Athapol Noomhorm

Effect of particle sizes on functional properties of dietary fibre prepared from sugarcane bagasse

Alkaline hydrogen peroxide (AHP) treatment affected physical and chemical properties of sugarcane bagasse (SB). AHP treatment can improve all its physical properties. The brightness, water-holding capacity (WHC), and oil-binding capacity (OBC) of SB were increased by 34, 96, and 55%, respectively. Lignin was removed from SB by 53%. Colour of Solka Floc 1 900, a commercial dietary fibre, was pure white (L=93.51); WHC and OBC were 8.61 g water/g sample and 7.34g oil/g sample, respectively. The results showed a highly positive correlation between particle size reduction of each dietary fibre (DF), WHC and OBC. While density showed a negative correlation, densities of AHP-SB and Solka Floc 1 900 were increased, with particle size reduction, from 1.06 to 1.34and from 1.09 to 1.28, respectively. At 5% of AHP-SB and Solka Floc 1 900 substitution in bread, reductions of loaf volume and softness of bread were observed in direct opposition to particle size reduction. The most acceptable breads contained 5% of AHP-SB and Solka Floc 1 900 when the particle sizes were < 0.075 and < 0.106 mm, respectively. # 2002 Elsevier Science Ltd. All rights reserved.

Effect of Aging on the Quality of Glutinous Rice Crackers

ABSTRACT The experiment was conducted to study the effects of aging on the physicochemical properties of two Thai cultivars of milled glutinous rice (RD6 and RD8). The amylose and protein content of rice samples did not change when stored from 0 to 4 months. Amylograph curves from samples of milled rice stored from 0 to 8 months were analyzed. Both cultivars gave constant gelatinization temperature during aging. The values for peak viscosity, final viscosity on cooking at 94°C, viscosity on cooling to 50°C and breakdown decreased significantly for RD6 cultivar, whereas the setback value and consistency were not changed significantly. For RD8 cultivar, no significant difference was observed for viscosity on cooling to 50°C and consistency during aging up to 8 months. Peak viscosity and breakdown value were reduced during storage, whereas the final viscosity on cooking at 94°C and setback value increased with time. Raw milled rice of both RD6 and RD8 cultivars have similar water uptake rates. Stored rice te...

EFFECT OF DRYING AIR TEMPERATURE AND GRAIN TEMPERATURE OF DIFFERENT TYPES OF DRYER AND OPERATION ON RICE QUALITY

Quality of aromatic rice (KDML-105) and non-aromatic rice (Suphanburi I) was studied using different methods and scales of drying. At the lab scale, rough rice at high moisture (21±1% w.b.) was subjected to shade drying, sun drying, oven drying at 45 °C and 60 °C and fluidized bed drying (for different time periods) at 120 °C, with tempering for 2hrs. On a commercial scale, single stage drying (sun drying, column drying) and multi stage drying in a fluidized bed dryer coupled with column and shade drying were investigated. Head rice yield, color, hardness, stickiness and hardness ratio, water absorption, and structure of milled rice were examined for each method of drying. The results revealed that water absorption and ratio of stickiness and hardness decreased but the b-value and hardness increased with increase in dry grain temperature, longer exposure/drying time, longer tempering time, and rapid rate of water removal. Head rice yield of samples dried at high temperature (>60 °C) followed by tempering and of those dried at low temperature (<45 °C) in case of lab scale drying was increased and no significant difference (p<0.05) was seen relative control samples. For single stage drying, at low temperature, and multi stage drying in the fluidized bed drier (interment tempering), at high temperature, head rice yield was decreased and exhibited significant difference (p<0.05) relative to control sample. The yield however increased for a sample subjected to a 12hr tempering period and then shade drying stage subsequent to drying in a fluidized bed drier. Drying of rough rice at low temperature (<45 °C) did not affect cooking and eating qualities of rice which were affected by drying at high temperature (>60 °C). Cooking and eating qualities however changed at both single and multi stage drying on a commercial scale.

Effect of Physicochemical Properties of High-Amylose Thai Rice Flours on Vermicelli Quality

ABSTRACT Certain physicochemical properties, including chemical composition, pasting, thermal parameters, and the gel texture of flour prepared from six cultivars of Thai rice with similar high-amylose content were determined. These properties were correlated with the quality of vermicelli prepared from these flours for cooking and textural properties. Flour prepared from a Thai rice cultivar currently used for commercial production of vermicelli served as reference for these comparisons. Many similarities, but some significant differences, in the physicochemical properties were observed between the test rice flours and to the reference cultivar. Vermicelli prepared from all of the test rice flours were within an acceptable range for cooking quality but showed greater variation in textural quality. Among the physicochemical properties, gel hardness was well correlated with cooking and textural quality of vermicelli, and was useful for predicting overall vermicelli quality.

Influence of Combined Hot Air Impingement and Infrared Drying on Drying Kinetics and Physical Properties of Potato Chips

Air jet impingement combined with infrared drying (IMIRD) was developed as an alternative processing method to produce health-friendly potato chips in place of conventional deep-fat frying. This article investigates the effects of IMIRD compared to air jet impingement drying alone (IMD) and conventional convective drying (CCVD) on potato being processed as potato chips in term of drying characteristics, quality attributes (shrinkage, color, and hardness), and specific energy consumption (SEC) of the dryer. The experiments were carried out at three different air velocities (5, 10, 15 m/s) and infrared intensities (0.16, 0.27, and 0.33 W/cm2) at a fixed air temperature of 85°C. The experimental results show that the drying air velocity and infrared intensity had a significant effect on the moisture removal from potato slices. IMIRD, compared to IMD and CCVD, provided a higher drying rate, less shrinkage, lower hardness, and less color deterioration. An increase in air velocity at each infrared intensity caused a decrease in the total SEC value.

Geosmin and Off-Flavor in Nile Tilapia (Oreochromis niloticus)

Abstract The concentration of geosmin (1,10-trans-dimethyl-trans-9-decaol) in fresh tilapia were analyzed by applying high-vacuum distillation, extraction and gas chromatography techniques. The distribution of geosmin in the fish was determined by examining tissues from various parts of tilapia, along with the rates of geosmin absorption and purging. Analysis showed that when geosmin was added to fish flesh at concentrations ranging from 2.8 to 390 μg per kg of flesh, the rate of recovery was 51 to 89%. Sensory evaluation detected muddy flavor in freshwater tilapia with geosmin content ranging from 7.55 to 9.85 μg/kg of fish flesh. However, panelists failed to detect muddy flavor in brackish water tilapia that contained geosmin only in the range of 1.5 to 2.6 μg/kg. Among various tissues of the fish, the intestines contained the highest geosmin concentration, and appeared in descending order in the abdominal, skin and muscle tissues. After holding for 2 h in water with 5 and 50 μg/l geosmin, tilapia absorbed 17.6 and 42.2 μg/kg geosmin in the flesh, respectively. Holding the fish over longer periods in water with higher geosmin content resulted in a greater amount of absorption. In contrast, transferring muddy-flavored fish to static clean water purged geosmin from the fish but it required at least 16 days to eliminate the muddy flavor.

Physiochemical Properties of Sweet Potato and Mung Bean Starch and Their Blends for Noodle Production

Physiochemical properties of four types of sweet potato starch (SPS) and mung bean starch (MBS), and their blends for noodle production were accessed. The results indicated that MBS was significantly higher in amylose content (40.69%), gel hardness, hot paste stability and cold paste viscosity; but substantially lower in protein, lipid, ash content, and gel stickiness than those of all sweet potato starches. Among all sweet potato varieties, the white skin and yellow-red flesh color sweet potato variety (SP1_W_YR) was the most suitable for noodle production due to its the highest starch yield (17%) and starch purity as well as the best starch color. The MBS noodle quality was superior to SPS noodle quality, and blending SPS with MBS for noodle production resulted in markedly reducing quality. However, the quality of noodles made from mixture of 20% SPS and 80% MBS was not significant difference to that of MBS noodles. The increase of solid content of starch slurry resulted in considerable increasing in cooking time, cooking loss, rehydration and tensile of noodles while aging time only markedly affected cooking loss and tensile. For noodles prepared from mixture of 20% SPS and 80% MBS, the most suitable initial solid content of starch slurry and aging time at 4 o C were 35% and 10-20 hrs respectively.

Effect of Raw Material Preparation on Rice Vermicelli Quality

The physicochemical properties of high amylose rice flour prepared from wet milling and dry milling were examined and the rice vermicelli quality made from these flour samples was evaluated. The effect of flour particle size on rice vermicelli quality was also determined. The milling method affected chemical compositions and all physicochemical properties of the flour. A higher degree of starch damage occurred in drymilled flour. Rice vermicelli made from dry-milled flour had higher cooking losses and softer texture than that made from wet-milled flour and the commercial reference products. Flour particle size influenced both cooking and textural quality of rice vermicelli but did not influence the water absorption index. Flours with larger particle sizes gave vermicelli with higher cooking loss and less desirable texture than flours with smaller particle sizes. Flour with particle sizes less than 200 mesh produced acceptable vermicelli in terms of cooking and textural quality.

A New Model and Quality of Unfrozen and Frozen Cooked Rice Dried in a Microwave Vibro-Fluidized Bed Dryer

This study aimed to develop a suitable drying model for microwave vibro-fluidized bed drying in a single-mode applicator (MVFB-SMA drying) of cooked rice with and without prefreezing treatment and to investigate the effects of prefreezing treatment and drying temperature (110–185°C) on quality of dried cooked rice. During the process of drying cooked rice from 60 to 10% (wet basis), results indicated that drying rate increased, whereas drying time decreased with prefreezing treatment and increased drying temperature. The drying rate and drying time of unfrozen and frozen cooked rice ranged from 0.196 to 0.497 g water/g dry matter/min and 0.228 to 0.554 g water/g dry matter/min; and from 7 to 2.5 min and 5.5 to 2 min, respectively. A new model was proposed in this study (MR = exp(−k t n ) + bt + c) to compare with 11 commonly used drying models. The new model describes the MVFB-SMA drying data most satisfactorily. The values of effective diffusivity were between 1.70 × 10−7 and 5.72 × 10−7 m2/s for the unfrozen sample and between 1.99 × 10−7 and 5.86 × 10−7 m2/s for the frozen sample. Their activation energy values were 23.66 and 21.19 kJ/mol, respectively. Prefreezing treatment provided a whiter product with a less uniform porous structure and higher bulk density. Slower ability to rehydrate was also observed for the frozen cooked rice dried at 160 and 185°C. An increase in drying temperature resulted in changes in whiteness, microstructure, bulk density, and rehydration capability. No prefreezing treatment and drying at 160°C seemed to be the optimal process condition for cooked rice, ensuring whiteness, a porous structure, low bulk density, and high rehydration capability.

Effect of particle sizes on in-vitro calcium and magnesium binding capacity of prepared dietary fibers

Abstract Microscopic examination showed a change on the surface structure of dietary fibers (DF) from rice straw (RS) and sugarcane bagasse (SB) by alkaline hydrogen peroxide (AHP) treatment. Effect of particle size on in-vitro binding of calcium (Ca) and magnesium (Mg) of AHP-RS, AHP-SB and Solka Floc® 900 (SF) were evaluated. Total bound Ca and Mg decreased with particle size reduction (P