俄罗斯落叶松锯材干燥过程中含水率和应力变化分析

分析了30mm厚度的俄罗斯进口落叶松(Larixgmelinii)木材干燥过程中的干缩量和干燥应力、以及含水率变化间关系。结果表明:俄罗斯产落叶松的弦、径向干缩系数和弦径向干缩比均小于国产落叶松,相同干燥条件下国产落叶松比俄罗斯产落叶松更易发生开裂和变形等缺陷;干燥过程中产生的应力与含水率梯度、干缩量和含水率、应力指标,存在一定的相关关系。     

Moisture stress during growth affects the breadmaking and gelatinisation properties of cassava (Manihot esculenta Crantz) flour

Breadmaking quality (judged by the regularity of the crumb) of cassava (in cassava flour/defatted soy flour/glyceryl monostearate recipes (80/20/3, w/w), Cereal Chem 68 323–327 1991) is related to crop age and the season of planting and harvesting. When taking the data sets of the dry season (J Sci Food Agric 66, 193–202 1994) and rainy season (ibid 68 167–174 1995) together, the following additional interpretation results: breadmaking quality of cassava is positively related to flour from roots with unrestricted growth, and therefore influenced by rainfall distribution, time of planting and harvesting. Variability in baking performance of cassava flour samples is related to the length and severity of the dry season, the growth behaviour of the genotype and the crop age. The highest flour breadmaking quality is obtained after 6 months of unrestricted growth of cassava irrespective of the planting season. © 1998 SCI.     

柞木干燥残余变形与应力、含水率及时间关系的研究

通过干燥实验找出柞木在干燥过程中残余变形与应力、含水率及应力之间的关系。利用数理统计中的回归分析与相关分析对实验所得的数据进行处理,最后得到有关残余变形与应力、含水率及时间之间关系的线性回归方程。实验结果表明:残余变形在干燥过程中受应力、含水率及时间的影响,且呈有规律的线性变化。     

鱼面的高温高湿干燥工艺研究

对鱼面的高温高湿干燥工艺进行研究,结果表明,高温高湿干燥可以提高鱼面的干燥速度,改善鱼面的品质。鱼面适宜的干燥条件为:前期干燥温度80℃、相对湿度60%、干燥时间30min,随后转入降温降湿干燥阶段,干燥时间约40min,产品最终含水量10.7%。     

Effect of drying temperature and beeswax content on physical properties of whey protein emulsion films

The objective of this work was to study the effect of drying temperature and the beeswax (BW) content on the physical properties of whey protein emulsion films. For this purpose, films were obtained by the casting method and dried at two selected temperatures (5 and 25 °C). Film thickness, water vapor permeability (WVP), solubility and mechanical properties were measured. The results showed that the decrease in drying temperature from 25 to 5 °C reduced the WVP and increased the solubility of the films containing BW. The effect of drying temperature on the mechanical properties was significant in the tensile test but not in the puncture test. The addition of BW decreased the WVP and the solubility and also had a significant effect on the evaluated parameters in both mechanical tests. In general, this effect was observed at both drying temperatures studied. Therefore, taking into account the several applications of the coatings the optimization of coating formulations and drying conditions is of vital importance.     

Rapid moisture and fat determination by pulsed NMR for monitoring drying and coating processes of extrudates

After extrusion cooking, extrudates must be dried and are often coated by spraying with fatty materials before cooling and packaging. As a means to control the drying and coating processes of pet foods, a rapid NMR method was developed to determine water and fat contents over a large temperature range without weighing, heating or measuring the temperature of the samples. Weighing was avoided by normalizing all NMR intensities by the solid echo maximum of each sample. Formulae using estimates of the transverse relaxation time and the concentration of liquid fat protons were used to determine total fat and moisture contents without measuring the temperature of the samples. Fat content estimation had a standard deviation better than 0.2% over a large solid fat index range above 20°C. Water content was determined with a standard deviation of about 0.2% at all temperatures studied.     

Effect of variety on the heat transfer coefficient during drying of fermented ground cassava

The effect of variety on the heat transfer coefficient of four cassava cultivars (TMS 30555, TMS 30572, NR 8082 and one Native type) was investigated. The cultivars were dried at an air temperature of 142 °C, air velocity of 1.397 m/s⁻¹ and relative humidity of 55%. The heat transfer coefficient obtained varied from 0.0622 to 0.0725 kJ kg s °C. The heat transfer coefficient varied for some cultivars, while some cultivars had close heat transfer coefficient. NR 8082 had the lowest heat transfer coefficient while TMS 30555 had the highest heat transfer coefficient. The cultivars with high heat transfer coefficient were found to have low bulk density, smaller particle diameter, high drying rate, low specific heat capacity and high carbohydrate fat and protein contents than other cultivars.     

Effect of Temperature and Relative Humidity on Drying Kinetics of Fresh Japanese Noodle (Udon)

The effects of temperature and relative humidity (RH) on the drying kinetics were investigated to identify the optimal drying conditions for Japanese noodle (udon). Drying of fresh udon was carried out under nine conditions involving three temperatures (20, 30 and 40°C) and three RHs (60, 70 and 80%) at a constant airflow. The apparent moisture diffusivities were determined using a diffusion model taking into account both the internal and external mass transfer resistances. The effect of RH on the apparent moisture diffusivity was found to be smaller than that of temperature, but could not be neglected. A modified Arrhenius-type equation of diffusivity involving a RH term was proposed and used for the calculation of moisture content with time. The proposed equation was found to be effective for representing the drying process of fresh udon.     

真空冷东干燥工艺参数对三文鱼片脱水率的影响研究

建立了冻千过程中,三文鱼片厚度、箱内真空度和加热搁板温度对脱水率综合影响的数学模型,采用回归分析的方法,确定了三文鱼片脱水率的主要影响因素,并推导出了一定工艺条件下,三文鱼片含水量动态变化的预测模型.     

Quality of plant-based food materials and its prediction during intermittent drying

In most drying processes, several physical, chemical and nutritional modifications take place in food products. Innovative drying techniques such as intermittent drying can enhance the quality of dehydrated products effectively and efficiently. Intermittent drying is a technique where drying conditions are changed through varying the drying air temperature, humidity, velocity, pressure, or even mode of heat input. This drying technique has been successfully applied to overcome the problems of conventional drying systems such as longer time consumption, case hardening, lower energy efficiency and poor-quality attributes. However, as the effect of intermittent drying on food quality is not yet well understood, a comprehensive study of quality change during intermittent drying is crucial. The main aim of this paper is to present a thorough review of the potential effect of intermittent drying methods on physical, chemical, nutritional, and stability characteristics of plant-based food material. It is found that application of intermittency using different drying systems has a significant effect on product quality and its stability. In addition, a comprehensive review on existing models of physio/biochemical kinetics for food drying is presented. Finally, the paper is concluded with the discussion of the current challenges and future directions of intermittent drying for producing high-quality dried food products.     

Effect of different drying methods on drying characteristics,colour, total phenolic content and antioxidant capacity of Goldenberry (Physalis peruviana L.)

In this study, the effects of convective, microwave and microwave–convective drying methods on the drying characteristics, colour, total phenolic content and antioxidant capacity of goldenberry fruits were investigated. To select the most appropriate thin‐layer drying model for drying treatments, nine mathematical drying models were fitted to the experimental data. Based on the statistical tests used for evaluation, the Midilli et al. and Wang and Singh models were considered the best models to describe the drying behaviours of goldenberry fruits in all drying methods. The colour values (L*, a* and b*) of fresh fruit were decreased by drying. Compared with the fresh sample, the dried samples exhibited a 64–75% and 65–75% decrease in total phenolic content and antioxidant capacity, respectively. Among the different drying treatments, the values closest to those of fresh samples with respect to colour values, total phenolic content and antioxidant capacity were achieved with the 160 W microwave drying method.     

Hot-air drying of whole fruit Chinese jujube (Zizyphus jujuba Miller): physicochemical properties of dried products

Drying characteristics of whole fruit was studied as distinct from fruit slices. Taking Chinese jujube as an example, shrinkage, density, vitamin C, colour and rehydration of whole fruit were measured in hot-air drying at 50, 60 and 70 °C. Unlike fruit slices or lumps where shrinkage volume typically equals the volume of removed water, volumetric shrinkage of Chinese jujube was much more than the volume of removed water. Change in shrinkage with moisture content was described using three linear regions. Increased drying temperature increases the retention of vitamin C and the extent of browning, while decreasing shrinkage and the density. The findings are useful for industrial drying of whole fruit of Chinese jujube but also possibly extend to drying of other drupes.     

Shrinkage and quality characteristics of whole fruit of Chinese jujube (Zizyphus jujuba Miller) in microwave drying

Drying characteristics of whole fruit Chinese jujube was studied as distinct from fruit slices. Shrinkage, density, vitamin C, colour and rehydration of Chinese jujube were measured in microwave drying at power level of 1.2, 1.67 and 2.5 W/g (dry base, db). Unlike fruit slices or lumps where, no matter at the beginning or at the end of drying, shrinkage volume typically equals the volume of removed water, ratio of the shrinkage volume to the volume of removed water of Chinese jujube could range from 2 to 2.6 at the beginning of drying, and at the end of drying, it could be 1.15 for higher microwave level (2.5 W/g, db), whereas, for lower power level (1.2 W/g, db), it was about 1. Unlike shrinkage curves in hot air drying that could be described with a three‐segment linear model, shrinkage curves in microwave drying could be well described with a cubic polynomial (R² > 0.99). When compared with the low power level (1.2 W/g, db), higher microwave power level(2.5 W/g, db) increased by 87.9% of the retention of vitamin C, 14.6% of the density and 8.7% of the extent of browning, decreased by 12.9% of the soluble solids content.     

对方便米线在多层带式干燥设备干燥过程的研究

以应用于方便米线生产实际的某型号多层带式干燥设备为研究对象,在生产现场对干燥设备的温度、湿度及方便米线干燥过程水分含量变化进行测试,考察方便米线的实际干燥条件和干燥过程及其可能对方便米线产品质量的影响。结果表明:干燥设备内温度、湿度变化较大并存在一些局部的高温低湿和低温高湿区域,造成米线水分在总体逐步降低的趋势下有较大的波动,这不仅不利于干燥的有效进行,而且当其波动幅度超过一定限度还有可能引起米线产品产生裂纹并断裂。     

Physicochemical and functional properties of chitosans affected by sun drying time during decoloration

The typical production of chitosan from crustacean shell consists of demineralization, deproteinization, decoloration, and deacetylation. Selected physicochemical and functional properties of chitosans as affected by various decoloration times (4, 5, 6, 7 or 8 h) using sun drying were evaluated. Moisture content (6.67-6.89 g/100 g), degree of deacetylation (81.91-82.73%), and color L^∗ value (78.32-79.43) of chitosans were not affected by sun drying time. However, color a^∗ and b^∗ values decreased when sun drying time was over 4 h. The viscosity of chitosan solution (0.5 g/100 mL acetic acid) decreased gradually with increasing sun drying time, with a more pronounced effect observed at 8 h of sun drying. There was no change in water-binding capacity (WBC) of chitosans decolorized by sun drying between 4 and 6 h; however, further increase in sun drying time from 6 to 7 or 8 h increased WBC of chitosans. DPPH radical scavenging activity of chitosans increased with increasing sun drying time. This study demonstrated that white-colored chitosans could be produced by an alternative decoloration step using sun drying for 4 h following the deacetylation step. However, increasing sun drying time to 7 h produced chitosan with increased WBC and DPPH radical scavenging activity.     

木材干燥过程中计算机断层扫描图像纠正方法的研究

还原和恢复变形图像是利用CT扫描非破坏性地研究木材内部水分迁移的关键基础问题。为恢复和还原干燥过程中由于干缩引起的木材CT图像的变形和由于扫描定位误差引起的图像移位,本文选择了三种方法,即图像像素移位法、最小方差法和最大重合法比较其效果。研究表明,像素移位法不适合于干缩较大的木材CT图像的处理,最大重合法的误差比像素移位法和最小方差法小。但对于干燥不均匀、干缩不一致或木材发生翘曲等缺陷的图像,最大重合法也会产生较大的误差。     

Muscle High-Energy Phosphates and Stress Affect K-Values during Ice Storage of Atlantic Salmon (Salmo salar)

Initial levels of white muscle high-energy phosphates, IMP, ATP:IMP-ratio, adenylate energy charge and pH were used as indicators of handling stress when Atlantic salmon were slaughtered. Ante-mortem handling included fish that were either anesthetized (baseline), quickly netted and killed by a blow to the head (unstressed) or chased to exhaustion in the holding tank (stressed). During subsequent storage in ice, freshness was evaluated in terms of IMP, HxR, Hx and K-values. HPLC showed initial differences in distribution of metabolites induced by struggling gradually fell during storage. K-values were different only for 2 days post mortem, but the effect of handling stress was discernible as higher mean K-values and different IMP and HxR contents for up to 7 days post mortem.     

Microwave drying of mango ginger (Curcuma amada Roxb): prediction of drying kinetics by mathematical modelling and artificial neural network

Curcuma amada (Mango ginger) was dried at four different power levels ranging 315–800 W to determine the effect of microwave power on moisture content, moisture ratio, drying rate, drying time and effective diffusivity. Among the fifteen thin layer drying models considered for evaluating the drying behaviour, the semi‐empirical Midilli et al., model described the drying kinetics very well with R² > 0.999. Drying rate and effective diffusivity increased as the microwave power output increased. Activation energy was estimated by a modified Arrhenius type equation and found to be 21.6 kW kg^?1. A feed‐forward artificial neural network using back‐propagation algorithm was also employed to predict the moisture content during MW drying and found adequate to predict the drying kinetics with R² of 0.985.     

贮藏期甜高粱形状与总糖含量的研究

甜高粱茎秆的贮藏关系到加工延长榨期,以达到糖分的充分利用。为延长甜高粱茎秆的贮藏期并确定最长存放时间,以新高粱9号(T601)茎秆收割后采取井型去叶去穗、带叶去穗堆放2种不同储存方式进行储藏试验,并研究了秸秆贮存过程中糖分、水分、湿度和温度等因素的变化规律。结果表明:甜高粱茎杆去叶去穗的各种贮藏方式温湿度都低于带叶去穗的各种贮藏方式,这样可以有效的减少霉变情况的产生,有利于贮藏。茎秆总糖含量与水分有密切的关系,糖分随着失水而升高,一般进入冻结期糖分上升速度减慢,解冻后又开始升高。根据各储藏方式对于秸秆形状变化可以初步确定,带叶去穗的贮藏方式最佳贮藏时间为2个月,而去叶去穗的贮藏方式能有效的延长贮藏期到5个月。     

对以甘油为增塑剂所制小麦面筋蛋白膜特性的研究

以小麦面筋蛋白(W G)为原料,研究了各因素对以甘油为增塑剂所制小麦面筋蛋白膜的各项性能(通透性、机械性能)的影响。基于本课题研究的重点,仅以面筋蛋白膜透水率为指标进行正交实验,最终得到最佳成膜条件分别为:谷朊粉/甘油4:1、乙醇浓度50%、反应温度50℃、透水率1.795×10-10g.m-1.s-1.Pa-1。