Abstract:

In order to study quality changes of Chinese small cabbage (Brassica rapa L.Chinensis Group.) during storage,
chlorophyll, reduced ascorbic acid content and sensory evaluation of Chinese small cabbage stored at 278, 283, 288 and
293 K were determined for kinetic analysis and shelf life prediction. A non-linear fitting of reaction rate k as a function of
temperature T based on Arrhenius law was also studied, from which a shelf life prediction model of Chinese small cabbage
describing shelf life (SL) as a function of temperature T and quality index M was obtained. The results showed that when
Chinese small cabbage was stored at lower temperature, chlorophyll and reduced ascorbic acid were degraded slower. Zeroorder
law was more appropriate than first-order reaction kinetics to describe the degradation of chlorophyll and reduced
ascorbic acid with active energy Ea of 93.27 and 85.27 kJ/mol, respectively. In addition, the shelf life based on a chlorophyll
loss of 20% was more approximate to that at a cut-off score of 3.5 by sensory evaluation, when the loss of reduced ascorbic
acid was more than 20%. Therefore the characteristic index and ending point to predict shelf life should be depended on
reality and needs in order to obtain an accurate shelf life prediction.

Key words: Chinese small cabbage, reduced ascorbic acid, chlorophyll, kinetic model, shelf life prediction