Effects of mild heat treatment on microbial growth and product quality of packaged fresh-cut table grapes.

The changes in packaged fresh-cut grape quality and microbial growth as affected by mild heat treatments and the retention of grape cap stems during 5 degrees C storage were evaluated. Each individual grape was either manually pulled off (stemless) from the stems, or cut (cut stem) to allow for a 1- to 2-mm cap stem remaining on the berry. The samples were sanitized in 100 mg/L chlorine solution for 1 min, followed by a mild heat treatment in a water bath (45 degrees C, 8 min) or an oven (55 degrees C, 5 min). After cooling, the berries were packaged in rigid trays sealed with a gas permeable film and stored at 5 degrees C. Product quality and decay rate were evaluated periodically during storage. The results indicate that in the package headspace for hot water treatment of stemless grapes, partial pressures of O(2) declined significantly (P < 0.05) less and C(2)H(4) increased significantly (P < 0.001) less than for the control and hot air treatment. Stem removal and heat treatment had significant (P < 0.05) effects on the decay rate of grapes during storage. Hot water treatment maintained a significantly lower decay rate than the control and hot air treatment throughout the entire storage. Color and texture were not significantly (P > 0.05) affected by either heat treatment or stem removal. Grapes that retained the cap stems and received hot water treatment had the lowest decay rate and lowest microbial growth with the absence of any negative impact on grape color, texture, and flavor.