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Title: Hot water treatment in combination with rachis removal and modified atmosphere packaging maintains quality of table grapes

item Luo, Yaguang - Sunny
item DING, W - Northwest Agricultural & Forestry University
item Conway, William

Submitted to: HortScience
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/8/2009
Publication Date: 12/5/2009
Citation: Kou, L., Luo, Y., Ding, W., Liu, X., Conway, W.S. 2009. Hot water treatment in combination with rachis removal and modified atmosphere packaging maintains quality of table grapes. HortScience. 44:1947-1952.

Interpretive Summary: Fresh grapes are often treated with chemical sulfur dioxide to control decay developed during storage and transportation. However, sulfur dioxide treatment leaves chemical residues that pose a health risk for allergic individuals and this application is not suitable for organic grapes. In this research, we developed an alternative to sulfur dioxide treatment to control decay on grapes. We demonstrated that a combination of warm water treatment with stem removal and appropriate modified atmosphere packaging significantly reduced microbial growth and decay development while maintaining grape color, texture, and flavor. This information is important to the grape industry, especially the organic grape growers, to control decay and maintain fruit quality.

Technical Abstract: Decay and rachis browning are major problems that limit the shelf life of fresh table grapes (Vitis vinifera cv. Crismons seedless) and are often controlled by the application of sulfur dioxide (SO2) to maintain quality. However, sulfite residues pose a health risk for allergic individuals and SO2 applications have consequently been restricted in many countries. The main objective of this study was to evaluate the use of mild heat treatment, rachis removal, sanitizing pre-wash and modified atmosphere package (MAP) to maintain quality and extend shelf-life of table grapes. Fresh seedless grapes were prepared by cutting off the pedicels 1-2 mm from the fruit, followed by a sanitizing wash and a hot water treatment (45 °C, 8 min). The grapes were drained, cooled and packaged in containers sealed with a special gas permeable film. The packages were stored at 5 °C for up to four weeks for quality evaluation. Gas composition, texture, decay, sensory evaluation and microbial growth of cut and cluster grapes were evaluated. Results indicated that hot water treatment of grapes significantly affected package atmospheres, maintained a firmer texture, higher overall quality, lower decay rate and lower microbial population than other treatments or the control during the entire storage period. Cut grapes treated with hot water maintained the highest quality for 4 weeks with the least decay among all treatments. A chlorine pre-wash treatment significantly reduced microbial populations and maintained better overall quality. Conventionally packaged grapes developed a dark decay with unacceptable product quality by the end of the storage period.