Food Technology Magazine
, pages 83-91
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In this study, whipped raspberry puree was dried in the microwavefreeze drying(MWFD). Through the combined use of microwaves and a foam structure, the drying process should be accelerated and at the same time an innovative product structure with an intensive aroma effect for consumption as a luxury food should be createdSnack. The influence of potato protein asfoamyAgent, maltodextrin as a foam stabilizer and the influence of microwave (MW) on the drying properties of raspberry foam under MWFD were studied. Conventional freeze drying (FD) tests were performed for reference. It has been shown that the MD concentration has a significant influence on the product temperature. Because higher MD concentrations produced smaller bubbles and a more even bubble size distribution, lower drying temperatures were required to achieve the same final moisture content.
Different MW powers had no significant influence on the drying time. MWFD at 1.0 Wg−1resulted in a three to fourfold reduction in overall drying time compared to FD. The addition of 10% protein resulted in the gentlest drying at high MW power, as structural changes allowed less resistance to water vapor mass transfer. There was a high correlation between the foam properties and the drying behavior. An overflow of over 450% resulted in gentle drying at all tested microwave power levels. Foam bubble size and bubble size distribution correlated well with drying rate. Overall, MWFD has proven to be a significantly faster and gentler alternative to FD for fruit foam production.
Raspberries are popular with consumers because they contain high levels of ascorbic acid and anthocyanins. Along with the increasing demand for ready meals, there has been a clear trend towards the production of healthy snack products in recent years. In general, a modern snack product is expected to offer high quality nutrition combined with an attractive appearance and mouthfeel. With increasing health awareness, vegan foods are growing in popularity, which has led to an increasing demand for fruit-based products. In addition, the consumer generally expects a minimally processed product with a natural and intense flavor that is close to that of unprocessed food. One way to produce dried snack products is by freeze drying (FD), a method that is considered safe and produces products with a near-natural appearance. However, FD is slow and therefore expensive, and products (e.g. dried whole fruit like raspberries) are slow to rehydrate. As an alternative to dried whole fruit, an attractive fruit product concept could be achieved by first processing whole fruit into pulp or puree and then whipping it into foam. Such foamed pulps could then be dried. This made it possible to produce a snack product with a highly porous structure that, when chewed, shows a new and intense sensation as the aroma is released immediately (Carvalho et al., 2017).
The foamed structure could also lead to a faster drying process as the open structure offers less resistance to the escape of water vapor during drying (Huang et al., 2015). Liquid or semi-liquid foods are whipped into a mechanically and thermodynamically stable foam using foaming agents and foam stabilizers such as hydrocolloids. In particular when a foam structure is to be dried, a certain foam stability is important; An unstable foam can collapse before or during the drying process. In order to obtain a stable fruit foam, various foaming and stabilizing agents such as egg white, soy protein isolate, methylcellulose or milk proteins have been described in the literature (Abbasi and Azizpour, 2016, Franco and Perussello, 2015, Kadam et al. al., 2011, Karim and Wai, 1999, Rajkumar et al., 2007, Sankat and Castaigne, 2004, Thuwapanichayanan et al., 2008). Recently, food manufacturers have shown great interest in replacing animal proteins with plant proteins (Glusac et al., 2018). Among the plant proteins, high quality hypoallergenic potato proteins have gained interest. Because of its functional properties as a potato protease inhibitor, a major portion of the soluble potato protein was used as a foaming agent. Especially in low pH ranges, PPI is stable against Ostwald ripening at pH 3, the pH of raspberries (Van Koningsveld et al., 2002). Carbohydrates such as maltodextrin can be used to improve foam stabilization due to their neutral taste and high solubility (Jafari et al., 2017). Hydrocolloids, which are mainly used as gelling agents when dispersed in water (Saha and Bhattacharya, 2010), are also used. Typically, a gelling agent such as pectin can help stabilize a foam and prevent dewatering, coalescence, breakage of the film between bubbles, Ostwald ripening, and other destabilizing events.
Foam drying, also known as foam mat drying, has been studied since the 1920s. It has become popular because liquid or semi-liquid products can be dried faster this way than with traditional methods (Ratti and Kudra, 2006). Greater efficiency is achieved because the air bubbles increase internal surface area and create a structure that is less resistant to mass transport of water vapor, resulting in evaporated water being removed much faster than a non-foamed liquid structure. On this basis, Brygidyr et al. (1977) and Thuwapanichayanan et al. (2012) reported that foam drying could be achieved at lower temperatures; and foam hardly experiences overheating, which can achieve higher product quality (Ng and Sulaiman, 2018). It has also been found that foaming agents and stabilizing agents can help prevent bubble collapse during drying as they increase the glass transition temperature of the sample (Ratti and Kudra, 2006).
It seems that drying fruit with foam mats is one of the most effective ways to dry sticky and very dense fruit purees. It has been applied to various fruits and fruit products such as mango (Lobo et al., 2017), jambolan (Carvalho et al., 2017), cowpea (Falade et al., 2003) and cantaloupe (Sangamithra et al., 2015a). However, until now foam mat drying of raspberries has not been reported in the literature.
As mentioned above and proven by a number of researchers (Jiang et al., 2011, Michalska et al., 2016, Monteiro et al., 2015), freeze drying has always been the best method to obtain high quality dried food from the drying process is performed at very low temperatures in an oxygen-free environment. However, the lower drying rates observed in freeze drying result in high energy consumption and hence lower energy efficiency (Ratti, 2001, Zhang et al., 2006). Dehnad et al. (2016) emphasized that what is best for functional properties is a trade-off between drying time and temperature. Therefore, there is a pronounced need for an equally gentle drying process that can deliver fruit products of comparable quality but higher process efficiency. Microwave-assisted freeze-drying (MWFD) appears to be a promising method. Because microwave electromagnetic radiation volumetrically heats the product in large quantities without direct contact, the application of microwave energy (MW) to a freeze-drying process results in faster drying rates and therefore shorter overall processing times. However, there are still some difficulties in implementing MWFD on an industrial scale due to the non-uniform temperature distribution. It is important to regulate microwave power and chamber pressure to avoid hotspots during the process (Fan et al., 2018).
To the best of the authors' knowledge, no work on the foaming properties of raspberry puree and its behavior during microwave drying has been published in the literature. The hypothesis of this work was that the freeze drying of foamed fruit puree can be accelerated by microwave energy, resulting in a high quality product and a specific end product structure.
The main purpose of this study was to investigate the drying properties of raspberry foam. We evaluated the influence of potato protease inhibitors (PPI) as a foaming agent, the concentration of MD as a foam stabilizer, and the influence of MW input on drying behavior to determine the optimal MWFD conditions for fruit foam. As a reference, the MWFD method was compared with conventional FD.
FrozenWillametteRaspberry variety from Serbia was provided by Main Frucht (Gochsheim, Germany). The required amount of frozen raspberries was thawed in a 2-hat appliance at 20°C. A puree was then made using a food grinder. PPI was used as the foaming agent. Maltodextrin (DE 6) (MD) and pectin (P) were used as foam stabilizers. Table 1 and Table 2 show the foam formulations, all of which have proven to be suitable for a stable drying process in preliminary tests. Whisk the raspberry puree mixture until fluffy
results and discussion
In this section, we report the MWFD drying behavior of raspberry fruit foams containing different concentrations of active ingredients affecting foam formation and foam stabilization. In section 3.3 we compare the MWFD drying rate with that of conventional FD.
Our results show that moderate foam overflow is beneficial for efficient drying and is a compromise between large internal surface area and thin lamellae. The diffusion limitation, which typically occurs with very dense structures, especially towards the end of drying, can be circumvented in this way. From this point of view, it is important to find a favorable concentration of the foaming agent in order to achieve an open, porous, yet stable foam for the highest possible drying speed. The
This research project was supported byThe Federal Ministry of Economics and Technology(via AiF) and FEI (Research Association of the Food Industry e.V., Bonn, project AiF 19015N). We thank Püschner Microwaves (Schwanewede, Germany) for technical support and Main Frucht (Gochsheim, Germany) for the supply of raspberries.
- E.Abbasiet al.
Evaluation of the physicochemical properties of foam mat dried tart cherry powder
LWT - Food Science. technical (Food Science – Technology.)
- IS.Bridgetet al.
Characterization and drying of tomato paste foam by hot air and microwave energy
can Inst. Food Science. Technology. J
- D.Dehnadet al.
Influence of drying on functional properties of food biopolymers: from traditional to new dehydration techniques
Food science trends. Technology.
- T.S.Francoet al.
Yacon juice foam mat drying: experimental analysis and computer simulation
J. Food Eng.
- J.A musicianet al.
Gel-like emulsions stabilized by tyrosinase-crosslinked potato and zein proteins
- S.M.Jafariet al.
Influence of spray drying on water solubility index, apparent density and anthocyanin content of pomegranate juice powder
- IN.Karimet al.
Foam mat drying of star fruit puree (Averrhoa carambola L.). Stability and air drying properties
- FA.Loboet al.
Foam mat drying of Tommy Atkins mangoes: Effects of air temperature and concentrations of soy lecithin and carboxymethylcellulose on phenolic composition, mangiferin, and antioxidant capacity
- IN.Michalskaet al.
Physico-chemical properties of whole fruit yolk powder obtained using various drying technologies
- R.L.Monteiroet al.
How to build a microwave vacuum dryer with turntable
J. Food Eng.
Development of beetroot powder (Beta vulgaris) using foam mat drying
LWT - Food Science. technical (Food Science – Technology.)
16 microwave equipment and process control requirements for advanced applications
Modeling of moisture diffusion in pores of a banana foam mat using a 2-D stochastic pore network: Determination of the moisture diffusion coefficient during the adsorption process
J. Food Eng.
Drying properties of foamed alphonso mango pulp in a continuous foam mat dryer
J. Food Eng.
Convection and freeze drying of high quality food: a review
J. Food Eng.
Foaming and drying behavior of ripe bananas
LWT - Food Science. technical (Food Science – Technology.)
Irreversible thermochromic ink for identifying over and under processed product segments in microwave assisted freeze drying
2023, Journal of Food Technology
The formation of over- and under-processed product areas is an inherent disadvantage of microwave-assisted freeze-drying (MWFD) of food, which is attributed to the inhomogeneity of microwave energy distribution. To overcome limitations in studying inhomogeneity effects, the purpose of this study was to develop and validate a new method using an irreversible thermochromic color component (ITC) with a specific color intensity profile as a function of temperature (40–70 °C). ). For validation, thermal images and spatially resolved biomarker inactivation were compared to the color intensity pattern resulting from the temperature-induced color response of ITC in MWFD. The ITC method offers advantages over existing methods as it visualizes the spatial distribution of the maximum treatment temperature independent of post-treatment effects and existing dryer designs. This user-friendly method has the potential to eliminate or reduce distortions due to the little-known inhomogeneity of microwave applications and pave the way for energy-efficient and fast MWFD of food.
Influence of pulsed microwaves on betacyanins, betaxanthins and physical properties in beet drying
2023, Applied Food Research
The aim of this study was to investigate the influence of pulse ratio and microwave power when drying beetroot using a combined intermittent microwave and hot air at low temperature (40 °C). By increasing the microwave power from 360 to 900 W and reducing the pulse ratio from 6 to 2, a significant reduction in drying time was observed. The highest Deffwas obtained at a microwave power of 900 W and a pulse ratio of 6. Dried beets showed the lowest shrinkage and the highest rehydration at a microwave power of 900 W and a pulse ratio of 6. In addition, increasing the microwave power and pulse ratio decreased the apparent density of the dried samples. By increasing the microwave power and the pulse ratio, the specific energy consumption could be reduced. Increasing the microwave power and pulse ratio increased the levels of betacyanins and betaxanthins to 79.47 and 44.20%, respectively. In addition, the samples dried at a power of 900 W and a pulse ratio of 6 showed the least microstructural collapse. Overall, the results of this study showed that by considering an appropriate pulse ratio and the applied power, good quality industrially dried products can be produced.
Production of blueberry pulp powder by microwave-assisted foam mat drying: Effects of foam agent formulations on drying properties and physicochemical properties
Foaming agents affect the feasibility of microwave assisted foam mat drying (MFD) for blueberry pulp powder (BPP) production. In this study, the effects of foaming agents on the drying properties of foamed blueberry pulp (FBP) and the physico-chemical indicators of BPP were investigated using formulations containing protein powder (EWP, 0, 4, 8 g/100 g), maltodextrin (MD, 0, 5, 10 g/100 g) and carboxymethyl cellulose (CMC, 0, 0.5, 1 g/100 g). The results showed that the simultaneous addition of EWP and MD obviously affected the drying rate of FBP. The solubility and porosity of BPP increased significantly (P<0.05) with increasing concentrations of EWP, MD and CMC. The physicochemical indicators of BPP were evaluated using the principal component analysis method due to the significant differences in color, tanning index (BI) and total anthocyanin content (TAC) of BPP among different foam concentrate formulations. The optimal formulation consisting of EWP, MD and CMC in the ratio 16:20:1 can achieve a high drying speed and the desired physico-chemical quality with high solubility and porosity as well as relatively high TAC and BI. This study can provide guidance for the production of powders of high physico-chemical quality with high moisture content, heat sensitivity and high viscosity, such as blueberry pulp.
Development of a control system for microwave freeze drying of carrot slices using dynamic microwave logic control
2021, Journal of Food Technology
The aim of this research was to develop a closed-loop control system (CLC) to improve the microwave freeze drying (MFD) process and to study the effects of a dynamic microwave logic control (DMLC) on the drying characteristics of the MFD. The development process consisted of two parts: (1) the MFD experiment to develop the DMLC and (2) the implementation of the CLC with the DMLC on top of the MFD process. In the first part, the MFD process was studied to determine the strategy for drying the carrot slices using microwave powers of 100 W, 200 W and 300 W, with a temperature profile of the sample from -15 °C to 40 °C and the final moisture grade of 6% (wet basis). In the second part, the DMLC was strategically developed and integrated into the CLC system. The results showed that in the MFD process, the DMLC was developed based on a drying phase configuration and dynamic control between microwave power and real-time moisture content sensing to provide feedback to the CLC system. After applying DMLC in the CLC system, the efficiency of the MFD process could be improved by up to 62.4% by reducing the drying time compared to the freeze drying (FD) process. MFD-DMLC also resulted in carrot quality similar to a traditional FD process. Since DMLC showed great potential for improving the MFD process, it could be further developed into a powerful MFD process in terms of product quality and process efficiency for future industrial use.
Influence of gum arabic concentrations on foam properties, drying kinetics and physico-chemical properties of foam mat drying of melons
2021, Food Hydrocolloids
The effect of gum arabic (GA) concentrations (0, 5, 10, and 15%) on foam properties, drying kinetics, and effective moisture diffusion when drying melon foam mats (cucumber melon) was analysed. The results showed that foam mat drying of melon puree with 10% GA resulted in better foam density, foam expansion and foam stability. The Page model fits the foam mat drying behavior of cantaloupe foam with different concentrations of GA at a constant temperature of 55°C. The moisture content of melon powder dried with foam mats ranged from 3.29 to 4.64%. The flowability of the powder was significantly affected by the GA concentration. The powder produced at higher GA concentration showed good powder flowability and lower cohesion. Fresh cantaloupe fruit can be preserved in foam mat dried cantaloupe powder and used as a food ingredient in a variety of foods. The application of foam mat dried cantaloupe powder in the cake frosting yielded a natural coloring with antioxidants and no significant changes in the frosting viscosity flow index.
Surface and foam properties of potato proteins: Influence of protein concentration, pH and ionic strength
2020, Food Hydrocolloids
Using a multi-scale approach, potato protein isolate was holistically characterized in terms of its solubility and surface charge, surface activity and surface dilatation properties, as well as foam and bubble structure properties. The aim was to gain a better mechanistic understanding of the functionality of potato proteins by using different protein concentrations (0.1–10.0%), pH values (3.0–10.0) and NaCl concentrations (0–200 mM). . Overall, it was found that surface activity was largely unaffected by changing protein concentration and pH, whereas pH had a marked effect on surface stretching elasticity. Likewise, foam stability was affected by pH and gave a maximum around the isoelectric point, which is attributed to improved network formation at the air/water interface, resulting in increased surface film stability. Coarsening exponents were found to reflect foam stability results. In comparison, the presence of NaCl clearly had an enhancing effect on surface activity and resulted in increased protein-protein interactions in the surface film. In turn, more compact surface films led to better foamability and foam stability as well as lower coarsening exponents. The comparison of the results with mechanisms known for β-lactoglobulin-stabilized surfaces showed that they are in principle also applicable to the functional properties of potato proteins. Overall, foam structures based on potato proteins can be controlled more specifically with the knowledge gained.
Regression analysis to predict fermentation state of packaged kimchi using a colorimetric indicator
Journal of Food Engineering, Band 240, 2019, s. 65-72
The use of a colorimetric indicator to monitor the degree of fermentation in kimchi was investigated. Changes in total color difference (TCD) occurred continuously from the first to the last stage of fermentation, with a maximum TCD value of 36.08 ± 0.72 at 28 days. The experimental data for the transformed color response function,F(Xc)They have been shown to be more linear (R2=0.986) than for TCD values. The coefficients for determining the pH value:F(Xc)(R2=0.9583) and titratable acidity:F(Xc)(R2= 0.9828) were sufficient to satisfy the zero-order answer. The results of the standardized residuals proved their normal distribution, indicating that 95% of the residuals of the predicted pH or titratable acidity were in the range of -1.96 to 1.96. The coefficients of determination between predicted and observed data were 0.841 (pH) and 0.912 (titratable acidity). Thus, based on a regression analysis, the colorimetric indicator could be used as an indicator of kimchi fermentation.
BRS Violeta (BRS Rúbea×IAC 1398-21) Grape Juice Powder made by Foam Mat Drying. Part I: Influence of drying temperature on phenolic compounds and antioxidant activity
Food Chemistry, Volume 298, 2019, Item 124971
The BRS Violeta grape has flesh and skin with a high content of phenolic compounds (PCs) and an intense purple color. It was used as a raw material for the production of juice and dehydrated products using foam mat drying at 60, 70 and 80 °C and freeze drying (control). HLPC-DAD-ESI-MSNmade it possible to assess the quantitative and qualitative changes in the main PCs (anthocyanins, flavonols and hydroxycinnamic acid derivatives (HCAD)) present in the grapes during processing. The use of the steam extraction method to obtain grape juice allowed greater extraction of flavonols and especially derivatives of hydroxycinnamic acid compared to anthocyanins. Drying at 70°C was best for preserving the PCs while reducing processing time. The powdered products showed significant levels of total PC (3-5 mg/g) and antioxidant activity (32-79 (DPPH) or 17-27 (FRAP) mg/g).
Storage stability of the phenolic compounds, color and antioxidant activity of jambolan juice powder obtained by drying foam mats
Food Research International, Band 128, 2020, Artikel 108750
Jambolan (Syzigium cumini(L.) Skeels) stands out among Brazilian fruits that are rich in bioactive compounds and have the potential to create dehydrated products. Therefore, Jambolan juice powder was produced by the foam mat drying method and stored at three temperatures (4, 25, 35 °C) for 150 days. The influence of time, temperature and the interaction of these two factors on the qualitative and quantitative profile of phenolic compounds was determined after analysis of the powders using HPLC-DAD-ESI-MSN. In the powders exposed to the different test conditions, the flavonol concentration did not differ from the control sample and only a small reduction in anthocyanin concentrations (7-9%) was observed, which was only significantly affected by the storage time. Furthermore, the molar profiles of these compounds were more affected by time than storage temperature, but none of the identified compounds were completely degraded. However, the percentage of antioxidant activity varied during storage, with no major loss seen after 150 days at all storage temperatures. The results showed that Jambolan juice powder is very stable in terms of anthocyanin and flavonol concentrations at all three storage temperatures. This and the attractive color (purple-red) make it a potential ingredient for enriching differentiated foods.
Heat and mass transfer modeling during foam mat drying of lime juice under the influence of different concentrations of ovalbumin
Journal of Food Engineering, Band 238, 2018, s. 164-177
In this study, the effect of ovalbumin concentration as a foaming agent (2, 3 and 4%) on foam mat drying of lime juice at 60 °C with 5 mm thick foam was investigated. The process was also simulated to study the effect of ovalbumin concentration on temperature and humidity distribution. The model was validated by comparing the data obtained from the model with experimental data. Increasing the ovalbumin concentration resulted in a decrease in the powder's bulk and tapped densities and an 11.22% increase in its water absorption index. Changes in bulk and tapped densities were 0.336-0.4 and 0.511-0.598 g/cm3Area. Changes in hue angle color parameters also resulted in statistically significant differences in the 2 and 4% ovalbumin concentrations, while there was no significant difference in the 2-3% and 3-4% concentrations. The results showed a good correlation coefficient of over 0.90 between the experimental data and the data obtained from the model. The even temperature and moisture distributions during the foam mat drying improved the qualitative properties of the final product in terms of the moisture content uniformity of the resulting powder, ultimately resulting in a higher quality lime juice powder.
Influence of excipients on the flowability and microstructural properties of foam freeze-dried date powder
Journal of Food Engineering, Band 215, 2017, s. 33-43
Date powder was prepared without (control) and with carriers at three ripening stages of dates (Khalal, Rutab and Tamr) by the foam mat freeze drying method. Maltodextrin (MD) DE 10 and gum arabic (GA) in two concentration levels (40% and 50%) were used as carriers. The influence of carriers on the flowability and the microstructural properties of the date powder was investigated. Maturity stage, carrier type and their concentration levels had a significant impact on almost all flow parameters. Control powder particles had more clumps resulting in no flowability. Date powder made with GA had a lower moisture content (7.1–9.7%), a lower angle of repose (32–37°), and a lower bulk density (0.6–0.7 g/cm).3), tap density (0.8–0.9 g/cm).3), particle density (1.5-1.6 g/cm3), Carr index (20–24%) and Hausner ratio (1.3), and relatively smaller particles (47 ± 20 μm) compared to powders made with MD. Microstructural analysis of the powder particles revealed that carriers are essential to obtain free-flowing powders. Overall, date powders made with GA had relatively good flowability and lower cohesion. Accordingly, 50% carrier-added powder had relatively better flowability.
Effects of foam mat drying on the physicochemical and microstructural properties of yacon juice powder
LWT – Food Science and Technology, Vol. 66, 2016, pp. 503-513
Yacon juice powder can be used as a highly nutritious ingredient in various food preparations. To this end, factors such as moisture content, density, porosity and solubility should be optimized as they determine the ease of reconstitution, stability and sensory quality of the product. In this work, yacon juice of two different concentrations (8°Brix and 24°Brix), both with added egg albumin as a foaming agent, was subjected to foam mat drying at different temperatures (50°C, 60°C and 70°C) and Foam layer thicknesses (0.5 cm, 1.0 cm and 1.5 cm). The resulting juice powders were evaluated for color, moisture, chemical composition, water activity, water solubility, water absorption rate, absolute and bulk density, intragranular porosity, microstructure, and hygroscopicity. The drying conditions did not affect the solubility index, density, microstructure, and porosity of the particles, but the temperature increase reduced moisture content, water activity, and hence hygroscopicity. The concentrated juice powders were lighter and redder than the unconcentrated juices, which tended to turn green. The highest air temperature in combination with reduced thickness turned out to be the best drying condition for both juices, yielding juice powders with low water activity and satisfactory physicochemical properties.
© 2018 Published by Elsevier Ltd.