. The main undesirable algal metyabolites are volatile alcohols geosmin and 2-methylisoborneol (MIB). The need for less expensive and quick methods of identifying major off-flavor compounds was pointed out. Research at the University of Arkansas at Pine Bluff, USA, on control of off-flavor algae in experimental ponds by filter-feeding silver carp (Hypophthalmichthys molitrix Val.) and tilapias confined in cages showed this approach to be rather promising

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