The Effects Of Glutamate Treatment On Quality And Accumulation Of Bioactive Components In Fresh-Cut Carrot

Glutamate,as an amino acid,widely existing in nature,plays a vital role in plant metabolism.Glutamate plays a crucial role in plant metabolism,on the one hand,it connects the tricarboxylic acid cycle through y-aminobutyric acid branch;on the other hand,it regulates plant nitrogen metabolism together with glutamine.Glutamate as a plant defense response signal molecule has been gradually clarified in recent years Recent studies have gradually identified that glutamate plays as a signal molecule to resist the response in plants.Fresh-cut carrots are popular in public because of their convenience and delicious taste.A large number of scientific studies have shown that mechanical damage caused by cutting leads to whitening and susceptibility to microbial infection.Most studies have focused on the storage and preservation of fresh-cut carrots,while few studies have focused on the nutritional enrichment of fresh-cut products.The purpose of this study is to promote the nutritional enrichment of fresh-cut carrots.The effects of glutamate treatment on the contents of bioactive components in fresh-cut carrot during 48 h storage,under the conditions of 15? and 80?90%relatively humidity were studied,concerning commercial value and food safety of fresh-cut carrots,the possible mechanism of glutamate treatment on the accumulation of phenolic compounds and GABA was also revealed,thereby providing people and factories with convenient,safe and efficient processing methods to improve the nutritional value and added value of fresh-cut carrots.The main findings are as follows:1.The optimal concentration of glutamate was 0.50 g·L-1.Fresh-cut carrot were maintained at 15?,80?90%RH,48 h after 10 min of glutamate treatment,glutamate treatment could keep quality and food safety of shredded carrots,compared with control,as well as a significant increase in total phenolic content and GABA content in shreded carrot(p<0.05).2.Glutamate treatment could delay the degradation of total carotene of shreded carrot,produce bitter and astringent taste and decrease salty taste during storage,but had no significant effect on sour taste and richness,meanwhile,glutamate treatment could maintain the fresh-cut shreded carrots' fresh flavor in earlier storage period.The value of sensors which are sensitive to characteristic aroma terpenes and alkanes decreased during storage,but that of the aromatic increased significantly.Compared with control,Glutamate treatment had no adverse effect on the taste,hardness and color of shreded carrot,and could maintain the sensory quality of shreded carrot.3.The result of the effect of glutamate treatment on the metabolism of reactive oxygen species(ROS)showed that glutamate treatment could significantly increase the activities of antioxidant enzymes such as superoxide dismutase(SOD),catalase(CAT),peroxidase(APX),peroxidase(POD)and 1,1-diphenyl-2-picrylhydrazyl(DPPH)free radical scavenging rate,reducing the rate of formation of superoxide anion(O2·-))the content of hydrogen peroxide(H2O2),the content of active oxygen free radical in fresh-cut carrot was decreased,and the quality of fresh-cut carrot was delayed.4.The results showed that Glutamate treatment could effectively increase the content of total phenol in fresh-cut carrot.The content of total phenol in fresh-cut carrot after 48 hours storage at 15? could reach nearly 8 times of the initial value.It was found that glutamate treatment could significantly increase the activities of phenylalanine aminoacid(PAL),cinnamate 4-hydroxylase(C4H),4-coumarate-coA ligase(4CL),and activate phenylpropanoid metabolic pathway in rats treated with glutamate,and increase the activities of PAL,C4H and 4CL,thus,the content of phenolic compounds is improved.The results of HPLC analysis showed that glutamate treatment can further induce the secondary metabolism,increase the content of monomeric phenol,and then increase the content of total phenol.5.The effect of glutamate treatment on GABA metabolism was studied.The results showed that glutamate treatment could significantly increase GABA content,mainly due to the high activities of glutamate decarboxylase(GAD)and GAB A transaminase(GABA-T),the net increase in GABA content is caused by synthesis rate is higher than decomposition rate of GABA.