Study On The Synthesis Regulation,Physiological Activity Evaluation Of Amadori Compounds And Its Application In Cherry Tomato Powder Preparation

Fruits and vegetables are important dietary resources.For many years,the planting and production of fruits and vegetables has been showing an increasing trend in China,and the total yield in 2018 ranked first in the world.The total yield of vegetables has exceeded 700million tons and the total yield of fruits has exceeded 250 million tons.However,industrial problems are also relatively obvious.For example,the annual loss rate is also high,reaching an astonishing 30%-40%,and the proportion used in product processing is relatively low.Dehydration drying and powder preparation are one of the main forms of fruit and vegetable processing.Up to now,in the production of dried fruits and vegetables and the preparation of fruit and vegetable powder,people often only pay attention to the degree of dehydration of the product and the thermal efficiency.As for the changes of ingredients in the dehydration/drying process,only the functional ingredients such as vitamins,carotenoids and flavonoids originally contained in raw materials are concerned.However,the effects of chemical reactions,development process and new components on human health are not fully and systematically studied.In the process of drying fruits and vegetables,reducing sugars and amino acids will inevitably undergo Maillard reaction and form the initial product,Amadori compounds,which is considered to be a beneficial component with various physiological functional activities.In recent years,many studies have shown that Amadori compounds have a key impact on the improvement of functional activity of fruit and vegetable products.Enriching the content of Amadori compounds in fruit and vegetable products and preventing their transformation to Maillard end-stage substances with the deepening of processing has extremely high research value and application potential.The systematic study of the formation process of Amadori compounds,the evaluation of the physicochemical properties of Amadori compounds and their effects on human health,and the proposal of precise regulation strategies have become the key technical foundations in the fields of fruit and vegetable drying and powder production,which need to be solved urgently.Therefore,this paper mainly carried out the following work and obtained relevant results:（1）The process inspection and mechanism analysis of the vacuum dehydration reaction（VDR）were carried out,which significantly improved the yields of 12 Amadori compounds in 6 categories.This paper firstly screened three clean synthetic methods of Amadori compounds without organic phase.The vacuum dehydration reaction（VDR）with the best effect was optimized and the key factors were investigated.According to the results,mild temperature（90℃）was the most suitable for vacuum dehydration reaction,and amino acid types,water activity（Aw）and p H value were the key factors affecting the synthesis of Amadori compounds.Vacuum dehydration can keep the reaction system in an acidic environment in which Amadori compounds are relatively stable.Adjusting the vacuum degree can effectively control the Aw to quickly reach the optimum state.The yields of 6 types of Amadori compounds was as follows:acid and basic type>unique type>polar neutral type>aliphatic type>aromatic type.Under the optimal reaction conditions,the yields of 12Amadori compounds ranged from 17.89%to 90.73%,and the yields of 7 Amadori compounds exceeded 80.00%.The effect was much better than the conventional aqueous synthesis method,and the average yield is more than 40 times higher.And higher than most reported results using organic synthesis reactions.（2）Improving the separation and purification method of Amadori compounds,and it was proved that Amadori compounds have uniform mass spectrometry fragmentation rules and good storage,processing and digestion stability.After improving the separation and purification method,the average final yields of 12 pure Amadori compounds increased to41.70%,and the highest could reach 65.34%.And the unified rule of mass spectrometry fragmentation of 12 Amadori compounds was determined,which confirmed that the main characteristic fragment ions include[M+H]⁺,[M+H-n H₂O]⁺,[M+H-n H₂O-CO]⁺and[AA+H]⁺,etc.Stable physical and chemical properties are the basis and premise of the application of active ingredients.After obtaining enough pure Amadori compounds,the stability was firstly analyzed.After continuous 60-day storage reactions with different p H and additional addition of glucose and amino acids at 4℃-37℃,no severe degradation was observed for the 12Amadori compounds except at high p H（>9）,showing good stability.And Amadori compounds are more stable in acidic environments.However,when the temperature was higher than 90℃,the high temperature will lead to the degradation of Amadori compounds,especially in strongly acidic or alkaline environments.At the same time,the 12 Amadori compounds showed good digestive stability,they weren’t decomposed a lot by the digestive enzymes.And the degree of protein glycation reaction with human serum protein is much lower than that of glucose.（3）It is proved that 12 Amadori compounds have different degrees of Cu²⁺,Fe²⁺and Zn²⁺ions chelation ability and can inhibit the negative effects caused by metal ions.The intensity of metal ion chelation ability is positively correlated with the concentration of Amadori compounds.The chelating ability of Zn²⁺ion is the weakest among the three metal ions,while the chelating ability of Cu²⁺and Fe²⁺ions varies according to the types of Amadori compounds.Fru-His has the strongest chelating ability for the three metal ions.Ultraviolet-visible absorption spectroscopy（UV-vis）and emission field scanning electron microscopy（SEM）can demonstrate the formation of complexes and the changes in the surface structure of complex particles.Fourier transform infrared spectroscopy（FTIR）showed that the metal ions mainly combined with amino acid residues and changed the configuration of fructose residues.And Amadori compounds have obvious inhibitory effect on the formation of oxidative radicals caused by metal ions,which can effectively inhibit the oxidative damage of DNA caused by Cu²⁺,the Fenton reaction caused by Fe²⁺and reduce Fe³⁺ions.（4）The angiotensin-converting enzyme（ACE）inhibitory activities of 12 Amadori compounds were evaluated and the related inhibitory mechanisms were analyzed,among which acidic and basic Amadori compounds had the best inhibitory effects.IC₅₀values for 12Amadori compounds ranged from 0.150 m M to 4.204 m M,Fru-His and Fru-Glu are the only two IC₅₀values below 1 m M.Then,Fru-His,Fru-Glu and Fru-Gly were used as representatives to analyze the ACE inhibition mechanism of Amadori compounds.The main analysis methods included kinetic analysis,fluorescence spectroscopy,thermodynamic analysis,circular dichroism analysis and molecular docking.Fru-His and Fru-Glu were competitive inhibitors,Fru-His can directly bind to Zn ion,the active center of ACE.And Fru-Gly was a non-competitive inhibitor.The interaction between Amadori compound and ACE is a spontaneous phenomenon,which is more easily carried out at low temperature,and the main binding force is the formation of hydrogen bonds between each other.After binding,the secondary structure of ACE will be changed,and the active group of ACE will be transferred to the hydrophilic environment.The binding strength of the three Amadori compounds to ACE is:Fru-His>Fru-Glu>Fru-Gly.（5）The vacuum drying（VD）was analyzed and optimized to develop a cherry tomato powder with a high content of Amadori compounds up to 42.69 mg/g DW.VD processing with high Amadori compound had no negative effect on the sensory quality of cherry tomato powder,and enhanced its color brilliance and umami perception.The total phenolic content of the VD samples was higher than that of fresh tomatoes,and lycopene and total flavonoids were also well preserved.VD cherry tomato powder with high Amadori compounds content showed good functional activity.Compared with other processing samples,fresh cherry tomato and commercial tomato powder,it showed better inhibition effect of ACE,bivalent metal ion chelating ability and partial antioxidant activity.Both pearson correlation analysis and partial least squares（PLS）regression analysis showed that the increase of these physiological activities was closely related to the content of high Amadori compounds.In summary,this paper analyzed and studied 12 Amadori compounds in 6 categories,developed an efficient and clean Amadori compounds synthesis method,verified theirs stability and functional activity,and developed a cherry tomato powder with high Amadori compounds content.The paper provide theoretical basis and new ideas for the regulation and application of Amadori compounds in simulation systems and actual product processing.