Preparation and physicochemical properties of modified jackfruit starches

Modifications of jackfruit starch, extracted from the cotyledons of Artocarpus heterophyllus Lam. (Thong Prasert cultivar), were carried out to obtain a pregelatinized starch, three (m-, n- and i-) carboxymethyl starches, a hydroxypropyl starch and a phosphate cross-linked starch. Physicochemical properties of native and modified jackfruit starches were comparatively investigated. Pregelatinized, hydroxypropyl, and cross-linked starches were insoluble or partially soluble in water at room temperature, while carboxymethyl starches were soluble with good overall water uptake. Scanning electron microscopic images revealed that granules of most modified jackfruit starches retained the native appearance and crystal structure, with the exception of pregelatinized starch and two (n- and i-) carboxymethyl starches, which showed significant breakage of granules. X-ray diffraction patterns corroborated to suggest the loss of crystallinity in these modified starches. Thermal analysis showed a significant decrease in the gelatinization temperature of hydroxypropyl starch with no change in enthalpy, while higher gelatinization temperature and less enthalpic value were observed for pregelatinized starch. Pregelatinized and hydroxypropyl starches showed temperature-dependent improvement on swelling and solubility, while cross-linked starch exhibited less solubility. Aqueous solution of m-carboxymethyl starch yielded the highest apparent viscosity with improved heating-cooling stability.     

Development of Cross-Flow Fluidized Bed Paddy Dryer

A cross-flow fluidized bed paddy dryer with a capacily of 200 kgh was designed, fabricated and tested. Experimental results showed that final moisture content of paddy should not be lower than 23 % dry-basis if quality is to be maintained. Drying air temperature was keot constant at 115°C according to the recommendation of previous work. Results obtained from the mathematical model developed in this study indicatedthat optimum operating parameters should be as follows : air speed of 2.3 m/s, bed thickness of 10 cm and fraction of air recycled of 80 %. At this condition, energy consumption was close to the minimum while drying capacity was near the maximum. A prototype fluidized bed dryer with a capacity of 1 t/h was designed, fabricated and installed with the collaboration of a private company. The unit has been used for almost the whole past harvesting season in 1994 at a paddy merchant sile with preference compared to conventional column continuous dryers. More than 300 tons of paddy were dried without any problems.     

Development of Cross-Flow Fluidized Bed Paddy Dryer

ABSTRACT

A cross-flow fluidized bed paddy dryer with a capacily of 200 kgh was designed, fabricated and tested. Experimental results showed that final moisture content of paddy should not be lower than 23 % dry-basis if quality is to be maintained. Drying air temperature was keot constant at 115°C according to the recommendation of previous work. Results obtained from the mathematical model developed in this study indicatedthat optimum operating parameters should be as follows : air speed of 2.3 m/s, bed thickness of 10 cm and fraction of air recycled of 80 %. At this condition, energy consumption was close to the minimum while drying capacity was near the maximum. A prototype fluidized bed dryer with a capacity of 1 t/h was designed, fabricated and installed with the collaboration of a private company. The unit has been used for almost the whole past harvesting season in 1994 at a paddy merchant sile with preference compared to conventional column continuous dryers. More than 300 tons of paddy were dried without any problems.     

Carboxymethyl Mungbean Starch as a New Pharmaceutical Gelling Agent for Topical Preparation

An application of carboxymethyl mungbean starch (CMMS) as a gelling agent in the topical pharmaceutical preparation was investigated. CMMS was prepared using specific conditions that yielded a high-viscosity product. Polymer gels and gel bases were prepared at 1–10% (wt/wt), and physicochemical studies were carried out in comparison with four standard gelling agents: carbopol 940 (CP), hydroxypropylmethyl cellulose (HPMC), methyl cellulose (MC), and sodium carboxymethyl cellulose (SCMC). Piroxicam was used as a model drug to study the drug release profile of the gel formulations. The tackless, greaseless, and transparent CMMS gels exhibited pseudoplastic behavior with thixotropy at concentrations less than 5% (wt/wt). At a concentration of 5% (wt/wt) and higher, the semisolid gels showed plastic flow characteristics. Viscosity and X-ray diffraction results indicated a good compatibility between CMMS and the acidic piroxicam. No precipitation of piroxicam or phase separation was observed during a stability test. The release rate of piroxicam from 3% (wt/wt) CMMS gel was 1,003.79 ± 105.08 μg/cm², which was comparable with 947.66 ± 133.70 μg/cm² obtained from a 0.5% (wt/wt) carbopol formulation. The release profiles of both formulations were consistent and remained unchanged after 2 months' storage. Viscosity played an important role in controlling the release rate of low concentration CMMS formulations by regulating the drug diffusion. At a concentration of 5% (wt/wt) CMMS and higher, the release rates of piroxicam were not significantly different. A plausible explanation based on the nature of the gelling agent was proposed. Stability and drug release profiles of CMMS and commercial gelling agents were compared. The results supported the potential use of CMMS as a new, effective gelling agent for topical gel preparation.     

Physicochemical, in vitro digestibility and functional properties of carboxymethyl rice starch cross-linked with epichlorohydrin

Cross-linked carboxymethyl rice starches (CL-CMRSs) were prepared from reactions between native rice starch and varied concentrations (0.1–15% w/w, M-0.1 to M-15) of epichlorohydrin (ECH) in a simultaneous carboxymethylation-crosslinking reaction setup using methanol as the solvent. The degree of carboxymethyl substitution was between 0.24 and 0.28, while apparent amylose contents were lowered due to modification. SEM images showed minor change on the granule surface, while XRD profiles indicated slight loss of crystallinity. DSC thermograms revealed no transition peak in all treated samples. The water uptake (WU), swelling volume (SV) and free swelling capacity (FSC) of CL-CMRSs increased significantly as a result of the modification, while swelling of CMRSs cross-linked with 2% (M-2) and 3% (M-3) ECH yielded FSC values and WU values that were much greater than those of native starches and were comparable to that of Explotab®. All modified starch samples showed increased amount of rapidly digestible starch (RDS), while cross-linking with 5–7.5% ECH raised the resistant starch (RS) content, compared to native starch. M-2 also showed promising results in tablet disintegration test. ECH–CL–CMRSs could potentially be used as an excipient in pharmaceutical and food/food supplement products.     

Carboxymethyl mungbean starch as a new pharmaceutical gelling agent for topical preparation

An application of carboxymethyl mungbean starch (CMMS) as a gelling agent in the topical pharmaceutical preparation was investigated. CMMS was prepared using specific conditions that yielded a high-viscosity product. Polymer gels and gel bases were prepared at 1-10% (wt/wt), and physicochemical studies were carried out in comparison with four standard gelling agents: carbopol 940 (CP), hydroxypropylmethyl cellulose (HPMC), methyl cellulose (MC), and sodium carboxymethyl cellulose (SCMC). Piroxicam was used as a model drug to study the drug release profile of the gel formulations. The tackless, greaseless, and transparent CMMS gels exhibited pseudoplastic behavior with thixotropy at concentrations less than 5% (wt/wt). At a concentration of 5% (wt/wt) and higher, the semisolid gels showed plastic flow characteristics. Viscosity and X-ray diffraction results indicated a good compatibility between CMMS and the acidic piroxicam. No precipitation of piroxicam or phase separation was observed during a stability test. The release rate of piroxicam from 3% (wt/wt) CMMS gel was 1,003.79 +/- 105.08 microg/cm(2), which was comparable with 947.66 +/- 133.70 microg/cm(2) obtained from a 0.5% (wt/wt) carbopol formulation. The release profiles of both formulations were consistent and remained unchanged after 2 months' storage. Viscosity played an important role in controlling the release rate of low concentration CMMS formulations by regulating the drug diffusion. At a concentration of 5% (wt/wt) CMMS and higher, the release rates of piroxicam were not significantly different. A plausible explanation based on the nature of the gelling agent was proposed. Stability and drug release profiles of CMMS and commercial gelling agents were compared. The results supported the potential use of CMMS as a new, effective gelling agent for topical gel preparation.