Improvement of Temperature Stability,Dielectric Properties and Nonlinear Current-Electric Field Characteristic of CaCu 3 Ti 4.2−x Sn x O 12 Ceramics

The dielectric properties and the nonlinear current density–electric field (J–E) relationship of CaCu3Ti4.2−xSnxO12 (x = 0.00, 0.05 and 0.10) ceramics at various sintering temperatures are presented. Excellent dielectric properties with a very low tanδ ∼ 0.008–0.020, a giant ε′ ∼ 6495–16,975, and stability of Δε′ of < ± 15% over the temperature range of −60 to 210°C are obtained in a CaCu3Ti4.15Sn0.05O12 ceramic sintered at 1080°C and CaCu3Ti4.10Sn0.10O12 ceramics sintered at both 1080°C and 1100°C. Additionally, all ceramics exhibited a nonlinear J–E relationship. A maximal nonlinear coefficient (α) of ∼ 1044.4 is obtained in the CaCu3Ti4.15Sn0.05O12 sintered at 1080°C. X-ray diffraction and field emission scanning electron microscopy techniques were used for structural and microstructural evaluation of all ceramics. Elemental mapping with energy dispersive X-ray spectroscopy confirmed the presence of Sn4+ dopant at the main CaCu3Ti4O12 site and in minor TiO2 phases of all Sn4+ doped CaCu3Ti4.2O12 ceramics. This mixed phase plays an important role to increase grain boundary resistance (Rgb) and significantly improves the thermal stability of dielectric properties, as well as the nonlinear J-E relationship.     

Lactic acid bacteria and yeasts isolated from the starter doughs for Chinese steamed buns in Thailand

Isolation of lactic acid bacteria (LAB) and yeasts from the starter dough of Chinese steamed buns from four different commercial sources in Thailand was carried out. Thirty-one lactic acid bacteria and eight yeast strains were isolated. Total counts of LAB were from 1.8 × 10⁴ to 10⁸ colonies/g sample, whilst yeasts were very low from 10 to 2.3 × 10² colonies/g sample. The pH values of all starter doughs ranged from 3.36 to 3.52 and the Total Titratable Acidity (TTA) varied from 11.1 to 17.0 ml of 0.1 N NaOH/10 g dough. All LAB isolates were identified as Lactobacillus. The phenotypic characteristics were used to cluster all the LAB isolates into two major groups (Group A and Group B), with the B group subdivided into four groups. Phylogenetic analysis, based upon partial 16S rRNA gene sequences, showed that isolates of Group A, which all contained meso-diaminopimelic acid in their cell wall and produced dl-lactic acid, were closely related to Lactobacillus plantarum, whilst the strains of Group B that produced l-lactic acid were closely related to Lactobacillus casei. For yeasts, eight isolates based on the D1/D2 domain sequences of 26S rRNA were identified as Candida tropicalis, Pichia stipitis, Candida parapsilosis, Issatchenkia orientalis and Saccharomyces cerevisiae.     

Visual comfort in using different VDT screens

In order to meet the goal of user comfort of information displays, visual problems of video display terminal (VDT) work were studied through the analysis of visual functions in two experiments. Eye movement analysis, in Experiment 1, revealed that VDT operators had to move their eyes 2.5 times faster than traditional clerical workers. Lens accommodation, pupil size, and subjective visual comfort were investigated in Experiment 2. A significant correlation was found between the velocity of lens accommodation and the subjective visual comfort while viewing seven different displays (r = .809). A positive‐type cathode‐ray tube (CRT), which has dark characters on a light background, was ascertained to be the most appropriate display type, while working with a liquid crystal display (LCD) was considered to be the least visually comfortable, with the lowest accommodative velocity.     

Storage quality of pineapple juice non-thermally pasteurized and clarified by microfiltration

Microfiltration (MF) is classified as a non-thermal process for the fruit juice industry. It could provide a better preservation of the phytochemical property and flavor of the juice. This work aimed to study the stability of phytochemical properties including vitamin C, total phenolic content, antioxidant capacity (2-Diphenly-1-picrylhydrazyl: DPPH, free radical scavenging capacity and Oxygen Radical Absorbance Capacity: ORAC assays), microbial and chemical–physical (color, browning index, pH and total soluble solid) properties of MF-clarified pineapple juice during storage at various temperatures (i.e. 4, 27, and 37 °C). The juices were clarified by microfiltration using hollow fiber module. The results showed that most of the phytochemical properties and soluble components were retained in the juice after microfiltration. No microbial growth was detected after 6 months of storage. The storage time and temperature did not affect total soluble solids and pH (P > 0.05). The color (L^*) of clarified juice stored at 4 °C was lighter than the juices stored at higher temperature levels (P < 0.05). The phytochemical properties and total phenol content of the juice significantly decreased as storage time and temperature increased (P < 0.05). Vitamin C content was the attribute that affected storage time and temperature most as indicated by reaction rate constant and activated energy. Storage of non-thermally pasteurized and clarified pineapple juice at 4 °C was the most suitable since it allowed the best quality preservation.     

Melatonin contents in mulberry (Morus spp.) leaves: Effects of sample preparation,cultivar, leaf age and tea processing

The effects of sample preparation, cultivar, leaf age and tea processing on melatonin content of mulberry (Morus spp.) leaves were investigated. Sample preparation using ultrasonic technique in combination with solid phase extraction resulted in high recovery rate (76%), when compared to homogenisation in combination with liquid–liquid extraction procedure (12% recovery rate). The melatonin contents in mulberry leaves harvested from three major cultivars (Buriram 60, Sakonnakhon and Khunphai) grown in Thailand were identified and quantified using high-performance liquid chromatography combined with fluorescence detector. The average melatonin content of the mulberry leaves cv. Buriram 60 (279.6 ng/g dry weight (DW)) was higher than those of cv. Sakonnakhon (100.5 ng/g DW) and cv. Khunphai (40.7 ng/g DW). The melatonin contents of all cultivars tested were highest in the tip of the leaves, followed by that in the young leaves, whereas the lowest was found in the old leaves. The melatonin contents of the two types of tea produced from mulberry leaves cv. Buriram 60 were also determined. Heat treatment during tea processing decreased the melatonin content in mulberry leaves cv. Buriram 60 by approximately 87%, when compared to that of the fresh leaves. However, there were no significant differences between the melatonin contents of the mulberry leaf tea produced with blanching (mulberry green tea) and those produced without blanching (mulberry black tea).     

Effect of membrane property and operating conditions on phytochemical properties and permeate flux during clarification of pineapple juice

The effects of membrane property on the permeate flux, membrane fouling and quality of clarified pineapple juice were studied. Both microfiltration (membrane pore size of 0.1 and 0.2 μm) and ultrafiltration (membrane molecular weight cut-off (MWCO) of 30 and 100 kDa) membranes were employed. Membrane filtration did not have significant effects on the pH, reducing sugar and acidity of clarified juice whereas the suspended solids and microorganism were completely removed. The 0.2 μm membrane gave the highest permeate flux, total vitamin C content, total phenolic content and antioxidant capacity as well as the highest value of irreversible fouling. Based on these results, the membrane with pore size of 0.2 μm was considered to be the most suitable membrane for the clarification of pineapple juice. The optimum operating conditions for the clarification pineapple juice by membrane filtration was a cross-flow velocity of 3.4 ms⁻¹ and transmembrane pressure (TMP) of 0.7 bar. An average flux of about 37 lm⁻² h⁻¹ was obtained during the microfiltration of pineapple juice under the optimum conditions using batch concentration mode.