Physiological Mechanism Research Of Green Color Change In High Hydrostatic Pressure Treated Spinach

High hydrostatic pressure (HHP) is a novel non-thermal food processing technology due to its limited effects on food color qulity. Based on plant chlorophylls are presented in chlorophyll-protein complexes, combined with our previous research that HHP could better retain green color of spinach puree during storage, and the positive effect induced by HHP in the200lux storage was more significant than that of storage in the dark. It is speculated that physiology activities related to chlorophyll-protein complexes are still existed. The possible physiology mechanism of green color retention in HHP-treated spinach was discussed. The main results were as follows:(1) HHP treatments better retained chlorophyll fluorescence kinetics of spinach leaves during storage compared to thermal treatment, and higher Fo, Fm and Fv/Fm could be found in HHP-treated samples. The results showed that PS II primary light energy conversion efficiency and electron transfer activity were kept, they will better contribute to protection of photosynthetic apparatus. The retention of chlorophyll-protein complexes function could be reflected by higher light reaction activity, it will play a positive role for chlorophyll retention in HHP processing green color vegetables.(2) HHP treated samples showed similar trend for spinach system and thylakoid membrane solution system. HHP treatment could better retain thylakoid membrane stacked structure and harvesting light capacity, further transfer light energy to reaction center, and the positive influence could be continued to storage. HHP treatment had less effect on PsaA/B, CP47and CP43, and they had higher stability after HHP treatments. The functions of PS I and PS â…¡ could be better kept.(3) For thylakoid membrane fatty acid composition, IUFA of samples after lower pressure (100and250MPa HHP) treatments had similar change with the control, and IUFA increased with storage time. The increase of IUFA presented better fluidity and stability of thylakoid membrane wasretained after lower pressure treatments. It played a protective role for thylakoid membrane chlorophyll-protein complexes and inhibited chlorophyll degradation. However,500MPa HHP-treated samples, IUFA decreased during storage. It might be caused by inhibition of membrane lipid unsaturated enzyme activity under HHP treatment, and desaturation of fatty acid was further inhibited.(4) As thylakoid membrane initiation site affected by stress, PSâ…¡particle structure and harvesting light capacity could better retain after HHP treatment, and harvested light energy further was excited and transferred to PS II reaction center. Changes of PS â…¡ particle polypetides showed that both of HHP and thermal treatments caused degradation of CP47, D1, D2,29KD and CP26to some degree. However, degradation induced by thermal treatment was more serious than that of HHP treatments. Degradations of the above polypetides compoments in HHP-treated samples could better keep oxygen activity of PS â…¡ particle and the whold photosynthesis system activity. Hence, PS â…¡ structure and function were maintained after HHP treatment, and higher LHC â…¡ stability had positive effect on inhibition of chlorophyll degradation.