DISCOLORATION OF COLESLAW IS CAUSED BY CHLOROPHYLL DEGRADATION

Coleslaw tissue was extracted and analyzed spectrophotometrically for chlorophyll and its derivatives to determine their relationship to tis sue discoloration and/or browning at 5 degrees 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 pheophyti n 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. Pol yphenol 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/bro wn pigments formed were mainly the result of chlorophyll degradation. No change in pH (similar to 4.6) was observed during storage. A substa ntial change in the color of the product was, however, observed as ana lyzed by blue light reflection with an Agtron colorimeter. The pathway for chlorophyll degradation in coleslaw at 5 degrees C was determined to be chlorophyll --> pheophytin --> pheophorbide. The rapid conversi on of chlorophyll to pheophytin suggests rapid acidic removal of Mg2upon addition of dressing, whereas the rather slow conversion of pheop hytin to pheophorbide suggests an enzymatic reaction that is possibly mediated by the enzyme chlorophyllase.