Study On The Properties Of Yam Mucilage And Its Enzymatic Processing For Powder

Yam has been well received people’s attention because of its higher nutritional andmedicinal value. Owning to its high viscosity, the mucilage is not conducive to the processing.The yam mucilage containing biological activities is often abandoned, resulting a waste ofresources. It is necessary for the detailed discussion of yam mucilage. In this paper, thecomposition and properties of yam mucilage were studied, and an enzymatic process ofreducing viscosity for lowering the drying cost was explored. This study provides a newdirection for the comprehensive utilization of yam. The main research contents are as follows:Firstly, the chemical composition of Iron rod yam and Common yam was determinedanalyzed. The moisture content of Iron rod yam and Common yam were70.3%and89.6%,respectively. The mucilage yield of common yam was as1.45times as iron rod yam, and themucilage mainly contained sugar and proteins. Mucilage crude polysaccharide was isolated toobtain the components of a neutral sugar (MP-1) and two acidic sugar components (MP-2,MP-3), the average molecular weight (Mw) of which were1.89105Da,3.73105Da,4.33104Da according to HPLC results. FT-IR spectra showed that, MP-1and MP-2contained β-type pyranose, and MP-3contained α-D-galactopyranose. Gas chromatographicindicated the mucilage polysaccharides were mainly made up of glucose and mannose.Secondly, the rheological properties of yam mucilage under different conditions wereexplored. The results showed that, with increasing concentration, the mucilage viscosity,storage modulus G’ and loss modulus G’’ all increased. But decreased with the increasing ofion concentration, and the Ca2+had more obvious effect than Na+, but an upward trendappeared after0.06mol/L. At pH4, the viscosity decreased to17.64mPa·s, but at pH8, theviscosity received maximum. The viscosity and antioxidant activity were significantlydecreased after heating treatment, and the extending treatment time increased its decline.Then, the enzymatic process aiming to reduce yam mucilage viscosity was studied. At itsoptimum condition (the enzyme ratio of Cellulase:Mannase2:1, enzyme amount:0.6%,reaction time:90min), there were a significant reduction by64.81%in the viscosity. Andafter3times concentrated, the viscosity of hydrolysis mucilage (62.92mPa·s) was lower thanthat of untreated (164.72mPa·s).Finally, the drying process of enzymatic yam mucilage was observed. The resultsshowed that the best drying condition was materials temperature40℃, soluble solids contentof20%, inlet temperature140℃and peristaltic pump speed10r/min. The color was milkywhite and solubility of the mucilage powder was84.41%.