Retention of the Enzymatic Activity and Product Properties During Spray Drying of Pineapple Stem Extract in Presence of Maltodextrin

The aim of this work was to investigate the effects of drying parameters on the retention of the enzymatic activity and on the physical properties of spray-dried pineapple stem extract. A Box and Behnken experimental design was used to investigate the effects of the processing parameters on the product properties. The parameters studied were the inlet temperature of drying gas (Tgi), the feed flow rate of the pineapple extract relative to evaporative capacity of the system (W_s?/W_max), and the concentration of maltodextrin added to the extract (MD). Significant effects of the processing parameters on the retention of the proteolytic activity of the powdered extract were observed. High processing temperatures lead to a product with a smaller moisture content, particle size, and lower agglomerating tendency. A product with insignificant losses of the proteolytic activity (≈ 10%) and low moisture content (less than 6.5%) is obtained at selected conditions.     

Moisture Diffusivity in High Oleic Sunflower Seeds and Kernels

Moisture diffusivities in high oleic seeds and kernels were obtained from experimental thin layer drying rates in the range of 25–90°C air temperature and 4.2–33.5% initial moisture content (d.b.). Moisture diffusivity back-calculated from Fick´s second law of diffusion varied between 0.85.10^-10 and 7.26.10^?10 m²/s for seeds and between 0.37.10^?10 and 2.39.10^?10 m²/s for kernels. The Arrhenius activation energy for seeds and kernels resulted 31 and 24 kJ/mol, respectively. A new model based on the kinetic parameter of Page equation was proposed as a simple tool to predict water diffusion in high oleic sunflower seeds and kernelss.     

Moisture Diffusivity Determination of Different Parts of Longan Fruit

The components of the longan fruit were modeled as sphere for seed, cylinder for seed stalk, and slab for seed coat, shell, and flesh. The moisture diffusivities were determined by minimizing the sum of square of derivations between the predicted and experimental values of moisture content of thin layer drying under controlled conditions of air temperature and relative humidity. Experimental data were obtained from thin layer drying of the components in the form of sphere for seed, cylinder for seed stalk and slab for seed coat, shell and flesh. Air temperatures of 50, 60, 70, and 80°C and relative humidity in the range of 1.5–13.33% were used. The mean diffusivity of flesh of longan fruit increased with temperature, but the diffusivities of shell, seed coat, seed, and seed stalk were independent of temperature. The moisture diffusivities of shell and seed coat were much lower than those of the other parts of the longan.     

Influence of Moisture Content and Temperature on Thermal Conductivity and Thermal Diffusivity of Rice Flours

The thermal conductivity and thermal diffusivity for four types of rice flours and one type of rice protein were determined at temperatures ranging from 4.8 to 36.8?°C, bulk densities 535 to 875.8 kg m^?3, and moisture contents 2.6 to 16.7% (w.b.), using a KD2 Thermal Properties Analyzer. The thermal conductivity of rice flours and rice protein increased with the increase in temperature, moisture content as well as with increase in bulk density. Thermal diffusivity decreased with increase in moisture content, increase in temperature and bulk density. The thermal conductivities values obtained were within the range of 0.045 to 0.124 W m^?1 K^?1 whereas the thermal diffusivity values were in the range of 0.094 to 0.138 mm² s^?1.     

Optimization of Maltodextrin and Tricalcium Phosphate for Producing Vacuum Dried Mango Powder

Drying of mango pulp into powder is a challenging operation, mainly due to the sticky issue of mango powder in the dryer and caking during handling and storage. To overcome the above problem, maltodextrin, MD (drying aid) and Tricalcium Phosphate, TCP (anti caking agent) were added to the mango pulp at three levels and vacuum dried. The dried powder was analysed for properties such as hygroscopicity, degree of caking, flowability and sticky point temperature. Factorial design of experiment was used to investigate the effect of MD and TCP on the mango powder properties. The amount of MD and TCP required to reduce powder stickiness and caking were optimized based on the powder properties. At the optimum amount of MD (0.527 kg per kg dry mango solid) and TCP (0.0167 kg per kg dry mango solid), the values of mango powder properties were: hygroscopicity = 6.4 %; degree of caking = 7.8%; flowability = 18.6 s; sticky point temperature = 47.4°C.     

果胶酶和壳聚糖对菠萝汁澄清作用的比较研究

本文研究比较了果胶酶和壳聚糖对菠萝汁的澄清方法,并确定了各自的最佳工艺参数,果胶酶法:果胶酶100mg/kg,pH3,温度40;壳聚糖法:0.6g/L,pH3,温度40。从澄清效果和贮存稳定性看,两种方法都能很好的澄清菠萝汁;从总体成本看,壳聚糖法明显优于果胶酶法,其贮藏时间长,成本低,易控制,是较好的澄清剂。     

Modeling Effective Moisture Diffusivity of Wheat (Tajan) During Air Drying

Drying conditions can greatly affect the physical and mechanical properties of grains. The drying process must be controlled to reduce or minimize drying damage. In this paper the thin layer drying behavior of wheat (Tajan) in a convective dryer is experimentally investigated. The mathematical modeling by using thin layer kinetics drying models available in literature was performed. Drying experiments were conducted at inlet drying air temperatures of 35, 45, 50, 60 and 70°C and at a fixed drying air velocity of 0.3 m/s and initial moisture content of 0.26–0.27 (d.b.). The effects of drying air temperature on the model's parameters were predicted by a linear regression analysis. The constants and coefficients of this model were be explained in terms of drying air temperature. A correlation coefficient (r) of 0.99 was found for the multiple regression model of moisture content during the drying process using different temperature values. Values of the diffusion coefficients for the whole kernel ranged from 2.28 × 10^?11 to 1.14 × 10^?10 m²/s.     

猪、牛、羊革的特征与鉴别

用光学显微镜观察分析了猪、牛、羊革的微观形态特征,形成了特征图片,为质检工作者进行皮革材质鉴定提供参考。     

Diffusivity,shrinkage and simulated drying of litchi fruit (Litchi Chinensis Sonn.)

Litchi (Litchi Chinensis Sonn.) is an important commercial fruit in Thailand and Vietnam. Litchi fruit is consumed both as fresh and dried products. Also most of the export of litchi is in the form of dried whole litchi fruit. Thermo-physical properties and drying model of litchi fruit is important for optimum design of litchi dryer. This paper presents moisture diffusivity, shrinkage and finite element simulated drying of litchi fruit. The moisture diffusivities of litchi were determined by minimizing the sum of square of deviations between the predicted and experimental values of moisture content of thin layer drying under controlled conditions of air temperature and relative humidity. The components in the form of cylinder for seed and seed stalk and slab for seed coat, shell and flesh were dried in thin layers at the air temperatures of 50, 60, 70 and 80 °C and relative humidity in the range of 10–25%. The mean diffusivity of flesh, seed and shell of litchi fruit increased with temperature and was expressed by the Arrhenius-type equation, but the diffusivities of seed coat and seed stalk were independent of temperature. The moisture diffusivities of seed coat and seed stalk were much lower than those of the other parts of the litchi. The shrinkage of litchi fruit has also been determined experimentally and it was expressed as a function of moisture reduction. A two-dimensional finite element model has been developed to simulate moisture diffusion in litchi fruit during drying. Shrinkage of the flesh and different component diffusivities of litchi during drying were also taken into account. The finite element model was programmed in Compaq Visual FORTRAN version 6.5. This finite element model satisfactorily predicts the moisture diffusion during drying. Moisture contents in the different components in the litchi fruit during drying were also simulated. This study provides an understanding of the transport processes in the different components of the litchi fruit.     

Changes in Temperature and Structure of Agar Gel as Affected by Sucrose During High-pressure Freezing

ABSTRACT: To determine the effects of high-pressure freezing, agar gel with 0, 5, 10, or 20% sucrose were frozen at 0.1 to about 686 MPa and -20 °C. Exothermic peaks were detected at 0.1, 100, 500 to about 686 MPa (freezing). However, at approximately 200 to 400 MPa, gel did not freeze but froze during pressure release. Thus, structure of gel frozen at approximately 200 to 400 MPa was better than other samples due to quick freezing. The phase transition from high-pressure-ices to ice I at -20 °C might have promoted the growth of ice crystals. With the addition of sucrose, the initial freezing temperature decreased and structural quality improved. Keywords: high pressure, agar gel, freezing, texture, ice crystals     

皮革生产过程中主要污染物的处理与控制

制革过程尤其是从原料皮到半成品革是一个多工序的过程,制革工序中的每一步产生的污染物或多或少都会给环境和操作人员带来危害。本文介绍了皮革生产过程中主要污染物控制方法,无论是对环境和工人安全,还是对皮革工业的发展来说,都是非常有必要的。     

皮革切削力矩的测试分析——制革刀轴类机器参数研究之二

在削匀机的动力分析,刀辊设计等问题中,切削力矩是个非常重要的量,它不仅受机器本身结构的影响,而且还与被削皮革的性状有关。本文通过大量的实验,比较深入地研究了削匀机切削不同的皮革时,刀辊切削力矩的变化过程以及它们同皮革削匀量之间的关系。同时也从机器运动学和动力学的角度对“跳刀”问题作了一定的分析研究。此外,本文还提出了切削过程中皮革被挤压时“临界压缩度”的概念并给出它与皮革厚度之间的关系。     

Mathematical Evaluation of Effective Moisture Diffusivity in Fresh Japanese Noodles (Udon) by Regular Regime Theory

The effect of moisture content and temperature on the effective moisture diffusivity was investigated to have the optimal drying condition of Japanese noodles (Udon) using regular regime theory. The drying of fresh Udon of different moisture contents was carried out under constant conditions of relative humidity and airflow at 20, 30, and 40 °C. The existence of regular regime periods for fresh noodles was experimentally verified. Effective moisture diffusivity obtained ranged from 2.1 × 10 ^-7 to 3.7 × 10 ^-7 cm² s^-1. The effect of temperature on effective moisture diffusivity was adequately modeled by the Arrhenius relationship, although the effect of moisture content was quite small.     

变温压差膨化干燥对芒果品质的影响

以凯特芒果为原料,采用变温压差膨化干燥技术,探讨了切条厚度、预干燥后水分含量、膨化温度、膨化压力差、抽空温度、抽空时间和停滞时间对芒果膨化产品的硬度、脆度、色泽、膨化度和含水率的影响.结果表明:芒果膨化的最佳厚度为6 mm;预干燥后水分含量、膨化温度和抽空时间是影响芒果膨化产品品质的关键因素;预干燥后,含水量在61.7...     

滚筒干燥过程中叶丝状态变化对其热物性的影响

为了分析烟草热湿加工处理中的传热过程,通过自行搭建的滚筒干燥过程中烟丝热物性在线测试平台,利用瞬态平面热源法测定了滚筒干燥过程中烟丝的热物性,考察分析了该过程中烟丝温度、含水率对烟丝导热系数、热扩散系数、体积热容的影响。结果表明:①当含水率相同时,烟丝导热系数、体积热容随着烟丝温度的升高而增大,热扩散系数随温度的升高而降低;②当烟丝温度相同时,烟丝导热系数、体积热容随含水率的降低而减小,热扩散系数随着含水率的降低而增大;③干燥过程中,烟丝含水率逐渐减小,烟丝温度逐渐升高,烟丝导热系数在温度与含水率的共同作用下整体有减小的趋势,表明烟丝含水率对导热系数的影响较温度显著。     

ICP-AES测定皮革及其制品中的可溶性重金属含量

建立了酸性汗液振荡提取-电感耦合等离子体发射光谱法同时测定皮革及其制品中As、Cd、Cr、Hg、Pb、Sb、Se、Ni等重金属可溶性含量的方法。研究了测试的仪器工作条件及共存离子的干扰等因素。在试验选定的最佳条件下,各元素的线性相关系数均≥0.999,方法检出限在0.010～0.050mg/kg之间,皮革样品中不同浓度加标回收率为95.6%～105.4%,相对标准偏差小于3.8%。本方法准确快速、检测限低、线性范围宽,可同时测定多种元素,可用于测定皮革中可溶性重金属含量。     

Thermal Properties of Ration Components as Affected by Moisture Content and Water Activity During Freezing

ABSTRACT: Beef roast with vegetables is an example of a meal, ready‐to‐eat (MRE) ration entrée. It is a mixture of meat, potato, mushroom, and carrot with a gravy sauce. The thermal properties of each component were characterized in terms of freezing point, latent heat, freezable and unfreezable water contents, and enthalpy during freezing using differential scanning calorimetry. Freezing and thawing curves and the effect of freezing and thawing cycles on thermal properties were also evaluated. The freezing points of beef, potato, mushroom, and sauce were all in the range of −5.1 to −5.6 °C, but moisture content, water activity, latent heat, freezable and unfreezable water contents, and enthalpy varied among these components. Freezing temperature greatly affected the unfrozen water fraction. The unfreezable water content (unfrozen water fraction at −50 °C) of ration components was in the range of 8.2% to 9.7%. The freezing and thawing curves of vegetables with sauce differed from those of beef but took similar time to freeze or thaw. Freezing and thawing cycles did not greatly affect the thermal properties of each component. Freezing point and latent heat were reduced by decreasing moisture content and water activity of each component. Water activity was proportionally linear to freezing point at a_w > 0.88, and moisture content was proportionally linear to freezable water content in all ration components. Water was not available for freezing when moisture content was reduced to 28.8% or less. This study indicates that moisture content and water activity are critical factors affecting thermal behavior of ration components during freezing.     

改善合成革吸湿透气性能的研究

目前在合成革领域亟待解决的问题就是合成革在吸湿透气方面与天然革的差距还比较明显。本文对非离子聚氨酯干法面层的吸湿透气行为进行了研究。讨论了非离子共聚组分的引入对聚氨酯合成革吸湿透气行为的影响。结果表明亲水基团PEG的引入可以提高合成革吸湿透气性能。并且微相分离大的吸湿透气性能差。     

Strawberry Texture and Pectin Content as Affected by Electron Beam Irradiation

Fresh Tristar' strawberries were irradiated with electron beam irradiation at 0, 1, and 2 kGy. Fruit firmness decreased as irradiation dose increased. Water-soluble pectin increased and oxalate-soluble pectin decreased at 0 and 1 day after 1 and 2 kGy irradiation. Fruit firmness correlated with oxalate-soluble pectin content. Total pectin and nonextractable pectin were not affected by irradiation. The oxalate-soluble pectin content and firmness of irradiated strawberries increased slightly at the beginning of 2°C storage and then decreased as storage time increased. No changes occurred in water-soluble pectin, nonextractable pectin, or total pectin during storage.     

棉织物干燥过程热湿传递特性软件计算与分析

以单层多孔薄棉织物为对象,分析并建立其热风干燥过程中的热质传递机理及数学模型,得到织物在烘干过程中含水率与温度的变化规律,并采用MATLAB APP designer设计了棉织物传热传质数值计算软件,简易又直观地显示了各干燥段干燥时间与温湿度变化曲线。结果表明,薄棉织物在干燥过程中,内部温度与含水率的梯度基本可忽略不计,薄棉织物恒速段干燥时间占总时间的70%以上,但在结束恒速干燥段后内部仍有一定的吸附水含量。可为印染热定形机的风道结构设计和棉织物热定形工艺参数的设定提供理论参考价值。