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Keywords:

  • enzyme inactivation;
  • lipoxygenase;
  • nonthermal;
  • pulsed ultraviolet (PUV);
  • sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE)

Abstract

This study investigated pulsed ultraviolet (PUV) illumination at different distances from the PUV source on soybean lipoxygenase (LOX) (0.4 mg/mL in 0.01 M Tris-HCl buffer, pH 9) activity. Samples (5 mL) were illuminated for 1, 2, 4, 8, and 16 s at 3 distances 6, 8.5, and 11 cm from the PUV lamp's quartz window. The temperature of 33.5 ± 1.8°C was observed for the highest treatment time of 16 s at the shortest distance of 6 cm, and resulted in a 3.5 log reduction (99.95%) in initial LOX activity. Illumination time and distance from the lamp significantly (P ≤ 0.05) affected LOX inactivation. Sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) was performed on treated LOX samples and further protein profile for treated LOX filtrate (≤10 kDa), was analyzed by reverse phase high-performance liquid chromatography (RP-HPLC). The protein profile analysis revealed that LOX protein degradation was influenced significantly (P ≤ 0.05) by PUV illumination time.

Practical Application

An investigation of pulsed ultraviolet light (PUV) on lipoxygenase (LOX) activity was performed for its application and enhancement of the current literature. This study shows that PUV illumination inactivates LOX, an enzyme responsible for stimulating off-flavor generation, loss of pigments and oxidative destruction of essential fatty acids in food products and raw materials. The sample treatment distance from the quartz window and illumination time were major parameters influencing the enzyme activity. The overall inactivation of LOX under PUV was accounted by the enzyme protein fragmentation with out considerable rise in the temperature of the sample. This shows PUV can successfully act as a nonthermal process for inactivation of LOX enzymes.