Aspergillus niger inactivation in microwave rotary drum drying of whole garlic bulbs and effect on quality of dried garlic powder

Abstract

Microwave rotary drum drying of whole garlic bulbs was investigated for the Aspergillus niger inactivation and moisture removal. The Weibull and Bigelow models were applied to microbial inactivation data. Garlic bulbs with initial moisture content in the range 1.95–2.14?g water g^?1?dry matter were dried up to 0.06?g water g^?1?dry matter. The microwave power density (PD) was varied from 1.03 to 2.67 Wg^?1 at 1.5 and 2.0 pulsation ratios (PRs). Effect of PD and PR on A. niger inactivation, product temperature, moisture diffusivity, moisture ratio, drying rate, color, and sensory parameters was studied. Page model was found to be a better fit for microwave rotary drying characteristics of whole garlic bulbs. Microwave rotary drum drying resulted in the average log reduction of A. niger between 1.12 and 1.60. Weibull model predicted A. niger inactivation better than the Bigelow model as it considered the nonlinearity associated with a microbial population in the sterilization process. Garlic powder prepared at 2.0 PR and 1.85 Wg^?1 PD was chosen as the best process based on sensory score. The cracking and peeling of garlic cloves were observed during microwave rotary drum drying. The SEM images confirmed the increase in the pore size of the microwave treated garlic sample than the untreated garlic which might be the reason for cracking and loosening of peel in garlic.     

Drying kinetics and effective moisture diffusivity of purslane undergoing microwave heat treatment

The effects of microwave drying on moisture content, moisture ratio, drying time and effective moisture diffusivity of purslane leaves (Portulaca oleracea L.) were investigated. By increasing the microwave output power (180–900W) and the sample amounts (25–100 g), the drying time decreased from 43 to 12.5 minutes and increased from 27 to 54 minutes, respectively. To determine the kinetic parameters, the drying data were fitted to various models based on the ratios of the differences between the initial and final moisture contents and equilibrium moisture content versus drying time. Among the models proposed, the semi-empirical Midilli et al. model gave a better fit for all drying conditions applied. By increasing the microwave output power and decreasing the sample amount, the effective moisture diffusivity values ranged from 5.913×10⁻¹¹ to 1.872×10⁻¹⁰ m²/s and from 9.889×10⁻¹¹ to 3.292×10⁻¹¹ m²/s, respectively. The activation energy was calculated using an exponential expression based on the Arrhenius equation.     

EXPERIMENTAL STUDY ON DRYING OF CHILLI IN A COMBINED MICROWAVE-VACUUM-ROTARY DRUM DRYER

ABSTRACT

This paper presents new data on drying chilli in a microwave-vacuum-rotary drum dryer. This novel technique is designed to combine the advantages of vacuum drying and evenly dispersed microwave energy in a rotary drum. The drying kinetic and the specific energy consumption at particular product moisture content were measured experimentally. Moreover, the effect of pressure inside the chamber and the rotational speed of the drum were also determined.     

An experimental study on the performance of a condensing tumbler dryer with an air-to-air heat exchanger

The performance of energy consumption in the closed-loop tumbler dryer with a condenser for clothes drying is evaluated as a function of the heater capacity, the drying air flow rate inside the dryer, and the cooling air flow rate. The clothes dryer in laundries used in this study consists of a tumbling drum, condenser for condensing the humid and hot air flowing out the rotating drums, and electric heater for heating the circulating drying air. Tests were performed at the heating capacity of 1.9 kW to 2.7 kW, the drying air flow rate of 60 m³/h to 140 m³/h, and the cooling air flow rate of 100 m³/h to 240 m³/h. The total energy consumption, the drying time, and the condensate water rate were also investigated. Parametric results showed that a larger heater power resulted in shorter drying time. With increasing heater power, the air temperature and the condensate rate increased due to the higher humidity ratio in the air. The drying air flow rate and the cooling air flow rate did not have a significant effect on drying performance.     

Microwave drying of wastewater sludge: Experimental and modeling study

This study investigates experimentally and using mathematical modeling the microwave drying of wastewater sludge with determination of moisture diffusivity at different drying conditions. The drying behavior was observed at different power levels (480, 840, and 1,080 W) and different initial masses (90, 120, and 150 g). The observed drying kinetics were divided into three parts: a short adaptation period, a long constant drying rate period, and a falling drying rate period. The maximum drying rate was observed during the constant rate period. Mainly, the results show that the drying rate decreases with the initial mass increase (from 0.45 kg·kg^?1·min^?1 for 90 g to 0.25 kg·kg^?1·min^?1 for 150 g) and increases with an increase in power level (from 0.15 kg·kg^?1·min^?1 at 480 W to 0.45 kg·kg^?1·min^?1 at 1,080 W). The measurement of the sample dimensions shows that shrinkage can occur and, depending on the drying conditions, it ranged between 0.42 and 0.37 of the sample initial volume. Presenting a more accurate solution of the diffusion model by incorporating shrinkage and finite dimensions of the sample is the novelty of this study. The drying conditions influenced the diffusion coefficient, which ranged from 1.53 × 10^?7 to 7.67 × 10^?7 m²s^?1. Similar to the drying rate, the diffusion coefficient was directly proportional to the power level and inversely proportional to the initial mass. Activation energy was determined using an Arrhenius relationship of the diffusion coefficient as a function of the ratio initial mass to the power level.     

Performance of fluidized bed electrode in a molten carbonate fuel cell anode

A fluidized bed electrode could lower concentration polarization and activation polarization because of its high mass and heat transfer coefficient. The polarization characteristics of the fluidized bed electrode are systematically investigated in a molten carbonate fuel cell anode with an O₂/CO₂/gold reference electrode. The results show that polarization performance of the anode is improved by selecting proper flow rates of H₂, O₂ and CO₂, choosing suitable nickel particle content together with appropriate O₂/CO₂ ratio, and increasing reaction temperature as well as the area of the current collector. Limiting current density of 115.56 mA·cm⁻² is achieved under optimum performance as follows: a cylindrically curved nickel plate current collector, nickel particle content of 7.89%, the reaction temperature of 923 K, H₂ flow rate of 275 mL·min⁻¹, O₂/CO₂ flow rate of 10/20 mL·min⁻¹ and O₂/CO₂ ratio of 1 : 2.     

Efficient drying and oxygen-containing functional groups characteristics of lignite during microwave irradiation process

To remove the high moisture of ZhaoTong lignite, the efficient drying characteristics and oxygen-containing functional groups changes in lignite during microwave irradiation process were highlighted in this study. As the microwave absorbers, lignite char and NaNO₃ were added to microwave drying of ZhaoTong lignite. The minimum chemical oxygen demand of waste water generated from microwave drying process of lignite was 99.89?mg?O₂?L^?1. The effects of microwave power, lignite mass, the weight ratio of lignite char to lignite and NaNO₃ content on the drying rate, and moisture diffusion coefficient of lignite were investigated during lignite microwave irradiation process. It was found that the drying rate and moisture diffusion coefficient of lignite increased with increasing microwave power, the weight ratio of lignite char to lignite and NaNO₃ content, but decreased with increasing lignite mass. Lignite char and NaNO₃ were mixed with lignite that can enhance the instantaneous surface temperature of lignite sample under microwave irradiation. Compared with addition of lignite char to lignite, the addition of NaNO₃ to lignite can decrease the unit electric power consumption of moisture evaporating. And the minimum unit electric power consumption of moisture evaporating was 9.44?Wh?g^?1. The FTIR technology was used to investigate the oxygen-containing functional groups changes in lignite during microwave drying process. The oxygen-containing functional groups of lignite were effectively removed with increasing microwave power.     

放射性废树脂微波桶内干燥控制方式研究

用微波作为热源,在桶内干燥核电厂产生的废树脂。通过对脉冲式和旋转式两种控制方式在12L规模和200L规模台架中的实验研究可知,两种控制方式均可有效的改善树脂干燥的均匀性问题,但从试验安全和设备设计角度出发建议下一步以脉冲式控制为台架装置设计基础。     

Epoxidation of karanja (Pongamia glabra) oil by H2O2

Epoxidation of karanja oil (KO), a nondrying vegetable oil, was carried out with peroxyacetic acid that was generated in situ from aqueous hydrogen peroxide and glacial acetic acid. KO contained 61.65% oleic acid and 18.52% linoleic acid, respectively, and had an iodine value of 89 g/100 g. Unsaturated bonds in the oil were converted to oxirane by epoxidation. Almost complete epoxidation of ethylenic unsaturation was achieved. For example, the iodine value of the oil could be reduced from 89 to 19 by epoxidation at 30°C. The effects of temperature, hydrogen peroxide-to-ethylenic unsaturation ratio, acetic acid-to-ethylenic unsaturation ratio, and stirring speed on the epoxidation rate and on oxirane ring stability were studied. The rate constant and activation energy for epoxidation of KO were 10⁻⁶ L·mol⁻¹·s⁻¹ and 14.9 kcal·mol⁻¹, respectively. Enthalpy, entropy, and free energy of activation were 14.2 kcal·mol⁻¹, −51.2 cal·mol⁻¹·K⁻¹, and 31.1 kcal·mol⁻¹, respectively. The present study revealed that epoxides can be developed from locally available natural renewable resources such as KO.     

EXPERIMENTAL STUDY ON DRYING OF CHILLI IN A COMBINED MICROWAVE-VACUUM-ROTARY DRUM DRYER

This paper presents new data on drying chilli in a microwave-vacuum-rotary drum dryer. This novel technique is designed to combine the advantages of vacuum drying and evenly dispersed microwave energy in a rotary drum. The drying kinetic and the specific energy consumption at particular product moisture content were measured experimentally. Moreover, the effect of pressure inside the chamber and the rotational speed of the drum were also determined.     

R&D OPPORTUNITES IN DRYING OF ADVANCED ELECTRO-CERAMICS

ABSTRACT

This article presents an inaoduction to the various drying processes operational in the ceramic processing industry, with special emphasis on electro ceramics. An attempt is made to arouse the interest of drying specialists in fields other than ceramics to participate in a concentrated group effort to solve a number of existing problems related to ceramics drying. The importance of materials education is highlighted by referring to a few examples depicting the effect of the drying process on the final product quality. It is argued that with more research, conventional processes like spray drying, rotary drum drying, etc. can be improved or replaced with alternative processes like freeze drying, microwave drying, infrared drying and vibrated fluidized bed drying.     

Effects of quenching mechanisms of carotenoids on the photosensitized oxidation of soybean oil

The effects of 0, 1.0 × 10”⁻⁵, 2.5 × 10⁻⁵, and 5.0 × 10⁻⁵ M β-apo-8'-carotenal, β-carotene, and canthaxanthin on the photooxidation of soybean oil in methylene chloride containing 3.3 × 10⁻⁹ M chlorophyll b were studied by measuring peroxide values and conjugated diene content. β-Apo-8'-carotenal, β-carotene, and canthaxanthin contain 10,11, and 13 conjugated double bonds, respectively. The peroxide values and conjugated diene contents of oils containing the carotenoids were significantly lower (P<0.05) than those of control oil containing no carotenoid. As the number of conjugated double bonds of the carotenoids increased, the peroxide values of soybean oils decreased significantly (P<0.05). The quenching mechanisms and kinetics of the carotenoids in the photosensitized oxidation of soybean oil were studied by measuring peroxide values. The steady-state kinetics study showed that carotenoids quenched singlet oxygen to reduce chlorophyll-sensitized photooxidation of soybean oil. The singlet-oxygen quenching rate constants ofβ- apo-8'-carotenal, β-carotene, and canthaxanthin were 3.06 × 10⁹, 4.60 × 10⁹, and 1.12 × 10¹⁰ M⁻¹sec⁻¹, respectively.     

Nitrogen competition in contour hedgerow systems in subtropical China

Contour hedgerow agroforestry has been studied for soil erosion control and soil fertility improvement in subtropical China. However, below-ground competitive and complementary interactions between tree hedges and crops have received relatively little attention in the scientific literature. A field experiment was conducted to explore the effects of a leguminous shrub hedge, false indigo (Amorpha fruticosa) and a non-legume gramineous hedge, vetiver (Vetiveria zizanioides), on the growth of soybean (Glycine max). Pot experiments were also carried out to determine the effect of below-ground interactions on nitrogen uptake between two contour hedgerow agroforestry with a ¹⁵N isotope method and root partition, i.e., a sheet barrier, a mesh barrier and no barrier. The results showed that the relative disadvantage of intercropping, expressed as land equivalent ratio, were 0.96/0.97 for the A. fruticosa–soybean system and 0.99 for the vetiver–soybean system, based on the dry matter (DM) production and N acquisition. Both area-adjusted yield and N content of soybean were significantly decreased in two intercropping treatments compared to those in the sole soybean treatment. The DM production of soybean, for example, was decreased by 10% and 5% under A. fruticosa and vetiver, respectively, when compared to the sole soybean. The intercropping disadvantage was mainly due to interspecific competitive interaction. The result was proved by lower yields and biomasses adjacent to the hedgerows. The ¹⁵N-based estimates of N uptake, in the vetiver–soybean system, of soybean with mesh separation (6.11 mg pot⁻¹) was lower than that (13.85 mg pot⁻¹) with no root separation, for vetiver the higher ¹⁵N uptake was observed in no root separation (13.90 mg pot⁻¹). In the A. fruticosa–soybean system, the lower ¹⁵N uptake of soybean (1.53 mg pot⁻¹) and A. fruticosa (6.42 mg pot⁻¹) were observed in no root separation. It is concluded that the growth of soybean was unexpectedly suppressed in two intercropping systems. The growth of A. fruticosa was clearly suppressed due to below-ground interactions, yet the growth of vetiver was improved to a great extent.     

Dissolution of colemanite in (NH<Subscript>4</Subscript>)2SO<Subscript>4</Subscript> solutions

Turkey is the country having the richest boron ores in the world, and colemanite, tincal and ulexite are the ores being mined mostly in Turkey. These ores are used in the production of various boron compounds of which the production methods are generally patented. Colemanite ore also is reacted with sulfuric acid to product boric acid. Produced by this method, boric acid contains various impurities which reduce the market value and are difficult to remove. This study investigated the reaction between colemanite and ammonium sulfate as an alternative method to produce boric acid. Particle size, ammonium sulfate concentration, solid to liquid ratio and reaction temperature were chosen as parameters. In results, the conversion rate was increased by decreasing particle size and solid to liquid ratio, by increasing ammonium sulfate concentration and temperature. A semi-empirical model with 40.46 kJmol⁻¹ activation energy representing this process was found as follows: 1−(1−X)^1/3=2.12×10²·C^1.38·R^−0.75·(S/L)^−0.44·e^−4866/T·t^0.61.     

Deuterium uptake and plasma cholesterol precursor levels correspond as methods for measurement of endogenous cholesterol synthesis in hypercholesterolemic women

To assess the validity of two techniques used to measure human cholesterol synthesis, the rate of uptake of deuterium (D) into plasma free cholesterol (FC), and plasma cholesterol precursor (squalene, lanosterol, desmosterol and lathosterol) levels were compared in 14 women [65–71 yr with low density lipoprotein-cholesterol (LDL-C)≥3.36 mmol·l ⁻¹]. Subjects consumed each of six diets for 5-wk periods according to a randomized crossover design. The experimental diets included a baseline diet (39% energy as fat, 164 mg chol·4.2 MJ⁻¹) and five reduced-fat diets (30% of energy as fat), where two-thirds of the fat was either soybean oil; squeeze, tub or stick margarines; or butter. Fractional and absolute synthesis rates (FSR and ASR) of FC were determined using the deuterium incorporation (DI) method, while cholesterol precursor levels were measured using gas-liquid chromatography. Data were pooled across diets for each variable and correlation coefficients were calculated to determine if associations were present. There was good agreement among levels of the various cholesterol precursors. In addition, FSR in pools/d (p·d⁻¹) and ASR in grams/d (g·d⁻¹) were strongly associated with lathosterol (r=0.72 and 0.71, P=0.0001), desmosterol (r=0.75 and 0.75, P=0.0001), lanosterol (r=0.67 and 0.67), and squalene (r=0.69 and 0.68) when levels of the precursors were expressed as μmol·mmol⁻¹C. Significant but lower correlations were observed between the D uptake and plasma cholesterol precursor levels when the latter were expressed in absolute amounts (μmol·L⁻¹). The wide range of fatty acid profiles of the experimental diets did not influence the degree of association between methods. In conclusion, the DI method and levels of some cholesterol precursors correspond as methods for shortterm measurement of cholesterol synthesis.     

Effects of organic acid catalysts on the hydrogen generation from NaBH4

Sodium borohydride has received much attention from fuel cell developers due to its high hydrogen storage capacity. In this study, organic acid solutions such as malic, citric, acetic acids were successfully utilized to accelerate and control hydrogen generation from stabilized sodium borohydride solutions. The generated hydrogen by malic acid was then continuously supplied to a PEMFC single cell. A power density of 168 mW cm⁻² was achieved with a hydrogen flow rate of 0.050 L min⁻¹ that was generated by adding 10 wt% aqueous malic acid to the stabilized sodium borohydride solution at an air flow rate of 0.11 L min⁻¹ without humidification. Further increase of power density to 366 mW cm⁻² is practicable by maintaining a precise hydrogen flow rate of 0.3 L min⁻¹. The current study focuses on the development of an instant hydrogen generation method for micro fuel cell applications. We successfully demonstrated that fast and direct generation of hydrogen could be achieved from stabilized borohydride using inexpensive organic acid solutions rather than expensive metal catalysts and a PEMFC single cell could be operated by generated hydrogen.     

Evaluation of the characteristics using slow strain rate tests of 5456 Al-Mg alloy for ship construction

Recently, there has been increased interest in using aluminum alloys in ship construction instead of fiber-reinforced plastic (FRP). Aluminum alloy ships are faster, have a greater load capacity, and are easier to recycle than FRP ships. We investigated the mechanical and electrochemical properties of aluminum alloys using slow strain rate and potentiostatic tests under various potential conditions. Aluminum and aluminum alloys do not corrode due to the formation of an anti-corrosive passive film, such as Al₂O₃ or Al₂O₃·3H₂O, which resists corrosion in neutral solutions. In seawater, however, Cl⁻ ions destroy this passive film. The optimum protection potential range with regards to hydrogen embrittlement and stress corrosion cracking was determined to lie between −1.5 and −0.7 V (SSCE). These results can be used as reference data for ship design.     

Chlorinated long chain fatty acids—their properties and reactions: III. Solvent effects in the dehydrohalogenation of sodium 9,10-dichlorooctadecanoate in dilute alkaline solutions

The first stage of the alkaline dehydrohalogenation of sodium 9,10-dichlorooctadecanoate (DCO) has been studied in ethylene glycol-water mixtures and in pure water at 90 C. The rate of the reaction was found to decrease rapidly with increasing water concentration. The rate of removal of the first chlorine from sodium 9,10-dichlorooctadecanoate was determined as a function of the water concentration in various ethylene glycol-water mixtures. The rate coefficient (k_OH) in pure water solution was 1.4·10⁻⁴ kg·mole⁻¹·min⁻¹ as compared to the maximum value of 2.7·10⁻² kg·mole⁻¹·min⁻¹ in 19 wt % solution. The effects of temperature and base concentration on the reaction rate were also investigated.     

Properties and catalytic mechanism of γ-glutamyltranspeptidase from B.subtilis NX-2

Since γ-glutamyltranspeptidase (GGT) especially catalyses the transfer of the γ-glutamyl moiety to a variety of amino acids and short peptides, GGT has important practical value for enzymatic synthesis of γ-glutamyl compounds. In this paper, the GGT produced from Bacillus subtilis NX-2 was purified by a combination of ammonium sulfate fractionation and ion exchange chromatography, and the properties of purified GGT were investigated. At the conditions of pH 10.0, D-glutamine (D-Gln)/L-tryptophan (L-Trp) with a molar ratio of 5: 7, a temperature 40°C and a reaction time of 4 h, a higher conversion rate of 42% was obtained. According to the time course, the catalytic mechanism of enzymatic synthesis of γ-D-glutamyl-L-tryptophan (γ-D-Gln-L-Trp) was discussed. It was demonstrated that the GGT can catalyze not only the reaction of transpeptidation, but also the irreversible hydrolysis of the products which results in the decrease of the yield of the products. The affinity parameter of GGT to D-Gln (Km) was 5.08 mmol·L⁻¹ and the maximum reaction rate of transpeptidation (r _max) was determined as 0.034 mmol·min⁻¹·L⁻¹, while the affinity parameter of GGT to γ-D-Gln-L-Trp (K’_m) was 2.267 mmol·L⁻¹, and the maximum reaction rate of hydrolysis (r’_max) was 0.012 mmol·min⁻¹·L⁻¹. __________ Translated from Journal of Chemical Engineering of Chinese Universities, 2008, 22(2): 288–293 [译自: 高校化学工程学报]     

Effects of various factors on capacitive properties of VO<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript>·<Emphasis Type="Italic">n</Emphasis>H<Subscript>2</Subscript>O powders in aqueous electrolyte

In this work, effects of drying temperature, pH of aqueous electrolyte and current density on capacitive performance of VO _x ·nH₂O material were firstly investigated. VO _x ·nH₂O powders were prepared by a melt quenching method. The samples were characterized by X-ray diffraction analysis (XRD) and Fourier transform infrared (FTIR). The capacitive properties of VO _x ·nH₂O samples were examined by cyclic voltammetry and galvanostatic charge/discharge test. VO _x ·nH₂O sample which was obtained at the drying temperature of 80 °C, delivers a maximum specific capacitance of 227.3 F g⁻¹ and exhibits excellent capacity retention in the potential range of −0.3 to 0.7 V at a current density of 200 mA g⁻¹ in NaNO₃ solution with pH 2.