Specific heat of apple at different moisture contents and temperatures

TL;DR

This study experimentally investigates the specific heat of apples across various moisture levels and temperatures, highlighting the influence of bound water and proposing models to describe the heat capacity behavior.

Contribution

It introduces an additive model for specific heat based on apple as a water-apple mixture and provides an analytical equation for $C(W,T)$ dependencies.

Findings

Bound water significantly affects specific heat behavior.

Estimated bound water amounts align with monolayer moisture content.

Proposed analytical model accurately describes $C(W,T)$ dependence.

Abstract

This work discusses results of experimental investigations of the specific heat, $C$, of apple in a wide interval of moisture contents ($W=0-0.9$) and temperatures ($T = 283-363$ K). The obtained data reveal the important role of the bound water in determination of $C(W,T)$ behaviour. The additive model for description of $C(W)$ dependence in the moisture range of $0.1<W<1.0$ was applied, where the apple was considered as a mixture of water and hydrated apple material (water plasticised apple) with specific heat $C_h$. The difference between $C_h$ and specific heat of dry apple, $\Delta Cb=C_h-C_d$, was proposed as a measure of the excess contribution of bound water to the specific heat. The estimated amounts of bound water $W_b$ were comparable with the monolayer moisture content in apple. The analytical equation was proposed for approximation of $C(W,T)$ dependencies in the studied intervals of moisture content and temperature.