Effects of particle size and its distribution on specific cake resistance during rice wine microfiltration

The effects of particle size and its distribution on permeate flux and specific cake resistance (α) of rice wine suspensions were determined. Specific cake resistance decreased as the ratio of particles having size larger than 45 μm increased. For rice wine suspensions with particle sizes in the range of 1-20 μm (mean diameter of 5-6 μm), α increased linearly with total suspended solids concentration. The dependence of α on total suspended solids concentration was minimal when particles with size greater than 20 μm were present. Specific cake resistance was independent of total suspended solids concentration when rice wine suspensions contained greater than 50% by weight of particles having size larger than 45 μm.     

Interfacial and emulsifying properties of sucrose ester in coconut milk emulsions in comparison with Tween

In this study, sucrose esters were presented as a promising alternative to petrochemically synthesized Tweens for application in coconut milk emulsions. The interfacial and emulsifier properties of sucrose ester (SE), mainly sucrose monostearate, had been investigated in comparison with Tween 60 (TW), an ethoxylate surfactant. The interfacial tension measurement showed that SE had a slightly better ability to lower the interfacial tension at coconut oil–water interface. These surfactants (0.25 wt%) were applied in coconut milk emulsions with 5 wt% fat content. The effects of changes in pH, salt concentration, and temperature on emulsion stability were analyzed from visual appearance, optical micrograph, droplet charges, particle size distributions, and creaming index. Oil droplets in both SE and TW coconut milk emulsions extensively flocculated at pH 4, or around the pI of the coconut proteins. Salt addition induced flocculation in both emulsions. The pH and salt dependence indicated polyelectrolyte nature of proteins, suggesting that the proteins on the surface of oil droplets were not completely displaced by either added nonionic SE or TW. TW coconut milk emulsions appeared to be thermally unstable with some coalesced oil drops after heating and some oil layers separated on top after freeze thawing. The change in temperature had much lesser influence on stability of SE coconut milk emulsions and, especially, it was found that SE emulsions were remarkably stable after the freeze thawing.     

Physicochemical properties of thermal alkaline treated pigeonpea (Cajanus cajan L.) flour

Thermal alkaline treatment, normally used for corn, was applied to pigeonpea grains. Starch granules were isolated using wet milling and alkaline treatments. Effects of the calcium hydroxide [Ca(OH)₂] concentration in the range of 0–1% (w/v) on granule structure, crystalline structure, chemical composition, and physicochemical, thermal, and pasting properties of isolated starch granules were determined. Compared to native samples, thermal alkaline treated samples had higher protein, lipid, calcium, and phosphorus contents, but lower starch and amylose contents. Thermal alkaline treatment increased starch granular size and gelatinization temperatures, but decreased relative crystallinity, gelatinization enthalpy, swelling power, solubility, amylose leaching, and the pasting viscosity. Amylose-lipid complexes were not found in thermal alkaline treated flours. As the Ca(OH)₂ concentration increased, the amylose content, relative crystallinity, gelatinization temperature, and enthalpy also increased, but the swelling power, solubility, amylose leaching, and paste viscosity decreased. A higher Ca(OH)₂ concentration produced more stable starch granules that resisted re-gelatinization.     

Taro Colocasia esculenta (L.) Schott Amylopectin Structure and Its Effect on Starch Functional Properties

Flour extracted from small‐, medium‐, and large‐corm taro Colocasia esculenta (L.) Schott cultivated in central Thailand had similar proximate composition, comparable calcium oxalate and amylose content, but different starch granule size and average chain length of amylopectin. Starch from the larger corm taro had a smaller average granule size and a lower average amylopectin chain length (CL_avg), a lower average external chain length (ECL_avg), and a lower average internal chain length (ICL_avg) when compared to that from the smaller corm taro. The solubility of taro starch was inversely proportional to CL_avg, ECL_avg, and ICL_avg. Starch having a shorter CL_avg, ECL_avg, and ICL_avg had a higher peak viscosity and breakdown. The onset (T_o), peak (T_p), and conclusion temperatures (T_c) of starch gelatinization and the extent of starch paste retrogradation did not correlate with the amylopectin structure.     

Structure‐Viscosity Relationships for Thai Rice Starches

The viscosities of five Thai rice starches with different amylose contents were measured by rotational rheometry and using a Rapid Visco Analyser. The viscosity response was interpreted in terms of the swelling volume and the structural properties of the granule determined by calorimetry, infrared spectroscopy and X‐ray diffraction. It was found that the waxy rice starches had a higher swelling volume resulting in a higher viscosity than the other rice classes. Critical concentrations for close packing, identified from the concentration where the flow behaviour departs from Newtonian, were 2.5%, 1.5% and 1.10% for the high amylose, medium amylose and waxy rice starch, respectively. An exception to this was a commercial high amylose starch that had a critical concentration similar to the medium amylose category. This was ex‐plained in terms of a relatively higher loss of short‐range molecular order on gelatini‐sation as shown by FTIR for this starch. Medium amylose Jasmine rice starch, extracted from rice that had been aged for 5 months, showed differences in granule size, crystallinity, pasting profile and enthalpy of gelatinisation when compared with the results for starch extracted from freshly harvested rice. This was provisionally interpreted in terms of granule damage during the extraction process, though more work would be required to confirm this interpretation.     

X-ray Diffraction Pattern and Functional Properties of <Emphasis Type="Italic">Dioscorea hispida</Emphasis> Dennst Starch Hydrothermally Modified at Different Temperatures

Starch from Thai yam Dioscorea hispida Dennst was hydrothermally modified at its original moisture content (∼13%, w/w) and 90 °C to 130 °C for 10 h. X-ray diffraction analysis of the modified starch showed that the crystallographic pattern of the starch was altered from type B in native starch to type C in the starch modified at 90 °C and to type A in those modified at 100–130 °C. Along with the change in crystallographic pattern, decreases in granule swelling, starch solubility, and amylose leaching were observed. Up to the modification temperature of 100 °C, a reduction in the estimated degree of crystallinity and an increase in peak viscosity were noted. Seven percent starch gel of all modified starches, except for that modified at 130 °C, showed higher complex moduli over 0.001 to 10 Hz in dynamic shear test when compared with 7% native starch gel.     

Effect of concentration on apparent viscosity of a globular protein solution

The viscosity of a globular protein solution as a function of concentration was studied with a cone and plate viscometef (Ferranti-Shirley Viscometer System) using, β-lactoglobulin as a model. An aqueous buffer solution (pH 7, ionic strength 0.04) containing up to 40 percent protein was subjected to rates of shear between 800 and 17,000 sec^?1. Specific viscosity of β-lactoglobulin up to 10 weight percent was proportional to the weight concentration of protein in solution such that: η_s = η₀ [ 1+0.8 (weight percent concentration)] where η₀ and η_s are viscosity coefficients for the pure solvent and the solution, respectively. For 3-40 weight percent, a linear relation of shear rate and shear stress was observed at high shear rates. Linearity began at 3500, 4300, 6800, and 7000 see^?1 for 10, 20, 30 and 40 weight percent concentrations respectively. The apparent viscosity was lower below these critical shear rates.