Course Of Shelf Life Research Articles

NONDESTRUCTIVE EXAMINATION OF TOMATO DURING THE COURSE OF SHELF LIFE

A nondestructive ultrasonic method was used to monitor the firmness and sugar content of greenhouse tomatoes (cv. 870) during their shelf life. This method is based on measurement of acoustic wave attenuation in the fruit tissue, by means of ultrasonic probes in contact with the fruit peel. The differences in the acoustic signals transmitted through the tissue of fruits of various degrees of firmness were measured and analyzed. The fruits for measurement were transferred from a greenhouse to a controlled-temperature room, and experiments were carried out at intervals throughout the storage period. The fruits were subjected to nondestructive ultrasonic tests and also to destructive penetration measurements of firmness. The results were analyzed statistically to determine the changing relationships between the ultrasonic attenuation measurements and the destructive measurements, during the course of shelf life. The measured attenuation was found to be significantly decreased and the firmness was obviously found to decrease significantly in the course of shelf life. A linear relationship between the attenuation and the firmness was observed until the end of the softening process. This suggests that this ultrasonic method might be used as a nondestructive means of monitoring the firmness of tomatoes during various stages of storage.

Modification of cell wall properties in lettuce improves shelf life.

It is proposed that post-harvest longevity and appearance of salad crops is closely linked to pre-harvest leaf morphology (cell and leaf size) and biophysical structure (leaf strength). Transgenic lettuce plants (Lactuca sativa cv. Valeria) were produced in which the production of the cell wall-modifying enzyme xyloglucan endotransglucosylase/hydrolase (XTH) was down-regulated by antisense inhibition. Independently transformed lines were shown to have multiple members of the LsXTH gene family down-regulated in mature leaves of 6-week-old plants and during the course of shelf life. Consequently, xyloglucan endotransglucosylase (XET) enzyme activity and action were down-regulated in the cell walls of these leaves and it was established that leaf area and fresh weight were decreased while leaf strength was increased in the transgenic lines. Membrane permeability was reduced towards the end of shelf life in the transgenic lines relative to the controls and bacteria were evident inside the leaves of control plants only. Most importantly, an extended shelf-life of transgenic lines was observed relative to the non-transgenic control plants. These data illustrate the potential for engineering cell wall traits for improving quality and longevity of salad crops using either genetic modification directly, or by using markers associated with XTH genes to inform a commercial breeding programme.

Assessing plum fruit quality attributes with an ultrasonic method

A nondestructive ultrasonic method was used to determine the maturity and sugar content of plum fruits (cv. `Royal Z') during storage. This method is based on measurement of acoustic wave attenuation in the fruit tissue, by means of ultrasonic probes in contact with the fruit peel. The differences in the acoustic signals transmitted through the tissue of fruits at different states of maturity were measured and analyzed. The fruits for measurement were transferred from storage to room temperature. Experiments were carried out at intervals throughout the storage period. The fruits were subjected to nondestructive ultrasonic tests as well as to destructive penetration measurements of firmness and sugar content, and the relationships between the ultrasonic attenuation measurements and the destructive measurements determine during the course of shelf life. The measured attenuation, the firmness, and sugar content were found to decrease in the course of shelf life. A link between the attenuation and the firmness could be observed from 78 h in shelf life until the end of the softening process. This suggests that this ultrasonic method might be used as a nondestructive technique for monitoring the firmness of plums during progressive stages in storage time. The changes in sugar content showed a decreasing trend with storage time in this study; this phenomenon is not clear yet and needs to be further investigated.