Effects of Different Pretreatment Methods on the Nutrition and Quality Properties of Freeze Dried Asp aragus Off icinalis

ZHU Yunlan; SHANG Xuebing; CHEN Anhui; CHEN Hongwei; WANG Tao; SHAO Ying; CUI Jiaqi

Abstract：Using Asparagus off icinalis as the research material,two methods of blanching and salt so-lution immersion were studied by single factor experiment with freeze-drying time,rehydration,vitamin C, crude protein,total sugar content,microstructure and microbial quantity as indexes effect of nutrient com-position and quality of asparagus on freeze-drying.T he experimental results show that different pretreat-ments have significant effects on the main nutritional components and quality of freeze-dried asparagus, which pretreated with sodium chloride solution is superior to bleaching pretreatment lyophilized samples in color,dehydration,rehydration,Vc,total sugar and protein content.Blanching pretreatment can kill the mi-croorganisms of freeze-dried samples well and reduce the number of microbes significantly.The two pre-treatment methods have no effect on the microstructure of lyophilized samples of asparagus.T he color of asparagus after 3 h of 10% sodium chloride solution treatment was better than that of the control.The soa-king of 5% sodium chloride solution for 5 h could effectively reduce the water content of asparagus after freeze-drying.The water content after freeze-drying was only 1.7%;under the conditions,the rehydration ability of freeze-dried asparagus reached to the best of 602%;NaCl solution soaking has a certain protec-tive effect on Vc of freeze-dried asparagus,5% NaCl solution soak asparagus for 3 h,the Vc content of freeze-dried asparagus was maintained at 45.43 mg/100g;the two different pretreatment methods of salt solution soaking and blanching played a protective role in the loss of total sugar and protein in asparagus. 15% NaCl solution soaked 5 h,the total sugar content was 3.21%,increased by 79% than untreated,its protein content was 2.52%,which was 98.4% higher than that of untreated.The contents of total sugar and protein were similar to those of fresh asparagus.