薯蓣贮藏期不同部位的褐变生理生化差异

研究了薯蓣贮藏期间不同部位褐变相关的生理生化差异.结果表明:贮藏期间,薯蓣不同部位存在明显的褐变差异.两端的褐变度、总酚含量和多酚氧化酶活性高于中部,皮部的高于心部,使两端和皮部比中部和心部更易和更早发生褐变.两端的过氧化物酶活性高于中部,皮部的高于心部,但心部的过氧化物酶活性15 d后高于中部的,30 d时与两端的相同,这与褐变度的变化规律不同.两端的超氧化物歧化酶活性低于中部,皮部的低于心部,而两端的丙二醛含量高于中部,皮部的高于心部.因此,在薯蓣贮藏过程中,两端和皮部的脂质过氧化程度高于中部和心部,清除自由基的能力则明显低于中部和心部,导致这两个部位膜的完整性更易丧失且易发生褐变.提示薯蓣加工过程中要尽可能抑制两端和皮部的褐变,块茎采摘后不宜长久放置,应及时加工.

Browning Differences of Different Parts of the Yam during Storage

Biophysical and biochemical indexes correlating with the browning of different parts of yams(Dioscorea alata L.) during storage had been studied.The results showed that the browning differences of different parts were obvious during storage.The degree of browning,the contents of all phenolics and polyphenol oxidase(PPO) activity of both ends were higher than those of middle part,and those of cortical part were higher than those of central part.So the browning occurred more easily and early in both ends and cortical part than in middle part and central part.Peroxidase(POD) activity of both ends was higher than that of middle part,and POD activity of cortical part was higher than that of central part.But POD activity of central part was higher than that of middle part after 15 days,and was the same with that of both ends on the 30th day.That was different from the change of the degree of browning.Superoxide dismutase(SOD) activity of both ends was lower than that of middle part,and SOD activity of cortical part was lower than that of central part.But Malondialdehyde(MDA) content of both ends was higher than that of middle part,and MDA content of cortical part was higher than that of central part.So during the storage of yams,the extents of lipid oxidation of both ends and cortical part were higher than that of middle part and central part and the abilities of cleaning free radical were much lower.So both ends and cortical part easily lost the membrane integrity and browning easily occurred in the two parts.During yams processing,browning of both ends and cortical part may be restrained as soon as possible,and yams tuber should be processed in time after being picked.