Pilot-scale Drying Research Articles

Transport phenomena in pasta drying: a dough-air double domain advanced modeling

In the realm of pasta drying, where precise prediction of temperature and water-content distribution is crucial, the application of modeling and simulation emerges as highly significant. This study endeavors to evaluate operational conditions ensuring the production of a safe, high-quality pasta product. An advanced two-domain model was devised and solved to estimate transport phenomena in both the food and air domains. Unlike conventional models relying on specified interfacial heat and mass transfer coefficients, the proposed model serves as a versatile tool applicable across a broad spectrum of process and fluid-dynamic conditions in real pasta driers. The system of non-linear unsteady-state partial differential equations governing the behavior of a “Rigatone" pasta sample in a drier was solved using the finite elements method to estimate how air characteristics influence drying performance. A pilot-scale drying chamber was used for model validation for inlet air temperature Ta,in=80°C at relative humidity values (RHin) of 50 % and 60 %, with error consistently below 10 %.

Particle morphology and powder properties during spray drying of maltodextrin and whey protein mixtures

Application behavior of spray dried powders such as reconstitution behavior and flowability is indirectly influenced by powder particle morphology. We here investigated the influence of the drying conditions and composition for whey protein (WP), maltodextrin (MD) and their mixtures on particle morphology during pilot-scale spray drying. Even though all powders showed a variety of morphologies, MD powders contained more wrinkled particles and had high bulk density, whereas pure WP powders contained more hollow particles. Mixture powders (75:25 WP:MD) show more hollow particles with increasing inlet temperature, with a lower bulk density. The observed morphologies for different formulations corresponded roughly to previous observations during sessile single droplet drying, but the results indicate that the morphology is also influenced by the faster pilot-scale drying, which was not evident in the slower single droplet drying.

A systematic analysis on tomato powder quality prepared by four conductive drying technologies

Abstract Four pilot-scale conductive dryers, namely a vacuum drum dryer (VDD), a drum dryer (DD), an agitated thin film dryer (ATFD) and a refractance window dryer (RWD), were used to dry tomato puree. Drying induced colour differences between the reconstituted puree and the original puree and strongly affected the volatile and non-volatile profiles of the powders. Principal component analysis (PCA) identified four separated groups corresponding to the different drying methods, indicating that the drying methods caused significant variance in compound profiles. Subsequently, pairwise comparison of different dried powders was performed by partial least square discriminant analysis (PLS-DA). This resulted in a selection of discriminative volatile and non-volatile markers. RWD and VDD produced powders with high volatile markers that may be related to aroma retention. Conversely, DD dried products contained more non-volatile markers that can be related to taste perception. ATFD processed powders had a lower level of discriminant compounds. Industrial relevance Tomato products are frequently thermally processed and dehydrated. However, processing negatively affects the sensory quality of tomato products. In this study, four conductive drying processes, i.e. vacuum drum drying (VDD), drum drying (DD), agitated thin film drying (ATFD) and refractance window drying (RWD) were studied for being energy-efficient drying methods, while suitable for mild (e.g. due to the reduced pressure) drying of pastes and slurries, such as tomato puree. The pilot-scale drying experiments and subsequent statistical analyses of results on quality markers contributed to unravel the impact of the different conductive drying technologies on tomato powder quality. This study may be considered a starting point for selection of conductive drying technologies for the efficient production of high quality tomato powders and other vegetable powders.

Effect of freeze dried, hot air dried and fresh onions on the composition of volatile sulfocompounds in onion oils

The bioactivity of onion, particularly its oil, has gained increasing research attention. Preparation of onion oil is challenging due to its low oil content and abundance of water. In this study, pilot-scale drying combined with laboratory extraction was conducted for sample preparation. GC/MS and solid phase microextraction (SPME) analyses were performed to evaluate the correlation between onion oil and drying. Results showed that drying significantly influenced the sulfocompounds composition of onion oils. Dipropyl disulfide and dispropyl trisulfide were the most abundant compounds in fresh onions (accounting for 68.41% to 93.13% of the total volatile sulfocompounds). The total contents of sulfocompounds in vacuum freeze dried and hot air dried onion powder were 4.96% and 39.79%, respectively, which account for 24.59% to 48.89% of the total content. Dimethyl sulfides and thiophenes were the main compounds in the onion oils. The highest content of sulfocompounds was obtained in the oil of hot air dried powder. Pilot-scale hot air drying was the optimal pretreatment method for onion oil extraction. It enjoys lower energy lost, shorter process time, and higher quality of the oil compared with freeze drying. The results may be helpful for onion oil production and bioactivity evaluation.

Spray Drying of Lactobacillus plantarum WCFS1 Guided by Predictive Modeling

Shelf life of probiotic microorganisms can be retained by drying. Spray drying is an economically interesting alternative to freeze drying with that respect. However, the viability can decrease due to the drying process and testing it is laborious and expensive. This research shows that the viability of Lactobacillus plantarum WCFS1 during pilot scale drying can be predicted with kinetics gathered at a single droplet level. Using this approach, it could be demonstrated that the viability of L. plantarum WCFS1 during spray drying is mainly determined by the combination of temperature and moisture content during the first 0.5 seconds after atomization. The combination of a high moisture content and a high temperature appeared most detrimental to the residual viability. Moreover, it was found to be important to take into account the particle size distribution during atomization when predicting viability, since this has a large effect on the moisture content during this first 0.5 seconds. Finally, it was observed that shelf life during storage was mainly determined by the moisture content of the powder. A lower moisture content resulted in a higher viability. Above a moisture content of 6%, shelf life stability rapidly decreased in the applied maltodextrin (DE = 16) matrix.

Scale Up from Small Oven-Drying Tests of Mineral Concentrate to Pilot-Scale Drying with a Heated Pad

While Fickian diffusion models are commonly used in other applications, there are few reports of them being applied to the batch drying of a mineral concentrate. Diffusion coefficients estimated from small-scale oven-drying tests were used to predict the drying behavior of a concentrate sample 1 m × 1 m in area and 50 cm deep, with a heated bottom pad. These pilot-scale tests included both daily turning of the sample and turning every three days. The excellent quantitative agreement between the predicted and observed pilot-scale behavior gives a high level of confidence in the model predictions and suggests that a Fickian diffusion model is adequate to predict the behavior of mineral concentrates at the low moisture contents used here.

Grape Drying in a Pilot Plant With a Heat Pump

ABSTRACT We describe a pilot-scale drying plant comprising a closed-circuit, hot-air convection chamber with a heat pump. In this plant, food and forest products can be drled with lower energy consumption and over a wider range of air, speeds, temperatures and relative humidities than in conventional driers. Also the dryinq conditions can be controlled independently of external conditions. Under several different sets of drying conditions, we determined the kinetics of dryinq of grapes that had been variously pretreated. The effects of drying conditions and the pretreatment on the drying time and the appearance of the dried product were evaluated. The drying kinetics can be described by a diffusion model.