Submitted to: Russian Polymer Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/15/2010
Publication Date: 5/27/2010
Citation: Muhidinov, Z.K., Avloev, K.K., Biriva, M.T., Nasriddinov, A.S., Khalikov, D.K., Fishman, M. 2010. Effect of temperature on the intrinsic viscosity and conformation of different pectins. Russian Polymer Science. 52(12):1257-1263. Interpretive Summary: The need to increase utilization of low valued co-products derived from the processing of fruit and sunflower seed has prompted us to investigate the effect of temperature on pectin. Pectin is a polysaccharide found in citrus peels, apple pomace and sunflower head casings. In this work we show that the chemical structure of apple pectin is more heat resistant to degradation than citrus or sunflower pectin extracted from fruit or seed grown in Tajikistan. This research, a cooperative project between The International Science and Technology Center, Chemistry Institute of the Tajikistan Academy of Sciences and ARS/USDA should be of help to fruit growers and processors in Tajikistan by increasing the demand and value of their by-products without increasing the cost of the basic commodity to the consumer. Furthermore, the intent of the agreement is to direct the research of Former Soviet Weapons Scientists into non weapon research.
Technical Abstract: The effects of temperature on the intrinsic viscosity and on the conformation of different pectins obtained from citrus, apple and sunflower in a 0.17M NaCl solution were studied. The intrinsic viscosity and the flow activation energy of the polymer (Ea) derived from slope of d In [']/ d(l/T) as an index of stiffness of polymers have been evaluated at various temperature (20-60 deg C). These results showed: the intrinsic viscosities decreased linearly with increasing temperature, for all pectins except apple pectin, therefore, a temperature-induced conformational transition did not occur in the temperature range studied. The results clearly indicate that only apple pectin has sufficient structural integrity to withstand the loss of neutral sugar side chains when subjected to temperatures as high as 60 degrees C. The values of Ea were between 0.67 and 0.69 x 107 J/(kmol) for the commercial citrus and orange pectins and 1.34 and 1.44 x 107 J/(kmol) for the sunflower and apple pectins respectively. Ea increased with decreasing molecular weight, indicating that pectins with low DE have aggregated species, while higher molecular weight pectins are more flexible. Ea data indicate again that all studied pectins are stiff molecules.