Synthesis Of Polysaccharide Derivatives And The Application In Aquatic Product Preservation

Aquatic products are liable to lose water and spoilage during low-temperature storage.In order to effectively slow down the deterioration and maintain the texture characteristics of aquatic products,it is necessary to preserve water and keep them fresh.Traditional water-retaining agents such as sodium pyrophosphate and traditional preservatives such as benzoic acid have certain impacts on the health of consumers,so it is of great significance to develop green and efficient water-retaining agents and preservatives for aquatic products.Natural saccharides,such as konjac glucomannan oligosaccharide(KGO) and chitosan oligosaccharide(COS),have hydrophilic groups such as hydroxyl group,which can form hydrogen bonds with water to effectively maintain water in the muscle tissue of aquatic products,but have low antibacterial or antioxidant activities.By modifying saccharides to enhance their antibacterial or antioxidant activities,and using saccharides derivatives as the main raw materials for compounding to play a synergistic effect,green,new,efficient aquatic product additives with moisture retention and preservation functions are developed.In this paper,konjac glucomannan oligosaccharide and chitosan oligosaccharide were modified respectively,and the derivatives were characterized by TG,XRD,UV-Vis,FTIR and ~1H NMR,and the water-retaining capacity,bacteriostasis,antioxidant activities,and water retention and freshness preservation properties in the aquatic product were determined.The main experimental methods and results are as follows:(1)Through alkylation reaction,kojic acid(KA)is introduced into the molecular chain of konjac glucomannan oligosaccharide to obtain konjac glucomannan oligosaccharide-kojic acid derivative(KGOK).The moisture retention rates of konjac glucomannan oligosaccharide-kojic acid derivative were 292.46%,101.13%,and70.96%respectively under the conditions of 81%RH,43%RH and dry silica gel,indicating that konjac glucomannan oligosaccharide-kojic acid derivative still has excellent moisture retention performance.At the same time,konjac glucomannan oligosaccharide-kojic acid derivative has good antibacterial activity,the minimum inhibitory concentration(MIC)of it to Staphylococcus aureus,Staphylococcus epidermidis,Shewanella putrefaciens,and Salmonella enterica is 2 mg/mL,to Escherichia coli is 3 mg/mL.(2)Maillard reaction products of chitosan oligosaccharide and Nisin were prepared through aqueous-state and solid-state respectively.Through single factor experiments of temperature and time and taking ultraviolet-visible absorption of the products as evaluation criteria,the conditions of the aqueous-state and solid-state reaction were determined,i.e.the solid-state conditions were that chitosan oligosaccharide and Nisin reacted at 90?for 6 h according to the mass ratio of 1:1,and the aqueous-state conditions were that chitosan oligosaccharide with final concentration of 25 mg/mL and Nisin reacted at 90?for 4 h.The efficiency of the Maillard reaction in solid-state is higher than that in aqueous-state,and the products of Maillard reaction in solid-state have better oxidation resistance.Antioxidant experiments were carried out on Maillard products.The results showed that DPPH scavenging rates for 0.25 mg/mL Maillard products of solid-state and aqueous-state were 91.50±2.59%and 81.97±3.62%respectively.The antibacterial activity of solid-state Maillard products was determined.The results showed that Maillard products of chitosan oligosaccharide-Nisin in solid-state have good antibacterial effects on Gram-positive bacteria such as Staphylococcus aureus,Staphylococcus epidermidis and Enterococcus faecalis,with the MIC of 1,1 and 0.5 mg/mL respectively.The antibacterial activities against gram-negative bacteria such as Escherichia coli,Salmonella enterica and Vibrio parahaemolyticus were also increased,with the MIC of 3,4 and 3 mg/mL respectively.(3)In this paper,Penaeus vannamei was used to measure the defrosting loss rate,cooking loss rate and other water retention indexes of konjac glucomannan oligosaccharide-kojic acid derivative,chitosan oligosaccharide-Nisin Maillard products and their mixtures,and the preservation indexes such as volatile base nitrogen,thiobarbituric acid,and the total number of colonies were determined.The experimental results show that konjac glucomannan oligosaccharide-kojic acid derivative and chitosan oligosaccharide-Nisin Maillard products have good water retention and freshness preservation for shrimp,and both have a synergistic effect on water retention and freshness preservation of shrimp.The thawing loss rate and cooking loss rate of shrimps in the compound group decreased to 5.82±0.42%and18.84±0.53%respectively,indicating that the compound group can effectively reduce the water loss rate of shrimps.At 6 d,the content of volatile basic nitrogen decreased from 28 mg/100 g to 14 mg/100 g in the control group,indicating that konjac glucomannan oligosaccharide-kojic acid derivative and chitosan oligosaccharide-Nisin Maillard products can synergistically inhibit protein corruption.Therefore,the konjac glucomannan oligosaccharide-kojic acid derivative and chitosan oligosaccharide-Nisin Maillard products have good application prospects in the preservation of aquatic products.