Extraction And Identification Of Active Substances From Sweet Sorghum And Their Effects On Beef Preservation

In the north of China,sweet sorghum is cultivated with abundant varieties and high yield,which is mainly used for sugar production.In the process of sugar production,a large amount of sweet sorghum residue will be formed,accounting for about a quarter of the weight of sweet sorghum.In addition to a large amount of dietary cellulose and polysaccharide,sweet sorghum residue also contains a large number of polyphenols and flavonoids,which have excellent antioxidant activity and free radical scavenging ability.At present,most of the researches on sweet sorghum polyphenols are focused on separation and purification,but the researches on the structure identification and biological activity of sweet sorghum polyphenols and the rapid determination of antioxidant active substances in the polyphenols are relatively few.In this paper,the optimal technological means of extracting polyphenols from sweet sorghum residue by ultrasonic assisted chemical solvent extraction and ion precipitation were studied.The molecular structure of polyphenols was determined by HPLC-ESI-MS,and a new method of simple and rapid detection of antioxidant active ingredients by HPLC post-column derivatization was established.The antioxidant characteristics and mechanism of phenolic extracts from sweet sorghum were studied.At the same time,the effects of sweet sorghum phenolic extracts on beef quality,protein oxidation and lipid oxidation,and the microbial diversity of chilled beef treated with sweet sorghum polyphenols during the whole storage period were studied.In order to improve the comprehensive utilization of sweet sorghum sugar industry,and for further systematic research and development of sweet sorghum polyphenols,the engineering technology and theoretical basis for reference were put forward.The main results are as follows:(1)Residue of sweet sorghum as raw material to study the ultrasonic assisted extraction sweet sorghum ethanol precipitation method and ion optimum process conditions of polyphenols,affecting the sweet sorghum polyphenols extract extraction rate of the most important factors: the type of solvent,ultrasonic output power,extraction temperature,extraction time,ratio of feed liquid and ethanol content of single factors and the interplay between the research.The optimal extraction conditions were as follows: acidic ethanol content 60%,solid-liquid ratio 1:20,extraction temperature 40℃ and ultrasonic treatment time 1 hour.HPLC-ESI-MS was used to separate and determine the polyphenol extract of p sweet sorghum.A total of18 phenolic compounds were isolated,including hydroxymethyl furfural,hydroxymethyl furan aldehyde,tert-butylphenol and other phenolic compounds with antioxidant activity.(2)A fast online detection method for antioxidant active components of sweet sorghum polyphenol extract was established.After optimization of online system parameters,a total of 7 compounds with strong antioxidant activity were screened from the crude extract of sweet sorghum polyphenols,which were coumarin,cinnamic acid,quinic acid,caffeic acid,coumarin,catechin and citric acid in order,belonging to the strong antioxidant with development and research potential.In a certain range,antioxidant capacity and free radical scavenging capacity.When the extraction concentration of sweet sorghum polyphenols was 50 μg/m L,the total antioxidant level was about 51.95 mmol/m L,the DPPH,superoxide anion and hydroxyl radical elimination capacities were 82.08%,81.15% and 61.46%respectively.(3)The results showed that sweet sorghum polyphenol extract had strong antibacterial activity against foodborne pathogenic bacteria Escherichia coli,Staphylococcus aureus,Listeria monocytogenes and Salmonella,and the minimum antibacterial content was 2.5 mg/m L,0.625 mg/m L,1.25 mg/m L and 2.5 mg/m L,respectively.The direct inhibition of sweet sorghum polyphenols against Grampositive bacteria was better than that against gram-negative bacteria.At the same time,sweet sorghum polyphenol extract can also control the protein synthesis of STaphylococcus aureus to some extent,especially the key proteins in the metabolic process of bacteria.In addition,after the sweet sorghum polyphenols extract treatment,bacteria cells inside and outside structure also produces change,bacterial cell membrane structure of the original complete sex,to produce the plasmolysis phenomenon,in the chamber is formed in bacterial cells,bacteria containing material leakage and,in turn,affect the normal physiological metabolism process of bacteria,and eventually played an inhibition of bacteria breeding.(4)It was found that sweet sorghum polyphenols could prolong the storage life of chilled beef by 4 days when the concentration of sweet sorghum polyphenols extract was 20 g/L.During the whole beef storage period,p H value,chroma,cooking loss and surface hydrophobicity were increased,while pressure loss,tenderness,hardness,elasticity,chewiness and resilience were decreased.However,sweet sorghum polyphenol extract could inhibit the changes of meat quality,and the meat quality of beef was significantly higher than that of control group(P<0.05).Moreover,it can improve some important meat quality indexes such as tenderness and water retention in different degrees.At the same time,polyphenols also have positive effects on protein oxidation and lipid oxidation,which can delay the rate of protein oxidation and lipid oxidation.Compared with the control group,the values of TBARS and POV of beef in the treatment group were significantly lower than those in the control group(P<0.05),carbonyl content was significantly decreased(P<0.05).(5)By using sweet sorghum polyphenols beef before and after the treatment of bacterial populations in the storage process measurement results show that the sweet sorghum polyphenols treatment can make part of the strain in the process of cold fresh meat in storage at the early stage of the storage has been a strong inhibitory effect,while at the beginning of the storage period,the experimental group and control group bacteria diversity index are similar,But at the end of storage,the abundance of the experimental group was significantly lower than that of the control group.From the level of microbiological phyla,the blank control group mainly changed from proteobacteria to bacteroidetes and other dominant phyla,but the experimental group changed from proteobacteria to firmicutes in a single direction.However,at this time,the pathogenic and deciduous bacteria accounted for a high proportion in the control group.At the level of microbiological species,pathogenic bacteria and aromatic bacteria were the dominant bacteria in the control group at the end of storage,as well as a large number of other miscellaneous bacteria.In the experimental group,lactobacillus or Lactococcus were the dominant species at the end of storage.Analysis of KEGG metabolic pathway annotation abundance and function prediction heat map showed that bacterial life activities in the control group and experimental group changed significantly during the whole storage process.In conclusion,sweet sorghum residue,is rich in phenolic compounds,and the polyphenols extracted from sweet sorghum have strong antioxidant capacity.It has good antibacterial performance against foodborne pathogenic bacteria.The treatment of sweet sorghum polyphenols significantly improved the quality of beef during storage,and inhibited the oxidation of protein and lipid in beef during storage.At the same time,sweet sorghum polyphenols also reduced the species and number of microorganisms during storage,thus prolonging the storage period of beef.