Effects of freeze-thaw pretreatments on the drying characteristics, physicochemical and phytochemical composition of red dragon fruit during mid- and near-infrared drying

Abstract

Effects of freeze-thaw pretreatments using slow (SFZ), fast (FFZ) and ultrafast (UFZ) freezing on the drying characteristics, physicochemical and phytochemical compositions of red dragon fruit slices were investigated during mid- (MIR) and near-infrared (NIR) drying. Results indicated that the pretreatments altered cellular structure, reduced drying time and increased drying rates and effective moisture diffusivity, and these effects were dependent on the freezing methods, showing that FFZ and UFZ could improve physicochemical quality, ascorbic acid, and hydroxyl scavenging ability, while SFZ could enhance total phenolics and flavonoid contents, betalains, and ABTS radical scavenging activity. Overall, freeze-thaw pretreatments prompted more efficient drying due to structural modification and improved heating uniformity, they also presented undesirable effects on color, shrinkage, betalains, phenolics and ABTS scavenging activity. The study provided a theoretical basis for applying freeze-thaw pretreatments during infrared drying and indicated the need for optimization studies for improving drying efficiency.

Keywords:

• freeze-thaw
• mid and near-infrared
• antioxidants
• PCA

Disclosure statement

The authors report no conflicts of interest. The authors alone are responsible for the content and writing of the paper.

Ethical approval

This article does not contain any studies with human participants performed by any of the authors.

Data availability statement

Data are available within the article or its supplementary materials.

Additional information

Funding

The authors are grateful to the National Natural Science Foundation of China10.13039/501100001809 (31972205) for its support. This research was also supported by the International S&T Cooperation Projects of Guangdong Province (2020A0505100007), Guangdong Basic and Applied Basic Research Foundation (2021A1515010644), the Contemporary International Collaborative Research Centre of Guangdong Province on Food Innovative Processing and Intelligent Control (2019A050519001), the Guangzhou Key Laboratory for Intelligent Sensing and Quality Control of Agricultural Products (202102100009) and the Common Technical Innovation Team of Guangdong Province on Preservation and Logistics of Agricultural Products (2021KJ145). In addition, Bassey Edidiong Joseph is in receipt of a PhD scholarship (2019ZFY014378) from the China Scholarship Council10.13039/501100004543.