Optimizing Study On Alkali Treatment And Cleaning Technology In Producing Gracilaria Agar

Agar is an important polysaccharide product,and the main raw material for producing agar in China is Gracilaria.Alkali consumption and water consumption during the extraction process of Gracilaria agar are important factors affecting the production cost of agar and causing environmental pollution.In this paper,the water consumption and alkali consumption in the extraction process of Gracilaria agar were studied.The feasibility of water saving in different cleaning methods was investigated.The relationship between alkali consumption and agar quality in the treatment of Gracilaria agar base was investigated.The main results were obtained.as follows:(1)The alkali treatment process of Gracilaria agar production was studied.It was found that the gel strength,transparency and 3,6-anhydrogalactose content of agar increased with the increase of the concentration,temperature and treatment time of alkali.The gelatinization rate showed a slight decrease after the first increase,and the sulfate content showed a trend of decreasing first and then tended to be flat.Comparing the alkali consumption under different conditions,it came out that the alkali consumption reached a lowest point under the condition of alkali treatment concentration 7%,treatment temperature 90℃,treatment time 0.5 h,when the agar quality reached a high gel strength standard,which can reduce the alkali consumption by about 0.67 g/g compared with the original process.(2)By studying the first-stage cleaning process of the alkali treatment in Gracilaria agar extraction,the water consumption was determined to be 7.5 mL/g.With the increase of reusing time of washing water,the transparency of the agar decreased continuously while the turbidity,sulfate and 3,6-anhydrogalactose content keep rising.And the gel strength,solidification temperature and melting temperature increased first and then decreased.When the reusing time of washing water was less than 3,there was no significant effect on the quality of the agar.And it can save 0.1 L/g of water approximately compared to the original process.(3)Optimizing the second to fourth stage cleaning process in the production process of Gracilaria agar,and determine the amount of cleaning water of the second to fourth stage is 15 mL/g,and the single-stage countercurrent flow of the cleaning water can save 0.08 L/g water approximately compared with the original process,and the multi-stage countercurrent circulation can save water by about 0.16 L/g compared to the original process.Compared with the traditional process,the two optimized processes can significantly reduce the amount of fresh water without affecting the quality of the agar.In this paper,we researched the alkali treatment and cleaning technology of the producing process of Gracilaria agar.We significantly decreased the assumption of alkali and water,which provided a reference for the realization of clean green production of Gracilaria agar.