Biological Deodorization,Polysaccharide Extraction And Antioxidant Application Of Kelp

Kelp is the most abundant macroalgae with the same source of medicine and food in my country’s marine resources.It is widely favored by people because of its fast growth rate,high bioremediation potential and large market demand.Kelp contains some aldehydes,alcohols,ketones and other substances,which become the source of its special fishy smell,which restricts the consumption of kelp and hinders the development of kelp in the food industry.Kelp contains a lot of polysaccharides with many biological activities,such as anti-diabetic,anti-inflammatory,antioxidant,etc.Therefore,in this paper,the kelp was used as the experimental raw material,and the fishy smell was removed by the biological fermentation deodorization method,and the main source of the fishy smell was analyzed,through the extraction and separation of kelp polysaccharide,the characterization of physicochemical properties and the determination of antioxidant activity in vitro,to explore its effect as a new natural antioxidant on food oxidative deterioration.Firstly,the deodorization process of common angel yeast,Saccharomyces cerevisiae,HSCC-LP121 Lactobacillus plantarum and HSCC-ST021 Streptococcus thermophilus was optimized by response surface experiment,and the kelp that has been deodorized by the optimal process of each strain,combined with its sensory indicators and electronic nose detection results,determined that the best strain of kelp to deodorize was HSCC-LP121 Lactobacillus plantarum,and the best deodorizing process conditions were:fermentation time 85 min,fermentation temperature 39℃,inoculum amount 4.5%,under this condition,the kelp pulp is blue-green with a special aroma produced by the fermentation of Lactobacillus plantarum.After the kelp was fermented and deodorized,a total of 64 main volatile substances were detected by GC-MS,including alcohols(8 types),aldehydes(13 types),ketones(10 types),acids(6 types),Esters(8types),other types(19 types).Among them,1-octen-3-ol,hexanal,2-octenal and 1-octen-3-one contribute more to the fishy smell of kelp,and the removal rate after fermentation and deodorization can reach 50.21%,57.82%,41.32%and 60.73%,respectively.At the same time,2-octanone,β-ionone,1-octanol and other substances are produced by fermentation,so that the kelp has a unique fragrance after being fermented and deodorized.Secondly,the extraction process of kelp crude polysaccharide was optimized by orthogonal experiments.The optimal process parameters were:ultrasonic power 420 W,ultrasonic temperature 60℃,ultrasonic time 90 min,solid-liquid ratio 1:5,enzymatic hydrolysis temperature 60℃,enzymatic hydrolysis time 2 h,the amount of enzyme added was1.5%,and the actual polysaccharide yield was 16.94±0.11%under this condition.Four kelp polysaccharides were obtained by ethanol fractionation and precipitation:KP-20,KP-40,KP-60 and KP-80.Through the characterization of physical and chemical properties of the KPs and the analysis of antioxidant activity in vitro,it was found that the four components were different in chemical composition,molecular weight,monosaccharide composition and microscopic morphology.The results of chemical composition analysis showed that the total sugar content of the KPs was between 71.91%～81.29%,and the content of nucleic acid and protein in the KPs was low.The weight-average molecular weights of KPs were 2894.7,3016.6,1228.3 and47.6 k Da.The four components all have the characteristic functional groups of polysaccharides and the unique fucose of seaweed.Among them,KP-40 has the highest fucose content,accounting for 53.03%of its monosaccharide composition,which is also the most effective in scavenging DPPH free radicals and ABTS free radicals.The results of in vitro antioxidant experiments showed that when the concentration of each polysaccharide component was 5.0mg/m L,the three components KP-20,KP-40 and KP-80 had the same ability to scavenge hydroxyl radicals as the positive control,up to 95%.Above,the overall results showed that the four kelp polysaccharides had different antioxidant activities in vitro,and KP-40 was the polysaccharide fraction with the strongest antioxidant activity among the KPs obtained by fractional alcohol precipitation.Finally,the peroxide value,acid value,P-anisidine and malondialdehyde added with different contents of KP-40 oil were determined by Schaal,it was found that the degree of oxidative rancidity of oils and fats rich in saturated fatty acid(SFA),monounsaturated fatty acid(MUFA)and polyunsaturated fatty acid(PUFA)decreased with the increase of KP-40 addition and there was a dose-dependent effect of each oil on KP-40.By analyzing the changes of four indicators during oil storage,it can be concluded that the antioxidant effect of KP-40components in the four types of oils is sesame oil(rich inω-6 PUFA)>olive oil(MUFA)>flaxseed oil(rich inω-3 PUFA)>lard(rich in SFA).The optimal ratio of new natural antioxidants optimized by orthogonal experiment is:adding 0.06%V_E,0.01%V_C and 3.2%KP-40,among which,the addition amount of KP-40 has the greatest influence on the antioxidant effect.It was applied to foods containing more oil,and it was found that adding it in the production process of duck neck(animal food)and adding it on the surface of twist(plant food)had the best antioxidant effect,which degree of inhibiting the oxidation of duck neck and twist was 1.16 times and 1.44 times that of the positive control.