摘要:

Round slices (2 mm thick) of fresh apple and of apple subjected to osmo-dehydration processes in sucrose syrups until reaching awvalues of 0.979, 0.968. and 0.958. were air-dried at 50. 60. and 70°C. Analysis of the drying curves showed that the products do not present a constant rate period (except for fresh apple) but showed two falling rate periods. Initial awgreatly affects the fraction of water lost during the drying processes. The use of the Fick's Second Law was not adequate to describe the experimental drying curves. However, apple drying processes can be modeled by the Characteristic Drying Curve model, using several equations (polynomial and logarithmic) with a high confidence level. The parameters of each equation showed a great dependence on product's awThese models can be used to predict drying curves within the studied limits in each case, presenting great advantages when compared to classical models based on effective diffusion coefficients.

ISSN:0737-3937    

DOI:10.1080/07373939708917270

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

The influence of the drying conditions on the oxidation state of the lipidic fraction in hazelnut (Corylus avellana, L.) has been studied. Different hazelnut quality parameters (acidity index, KZI2 index, K270 index and oxidation stability) have been determined in unshelled and shelled hazelnuts dried under six drying air temperatures (30, 40, 50, 60, 70 and 80°). The drying experiments were done with forced air circulation, and two varieties of hazelnut were investigated, Negret and Pauetet. It has been observed that hydrolytic reactions affect dried Negret hazelnut, increasing with drying temperature. Also, drying temperatures higher than 50°C favour an increase of the rate of lipid oxidation in hazelnut, specially in shelled hazelnuts, with a decrease of the oxidation stability.

ISSN:0737-3937    

DOI:10.1080/07373939708917271

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

The influence of the drying conditions on the enzymatic activity in hazelnut (Corylus avellana, L.) has been studied. In this work, the activity of the enzymes lipase. peroxidase and polyphenoloxidase have been determined in hazelnuts dried under three temperatures (30, 50 and 70°C). The drying experiments were done with forced air circulation, and samples of Negret variety. unshelled and shelled, were used. It has been observed that the drying process reduces the activity of the enzymes lipase, peroxidase and polyphenoloxidase in hazelnut, and the results indicated that polyphenoloxidase is the most unstable to heat.

ISSN:0737-3937    

DOI:10.1080/07373939708917272

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

The influence of drying conditions on browning in hazelnut (Corylus avellana L.) has been studied by means of color measurement. Samples of unshelled and shelled hazelnuts were dried under six air temperatures (30. 40, 50, 60, 70 and 80°C). The drying experiments were done with forced air circulation, and two varieties of hazelnut were investigated, Negret and Pauetet. CiELab system was used to evaluate changes in total color (δE*), lightness (L*), chroma (C*) and hue angle (H*) on dried hazelnuts. Browning of hazelnut was observed to occur a1 all temperatures studied. The rate of pigment formation was determined from the δE' values with zero-order kinetic model, and temperature dependence was described by the Arrhenius equation with an activation energy (Ea) varying from 28 to 39 kJlmol. Negret variety showed the highest rate of browning.

ISSN:0737-3937    

DOI:10.1080/07373939708917273

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

A study of the pysical structure and quality potatoes during microwave and air drying war undertaken. The effect of various experimental variables on volumetric shrinkage including microwove power levels, air temperature and velocity as well as sample geometry was investigated. In both microwave and air drying, the shrinkage of potatoes showed a linear behaviour in relation to different moisture content levels. Experimental data showedthat air velocity and microwave power had a major effect on the degree of shrinkage, also the shrinkage behaviour was independent of sample geometry and air temperature. The use of microwave produced smaller changer in volume (less shrinkage) and henee a better quality finished product.

ISSN:0737-3937    

DOI:10.1080/07373939708917274

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

Soymilk slurries were spray dried at various combinations of inlet air temperature (1255. 265, and 275°C), feed rate (0.38 and 0.57 Lpm), and atomizer speed (119,300 and 26,800 rpm). Monitored dryer parameters included dry and wet bulb temperaturea of ambient and exhaust air, drying chamber's inlet and outlet air temperatures, product and feed temperatures, velocity pressure at exhaust pipe, atomizer speed, and feed rate. Weather data was included in the analysis.

ISSN:0737-3937    

DOI:10.1080/07373939708917275

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

Field-dried peanuts having 25% average moisture content have been dried by using a liquid dasiccant drying system. This system cansirts of climate simulation subsystem, closed loop air drying subsystem, and regeneration subsystem. The closed loop drying subsystem used in this investigation provides low temperature drying with a little increase in drying air temperature. Regeneration temperature, liquid desiccant concentration, and air flowrate in the drying subsystem have heen kept unchanged during the experiments, but air of different humidity have been used to regenerate the liquid desiccant. Experimental measurements of the system performance have been carried out utilizing a new cost effective desiccant mixrure (CELD) which is composed of equal portions by weight of lithium chloride and calcium chloride. The drying process has been performed using different climatic canditions in the regeneration process. Experimental rasults demonstrate that drying peanuts by the use of a liquid desiccant system is promising.

ISSN:0737-3937    

DOI:10.1080/07373939708917276

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

To simulate space cooling or drying systems for various geographical regions (low, moderate, and high humidity regions) a liquid desiccant system consisting of a humidifier and dehumidifier has been designed and constructed. This system consists of two coupled humidifying and dehumidifying packed columns filled with plastic Intalox Snowflake packing material. Experimental measurements of the dehumidifier performance utilizing a new effective liquid desiccant mixture (CELD) total desiccant salt content 40%wt.to 45%wt (salt comprised of equal portions by weight of lithium chloride and calcium chloride ), have. been carried out, The effect of different independent variables such as packing height, air inlet temperature and humidity ratio, and liquid desiccant inlet temperature, flow rate and concentration on the performance of the dehumidifier has been investigated. Experimental results demonstrate that the CELD is a promising desiccant for cooling and drying operations.

ISSN:0737-3937    

DOI:10.1080/07373939708917277

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

A set-up and a method are described with which sorption isotherms of granular materials can be measured. The set-up uses a recirculating air flow through a fluidized bed of granular materials. The measuring procedure starts with drying the granular material completely. A known amount of water is added to the fluidized bed. At equilibrium between the amount of water in the granular material and the circulating air the air humidity is measured. The method is demonstrated using silica gel.

ISSN:0737-3937    

DOI:10.1080/07373939708917278

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

Milled peat production involves the atmospheric drying of a 20-30mm deep layer of milled peat (i.e. peat in a powder or crumb form) on the surface of the bog. Research from various sources indicates that the drying of rate of this layer is highly dependent upon its particle size distribution. Experiments were conducted to confirm this phenomenon for Irish peats.

ISSN:0737-3937    

DOI:10.1080/07373939708917279

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor