Kentucky State University

Poster Title

Effects of Heat Treatment on the Color Stability of Pawpaw Pulp

Institution

Kentucky State University

Abstract

Polyphenol oxidase has been found to be involved in the brown discoloration of pawpaw pulp. Its activity is the greatest at pH 6.5–7.0 and at 5–20o C. Exposure to 40–80o C caused the crude extract of the enzyme to lose its enzyme activity rapidly. The objective of this study was to determine whether brief heat treatment could prevent discoloration of pawpaw pulp. Pawpaw fruits were harvested from the research farm of Kentucky State University in the fall of 2006. Freshly prepared pulp homogenate consisting of about 10 fruits was divided into 16 individual, equal-sized portions, placed in vacuum packed plastic bags. The bags were heated by being placed in boiling water for 0, 1, 3 or 5 minutes. Immediately after heating, they were cooled in ice cold water. The pulp was removed from each of the bags and placed evenly in a flat plastic container covered with plastic film. Air was allowed into the container through holes on the film. The color of the pulp in the containers was measured with a colorimeter at 0, 1, 2, 10 and 20 hours after the end of the heat treatment. With no heat treatment, the pulp changed color rapidly, turning completely brown by 10 hours. Heating for 1 or 3 minutes slowed down the color change but heating for 5 minutes essentially prevented significant color changes in the pulp. Our results indicate that a brief heat treatment can be used to prevent discoloration of pawpaw pulp.

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Effects of Heat Treatment on the Color Stability of Pawpaw Pulp

Polyphenol oxidase has been found to be involved in the brown discoloration of pawpaw pulp. Its activity is the greatest at pH 6.5–7.0 and at 5–20o C. Exposure to 40–80o C caused the crude extract of the enzyme to lose its enzyme activity rapidly. The objective of this study was to determine whether brief heat treatment could prevent discoloration of pawpaw pulp. Pawpaw fruits were harvested from the research farm of Kentucky State University in the fall of 2006. Freshly prepared pulp homogenate consisting of about 10 fruits was divided into 16 individual, equal-sized portions, placed in vacuum packed plastic bags. The bags were heated by being placed in boiling water for 0, 1, 3 or 5 minutes. Immediately after heating, they were cooled in ice cold water. The pulp was removed from each of the bags and placed evenly in a flat plastic container covered with plastic film. Air was allowed into the container through holes on the film. The color of the pulp in the containers was measured with a colorimeter at 0, 1, 2, 10 and 20 hours after the end of the heat treatment. With no heat treatment, the pulp changed color rapidly, turning completely brown by 10 hours. Heating for 1 or 3 minutes slowed down the color change but heating for 5 minutes essentially prevented significant color changes in the pulp. Our results indicate that a brief heat treatment can be used to prevent discoloration of pawpaw pulp.