Pankaj Kumar Bhowmik

Textural and Compositional Changes of Stored Iceberg Lettuce in Relation to Harvest Season and Storage Condition

The quality and storability of iceberg lettuce (Lactuca sativa L.) is dependent on growing and storage conditions, which are not completely known. Lettuce was planted at approximately monthly intervals from Sept. 2006 to Feb. 2007. Crops were harvested at approximately monthly intervals from Nov. 2006 to May 2007 and held in storage at 3 and 13°C. Effects of harvest month and storage condition on storage quality—i.e., changes in textural quality, sugar and organic acid contents—as well as shelf-life in iceberg lettuce were examined. Higher values for puncture force and breaking energy and increased sugar content were found in the cooler than in the warmer months. Lower leaf crispness was recorded after one week of storage with a greater degree at 13°C. Total soluble sugar content declined by about 56% and 32% after one week of storage at 13°C in the outer and inner leaves, respectively. Organic acid content did not show any consistent trend. At the end of the harvest season, shelf-life declined by 40% and 30% during storage at 3 and 13°C, respectively. Results indicate that low temperature during growth and storage could ensure a longer shelf-life along with a higher quality of iceberg lettuce.

Changes in Phenylalanine Ammonia-lyase Activity and Gene Expression during Storage of Asparagus Spears

A cDNA clone coding phenylalanine ammonia-lyase (PAL) was isolated from a cDNA library prepared from asparagus spears (Asparagus officinalis L. cv. Welcome) using the reverse transcription-polymerase chain reaction (RT-PCR). The partial cDNA clone encoded an mRNA of 527 bp and the derived amino acid sequence was found highly homologous to PAL from rice, maize and barley. Northern blot analysis showed an increase of pAS-PAL mRNA until 24 h at 20 °C, which coincided well with PAL activity and fiber development, suggesting that the increase is a response to the wounding associated with harvest.