Showing papers by "Chung Lim Law published in 2014"

Color Change Kinetics of American Ginseng (Panax quinquefolium) Slices During Air Impingement Drying

Abstract: The color change kinetics of American ginseng (Panax quinquefolium) slices were investigated in an air impingement dryer under different drying temperatures (35, 45, 55, and 65°C) using the CIE Lab color parameters (L*, a*, b*) as the assessment indicators. Results illustrated that all three color parameters (L*, a*, b*) increased with drying time. The L* value decreased with increasing drying temperature. However, a* and b* values increased with the increase in drying temperature. Furthermore, at the initial drying stage the change rate of L* increased significantly, while towards the end of drying it reduced significantly. As regards a*, it slowly changed at the initial and final drying stages rather than in the intermediate drying stage. In the case of b*, it increased with increasing drying time and drying temperature during the whole process. The zero-order, first-order, and fractional conversion models were fitted to the experimental data, and the model's parameters were determined using linear regr...

Combined Drying of Apple Cubes by Using of Heat Pump, Vacuum-Microwave, and Intermittent Techniques

Abstract: Apple cubes of 15 mm were dried naturally without adding any chemical preservative using various drying methods namely intermittent hot air–dehumidified air drying with cyclic temperature profile and step-up temperature profile, heat-pump-assisted (HP) drying, convective vacuum-microwave (C/VM) drying, and heat pump vacuum-microwave (HP/VM) drying. The drying kinetics of apple samples dehydrated by different methods was divided into characteristic drying periods and fitted with empirical models, which gave high value of determination coefficient. The application of C/VM in drying of fruits gave the shortest drying time compared to other drying methods (about 50 % of the total drying time). The drying time was affected by effective diffusivity ranging from 3.522 × 10−8 to 1.431 × 10−6 m2/min depending on the drying technique used. It was found that combined drying which apply vacuum microwave (C/VM, HP/VM) gave the lowest values in hardness and chewiness. In addition, HP/VM drying gave the highest retained total polyphenol content, antioxidant activity, and the best appearance quality.

Effects of freeze drying on retention of essential oils, changes in glandular trichomes of lemon balm leaves.

Abstract: The effect of chamber pressure of a freeze dryer on essential oil contents, drying kinetics, drying characteristics lemon balm leaves and morphology of lemon balm glandular trichomes (oil reservoirs) were investigated. It was found that overall freeze drying (FD) carried out at high (FD-HP) and low pressure (FD-LP) settings consist of sublimation rate, first falling rate and second falling rate periods. Drying rate of FD-LP dried Lemon Balm leaves are higher than FD-HP dried samples, where the drying rates ranged from 0.063 to 0.449 g H2O/ g DM. s and 0.0365 to 0.395 g H2O/ g DM. s, respectively. 3 rd order Polynomial model was found to be the best fit model for both drying kinetics. In terms of product quality, eight (8) major constituents of lemon balm leaves essential oil were quantified. Further to this, electro-microscope was used to observe the peltate glandular hairs structure. Product quality analysis showed that FD-HP retained higher amount of essential oil, shape of glandular hairs, but no positive effect on the freeze drying duration.

Maximizing the Retention of Ganoderic Acids and Water-Soluble Polysaccharides Content of Ganoderma lucidum Using Two-Stage Dehydration Method

Abstract: Ganoderic acids and water-soluble polysaccharides are the main bioactive ingredients of Ganoderma lucidum and are heat sensitive. Hence, it is crucial to apply a suitable drying method for the drying of G. lucidum to minimize the loss of these bioactive ingredients. In this study, a two-stage drying method was applied to enhance the drying kinetics, as well as the retention of both ganoderic acids and water-soluble polysaccharides in dried G. lucidum fruiting bodies and slices compared to other single-stage-dried products. The results showed that two-stage drying enhanced the overall drying rate, which consequently shortened the total drying time up to 61 and 330% for fruiting bodies and slices, respectively, compared to single-stage drying methods. Furthermore, two-stage drying of Ganoderma fruiting bodies, which involves 18-h vacuum drying followed by 5-h heat pump drying, maximized the retention of ganoderic acids and water-soluble polysaccharides, with the retention of 97.90% of water-soluble polysacc...

Food Technologies: Drying

Abstract: Drying is an energy intensive unit operation in food processing to reduce product moisture content to a level that is safe for storage and transportation, to avoid microbial multiplication and inactivate microbial activity Generally, dryers are classified into different categories based on drying strategy, drying medium, mode of handling of drying material, and mode of heat transfer With reference to the dryer classification, dryers that permit high temperature drying or low temperature have the potential to avoid microbial multiplication and inactivate microbial activity In addition, hybrid drying which combines different drying techniques can also be considered Further, pretreatments can be applied in order to reduce or eliminate microbial load of a product before drying Drying material can also be exposed to irradiation or ionized environment for elimination of microorganisms during the drying process This chapter discusses and elaborates drying from the food safety point of view

Evaporation and Diffusion Transport Properties and Mechanical Properties of Alginate Dried Film

Abstract: The effects of alginate concentration and drying temperature on drying kinetics/characteristics of alginate solution and mechanical property of formed solid films were examined. Solid films were fabricated through thin-layer drying of 1 to 4%w/w sodium alginate solution at 40, 60, and 80°C using the solvent-evaporation method. The water weight loss profile of alginate solution undergoing drying was recorded with time. The polymer weight of all solid films was kept constant. The plasticity of films was evaluated using thermomechanical analyzer. The findings indicated that both constant rate and falling rate periods existed during drying of dilute alginate solution or at low drying temperature since both surface and core waters were available for drying. The falling rate period dominated in drying of an alginate solution of high polymer concentration and at high drying temperatures with internal diffusion being the governing transport phenomenon for water. In the latter, an exponential relationship between ...