Rice starch is commonly isolated by alkaline (sodium hydroxide) extraction because this process provides high yield, high purity and is low in capital costs. This process produces an highly loaded alkaline effluent that contributes significantly to general costs of wastewater treatment. The present study attempted to develop an enzymatic procedure to isolate pure rice starch and to investigate the physico‐chemical properties in comparison with that of rice starch produced by an alkaline process of comparable scale. The isolation of starch from polished rice grain was effected by application of cellulase under slightly acidic conditions in order to degrade the cellular tissue, followed by protease (Corolase 7089 or papain) under neutral conditions in order to loosen the protein bodies that are associated with starch granules. In comparison with the alkaline process, the enzyme process provided rice starch with a slightly elevated protein content, but less damaged starch. No differences were found between the two proteases used. Washing the enzyme‐isolated starch with 0.2% sodium hydroxide or 0.5% sodium dodecylsulphate (SDS) solutions further improved the purity of rice starch. The physico‐chemical properties of the enzymatically‐isolated starches were mostly comparable with starch from the alkaline process. The developed process allows to replace the alkaline process and thus eliminates critical levels of mineral load in effluents of rice starch plants.
A total of 7.0 × 10 6 and 7.3 × 10 6 t starch was produced in 1996 and 1997, respectively, in the European Union, consisting of 15 member states [1,2]. The trend of a steadily increasing starch production is obvious. During a long period, potato starch played an important role in covering approximately 25 % of the available shares; the situation changed in 1995 by the decision of the European Commission to limit subsidies connected with the production of potatoes and their utilisation in starch factories. The instrument used to limit costs became a quota system issued to each potato starch producing member country; in fact, 8 of the 15 member states. A maximum potato starch production has been fixed at approximately 1,864 × 10 3 t/a. The main share is covered by four member states: Germany (696.3 × 10 3 t), Netherlands (538.3 × 10 3 t), France (281.5 × 10 3 t) and Denmark (178.5 × 10 3 t). Smaller quotas (49 to 64 × 10 3 ) are held by Sweden, Finland and Austria, while Spain owns a quota of 2,000 t ( Fig. 1) [3]. Recent resolutions, in connection with the development of EU's Agenda 2000 system, resulted in further reduction of starch production limits by 100 × 10 3 t. The relevant decreases in production will be approx. 40 × 10 3 t for Germany and 31 × 10 3 t for The Netherlands as the main potato starch producing countries. As result of these regulations, potatoes will not be used increasingly as substrates of starch production. Maize and wheat will cover future growth, with more important prospects for wheat.Potato starch production encountered drastic changes during the last years, in particular in economics and substrate supply. Because of economically required reductions in subsidisation, production of potato starch will decrease. Changes in technology are characterised by savings in wash water and process water streams that are effected by increased efficiency introduced with new machinery and changed technological concepts. From an ecological point of view, an early and maximum fruit water separation (up to 95 %) based on dilution of gratings with process water and decanter separation allowed to reduce the fresh water supply to 0.4 to 0.5 m 3 /t of processed potatoes. For economical isolation of potato protein a correspondingly high protein recovery rate (up to 90 %) is essential. Concerning starch extraction, a minimum of 95 % is reached in modern potato starch plants, but optimum engineering (rasping, decanting, sieving) gives recovery rates of 97 to 98 %. In starch refinement, three-phase nozzle separators equipped with wash water supply and constructed for efficient displacement washing allow to achieve a fine fibre removal of 98 % within three separation stages and a final concentration of purified starch milk of 22 to 23°Bé. Potato protein isolates (protein content 83 to 85 %) are produced by isoelectric precipitation combined with heat coagulation while stringent solutions for treatment of de-proteinised fruit water are still lacking. * Publication No. 7075 of the Federal Centre for Cereal, Potato a...
Acid modified, agglomerated starches offer specific advantages as fillers in production of pharmaceutical tablets. Spray drying can improve processing of tablet mixtures significantly. In order to investigate prerequisites in utilization of rice starch, non‐waxy and waxy types were partially hydrolyzed in 6% (w/v) HCl solution at room temperature for varied length of time to obtain rice starches with increased crystallinity (so‐called crystalline rice starches). Scanning electron micrographs of native and highly crystalline starches were used to study the morphological changes and to suggest the mode of acid attack during hydrolysis. Exo‐corrosion distributed over the surface of acid‐modified waxy rice starch (AWRS) was observed after 192 h of hydrolysis. In contrast, the surface of acid‐modified rice starch (ARS) remained unchanged at 192 h of acid hydrolysis. The amylose content and the median particle size (diameter) were reduced with increasing hydrolysis time. It was found by X‐ray diffraction that the relative crystallinity of acid‐modified starches at >95% relative humidity was clearly increased with prolonged hydrolysis time.For studying tablet properties spherical agglomerates of the native and acid modified starches were directly compressed at 4 kN to obtain tablets. Crushing strength and disintegration time of tablets increased with relative crystallinity. In contrast, tablet friability was reduced. Concerning tablet functionality, the crystalline starches were positioned in overlapping ranges between the common commercial tablet fillers (microcrystalline cellulose, pregelatinized starch and lactose, respectively).
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