National University of Singapore
Food Science & Technology
Effects of Freeze-Thaw Cycles on Prawn Quality
Materials:
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Homogeniser
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Pipettes and tips
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Weighing balance (up to 0.01 g for centrifuge tubes)
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water bath set at 45°C
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Blue cap tubes x 13 at least
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measuring cylinder
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cuvettes
(Top) Demonstration video on effects of freeze that cycles on prawn quality
The objective of this experiment is to investigate the effect of freeze-thaw cycles on the quality of prawns through determining the amount of total soluble proteins as well as the enzyme activity of α-glucosidase.
Aim:
Measurement of α-glucosidase activity:
The enzyme activity of α-glucosidase is determined spectrophotometrically using ρ-nitrophenyl-α-glucopyranoside, PNPG. In the presence of its substrate which is PNPG, a coloured product which is ρ-nitrophenol can be formed through reaction between the enzyme and PNPG. The amount of ρ-nitrophenol can be measured spectrophotometrically at 405 nm using molar extinction of 19,500 M^(-1) cm^(-1).
(Top) Conversion of PNPG to p-nitrophenol in the presence of α-glucosidase