Food Technology Magazine
Bind 240,
January 2019
, pages 83-91
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Abstract
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.
introduction
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.
section excerpt
foam preparation
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.
Conclusions
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
recognitions
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.
references(33)
- E.Abbasiet al.
Evaluation of the physicochemical properties of foam mat dried tart cherry powder
LWT - Food Science. technical (Food Science – Technology.)
(2016)
- IS.Bridgetet al.
Characterization and drying of tomato paste foam by hot air and microwave energy
can Inst. Food Science. Technology. J
(1977)
- D.Dehnadet al.
Influence of drying on functional properties of food biopolymers: from traditional to new dehydration techniques
Food science trends. Technology.
(2016)
- T.S.Francoet al.
Yacon juice foam mat drying: experimental analysis and computer simulation
J. Food Eng.
(2015)
- J.A musicianet al.
Gel-like emulsions stabilized by tyrosinase-crosslinked potato and zein proteins
food hydrocolloids
(September 2018)
- S.M.Jafariet al.
Influence of spray drying on water solubility index, apparent density and anthocyanin content of pomegranate juice powder
powder technology.
(2017)
- IN.Karimet al.
Foam mat drying of star fruit puree (Averrhoa carambola L.). Stability and air drying properties
food chem.
(1999)
- 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
food chem.
(2017)
- IN.Michalskaet al.
Physico-chemical properties of whole fruit yolk powder obtained using various drying technologies
food chem.
(2016)
- R.L.Monteiroet al.
How to build a microwave vacuum dryer with turntable
J. Food Eng.
(2015)
Development of beetroot powder (Beta vulgaris) using foam mat drying
LWT - Food Science. technical (Food Science – Technology.)
(2018)
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.
(2010)
Drying properties of foamed alphonso mango pulp in a continuous foam mat dryer
J. Food Eng.
(2007)
Convection and freeze drying of high quality food: a review
J. Food Eng.
(2001)
Foaming and drying behavior of ripe bananas
LWT - Food Science. technical (Food Science – Technology.)
(2004)
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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
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Surface and foam properties of potato proteins: Influence of protein concentration, pH and ionic strength
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Heat and mass transfer modeling during foam mat drying of lime juice under the influence of different concentrations of ovalbumin
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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.
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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.
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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.
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