Effect Of Sodium Selenite Treatment On The Quality Of Storage Of Fresh-cut Lactuca Sativa L.

Lactuca sativa L.is popular in recent years.It contains a lot of mineral elements such as vitamin C,vitamin A,Ca,Fe and so on.But it is not easy to preserve,because the area of its leaf is large and its respiration rate is fast.There are many studies on selenium enrichment of fruits and vegetables before harvest at home and abroad.The result showed that selenium treatment could slow down the aging rate and prolong the shelf life of fruits and vegetables.In this paper,the fresh lettuce was used as test material.We research the effect of sodium selenite on storage quality and aroma components of fresh-cut Lactuca sativa L.,and the antagonism of heavy metals.It provide a theoretical basis for the regulation of the quality of Lactuca sativa L.by sodium selenite treatment.The results showed that(1)The quality of fresh lettuce was obviously improved after sodium selenite treatment.The fresh-cut Lactuca sativa L.and wheat were soaked in 0.5 mg/ L,1.0 mg/ L,1.5 mg/ L,2.0 mg/ L,and 2.5 mg/ L sodium selenite for 5 min,10 min,15 min,20 min and 25 min respectively.We fing that soaking in 2.0mg/L sodium selenite for 20 minutes could significantly slow down the increase of weight loss rate(P<0.05),and the decrease of soluble solids,and Vc contents in Lactuca sativa L.during storage,and the browning degree was obviously inhibited.Sodium selenite treatment delayed the quality decline rate of fresh-cut Lactuca sativa L.and effectively prolonged the storage period.(2)Sodium selenite treatment of fresh-cut Lactuca sativa L.significantly slowed down the aging rate of fresh-cut Lactuca sativa L.,slow down the decline of GSH-Px activity in Lactuca sativa L.,inhibit the increase of malondialdehyde content,and also inhibit the increase of nitrate content and nitrite content.It showed that sodium selenite could maintain the integrity of plant cell membrane,scavenge free radicals in Lactuca sativa L.,slow down the aging speed and improve the quality of fresh-cut Lactuca sativa L..The malondialdehyde content,nitrite content and nitrate content of fresh-cut group were lower than those of whole-cut group during storage.The content of nitrite in fresh-cut group was only 2.7 mg/kg on the second day,which was significantly lower than that in other groups(P<0.05).The activity of GSH-Px in whole and fresh-cut treatments was 25.85U/g.FW and 28.39U/g.FW on the 6th day,respectively.It was 2.5 times higher than that of the control group,and the difference was significant.The results showed that the preservation effect of sodium selenite on fresh-cut Lactuca sativa L.was better than that of whole rape.(3)Sodium selenite treatment of fresh-cut Lactuca sativa L.can better retain its aroma substances.The results showed that sodium selenite treatment could delay the degradation of soluble sugar in fresh-cut Lactuca sativa L..Sodium selenite treatment group and control group had differences in the content and types of aroma components.Sodium selenite made the loss of total aroma components of fresh-cut Lactuca sativa L.slow.The relative content of aldehydes accounted for 47%-64% of the total aroma components.It was characteristic aroma.Four days before storage,there was no significant difference between the treatment group and the control group.From the 4th day,the aroma components of the treated group were significantly higher than those of the control group(P < 0.05),especially those containing alcohols and acids.The change trend of esters in the treated group during storage was gentler than that of the control group.The hydrocarbons and ketone in the treated group were higher than those in the control group duringstorage,and the sulfur compounds were significantly higher at the end of storage.The results showed that sodium selenite treatment could effectively retain the volatilization of aroma substances and the edible flavor of Lactuca sativa L.rape in the later stage.(4)Sodium selenite treatment can reduce heavy metal residues in fresh-cut Lactuca sativa L.,slow down the loss of Fe elements,and increase the content of Se in Lactuca sativa L..The contents of Cr,Cd,Pb,As and Hg in the sodium selenite treatment group were lower than those in the control group,and the contents of Fe and Se in fresh-cut Lactuca sativa L.were significantly higher than those in the control group.Selenium content was 0.25 mg/kg on the fourth day,which was 5 times higher than that of the control group(P < 0.05),and the highest was 0.28 mg/kg during storage.This indicated that sodium selenite could inhibit the accumulation of heavy metals such as Cr and Cd,slow down the loss of Fe,and increase the selenium content in Lactuca sativa L..Sodium selenite treatment can delay the decrease of Vc content,soluble solids content,chlorophyll content and GSH-Px activity during storage,and prolong storage period.At the same time,it can inhibit the accumulation of nitrate content,inhibit heavy metals,reduce the toxic effect of heavy metals on them,and prolong their storage quality.It is found that sodium selenite can effectively preserve the aroma of Lactuca sativa L.and retain its edible flavor.