Understanding appearance quality improvement of jujube slices during heat pump drying via water state and glass transition

Hou, Haonan; Chen, Qinqin; Bi, Jinfeng; Wu, Xiaoqing; Jin, Xinwen; Xiao, Li; Qiao, Yansong; Lyu, Ying

doi:10.1016/j.jfoodeng.2019.109874

Cited by 37 publications

(22 citation statements)

References 56 publications

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“…Water state was measured by a Niumag pulsed NMR analyzer (Niumag Analytical Instrument Corporation, Suzhou, China) bonded with a 0.5 T permanent magnet. The proton resonance frequency was 23.2 MHz at 32.00 ± 0.02 °C, with 90° pulses of 16 ms. Other parameters for T 2 relaxation time measurements were TW (time waiting) = 6500 m s, TE (time echo) = 0.4 m s, NECH (number of echoes) = 16 000 and NS (number of scan) = 16 16 …”

Section: Methodsmentioning

confidence: 99%

Discoloration investigations of freeze‐dried carrot cylinders from physical structure and color‐related chemical compositions

Lyu

Chen

et al. 2021

J Sci Food Agric

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BACKGROUND High carotenoid content always lead to a yellower/redder color in carrots, while a puzzling phenomenon still exists that freeze‐dried carrots (FDC) have a higher carotenoid content but a lighter color compared with thermal‐dried carrots. It seems that carotenoid is not the only main factor affecting sample color. Hence the discoloration characteristics of freeze‐dried carrots were comprehensively analyzed from physical structure and color‐related chemical composition profile. RESULTS Outcomes of low‐field nuclear magnetic resonance and scanning electron microscopy showed that sublimation of immobilized water preserved the intact porous structure of FDC, which kept the volume shrinkage below 30% and led to less accumulations of color‐related compositions. Besides, results of correlation and principal component analysis‐X model proved that lutein and caffeic acid mainly affected a* value (r = 0.917) and b* value (r = 0.836) of FDC, respectively. Moreover, lipoxygenase indirectly affected sample color by degrading carotenoids, and the lutein content loss for fresh and blanching FDC was 41.56% and 47.14%, respectively. CONCLUSIONS The discoloration of FDC was significantly affected by both physical structure and color‐related chemical compositions. © 2021 Society of Chemical Industry

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Section: Methodsmentioning

confidence: 99%

Discoloration investigations of freeze‐dried carrot cylinders from physical structure and color‐related chemical compositions

Lyu

Chen

et al. 2021

J Sci Food Agric

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“…Drying rate (DR) of processed shiitake mushroom was calculated using Eqn (2) 11,12 :

DR = \frac{M_{t 0} - M_{t 1}}{t_{0} - t_{1}}

In Eqn (2), M t 0 and M t 1 are respectively the dry basis moisture content of the material at the time t 0 and t 1 during the drying process (in g/g).…”

Section: Methodsmentioning

confidence: 99%

Role of thermal and non‐thermal drying techniques on drying kinetics and the physicochemical properties of shiitake mushroom

et al. 2021

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BACKGROUND Fresh shiitake mushrooms are rich in nutrients, but have high water content, a fast metabolism after harvest, and deteriorate extremely easily. Therefore, the drying of shiitake mushrooms has become a research direction. However, the role of different drying techniques on shiitake mushroom quality is limited. Therefore, the purpose of this study was to investigate the effect of thermal and non‐thermal drying on the drying kinetics, and the physicochemical properties of the end product. RESULTS Results showed that shiitake mushroom treated with non‐thermal drying (vacuum freeze‐drying) had an attractive color, low shrinkage, and uniform honeycomb structure, while the drying time was the longest and not conducive to the formation of shiitake mushroom aroma. But shiitake mushroom treated with thermal drying presents an attractive fragrance. In thermal processing technology, compared with hot air convection drying (HAD), infrared hot air convection drying (IRHAD) shortens the drying time by 37.5%, and had the highest oxidation resistance, polysaccharide content and the lowest color change. Relative‐humidity drying (RHD) samples had the lowest shrinkage compared with other thermal processing technology. The five polysaccharides exhibited similar preliminary structural characteristics, but the polysaccharides obtained by IRHAD have the highest antioxidant properties. CONCLUSION These results showed that compared with thermal drying technology, non‐thermal drying technology is not suitable for shiitake mushroom processing. In thermal processing technology, IRHAD is a potential drying method to obtain high‐quality dried shiitake mushrooms and shiitake mushroom polysaccharide (SMP). However, it is necessary to increase the pretreatment technology to achieve the attractive appearance of non‐thermal drying technology. © 2021 Society of Chemical Industry.

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“…the surrounding air for 15% RH became greater than that where the RH was uncontrolled, resulting in a noticeably faster moisture decrease. Hou et al (2020) found that drying jujube slices at the same temperature (60°C) and an air velocity of 2.0 m/s, the heat pump dryer spent only about 86% of the drying time required by a hotair dryer. Furthermore, after 12 hr, the drying rates of the mango sheets in both cases were slow and seemed to be similar because after drying for 12 hr, the moisture content was rather low (less than 22.2% d.b.…”

Section: Effects Of Drying Air Rh and Temperature On Drying Curvesmentioning

confidence: 99%

“…When the surface layer of the samples was dried and hard whereas the samples were in the rubbery state and still moist inside, the vapor pressure would accumulate and then move out of the samples causing tiny air pores at various sites on the mango sheets. Thus, the drying at higher temperature would lead to more likelihood for the happening of air bubbles in the mango sheet structure compared to the application of lower drying temperature Hou et al (2020). explained that during drying, the internal moisture might not transfer to the surface in time resulting in the formation of a harder surface.The tougher surface acted as a moisture transfer barrier causing the greater vapor pressure within the samples during the drying process and consequently larger pores in the samples.…”

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confidence: 99%

Moisture sorption isotherms, drying behavior, and quality attributes of mango sheets dried using hot air combined with relative humidity control

Praphunchonakorn

Jittanit

2022

Food Processing Preservation

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The equilibrium moisture contents of mango sheets were determined at 40–60°C and 11%–82% relative humidity (RH). The effects of RH and temperature of the drying air were investigated. The main objectives were: (a) to determine the moisture sorption isotherms and (b) to investigate the effects of applying hot air combined with RH control on mango sheet drying to imitate heat pump drying. Peleg's model was the best‐fitting model for the equilibrium moisture content. Controlling the RH at 15% clearly raised the drying rate after drying for 2 hr compared to drying without any RH control. Single‐stage drying at 60°C and 15% RH and two‐stage drying both required shorter drying times and provided superior mango color and textural qualities than the single‐stage drying at 60°C without any RH control. These results implicitly indicated the potential of heat pump dryer in the mango sheet drying. Novelty impact statement The moisture sorption isotherms together with the equations developed in this study are beneficial for the operation of heat pump dryer in mango sheet drying. The hot air combined with relative humidity control was applied in mango sheet drying experiments in order to imitate the drying air conditions occurring in a heat pump dryer. This study revealed that the application of heat pump dryer in the commercial drying of mango sheet or other agricultural products is interesting because this drying technique has potential to obtain the uniformity of moisture content of products without the necessity of opening the drying chamber to switch the positions of either trays or trolleys inside the drying chamber along the whole drying process which is both time‐ and labor‐consuming and increases the risk of contamination.

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Understanding appearance quality improvement of jujube slices during heat pump drying via water state and glass transition

Cited by 37 publications

References 56 publications

Discoloration investigations of freeze‐dried carrot cylinders from physical structure and color‐related chemical compositions

Discoloration investigations of freeze‐dried carrot cylinders from physical structure and color‐related chemical compositions

Role of thermal and non‐thermal drying techniques on drying kinetics and the physicochemical properties of shiitake mushroom

Moisture sorption isotherms, drying behavior, and quality attributes of mango sheets dried using hot air combined with relative humidity control

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