Study On The Extraction Technology Of Pectin From Walnut Green Husk And Properties

Walnut planting in Xinjiang had more than a thousand years of history.The growth rate of walnut planting area in Xinjiang was 27.76% every year.The planting area was 32.1 thousands hectare in 2013.Based to China Forestry Statistics Yearbook,the total output of Walnut in China was 271 million tons,and the full output of Walnut in Xinjiang was 498 thousands and 900 tons,accounting for 18.38% of the full output of China in 2014.Walnut green husk generated as agricultural and forestry residues in the walnut harvest.There was a huge stock.Except a few green husk was used in drug,most were still treated as garbage and continued to pollute the environment.A large number of researches showed that walnut green husk mainly contain phonemic acids,naphthoquinone and its glycosides,diary heptanes.And it had antibacterial,antioxidant,antitumor and insecticidal activity.Pectin was a hydrophilic colloid whose main components were D-glucose acid and rhamnose,xylose and arabia sugar,galactose,etc.It had good gel,thickening,emulsification and stability,were widely used in food industries.This study took abandoned walnut green husk as raw material to extract pectin,can not only make full use of the resource of walnut green husk,improved the value of walnut industry,reduce environmental pollution,can also be used for the development of high quality pectin resources provide a certain amount of research foundation.The influences of pretreatment methods and the particle size on the yield of pectin were investigated in this paper;Effects of water bath extraction method,ultrasonic assisted extraction,microwave assisted extraction of three kinds of processes on the yield of walnut green husk pectin;The differences of physicochemical properties between three different processes were investigated.The results of the study were as follows:(1)Different extraction methods,drying temperature and drying methods had significant effects on pectin yield.Fresh walnut green husk through natural dried,hot air dried,40?,50?,60?,70? 80? and microwave destroy enzyme then 60? hot dried after 5 min.The highest yield of pectin was 92.88 mg/g,which was under 60? hot air drying condition.The yield of pectin significantly affected by the particle size of dry green husk.The smaller the particle size is,the higher the pectin yield is,and the highest pectin yield is 84.09 mg/g at 80 mesh.(2)Studied the traditional acid extraction,ultrasonic assisted extraction,microwave assisted extraction of three methods on the yield of walnut peel pectin.Water bath extraction factors the best level for: water bath temperature is 77?,water bath time is 1.8h,material liquid than is 25 mL/g,extract pH of 2.And under this condition the pectin yield was 80.77 mg/g;Level of microwave assisted extraction of the best factors: microwave temperature56 ?,microwave power 540 W,extract pH 3.5,microwave time15 min,liquid pH 3,liquid ratio of 30 mL/g.And under this condition,the pectin yield was89.94 mg/g;Optimum process conditions of ultrasonic assisted extraction of walnut green husk pectin is:ultrasonic temperature was 80?,the ultrasonic time for 20 min,liquid pH 2.61,ultrasonic power was 70%,ultrasonic liquid ratio was 25 mL/g.And under this condition the pectin yield was 99.78 mg/g.From this point of view,ultrasonic assisted extraction of pectin had the highest yield.(3)The physical and chemical properties properties of pectin from different process products were different.This experiment studied the three extraction methods of pectin desertification degree,acid insoluble in finished products,pH,water content,ash content,solubility,viscosity measurement,fourier transform infrared spectroscopy,scanning electron microscope etc.The results showed that water bath extraction,ultrasonic assisted extraction,microwave assisted extraction of pectin products desertification degree were respectively: 69.79±0.88%,59.06±0.63%,56.98±0.04%;And the acid insoluble were respectively: 0.55±0.01%,0.24±0.04%,0.35±0.04%;The results of ash contents were respectively: 2.4±0.42%,4.35±0.21%,2.95±0.07%;The results of solubility among three products were respectively: 88.5±0.71%,81.75±1.77%,77.75±0.35%;The pH were respectively: 2.47±0.06%,2.70±0.02%,2.91±0.11%;Drying decrement were respectively: 8.08±0.21%,7.37±0.11%,7.83±0.05%.