Study On Browning Inhibition Of Glutamic Acid Solution On Fresh-cut Potatoes

In China,fresh-cut potatoes have very broad market prospects.However,it is inevitable that potatoes will be damaged mechanically during fresh-cut processing.Therefore,browning is very easy to occur on the surface of potatoes,which is an important factor leading to the decline of the sensory flavor and nutritional quality of fresh-cut potatoes.In particular,browning of fresh-cut potato shreds is serious during storage logistics due to the high degree of cutting.In view of the browning of fresh-cut potatoes,the existing browning inhibition methods cannot fully meet the needs of industrial production of fresh-cut potatoes,making it particularly important to develop new safe browning inhibitors.In this study,the Netherlands No.15 potato was selected as the raw material for fresh-cut potato shreds.This study optimized the optimal technical conditions for glutamic acid solution to inhibit the browning of fresh-cut potatoes,including soaking concentration and time,then preliminarily explored the mechanism of glutamic acid solution inhibiting the browning of fresh-cut potatoes,with the aim of finding a new anti-browning agent that can effectively prevent browning,so as to provide a theoretical and technical basis for prolonging the shelf life of fresh-cut potatoes.The main results of the research are as follows.(1)Glutamic acid solution concentrations(0.5%,1.0%,1.5%and 2.0%)and dipping time(1 min,2 min,3 min,4 min and 5 min)were screened to determine the best treatment condition.The results showed that the suitable conditions were dipping fresh-cut potatoes in1.5%glutamic acid for 4 min.Under this condition,the shelf life of boxed fresh-cut potato shreds can be prolonged to 4 days at 4?(the shelf life of the control is 0.5 days),maintaining good commercial value during the period.Furthermore,the glutamic acid solution had a unique flavor,which improves the flavor of fresh-cut potato shreds and obtains a higher sensory evaluation score.(2)The fresh-cut potato shreds were soaked in a 1.5%glutamic acid solution for 4minutes.During storage,the activity of the browning-related enzymes(such as PPO,POD and PAL)and the total phenol content of the fresh-cut potato shreds were determined.The results showed that glutamic acid inhibited the browning of fresh-cut potato shreds mainly by inhibiting the activity of PPO and the decrease of total phenol content in the early storage period.POD and PAL in fresh-cut potato were activated in response to external stress.By enhancing the potato's resistance to stress,the decline of the related quality of fresh-cut potatoes are delayed.(3)Glutamic acid inhibited PPO activity by lowering the pH of potatoes and chelating the PPO active center copper ions to slow down the browning process of fresh-cut potatoes,and its inhibitory ability increased with the increase of solution concentration and the decrease of pH.The glutamic acid solution with a concentration of 1.5%almost completely lost the PPO activity of potatoes.The glutamic acid solution had a significant inhibitory effect on the PPO enzyme activity.When the pH returns to the control(deionized water group),the PPO activity cannot be completely restored.At the same time,when the pH of potato pulp was reduced to the same level after treatment with glutamic acid solution,the inhibitory effect of glutamic acid solution on PPO cannot be achieved.The results showed that lowering pH is not the only factor that glutamic acid inhibits PPO activity.Glutamic acid had the ability to chelate copper ions,and the addition of copper ions in the form of copper sulfate can partially restore the PPO activity reduced by the glutamic acid solution,indicating that glutamic acid can chelate Cu²⁺in the active center of PPO to inhibit PPO activity.(4)The glutamic acid solution significantly inhibited the browning of potato pulp,which can make the reddish-brown substances produced by the medium browning of the pulp gradually disappear,and it also has a significant effect on the black browning products produced by the severe browning.Glutamic acid solution had the ability to inhibit the production of quinones and delayed the occurrence of browning by inhibiting quinones.(5)Glutamic acid participated in the production of free amino acids in fresh-cut potato shreds and stably maintains a high free amino acid level,avoiding the aggravation of browning caused by the reduction of free amino acids during storage.In particular,it promoted an increase in the content of amino acids known to inhibit browning and induce resistance,such as cysteine,aspartic acid,proline,and?-aminobutyric acid.The glutamic acid solution's ability to inhibit browning of fresh-cut potatoes was further improved.(6)The effect of glutamic acid and two common browning inhibitors(ascorbic acid,citric acid)were compared under the same concentration conditions.Fresh-cut potato shreds were stored for 4 d at 4?and the effect of glutamic acid browning inhibition was lasting better than that of ascorbic acid and citric acid.Considering the sensory quality,glutamic acid meets the needs of industrial processing of fresh-cut potato shreds.Therefore,it can replace citric acid and ascorbic acid as an effective browning inhibitor in the production of fresh-cut potato shreds.