Dudsadee Uttapap

Pervaporation separation of ethyl butyrate and isopropanol with polyether block amide (PEBA) membranes

Abstract Polyether block amide (PEBA) membranes were prepared by the solution casting technique. The membranes were investigated for the pervaporation separation of isopropanol–water and ethyl butyrate–water mixtures. The effects of feed concentration and temperature on the separation performance of the membranes were studied. The overall performance of pervaporation separation was evaluated in term of the pervaporation separation index (PSI), which is a composite parameter combining permeation flux and separation factor. It was shown that under the same operating conditions, the pervaporation separation of aqueous ethyl butyrate solution was more efficient than the separation of aqueous isopropanol solutions. It was observed that both permeation flux and separation factor increased with an increase in feed ethyl butyrate content, while an increase in temperature resulted in an increase in permeation flux and a reduction in separation factor.

A comparative study of edible canna (Canna edulis) starch from different cultivars. Part I. Chemical composition and physicochemical properties

Abstract The chemical composition and physicochemical properties of starches isolated from three cultivars (Japanese-green, Thai-green and Thai-purple) of edible canna rhizomes were studied. Scanning electron microscopy investigations showed that the starch granules from all cultivars of canna were oval-shaped granules with smooth surfaces and were around 10–100 μm in sizes. Proximate composition studies showed that the protein content in the canna samples varied between 0.069 and 0.078%, lipid between 0.014 and 0.019% and ash between 0.25 and 0.33%. All canna starches contained considerably high phosphorus (371–399 ppm), followed by calcium (113–154 ppm) and potassium (35–61 ppm). The absolute amylose content ranged from 19 to 25%. All three starches displayed a B-type X-ray diffraction pattern. The viscograms of canna starches determined by Rapid Visco Analyzer showed that Thai-green and Japanese-green starches paste were quite stable during cooking and had high setback. The enthalpy for gelatinization and dissociation of retrograded canna starches, investigated using differential scanning calorimeter, were 17.6–18.4 and 12.3–15.0 J/g of starch, respectively. The results obtained from freeze-thaw stability and light transmittance measurements indicated that all canna starches had a high tendency for retrogradation.

Rice starch vs. rice flour: Differences in their properties when modified by heat–moisture treatment

Starch and flour from the same rice grain source (with 20, 25 and 30% moisture content) were exposed to heat-moisture treatment (HMT) at 100 °C for 16 h in order to investigate whether there were differences in their susceptibility to modification by HMT and, if any, to determine the main causes of the differences. HMT had a far greater effect on paste viscosity of flour than of starch. A significant increase in paste viscosity after removal of proteins from HMT flour - as well as images of fast green-stained HMT flour gels - indicated that an important role was played by proteins in affecting properties of the modified samples. Greater effects of HMT on thermal parameters of gelatinization and gel hardness values of flours were observed - more so than those for starches. Following this observation, it was ascertained that components in rice flour other than rice starch granules also underwent alterations during HMT.

Separation of aroma compounds from aqueous solutions by pervaporation using polyoctylmethyl siloxane (POMS) and polydimethyl siloxane (PDMS) membranes

Abstract Pervaporation separation was used to recover aroma compounds from ethyl butanoate (ETB)–H 2 O, ethyl hexanoate (ETH)–H 2 O mixtures, and ETB–ETH–H 2 O mixtures using polyoctylmethyl siloxane (POMS) and polydimethyl siloxane (PDMS) membranes. The effects of operating conditions (e.g., downstream pressure, feed concentration, feed flow rate, and temperature) on the separation performance were investigated. It was shown that decreasing downstream pressure increased both permeation flux and separation factor, while an increase in feed aroma concentration and/or temperature would increase water flux more significantly than the aroma compound flux, resulting in a decrease in the separation factor. In general, the POMS membrane was more permselective to the aroma compound than the PDMS membrane, and the membrane was more efficient for separation of ETH than for ETB. When both model aroma compounds were present in the feed solution, there was a strong interaction between the two permeating components and the permeation of one aroma compound was affected by the presence of the other aroma compound. It was also shown that under the operating conditions tested, both concentration polarization and temperature polarization occurred. The feed flow hydrodynamic conditions should be controlled appropriately to reduce the boundary layer effect in order to improve the process efficiency.

Self-forming dynamic membrane for ultrafiltration of pineapple juice

Abstract The formation of self-forming dynamic membrane on a porous ceramic support was studied. Pineapple juice of 12° Brix concentration was used in the experiments which were carried out at 25°C by circulating the pineapple juice at the applied pressure of 100, 200, and 300 kPa and at cross-flow velocities of 1.30–2.95 m s −1 through the ceramic membrane module for 1 h. The experimental data of flux and rejections showed that the dynamic membrane was well-formed after 30 min of circulation under the applied pressure of 300 kPa and at a cross-flow velocity of 2.0 m s −1 in which the steady values of flux and rejections of macromolecules and sugars obtained from the filtration mode were 6.0×10 −3 m 3 /m 2 h, 84–87% and 6%, respectively. The corresponding values for ultrafiltration by alumina membrane of MW cut-off 50,000, using equivalent conditions, were 15.8×10 −3 m 3 /m 2 h, 91% and 10.5%. Ultrafiltration was found to be more promising. The stability of the self-forming dynamic membrane was acceptable when subjected to change of filtration conditions. The permeation flux increased with cross-flow velocity and decreased when the applied pressure was reduced. The resistances for filtration by dynamic membrane and by ultrafiltration were calculated. For a porous support of large pore sizes, an in-pore blockage of solutes which were smaller than the membrane pores reduced the pore volume and induced fouling. Internal fouling resistance ( R f ) was, therefore significant and responsible for the values of flux and rejection and was approximately 70% of total resistance. While in ultrafiltration, in which membrane with a smaller pore diameter was used, R f was only 20% but R p , the polarized layer resistance, was as high as 60% of total resistance.

Pervaporation separation and mass transport of ethylbutanoate solution by polyether block amide (PEBA) membranes

Dense and composite membranes were developed from polyether block amide (PEBA). Polyacrylonitrile (PAN) and polysulfone (PSf) were used as the porous supports for the composite membranes. The membranes were tested for pervaporation separation of ethylbutanoate (ETB) solutions. Sorption and desorption experiments were also performed to provide data for analysis of mass transport based on resistance-in-series model. The composite membranes with polyether block amide (PEBA) casted on PSf (PEBA/PSf) showed superior pervaporation performance than that casted on PAN (PEBA/PAN). The analysis of transport resistances revealed that: (1) the resistances in liquid boundary of ETB were highest and, therefore, were the controlling resistances; and (2) the transport resistances in the porous supports were much lower than those in the membrane top layers. The results on plasticizing coefficients showed that ETB plasticized the membranes (positive, kii) but water did not (negative, kjj). Negative coupling coefficients (kij) indicated that water reduced diffusivity of ETB in the membranes and the presence of ETB enhanced water diffusion in the membranes due to positive kji.

Crossflow microfiltration of a colloidal suspension with the presence of macromolecules

Crossflow microfiltration of a colloidal suspension of bentonite with the presence of macromolecules of BSA, dextran and PEG was studied. The plate and frame tangential flow module with the hydrophilic PVDF membrane of nominal pore size of 0.2 μm was used in the experiments which were carried out at constant temperature and flow rate. The results presented are the permeation flux, solute rejection and flow resistances. The constant pressure filtration models were also applied to explain the blocking process. The macromolecules decreased the permeation flux of a bentonite suspension while their rejections were enhanced with presence of bentonite. An increase of flow resistance of a bentonite suspension with BSA was due to internal fouling. For dextran and PEG, external fouling resulted from concentration polarisation and deposition on the membrane surface was an important factor for flux decline. The blocking process of a suspension of bentonite followed the cake filtration model (CFM). The presence of macromolecules affected the blocking process of a suspension of bentonite and the experimental data conformed with CFM and/or incomplete blocking model (IBM).

Nano-structure of heat–moisture treated waxy and normal starches

Surface regions of untreated and heat-moisture treated (HMT) normal rice, waxy rice, normal corn, waxy corn, normal potato, and waxy potato starch granules were examined by atomic force microscopy (AFM). AFM images revealed surface roughness of untreated starch granules and protrusions with a diameter of approximately 15-90 nm. After treatment, the smooth surface region on starch granules was observed, especially in normal rice, waxy rice, and normal corn starches. A significant reduction in the size of protrusions on the surface of HMT potato starch granules was also detected. The newly formed structures may act as barriers and retard water penetration into starch granules. The blocklet model of starch granule architecture was also confirmed by the AFM images.

Anaerobic digestion of pineapple pulp and peel in a plug-flow reactor.

The objective of this research was to study the production of biogas by using pineapple pulp and peel, the by-products from fruit processing plants, in a plug-flow reactor (17.5 L total volume). The effects of feed concentration, total solids (TS) and hydraulic retention time (HRT) on degradation of the waste were investigated. The increase of pineapple pulp and peel of 2% (wt/vol) at HRT 7 d to 4% (wt/vol) at HRT 10 d showed increases in biogas production rate, biogas yield and methane yield - from 0.12 v/v-d, 0.26 m(3)/kg COD removed and 0.11 m(3)/kg COD removed, with COD removal at 64.1%, to 0.25 v/v-d, 0.43 m(3)/kg COD removed and 0.14 m(3)/kg COD removed, with COD removal at 60.41%. The methanogenic fermentation was more active in the middle and final parts of the reactor. The recirculation of fermentation effluent at 40% (vol/vol) of the working volume into the reactor could increase the biogas production rate and biogas yield up to 52% and 12%, respectively. The results showed technological potential for waste treatment of pineapple pulp and peel in a plug-flow reactor.

Quality assessment of noodles made from blends of rice flour and canna starch.

Canna starch and its derivatives (retrograded, retrograded debranched, and cross-linked) were evaluated for their suitability to be used as prebiotic sources in a rice noodle product. Twenty percent of the rice flour was replaced with these tested starches, and the noodles obtained were analyzed for morphology, cooking qualities, textural properties, and capability of producing short-chain fatty acids (SCFAs). Cross-linked canna starch could increase tensile strength and elongation of rice noodles. Total dietary fiber (TDF) content of noodles made from rice flour was 3.0% and increased to 5.1% and 7.3% when rice flour was replaced with retrograded and retrograded debranched starches, respectively. Cooking qualities and textural properties of noodles containing 20% retrograded debranched starch were mostly comparable, while the capability of producing SCFAs and butyric acid was superior to the control rice noodles; the cooked noodle strips also showed fewer tendencies to stick together.