Nitrogen retards and oxygen accelerates colour darkening in faba bean (Vicia faba L.) during storage
S.M. Nasar-Abbas, J.A. Plummer, K.H.M. Siddique, P.F. White, D. Harris and K. Dods
Postharvest Biology and Technology, Volume 47, Issue 1, January 2008, Pages 113-118
2008
บทคัดย่อ
Modified atmosphere packaging (MAP) techniques were applied in order to control seed coat (testa) colour darkening in faba bean during long-term storage. These techniques included flushing with carbon dioxide, nitrogen, oxygen or ethylene, and vacuum packaging. Seeds flushed with air were used as the control. After MAP treatments, samples were stored at 30 °C in dark for 1 year. Seed coat colour was measured at 0, 0.5, 1, 2, 3, 4, 6, 8, 10 and 12 months of storage using a chroma meter. Changes in chroma (C*), hue angle (h°) and colour difference index (DE*ab values) calculated from L*, a* and b* colour coordinates demonstrated that relative to controls, nitrogen was effective in reducing colour darkening by an appreciable level, whereas storage in oxygen accelerated the colour darkening process. Ethylene had some effect whereas the other MAP treatments were ineffective in reducing colour darkening in faba beans.
Analytical studies revealed that tannin compounds were the major constituents of total phenolics in faba bean of which proanthocyanidins were the predominant component group. Tannin concentration was negatively correlated with colour darkening in faba bean. Air, vacuum and ethylene treated samples showed similar changes in phenolic constituents after 12 months storage but samples flushed with CO2 and especially those flushed with O2 had much higher losses in phenolic constituents demonstrating that colour darkening is likely to be due to oxidative transformation of phenolic contents.