Cracking the code: Spatial heterogeneity as the missing piece for modeling granular fluidized bed drying

Pharmaceutical twin-screw wet granulation is a multifaceted and intricate process pivotal to drug product development. Accurate modeling of this process is indispensable for optimizing manufacturing parameters and ensuring product quality. The fluid bed dryer, an integral component of this granulation process, significantly influences the granular critical quality attributes. This study builds upon prior research by integrating experimental findings on granule segregation during fluid bed drying into an existing compartmental model, enhancing its predictive capabilities. An additional model layer on granule segregation behavior is composed and integrated into the existing model structure in this study. The added model compartment describes probability distributions on the vertical position of granules within each granule size class considered. To beware of overfitting, predictions of both the moisture content after drying and the granule bed temperature throughout drying are discussed in this study relative to experimental data from earlier published studies. These independent analyses demonstrated a marked improvement in prediction accuracy compared to earlier published model structures. The refined model accurately predicts the residual moisture content after drying for an untrained formulation. Moreover, it simultaneously makes accurate predictions of the granular bed temperature, which emboldens its structural correctness. This advancement makes it a powerful tool for predicting the behavior of the pharmaceutical fluid bed drying, which holds significant promise to facilitate pharmaceutical product development.

Mechanistic modeling of semicontinuous fluidized bed drying of pharmaceutical granules by incorporating single particle and bulk drying kinetics

In this work, a mechanistic fluidized bed drying model computing the granule moisture content in function of granule size, drying time, process settings and formulation properties is developed. Modeling the moisture content distribution concerning the granule size is essential for tabletability and drug product quality. This work combines a mechanistic bulk model and a single-particle drying kinetics model in a semicontinuous mode. The added model complexity allows physical approximations of drying phenomena at both the drying system level and the granular level. This includes quantifying the variations in moisture content by taking into account the specific dryer design and the variations in granule size. The model performance was quantified through industrially relevant case studies. It was revealed that the proposed model structure accurately predicts the drying behavior of the yield fraction. However, systematic model biases were observed for the fine and coarse fractions of the granule size distribution. In addition, discrepancies in the predicted outgoing air properties (relative air humidity and air temperature) were obtained. Further enhancement of the model complexity, e.g. complete incorporation of fluidization and segregation phenomena, is likely to improve the model performance. Notwithstanding, the developed model forms a step towards a formulation-generic fluidized bed drying model as interacting mechanisms on different levels of the drying system are considered.

Stability of yerba mate extract, evaluation of its microencapsulation by ionic gelation and fluidized bed drying

Studies show that yerba mate (Ilex paraguariensis) has high antioxidant capacity occasioned by its high contents of total phenolic compounds. Microencapsulation, specifically ionic gelation, since it does not use heating during process, is considered as an alternative for preserving and applying the extract. The purpose of this study was to evaluate general characteristics and stability of hydroalcoholic extract of yerba mate, conduct the extract microencapsulation by ionic gelation followed by microparticle fluidized bed drying. The extract was evaluated for color stability, total phenolic compounds, and antioxidant activity for nine weeks and at three temperatures (5, 15, and 25 °C). From the extract, a double emulsion (W/O/W), generation of microparticles (ionic gelation by dripping), and fluidized bed drying were conducted. The extract had 32912.55 mg GAE/100 g of phenolic compounds and 2379.49 μmol TE/g of antioxidant activity. The main compound observed was chlorogenic acid (5-CQA) with 0.35 ± 0.01 g/100 mL. In the stability study, the temperature was observed to influence in phenolic compounds reduction, as well as in total color difference of the extract. Double emulsion has shown to be stable and appropriate for use. The values of microparticles total phenolic compounds and antioxidant activity were 423.18 ± 8.60 mg GAE/100 g and 21.17 ± 0.24 μmol TE/g, respectively. After drying, the moisture of microparticles was reduced from 79.2% to 19%. The extract had high total phenolic compound content and high antioxidant activity. Storage at the lowest temperature (5 °C) assured better preservation of extract total phenolic compounds. The dried microparticles showed content of total phenolic compounds and antioxidant activity with potential for commercialization and future application in food matrices.

Microwave assisted fluidized bed drying of bitter gourd: Modelling and optimization of process conditions based on bioactive components

Bitter gourds were dried under varied drying conditions in a microwave assisted fluidized bed dryer, and the process was optimized using response surface methodology. Microwave power, temperature and air velocity were used as process variables for drying and the process parameters were varied between 360 and 720 W, 40-60 °C and 10-14 m/s, respectively. The responses determined for deciding the optimal criteria were vitamin C, total phenolics, IC₅₀, total chlorophyll content, vitamin A content, rehydration ratio, hardness and total color change of the dried bitter gourd. Statistical analyses were done by using response surface methodology, which showed that independent variables affected the responses to a varied extent. The optimum drying conditions of 550.89 W microwave power, 55.87 °C temperature, and 13.52 m/s air velocity were established for microwave assisted fluidized bed drying to obtain highest desirability for the dried bitter gourd. At optimum conditions, validation experiment was done to ensure the suitability of models. Temperature and drying time plays an important role in the deterioration of bioactive components. Faster and shorter heating led to the greater retention of bioactive components. Taking the aforesaid results into consideration, our study recommended MAFBD as a promising technique with minimum changes in quality attributes of bitter gourd.

Computational Modeling of Fluidized Beds with a Focus on Pharmaceutical Applications: A Review

The fluidized bed is an essential and standard equipment in the field of process development. It has a wide application in various areas and has been extensively studied. This review paper aims to discuss computational modeling of a fluidized bed with a focus on pharmaceutical applications. Eulerian, Lagrangian, and combined Eulerian-Lagrangian models have been studied for fluid bed applications with the rise of modeling capabilities. Such models assist in optimizing the process parameters and expedite the process development cycle. This paper discusses the background of modeling and then summarizes research papers relevant to pharmaceutical unit operations.

Applications of ultrasound to enhance fluidized bed drying of Ascophyllum Nodosum: Drying kinetics and product quality assessment

In this study, ultrasound either as a pretreatment technique or as an integrated technique was employed to enhance fluidized bed drying of Ascophyllum nodosum, and drying kinetics and dried product quality were assessed. In order to compare technology efficiency and dried product qualities, oven drying and fluidized bed drying (FBD) were employed. The novel drying methods included airborne ultrasound-assisted fluidized bed drying (AUA), ultrasound pre-treatment followed by FBD (USP), and hot water blanching pre-treatment followed byFBD (HWB). Six drying kinetics models were used to describe the drying curves, among which the Page model was the best in fitting USP and AUA. Model by Millidi et al. was employed to describe HWB. Airborne ultrasound in AUA did not reduce energy consumption or drying time, but retained total phenolic content (TPC) as well as colour, and exhibited the highest yield among the novel drying methods. USP and HWB showed lower energy consumption and drying time considerably, but the TPC was the lowest among the studied methods. At the same time, USP dried product exhibited the lowest aw, followed by HWB and then AUA. This studyalso demonstrated that FBD could be a very practical drying method on Irish brown seaweed, and ultrasound-assisted drying methods may have potential developments in Irish brown seaweed drying process.

Dynamic flavor perception of encapsulated flavors in a soft chewable matrix

Encapsulation is commonly used to protect flavor compounds against adverse environmental and processing conditions or to provide controlled release in processed foods. Flavor compounds are released during eating and the release rate depends on food breakdown dynamics in the mouth. Two sequential studies were designed to explore the flavor perception of the same flavor in different encapsulation systems. The studies were focused on the interactions between encapsulation technology, particle size and breakdown processes in the mouth. A peppermint flavor was used as a model flavor and encapsulated with different technologies (spray drying, melt extrusion and fluidized bed drying). The encapsulated flavors and a selected combination were incorporated into a soft chewable candy, keeping the total flavor concentration the same for each sample. The chewable candy samples were presented to naïve panelists (n > 30) for the following two evaluations; (1) comparison of overall flavor perception with a 2-alternative forced choice test; and (2) dynamic evaluation of perceived flavor intensity over time during eating and after swallowing using time intensity. The results showed that the overall and dynamic flavor perceptions are greatly affected by the encapsulation technologies and particle sizes, and can be modulated by combining flavor particles produced by different encapsulation technologies depending on the application and desired flavor profile. The results also showed a large perceived flavor intensity variation between panelists, resembling variation among consumers. In an effort to better understand the relationship between the oral processing patterns and flavor perception, we used the JBMB® typing tool which gives four "Mouth Behavior" groups ("Chewers", "Crunchers", "Smooshers" and "Suckers") and explored to determine whether they would account for the variation. Compared with "Chewers" and "Crunchers", "Smooshers" tended to have a slower increase of flavor intensity during eating and a more gradual drop after swallowing. However, this needs to be confirmed with larger numbers of consumers (including suckers who were excluded in this study because they were not sufficient in numbers) and samples with a longer chew time.

Survival and phosphate solubilisation activity of desiccated formulations of Penicillium bilaiae and Aspergillus niger influenced by water activity

The impact of formulation and desiccation on the shelf life of phosphate (P)-solubilising microorganisms is often under-studied, particularly relating to their ability to recover P-solubilisation activity. Here, Penicilllium bilaiae and Aspergillus niger were formulated on vermiculite (V) alone, or with the addition of protectants (skimmed milk (V + SM) and trehalose (V + T)), and on sewage sludge ash with (A + N) and without nutrients (A), and dried in a convective air dryer. After drying, the spore viability of P. bilaiae was greater than that of A. niger. V formulations achieved the highest survival rates without being improved by the addition of protectants. P. bilaiae formulated on V was selected for desiccation in a fluidised bed dryer, in which several temperatures and final water activities (aw) were tested. The highest spore viability was achieved when the formulation was dried at 25 °C to a final aw >0.3. During three months' storage, convective air dried formulations were stable for both strains, except in the presence of skimmed milk for P. bilaiae which saw a decrease in spore viability. In the fluidised bed-dried formulations, when aw >0.3, the loss in viability was higher, especially when stored at 20 °C, than at aw <0.1. P-solubilisation activity performed on ash was preserved in most of the formulations after desiccation and storage. Overall, a low drying temperature and high final aw positively affected P. bilaiae viability, however a trade-off between higher viability after desiccation and shelf life should be considered. Further research is needed to optimise viability over time and on more sustainable carriers.

Optimization of soybean heat-treating using a fluidized bed dryer

This study was designed to optimize drying and inactivation of heat-labile inhibitors conditions of soybean by using a fluidized bed dryer, in order to shorten treatment time and to reduce losses in end-product quality such as soy flour color and soy protein solubility. The independent variables were initial moisture of soybeans, heating time and temperature of air entering the fluidization chamber. The response variables studied were final moisture of soybeans, inactivation of urease, soy flour color and soy protein solubility. Response surface methodology was able to model the response of the different studied variables. For each response group, relevant terms were included into an equation; the behavior of response was predicted within the experimental area and was presented as a response surface. The results suggested that a combination of soybean initial moisture of 0.14 g/g (wb), treatment time of 3.4 min and hot-air temperature of 136.5 °C could be a good processing combination of parameters for heating soybean using hot-air in order to reduce treatment time and quality losses in soybean flour. Thus, fluidized bed drying technology may be used as an alternative industrial method to eliminate the antinutritional factors.

Modeling moisture diffusivity, activation energy and specific energy consumption of squash seeds in a semi fluidized and fluidized bed drying

This study investigated thin layer drying of squash seeds under semi fluidized and fluidized bed conditions with initial moisture content about 83.99% (d.b.). An experimental fluidized bed dryer was also used in this study. Air temperature levels of 50, 60, 70 and 80 °C were applied in drying samples. To estimate the drying kinetic of squash seed, seven mathematical models were used to fit the experimental data of thin layer drying. Among the applied models, Two-term model has the best performance to estimate the thin layer drying behavior of the squash seeds. Fick's second law in diffusion was used to determine the effective moisture diffusivity of squash seeds. The range of calculated values of effective moisture diffusivity for drying experiments were between 0.160 × 10(-9) and 0.551 × 10(-10) m(2)/s. Moisture diffusivity values decreased as the input air temperature decreased. Activation energy values were found to be between 31.94 and 34.49 kJ/mol for 50 °C to 80 °C, respectively. The specific energy consumption for squash seeds was calculated at the boundary of 0.783 × 10(6) and 2.303 × 10(6) kJ/kg. Increasing in drying air temperature in different bed conditions led to decrease in specific energy value. Results showed that applying the semi fluidized bed condition is more effective for convective drying of squash seeds. The aforesaid drying characteristics are useful to select the best operational point of fluidized bed dryer and to precise design of system.

Prediction of carrot cubes drying kinetics during fluidized bed drying by artificial neural network

This article presents static and recurrent artificial neural networks (ANNs) to predict the drying kinetics of carrot cubes during fluidized bed drying. Experiments were performed on square-cubed carrot with dimensions of 4, 7 and 10 mm, air temperatures of 50, 60 and 70°C and bed depths of 3, 6 and 9 cm. Initially, static ANN was used to correlate the outputs (moisture ratio and drying rate) to the four exogenous inputs (drying time, drying air temperature, carrot cubes size, and bed depth). In the recurrent ANNs, in addition to the four exogenous inputs, two state input and output (moisture ratio or drying rate) were applied. A number of hidden neurons and training epoch were investigated in this study. The dying kinetics was predicted with R(2) values of greater than 0.94 and 0.96 using static and recurrent ANNs, receptively.