Separation,Purification,Biological Activity Of Arthrospira Platensis Polysaccharide And Its Application In Preservation Of Meat Products

In the development trend of meat product preservation technology,biological preservation technology has become one of the most important directions for ensuring the quality and safety of meat products and developing the green environmental protection industry.Natural plant preservatives have been widely applied to meat products to improve quality and safety because of their greenness,safety and high-efficiency characteristics.However,most of these natural plant preservatives derived from advanced plants.Due to the relatively limited resources,the large area of occupied farmland,the long growing period and the high cost of planting,its further development and application are limited.Compared with advanced plants,algae,especially microalgae,has the advantages of rapid propagation,less land occupation,easy cultivation,high yield,and low cost.At the same time,microalgae are rich in many active ingredients.Therefore,the development of high-quality,low-cost plant-based preservatives from microalgae has broad prospects for development.The production of Arthrospira platensis is the largest in microalgae resources and it is the most widely consumed.At present,due to the new functions such as antibacterial and antioxidation of packaging materials provided by active packaging,and the characteristics of improving food quality and safety,the development of new products for active packaging has become a research hotspot,mainly using chitosan or chitosan complexes.Although most of the active food packaging films are produced,there are few studies on the microalgal-chitosan composite active films,and the preparation and preservation mechanism of the microalgae-chitosan composite active films need to be strengthened.This thesis summarizes the existing research results in the field of higher plants and algae,especially microalgae Arthrospira platensis.Using Arthrospira platensis as raw material,extraction,purification and structure identification of Arthrospira platensis polysaccharides?APP?were studied.The information of its content,purity and glycosidic bond configuration was obtained.Furthermore,the antioxidant activity of APP and its antimicrobial activity against common pathogens of food were investigated.Based on this,the effect of APP on physicochemical,microbiological,and sensory qualities of Chinese-style sausage samples during refrigerated storage at 4°C were examined,and the preservation mechanism was explored.Finally,the active packaging film?CAP-film?was prepared by combining APP and chitosan.The physicochemical properties and mechanical properties of CAP-film were determined,and its structure and morphology were characterized.Meanwhile,the effect of CAP-film on physical,chemical,microbiological,and sensory qualities of cooked ground pork meat during refrigerated storage at 4°C were examined,and its preservation mechanism was explored.The research ideas of this dissertation focus on the strategic goal of developing the green environmental protection industry in the 13th Five-Year Plan of China and have important significance for improving people's life quality and ensuring food safety.The main findings of this study include:?1?Arthrospira platensis crude polysaccharide?APP?was prepared by reflux extraction.After being separated by DEAE-cellulose 52 column chromatography,APP-I and APP-II were obtained,which accounted for53.02%and 8.13%of APP,respectively;the main component APP-I was further purified by Sephadex G-150 gel column.A single component of APP-III was obtained with a purity of 91.47%.By optical rotation,gel column chromatography,and UV-visible spectral scanning analysis,the specific rotation of APP-III was dextro-circle 57.64°;its molecular weight was 78426 Da,and no protein was present.These results indicated that the purified APP-III is a white crystalline and water soluble acidic polysaccharide with high purity.Analysis of the composition and structure by gas chromatography?GC?and infrared spectroscopy?FTIR?indicated that polysaccharide was mainly composed of rhamitol?21.2%?,followed by nectar Alcohol?10.46%?,fucose?10.01%?,glucose?4.17%?,galactose?2.02%?,xylose?1.14%?,and arabitol?0.47%?,and these monosaccharides existed as?-Pyranose.?2?The antioxidant activity of APP was measured using DPPH radical,hydroxyl radical?·OH?,superoxide anion radical?O₂?^-?and metal Fe²⁺ion system.The results showed that the scavenging capacity of APP on three free radicals was significantly higher than that of Arthrospira platensis extracts?APE??p?0.05?,lower than that of positive control Vc,and the corresponding IC₅₀ of the median inhibitory concentration was 0.20mg·mL^-1,0.26 mg·mL^-1 and 0.43 mg·mL^-1,respectively;The half-chelating concentration CC₅₀0 of APP to Fe²⁺was 0.19 mg·mL^-1,which chelated Fe²⁺significantly higher than APE,but also lower than positive control EDTA-2Na.Antibacterial effects of APP on seven common food-borne pathogens were investigated.The results showed that,in addition to Salmonella,APP had a different degree of inhibition on the growth of the tested bacteria,which can significantly delay the logarithmic growth phase of bacteria and fungi.The order of antimicrobial activity was as follows:Staphylococcus aureus>Bacillus cereus=Escherichia coli=Aspergillus flavus>Listeria monocytogenes>Candida albicans,the corresponding minimum inhibitory concentrations?MIC?were 1.25 mg·mL^-1,1.25mg·mL^-1,2.5 mg·mL^-1,2.5 mg·mL^-1,5.0 mg·mL^-1,10 mg·mL^-1,respectively.?3?The effect of APP at 0.1%,0.25%and 0.5%?wt/wt?of Chinese-style sausages on lipid peroxidation,microbiological and sensory properties during 24 days of refrigerated storage at 4°C were examined.During the storage,pH,L*,DPPH radical scavenging activity and sensory scores decreased with time and thiobarbituric acid-reactive substances?TBARS?,total volatile base nitrogen?TVB-N?,mesophilic?MTVC?and psychrotrophic?PTVC?total viable counts increased.However,the magnitude of the changes was attenuated with the addition of APP as compared to control.Samples containing APP had significantly?p?0.05?higher DPPH radical scavenging activity and lower TBARS values compared with the control,and the antioxidant effect was dose-dependent.The addition of 0.5%APP maintained stable a*values of sausages,although there was no positive effect on the microbiological status.Moreover,the addition of APP prevented the decrease of aroma,flavor and sensory acceptance of samples.The results suggested incorporation of APP could decrease lipid peroxidation and improve eating properties of Chinese-style sausage.?4?In order to explore the possibility of applying APP in green active packaging,APP-chitosan active films were prepared.The effect of APP on the physical properties,mechanical properties,structure and morphology of chitosan films were investigated.The results indicated APP macromolecules can be better dissolved in chitosan matrix and interact with chitosan molecular groups?such as the formation of hydrogen bonds or covalent bonds,etc.?,resulting in cross-links forming a dense structure.The values of density,transparency?O?,water vapor transmission rate?WVP?and swelling ratio?Swe?significantly decreased with the increasing of APP concentration,and the water content?Mc?increased.The properties of tensile strength and elongation at break enhanced?p?0.05?.Infrared spectroscopy?FTIR?and crystal structure?X-ray?analysis indicated that the incorporation of APP caused changes in the structure of chitosan film,formed new bonds with chitosan molecules,and new chemical reactions occurred.APP was well embedded in chitosan films.By the analysis of scanning electron microscopy?SEM?and atomic force microscopy?AFM?,the results showed that the addition of APP resulted in a more compact surface structure of the chitosan film,and the surface was not smooth,increasing the surface roughness.?5?In order to confirm the preservation effect of CAP-film in meat product system,effect of CAP-film on physicochemical,microbiological and sensory properties of cooked ground pork during refrigerated storage at 4°C were investigated.The results showed that CAP-film significantly reduced the increase of the acidity?pH?,thiobarbituric acid?TBARS?,total viable count?TVC?,and psychrophilic bacteria count?TBC?of cooked pork compared to a single chitosan film,effectively improving the odor,taste,texture,and overall acceptability of samples,and extending the shelf life of more than 5 d.CAP-film had no adverse effects on the color?L*,a*,and b*?of cooked ground pork.