FRESHNESS AS A PART OF VEGETABLE QUALITY

Fruit and vegetable are subject to an active metabolism at the time of harvest, and numerous biochemical processes are continuously changing the original composition of the crop up to the point where marketability is definitively lost.
In this chain of constant decline in quality only the first period comprising no drastic changes in composition may really be defined as the time of freshness.

Since freshness is considered to be an important part of food quality, its evaluation should rest upon objective methods.
Up to now only visual criteria for the freshness of fruit and vegetable are used, but these may be misleading and are difficult to objectivate.
Therefore, it was tried to find out marker substances, which could serve as a quality index.
The rise in free amino acids during the storage of green vegetable was studied followed by an examination of protease activities.
The results obtained with spinach and lettuce have been disappointing in spite of the fact that some authors could demonstrate a stress-depending accumulation of proline in some plant varieties.

For studies concerning the change in SH-groups during storage a kinetic method for the determination of SH-groups using 6,6′-Dithiodinicotinic acid was developed.
This method is quick (1 sample/min), sensitive (detection limit: 2,5 nMol/ml) and precise (VC 2,3 %; n=6), but preliminary results have revealed the level of SH-groups in plant extracts to be rather low.

Symposium on Quality of Vegetables

E. Schwerdtfeger

https://doi.org/10.17660/ActaHortic.1979.93.4