Comparison of energy consumption in the convective and freeze drying of raspberries

Kešelj, Krstan; Pavkov, Ivan; Radojčin, Milivoj; Stamenković, Zoran

doi:10.5937/jpea1704192k

Cited by 13 publications

(11 citation statements)

References 2 publications

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“…Only in the case of VD and AD, a statistically significant but slightly shorter DT was observed for GR compared to WH. Other authors also observed that FD takes much longer than other drying methods [ 33 ].…”

Section: Resultsmentioning

confidence: 99%

Dehydrated at Different Conditions and Powdered Leek as a Concentrate of Biologically Active Substances: Antioxidant Activity and Phenolic Compound Profile

et al. 2021

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This study aimed to analyze the antioxidant activity, phenolic acid profile, color changes, and chemical composition of dried and powdered leek (Allium porrum). Leek was divided into white shaft (WH) and green shaft (GR) and subjected to drying by different methods—convection drying, vacuum drying, and freeze-drying (FD)—at a temperature of 60 °C. A sample freeze-dried at a temperature of 20 °C was used as control. Analyses of the dried leek samples revealed that GR contained a higher amount of ash, protein, fat, fiber, phenolic acids, and flavonoids, and exhibited higher antioxidant capacity compared to WH. The dominant phenolic acid in WH was p-cumaric acid followed by synapic and protocatechuic acids. GR had a several-fold higher content of phenolic acids than WH, with ferulic acid being dominant (about 85% of the total phenolic content). It was also observed that a higher drying temperature resulted in the degradation of phenolic compounds and reduced the antioxidant properties of leek shafts. Most importantly, FD under a temperature of 60 °C caused a similar degree of degradation of biologically active compounds as air drying. An increase in drying temperature was associated with a slight decrease in the lightness of GR, whereas in the case of WH no significant change in this parameter was observed.

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Section: Resultsmentioning

confidence: 99%

Dehydrated at Different Conditions and Powdered Leek as a Concentrate of Biologically Active Substances: Antioxidant Activity and Phenolic Compound Profile

et al. 2021

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“…The downside of this method is that it is one of the most energy‐demanding technologies with high production costs . Kešelj and coworkers discovered that freeze‐drying of raspberry requires 1.9 times more energy than convective drying . This is one of the reasons why scientific research has been focused on combining different drying technologies in order to achieve good quality and lower production costs …”

Section: Introductionmentioning

confidence: 99%

“…19 Kešelj and coworkers discovered that freeze-drying of raspberry requires 1.9 times more energy than convective drying. 20 This is one of the reasons why scientific research has been focused on combining different drying technologies in order to achieve good quality and lower production costs. 5,21,22 Stamenkovi c and coworkers showed that the convectively dried Polana raspberry variety, which is used as addition to some confectionery products, biscuits, cookies, dairy product, etc, may be an adequate substitution for a freeze-dried raspberry with the right choice of drying factors.…”

Section: Introductionmentioning

confidence: 99%

Ranking and multicriteria decision making in optimization of raspberry convective drying processes

Stamenković

Radojčin

Pavkov

et al. 2020

Journal of Chemometrics

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Serbia is one of the leading producers and exporters of raspberry in the world, and considering the short shelf life of raspberry, the processing, storage, and transport are some of the main issues to be addressed. A comparative experiment was conducted in order to find the suitable process parameters for convective drying that may be considered as the alternatives to freeze‐drying, which is a widely used preservation method for raspberry even though it is a costly and energy‐consuming method. Twelve convective drying regimens were applied with a combination of three influencing factors: air temperature (60°C, 70°C, and 80°C), air rate (0.5 and 1.5 m·s−1), and stage of raspberry (fresh and frozen). The final product, a dried raspberry, was assessed for chemical, physical, and mechanical properties and rehydration capacity. Deep ranking analysis by power eigenvectors (DRAPE) and sum of ranking differences (SRD) were used to uncover the differences and similarities between the applied drying methods. SRD showed that convective drying of fresh raspberries proved to be more similar to freeze‐dried raspberries than convective drying of frozen ones. Fresh samples dried at 60 °C air temperature and 1.5 m·s−1 air flow proved to be the most similar to the reference freeze‐drying method. This convective regimen gives samples with the lowest color change, shrinkage, and shape deformation. With the mechanical and chemical properties of these samples being observed, statistical Duncan's test show that there is no significant difference (P < .05) in terms of hardness, shear force resistance, total phenolic, and total flavonoid preservation, compared with freeze‐dried samples. DRAPE gave similar results, but it added the variable importance in ranking as well, and total phenol reduction was defined as the most important variable. These results can help practitioners to develop cheaper and simpler drying methods that would replace the freeze‐drying but keep the same quality of the dried products.

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“…9 However, the equipment of freeze drying comes with a high maintenance cost 10 and the energy consumption is approximately twice than the convective drying. 11 Vacuum drying is also reported to have positive effects on quality compared with the hot air convective drying, but the energy consumption is increased at a similar scale. 12 As for the fluidized bed drying (FBDs), it is reported that quality loss of medicinal plant drying was limited, compared with hot air and solar drying.…”

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confidence: 99%

“…17,18 Due to the high drying efficiency, FBD is well-suited for large scale operations. 19,20 It is also an economical method compared to vacuum, 12,21 hybrid, 3,8,21 freeze 10,11,21 and convective drying. 14,21 Generally, FBDs are more convenient and attractive in industry, even for farmers, to produce high-quality products.…”

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confidence: 99%

Energetic, economic, and global warming aspects of fluidized bed drying of the medicinal plant Echium Amoenum Fisch. & C. A. Mey

Nadi

2021

Env Prog and Sustain Energy

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This research aims to conduct a comprehensive analysis of the drying conditions in a pilot-scale fluidized bed dryer by considering energetic, economic and global warming aspects. Echium amoenum Fisch. & C. A. Mey. E. amoenum petals were dried at a temperature range of 40-60 C and air velocities of 0.5 to 1 m s À1 . According to the results, the air velocity has a positive effect but the drying temperature has a negative impact on the specific energy consumption (SEC), the production cost and the GHG emissions. It was observed that the case of 0.5 m s À1 air velocity and 60 C drying temperature, the production cost, the SEC and the GHG emissions were minimized. However, considering the quality of the dried E. amoenum petals the optimal conditions were obtained at 60 C drying temperature and 0.91 m s À1 air velocity.Under these conditions, GHG emissions, production cost and SEC of dried E. amoenum petals would be 60.56 g CO 2 kg À1 , $38.87 kg À1 of dried E. amoenum petals and 29.87 MJ kg À1 of evaporated water, respectively.

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Comparison of energy consumption in the convective and freeze drying of raspberries

Abstract: Freeze-drying has proven to be one of the best drying processes thus far.

Cited by 13 publications

References 2 publications

Dehydrated at Different Conditions and Powdered Leek as a Concentrate of Biologically Active Substances: Antioxidant Activity and Phenolic Compound Profile

Dehydrated at Different Conditions and Powdered Leek as a Concentrate of Biologically Active Substances: Antioxidant Activity and Phenolic Compound Profile

Ranking and multicriteria decision making in optimization of raspberry convective drying processes

Energetic, economic, and global warming aspects of fluidized bed drying of the medicinal plant Echium Amoenum Fisch. & C. A. Mey

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