Investigating the Commercial Microwave Vacuum Drying Conditions on Physicochemical Properties and Radical Scavenging Ability of Thai Green Tea

The effects of drying conditions using a commercial microwave vacuum dryer on the physicochemical properties and antioxidant activity of Thai green tea were investigated. Nine different drying conditions (power 3200, 3600, and 4000 Watts vs. radiation time 20, 25, and 30 min) were applied in this study. The results showed that individual catechins, their total quantities, radical scavenging ability, and moisture content were significantly affected; however, total polyphenol content and color parameters were not significantly affected by these drying conditions. Based on this data, to obtain optimal physicochemical properties of green tea, drying conditions at 3600 Watts for 30 min were recommended.     

Activated Kaolin Minerals as Bleaching Clays for Prolonging the Useful Life of Palm Oil in Industrial Frying Operations

During frying operations, vegetable oils break down and compounds with undesirable flavors are produced. Various procedures have been developed to extend the useful life of frying oils, including treatment with bleaching clays. In this article, we describe the activation of kaolin minerals by a combination of grinding and chemical treatments, and report their performance in removing breakdown products generated in palm oil that had been used for 20 hours continuous frying. There was little influence of the original kaolin mineral form on the ability to reduce the free fatty acid (FFA) contents, and grinding only changed FFA reduction from ∼32% to ∼36%. However, much greater FFA reductions were obtained after chemical treatment of the ground clays, and the best performing kaolin product gave similar FFA reduction to a commercial bleaching clay (∼76% and ∼77%, respectively). This activated kaolin also produced a reduction in viscosity at 40 °C from ∼73 to 48.4 cSt (compared to 45.5 cSt in the unused oil), and in the peroxide value from 30.0 to 22.0 meq/kg (compared to 10.0 meq/kg in the initial oil). Thus, activated kaolin samples represent a cheap and convenient alternative to conventional bleaching clay for improving common quality parameters in used palm oil, although we also found that the optimum kaolin preparation conditions were different from those that have been reported for raw rice bran oil refining.     

Effect of Alumina Content and Surface Area of Acid‐Activated Kaolin on Bleaching of Rice Bran Oil

This study investigated the effect of kaolin acid activation on alumina losses, surface area changes and oil bleaching performance. Ground kaolin was treated with hydrochloric or citric acid, and bleaching tests were performed on rice bran oil. The adsorption studies showed that the optimal bleaching of ~83 or ~81 % were achieved by activation with 0.5 M hydrochloric or citric acid, respectively, whereas bleaching with a commercial clay was ~82 %. The highest bleaching value was not associated with the maximum clay surface area or porosity. X‐ray fluorescence showed that alumina contents of 31–34 % were suggestive for optimum bleaching depending on the different acid used. Treating ground kaolin with the same hydrochloric acid strength by varying the acid concentration and clay/acid ratio also confirmed that the best Al³⁺ content was ~32 %, and a value lower than one indicated the extensively destruction of kaolinite proportions leading to a decrease in its bleaching capacity, even though it had the maximum surface area. The decrease in capacity was due to the reduction of alumina content, and the parallel formation of high amorphous silica was favorable for the adsorption of anionic pigments, such as chlorophyll‐a.     

Comparative evaluation of physicochemical,functional and texture properties and sensory acceptance of different instant rice varieties coated with Spirulina and edible polymers

This study aimed to determine the influence of Spirulina platensis and edible polymer coating on the physicochemical and texture properties, and sensory acceptance of coated instant rice: glutinous white rice (GWR), glutinous black rice (GBR), non-glutinous white rice (NWR) and non-glutinous black rice (NBR). Instant rice was cooked and dried, and then coated by a pan-coating process. Black rice varieties (GBR and NBR) showed higher amounts of protein, fibre, ash and bioactive compounds than white rice varieties (GWR and NWR). The Spirulina-coated rice had significantly improved texture properties, especially black rice cultivars. The hedonic rating of the coated instant rice ranged from 5 (neither like nor dislike) to 6 (slightly liked), and GBR obtained a higher acceptability score (6.93). Principal component analysis models allowed sample classification. Therefore, fortification with Spirulina as a coating on instant rice could be an alternative way to produce functional instant rice with extra health benefits.     

Production,iron analysis and consumer perception of functional Thai Sinlek iron rice (Oryza sativa) drink

We produced the iron rice (IR) drink, determined the relevant chemical composition and antioxidant activity and tested the consumers’ degree of satisfaction. IR grains were digested with α-amylase and analysed chemical composition and antioxidant activity, while the hydrolysate (pH 4.0) and flavouring agents were added for final preparation of the IR drink. The IR hydrolysate contained a total iron content of 13.9 mg g⁻¹, a total phenolic content of 1.33 ± 0.07 mg gallic acid equivalent g⁻¹ and γ-oryzanol of 70.12 ± 2.7 mg kg⁻¹ rice grain, all of which inhibited the generation of free radicals in a concentration-dependent manner. The IR drink was composed of flavonoids and phenolic acids for which kaempferol was predominant. The members of all three groups of elderly subjects who consumed the low-dose IR (1.47 mg iron/100 mL), high-dose IR (2.74 mg iron/100 mL) and white rice (WR; 0.5 mg iron/100 mL) drinks expressed satisfaction and interest with the beverages at 91.2%, 100% and 88.9%, respectively. In terms of sensory evaluation, the low-dose IR drink revealed a higher acceptance rating than high-dose IR and WR (P < 0.05). Notably, the Sinlek rice drink was abundant with iron, anti-oxidative phenolics and γ-oryzanol, for which consumers expressed an overall degree of acceptance (8.1 ± 1.1).     

Comparative evaluation of physicochemical properties of Lingzhi (Ganoderma lucidum) as affected by drying conditions and extraction methods

Lingzhi (Ganoderma lucidum) is a high-potential mushroom which is used as a dietary supplement or a source of nutrients and antioxidant agents. The aims were to investigate the effect of drying conditions (hot air and vacuum dry) and to compare the extraction methods of microwave-assisted extraction (MAE) and pulsed electric field extraction (PEF) for obtaining triterpenes, flavonoid and polysaccharides. The favourable drying condition was 80 °C for 1 h and 37 min, which achieved 1.17 ± 0.05 mg quercetin/g of flavonoids and 11.49 ± 0.87 mg ursolic acid/g of triterpenes. The MAE condition was 800 W, 1 min 30 s extraction time and 65.35% ethanol, achieving polysaccharides of 13.08 mg glucose/g and triterpenes of 9.15 mg ursolic acid/g. Additionally, MAE was significantly more efficient than reflux and PEF methods. The application of microwave radiation is beneficial in saving time and solvent and also provides high extraction efficiency for dried Lingzhi.     

Effects of thermal processing on antioxidant activities,amino acid composition and protein molecular weight distributions of jasmine rice bran protein hydrolysate

This research aimed to evaluate the effects of thermal processing on the amino acid composition, molecular weight distribution (MW) and antioxidant activities of Jasmine rice bran protein hydrolysates (JBH). JBH was prepared by enzymatic hydrolysate (alcalase and flavourzyme at a ratio of 9.81:90.19, 2.84% w/w) for 60 min. JBH samples were treated as follows: non-heat (NJBH), pasteurisation (72ºC, 15 min; PJBH) and sterilisation (121ºC, 15 min; SJBH). For SJBH treatment, the browning index and fluorescence intensity increased (P < 0.05). FTIR showed that thermal process changed the intensities and location of some bands. Thermal processing affected MW by decreasing it from high MW (>10 kDa) to medium (3–10 kDa) and low MW (<3 kDa). Val, Met, Ile and Leu contents increased after thermal processing. Compared with NJBH, the IC₅₀ values of ABTS and FRAP of SJBH were not significantly different, while the IC₅₀ of DPPH increased (P ≥ 0.05).     

Decolorization of Rice Bran Oil Using Modified Kaolin

Measurements show that kaolin from Ranong, obtained from a major deposit in southern Thailand, can be modified to produce a material that is suitable for decolorizing rice bran oil. Its sorption properties were determined after various physical and chemical modifications of this kaolin. Physical modification was achieved by grinding via a planetary ball mill (300 rpm for 1 h), and this was followed by chemical treatment using sulfuric or oxalic acids. The optimum decolorization capacity (~80%) was achieved by using 2 M sulfuric acid. With oxalic acid, the best results were obtained with 0.7 M, but these were slightly lower than those obtained with 2 M sulfuric acid. Compared to the original kaolin sample, the specific surface area of the modified clay increased from ~13 to ~244 cm² g⁻¹, and the total pore volume from 0.06 to 0.43 cm³ g⁻¹. The pore size distribution curves show that most pores are in the mesoporous region with their diameters between 3.0–4.5 nm, and are suitable for adsorption of pigment molecules that are present in rice bran oil. Desorption and spectroscopic studies suggest that both electrostatic and chemical processes are involved in the interaction between pigments and active sites on the clay surface.     

Effects of particle type on thermal and mechanical properties of polyoxymethylene nanocomposites

The effects of particle size of titanium dioxide (TiO₂) on mechanical, thermal, and morphological properties of pure polyoxymethylene (POM) and POM/TiO₂ nanocomposites were investigated and compared with the results for nanoparticle ZnO in the same matrix, reported in a previous paper. POM/TiO₂ nanocomposites with varying concentration of TiO₂ were prepared by the melt mixing technique in a twin screw extruder, the same method that used for blending the homogeneous ZnO nanocomposites. The dispersion of TiO₂ particles in POM nanocomposites was studied by scanning electron microscopy (SEM). The agglomeration, as observed by the mechanical properties of TiO₂ particles in the polymer matrix, increased with increasing TiO₂ content, a result not found for ZnO even at lower particle sizes. Increasing the filler content of POM/TD32.4 and POM/TD130 (130 nm) nanocomposites resulted in a decrease in tensile strength. The Young modulus, stress at break and impact strength of TiO₂ nanocomposite did not improve with increasing filler contents, in opposition to the better agglomeration conditions of ZnO nanocomposite even at lower particle sizes. Because of agglomeration, the POM/TD32.4 nanocomposites had lower mechanical properties and lower degradation temperature than the POM/TD130 ones. The sizes of nanoparticles determined the agglomeration, but however, the agglomeration also depended on the type of nanoparticles, even when using the same matrix (POM) and the same mixing method. TiO₂ nanoparticles were more difficult to mix and were more agglomerated in the POM matrix as compared to ZnO nanoparticles, regardless of the size of the nanoparticles. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012