Study On The Preparation Of Orange Low Ester Pectin By Different Methods And Quality Analysis

As natural food additive, pectin has the function of thickening, stabilizing and emulsifying. Pectin extracted from plants is mostly high-methoxyl pectin,ordinary low-methoxyl pectin and low-methoxyl amidated pectin could be prepared by the further de-esterification.Low-methoxyl pectin gel is easily formed under low sugar concentration.Because of its thermally reversibility, low-methoxyl amidated pectin is wildly used.However,research on pectin with start,high-methoxyl pectin is the primary form in Chinese marker.In this paper,the optimum conditions of alkali and amidation de-esterification method on citrus peel pectin were explored,with esterification degree and amidation degree as the index.The pectin quality characteristics of two de-esterification methods were compared.The results can provide a theoretical basis for the orange peel comprehensive utilization and pectin products development. The major results were as follows:(1) Study on the technology of alkali de-esterification methodOn the basis of single factor experiment, taking high-methoxyl pectin as the test material, degree of esterification, reaction time, temperature and pH value as the research index, using response surface experimental design to determine the process by alkali de-esterification method. The optimum technological conditions were obtained:the temperature is 14?, reaction time is 41min, the pH value is 10.4. According to the yield of pectin, the conditions for using ethanol precipitation were as follows:ethanol and pectin solution volume ratio of 1.4:1, precipitation time was 35 min, under these conditions, pectin yield was 87.84%, degree of esterification was 33.57%.(2) Study on the technology of amidation de-esterification methodOn the basis of single factor experiment, taking high-methoxyl pectin as the test material, using response surface experimental design to determine the preparation process of amidated low ester pectin by amidation that optimum conditions:69% of the concentration of the ethanol and ammonia added 23 mL/100mL,11? and reaction time was 53 min. At this time degree of amidation was 23.11%, degree of esterification was 38.32%(3) Study on the quality characteristics of low-methoxyl pectin prepared by different methodsThe quality characteristics of pectin obtained by alkali de-esterification method and amide de-esterification method were compared and analyzed, including physical and chemical properties, rheological properties, color difference value and gel texture properties. The results showed that the prepared by alkali de-esterification method of low ester pectin, galacturonic acid, acid insoluble components, dry reduction was more than prepared by amidation pectin, esterification degree is lower than that of low-methoxyl amidated pectin. The L*(brightness) value of low-methoxyl amidated pectin was greater than the low-methoxyl pectin, a* (red/green value), b* (yellow/blue value) was lower than that of ordinary low-methoxyl pectin. By means of the rheological characteristics of determination can be obtained both rheological properties index were less than 1, it showed that the pectin solution was a typical pseudo plastic fluid, and low-methoxyl amidated pectin shear stress is larger than that of an ordinary low-methoxyl pectin. It can be concluded that:under the same pectin concentration, and sucrose concentration, hardness and springiness of low-methoxyl amidated pectin was higher than that of ordinary low ester pectin. The gel properties of low-methoxyl pectin at pH 3.6-4.6 and calcium concentration of 35 to 65 mg/g was better; The gel properties of low-methoxyl amidated pectin at pH 3.2-4.6 and calcium concentration 25?65 mg/g was better.