Determination of effective moisture diffusivity and assessment of quality attributes of banana slices during drying

The influence of drying temperatures on the moisture diffusivity and quality attributes of the dried banana slices in terms of volatile compound, shrinkage, color, texture and microstructure were studied. Bananas with peel color index of 5 corresponding to yellow color with green tip were sliced into 3 mm thickness, dipped into ascorbic acid solution and dried at four temperatures of 70, 80, 90 and 100 °C. Drying rate of banana slices can be divided into two sub-drying periods, first and second falling rate periods. The effective diffusivity estimated by the optimization technique was found to decrease sharply with moisture content in the first falling rate period and changed slightly in the second falling rate period. High-temperature drying seems to provide lower loss of volatile compounds in the dried sample. Moreover, the dried banana was very porous, resulting in remarkably lower hardness value than that obtained from the low-temperature drying whilst the crispiness was not significantly different amongst the samples obtained at various drying temperatures. Although the textural property could be improved at high temperature, the product color was brown as manifested by the low L- and hue values in particular at the drying temperature of 100 °C.     

Antioxidant activity, ascorbic acid, phenolic compounds and sugars of wild and commercial Tuberaria lignosa samples: Effects of drying and oral preparation methods

The antioxidant activity and phytochemical composition (ascorbic acid, free sugars and phenolic compounds) of decoctions and infusions of wild and commercial samples of Tuberaria lignosa (Sweet) Samp. Aerial parts were evaluated and compared. Among wild samples, the effects of the drying method (freeze or shade-drying) on those parameters were studied. Infusion of the freeze-dried wild sample gave the highest levels of sugars, while infusion of shade-dried wild sample and decoction of the freeze-dried sample presented higher ascorbic acid and phenolic compounds content (including ellagitannins and flavonoids) than the other samples. The last two samples also revealed higher antioxidant activity, in some cases even higher than Trolox. Decoctions gave lower amounts of disaccharides than infusions, which seemed to be hydrolysed, increasing the content of monosaccharides. Commercial samples showed the lowest content in phenolic compounds, mainly in ellagitannins and flavonoids, and also the lowest antioxidant activity. This work gives scientific evidence to the traditional medicinal uses of wild Tuberaria lignosa, highlighting the interest of its decoctions and infusions as a source of bioactive compounds and functional beverages.     

HIGH TEMPERATURE DRYING FROM THE THREE PRIMARY ORTHOGONAL SURFACES OF LOBLOLLY PINE

While several permeability studies have been performed, little information is available on the flow of water in wood along its three orthogonal axes during high temperature drying. Much southern yellow pine construction lumber is dried at temperatures above 100°C, thus how water moves in wood is of concern. In this experiment individual Loblolly pine (Pinus taeda) sapwood cubes were coated on two of their three orthogonal faces (longitudinal, radial, and tangential) and the effect of this sealing on the drying rate was determined. From these cubes, drying rates from each of the three primary planes were determined. The free water movement/evaporation between the radial and tangential faces was not statistically different, while the longitudinal rate was approximately three times faster. In commercial practice, the faster longitudinal rate is negated by the very small portion of transverse surface area relative to total lumber surface area. This partially explains why end checking and moisture variation in high temperature dried southern yellow pine lumber are not significant causes of degrade. There was no statistically significant difference in permeability across the seasons tested.     

Theoretical model of a drying system including turbulence aspects

Biological products contain high moisture content in the harvest period. Such moisture could cause their deterioration in storage. Drying is an interesting solution to keep the quality of these products. Generally, drying process is based on contact of a dry air phase with a wet solid. A theoretical model was developed to describe the dynamic behavior of a forced convection drying process. This model takes into account the entire dynamic phenomenon including turbulence, diffusivity and tortuosity effects. Only the mass transfer of water molecules during vaporization was referred to as an empirical expression. The model thus strongly build, was compared to Thompson’s empirical model. Corn grain was used in the validating process. Transient temperature and water content results are presented.     

提高陶瓷刀具在干切削加工中性能的方法

陶瓷刀具具有优良的切削性能.本文论述了陶瓷刀具的特点和切削性能,提出了提高陶瓷刀具性能的几种途径,对陶瓷刀具在干切削中的应用进行了分析.     

保香低温速溶红茶粉的研发

为了解决速溶茶粉的滋味淡、香气低、冷溶性差等问题,该试验以红茶为原料,采用高压脉冲电场（Pulsed Electric Field,PEF）技术辅助提取和杀菌,并结合冷冻浓缩和真空冷冻干燥联合真空吸附干燥法生产速溶红茶粉,使得整个加工工艺都在低温状态下完成。试验结果表明,高压脉冲电场技术有助于提高红茶的提取率,冷冻浓缩和高压脉冲电场杀菌能够有效保持茶汤的色、香、味;真空冷冻干燥联合真空吸附干燥后所得的速溶红茶粉的得率为22.7%,且其冷溶性高,滋味鲜浓而醇厚,香气高而纯正,汤色红艳明亮,无沉淀。     

Effect of Pomace Drying on Apple Pectin

The effect of temperature used for drying apple pomace on apple pectin characteristics, including chemical composition, color and gelpoint temperature (T_g) was determined. Pomace was obtained from commercial Granny Smith apples and dried in a rotary drier at different air temperatures (T_dr = 60, 70, 80 and 105 °C). Pectin was extracted from dried pomace in nitric acid solution (pH = 2.5) at 80 °C. Major minerals in apple pectin were Ca>Na>Mg. Galacturonic acid content (% AGA=60.6±1.8) was practically unaffected by drying temperature. Conversely, T_dr affected both the degree of methoxylation (DM) and the molecular weight (M_w) of extracted pectin. M_w was estimated by applying the Mark Houwink - Sakurada equation, through determination of intrinsic viscosity of pectin solutions. M_w reduced withT_dr from approximately 122,000 (60°C) to 57,000 (105°C). Pectin color, as Hunter ΔE, was also affected by T_dr. A lighter color was obtained at 80°C. The higher gelpoint value (T_g= 80°C) was obtained with pectin from pomace dried at 80°C. Gelpoint was shown to be more sensitive to T_dr than other quality parameters: while DM had the same value both at 80 and 105°C, minimumT_g occurred at the higher temperature. T_g was also very sensitive to pH.     

管式分酸器在硫酸生产中的使用效果

管式分酸器应用于硫铁矿沸腾焙烧制酸装置,效果显著,与原挂钩槽式分酸器相比,干燥塔出口水份含量从０．４ｇ／ｍ＾３降至０．０８ｇ／ｍ＾３。     

Evaluation of the Sorption Equilibrium and Effect of Drying Temperature on the Antioxidant Capacity of the Jaboticaba (Myrciaria cauliflora)

In recent years, interest toward berries has increased (e.g., Myrciaria cauliflora or jaboticaba) because of their high phenolic content (phenolic acids, flavonoids, and anthocyanins) that has been associated with positive effects on consumer health and which play an important role in the antioxidant properties of food. This study analyzed the sorption isotherms, thermodynamic properties of sorption (isosteric heat and Gibbs free energy), and the evolution of the antioxidant capacity during the drying process. The effects of drying temperatures of 40°, 50°C, and 60°C on the antioxidant capacity and thermodynamic properties of sorption were evaluated. The gravimetric static method for sorption isotherm determination over a range of relative humidity levels from 0.10 to 0.90 was used. The sorption isotherms exhibited a Type II behavior, typical for many foods. The Guggenheim, Anderson, and Boer (GAB); Oswin; Peleg; and Lewicki models were used to fit the experimental data, and it was determined that the GAB and Peleg models were most appropriate for describing the sorption curves. The isosteric heat and Gibbs free energy were obtained from the experimental sorption equilibrium. The isosteric heat of adsorption decreased when the moisture content increased, while the Gibbs free energy increased. In addition, the phenolic content and antioxidant capacity increased while drying at 50°C and 60°C, whereas these factors decreased at 40°C. Our results provide the food industry with information concerning the best drying conditions to preserve antioxidant properties.