Study On The Preparation And Process Design Of Oxidized Agar

Agar is a hydrophilic colloid extracted from red algae such as Gracilaria.To expand the application scope of agar,it is often modified by chemical or physical methods to alter some of the special properties or to give it a special purpose.In this paper,the preparation and characterization of oxidized agar were studied.The production workshop with 300 tons per year of oxidized agar was designed.Firstly,hydrogen peroxide was used as oxidant and oxidized agar was prepared from raw agar with the index of gel strength.Under the optimized conditons of reaction temperature 80℃,initial pH 5,2 mL of 30%H2O2 addtion,reaction time 4 h,characterization of raw agar and oxidized agar samples are as follows:the gel strength of oxidized agar is 232 g·cm^-2,the gel temperature is 35℃,the melting temperature is 79℃,the gel dissolution temperature is 94℃.The apparent viscosity,the content of 3,6-AG,the sulphate,the transparency decreased of oxidized agar.The whiteness and the ash content increased.The carboxyl group was introduced into the structure.Effects of different cosolvent and spray drying conditions on the gel strength and the dissolution temperature of the sample were investigated.On the basis of single factor,the optimum conditions for the preparation of oxidized agar by spray drying are as follows:using mixture of 1.5%potassium chloride and 20%sucrose（based on the mass of raw agar）as the combined cosolvent.The parameters of spray drying are as follows:the air inlet temperature is 150℃,the flow rate of the fan is 45 m³·h^-1,the peristaltic pump speed is 8 r/min,and the spray pressure is 0.2 MPa.The gel strength of the oxidizing agar spray dried sample added with the cosolvent can reach a value of 137 g·m-2,the gel temperature reduced to 31.5℃,the melting temperature reduced to 31℃,and the solution temperature reduced to 81℃.The transparency and the content of 3,6-AG decreased.The content of galactose and the whiteness increased.The production workshop with 300 tons per year of oxidized agar was designed.The system of three shifts was adopted,and the total number of staff was 13.The main equipment includes stainless steel storage tank,stainless steel reactor,pH automatic dosing machine,spray drying tower and powder quantitative packing machine.The total cost of consuming raw and auxiliary materials is 32.24 million yuan.Workshop investment includes engineering construction and purchase of fixed assets totalling is 2 million yuan.The cost of water and electricity is 3.41 million yuan.Total cost investment is 37.65 million yuan.By estimating the economic benefit of the enterprise,the annual profit can reach 16.346 million yuan.The operating condition of the company is safe through the analysis of the operating safety rate,and the cost can be recovered within 3.3 years.