Improvement of fish freshness determination method by the application of amorphous freeze-dried enzymes.
Alkaline phosphatase (ALP), nucleoside phosphorylase (NP), and xanthine oxidase (XOD) were used in a colorimetric method for evaluation of fish freshness based on the Ki value. Two enzyme mixtures, NP-XOD and ALP-NP-XOD, were prepared with a color developing agent, and stabilities of the enzymes were improved by freeze-drying with glass-forming additives, i.e., sucrose and sucrose-gelatin. As a result, a linear relationship was obtained between the Ki values determined by the developed colorimetric method and a conventional high-performance liquid chromatography with a high correlation coefficient of 0.997. All enzyme samples containing the additive(s) were amorphous, and higher enzymes activities were maintained compared to those freeze-dried without an additive. Sucrose-gelatin/enzyme mixtures showed higher glass transition temperature; consequently, the enzymes were better stabilized than the sucrose/enzyme formulations. Using the sucrose-gelatin/enzyme mixture, Ki values of fish meat could be accurately determined even after 6-month storage of the dried enzymes at 40 °C.
Department of Food Science and Technology.
Paveena
P
Srirangsan
Naoko
N
Hamada-Sato
Kiyoshi
K
Kawai
Manabu
M
Watanabe
Toru
T
Suzuki
D000469:Alkaline Phosphatase / Q000737:chemistry*; D000818:Animals; D003124:Colorimetry / Q000379:methods*; D057075:Enzyme Assays / Q000379:methods*; D004795:Enzyme Stability; D005396:Fish Products / Q000032:analysis*; D029941:Fish Proteins / Q000737:chemistry*; D005399:Fishes; D005612:Freeze Drying; D006358:Hot Temperature; D007700:Kinetics; D010430:Pentosyltransferases / Q000737:chemistry*; D014969:Xanthine Oxidase / Q000737:chemistry*
D029941:Fish Proteins; D014969:Xanthine Oxidase; D010430:Pentosyltransferases; C067995:nucleoside phosphorylase; D000469:Alkaline Phosphatase