Recent developments in high efficient freeze-drying of fruits and vegetables assisted by microwave: A review

ABSTRACT

Microwave heating has been applied in the drying of high-value solids as it affords a number of advantages, including shorter drying time and better product quality. Freeze-drying at cryogenic temperature and extremely low pressure provides the advantage of high product quality, but at very high capital and operating costs due partly to very long drying time. Freeze-drying coupled with a microwave heat source speeds up the drying rate and yields good quality products provided the operating unit is designed and operated to achieve the potential for an absence of hot spot developments. This review is a survey of recent developments in the modeling and experimental results on microwave-assisted freeze-drying (MFD) over the past decade. Owing to the high costs involved, so far all applications are limited to small-scale operations for the drying of high-value foods such as fruits and vegetables. In order to promote industrial-scale applications for a broader range of products further research and development efforts are needed to offset the current limitations of the process. The needs and opportunities for future research and developments are outlined.

KEYWORDS:

• Microwave
• Vacuum freeze-drying
• Drying rate
• Quality
• Fruits and vegetables

Acknowledgments

We acknowledge the financial support from National Key R&D Program of China (Contract No. 2017YFD0400901), Jiangsu Province (China) Agricultural Innovation Project(Contract No. CX(17)2017), Jiangsu Province(China) “Collaborative Innovation Center for Food Safety and Quality Control”Industry Development Program, Jiangsu Province (China) Infrastructure Project (Contract No. BM2014051) all of which enabled us to carry out this study.

Funding

National Key R&D Program 510 of China (Contract No. 2017YFD0400901), Jiangsu Province (China) Agricultural Innovation Project (Contract No. CX (17) 2017), Jiangsu Province (China) “Collaborative Innovation Center for Food Safety and Quality Control” Industry Development Program, Jiangsu Province (China) Infrastructure Project (Contract No. BM2014051).