Hypoxanthine Ratio Determination in Fish Extract Using Capillary Electrophoresis and Immobilized Enzymes

Abstract

Fish freshness was assessed using capillary electrophoresis and an immobilized enzyme procedure to monitor degradation of inosine-Smonophosphate (IMP), inosine (HxR) and hypoxanthine (I-Ix). The enzymatic method used an amperometric probe at + 0.7 V (platinum vs silver/silver chloride) with immobilized xanthine oxidase, catalase, nucleoside phosphorylase, and nucleotidase for converting I-Ix, HxR or IMP to uric acid. Capillary electrophoresis resolved IMP, inosine and Hx by migration rates resulting from an applied electric field (416 V/cm, 50 p,A). Components were detected at 250 nm. The H ratio of Hx/[IMP + HxR + Hx] and simplified K value of [HxR + Hx]/ [IMP + HxR + I-Ix] were determined in cod, salmon and trout stored on ice (WC) and at 20°C. The two procedures agreed and for all species H ratio and K values increased with storage time.

Chemical Quality Indices for Freshness Evaluation of Fish

“…Luong et al (1992) highlight that, for some species, K and Ki values do not adequately reflect the alterations that occur, because they rapidly increase and then, they remain more or less constant. This is caused by a rapid accumulation of HxR and Hx.…”

“…Many methods have been reported for the analysis of ATP and its degradation products, such as the use of cationic-ionic exchange columns (Saito et al 1959), enzyme sensor system (Karube et al 1984), capillary electrophoresis (Luong et al, 1992) and high performance liquid chromatography (HPLC), the latter as the most frequently described in several studies (Burns et al, 1985;Lakshmanan et al, 1996;Vázquez-Ortiz et al, 1996;Özogul et al, 2000;Huidobro et al, 2001;Özogul et al, 2008;Siripatrawan et al, 2009;Uriarte-Montoya et al, 2010;Özogul et al, 2011). Perchloric acid is the reagent more frequently used in the extraction stage.…”

Microchip capillary electrophoresis with a boron-doped diamond electrode for rapid separation and detection of purines

“…Hypoxanthine, xanthine, and uric acid are metabolites of purine bases in nucleic acids through a series of biochemical pathways [2]. In addition, hypoxanthine and xanthine have been linked to off-flavors in food and are important markers of fish freshness [3,4]. The concentration of uric acid is an important diagnostic parameter in the evaluation of renal diseases [2].…”

Quality assessment of rainbow trout (Oncorhynchus mykiss) fillets during super chilling and chilled storage

“…Since adenosine nucleotides disappear very quickly, Karube et al (1984) proposed the Ki value, which excludes ATP, ADP and AMP, as an index of freshness quality. H values have been described by Luong et al (1992) as an index of freshness quality. Additionally, the G and P values are reported to be most useful with lean fish.…”