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Discoloration of Coleslaw Is Caused by Chlorophyll Degradation

1996; American Chemical Society; Volume: 44; Issue: 2 Linguagem: Inglês

10.1021/jf9504475

1520-5118

James W. Heaton, Rickey Y. Yada, Alejandro G. Marangoni,

Polyamine Metabolism and Applications

Coleslaw tissue was extracted and analyzed spectrophotometrically for chlorophyll and its derivatives to determine their relationship to tissue discoloration and/or browning at 5 °C under reduced oxygen conditions. A general rapid decrease in chlorophyll a and b was noted after 2−3 days, with a concomitant increase in the amount of pheophytin a and b. The pheophytin was then converted to pheophorbide a and b, which resulted in gray/brown coleslaw after 12−15 days of storage. Polyphenol oxidase activity in cabbage was determined to be very low (81.6 units/g fresh tissue), whereas chlorophyllase activity was very high (23 nmol/min/g fresh tissue). This result suggested that the gray/brown pigments formed were mainly the result of chlorophyll degradation. No change in pH (∼4.6) was observed during storage. A substantial change in the color of the product was, however, observed as analyzed by blue light reflection with an Agtron colorimeter. The pathway for chlorophyll degradation in coleslaw at 5 °C was determined to be chlorophyll → pheophytin → pheophorbide. The rapid conversion of chlorophyll to pheophytin suggests rapid acidic removal of Mg2+ upon addition of dressing, whereas the rather slow conversion of pheophytin to pheophorbide suggests an enzymatic reaction that is possibly mediated by the enzyme chlorophyllase. Keywords: Coleslaw; discoloration; browning; chlorophyll; degradation; chlorophyllase