Evaluation of freeze drying combined with microwave vacuum drying for functional okra snacks: Antioxidant properties, sensory quality, and energy consumption

LWT ◽  
2017 ◽  
Vol 82 ◽  
pp. 216-226 ◽  
Author(s):  
Ning Jiang ◽  
Chunquan Liu ◽  
Dajing Li ◽  
Zhongyuan Zhang ◽  
Chunju Liu ◽  
...  
2019 ◽  
Vol 2019 ◽  
pp. 1-11 ◽  
Author(s):  
Lihui Zhang ◽  
Yu Qiao ◽  
Chao Wang ◽  
Li Liao ◽  
Lu Liu ◽  
...  

In this study, freeze vacuum drying (FVD), hot air drying (AD), and FVD combined with AD (FVD-AD) were used to dry kiwifruits. Dried products were analyzed comprehensively on their sensory quality, active components, moisture mobility, odors, and microstructure. Results showed that the FVD-AD saved time by 38.22% compared with FVD while maintaining an acceptable product quality. The antioxidant properties of FVD-AD were lower than those of FVD but significantly higher than those of AD. Moreover, compared with FVD products, FVD-AD products were moderately hard (5252.71 ± 33.53 g) and improved in color, bound water, and microstructure. Additionally, FVD-AD consumed lesser drying time and energy than FD. According to cluster analysis, the odors of FVD-AD products were similar to those of the fresh ones. Principal component analysis of physicochemical and drying cost indicated that FVD-AD was a promising processing technique for functional kiwifruit snacks.


2021 ◽  
pp. 1-12
Author(s):  
T. Chaowattanakul ◽  
V.M. Khieu ◽  
C. Rojviriya ◽  
S. Siriwong ◽  
W. Jittanit ◽  
...  

This study evaluated the effects of three drying techniques, tray drying, roasting and microwave vacuum drying, on the physical properties, secondary structures, in vitro protein digestibility and X-ray tomographic structure of crickets (Acheta domesticus) and mulberry silkworm pupae (Bombyx mori L.). The protein contents of dried crickets and silkworm pupae were 49-54% and 51-53% (dry basis), respectively. Roasting produced a significantly higher browning index than the other two methods for crickets and silkworm pupae. The microwave vacuum-dried crickets exhibited the lowest hardness, with hardness values of approximately half those of the tray-dried and roasted crickets. Tray-drying and microwave vacuum drying silkworm pupae produced similar hardness values, which were lower than that of roasted silkworm pupae. The energy consumption of the tray dryer was the lowest, followed by the roaster and microwave vacuum dryer. No significant changes in the secondary protein structure of dried silkworm pupae were observed. A significant decrease in α-helix and β-turn and increase in β-sheet was observed in roasted crickets. Cricket and silkworm pupae powders produced from all drying techniques could be easily digested (90-95% digestibility). This work presents valuable knowledge for understanding the effects of different drying techniques on the properties of dried edible insects, aiming to support the production of alternative and sustainable protein sources for the growing population to improve food security.


Author(s):  
Hongfang Ji ◽  
Ailin Du ◽  
Lingwen Zhang ◽  
Shuang Li ◽  
Mingduo Yang ◽  
...  

Abstract In order to explore the potential drying process, the effects of different drying methods (sun drying, hot-air drying, microwave-vacuum drying, and freeze drying) on the antioxidant properties and phenolic contents in white button mushroom fruit bodies were investigated. The Folin-Ciocalteu method was used to determine total phenolic content, while 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging, reducing power, iron-chelating ability, and hydroxyl radical scavenging activity assays were used to elucidate antioxidant activities. Results indicated that antioxidant properties in dried white button mushroom were affected by the drying methods to different extents, and phenolic contents showed significant differences (p<0.05) among different drying methods. Microwave-vacuum drying possessed the highest antioxidant activity in DPPH radical scavenging, reducing power and iron-chelating ability, respectively; and the content of phenolic compounds was 4.945 mg gallic acid equivalents (GAE) /g dry weight (DW). Sun drying was the worst in antioxidant activity and content of phenolic compounds was 1.964 mg GAE/g DW. Additionally, significantly positive correlation was found between the total phenolic content and antioxidant activity (p<0.01). As far as antioxidant activities are concerned, microwave-vacuum drying is proposed as an appropriate drying technique for white button mushroom.


Author(s):  
Takaharu Tsuruta ◽  
Takuma Ogawa ◽  
Ryosuke Abe ◽  
Hirofumi Tanigawa

High quality drying of therapeutic protein-solution is important in medical and pharmaceutical processing.  Freeze-drying is mostly used, but it takes a long drying-time and causes damages of protein structures.  In order to improve the drying quality, we propose a microwave vacuum drying performed at ambient temperatures under low-pressure conditions.  We are focusing on the Parma-Zyme method for the evaporative drying of protein solutions such as egg white or lysozyme with vitrification. Circular dichroism (CD) spectroscopy is used to detect protein conformation changes due to the drying, and it is found that the ambient temperature drying can preserve the protein conformation. Keywords: Microwave vacuum drying; Freeze-drying; Therapeutic protein; Egg white; Lysozyme 


Molecules ◽  
2019 ◽  
Vol 24 (23) ◽  
pp. 4291 ◽  
Author(s):  
Xiaohuang Cao ◽  
Jianping Chen ◽  
Md. Nahidul Islam ◽  
Wanxiu Xu ◽  
Saiyi Zhong

To examine the processing characteristics and high quality of an improved microwave vacuum drying system, litchi fruits were dried using intermittent microwave volumetric heating while microwave vacuum drying at 2 W/g was carried out for comparison; the intermittent microwave heating profiles were set as (1) 5 min drying-on, 5 min drying-off; (2) 5 min drying-on, 10 min drying-off; and (3) 5 min drying-on, 15 min drying-off. Energy consumption during drying was determined, and physicochemical properties such as moisture content, vitamin C, total phenolics, color, and sensory evaluation of dried products were assessed. In microwave vacuum drying, intermittent microwave volumetric heating was found to be energy-efficient (about 32 KJ/g to 45 KJ/g) and saved at least 31% of energy consumption compared with microwave vacuum drying as well as decreasing product browning. In addition, microwave volumetric heating had no substantial effects on sugar and protein contents, while antioxidants were affected significantly (p ≤ 0.05). Moreover, sensory evaluation showed that intermittent microwave-assisted vacuum drying (IMVD) increased the acceptance of the dried product compared with microwave vacuum drying (MVD).


2014 ◽  
Vol 32 (15) ◽  
pp. 1840-1847 ◽  
Author(s):  
Bing Zhou ◽  
Min Zhang ◽  
Zhongxiang Fang ◽  
Yaping Liu

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