J Food Process Preserv. 2019;00:e14319. wileyonlinelibrary.com/journal/jfpp | 1 of 11 https://doi.org/10.1111/jfpp.14319 © 2019 Wiley Periodicals, Inc. 1 | INTRODUCTION Fruits and vegetables are perishable foods with high moisture. Drying is a classical technique of fruit and vegetable preservation that can diminish the microbiological activity, reduce the water ac- tivity of the material, and prevent deterioration (Liu et al., 2017). In recent years, combination drying (in which two or more drying techniques are used together) has been proved to be an efficient technique for the reduction of drying cost and energy expenditure, as well as quality improvement. Hot air drying, considered as the simplest and most economical drying method, has frequently been carried out as a predrying method in combination drying (Ando et al., 2016b). During hot air predrying, complicated modifications of phys- ical properties and microstructure will occur in the fruit and vege- table tissues, influencing the overall texture of the dried products (Mohammad, Richard, Chandan, & Karim, 2015). During hot air dry- ing, the transport of cellular water from the tissue to the surrounding causes cell shrinkage or deformation, and changes in the stiffness of the cell wall (Ando et al., 2016a; Lewicki & Drzewucka-Bujak, 1998). The mechanical characteristics of parenchyma tissue in fruits and vegetables are known to be important factors for obtaining a good texture in the dehydrated product (Oikonomopoulou & Krokida, 2012). The elastic modulus of fruits and vegetables is an important biomechanical index which reflects their mechanical Received: 1 July 2019 | Revised: 14 September 2019 | Accepted: 26 October 2019 DOI: 10.1111/jfpp.14319 ORIGINAL ARTICLE Correlation of mechanical properties of peach slices with cell wall polysaccharides and cell morphology during hot air predrying Haiou Wang 1 | Chunju Liu 2 | Youlin Xue 3 | Dajing Li 2 1 School of Food Science, Nanjing Xiaozhuang University, Nanjing, P.R. China 2 Institute of Agro-product Processing, Jiangsu Academy of Agricultural Sciences, Nanjing, P.R. China 3 College of Light Industry, Liaoning University, Shenyang, P.R. China Correspondence Dajing Li, Institute of Agro-product Processing, Jiangsu Academy of Agricultural Sciences, No.50 Zhongling Road, Xuanwu District, Nanjing, Jiangsu Province 210014, P.R. China. Email: 124896780@qq.com Funding information The National Natural Science Foundations of China, Grant/Award Number: 31872901; the National Key R&D Program of China, Grant/ Award Number: 2017YFD0400900; the Special Fund for Agro-scientific Research in the Public Interest, Ministry of Agriculture, Grant/Award Number: 201503142 Abstract The mechanical properties, cell wall polysaccharides, cell morphology, and cell wall ultrastructure of peach slices during hot air predrying were investigated. A continu- ous decrease was observed with respect to the elastic modulus and maximum stress, and total pectin, hemicellulose, and cellulose contents of the cell wall in the peach samples with an increase in the drying time. However, an increasing trend was seen in the viscosity index and fractal dimension of the cell cross-sectional area. The elastic modulus and maximum stress were positively correlated and grouped with the cel- lulose content and total pectin content. The viscosity index was close to the fractal dimension of the cell cross-sectional area and was negatively correlated with the con- tent of cell wall polysaccharides. In this study, the correlations of mechanical proper- ties with cell wall polysaccharides and cell morphology during hot air predrying were constructed for guiding the textural quality improvement of hot air dried products. Practical applications Hot air drying is often used in the dehydrated products of fruits and vegetables. In this study, peach fruit was selected to study the mechanical properties of peach slices during the hot air predrying process by observing the cell wall polysaccharides, the morphology, and microstructure of cells. Their changing trend and correlations were revealed. The results of this study can be useful for the process optimization and textural quality improvement of hot air dried fruits and vegetables.