This research studied various types of packaging to prolong the shelf life of non-preservative white bread. Three types of blown film packages were used, i.e. a single LDPE layer incorporated with an oxygen scavenger, a single LDPE layer containing an oxygen absorber sachet, and three layers of LDPE laminated with O-nylon. The effects of modified packaging atmosphere, i.e. 5, 10, and 21 vol. % of oxygen in nitrogen balance, on the shelf life was also included. Characterization of the packaging films was carried out using several techniques, such as Oxygen Transmission Rate (OTR) and an optical microscopy. Headspace gases, microbial count, as well as physical appearance were used to evaluate the shelf life. The optical microscopic images showed that incorporating the oxygen scavenger into the plastic film produced small pores, contributing to a passive function of the films as their OTRs were significantly enhanced. However, the microbial growth on bread stored in those packages was suppressed, implying that the intermediate generated from scavenging reaction might act as a fungistatic. Even though the scavenging capability of the oxygen absorber sachet lasted only for 4 days, the fungi and mould development thereafter was still lower compared to the package without the sachet. The prolonging white bread shelf life was found to be primarily dependent on two factors. The package with a high oxygen barrier such three-layer films defeated microorganisms. With a low initial oxygen level of around 5% by volume, the bread shelf life could be prolonged up to 5–7 days.

No abstract

Extraction and characterization of acid soluble collagen (ASC) and pepsin soluble collagen (PSC) from scales of Giant groupers (saltwater fish) and Nile tilapia (freshwater fish) were carried out in this research. Due to a higher protein content in scales, collagen yield extracted from the Giant groupers scales was higher than that of the Nile tilapia scales. The yield increased as extraction time increased for both ASC and PSC and pepsin extraction resulted in higher yields than acid extraction. Even though there were differences in collagen yields, collagen characteristics were independent of the scale sources but some differences were observed for the ASC and PSC. The peptide hydrolysis patterns of the ASC showed a wide range of molecular weights whereas all of the PSC had similar molecular weight of around 42 kDa. FTIR spectra showed that all the collagens remained the triple helical structure though ASC might be self-aggregated. From zeta potential analysis, net charge of zero was found at pH 3.2-4.0 and the dynamic light scattering suggested that the average particle sizes at pH 11-12 were around 100-200 nm. The denaturation temperatures (Tds) in a range of 35-42 o C indicated that the collagens were considerably thermally stable.

Abstract. Variable Frequency Microwave (VFM) is known to be a rapid, volumetric, and selective form of heating which has shown potential as an alternative technique for the processing of negative-tone SU8 photoresist in the Micro-Electro-Mechanical System (MEMS) industry. A comparison of thermal properties of the films cured during the softbake and post exposure bake process using different techniques, i.e. conventional thermal curing, VFM curing, and a combination of both (referred to as hybrid, HY), was investigated using a Differential Scanning Calorimeter (DSC) and Thermogravimetric Analysis (TGA). A significant increase on the degree of cure (between 13-23%) was observed using the VFM over the hybrid and hotplate curing which means that SU8 curing at lower temperatures or rapid curing is possible. The increase in cure rates can be attributed to a combination of heat transfer and the unique capability of microwave to couple with the sample (selective heating). The improvement in curing at the same processing temperatures has important implications for processing thick films. It was found that regardless of curing methods, crosslink densities increased as the baking temperature increased, resulting in lower dielectric properties. Despite higher crosslinking contents, VFM cured samples decomposed at 2-4°C lower temperatures. In addition to better thermal properties, VFM offered satisfactory microstructure at lower curing temperatures; however, high processing temperatures could result in film cracking.

No abstract