Submitted to: Journal Acta Horticulturae
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/1/1997
Publication Date: N/A
Citation: Interpretive Summary: Fresh-cut fruits and vegetables are packed in film bags and the oxygen supply within the bag can be depleted to a dangerously low level by respiration. When the oxygen drops below a specific level, called the extinction point, aerobic respiration cannot proceed and anaerobic respiration becomes the dominate pathway. This is not desirable because the product begins to ferment and deteriorate when anaerobic pathway is dominant. However, we found carrot shreds to be satisfactory when stored in low oxygen atmosphere below the extinction point. Research was undertaken to better understand why the carrot shreds or any other fresh-cut product can survive at slightly below the extinction point. Results indicated that the anaerobic pathway was induced to proceed at a more rapid rate. Typically, anaerobic respiration does not produce sufficient chemical energy to sustain metabolism. However, when anaerobic respiration rate proceeded at a faster rate, a sufficient amount of chemical energy was produced to sustain minimum metabolism. This fundamental information on how the carrot shreds survived in oxygen atmosphere slightly below the extinction point will be helpful in identifying the minimum oxygen level acceptable in film bags for other fresh-cut products.
Technical Abstract: The RQ breakpoint of carrot shreds occurred at about 1 percent O2. At slightly below the RQ breakpoint, 0.5 percent O2, glycolysis was affected. The low O2 atmosphere caused a sharp increase in fructose 1,6-bisphosphate (Fru-1,6-P2) and a slight decrease in fructose 6-phosphate (Fru-6-P), phosphoenolpyruvate, and pyruvate among the glycolytic intermediate. The low O2 also caused an increase in fructose 2,6-bisphosphate (Fru-2.6-P2) and ethanol. Fru-2,6-P2 appeared to have promoted glycolysis, as noted by the increased activity of phosphate-dependent fructokinase. ATP level decreased under low O2, but a sufficient level is thought to have been maintained for minimum metabolism by the increased glycolytic activity.