Intermittent Drying: Fundamentals, Modeling and Applications

Lima, Antônio Gilson Barbosa de; Delgado, J. M. P. Q.; Neto, Severino Rodrigues de Farias; Franco, Célia Maria Rufino

doi:10.1007/978-3-319-19767-8_2

Cited by 28 publications

(35 citation statements)

References 37 publications

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“…In general, intermittent drying is defined as a process that alternates active and non‐active drying periods. During non‐active period, often denominated as tempering period, heat input is stopped and the product has a relaxation period in order to allow homogenization of the moisture, which will increase the drying rate during the subsequent active drying (Barbosa de Lima, Delgado, Neto, & Franco, 2016; Jangam & Mujumdar, 2017). However, this is not the only alternative for the intermittent drying.…”

Section: Introductionmentioning

confidence: 99%

Drying of mangoes (Mangifera indica L. cv. Palmer) at changeable temperature conditions—Effects on energy consumption and quality of the dehydrated fruit

Amado

Silva

Mauro

2020

J Food Process Engineering

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This study evaluated the influence of heat input change on the drying kinetics, energy consumption, the color, and carotenoid retention during the drying of mangoes. The drying conditions in the first stage were 95°C for 40 min and 80°C for 40 min, so that the surface temperatures of the fruit at the end of this stage were around 60°C. The temperatures of the second stage and corresponding continuous drying (control) were 70 and 60°C. As a result, the thermal intermittence influenced the drying kinetics, causing significant reductions in the overall process time and providing energy savings when compared to continuous drying. The color parameters did not show relevant changes as result of the intermittent drying while good carotenoid retention was obtained in intermittent conditions, when the second stage was 60°C. Therefore, the carotenes were more sensitive to a temperature of 70°C, which highlights the importance of limiting the temperature of the mango to 60°C during the two drying stages to better preserve the quality of the dehydrated fruit. Moreover, the high air temperatures used in the first stage were advantageous for reducing the overall process time and providing energy saving.Practical ApplicationsDrying is an operation well known for the food industry. However, in so many cases, dryers are not designed with energy consumption in mind. Moreover, simple procedures can bring savings in convective drying, as shown in the present study, where the application of two‐stages in the convective drying of mangoes was advantageous to reduce the overall drying time and provide energy savings in relation to continuous drying. Besides that, good carotenoid retention was obtained using low temperature (60°C) at the second stage. The results can be useful for design of dryers and drying process, considering different temperatures. Intermittent drying of high moisture foods by varying the drying air temperature can be applied both on an industrial scale, in continuous belt dryers or in tunnel dryers, and on a small scale, using two or more dryers with different temperatures.

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Section: Introductionmentioning

confidence: 99%

Drying of mangoes (Mangifera indica L. cv. Palmer) at changeable temperature conditions—Effects on energy consumption and quality of the dehydrated fruit

Amado

Silva

Mauro

2020

J Food Process Engineering

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“…However, humidity and temperature during tempering are essential to quantify the moisture loss or uptake of the tissue to the environment, thus the moisture redistribution kinetics. In some studies, the impact of the environmental conditions during tempering was bypassed by restricting moisture removal (Barbosa de Lima, Delgado, Neto, & Franco, 2016;Nishiyama et al, 2006). Such a zero-flux condition can be enforced in laboratory experiments, by wrapping the fruit inside a plastic foil, but not on an industrial scale.…”

Section: Introductionmentioning

confidence: 99%

Towards more efficient intermittent drying of fruit: Insights from combined hygrothermal-quality modelling

Defraeye

2016

Innovative Food Science & Emerging Technologies

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Intermittent drying is a promising alternative to continuous drying, as it enables moisture redistribution during tempering periods, leading to higher effective drying rates when the process is started again. This strategy can effectively reduce the net residence time in the dryer, which can help save process energy and increase product throughput. The milder temperature conditions that occur during tempering can also be beneficial for fruit quality. Intermittent drying is analyzed, in a new way, by combining hygrothermal simulations of the drying process with a temperature-dependent kinetic model for fruit quality degradation during drying. This method enabled to quantify the total process time of the fruit, the effective residence time in the dryer but also product quality degradation. By means of a parametric study, we obtained new insights in the impact of tempering time, total cycle time for drying and the ambient humidity conditions during tempering. By intermittent drying, the residence time could be reduced successfully without compromising fruit quality. Industrial relevance. The modelling strategy provides combined information on the water activity level in the fruit and the fruit quality state during drying. This enables, in a unique way, to optimize the drying process conditions for intermittent drying in order to achieve fast drying and still obtain prime product quality. Thereby a better identification of possible savings in energy and processing time is possible for intermittent drying and their relation to the final quality of the fruits.

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“…Currently, despite the considerable potential of IMCD, the impact of IMCD on food quality has not been extensively examined ( 2 , 18 , 19 ), particularly no study has investigated the effect of IMCD on the nutritional quality attributes of kiwifruit. Kiwifruit ( Actinidia chinensis Planch ) is an attractive, valuable and nutrient-dense fruit with inviting green/yellow flesh colour, distinctive flavour, taste and many health beneficial ingredients.…”

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confidence: 99%

Nutritional quality of heat-sensitive food materials in intermittent microwave convective drying

Pham¹,

Martens²,

Karim

et al. 2018

Food & Nutrition Research

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BackgroundThe retention of health promoting components in nutrient-rich dried food is significantly affected by the dehydration method. Theoretical and experimental investigations reported in the literature have demonstrated that intermittent microwave convective drying (IMCD) can effectively improve the drying performance. However, the impact of this advanced drying method on the quality food has not been adequately investigated.DesignA programmable NN-SD691S Panasonic inverter microwave oven (1100 W, 2450 MHz) was employed for the experiments. The microwave power level was set at 100 W and ran for 20 seconds at different power ratios and the constant hot air conditions was set to a temperature of 60°C and 0.86 m/s air velocity.ObjectiveIn this study, natural bioactive compounds (ascorbic acid and total polyphenol), water activity, colour and microstructure modifications which can occur in IMCD were investigated, taking kiwifruit as a sample.Results and DiscussionThe microwave (MW) power ratio (PR) had significant impact on different quality attributes of dried samples. The results demonstrate that applying optimum level MW power and intermittency could be an appropriate strategy to significantly improve the preservation of nutrient contents, microstructure and colour of the dried sample. The IMCD at PR 1:4 was found to be the ideal drying condition with the highest ascorbic acid retention (3.944 mg/g DM), lowest colour change (ΔERGB = 43.86) and a porous microstructure. However, the total polyphenol content was better maintained (3.701 mg GAE/g DM) at higher microwave density (PR 1:3). All samples attained a desirable level of water activity which is unsusceptible for microorganism growth and reproduction.ConclusionOverall, IMCD significantly improved the drying performance and product quality compared to traditional convective drying.

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Intermittent Drying: Fundamentals, Modeling and Applications

Cited by 28 publications

References 37 publications

Drying of mangoes (Mangifera indica L. cv. Palmer) at changeable temperature conditions—Effects on energy consumption and quality of the dehydrated fruit

Drying of mangoes (Mangifera indica L. cv. Palmer) at changeable temperature conditions—Effects on energy consumption and quality of the dehydrated fruit

Towards more efficient intermittent drying of fruit: Insights from combined hygrothermal-quality modelling

Nutritional quality of heat-sensitive food materials in intermittent microwave convective drying

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