Studies on the jellying propertiesof Ficus awkeotsangMakino achenes and the qualities of Awkeo-jelly

• Main Authors: Bor-Hon,Lee, 李柏宏
• Other Authors: Min-Hsiung Lee
• Format: Others
• Language: zh-TW
• Published: 2000
• Online Access: http://ndltd.ncl.edu.tw/handle/80271745400001463871

博士 === 國立臺灣大學 === 農業化學研究所 === 88 === Summary Jelly fig(Ficus awkeotsang Makino) achenes were extracted with distilled water (1:40, w/v) for 3 hr or with 4% NaCl solution (1:40, w/v) for 140 hr at cold room and room temperature, respectively. During the extraction processes, samples were taken and filtered,and the filtrates were measured for pH, pectin concentraction, degree of esterification (DE) and molecular weight of pectin, solid concentraction, viscosity, and the activities of pectinesterase (PE) ,and polygalacturonase (PG) , while the filtered residues were scanned with SEM for the appearance of jelly fig achenes . For rapid evaluation of jelly fig quality, the measurements of maximum jellying fold and PE activity were recommended. mixer for 15 min. The maximum jellying fold was defined as the highest ratio of water added to the tube that was able to form a gel not collapsing when the tube was laid flat. Rapid determination of PE activity was conducted by using a mixed pH indicator (methyl red :bromothymol blue=3:1) method . The higher the PE activity , the faster the color change happens. The PE activity of the sample can be evaluated grossly according to the time of color change and the color intensity developed . For quality classification of jelly fig , maximum jellying fold，cold water-soluble pectin(CWP) content and PE activity of the achenes were suggested to be determined, and then calculate the gel forming ability(GFA) = PE (U/g)/CWP (mg/g). Jelly fig samples should meet certain requirements set for maximum jellying fold and GFA value to be classified into a certain class. Factors affecting awkeo-jelly’s quality include PE(pectinesterase), PG(polygalacturonase) and PAL(pectate lyase)activities, the content of pectin, molecular weight , DE(degree of esterification)，as well as the activity of PE inhibitor. Among them, PE activity was recognized the most important factor in this study. Awkeo-jelly containing different concentrations of pectin were used for sensory evaluation. It seems that consumers favored the jelly with higher hardness, brittleness, elasticity and chewiness, while no apparent fondness was observed for the color according to statistical analysis. To distinguish imitative awkeo-jelly from true one, the residual PE in the jelly was firstly measured by using pH-stat or mixed indicator (methyl red : methylene blue=8:2)method. If PE activity exists, it must be a true one. When no PE activity was detected，the jelly should be tested by heating-cooling treatment. If the jelly melts when heated and re-jelled when cooled, it must be an imitative one made of other polysaccharides. If the jelly showed no change when heated，it is suggested to test by ruthenium red binding and m-hydroxydiphenyl colorimetric methods in order to distinguish whether the jelly is made of pectin or not . If the jelly does not bind with ruthenium red，it must be an imitative one. If rethenium red test is positive(probably caused by acidic polysaccharides), then it is needed to determine further by m-hydroxydiphenyl colorimetric method . If the jelly gave a positive result in rethenium red test but is low absorbance by m-hydroxydiphenyl test, the jelly must be an imitative one too. Water had more efficiency than NaCl solution for the extraction of PE inhibitor (PEI) from jelly fig achenes. As NaCl concentration increases, PEI concentration in the extract decreases gradually. Therefore hydrophobic interaction was suggested to be the main force of PEI adsorption to the achenes . A pectin extractor modified from a laundry machine, after 13-min operation exhibited a pectin extracting ability equivalent to more then 90% of that of 15-min hand-washing , suggesting the feasibility of using the modified-laundry machine to replace hand-washing process in mass production of awkeo-jelly.