Single droplet experimentation on spray drying:evaporation of sessile droplets deposited on a flat surface

Abstract: Individually dispensed droplets were dried on a flat surface to mimic the drying of single droplets during spray drying. A robust dispensing process is presented that generates small droplets (dp>150 µm). A predictive model based on Bernoulli’s law accurately describes droplet size with varying liquids and dispensing parameters. Shrinkage of the droplets, monitored with a camera, was described using mass balance equations. Finally, a Sherwood correlation was derived to describe the mass transfer coefficient for sessile droplets. This work forms the basis for the development of a platform for high throughput experimentation on spray drying

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

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

Single droplet drying for optimal spray drying of enzymes and probiotics

Spray drying is a mild and cost-effective convective drying method. It can be applied to stabilise heat sensitive ingredients, such as enzymes and probiotic bacteria, albeit in industrial practice for example freeze drying or freezing are often preferred. The reason is that optimum drying conditions and tailored matrix formulations are required to avoid severe heat damage leading to loss in enzyme activity or reduced survival of bacteria. An overview is provided on the use of protective carbohydrate-rich formulations in the spray drying of enzymes and probiotics. Subsequently, single droplet drying experimentation methods are reviewed for mapping drying trajectories of individual droplets. The advantage of these is to provide insight in inactivation kinetics of enzymes and probiotics and thus contribute to unravelling of stabilisation mechanisms. Finally, it is shown that detailed modelling of single droplet drying and insight in micro-structural changes during drying can be complementary to the experimental single droplet approaches

Agitated thin-film drying of spinach juice

[EN] Agitated thin film dryers (ATFD) has been considered as an effective technology for drying viscous liquid foods, pastes or pureed foods. In this study, a lab-scale ATFD was developed and applied for drying of juices from spinach leaves at varying temperature (60 – 90 ˚C), feed rate (0.3 – 0.5 kg/h) and blade rotation speed (300 – 600 RPM) combinations. Juice suspensions were successfully dried into powder with a moisture content ranging from 0.049 to 0.114 kg/kg total. Increasing the wall temperature and feed rate were found to improve the specific evaporation rate and evaporation rate of the ATFD, respectively. The blade rotation speed had limited effect on the water removal rate, while it played a crucial role in powder formation.Qiu, J.; Boom, RM.; Schutyser, M. (2018). Agitated thin-film drying of spinach juice. En IDS 2018. 21st International Drying Symposium Proceedings. Editorial Universitat Politècnica de València. 1317-1324. https://doi.org/10.4995/IDS2018.2018.7515OCS1317132

Recent developments in functional bakery products and the impact of baking on active ingredients

[EN] Active ingredients can be supplemented into a bakery product to produce functional food. However, the preservation of the functionality of these active ingredients during baking remains a challenge for food industry. A deeper understanding of the underlying interactions between functionality and baking is highly desired for developing innovative functional bakery products with significant health benefits and high product quality. In this work, recent advances in the development of functional bakery products are reviewed. The interactions between the baking process and the functionality of the supplemented active ingredients are discussed and the perspective of future research is addressed.Zhang, L.; Boom, R.; Chen, X.; Schutyser, M. (2018). Recent developments in functional bakery products and the impact of baking on active ingredients. En IDS 2018. 21st International Drying Symposium Proceedings. Editorial Universitat Politècnica de València. 667-674. https://doi.org/10.4995/IDS2018.2018.7593OCS66767

Glucosylsphingosine Is a Highly Sensitive and Specific Biomarker for Primary Diagnostic and Follow-Up Monitoring in Gaucher Disease in a Non-Jewish, Caucasian Cohort of Gaucher Disease Patients

Gaucher disease (GD) is the most common lysosomal storage disorder (LSD). Based on a deficient β-glucocerebrosidase it leads to an accumulation of glucosylceramide. Standard diagnostic procedures include measurement of enzyme activity, genetic testing as well as analysis of chitotriosidase and CCL18/PARC as biomarkers. Even though chitotriosidase is the most well-established biomarker in GD, it is not specific for GD. Furthermore, it may be false negative in a significant percentage of GD patients due to mutation. Additionally, chitotriosidase reflects the changes in the course of the disease belatedly. This further enhances the need for a reliable biomarker, especially for the monitoring of the disease and the impact of potential treatments.Here, we evaluated the sensitivity and specificity of the previously reported biomarker Glucosylsphingosine with regard to different control groups (healthy control vs. GD carriers vs. other LSDs).Only GD patients displayed elevated levels of Glucosylsphingosine higher than 12 ng/ml whereas the comparison controls groups revealed concentrations below the pathological cut-off, verifying the specificity of Glucosylsphingosine as a biomarker for GD. In addition, we evaluated the biomarker before and during enzyme replacement therapy (ERT) in 19 patients, demonstrating a decrease in Glucosylsphingosine over time with the most pronounced reduction within the first 6 months of ERT. Furthermore, our data reveals a correlation between the medical consequence of specific mutations and Glucosylsphingosine.In summary, Glucosylsphingosine is a very promising, reliable and specific biomarker for GD

Survival of encapsulated Lactobacillus plantarum during isothermal heating and bread baking

The effect of encapsulation on the survival of Lactobacillus plantarum during isothermal heating and bread baking was investigated. Four encapsulating materials were evaluated, i.e., reconstituted skim milk (RSM), gum arabic (GA), maltodextrin (MD) and inulin. Freeze dried bacteria survived better in GA and RSM matrices during isothermal heating at 90 °C, which was explained by their high glass transition temperatures and physical entrapment of the bacterial cells in their dense microstructure. The survival of bacteria in bread during baking depended on the approach used to incorporate probiotics and physical properties of encapsulating materials, which was related to the exposure of the bacterial cells to moist-heat. Maximum survival of probiotic bacteria (>108 CFU/g bread) was achieved after 15 min baking at 100 °C when the RSM-probiotic powder was distributed on the dough surface. Furthermore, A Weibull model could describe the general trend of the inactivation kinetics of bacteria during isothermal heating (at 60, 75 and 90 °C) as influenced by the initial moisture content of the RSM-water mixtures (0.05, 0.60 and 0.90 kg/kg). Future development of bakery products with alive probiotic bacteria could benefit from this work