Metabolome Analysis Of Lemon Juice And Development Of Lemon Fruit Powder

Lemon is rich in vitamins,amino acids,dietary fiber and other nutrients as well as flavonoids,phenolic acids,essential oils and other bioactive components.Currently,lemons are consumed mainly by fresh fruits and processed products.Lemon juice(LJ)is one of the most important products of lemon products,which can be divided into raw lemon juice and juice concentrate.During the juicing process of lemon,most of which free water water and water-soluble substances constitute LJ,while the peel,juice capsule residue,seeds and some insoluble substances constitute pomace(LP).However,current studies on lemons have focused on the extraction of active substances in them and their bioactive capacity,and there is a lack of research on the differences of substances in lemons during the juicing process and the quality of lemon juice.Based on this,this study investigated the fractionation of active substances in lemons during the juicing process and the differences in nutrients and active substances among LF,LJ and LP from the perspective of food ingredients using metabolomics techniques.Meanwhile,starting from whole fruit lemon juice(WLJ)and peeled lemon juice(PLJ),a systematic comparison of nutrients and active metabolites of the two lemon juices was conducted to investigate the molecular mechanisms of flavor differences and to provide a theoretical basis for the development of LJ industry.The main findings were as follows.Firstly,the nutritional composition and active substances of LF,LJ and LP were compared.The results of the study showed that there were differences in the nutritional composition of LF,LJ and LP.A total of 970 metabolites were identified by the metabolome,and 440 differentially abundant metabolites(DAMs)were screened out between LJ and LP,suggesting significant metabolite fractionation during juicing.The“flavonoids”,“phenolic acids”,and “saccharides and alcohols” were mainly retained in the LP,while the fractionation of major “organic acids” was differentiated.Seven of the12 potential bitter metabolites were more abundant in the LP and two were more abundant in the LJ,suggesting that LP would be more bitter.L-Ascorbic acid,thiamine,and acitretin were significantly lost during juicing,while riboflavin was newly dissolved during juicing.The antioxidant capacity of LP was significantly higher than that of LJ,which was closely related to the higher abundance of phenolic acid metabolites in LP.These findings suggtested that promoting the release of flavonoids and phenolic acids from LP is a potential strategy to improve the quality of LJ.Results also provides important information and reference for developing high-value products by using LP.There were differences in the nutritional composition between WLJ and PLJ,and the peel was found to influence the nutrition and quality of LJ.A total of 969 metabolites were identified by metabolomics,and 306 DAMs were screened in WLJ and PLJ."Flavonoids","phenolic acids","organic acids" and "sugars and alcohols" were found to have the highest total abundance in WLJ."Among the 13 vitamins,only vitamin K2 was more abundant in the PLJ than in the WLJ,which was related to the solubility of vitamin K2.The antioxidant capacity of WLJ was significantly stronger than that of PLJ,which was closely related to flavonoids,phenolic acids and vitamin C-like substances in WLJ.In order to retain the active substances in LF to the greatest extent,we carried out colloid mill crushing and wall breaker crushing treatment on LF,and found that the colloid mill crushing treatment could crush the tissue structure of LF evenly.After vacuum freeze-drying,the whole fruit powder of lemon was obtained.There was no difference between the fruit powder obtained by the two crushing methods,but the fruit powder after the wall breaker treatment had better fluidity.The fruit powder,lactose,microcrystalline cellulose and magnesium stearate were hand-pressed in the ratio of50%,39%,10% and 1%,and each index of the resulting tablets met the requirements of the Chinese Pharmacopoeia.In this study,we investigated the differences in nutrients and lemon juice quality during lemon juice extraction,and explored the fractionation of active substances and molecular mechanisms of lemon juice flavor differences during lemon juice extraction with the help of metabolomics analysis.The results of the study provide basic information for the production and processing of lemon juice and provide a theoretical basis for the high-value processing and utilization of lemon pomace.The whole fruit powder of lemon obtained through the crushing of colloid mill and wall breaker provides new directions for the processing and utilization of lemon whole fruit and expands the application of lemon products.