Kinetics and variation of volatile components of Atractylodis Macrocephalae Rhizoma during hot-air drying / 中国中药杂志

The present study explored the kinetics and variation of volatile components of Atractylodis Macrocephalae Rhizoma during the hot-air drying process to obtain the optimal process parameters under multiple goals such as drying efficiency and drying quality. The dry basis moisture content and drying rate curves along with the change of drying time of Atractylodis Macrocephalae Rhizoma were investigated at five levels of drying air temperatures(30, 40, 50, 60, and 70 ℃). The relationship between moisture ratio and time in the drying process of Atractylodis Macrocephalae Rhizoma was fitted and verified by Midilli model, Page model, Overhults model, Modified Page model, Logaritmic model, Two terms Exponential model, and Newton model. Meanwhile, the effective diffusion coefficient of moisture(D_(eff)) and activation energy(E_a) in Atractylodis Macrocephalae Rhizoma were calculated under different drying air temperatures. GC-MS was used to determine the volatile components and content changes of the fresh Atractylodis Macrocephalae Rhizoma and dried products at different temperatures. The dry basis moisture content and drying rate of Atractylodis Macrocephalae Rhizoma were closely related to the temperature of the drying medium, and the moisture of the Atractylodis Macrocephalae Rhizoma decreased with the prolonged drying time. As revealed by the drying rate curve, the drying rate increased with the increase in hot air temperature, and the migration of moisture was accelerated. The comparison of the correlation coefficient(R~2), chi-square(χ~2), and root mean standard error(RMSE) of each model indicated that the parameter average of the Midilli model had the highest degree of fit, with R~2=0.999 2, χ~2=8.78×10~(-5), and RMSE=8.20×10~(-3). Besides, the D_(eff) at 30-70 ℃ was in the range of 1.04×10~(-9)-6.28×10~(-9) m~2·s~(-1), and E_a was 37.47 kJ·mol~(-1). The volatile components of fresh Atractylodis Macrocephalae Rhizoma and dried products at different temperatures were determined by GC-MS, and 18, 18, 18, 17, 17, and 18 compounds were identified respectively, which accounted for more than 84.76% of the volatile components. In conclusion, the hot-air drying of Atractylodis Macrocephalae Rhizoma can be model-fitted and verified and the variation law of the moisture and volatile components of Atractylodis Macrocephalae Rhizoma with temperature is obtained. This study is expected to provide new ideas for exploring the drying characteristics and quality of aromatic Chinese medicine.

Drying kinetics modeling of apple and zucchini slices vacuum impregnated with anthocyanins / Modelagem da cinética de secagem de discos de maçã e abobrinha impregnadas a vácuo com antocianinas

ABSTRACT: The aim of this research was to study the drying kinetics of apple and zucchini slices enriched with anthocyanins and to evaluate the influence of drying temperature on the anthocyanin content of apple and zucchini snacks. Apple (Granny Smith) and zucchini (Cucurbita pepo) slices were enriched with anthocyanins by vacuum impregnation with blueberry juice. Then, slices were dehydrated at 40, 50 and 60 ºC with 1.0 m/s air flow. Dehydrated samples were referred to as anthocyanin enriched snacks. Diffusion coefficient values improved by increasing the drying temperature, within the 2.81×10-10 to 5.78×10-10 m2/s range for apple slices and 2.02×10-10 to 3.99×10-10 m2/s for zucchini slices. The activation energy was 31.19 kJ/mol and 80.33 kJ/mol for apple and zucchini slices respectively. Page, Weibull, Logarithmic, Henderson-Pabis and Lewis models best fitted the experimental data. Snacks obtained at 60 °C retained a higher concentration of anthocyanins, reaching values of 592.81±52.55 and 464.62±48.44 mg of cyaniding-3-glucoside equivalent/kg dry matter in apple and zucchini snacks respectively. Combination of vacuum impregnation and hot air drying was a technological alternative for producing snacks with functional properties.

RESUMO: O objetivo deste trabalho foi estudar a cinética de secagem de fatias de maçã e abobrinha enriquecidas com antocianinas e avaliar a influência da temperatura de secagem no teor de antocianinas de discos de maçã e abobrinha. Fatias de maçã (Granny Smith) e abobrinha (Cucurbita pepo) foram enriquecidas com antocianinas por impregnação a vácuo com suco de mirtilo. Em seguida, as fatias foram desidratadas a 40, 50 e 60 ºC com fluxo de ar de 1,0 m / s. As amostras desidratadas foram referidas como snacks enriquecidos com antocianinas. Os valores do coeficiente de difusão melhoraram com o aumento da temperatura de secagem, na faixa de 2.81 × 10-10 a 5.78 × 10-10 m2/s para fatias de maçã e 2.02 × 10-10 a 3.99 × 10-10 m2/s para fatias de abobrinha. A energia de ativação foi 31.19 kJ / mol e 80.33 kJ / mol para as fatias de maçã e abobrinha, respectivamente. Os modelos de Page, Weibull, Logarithmic, Henderson-Pabis e Lewis ajustaram os dados experimentais. Os snacks obtidos a 60 °C retiveram uma maior concentração de antocianinas, atingindo valores de 592.81 ± 52.55 e 464.62 ± 48.44 mg de equivalentes de cianidina-3-glicosídeo / kg de matéria seca nos snacks de maçã e abobrinha, respectivamente. A combinação da impregnação a vácuo e secagem por ar quente foi uma alternativa tecnológica para produção de lanches com propriedades funcionais.

Effects of three drying technologies on drying kinetics and quality attributes of yam slices / 中草药

Objective: In order to explore suitable drying technology for yam slices, the effects of three different drying methods, namely medium and short infrared wave drying, air impingement drying, pulsed vacuum drying, on drying kinetics and quality attributes of yam slices were investigated. Methods: The moisture ratio, drying rate curves along with the change of drying time and relationship between dry basis moisture content and drying rate of yam slices were studied under three drying methods. Additionally, the effects of the three drying technologies on color parameters (L*, a*, b*), rehydration ratio, allantoin and extract contents were investigated. Results: All drying process of the three drying methods for yam slices belonged to the falling rate period without constant drying stage, and the shortest drying time was only 120 min obtained under air impingement drying temperature of 70 ℃, air velocity of 15 m/s. The effective moisture diffusivities were 7.52 × 10-10, 1.19 × 10-9 and 1.30 × 10-9 m2/s for pulsed vacuum drying, medium and short infrared wave drying and air impingement drying, respectively. The three drying methods were comprehensively evaluated based on seven indexes including rehydration ratio, drying time, extract and allantoin content, etc. The comprehensive scores of medium and short infrared wave drying, pulsed vacuum drying and air impingement drying were 0.29, 0.59, and 0.70, respectively, which indicated that air impingement drying obtained the highest score. Conclusion: Comprehensive evaluation results showed that the best drying method for yam slices drying is air impingement drying and the air impingement. This study provides a theoretical basis for the exploration of suitable drying technology and drying conditions for yam slices dehydration.

Drying kinetics and mathematical modeling of Erzhi Pills during hot-air drying process / 中草药

Objective: To study the change rule of water content in the drying process of hot air drying of thin layer drying characteristic and model research, and to provide reference for improving the quality of Erzhi Pills (EP). Methods: The moisture ratio, drying rate of dry basis, and drying rate curves along with the change of drying time and relationship between dry basis moisture content and drying rate of EP were studied using a hot air dryer at five levels of drying air temperature in the range of 50-90 ℃. The model was fitted and verified by the empirical model Henderson & Pabis model, Newton model, Page model, Logarithmic model, two term exponential model, Wang & Singh model, Midilli et al. model, etc. Meanwhile, based on Fick's diffusion law, the effective diffusion coefficients of water (Deff) and activation energy value in EP were calculated. Results: The drying curves of EP show that the moisture ratio and drying rate of EP were closely related to the temperature of drying medium, and the moisture of the material decreases with the prolonged drying time. It could be seen from the drying rate curve that the drying rate increased with the increase of hot air temperature, and the migration of moisture was accelerated. By comparing the correlation coefficient (R2), chi-square (χ2) and standard error (RMSE), we could see that the mean value of R2 of model number 7 was the maximum, the χ2 and RMSE mean were the smallest (0.996 86, 2.43 × 10−4, and 1.93 × 10−4), respectively. The results showed that the model number 7 could describe and predict the drying process of the pills. The experimental data had the effective diffusion coefficient (Deff) value of 8.6 × 10−11—3.13 × 10−10 m2/s, and the activation energy (Ea) was 30.97 kJ/mol. Conclusion: The hot air drying process of EP can be modeled and verified. The research provides a new way to explore the drying characteristics and quality of pills.

Drying Kinetics of Gum Karaya (Sterculia urens) Using Convective Air Dryer.

The present study was aimed to investigate the drying kinetics of gum karaya (S. urens). Three grades of gum (I, II, III) were dried using a cabinet-type convective dryer. Particle size equivalent to US Sieve size-6 and air temperatures of 50, 60 and 70°C were used for the drying experiments. The experimental drying data was fitted to Page’s model to predict the drying kinetics. Investigations with constant air velocity revealed that for grade- I gum, drying rate constant (k) varied between 0.2744-0.3742 (h-1), for grade-II gum between 0.3208-0.4439 (h-1) and for grade-III gum between 0.4098-0.4639 (h-1). The dimensionless number (n) was always more than 1 and minimum value of the Coefficient of determination (R2) was 0.967. Increase in air temperature enhanced drying process and drying rate. For each particular temperature, the values of drying rate constant were minimum for grade-I, maximum for grade-III and intermediate for grade-II gum.

Avaliação das curvas de secagem de guaco (Mikania glomerata Spreng. ) em secador de bandejas / Evaluation of drying curves of Mikania glomerata Spreng. in a tray dryer

Esse trabalho teve como objetivo avaliar diferentes modelos matemáticos para determinar a curva de secagem de guaco. Para a condução do experimento, foi utilizado um secador com ventilação forçada, com 4 bandejas, empregando gás liquefeito de petróleo como fonte de aquecimento. Foram realizados 6 tratamentos de secagem: com ar aquecido a 40, 50, 60, 70 e 80ºC, e com ar a temperatura ambiente. Para todos os tratamentos a velocidade do ar de secagem passando através da massa de plantas foi mantida em, aproximadamente, 0,5 m s-1. Para ajuste dos modelos matemáticos aos dados experimentais realizou-se análise de regressão não-linear pelo método Quasi-Newton empregando-se o programa computacional STATISTICA 6.0®, sendo os valores dos parâmetros dos modelos estimados em função da temperatura do ar de secagem. Apenas o modelo proposto por Midilli et al. apresentou ajuste satisfatório para descrever o processo de secagem de guaco, independentemente da temperatura do ar de secagem, enquanto o modelo da aproximação da difusão se adequou para a temperatura ambiente e com ar aquecido a 60ºC.

This work aimed to evaluate different mathematical models to determine the curve of the drying of Mikania glomerata Spreng. . For the conduction of the experiment, a drier with forced ventilation was used, with 4 trays, using liquefied petroleum gas as heating source. Six drying treatments were carried out, that is, with hot air at 40, 50, 60, 70 and 80ºC, as well as drying with air at room temperature. For all the treatments, the drying air speed, through the mass of plants, were kept at, approximately, 0.5 m s-1. For the adjustment of the mathematical models to the experimental data, nonlinear regression analysis was performed through the Quasi-Newton method, using the computational program STATISTICA 6.0®, and the values of the parameters of the models were estimated in function of the temperature of the drying air. But only the model considered by Midilli et al. presented satisfactory adjustment to describe the process of drying Mikania glomerata Spreng., regardless of the temperature of the drying air, while the model of diffusion approximation was suitable for room temperature and hot air at 60ºC.

Mathematical modeling of convective air drying of quinoa-supplemented feed for laboratory rats

Drying kinetics of quinoa-supplemented feed for laboratory rats during processing at 50, 60, 70, 80 and 90ºC was studied and modeled in this work. Desorption isotherm was obtained at 60ºC giving a monolayer moisture content of 0.04 g water/g d.m. The experimental drying curves showed that drying process took place only in the falling rate period. Several thin-layer drying equations available in the literature were evaluated based on determination coefficient (r²), sum squared errors (SSE) and Chi-square (χ2) statisticals. In comparison to the experimental moisture values, the values estimated with the Logarithmic model gave the best fit quality (r² >0.994, SSE < 0.00015 and χ2 < 0.00018), showing this equation could predict very accurately the drying time of rat feed under the operative conditions applied.