Production of carboxymethylcellulose from sugar beet pulp cellulose and its use in retardation of deterioration of fruit as protective film layer

Sugar-beet pulp is a by-product from the sugar industry, produced annually in large quantities. The lignocellulosic fraction of dried sugar-beet pulp contains 22-30 % cellulose. Cellulose is a polydisperse polymer of high molecular weight comprised of long chains of D-glucose units joined together by P-l,4-glucosidic bonds. ^Water-soluble cellulose derivatives^are a Tdass of^ technically important compounds. Most of them are ionically substituted, e.g. sodium carboxymethyl cellulose which is used a thickener or a flocculating agent in various applications. CMC form complexes and are used in aqueous coating systems. CMC is also used widely in pharmacy, cosmetics, the food industry and coating of fruit surfaces in order to improve the consistency and flow properties. In this study, the effects of several factors such as extraction time, temperature and concentration of alkali on cellulose yield in extraction of cellulose from the sugar- beet pulp were investigated. Magnitudes of intrinsic viscosity, and molecular weight of cellulose obtained from sugar-beet pulp by different extraction conditions were fitted to Mark-Houwink-VI Sakurada equation, which helps evaluate the average molecular weights of cellulose solutions from sugar-beet pulp with a knowledge of their intrinsic viscosity. Effects of temperature and concentration on viscosity of cellulose solutions were examined at six different temperatures between 10 °C and 60 °C and seven different concentration levels. Equations describing the combined effects of temperature and concentration on viscosity were derived. In production of carboxymethylcellulose from cellulose, the process of carboxymethylation was optimised with respect to the solvent medium, alkali concentration, acid concentration, time and temperature of the reaction. The flow behaviour carboxymethylcellulose solutions was determined with a rotational viscometer at a temperature range of 20-30 °C and carboxymethyl cellulose concentrations of 5- 30 kg/m3. The experimental results of the variation of shear stress with shear rate were fitted to the several reological models by non-linear regressions. The flow behaviour of carboxymethyl cellulose solutions having concentrations of 5-30 kg/m3 was pseudoplastic and fitted well to the Ostwald-de Waele model. The expression for the combined effect of temperature and concentration on the apparent viscosity, flow behaviour index and consistency factor was givea The fruits such as peach, apple, pear and tangerine were coated with films formed by spraying the different emulsions containing the carboxymethyl cellulose from sugar-beet pulp cellulose to retard of deterioration of the fruits and to extend their shelf life during storage. Fruits were stored in fruit storage chamber at 25 °C and at a relative humidityof 75 %^Tlre changesof Jhe weight loss, pH» tfrratahle acidify^ total soluble solids and ascorbic acid of the coated samples during storage were periodically investigated in comparison with the uncoated samples to determine the effects of coatings in extending postharvest life of fruits and maintaining their quality. It was found that coating was effective to prolong storage time of fruits, and the film emulsions didn't exhibited similar effects for each fruits. Key Words: Sugar-beet pulp, cellulose, carboxymethyl cellulose, extraction, rheology, fruit coating.