Research On The Quality Analysis Of Ecologically Cultivated Red Tangerine Fruit And Its Fermented Juic

Dahongpao tangerine(Citrus tangerina Hort.ex Tanaka)is one of the original citrus varieties in China.It is a characteristic citrus resource in Chongqing.Wanzhou District is the largest cultivated area of Dahongpao tangerine.In order to improve the utilization value of Dahongpao tangerine and strengthen the utilization of Dahongpao tangerine resources,this paper analyzed the nutritional components,pesticide residues and heavy metal content of ecologically cultivated Dahongpao tangerine.Taking ecological Dahongpao tangerine as raw material,the screening of fermentation strains,optimization of fermentation process and analysis of nutrient changes related to fermented juice were carried out.The main results are as follows:1.Analysis of fruit quality of ecological cultivation Dahongpao tangerine.The contents of total flavonoids,β-carotene,reducing sugar,soluble solids,pesticide residues and heavy metals in Dahongpao tangerine fruits under ecological cultivation and conventional cultivation conditions were compared and analyzed.The results showed that the contents of total flavonoids(3.15 mg/kg-4.92 mg/kg)andβ-carotene(3.25 mg/k-3.49 mg/kg)in samples S1,S2 and S3 were higher than those in samples F1,F2 and F3(2.32 mg/kg-2.97 mg/kg)andβ-carotene(2.64 mg/kg 2.93 mg/kg).The reducing sugar of ecological samples was 14 g/L-19.8 g/L higher than that of conventional samples.The soluble solids of conventional samples were slightly higher than that of ecological samples.Only one of the three ecological cultivation samples detected two pesticides,and the residues were 0.2%and 1.35%of the limit standard.Among the three conventional cultivation samples,there were two fresh fruit samples with excessive isocarbophos.There was no significant difference in heavy metal content between ecological cultivation and conventional cultivation,and all contents did not exceed the national standard.Therefore,the ecological cultivation of Dahongpao tangerine fruit quality is better and safer.2.Screening of Dahongpao tangerine fermented juice strains.Three strains of suspected lactic acid bacteria J2,LA8 and LB21 with good growth were screened out.J2was isolated from the surface of Dahongpao tangerine fruit,and LA8 and LB21 were isolated from litchi pulp.All three strains were Gram-positive and had calcium-dissolving circles.They were identified as Lactobacillus plantarum by 16 S r DNA sequence analysis.The Dahongpao tangerine juice fermented by strain LB21 was sweet and sour,and the aroma was obvious.The number of viable bacteria reached 2.8×10~9CFU/mL,which was used as the fermentation bacteria of Dahongpao tangerine juice.3.Process optimization of Dahongpao tangerine fermented juice.The total acid content and sensory evaluation are the main influencing indicators.The fermentation process flow is mainly the preparation of fermentation seed liquid,raw material pretreatment,enzyme demodulation acid,sterilization cooling,inoculation fermentation,cold storage after ripening and so on.The optimal levels obtained by single factor experiments and orthogonal experiment were as follows:0.8%inoculation amount,fermentation time 24 h,fermentation temperature was 37℃,solid-liquid ratio was 1:1,and sugar content was 11%.4.Changes of nutritional components and antioxidant activity of Dahongpao tangerine fermented juice,After fermentation,the number of viable bacteria in the fermented juice of the ecological sample was about 2 times that of the fermented juice of the conventional cultivated Dahongpao tangerine.Before fermentation,the main organic acids were citric acid(2273.68 g/mL),malic acid(480.51 g/mL),lactic acid(56.47g/mL)and acetic acid(13.32 g/mL).After fermentation by Lactobacillus plantarum LB21,citric acid decreased by 86.66%,malic acid decreased by 99.17%,lactic acid increased by92 times,and acetic acid increased by 31 times.The reducing sugar decreased from 23.8g/L to 13.1 g/L,and the total phenol decreased from 0.4%before fermentation to 0.3%.The contents of total flavonoids andβ-carotene decreased.The contents of total flavonoids in ecological samples S4,S5 and S6 were between 1.12 mg/kg and 2.38 mg/kg,and the contents of F4,F5 and F6 in conventional group were between 0.47 mg/kg and 1.08 mg/kg.The content ofβ-carotene in ecological samples was between 0.55 mg/kg and 0.8 mg/kg,and the content ofβ-carotene in conventional cultivation samples was between 0.2 mg/kg and 0.66 mg/kg.The DPPH free radical scavenging rate increased from 45.56%to 47.5%,and the hydroxyl radical scavenging rate increased from 1.81%to 4.07%,and the antioxidant capacity increased slightly.The pesticide residues in fermented juice were extremely low,and 0.015 mg/kg of pyraclostrobin was detected in F4,but it did not exceed the standard.The contents of four heavy metals decreased,and the transfer rate of the two safety indicators was low for fresh fruit.5.The safety analysis of Dahongpao tangerine fermented juice and its quality change during the storage period.The pesticide residues in red tangerine fermented juice were extremely low.F4 detected 0.015 mg/kg of ethofenprox but did not exceed the standard.The content of four heavy metals decreased,and the two safety indicators had a low transfer rate for fresh fruit.Detection of four harmful bacteria that Salmonella,mold yeast,Staphylococcus aureus and Escherichia coli in Dahongpao tangerine fermented juice.The results shown that there were no harmful bacteria,so that the microbial health indicators of Dahongpao tangerine fermented juice were qualified.After 22 days of storage,the p H value of the fermented juice decreased from 3.76 to 3.21,the hydroxyl radical scavenging rate decreased from 7.11%to 4.07%,the antioxidant activity decreased,the soluble solids decreased by 0.3%,there were bad flavors,the quality decreased rapidly,and the shelf life was short.