Binderless agglomeration enhances spray-drying efficiency by inducing in situ particle growth without external binders. Two amorphous powders, skim milk powder (SMP) and maltodextrin DE21 (MD21), were processed in a two-stage spray dryer with an integrated fluidized bed, while outlet temperature, fluidizing-air humidity, and feed total solids (TS) were varied. Moisture sorption, growth kinetics, and morphology were quantified using in-line fiber-optic spatial filter measurements and near-infrared spectroscopy (NIR). A sintering model linked the temperature offset above the glass transition Delta Tg=T-Tg to sinter-bridge formation and agglomerate growth. Higher relative humidity (RH) and Delta Tg promoted agglomeration, particularly for SMP due to its lower Tg and higher stickiness. The model predicted stable, fluidizable agglomerates by combining process variables and material properties that are suitable for stable binderless agglomeration and downstream processing.

By producing a storable intermediate during cheese processing by drying new flexibility is gained. Thereby, cheese can be produced detached from the production of intermediate granules and whey. The dairy gel granules tend to agglomerate without agitation and oil-out or plasticise at high temperatures making them a highly challenging product for drying. Contact drying in a modified Lodige ploughshare mixer was performed due to the possibility to apply sufficient agitation and to operate under vacuum. A design of experiments with varying granule types and jacket temperatures was performed and different responses analysed regarding drying efficiency. A higher drying temperature resulted in higher drying rates and consequently lower final moisture contents and aW values. For more insight into the drying process, two different in-line measurement techniques were installed and calibrated for monitoring of the moisture content. While the capacitive moisture measurement could not be calibrated, the near-infrared spectroscopy was successfully calibrated with a data selection via partial least squares regression with 2nd derivative pre-processing and seven factors as a first step to a smart and dynamic drying process, where the drying parameters can be adapted to the current product properties of the granules.

Swelling of food powders upon contact with water is a phenomenon with high relevance for powder reconstitution. Detailed knowledge about swelling kinetics of food powders and factors influencing these kinetics is key to improving product formulations and process conditions. This study focuses on the impact of particle size on swelling kinetics. Two food powders (gelatin powder and soy protein isolate) were studied regarding their maximum water uptake and swelling speed. Gelatin powder was analyzed using NMR (nuclear magnetic resonance) relaxometry, while soy protein isolate was investigated by laser diffraction. Kinetic models were used to determine swelling rate and maximum and equilibrium water uptake. For a non-dissolving material (gelatin powder), the swelling rate was found to decrease with increasing particle size, while the equilibrium water uptake was independent of size. For dissolving material (soy protein isolate), both the swelling rate and the maximum water uptake decreased with increasing size. The equilibrium water uptake was not correlated to particle size.

This study examines forced, binder-based, bottom-spray agglomeration in the integrated fluidized bed of a multi-stage spray drying process. A two-stage spray dryer with fines return is coupled with a binder-based agglomeration stage in the integrated fluidized bed, yielding a multi-stage process. The process window was defined and controlled through temperature–moisture offsets of 7, 12 and 17 K above the glass transition temperature. Experiments were carried out with two binder systems, water and a 20% skimmed milk solution, at fluidized bed temperatures of 40 °C, 52 °C and 65 °C. In-line monitoring by near-infrared spectroscopy and particle size measurement enabled binder dosing to be adjusted during operation and product moisture to be kept stable. The main driving force for particle growth was the temperature–moisture offset, which resulted in an increase in the Sauter mean diameter from 44μm to 93μm. Meanwhile, fluidized bed temperature and binder type acted as smaller but statistically significant factors. Larger particles were consistently associated with lower tapped density and reduced attrition stability, revealing a practical trade-off between particle size, tapped density and mechanical robustness. X-ray microtomography renderings qualitatively confirmed the shift from loosely packed to denser agglomerate structures as stickiness increased. Overall, these results provide a transferable in-line monitoring and control framework for adjusting particle size and structure in an integrated binder-based fluidized bed agglomeration process.

Smart and dynamically controlled drying enables processing of challenging materials. Dairy gel granules are an intermediate material during cheese production, which can be dried for more flexibility regarding place and time of production. However, agitation is necessary during drying due to the granules' tendency to build agglomerates, as well as low temperatures due to risk oiling-out and plasticizing at high temperatures. The resulting long and inefficient fluidized bed drying process shall be improved by using in-line monitoring of the moisture content via a near-infrared (NIR) sensor calibrated with partial least squares (PLS) regression. Using that moisture content and the correlation to a changing temperature of the irreversible gel sol transition, the drying temperature can be adapted in-line to be just below that temperature. Comparison of these dynamically controlled drying trials to reference trials with a static drying temperature showed drier products within the same drying time, ergo higher drying rates. Thereby, the feasibility of the concept could be proven.

Material swelling during food powder reconstitution is a key mechanism involved in undesirable lump formation. The choice of food material often defines the extent of powder swelling and associated problems but the swelling itself is seldom characterized. Quantitative data on swelling kinetics of biopolymers relevant for food systems can help improve product and process design. However, such data is scarce due to the complexity of food powder composition and a lack of reliable measurement methods. This study employs three measurement methods (measurement of displaced volume in a normal force rheometer, image analysis of light microscopy data, particle size measurement) to measure volume changes of gelatin, pea protein concentrate, soy protein isolate and skim milk powder. Data is compared with NMR relaxometry data of a previous study and assessment of the methods regarding their ability to quantify swelling is conducted. For gelatin, data obtained by NMR relaxometry, displaced volume measurement and image analysis were comparable. While no swelling could be measured with the chosen methods for skim milk powder, swelling was clearly observable with all methods for plant-based proteins. However, resulting maximum volume increase ranged from 4 to 15 m3/m3 depending on material, water availability and dispersion conditions.

Superheated steam spray drying has the potential to significantly reduce the net energy consumption of drying processes. Food products have been successfully dried in laboratory scale systems with unique properties. In this paper the technological challenges for industrial applications are discussed. A closed-loop superheated steam spray dryer set up is introduced at pilot plant scale with focus on heat-sensitive food materials. The design of the drying chamber is a novel approach to meet the specific characteristics of such materials for superheated steam spray drying. The discharge of the dry powder from the steam atmosphere is realized by a novel annular venturi nozzle system, which operates fully continuously and rapidly. These adaptations ensure a low oxygen content in the system, protection of the feed and condensation-free powder discharge.

The effects of dextrose equivalent (DE) and drying air temperature (Tin) on the morphology and bulk density of spray-dried maltodextrin powders were investigated on a large pilot-scale spray dryer. Maltodextrin DE6, DE21, and DE38 solutions of 25 w/w% were dried at least six times at 160 degrees C and 180 degrees C. Particle morphologies were analyzed using scanning electron microscopy and advanced morphology analysis. DE6 powders mainly consisted of spherical particles, supplemented by particles with smooth undulations, whereas DE21 and DE38 powders predominantly contained wrinkled and dented particles. DE21 particles displayed wrinkles with sharper edges, whereas DE38 particles were more creased. Besides particle morphology, bulk density was evaluated. Increasing the Tin resulted in smaller, less wrinkled particles with higher circularity. The lowest loose bulk density, 351 kgm-3, was obtained at low DE and high Tin. Increasing DE and decreasing Tin increased the loose bulk density to 449 kgm-3. A similar trend was observed for tapped and apparent particle densities. Results could be linked to the viscoelastic behavior of the maltodextrins, drying rates imposed by drying conditions, and morphologies of maltodextrins previously observed during earlier single droplet drying (SSD) studies.

Superheated steam spray drying has the potential to significantly reduce the net energy consumption of drying processes. Food products have been successfully dried in laboratory scale systems with unique characteristics. Thermal modification of starch for food applications by superheated steam spray drying is therefore an energy efficient alternative to existing processes. A native potato starch was used to demonstrate the applicability and evaluate the properties of the resulting cold swelling and cold dissolving pregelatinised potato starch. The thermal effects of atomisation and drying under superheated steam atmosphere were evaluated using a closed- loop superheated steam spray drier at pilot plant scale with inlet temperatures between 170 degrees C and 230 degrees C. The resulting cold-swelling potato starch granules are intact and the gel has an initial viscosity that is twice that of the drum-dried reference material at the same concentration. The viscosity of the resulting gel is boiling-stable offering opportunities for instant products that can be served at elevated temperatures for consumption.

Fouling reduces spray dryer operability. The impact of different configurations of a spray dryer on operability and nozzle-zone agglomeration stimulated by dry powder dosing was investigated through a combination of CFD simulations and pilot-scale experiments. Included were two positions of the nozzle and dry powder introduction, and two degrees of air swirl. Air flows and droplet trajectories were simulated and a particle collision model was built in. The experiments were executed using a single stage co-current spray dryer with concentrical fines return. A high nozzle position (6 cm below the air inlet) resulted in undesired fouling due to an upward air flow causing wet droplets to collide with the roof. The operability was improved by lowering the nozzle position 25 cm as there was less fouling. With a low nozzle position, the degree of air swirl only had a limited effect on fouling. Surprisingly, agglomeration did not seem to be significantly affected by air distribution in both the simulations and the experiments. This means that there is some freedom in the design of a spray dryer in terms of agglomeration. Overall, the findings highlight the importance of well-designed spray drying operations to reduce fouling and thus minimize product waste.

Freeze-dried ginger (Zingiber officinale) is renowned for its high quality, but it is expensive. As an alternative, spray drying can be explored for producing ginger powder. However, sugar rich feed solutions can lead to stickiness development during the process. Adding carrier materials increases costs and labeling. Accordingly, a split-stream spray-drying process was developed, where ginger fibers in their natural composition were reintroduced as a carrier material into the spray-drying process. The inlet and outlet temperatures were set at 220 and 80 °C, respectively, for optimal aroma retention. Using a stir bar sorptive extraction-gas chromatography-mass spectrometry-olfactometry, the results revealed that reintegrating ginger fibers significantly increased the concentration of eight key odorants. Although freeze-dried ginger retains more aroma, the total concentration of twenty-seven odorants in the developed spray-dried ginger was 1.9 times higher compared to frozen ginger.

The positive effect of protein drying aids that reduce the stickiness of sugar-rich products on the spray drying yield is known. However, as agglomeration also depends on stickiness, one can expect an effect of these drying aids on interparticle collisions. Therefore, the effect of protein addition to maltodextrin systems on agglomeration and yield in spray drying was investigated using single droplet drying and pilot-scale spray drying experiments. Single droplet drying was used to compare the sticking regimes of whey and pea proteins at different concentrations. Adding protein increased the chance of creating agglomerates upon forced collisions between a drying droplet and a glass bead. This was reflected in an increased fraction of agglomerated particles in pilotscale experiments with injection of fines. Pea protein decreased the fraction of non-agglomerated primary particles from 38% to 22% when the protein content in the liquid feed was 50 g/kg dry basis. In pilot-scale spray drying, protein addition improved the yield. Industrially, these results can be used to steer formulations regarding agglomeration and yield.

Quantitative data on powder swelling kinetics is essential to understand phenomena occurring during rehydration, e.g. lump formation. In this study, swelling kinetics of food powders (gelatin powder, soy protein isolate, pea protein concentrate) were quantified by Nuclear Magnetic Resonance (NMR) relaxometry. Using gelatin plates as a model system, it was successfully demonstrated that NMR relaxometry is an efficient, non-destructive method to study swelling kinetics of non-dissolving systems with moderate swelling speeds. For plant-based proteins, high swelling speeds were observed. The obtained maximum water uptake due to swelling was 5.10 ± 0.80 g/g for soy protein isolate and 3.93 ± 0.16 g/g for pea protein isolate, which is in the expected range. Measurement speed was too low to resolve early swelling kinetics (below 84 s), evaluation was more elaborate and results less unambiguous.

For accurate description of particle structure, single particle properties are required so that the properties of interest can be expressed as distributed parameters. X-Ray microtomography of the powder bed with subsequent particle separation can be used for this purpose. In this paper, a new algorithm for X-Ray microtomography images of spray dried particles was introduced since standard methods tend to fail if the particle size distribution is broad. The algorithm is based on 2D shape classification and subsequent 3D reconstitution of the particle using only a shape classifier as free parameter. The proposed algorithm was validated successfully. Using the algorithm, single particle porosities were obtained, which ranged from 0 to 70%. Prerequisites for the application of the algorithm are that a shape classifier can be set and that the 3D shape is regular.

Protein denaturation during spray drying is critical for high-quality food powders. This study investigated the influence of particle size on protein denaturation using phycocyanin as a marker. The effect of particle size was investigated at three different air outlet temperatures, with the inlet air temperature held constant. For each temperature combination, different nozzles were utilized to obtain varying particle sizes. Denaturation increased with higher outlet air temperature and larger particle size, up to a size of 40 & mu;m. This increase in denaturation with particle size was attributed to faster drying rates and the absence of denaturation once particles are dry. Particle size had a similar magnitude of effect as outlet air temperature. For larger particles, a plateau in denaturation was observed due to a prolonged constant drying rate regime. It can be assumed that conditions that retain phycocyanin are also suited for the retention for less thermolabile proteins.

Crucial for achieving premium agglomerated powder products through spray drying is that the primary particle morphology and the degree of agglomeration can be controlled. However, the costs of trial runs and the wide range of products properties complicate achieving this control of particle structure during spray drying. Single droplet drying approaches are employed to study the development of the primary particle morphology and the collision behavior of droplets under well-defined conditions. These studies shed light on the underlying mech-anisms but have been related less often to realistic drying and especially agglomeration. This review focuses on the potential and limitations of single droplet drying approaches to unravel the evolution of primary particle morphology and nozzle-zone agglomeration phenomena during spray drying. We discuss advances in single droplet drying approaches and how to combine these with pilot-scale spray drying to obtain the desired particle structures.

Industrial use of ginger after peeling results in large amounts of agro-waste. To provide a basic reference for the sustainable processing of ginger products as a spice, we investigated the differences between unpeeled ginger, peeled ginger, and corresponding ginger peel, in terms of aroma, sensory profiles, and nutrition relevant physicochemical properties. The results showed that the total concentrations of identified odor-active compounds in unpeeled ginger, peeled ginger, and ginger peel were 876.56, 672.73, and 105.39 mg/kg, respectively. Unpeeled ginger exhibited more intense citrus-like and fresh impressions compared to peeled ginger, revealed by descriptive sensory analyses. This is relevant to the high odor activity values of odorants such as beta-myrcene (pungent, citrus-like), geranial (citrus-like), citronellal (citrus-like, sourish), and linalool (floral, fresh). In parallel, unpeeled ginger contained higher total polyphenol (84.49 mg/100 g) and total sugar content (33.4 g/kg) in comparison with peeled ginger (76.53 mg/100 g and 28.6 g/kg).

Makespan dominates the manufacturing expenses in bakery production. The high energy consumption of ovens also has a substantial impact, which bakers may overlook. Bakers leave ovens running until the final product is baked, allowing them to consume energy even when not in use. It results in energy waste, increased manufacturing costs, and CO 2 emissions. This paper investigates three manufacturing lines from small and medium-sized bakeries to find optimum makespan and ovens’ idle time (OIDT). A hybrid no-wait flow shop scheduling model considering the constraints that are most common in bakeries is proposed. To find optimal solutions, non-dominated sorting genetic algorithm (NSGA-II), strength Pareto evolutionary algorithm (SPEA2), generalized differential evolution (GDE3), improved multi-objective particle swarm optimization (OMOPSO), and speed-constrained multi-objective particle swarm optimization (SMPSO) were used. The experimental results show that the shortest makespan does not always imply the lowest OIDT. Even the optimized solutions have up to 231 min of excess OIDT, while the makespan is the shortest. Pareto solutions provide promising trade-offs between makespan and OIDT, with the best-case scenario reducing OIDT by 1348 min while increasing makespan only by 61 min from the minimum possible makespan. NSGA-II outperforms all other algorithms in obtaining a high number of good-quality solutions and a small number of poor-quality solutions, followed by SPEA2 and GDE3. In contrast, OMOPSO and SMPSO deliver the worst solutions, which become pronounced as the problem complexity grows.

Soy whey is becoming a worldwide issue as a liquid wastestreamthat is often discarded after tofu, soy protein, and soy-based dairyalternative manufacturing. This study established a model to producea bioflavor and mycoprotein using fermentation of soy whey by a basidiomycete Ischnoderma benzoinum. Under the dedicated controlof a fermentation system, an intense almond-like and sweetish aromawas perceived by a trained sensory panel (n = 10)after fermentation of pure soy whey within 20 h. By application ofdirect immersion-stir bar sorptive extraction combined withgas chromatography-mass spectrometry-olfactometry (DI-SBSE-GC-MS-O),around 1.0 mg/L benzaldehyde and 1.1 mg/L 4-methoxybenzaldehyde impartinga pleasant almond-like odor note were determined in the fermentedsoy whey with I. benzoinum. Concurrently,a certain of amount of the dry mass of I. benzoinum was accumulated with 73.2 mg/g crude protein and seven essentialamino acids.

The investigation of single droplets in the acoustic levitator has been increasingly used in recent years to study their behavior during the drying process. By selectively flowing conditioned air onto the droplets and controlling the ambient conditions, it is possible to observe the drying behavior without contact under conditions similar to those prevailing in spray drying. A CMOS camera is used to continuously measure the change in volume that occurs during drying and an infrared camera is used to measure the surface temperature of the droplets/particles. The data are used to calculate the drying kinetics and the drying parameters with a high degree of accuracy. In addition to the suspensions investigated so far, the drying behavior of the solutions should be examined more closely. Since the drying kinetics of the solutions are complex and depend on the concentration and the material properties, two different maltodextrins (DE <3 and DE 21) and their solutions in different concentrations at different temperatures were investigated. Maltodextrin is a product that dries mainly in the falling rate period. From the results, conclusions were drawn concerning the structural development of the final particle and the average viscosity of the solution during the drying process.