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Djagal W Marseno
Gadjah Mada University
Agriculture, Biological Sciences & Forestry

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Detection of Fish Freshness Using Immobilized ADP-ase and 5'-Nucleotidase on Polyacrylamide Gel Djagal W Marseno; Retno Indrati; Sudarmanto Sudarmanto
Indonesian Food and Nutrition Progress Vol 5, No 1 (1998)
Publisher : Indonesian Association of Food Technologists

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.22146/jifnp.54

Abstract

The presence of ADP and IMP in the muscle of fish could be used as an indicator of its freshness. These metabolites could be detected enzymaticaly using ADPase and 51-nucleotidase. The aim of this research was to determine the presence of ADP and IMP in the muscle of fish qualitatively, using immobilized ADPase and 5'-nucleotidase on polyacrylamide gel. The results showed that in the non-immobilized form, ADPase has an optimum pH of 6 and stable at pH 5.5-10, while 5'-nucleotidase has two optima pH of 6.5 and 9 and it was stable at pH 7-10. Optimum temperature of ADPase and 5'-nucleotidase was 45 and 50°C, respectively. In the immobilized form, the activity of ADPase was optimum at pH 6 and it was still stable at pH 5.5 - 7.0 after storage at -20°Cfor 90 days, while 5'-nucleotidase was still stable at pH Z5-10 after storage at -20°C for 90 days. Both enzymes were more stable in frozen storage than that of chilled storage. Sensitivity of both enzymes to detect the fish freshness during storage was affected by the presence of free inorganic phosphate derived from other phosphate-containing metabolites.
Utilization of ATP and Its Derivatives as an Index of Freshness of Nila (Oreochromis niloticus) During Storage Djagal W Marseno; Sudarmanto Sudarmanto; Retno Indrati
Indonesian Food and Nutrition Progress Vol 6, No 1 (1999)
Publisher : Indonesian Association of Food Technologists

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.22146/jifnp.75

Abstract

The role of a reliable and reproducible, index of fish freshness, is important. The objective of this research was to examine the utilisation of ATP and its derivatives (expressed as K-value) as an index offish freshness using Nila (Oreochromis niloticus) as a model of study. K-value is [(Inosine + Hypoxanthine) / (ATP + ADP + AMP + IMP + Inosine + Hypoxanthine)] x 100%. Live fish were killed, packed individually using polyethylene bag and stored at 4 and 28°C. At defined time, some fishes were examined their ATP and its breakdown products using a reverse phase HPLC system. The results showed that ATP, ADP and AMP were degraded rapidly and disappeared within 12 ho urs. Degradation of IMP in the samples stored at 4°C was slower than those of samples stored at 28°C. Interestingly, the accumulation of Inosine occurs only in the samples stored at 28°C while the accumulation of Hypoxanthine occurs only in the samples stored at 4"C. The data suggested that the activity of IMP-degrading enzyme (5'-nucleotidase) at 4"C was higher than that of Inosine-degrading enzyme, but at 28°C both enzymes have similar activities. Linear regression analysis between K-value and storage time showed that increasing rate of K-value or rate of the lowering freshness of samples stored at 28"C was 4 times higher than that of samples stored at 4°C. Limits offish acceptability (K-value 60%) of Nila stored at 28 and 4"C were reached at 12 and 72 hours, respectively. The results confirmed that K-value was the best as an index offish freshness compared with IMP, Inosine and Hypoxanthine and it could be used as an index of freshness of Nila (Oreochromis niloticus) during storage.
Immobilization of Lipase from Rhizopus delemar on Polyethylene Membrane Retno Indrati; Djagal W Marseno; Yoshiyuki Ohta
Indonesian Food and Nutrition Progress Vol 6, No 1 (1999)
Publisher : Indonesian Association of Food Technologists

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.22146/jifnp.67

Abstract

Rhizopus delemar lipase was immobilized by physical adsorption onto polyethylene membranes. The influence of membrane pore size and thickness on enzyme activity was studied. The immobilization efficiency was higher for the thicker membrane than thin one, this related to the large excess of area that the enzyme can occupy. The immobilization efficiency was also affected by enzyme loading, in which suppression was occurred at high enzyme loading. At the initial rate of hydrolysis reaction, the amount of enzyme bound, concentration of substrate, and membrane's thickness as related to the limitation of the substrate transfer affected the production of fatty acid. The thin polyethylene membrane was the best support since the enzyme immobilized on this support was stable during storage and possessed higher degree of hydrolysis and ability for subsequent reuses. Both membranes were regenerable by washing for fresh enzyme immobilization.
Co-Authors Retno Indrati Sudarmanto Sudarmanto Yoshiyuki Ohta