CHARACTERIZATION OF POLYPHENOL OXIDASE FROM ROOSTER POTATO (SOLANUM TUBEROSUM CV ROOSTER)

The isolation and purification of polyphenol oxidase from potatoes ( Solanum tuberosum cv. Rooster) is described. A 64-fold purified preparation has been obtained with 10% yield by a procedure involving (NH₄)₂SO₄ precipitation, phenyl sepharose chromatography, ion exchange chromatography and hydroxyapatite chromatography. The partially purified enzyme has both cresolase and catecholase activity. Activity was lower toward monophenols than diphenols. Enzyme activity was optimal at pH 6.0–6.5 and at 30C. Greater than 50% activity was retained during storage for 72 h at pH 6.0–7.5. Residual activity was greater than 50% after incubation at 20C for 72 h, 30C for 48 h, 40C for 24 h, 50C for 2 h and 60C for 15 min. The most effective inhibitors tested were sodium metabisulfite and ascorbic acid. Sodium dodecyl sulphate appeared to activate the enzyme. The enzyme was capable of cross-linking casein but did not increase gel-strengths in acidified milk gels.

PRACTICAL APPLICATIONS

Rooster is the most important potato cultivar grown in Ireland and data on its isolation and characterization has not been reported previously. This work describes a method to isolate polyphenol oxidase and characterization of the enzyme. Information on characterization of the enzyme could be valuable in relation to control of enzymatic browning during current processing and in minimum processing. There is potential for use of the enzyme in the emerging cross-linking area, as the results show some success and there may be potential of more cross-linking as the field develops and as interest in natural methods of cross-linking for food texture grows. This could lead to an important use for potato waste. Food product applications are given.