Drying kinetics of whole durum wheat pasta according to temperature and relative humidity

Drying kinetics of bran-free and bran-rich pasta (whole durum) was determined according to temperature (40, 60 or 80 °C) and relative humidity (65%, 75% or 85%). Compared to temperature, relative humidity in drying chamber had a greater effect on pasta effective moisture diffusivity (α<0.01), and both parameters responded to a modified Arrhenius-type equation. Activation energy of pasta (11.4 kJ mol⁻¹) was lower than reported in the literature. Bran changed the course of pasta drying, depending on temperature and relative humidity. When relative humidity was higher than 75%, effective moisture diffusivity of bran-rich pasta decreased but the reverse was observed below 75%. Above 76 °C, equilibrium moisture content of bran-rich pasta was higher than bran-free pasta. In conclusion, optimal drying conditions for bran-rich pasta were different than standard (bran-free) pasta. Close control of relative humidity in pasta drying unit would be critical, especially under high relative humidity and high temperature conditions.     

Sensitivity analysis of parameters affecting the drying behaviour of durum wheat pasta

In this work, a comprehensive model of pasta drying combining Neumann boundary conditions, differential shrinkage and with consideration of the constant drying rate period and falling drying rate period was investigated through sensitivity and uncertainty analysis. Results confirmed that shrinkage, moisture loss and drying rate during the constant drying rate period and external resistance to mass transfer did not have a significant impact on the predicted required drying time. The predicted required drying time was influenced predominantly by the effective moisture diffusion coefficient. A correlation to estimate the effective moisture diffusion coefficient was developed from published values and was used to predict the required drying time with an uncertainty of ±3.5 h at a 90% confidence interval. Since this magnitude of uncertainty is unreasonable for most industrial uses, accurate data collection of effective moisture diffusivity should be viewed as a major objective in pasta drying research.     

Shrinkage,porosity and density behaviour during convective drying of spirulina

Spirulina (Arthrospira platensis) is a microalgae produced for its nutritional and therapeutic qualities. Drying is the main process of conservation used for this product and it is so essential to control its drying parameters. In this study, shrinkage, porosity and density of spirulina cylinders during convective drying were investigated. For 3, 4 and 6 mm diameter cylinders, results showed a weak and anisotropic shrinkage. The glass nature of the product during the drying process tended to reduce its shrinkage and to facilitate formation of pores and cracks. The product had a final porosity approaching 80% and most of its evaporated water during drying was replaced by gas. The apparent density strongly varied during drying. Its value decreased from 850 kg/m³ at the beginning of the drying to about 300 kg/m³ at the end of the drying. The effective water diffusivity was influenced by shrinkage. Its value was over-estimated about 36.48% to 92.41% when shrinkage was not considered in data processing.     

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.     

Kinetic modelling of drying and conversion/degradation of isoflavones during infrared drying of soybean

Soy isoflavones, which are well-known for their health benefits, could be affected by the technique and condition that are used to dry soybean prior to its use. In this study the drying kinetics of soybean as well as the inter-conversion and degradation of soy isoflavones during gas-fired infrared combined with hot air vibrating drying (GFIR–HAVD) at various temperatures (50, 70, 130 and 150 °C) were investigated. Simple kinetic models for the evolutions of both moisture content and isoflavones were proposed and tested. The temperature dependency of the effective moisture diffusivity of soybean could be well described by the Arrhenius correlation with the activation energy of 13.88 kJ/mol. In terms of the evolutions of isoflavones the contents of 6″-O-malonylgenistin (MGI) and 6″-O-acetylgenistin (AGI) decreased, while genistin (GI) and genistein increased with an increase in the drying temperature and drying time. First-order kinetic models could be used to describe the changes of isoflavones. At all drying temperatures the conversion of MGI to GI exhibited the highest rate constant; this was followed by the conversion of AGI to GI. In addition, MGI had the highest degradation rate constant; this was followed, in descending order, by AGI, GI and GE. The activation energies of degradation were lower than those of inter-conversion among all forms of isoflavones.     

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.     

干燥方式对pH改性豌豆分离蛋白功能性和结构的影响

以豌豆为原料制备豌豆分离蛋白(PPI),比较了常用的两种干燥方式对pH改性PPI功能性的影响,并利用SDS-PAGE和红外光谱法研究了两种干燥方式对pH改性PPI结构的影响。研究结果表明:与冷冻干燥相比,喷雾干燥使改性处理后的PPI形成较多聚集体,同时使蛋白质的功能性质(溶解性、乳化性、胶凝性)略微降低;经过pH改性处理喷雾干燥PPI的乳化性和胶凝性显著高于未改性处理冷冻干燥PPI,喷雾干燥后PPI亚基发生更多的非二硫键共价聚集,使PPI发生部分变性,二级结构发生了变化。总之,喷雾干燥对PPI的功能性质有降低趋势,而pH改性处理可以大大改善PPI的功能性质从而弥补喷雾干燥带来的不足。     

Mass transfer characteristics during convective,microwave and combined microwave–convective drying of lemon slices

BACKGROUND: The investigation of drying kinetics and mass transfer phenomena is important for selecting optimum operating conditions, and obtaining a high quality dried product. Two analytical models, conventional solution of the diffusion equation and the Dincer and Dost model, were used to investigate mass transfer characteristics during combined microwave‐convective drying of lemon slices. Air temperatures of 50, 55 and 60 °C, and specific microwave powers of 0.97 and 2.04 W g^?1 were the process variables. RESULTS: Kinetics curves for drying indicated one constant rate period followed by one falling rate period in convective and microwave drying methods, and only one falling rate period with the exception of a very short accelerating period at the beginning of microwave‐convective treatments. Applying the conventional method, the effective moisture diffusivity varied from 2.4 × 10^?11 to 1.2 × 10^?9 m² s^?1. The Biot number, the moisture transfer coefficient, and the moisture diffusivity, respectively in the ranges of 0.2 to 3.0 (indicating simultaneous internal and external mass transfer control), 3.7 × 10^?8 to 4.3 × 10^?6 m s^?1, and 2.2 × 10^?10 to 4.2 × 10^?9 m² s^?1 were also determined using the Dincer and Dost model. CONCLUSIONS: The higher degree of prediction accuracy was achieved by using the Dincer and Dost model for all treatments. Therefore, this model could be applied as an effective tool for predicting mass transfer characteristics during the drying of lemon slices. © 2012 Society of Chemical Industry     

Composition,physicochemical properties of pea protein and its application in functional foods

Abstract

Field pea is one of the most important leguminous crops over the world. Pea protein is a relatively new type of plant proteins and has been used as a functional ingredient in global food industry. Pea protein includes four major classes (globulin, albumin, prolamin, and glutelin), in which globulin and albumin are major storage proteins in pea seeds. Globulin is soluble in salt solutions and can be further classified into legumin and vicilin. Albumin is soluble in water and regarded as metabolic and enzymatic proteins with cytosolic functions. Pea protein has a well-balanced amino acid profile with high level of lysine. The composition and structure of pea protein, as well as the processing conditions, significantly affect its physical and chemical properties, such as hydration, rheological characteristics, and surface characteristics. With its availability, low cost, nutritional values and health benefits, pea protein can be used as a novel and effective alternative to substitute for soybean or animal proteins in functional food applications.     

The effect of protein types and low molecular weight surfactants on spray drying of sugar-rich foods

The effect of protein types and low molecular weight surfactants (LMS) on spray drying of sugar-rich foods has been studied using sucrose as a model sugar and sodium caseinate (NaCas) and pea protein isolate (PPI) as model proteins. Sodium stearoyl lactylate (SSL) and Polysorbate 80 (Tween-80) were chosen as model ionic and non-ionic LMS. The sucrose:NaCas and sucrose:PPI solid ratios were maintained at (99.5:0.5) and (99:1), respectively and spray-dried maintaining 25% solids in feed solutions. It was found that the proteins preferentially migrated to the air–water interface reasonably swiftly and the addition of LMS resulted into partial or complete displacement of the proteins from the air–water interface. More than 80% of amorphous sucrose powder was produced with the addition of 0.13% (w/w) of NaCas in feed solution. PPI was not as effective and produced less than 50% recovery even at 0.26% (w/w) in feed. Addition of 0.01–0.05% SSL displaced 2.0% and 29.3% of proteins from the surface of sucrose–NaCas–SSL droplet, respectively, resulting in a 6.5 ± 1.2% to 51.9 ± 1.9% reduction in powder recovery. The extent of protein displacement was higher when SSL was added into sucrose–PPI solution; however, the powder recovery was not much affected. The addition of 0.01% Tween-80 in sucrose–NaCas solution resulted in a 48.2 ± 1.5% reduction in powder recovery and at 0.05% concentration, it displaced a substantial amount or all the NaCas from the droplet surface and no powder was recovered. The addition of 0.01% and 0.05% Tween-80 into sucrose–PPI solution resulted into very low powder recoveries (24.9 ± 0.4% and 29.5 ± 1.8%, respectively). The glass transition temperature (T_g) results revealed that the amount of protein required for successful spray drying of sucrose–protein solutions depends on the amount of proteins present on the droplet surface but not on the bulk concentration. X-ray diffraction and scanning electron microscopy results showed that the powders of sucrose–NaCas/PPI and sucrose–NaCas/PPI with 0.01% SSL were mostly amorphous while those with sucrose–NaCas/PPI–Tween-80 (0.01%), sucrose–PPI–Tween-80 (0.05%) and sucrose–NaCas/PPI–SSL (0.05%) were crystalline.     

Shrinkage, density, porosity and shape changes during dehydration of pumpkin (Cucurbita pepo L.) fruits

The aim of this work was to study the changes in volume, density, porosity and shape factors of pumpkin tissue during osmotic dehydration (OD) and air drying (AD). Pumpkin cylinders with length/diameter ratio of 5/3 were used. OD experiments were carried out with solutions of sucrose, sodium chloride and mixtures of both solutes at different temperatures. AD experiments were conducted at 70 °C. Volume of samples decreased linearly with weight reduction (WR). Bulk density varied in a restricted range (5-13%) during dehydration and for all the methods maximum values were found. Particle density increased during both processes. Porosity increased at advanced degrees of dehydration, showing a minimum value at the beginning of OD and AD. The proposed models to evaluate shrinkage, bulk and particle densities and porosity from WR were satisfactorily applied. Image analysis showed that shrinkage of samples during OD was isotropic. Pumpkin cylinders increased elongation and decreased roundness and compactness during osmotic dehydration.     

Effects of spray drying conditions and the addition of surfactants on the foaming properties of a whey protein concentrate

Whey is the main waste by-product from dairy industry and at the same time is the major source of globular proteins. These proteins are concentrated mainly through spray drying, but high temperatures affect the foaming properties of globular protein. The addition of surfactants can have a protective role against thermal effects. The aim of this work was to optimize the spray-drying condition and surfactant concentration to obtain a whey protein concentrate (WPC) to be used in hot beverages according to the industry criteria for foaming stability. Three temperatures and three surfactant concentrations were applied, and the optimization was conducted using response surface analysis. Sensory analysis was applied to the WPC obtained under optimal conditions. The results showed that the foaming stability according to industrial criteria was attained when the spray drying was performed at 210 °C with surfactant concentration of 1.50 g/100 g. This resulted in foaming capacity of 3.80 mL, moisture content of 1.82 g/100 g and apparent density of 0.181 g/cm³. The sensory analysis suggested that aroma was related to dairy, cooked and whey and taste was related to sweet and dairy notes. In conclusion, temperature and surfactant concentration played an important role in the foaming capacity and stability of WPC.     

Effect of drying and proline addition on aroma volatile compounds of acid‐hydrolysed rice bran protein concentrate

Rice bran protein concentrate (RBPc) was hydrolysed by 0.5 N aqueous HCl at 95 °C for 12 h. The liquid hydrolysate obtained was prepared as hydrolysate powder by spray drying. Aroma volatile compounds in liquid hydrolysate and its hydrolysate powder were tentatively identified by GC‐MS. Furfural and vanillin were found in both hydrolysates with high concentration, and vanillin showed the highest odour activity value. Hexanal was present in only liquid hydrolysate. Concentrations of carboxylic acids and heterocyclic compounds, especially 2‐methoxy‐6‐methylpyrazine, increased after drying. Amino acid composition of the hydrolysate powder showed high aspartic acid and glutamic acid. Aroma volatile compounds of hydrolysate powder prepared by the addition of proline at pH 6.0 (Pro6.0‐H) and pH 7.5 (Pro7.5‐H) before drying were investigated. Furaneol was found only in Pro6.0‐H, but it was not detected in Pro7.5‐H and hydrolysate powder without proline addition. Pro7.5‐H had higher furfural and vanillin concentrations than Pro6.0‐H.     

Potential sources of mouth drying in beverages fortified with dairy proteins: A comparison of casein- and whey-rich ingredients

Oral nutritional supplement drinks (ONS) are beverages high in dairy proteins that are prescribed to individuals at risk of malnutrition. Consumption of ONS is poor in elderly care facilities, with patients commenting that the sensory attributes of these drinks reduce their enjoyment and willingness to consume. Mouth drying is an attribute of ONS found to build with repeated consumption, which may further limit liking of these products. This study investigated the sources of drying sensations by sequential profiling, with a trained sensory panel rating a range of model milk systems and ONS over repeated sips and during after-effects. Sequential profiling found that fortification of milk with both caseinate and whey protein concentrate significantly increased the perception of mouth drying over repeated consumption, increasing by between 35 and 85% over consumption of 40 mL. Enrichment of ONS with either whey protein concentrate or milk protein concentrate to a total protein content of 8.7% (wt/wt) resulted in whey and casein levels of 4.3:4.4% and 1.7:7.0% respectively. The product higher in whey protein was substantially more mouth drying, implying that whey proteins may be the most important contributor to mouth drying in ONS. However, efforts to mask mouth drying of protein-fortified milk by increasing sweetness or fat level were unsuccessful at the levels tested. Increasing the viscosity of protein-fortified milk led to a small but significant reduction in mouth drying. However, this approach was not successful when tested within complete ONS. Further analysis is required into the mechanism of protein-derived mouth drying to mask negative sensations and improve the enjoyment and consumption of protein-rich ONS.     

Effect of whey and pea protein blends on the rheological and sensory properties of protein-based systems flavoured with cocoa

Whey and pea protein combined in different proportions (100W:0P, 75W:25P, 50W:50P, 25W:75P, 0W:100P) were used to prepare protein-based systems flavoured with cocoa and containing κ-carrageenan or κ-carrageenan/xanthan gum as thickeners. Steady and dynamic shear rheological properties of samples were measured at 10 °C and sensory differences were evaluated. Protein-based systems exhibited a shear-thinning flow behaviour that was fitted to the simplified Carreau model. Samples showed different viscoelastic properties, ranging from fluid-like to weak gel behaviour. For both types of system (with and without xanthan gum) viscosity, pseudoplasticity and elasticity rose on increasing the pea protein proportion in the blend. The sample with only whey protein obeyed the Cox-Merz rule, while in the rest of the samples complex viscosity was higher than apparent viscosity. Regarding sensory properties, the protein blend ratio mainly affected sample thickness, which rose as pea protein proportion increased. However, at the same time, the chocolate flavour and sweetness decreased and the off-flavour increased.     

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。     

Chemical,textural, rheological,and sensorial properties of wheyless feta cheese as influenced by replacement of milk protein concentrate with pea protein isolate

Replacement of milk protein with protein isolates from vegetable resources can significantly influence the characteristics of feta whey less cheese and also decrease the cost of final production. In this study, various blends of milk protein concentrate (MPC) and pea protein isolate (PPI) were mixed at levels of 12% MPC and 0% PPI (MP0), 10% MPC and 2% PPI (MP2), 9% MPC and 3% PPI (MP3), 8% MPC and 4% PPI (MP4), 7% MPC and 5% PPI (MP5), 6% MPC and 6% PPI (MP6) and used in the manufacture of wheyless feta cheese. The chemical, textural, rheological, and sensorial properties, as well as the microstructure of the cheese samples, were evaluated after 1, 15, and 30 days of storage. The general linear model procedure of SAS statistical software was used for statistical analysis. Duncan's multiple range tests was used to compare the means of different treatments. The results showed that all properties of the cheeses were influenced by different levels of PPI due to different total solids content. The use of high concentrations of PPI resulted in a more open protein network, softer structure and decreasing the storage (G′) and loss (G″) moduli in the cheeses. Sensory evaluation of the samples revealed that total score in terms of flavor, texture and overall acceptability was gradually decreased with increasing PPI levels, but still preferable for the panelists. Furthermore, for each sample, with increasing levels of PPI, the whiteness and the greenness were decreased, but the yellowness was increased.     

Effects of plasticizers, pH and heating of film-forming solution on the properties of pea protein isolate films

Effects of glycerol (3-7% w/w) and sorbitol (4-8% w/w) concentration, pH (7.0, 9.0, 11.0) and heating (90 °C, 20 min) of film-forming solution (FFS) on the water vapor permeability (WVP), moisture content (MC), solubility, light transmission and transparency of pea protein isolate (PPI) films were investigated. Films plasticized with sorbitol exhibited significantly lower WVP, lower MC and higher solubility, in comparison with glycerol-plasticized films. Increasing glycerol content of the films led to increases in WVP and MC but did not affect film solubility. In contrast, increase in sorbitol content had no effect on permeability and MC but resulted in increased film solubility. Moisture sorption isotherms of PPI films suggested that the difference in WVP observed among films plasticized with glycerol and sorbitol might be due to the different hygroscopicity of these plasticizers. The pH of FFS did not have a significant effect on WVP and MC. Solubility of PPI films formed from non-heated FFS was not affected by pH, whereas solubility of films formed from heat-treated FFS generally increased when pH was increased from 7.0 to 11.0. Heating of FFS resulted in improved film transparency. All tested films were characterized by excellent ability to absorb UV radiation. Microstructural observation by scanning electron microscopy did not show differences between sorbitol- and glycerol-plasticized films.     

5000 t/a大豆分离蛋白喷雾干燥塔的设计及结构

喷雾干燥是生产大豆分离蛋白的一种常用的干燥方式,喷雾干燥的效果直接决定最终产品的质量和功能性。喷雾干燥塔的设计制作、结构是否合理至关重要,是保证喷雾干燥效果的前提。详细介绍了5 000 t/a大豆分离蛋白喷雾干燥塔的设计计算、喷雾干燥塔的结构、附属设备的相关工艺参数;喷雾干燥塔的结构主要包括热风分布器、雾化器、塔体、清扫粉装置等,为5 000 t/a大豆分离蛋白喷雾干燥塔的设计、制作提供了参考。