| Mulberry leaf is a traditional medicinal and edible plant resource.At present,the application of mulberry leaf is mainly distributed in the production of mulberry leaf tea and feed industry,while the application of mulberry leaf in other fields of food or as a health food development report is relatively few.GABA is an important inhibitory neurotransmitter with multiple functions.There are many reports on GABA enrichment,but mainly focus on the preparation of high GABA tea by various techniques and means.A small number of studies using asparagus,soybean leaves,pork and mulberry leaves have also been reported.Most of the pretreatment processes are complicated and the temperature is difficult to control,which requires further optimization of the process and improvement of production equipment.Studies on mulberry leaves,a leafy plant,did not consider color change and how to combine GABA enrichment with green protection.Therefore,it is of great application value to systematically explore the GABA enrichment process conditions of mulberry leaves and combine with green protection.Considering that mulberry leaves are rich in glutamic acid,and mulberry leaves themselves have a variety of functional components,this project intends to study the influence of different detoxification technologies and certain color protectants on the color change of mulberry leaves according to the composition characteristics of mulberry leaves.On this basis,the influence of different enrichment technologies on GABA in mulberry leaves is studied.Through systematic study,the optimal process conditions conducive to GABA enrichment are obtained.The high GABA mulberry green powder was prepared under this technological condition,and the chemical characteristics of main food of mulberry green powder were studied and the preliminary application study was carried out,so as to provide support for the application of mulberry leaves in food as a resource for both medicine and food.(1)The effects of different thermal detoxification methods on enzyme activity,chlorophyll,polyphenols and color change of mulberry leaves were analyzed.Three optimal thermal detoxification methods were obtained,which were 80 g fresh mulberry leaves: 1L boiling water blanching detoxification 120 s,steam detoxification 180 s and microwave detoxification 150s(500w).At this time,peroxidase and polyphenol oxidase are completely inactivated,and the degradation of chlorophyll and polyphenol is slowed down,which can maximize the retention of chlorophyll and polyphenol in mulberry leaves.Based on the conditions of hot detoxification,three color protectants,citric acid,sodium bicarbonate and sodium isoascorbate,were sprayed before and after detoxification,and the effects of spraying concentration on chlorophyll,polyphenols and color change of mulberry leaves were investigated,and nine optimal compound green protection processes were obtained.In addition,the protection effect of 9 kinds of green protection technology combined with color protection agent on chlorophyll and polyphenols of mulberry leaves was better than that of single green treatment.Through the comparative analysis of 9 kinds of compound green protection technology from taste components,functional components and color change,the results showed that: in taste components of mulberry leaves,soluble sugar content and total acid content increased compared with fresh leaves.The content of total sugar and free amino acid in mulberry leaves decreased compared with fresh leaves.Among the color change and functional components of mulberry leaves,the retention rates of chlorophyll,polyphenols and flavonoids of mulberry leaves were the highest when BB treatment was applied,and all of them were higher than that when blanching only,indicating that spraying sodium bicarbonate had a protective effect on chlorophyll and polyphenols,which could reduce the damage to them by high temperature blanching.The analysis results of color change were consistent with those of BB treatment.The retention rate of polysaccharide and GABA of mulberry leaves was also higher with BB treatment,indicating that blanching green and spraying sodium bicarbonate could kill enzymes in a short time and reduce the loss of functional components to a large extent.In summary,with the protective effect of mulberry leaf color as the main objective of investigation and comprehensive consideration of taste components and other functional components of mulberry leaves,blanching Qingqing combined with spraying sodium bicarbonate was selected as the best green protection process,namely BB process.(2)On the basis of the above-mentioned green protection technology,the anaerobic and aerobic alternating treatment of mulberry leaves was carried out,and the optimal time of aerobic/anaerobic alternating treatment was discussed.The results showed that anaerobic8h-aerobic 2h-anaerobic 4h was the appropriate aerobic/anaerobic combined treatment time,denoting as IA.At this time,GABA content of mulberry leaves was 4.993mg/g dry base,which was 63.0% higher than that of fresh leaves.Chlorophyll content was 5.921mg/g in dry base,which retained 60.0% compared with fresh leaves.The polyphenol content was 7.967mg/g in dry base,which retained 75.5% compared with fresh leaves.Based on IA,the effects of adding different exogenous substances combined with aerobic/anaerobic treatment on GABA in mulberry leaves were respectively compared,and compared with low temperature refrigeration treatment,the best process conducive to GABA enrichment was explored.First,response surface optimization was carried out for GABA enrichment process of mulberry leaves with glutamic acid and sodium salt addition.The optimal process parameters were obtained as follows: sodium glutamate addition,spray concentration of 1.5 %,treatment time of 2.5h,denoted as IB.The analysis of GABA enrichment process of mulberry leaves by adding vitamins and minerals showed that adding 0.3%vitamin B6+0.3% calcium chloride was the optimal condition,denoting as IC.At this time,the GABA content of mulberry leaves was 5.908mg/g dry base,which was 63.8% higher than that of fresh mulberry leaves.The green content of leaves was 10.141mg/g dry base,and the retention rate reached 89.2%.The polyphenol content of mulberry leaves was 14.198mg/g dry base,and the retention rate was 91.2%.The process of GABA enrichment in mulberry leaves by lactic acid bacteria was analyzed,and the results showed that the optimal conditions for GABA enrichment were obtained when the concentration of lactic acid bacteria was 2%,denoted as ID.The influence of low temperature refrigeration time on GABA of mulberry leaves was explored.The results showed that 4h of cold shock was the appropriate treatment time.At this time,GABA content of mulberry leaves was 4.299mg/g dry base,which was 19.2% higher than that of fresh mulberry leaves,and was denoted as CT.Mulberry leaves enriched with GABA by IB,IC,ID and CT processes were then subjected to blast drying and grinding to prepare mulberry leaf coarse powder.The results showed that the IB process had the best GABA enrichment effect on mulberry leaves,and the destruction rate of polyphenols and flavonoids was lower.(3)The coarse mulberry leaf powder(40 mesh)prepared by IB process was crushed,and 40 mesh,100 mesh and 30 s,60s and 90 s mulberry green powder were respectively obtained,which were recorded as A,B,C,D,E,and the effects of ordinary grinding with different particle size and ultramicro grinding time on the quality characteristics of mulberry green powder were studied.The results show that: With the decrease of ordinary grinding size and the extension of ultramicro grinding time,the particle size of mulberry green powder gradually decreases,and the particle size distribution is more and more uniform.Among them,the particle size of ultramicro grinding 30 s powder is larger than that of ordinary grinding 100 powder,indicating that ordinary grinding 100 mesh powder is better than ordinary grinding 30 s powder,until ultramicro grinding 90 s,mulberry green powder reaches ultramicro particle size.The color becomes more green,the Angle of repose becomes larger,and the water solubility increases.With the decrease of particle size,the contact area with extractants increased,soluble sugar,soluble dietary fiber,free amino acid and other soluble components increased.Large molecules such as fat,protein and insoluble dietary fibre are reduced.The contents of GABA,polyphenols,flavonoids and alkaloids decreased with the decrease of particle size and the extension of ultramicro grinding time,except for a small increase of chlorophyll content.In general,ultramicro grinding is beneficial to the application of mulberry green powder in food processing.Ultrafine mulberry green powder was used as raw material to prepare ultrafine mulberry green powder effervescent tablets.Through single factor experiment,orthogonal optimization experiment and verification experiment system,optimized technological conditions for preparation of ultrafine mulberry green powder effervescent tablets were studied,and the optimum formulation for preparation of ultrafine mulberry green powder effervescent tablets(tablet weight 1g)was determined.The results were as follows: acid-base ratio 1: 1.0(0.317 g citric acid,0.158 g malic acid,0.475 g sodium bicarbonate),disintegrating agent 0.95 g,PEG 0.175 g,sweetener 0.05g(0.5g xylitol,0.5g sucrose,0.05 g acesulfamil).Based on the Chinese Pharmacopoeia(2020 edition),the results of this study and related literature,the corresponding quality standards for ultramicro mulberry green powder effervescent tablets were established.The effervescent tablets prepared by the optimized technology were complete in appearance,with an average mass of 1.004g±0.016,disintegration time of 3.35 min,p H of 4.8,gas production of 0.15g±0.02 and fracture of 28 kg.This product tablet particles small,easy to form,hardness is larger,the tablet integrity is not easy to break.The cohesive value is moderate,the binding effect between particles is strong,the tablet has a strong ability to resist damage.High fracture,not easy to deformation,easy to transport. |
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