Drying strategies of spent coffee grounds using refractance window method.

The objective of this study was to evaluate, during the drying of spent coffee grounds, the application of pretreatments with ethanol and the application of ultrasound assisting the refractive window (RW) drying, and to compare with convective drying by hot air (AC). The effect on the kinetics parameters of the Fick and Page models were evaluated, as well as on the content of total phenolics and antioxidant capacity. For AC drying, samples of spent ground coffee were prepared in the form of fixed rectangular beds 0.7 cm high, which were placed on polyester sheets and pretreated up to 10 times sprayed with ethanol, then dried by AC at 80 °C and 0.8 m/s. For RW drying, the samples prepared in the same way as for AC were used. For this case, the application of ethanol as pretreatment and the use of ultrasound during process were tested. As results, regardless of the conditions applied, drying by RW was up to 50 % faster, evidenced in the highest values of effective diffusivity (from the Fick model) and the kinetic parameter (from the Page model). Regarding the treatments applied and their effect on the drying kinetics, any treatment had a significant effect on AC drying. On the contrary, the strategies applied in RW drying had significant effects, both the application of pretreatment with ethanol as well as the application of ultrasound assisting the process accelerated the drying kinetics. However, the treatment with ethanol and RW drying was the one that best preserved the phenolic compounds and the antioxidant capacity in the samples. Therefore, these strategies could be a good option to improve RW drying by accelerating the process and preserving the bioactive compounds in the spent coffee grounds for subsequent utilization.

Combining ultrasound, vacuum and/or ethanol as pretreatments to the convective drying of celery slices.

This work studied three emerging approaches to improve the convective drying (50 °C, 0.8 m/s) of celery. Celery slices of 2 mm thick were pretreated for 5 min using ultrasound (32 W/L, 40 kHz), vacuum (75 kPa vacuum pressure) and ethanol (99.8% v/v, as drying accelerator) applied individually or in combination. To evaluate individual effects of ultrasound and vacuum, the treatments were also performed with distilled water or air medium, respectively. Moreover, the cavitational level was characterized in each condition. Drying kinetics was evaluated tending into account the drying time required by each treatment and the Page's model parameters. In addition, microstructural effects and shrinkage were evaluated. As results, ethanol combined with ultrasound significantly improved drying kinetics reducing drying time by around 38%. However, vacuum pretreatment did not affect drying kinetics even in combination with ethanol and/or ultrasound. Microstructural evaluation did not evidence cell disruption, suggesting changes in intercellular spaces, pores and/or cell wall permeability. The use of ethanol and vacuum showed a greater effect on shrinkage after pretreatment and after drying, respectively. In conclusion, at the studied conditions, the drying acceleration by vacuum and ultrasound is lower compared to the effect produced using ethanol.

Essential Oils Extracted from Organic Propolis Residues: An Exploratory Analysis of Their Antibacterial and Antioxidant Properties and Volatile Profile.

The industrial processing of crude propolis generates residues. Essential oils (EOs) from propolis residues could be a potential source of natural bioactive compounds to replace antibiotics and synthetic antioxidants in pig production. In this study, we determined the antibacterial/antioxidant activity of EOs from crude organic propolis (EOP) and from propolis residues, moist residue (EOMR), and dried residue (EODR), and further elucidated their chemical composition. The EOs were extracted by hydrodistillation, and their volatile profile was tentatively identified by GC-MS. All EOs had an antibacterial effect on Escherichia coli and Lactobacillus plantarum as they caused disturbances on the growth kinetics of both bacteria. However, EODR had more selective antibacterial activity, as it caused a higher reduction in the maximal culture density (D) of E. coli (86.7%) than L. plantarum (46.9%). EODR exhibited mild antioxidant activity, whereas EOMR showed the highest antioxidant activity (ABTS = 0.90 µmol TE/mg, FRAP = 463.97 µmol Fe2+/mg) and phenolic content (58.41 mg GAE/g). Each EO had a different chemical composition, but α-pinene and ß-pinene were the major compounds detected in the samples. Interestingly, specific minor compounds were detected in a higher relative amount in EOMR and EODR as compared to EOP. Therefore, these minor compounds are most likely responsible for the biological properties of EODR and EOMR. Collectively, our findings suggest that the EOs from propolis residues could be resourcefully used as natural antibacterial/antioxidant additives in pig production.

Combining Ionizing Irradiation and Ultrasound Technologies: Effect on Beans Hydration and Germination.

The present work studied, for the first time, the effect of two technologies on the hydration and germination process of beans: ionizing irradiation and ultrasound. In addition, this work proposed a possible biological effect of ultrasound to describe its effect on grain hydration. Carioca beans were irradiated at doses of 2.3 and 3.8 kGy using γ-rays, establishing different metabolic activities for the beans. Then, they were hydrated with and without the ultrasound technology (91 W/L and 25 kHz) at 25 °C. Both the hydration and germination kinetics were evaluated considering the application of both technologies alone and in combination. As results, irradiation did not significantly affect (P > 0.05) the hydration rate, the equilibrium moisture, or the lag phase time, but ultrasound affected them, reducing 50% of the processing time. On the other hand, only the equilibrium moisture was slightly reduced by the interactive effect of irradiation and ultrasound technology, which was discussed based on different metabolism levels. Furthermore, the germination process of carioca bean was hindered by both the studied variables, reducing its germination capacity to 0% in some cases. Therefore, by studying the effect of ultrasound on beans with different active metabolism (due to different irradiation doses), it was suggested that both physical and biological mechanisms are involved during hydration process and that both can be affected by ultrasound. Further, irradiation could be used on carioca beans with objectives such as avoid germination, insects, and microorganism's growth, without an important effect on the hydration kinetics. PRACTICAL APPLICATION: Ultrasound technology has demonstrated to accelerate the soaking process of several legume grains. However, sometimes, grains are irradiated for disinfestation purpose to improve their shelf life. Indeed, irradiation can change the grain properties as the cooking time, hydration time, and germination capacity. Therefore, this work verified if irradiation changes the desirable effect of ultrasound on grain processing: soaking and germination. Moreover, this work novelty is also based on describing the phenomena: by proposing a possible biological effect, further approaches to improve the grain processing can be achieved.

Irradiation of mung beans (Vigna radiata): A prospective study correlating the properties of starch and grains.

In this work, the effect of Gamma-irradiation was evaluated on the characteristics of mung bean (Vigna radiata) grains and starches, considering doses up to 5 kGy. For this purpose, the starch structure and properties were evaluated, as well as the grains' hydration, germination and cooking. The irradiation process was able to change the characteristics of both mung bean starches and grains. The starch structure was partially changed, presenting smaller molecules and small changes in the granule morphology. No alterations were observed in the starch X-ray diffraction pattern, while lower pH was achieved. Considering the starch properties, it was observed lower water retention ability at 75 °C, lower apparent viscosity, higher paste clarity and, in general, harder and less viscous gels. The ionizing radiation accelerated the hydration, reduced the germination capacity and improved cooking time of the mung bean grains. The results proved the efficacy of using ionizing radiation, at the doses applied in this work, to desirably modify the mung bean starch and grains.

Structural changes caused by ultrasound pretreatment: Direct and indirect demonstration in potato cylinders.

This work aimed to demonstrate the internal and external structural changes in potato cylinders caused by different times of ultrasound pretreatment. In addition, the structural changes were associated with the viscoelasticity and mass transfer. For which, potato cylinders were immersed in distilled water and pretreated with and without ultrasound (ultrasonic bath of 91 W/L and 25 kHz) up to 120 min. Then, the microstructure was evaluated by stereoscopic observation as a direct method, and by viscoelasticity and mass transfer evaluation (pigment diffusion and drying) as indirect methods. Both external and internal structure of the material were evaluated. As results, it was demonstrated the formation of microchannels inside the potato tissue as well as the surface erosion caused by ultrasound, especially after 60 min of pretreatment. Further, it was observed that the product viscoelasticity is affected by the ultrasound pretreatment reducing the elasticity. In addition, the mass transfer on the cylinders was improved by ultrasound pretreatment. The pigment transfer was enhanced, demonstrating the acoustic erosion at the sample border. Furthermore, the drying process was accelerated by ultrasound, demonstrating the reduction of the internal resistance to water transfer. Finally, it was observed that high structural changes on the potato cylinders can bring some disadvantages such as changes on the color and severe shrinkage. This work concluded that the structural changes caused by ultrasound can be evidenced directly and indirectly. Furthermore, different structural changes took place, on both inside and outside of the vegetable sample. However, despite ultrasound improves further process, especially those that involve mass transfer, the parameters time and ultrasonic power must be optimized to obtain desirable results without reducing the product quality.

The ultrasound assisted hydration as an opportunity to incorporate nutrients into grains.

Hydration is an important but long step in processing beans. Consequently, any ways of taking advantage of this processing time are desirable. One possibility is to fortify the beans during the hydration process, especially with water-soluble nutrients. This work studied the incorporation of iron into beans during hydration with and without ultrasound, describing the kinetics of water and iron uptake, the entrance pathway and its effect on germination and the cooking process. For that, carioca beans were soaked in ferrous sulfate solution (0.271% w/v) with and without ultrasound (91 W/L; 25 kHz) at 25 °C. It was demonstrated that iron could be incorporated during the hydration process, describing a similar kinetics behavior to the water uptake. In addition, ultrasound accelerated this process, achieving 60.1 mg Fe/100 g w.b. after 510 min of process, in contrast to 34.4 mg Fe/100 g w.b. when the beans were hydrated without ultrasound. Finally, by hydrating the beans with ferrous sulfate, the cooking process was accelerated, which is desirable. However, the capacity for germination of the beans was reduced. In conclusion, the hydration process time can be used to fortify the beans with iron (and, possibly, other water-soluble nutrients). Nevertheless, future studies must be performed to determine if the incorporated iron is bioavailable and bioaccessible, as well as how relevant this approach is as a nutritional policy.

Correlating the properties of different carioca bean cultivars (Phaseolus vulgaris) with their hydration kinetics.

This work explained how the intrinsic properties of beans affects the hydration process. For that, different properties of six cultivars of carioca bean (a variety of common bean) were analyzed to verify the correlation with their hydration kinetics characteristics (hydration rate, lag phase time and equilibrium moisture content), using a Multiple Factorial Analysis (MFA): the chemical composition (starch, protein, lipids, minerals (Mg, P, S, K, Ca, Mn, Fe, Cu, Zn), functional groups from the seed coat analyzed by FT-IR), physical properties (size, 1000 grain weight, seed coat thickness, energy to penetrate the bean) and microstructure. Only few properties correlated with the hydration kinetics characteristics of the studied bean, comprising both composition and structure. The fat content, potassium content, specific surface, and the protein to lipids ratio correlated with the lag phase time, which is related with the seed coat impermeability to water. The necessary energy to perforate the seed coat correlated negatively with the hydration rate. It was concluded that the hydration of beans process is a complex phenomenon and that despite being from the same variety of legume, any change due to agronomic enhancement may affect their hydration process kinetics.

The Hydration of Grains: A Critical Review from Description of Phenomena to Process Improvements.

Hydration is a crucial step during grain processing. It is performed prior to many other processes, such as germination, cooking, extraction, malting and fermentation. The number of publications on this topic studying the description of the mechanisms involved and recent technologies for processing enhancement has increased recently. However, due to the complexity of the hydration process, there are still many aspects that are little understood. For that reason, this review provides not only an overview of recent developments in this field, but also a critical discussion of publications from the last 2 decades, as well as suggestions for future innovative studies. This review discusses the importance of hydration in the grain industries, the pathway for water entry into the various grains, the mass transfer and fluid flow mechanisms in the process, the behavior of the hydration kinetics, the mathematical modelling, the technologies used to accelerate the process and other necessary requirements that must be performed to complement and complete our knowledge of this process.

Ultrasound assisted acidification of model foods: Kinetics and impact on structure and viscoelastic properties.

This work aimed to describe the acidification process of two specific model foods using the ultrasound technology, as well as to evaluate the changes on its viscoelasticity properties. For that, two types of model food were used, with similar composition but different structures: natural melon cylinders and restructured melon-agar cylinders. The acidification process was performed using a citric acid solution (0.2% w/w) assisted with and without ultrasound (40W/L of volumetric power and 20kHz of frequency) at constant temperature (25°C). In addition, the stress relaxation analysis was performed on the cylinders in order to evaluate the changes on the viscoelastic properties. As a result, both ultrasound processing and the different structural conformation of the model foods affected the acidification kinetics, being improved by ultrasound. Further, the acidification process with and without ultrasound affected the mechanical properties of both products, reducing their elasticity. The relaxation data could be described by a Maxwell model with two bodies and a residual spring, providing a possible explanation of the association between the mechanical model parameters and the microstructural conformation of both studied cases.

Enhancing mung bean hydration using the ultrasound technology: description of mechanisms and impact on its germination and main components.

The ultrasound technology was successfully used to improve the mass transfer processes on food. However, the study of this technology on the grain hydration and on its main components properties was still not appropriately described. This work studied the application of the ultrasound technology on the hydration process of mung beans (Vigna radiata). This grain showed sigmoidal hydration behavior with a specific water entrance pathway. The ultrasound reduced ~25% of the hydration process time. In addition, this technology caused acceleration of the seed germination - and some hypothesis for this enhancement were proposed. Moreover, it was demonstrated that the ultrasound did not change both structure and pasting properties of the bean starch. Finally, the flour rheological properties proved that the ultrasound increased its apparent viscosity, and as the starch was not modified, this alteration was attributed to the proteins. All these results are very desirable for industry since the ultrasound technology improves the hydration process without altering the starch properties, accelerates the germination process (that is important for the malting and sprouting process) and increases the flour apparent viscosity, which is desirable to produce bean-based products that need higher consistency.

Mechanisms for improving mass transfer in food with ultrasound technology: Describing the phenomena in two model cases.

The aim of this work was to demonstrate how ultrasound mechanisms (direct and indirect effects) improve the mass transfer phenomena in food processing, and which part of the process they are more effective in. Two model cases were evaluated: the hydration of sorghum grain (with two water activities) and the influx of a pigment into melon cylinders. Different treatments enabled us to evaluate and discriminate both direct (inertial flow and "sponge effect") and indirect effects (micro channel formation), alternating pre-treatments and treatments using an ultrasonic bath (20 kHz of frequency and 28 W/L of volumetric power) and a traditional water-bath. It was demonstrated that both the effects of ultrasound technology are more effective in food with higher water activity, the micro channels only forming in moist food. Moreover, micro channel formation could also be observed using agar gel cylinders, verifying the random formation of these due to cavitation. The direct effects were shown to be important in mass transfer enhancement not only in moist food, but also in dry food, this being improved by the micro channels formed and the porosity of the food. In conclusion, the improvement in mass transfer due to direct and indirect effects was firstly discriminated and described. It was proven that both phenomena are important for mass transfer in moist foods, while only the direct effects are important for dry foods. Based on these results, better processing using ultrasound technology can be obtained.

Ultrasound pre-treatment enhances the carrot drying and rehydration.

The present work aimed to describe the mechanisms involved in the enhancement of the drying and rehydration process of carrot slices caused by the pre-treatment using the ultrasound technology. For that, carrot slices of 4mm of thickness were pre-treated for 30 and 60min using an ultrasonic bath (41W/L; 25kHz). The convective drying process was performed at 40 and 60°C with 2.0m/s of air velocity, while the rehydration process was performed at 25°C. The Henderson & Pabis model was used to describe the drying kinetics and the Peleg model to describe the rehydration process of the carrots slices. As a result, the drying and rehydration kinetics were described, at the different conditions of process, correlating the results with the main effects that the ultrasound cause as a pre-treatment (cell bloating and micro-channels) and the air-drying temperature. Depending on the length of the pre-treatment, the effects caused by the ultrasound in the following processes were different. In addition, it was corroborated that when the drying temperature is increased, less evidenced is the ultrasound effect. The ultrasound, when is applied for long times, enhanced the drying and further rehydration rate at low temperatures, due to the tissue damage. Moreover, vacuum-packed samples were pre-treated with ultrasound in order to exclude the water gain and to evaluate only the micro-channels formation effect. It was concluded that the ultrasound pre-treatment enhances the drying and rehydration processes; however, future optimization studies are recommended.