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Spray drying of sugar-rich foods causes problems, related mainly to low glass transition temperature, which is manifested by high stickiness, lower drying efficiency, and yield. Thus, a number of research papers have been published recently on this topic. This study summarizes the obtained results and indicates possible future directions. The most popular method to overcome the stickiness problem is still the application of carriers. However, in addition to conventional carriers like maltodextrin and gum Arabic, novel carriers are also being tested. The carriers with additional health-promoting properties are the most interesting group. In the material-science approach the application of proteins as anti-stickiness agents can also be mentioned. Moreover, the raw materials can be modified by membrane techniques to reduce sugar content and increase glass transition temperature. In the process-based approach, the main efforts are mostly focused on decreasing of drying temperature. Currently, the use of dehumidified air has been successfully verified as a possible way to reduce drying temperature. The reduction of stickiness achieved by this method allows to minimize the amounts of carriers added into the feed before spray drying. [ABSTRACT FROM AUTHOR]

The present study was undertaken to determine the mechanism of anthocyanin content (ACNs) and related stability of infrared freeze-dried rose flowers using novel ultrasound pretreatments (20 kHz and 45 kHz for 5, 10 and 15 min). Additionally, the impact of such processing on peroxidase, polyphenol oxidase, color, moisture, total phenolic, total flavonoid, anthocyanins degradation during storage and chemical structure of infrared freeze-dried flowers was evaluated quantitatively. Peroxidase in rose flowers was effectively inactivated while polyphenol oxidase was activated very slowly (85, 95.67, 87.33, 77.67, 93, 98, 90.67%) by ultrasound pretreatment at 45 kHz and 20 kHz for 5, 10 and 15 min, respectively. The TPC and TFC of dried rose flowers pretreated by 45 kHz ultrasound (US) was also higher than that of dried roses pretreated by 20 kHz US. Moreover, US at 45 kHz was beneficial for the retention of color and anthocyanins of roses after infrared freeze-drying. In addition, US treatment at 45 kHz for 10 min resulted the lowest ACNs degradation rate during storage. These results demonstrate that US treatment at 45 kHz is a potential technique for improving the stability of anthocyanins during its processing and storage. [ABSTRACT FROM AUTHOR]

This study aims to explore the shrinkage of onion cells, single and multi-layer onion section, and expansion of intercellular pathways during dehydration. For macro and bulk-level studies, moisture analyzer and hot air convective dryer were used, respectively. Shrinkage, size retention, and color changes due to dehydration and rehydration of onion shreds were compared. At micro-level, CaCl2 and water blanched samples dehydrated at 70 °C, citric acid blanched samples dehydrated at 60 and 80 °C showed less shrinkage compared to unblanched samples. On rehydration, single layer section showed comparable cell size and intercellular space retention. Multi-layer section of CaCl2 blanched samples dehydrated at 70 °C retained better structure. At macro-level dehydration, shrinkage of CaCl2 blanched samples was the least. At bulk-level, all blanched samples shrank by 82–90%. Bulk level rehydration at 50 °C achieved better size retention. Blanching resulted a porous structure of onion shreds with an improved rehydration characteristics. [ABSTRACT FROM AUTHOR]

Delivering viable probiotics at adequate doses is essential to exert a beneficial effect on the host organism. However, the viability of probiotics is affected by environmental conditions and biochemical changes during storage and digestion. Drying probiotics into powder form exerts various benefits (e.g. ease of handling, high stability, less space needed for storage, and maintaining cell viability). However, the final product's cell viability and fundamental powder properties are considerably affected by the type of protective material used and the drying technique employed. A comprehensive summary of probiotic drying techniques, protective materials used, mathematical models to predict survival, and powder properties has been discussed in this review. Achievements made using innovative drying methods have also been analyzed. [ABSTRACT FROM AUTHOR]

Pomegranate juice powder could be applied as a valuable ingredient in other food and pharmaceutical products and be accessible throughout the year. In this research, pomegranate juice was spray dried at three maltodextrin levels (25, 35 and 45% w/w) and two inlet air temperatures (124 and 143 °C) and physicochemical and nutritional characteristics of the powder in terms of moisture content, pH value, ash content, color values, total phenolic compounds, along with microstructural properties of the pomegranate juice powders were analyzed. Inlet air temperature just could affect ash content of the powder while maltodextrin level could influence all properties of the final powder. SEM analysis revealed that lower maltodextrin levels and higher inlet air temperatures resulted in smaller but smoother particles. In conclusion, pomegranate juice powders produced at 25% maltodextrin level and 143 °C, with a low moisture content of 3.19%, high ash content of 0.58%, safe pH value of 3.4 and considerable total phenolic compounds of around 903 mg gallic acid/g db, are suitable and nutritionally-rich choices for industrial production. [ABSTRACT FROM AUTHOR]

The aim of this study was to evaluate the physical, physicochemical, rheological, and morphological properties and antioxidant capacity of thyme essential oil encapsulated by spray drying; as well as to verify the effects of the partial replacement of whey protein isolate by maltodextrin and chitosan. The presence of maltodextrin decreased viscosity of the emulsion; decreased moisture, density, and mean volume diameter, and maintained the oil retention percentage and solubility of the microparticles. All treatments showed low hygroscopicity, being chitosan considered an alternative to reduce this parameter. Phenolic monoterpene thymol was characterized as the major constituent in all samples. The carrier agents were efficient in maintaining antioxidant activity when compared to pure thyme essential oil. In general, they showed spherical shapes and smooth surfaces with slight roughness. The mixture of maltodextrin and chitosan, in partial replacement of whey protein isolate, represents a promising opportunity in obtaining thyme essential oil microparticles by spray drying process. [ABSTRACT FROM AUTHOR]

The encapsulation capacity and the polymer blends containing gum Arabic (GA), inulin (IN), and cellulose nanofibrils ginger (CNFG), extracted from the fibrous ginger residues, for the microencapsulation of ginger essential oil by spray-drying technique were evaluated in this study. The addition of CNFG improved the emulsifying properties of the formulations, with an increase in Newtonian viscosity (μ); however, the partial substitution of GA by IN decreased the viscosity. The higher IN levels increased the emulsion droplets in the formulations with and without the addition of CNFG. In addition, the emulsion droplets with smaller size resulted in the formation of pulverized droplets with smaller diameter. The presence of CNFG in the polymer blends exhibited similar instantaneization times and provided greater oil retention of ginger essential oil by spray drying. The oil retention in the formulation containing GA and CNFG was 12.23% higher than the formulation containing only GA. Changes in the retention of the compounds of pure and microencapsulated ginger essential oil were observed by GC-MS, all six major components remained in the final product, however with some variations on the encapsulated essential oil profile. [ABSTRACT FROM AUTHOR]

Nowadays microencapsulation of pigments is widely applied to create stable powders. The aim of this study was to investigate the effect of thermal blanching as a form of pretreatment before pressing and carrier type on stability of microencapsulated carrot juice powder. Raw material used in the study was the carrot variety Kazan. One part of carrots was blanched before pressing the juice. Mixtures of low-crystallized maltodextrin (MD) with Arabic gum (AG) in different proportions (1:1, 2:1) and whey protein isolate (WPI) were used as carriers. Drying was carried out in a spray-drier at inlet air temperature of 160 °C. Two speeds of the disc were used (28,000; 39,000 rpm). Viscosity, soluble solid content, density, and carotenoid content were measured in juice. Water content, water activity, apparent and bulk density, size of particles, morphology, and carotenoid content were tested in powders. Carrot blanching resulted in higher viscosity, without influencing its density or soluble solid content of the juices in comparison with those without pretreatment. In most cases, blanching treatment caused a decrease in carotenoid content and increases in densities and diameters of powder particles. The change of carrier material from MD:AG mixtures to WPI caused an increase in diameter d50 and carotenoid content and decrease in density values. [ABSTRACT FROM AUTHOR]

Anthocyanins, which could be extracted from red rose, are water-soluble natural pigment of higher value. Anthocyanins are, however, known to suffer significant degradation and losses during drying, which is sometimes required prior to pigment extraction. Various pretreatments are here proposed and were tested as means to help preserve anthocyanins during subsequent hot air drying. Fresh rose flowers were dipped in four different solutions (citric acid, CA; ascorbic acid, AA; tartaric acid, TTA; and sucrose, Suc) of different concentrations viz. 0.1%, 1% and 2% w/v). The pretreated flowers were dried at 50 °C. Monomeric anthocyanins and polymeric color percentage of fresh and hot air dried rose were evaluated; color measurement and electronic nose analysis were also conducted. The results showed that 2% TTA resulted in the largest amount of anthocyanins (14.78 ± 0.19 mg/g, dry mass cyanidin 3-glucoside equivalent), which was equivalent to 3.2% loss compared with the amount in the fresh sample. However, the color of the 2%-TTA treated sample was not as bright as those treated by 0.1% TTA, 0.1% Suc and 1% Suc. All dried samples exhibited flavor that is related to biosynthesis compounds such as those produced during Maillard reaction and baking. [ABSTRACT FROM AUTHOR]

The uniformity of microwave-dried bitter gourd slices was poor, and a microwave hot-airflow vibrating drying (MHAVD) apparatus was used to carry out an in-depth elucidation of moisture flow characteristics underlying the variation in dielectric characteristics. Low-field nuclear magnetic resonance and imaging (LF-NMR/MRI) was used to measure the moisture state and distribution during different drying stages, and the relationship model between moisture semaphore and moisture ratio were analyzed. A vector network analyzer was used to measure the patterns in the variation of dielectric characteristics in bitter gourd slices at different drying stages. As a result, the temperature and moisture distribution of bitter gourd slices during MHAVD was uniform caused by hot air and vibration, and the water semaphore in NMR gradually decreased, but the bound water semaphore increased during certain drying stages. There is a significant linear relationship between the total semaphore A2 and the moisture ratio MR in bitter gourd slices per unit dry basis mass in the NMR spectrum (R2 = 0.99). As moisture decreases, the ability of the material to store microwaves and convert electromagnetic energy to heat energy decreases, the ability of the material to absorb microwaves decreases, and the microwave penetration significantly increases. The moisture flow characteristics in bitter gourd slices is related to the variation of dielectric characteristics during MHAVD, and drying uniformity was improved. [ABSTRACT FROM AUTHOR]

The process of drying improves the shelf-life of a range of food products. Considering drying of probiotics, retention of cell viability is challenging, yet crucial. The impact of various drying process on probiotics viability is well documented. This study was aimed to prepare probiotic powders of Lactobacillus plantarum with a suitable combination of prebiotics by refractance window (RW) drying, a variant of the conductive hydro drying technique. Properties of RW dried synbiotic powder were investigated and compared with freeze dried samples. RW dried synbiotic powder showed lesser moisture content, better flowability, and porous flaky structures in its surface morphology. RW dried synbiotics showed acceptable probiotic viability and stability under simulated oral-gastrointestinal conditions. The findings of this study highlight a new approach for commercial production of probiotic powders. [ABSTRACT FROM AUTHOR]

This study investigated the quality and drying kinetics of instant parboiled rice fortified with turmeric (IPRFT) by using hot air (HA) and microwave-assisted hot air (MWHA) drying. The cooked long grain parboiled rice (LGPR) fortified with turmeric was dried with HA at temperatures of 65, 80, 95, and 110 °C. The microwave power density of 0.588 Wg−1 was incorporated for drying with MWHA. Drying was performed until the dried IPRFT reached 16% (d.b.) of moisture content. The quality of the dried IPRFT was evaluated in terms of color, total phenolics content (TPC), total antioxidant capacity (TAC), rehydration ratio, volume expansion ratio, texture and microstructure. The results showed that the incorporation of microwave power with HA drying helped to reduce the drying time by 50% compared to conventional HA drying. A prediction of the moisture ratio by using the Page model provided the best R2 and RMSE in drying kinetics. The drying conditions had small effects on the color, TPC, TAC, and microstructure of the dried IPFRT. The rehydration ratio, volume expansion ratio and texture of the rehydrated IPFRT showed minimal variations from changes in the drying conditions. The TPC and TAC of the dried IPRFT clearly increased compared to the TPC and TAC of the initial LGPR. [ABSTRACT FROM AUTHOR]

A semi-empirical mathematical model of mass transfer was developed to investigate the microwave-assisted fluidized bed drying of Cuminum cyminum L. and to optimize drying condition based on drying rate and energy consumption. Accordingly, the drying kinetics of this seed undergoing microwave-assisted fluidized bed dryer at various microwave output powers (300, 600, 900 W), air velocities (3.60, 5.45, 7.30 m/s), and air temperatures (45 °C, 55 °C, 65 °C) were studied. Concerning the distinctive shape of seeds, we tried to find a convenient and efficient model to evaluate moisture effective diffusivity ( D eff) and activation energy ( E a ). The range of D eff and E a values were estimated to be from 0.382 × 10−10 to 2.746 × 10−10 m2/s for Deff and 8.464 W/g and 44.653 kJ/mol for Ea. [ABSTRACT FROM AUTHOR]

Osmotic dehydration (OD) is one of the conventional methods to increase the shelf-life of vegetables and fruits. However, the operating conditions can adversely affect the organoleptic and nutritional quality of fresh products due to the high sugar uptake during processing and the loss of water-soluble constituents to the osmotic medium. The application of edible films has attracted interest due to their ability to reduce the entry of solutes and simultaneously increase the removal of water during OD treatments. Microwave (MW) is one of the most effective emerging technologies to accelerate dehydration processes in vegetable matrices. This aspect is particularly relevant in strawberries, given its high content in bioactive and nutritional compounds. Thus, the aim of this paper was to assess the influence of edible film application (alginate–lactate) in strawberry slabs during combined OD-microwaves dehydration processes. Samples of 1 cm thickness were treated with sucrose solution (60°Bx, 40 °C, 4 h) and then were dehydrated in a microwave oven (1.2 W/g). The application of alginate–lactate edible films resulted in similar weight and water losses but lower solids gain compared to uncoated samples during OD treatment. OD pre-treated MW-dried strawberry slabs with moisture contents up to 0.15 kg dry basis were obtained after 100 min of MW drying. Besides, the effective diffusional coefficient (De) was estimated for MW drying process, values ranged from 4.5 to 8.8 10−10 m2/s when shrinkage effect was considered, and from 1.1 to 2.3 10−9 m2/s for constant thickness assumption. [ABSTRACT FROM AUTHOR]

At present, microorganisms are mainly preserved by freeze-drying. There is, however, lack of studies conducted on various cheaper yet promising convective air-drying alternatives. Convective air-drying has been proven to produce dried culture with comparable cell survival and final moisture content to that of freeze-drying. This paper aims to draw an understanding to application and suitability of convective air-drying which includes spray, oven, heat pump, fluidized bed, conveyor, and rotary drying to preserve microorganisms. The paper concludes that drying near ambient temperature and the addition of dehydration protectants are important to obtain satisfactory drying quality. [ABSTRACT FROM AUTHOR]