Time and speed of fruit drying on batch fluid-beds

Drying of particles (pieces) in a fluidized bed affords better quality of end products, especially for better product structure and its shorter reconstitution time. Fluid-bed drying of different fruit particles has been investigated. Starting water content varies from grape berries 81.5% and peach 87.7% to apricot 86.9%. The temperature of fluidization varies from 70°C to 100°C at air velocities from 0.98 ms⁻¹ to 5.2 ms⁻¹. The product should be dried fruit with 10% to 14% of water content with good rehydration quality that varies from 8 to 20. Experimental data have been measured, relevant values have been calculated and a mathematical model introduced. The results have shown that drying of fruit in a fluidized bed produces dry fruit particles of improved quality in a much shorter time, with improved rehydration times and qualities, than in continuous belt-driers that are generally used.     

Effects of processing on nutritional composition and quality evaluation of candied celeriac

In this work, a new candying procedure with partial re-use of sugar syrup is proposed. Physicochemical analysis, together with sensory evaluation, of candied celeriac samples was done. Candying was performed in a pilot unit at 65‡C, through three cycles of 5 hours duration each. Sugar syrups of 75‡ Brix were used. Effects of 1 % (m/v) citric and 1 % (m/v) ascorbic acid addition, as well as the drying of candied celeriac (60‡C for 8 h) were studied. Sugar syrup deterioration was estimated by the concentration of hydroxymethylfurfural. The results obtained showed that there were no significant(P < 0.01) differences in total dry matter and total sugar content between samples, while the increases after drying were significant(P > 0.01). Differences were observed in sugar compositions between samples. After three cycles, samples turned lighter, with decreasedL* values after drying. The celeriac from the first cycle of the ascorbic acid addition procedure was adjudged best with respect to all quality parameters. The decreased concentration of hydroxymethylfurfural confirmed that re-use of sugar syrup is possible.     

处理工艺对四种速冻蔬菜品质的影响

以加工后样品内维生素C(Vc)和可溶性固形物(total soluble solid,TSS)剩余含量为评价指标,分析速冻加工过程中切分大小、漂烫和速冻速率对速冻样品蔬菜(马铃薯、胡萝卜、西兰花和洋葱)品质的影响。研究结果表明:速冻速率在一定范围内对蔬菜Vc和TSS含量无明显影响;切块较大可有效保持蔬菜中的Vc和TSS;速冻前的漂烫过程明显增大了胡萝卜和洋葱Vc和TSS的损失,而马铃薯和西兰花则更适合于漂烫后再速冻的加工方式。     

Superplastic deformation of sheet test pieces machined from Ti-6Al-4V bar

Sheet tensile test pieces were machined in three orientations from edge textured Ti-6Al-4V bar and tested at temperatures in the range 800 to 975‡ C and at strain rates of 3 × 10⁻⁴ and 1.5×10⁻³ sec⁻¹. Bands of contiguous alpha grains aligned in the rolling direction caused local variations in the flow stress, strain to necking, strain rate sensitivity, plastic strain ratio values and surface roughness. Texture effects were only detected at the lowest test temperature (800‡C) and highest strain rate (1.5×10⁻³ sec⁻¹).     

Design and development of energy efficient solar tunnel dryer for industrial drying

A natural convection poly house walk-in type solar tunnel dryer was designed and used for drying surgical cotton on industrial scale. This article deals with the basic design criterion used for development of solar tunnel dryer and result of drying of surgical cotton in actual use. A batch of surgical cotton of 600 kg by mass, having an initial moisture content of 40% wet basis from which 210 kg of water is required to be removed to get a desired moisture content of about 5% wet basis, is used as the drying load in designing the dryer. A drying time of 7–8 h is assumed for the anticipated test location (Udaipur, 27° 42′ N, 75° 33′ E) with an expected average solar irradiance of 5.5 kW m⁻². Average cost of drying one batch of surgical cotton in a solar tunnel dryer has been worked out to be approximately 4.63 USD as compared to 30.00 USD in the existing diesel fired dryer.     

Thermal effects in model specimens under acoustic and convective actions

The temperatures of three model specimens placed in a nonheated air flow under convective and acoustic drying have been measured. It has been shown that in the dry specimens containing no water there occurs an appreciable heating of the internal region of the specimens by the acoustic field. The values of the moistureexchange coefficients of the specimens averaged over the drying period have been found. __________ Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 79, No. 2, pp. 168–173, March–April, 2006.     

Producing clean diesel fuel by co-hydrogenation of vegetable oil with gas oil

The goal of our investigation was the production of partially bio-derived fuels in the gas oil boiling point range. Our aim was the production of diesel fuel blending components by co-hydrogenation of mixtures of high-sulphur gas oil (about 1.0%) and vegetable oil raw materials with different vegetable oil contents (0, 5, 15, 25 and 100%). The experiments were carried out on a NiMo/Al₂O₃ catalyst with a targeted composition (T = 300–380°C, P = 60–80 bar, LHSV = 1.0/h and H₂/HC = 600 Nm³/m³). We obtained that both the vegetable oil conversion reactions and the gas oil quality improvement reactions took place. Under the favourable operational conditions (360–380°C, P = 80 bar, LHSV = 1.0/h and H₂/HC = 600 Nm³/m³ and up to 15% vegetable oil content of the feed), the main properties of the high-yield (>90%) products except for the Cold Filter Plugging Point (CFPP) value satisfied the requirements of the standard of diesel fuels (EN 590:2009). The amount of vegetable oil higher than 15% reduced the desulphurization efficiency, because of the intake of large quantities of oxygen with the triglyceride molecules of the vegetable oil. The products—depending on the vegetable oil content of the feedstocks—have an increased n- and i-paraffin content, so their combustion properties are very favourable, and the emission of particles is lower.     

Stress relaxation phenomena in vegetable tissue

The stress relaxation in some compressed vegetable fleshes, i.e. potato and kohlrabi tubers, and carrot and parsley roots, has been investigated. The relaxation curves obtained with different prestrain parts (different stress level and different prestrain rate) are approximated in the second part by simple equations, i.e. logarithmic and power equations. The similarity of these equations is demonstrated using similarly defined parameters: the initial slope of the relaxation curve and the time factor. The influence of prestrain on the strain relaxation is shown by the probability density of the decay processes. The activation volume was determined by two different methods: analysis of relaxation curves or/and by push change of the deformation rate. The second method gives systematically higher values than the first one. The activation volume strongly decreases with increasing stress, but only small differences in activation volumes were observed for different vegetable fleshes. The activation volumes between 50 and 110 nm^–3 are in a good agreement with the pore volume in the cell walls. The results obtained agree with the hypothesis of the controlling role of squeezing out of the cellular sap for stress relaxation in vegetable flesh.     

Physical properties of methyltrimethoxysilane based elastic silica aerogels prepared by the two-stage sol–gel process

The experimental results on the physical properties of methyltrimethoxysilane (MTMS) based elastic silica aerogels prepared by the two stage sol–gel process, are reported. The molar ratio of methanol (MeOH)/MTMS, (M), was varied from 14 to 42 and the molar ratios of acidic water/MTMS, (A) and basic water/MTMS, (B) were each varied from 0.8 to 7.2. The acidic water and basic water concentrations were also varied from 0–0.1 M and 6–13.36 M, respectively. The MTMS based superhydrophobic elastic aerogels could be obtained by adding only distilled water without an acid in the first step which would prevent the possible corrosion of the autoclave during the supercritical drying. With an increase in the MeOH/MTMS molar ratio, the aerogels have been found to become flexible which was characterized by the Young’s modulus. The best quality elastic superhydrophobic aerogels in terms of contact angle (160°), density (37 kg/m³), volume shrinkage (6%), porosity (98%) and thermal conductivity (0.057 Wm⁻¹ K⁻¹) have been obtained for the molar ratio of MTMS:MeOH:acidic water:basic water:: 1:35:3.97:3.97, respectively. The hydrophobicity was confirmed by Fourier Transform Infrared (FTIR) spectroscopy and contact angle measurements. The microstructure of the aerogels has been studied by the transmission electron microscopy (TEM).     

Drying of granular materials in circulating fluidized beds

It is attempted in the present investigation to dry solid materials in the riser of circulating fluidized bed covering a wide range of operating parameters. The effects of initial moisture content, temperature and flow rate of the heating medium, and solid circulation rate on rate of drying, have been critically examined. It has been observed that the solids material used in the present investigation exhibits a falling rate period, and the rate of drying is influenced by the temperature and flow rate of the heating medium, solids circulation rate and solid initial moisture content.     

A study on the dewatering of industrial waste sludge by fry-drying technology

In sludge treatment, drying sludge using typical technology with high water content to a water content of approximately 10% is always difficult because of adhesive characteristics of sludge. Many methods have been applied, including direct and indirect heat drying, but these approaches of reducing water content to below 40% after drying is very inefficient in energy utilization of drying sludge. In this study, fry-drying technology with a high heat transfer coefficient of approximately 500 W/m² °C was used to dry industrial wastewater sludge. Also waste oil was used in the fry-drying process, and because the oil's boiling point is between 240 and 340 °C and the specific heat is approximately 60% of that of water. In the fry-drying system, the sludge is input by molding it into a designated form after heating the waste oil at temperatures between 120 and 170 °C. At these temperatures, the heated oil rapidly evaporates the water contained in the sludge, leaving the oil itself. After approximately 10 min, the water content of the sludge was less than 10%, and its heating value surpassed 5300 kcal/kg. Indeed, this makes the organic sludge appropriate for use as a solid fuel. The wastewater sludge used in this study was the designated waste discharged from chemical, leather and plating plants. These samples varied in characteristics, especially with regard to heavy metal concentration. After drying the three kinds of wastewater sludge at oil temperatures 160 °C for 10 min, it was found that the water content in the sludge from the chemical, leather, and plating plants reduced from 80.0 to 5.5%, 81.6 to 1.0%, and 65.4 to 0.8%, respectively. Furthermore, the heat values of the sludge from the chemical, leather, and plating plants prior to fry-drying were 217, 264, and 428 kcal/kg, respectively. After drying, these values of sludge increased to 5317, 5983 and 6031 kcal/kg, respectively. The heavy metals detected in the sludge after drying were aluminum, lead, zinc, mercury, and cadmium. Most importantly, if the dried sludge is used as a solid fuel, these heavy metals can be collected from the dust collector after combustion.     

Mechanism of high-temperature oxidation of tin selenide

High-temperature oxidation of SnSe in the temperature interval 25 to 650‡ C has been studied by X-ray photoelectron spectroscopy, X-ray diffraction and thermal analysis techniques. Exposure to dry oxygen (760 torr pressure) at up to 200‡ C leads to the formation of SnO₂ on the surface. The high-temperature bulk oxidation between 250 and 650‡ C goes through distinct steps of formation of intermediate tin oxoselenides, presumably SnOSe or SnSeO₂ and its subsequent conversion to SnO₂.     

Reduction of sodium cyclotriphosphate by metallic molybdenum

The products of the reaction between sodium cyclotriphosphate and powder Mo in vacuum at temperatures up to 1000‡C were characterized by x-ray diffraction and³¹P nuclear magnetic resonance. Above 650–700‡C, the reaction yields MoP and amorphous sodium phosphates (orthophosphate, pyrophosphate, and cyclotetraphosphate) containing Mo in the oxidation state 5+. At the Mo content ensuring the largest percentage of sodium cyclotetraphosphate in the reaction products, these also contain a small amount of elemental phosphorus.     

添加剂对可食性蔬菜纸耐折度的影响

目的研究复合添加剂对可食性蔬菜纸耐折度的影响,以提高纸张的耐折度。方法以芹菜为基材,添加可食性的CMC、明胶和海藻酸钠作为粘结剂,甘油和山梨醇作为增塑剂,进行制浆、抄纸、干燥,制成可食性的芹菜纸,并对芹菜纸的耐折度进行测定,根据单因素实验结果,进行复合添加剂制备芹菜纸的实验,并建立回归方程,绘制响应面曲线和等高线,找出芹菜纸耐折度达到极值时的添加剂混合比例。结果当粘结剂质量分数为0.9%时,耐折度达到峰值6次,增塑剂质量分数为6%时,耐折度峰值为10次。当以质量分数分别为0.34%的CMC、0.40%的明胶和5.9%的甘油作为混合添加剂时,芹菜纸的耐折度可达到21次。结论复合添加剂的添加有效地提高了纸张的韧性,对改善纸张的耐折度起到了一定的作用。     

Impact strength of nylon 6 and 66 in the dry and moist states

The impact strength of nylon was determined by the modified Charpy test with double-V notches described in DIN 53753, because it cannot be reliably assessed by the notched Charpy and Izod tests. This test was adjusted to obtain a sensitive, accurate and reproducible method for the determination of impact strength in the dry and moist states. In the light of the criterion thus gained, it is shown that the dry “as-moulded” state is unstable and that the impact strength decreases exponentially with storage timE. Therefore, comparison tests are not valid unless the measurements are performed within a restricted period of time after the specimens had been demoulded. If the age of the specimens is unknown, a reproducible “as-moulded” state can be regenerated by an annealing procedure. The state of “conventional” moisture content that is taken as a reference for comparing data obtained on moist nylon is the equilibrium moisture content in a standard laboratory atmosphere. Various methods are discussed for attaining this state rapidly by accelerated conditioning. An atmosphere of 70‡ C and 62% relative humidity allows accurate adjustment to the “conventional” moisture content but does not result in a stable reference state; for instance, the impact strength decreases within several weeks after conditioning.     

Numerical analysis of drying characteristics of frozen material immersed in fluidized bed at low temperature under reduced pressure

A spherical frozen material was dried in a fluidized bed of inert particles at a low temperature (lower than the melting point of water) under reduced pressure. To evaluate the drying characteristics of the frozen material, the heat and mass transfers in the material during the drying process were calculated using one-dimensional differential equations. The fitting parameters (accommodation coefficient of internal sublimation and heat transfer coefficient at the surface of the material) were determined to fit the calculation results and the experimental data. Drying characteristics, such as the distributions of moisture content and temperature in the material during drying, were calculated. Operational conditions, such as bed temperature, humidity, and heat transfer coefficient (gas velocity) at the surface of the material were varied in the calculation, and the effects on the end time of drying were estimated. Sublimation in the interior of the material governs the drying characteristics. The dry region in the material became resistant to heat transfer. The calculation results are reasonable for expressing the drying characteristics of freeze-drying, that is, our calculation method can be used to estimate the drying characteristics of frozen material in a fluidized bed.     

Practical experiences of sensory investigations into the packaging of vegetables

The market for modified atmosphere foods continues to grow throughout Europe. This paper highlights some of the practical research studies carried out at the Campden Food and Drink Research Association during recent years. Vegetables referred to include potatoes, mushrooms, Brussels sprouts, calabrese, carrots, bean sprouts, watercress, diced onions, lettuce and mixed lettuce, and mixed vegetables. In all cases sensory evaluations of appearance were carried out on these vegetables packed in different atmospheres and in different packaging films, but only some results are included here in detail. Reference is made to a new industry guideline document for the good manufacturing and handling of modified atmosphere packed food products, and also to the use of active packaging.     

添加剂对可食用性芹菜包装纸机械性能的影响

为了研究添加剂对可食性蔬菜纸机械性能的影响,以芹菜为基材,CMC、明胶和海藻酸钠为黏结剂,甘油为增塑剂,通过制浆、抄纸、干燥,制成可食性芹菜包装纸,并对芹菜包装纸的机械性能进行测定。根据单因素实验结果,进行多因素实验分析,并建立回归方程,分析不同复合添加剂对包装纸抗张强度的影响,得到添加剂的最佳混合比例。实验结果表明：当CMC的添加质量分数为0.68%,明胶的添加质量分数为0.62%,甘油的添加质量分数为3.3%时,抗张强度取得最优值,为26.13 MPa。与单因素实验结果相比,复合添加剂的添加有效地提高了纸张的机械性能。     

壳聚糖/柠檬酸复合涂膜对胡萝卜的保鲜效果

目的研究壳聚糖和柠檬酸复合涂膜对胡萝卜保鲜效果的影响,为胡萝卜采后保鲜贮藏提供新途径。方法以胡萝卜为实验材料,采用壳聚糖(质量分数为1%)涂膜、壳聚糖(质量分数为1%)/柠檬酸(质量分数为1%)复合涂膜处理胡萝卜,以未涂膜处理的胡萝卜为空白对照,研究贮藏期间不同处理组胡萝卜的主要品质指标和生理活性随贮藏时间的变化情况。结果贮藏90 d后,复合涂膜处理组胡萝卜的呼吸强度为3.02 mg/(kg·h),质量损失率为3.32%,Vc含量为0.1704 mg/g,可溶性糖质量分数为2.08%,胡萝卜素含量为0.0549mg/g,POD活性为0.53U/g,PAL活性为65.87U/g,复合涂膜较单一涂膜更好地延缓了贮藏期间Vc含量、可溶性糖含量和胡萝卜素含量的下降,较好地保持了POD和PAL酶的活性。结论壳聚糖涂膜和壳聚糖/柠檬酸复合涂膜处理能够有效提高胡萝卜的贮藏品质,维持其生理活性,延缓衰老进程,其中,壳聚糖/柠檬酸复合涂膜处理的综合保鲜效果要优于单一壳聚糖涂膜处理。     

Influence of free water content on the compressive mechanical behaviour of cement mortar under high strain rate

The effect of free water content upon the compressive mechanical behaviour of cement mortar under high loading rate was studied. The uniaxial rapid compressive loading testing of a total of 30 specimens, nominally 37 mm in diameter and 18.5 mm in height, with five different saturations (0%, 25%, 50%, 75% and 100%, respectively) were executed in this paper. The technique ‘Split Hopkinson pressure bar’ (SHPB) was used. The impact velocity was 10 m/s with the corresponding strain rate as 10²/s. Water-cement ratio of 0.5 was used. The compressive behaviour of the materials was measured in terms of the maximum stress, Young’s modulus, critical strain at maximum stress and ultimate strain at failure. The data obtained from test indicates that the similarity exists in the shape of strain–stress curves of cement mortars with different water content, the upward section of the stress–strain curve shows bilinear characteristics, while the descending stage (softening state) is almost linear. The dynamic compressive strength of cement mortar increased with the decreasing of water content, the dynamic compressive strength of the saturated specimens was 23% lower than that of the totally dry specimens. With an increase in water content, the Young’s modulus first increases and then decreases, the Young’s modulus of the saturated specimens was 23% lower than that of the totally dry specimens. No significant changes occurred in the critical and ultimate strain value as the water content is changed.