Abstract
ABSTRACTAlmond fruits are subjected to various mechanical stresses throughout production, from harvest to processing, storage and packaging. Kernel properties play an important role in reducing mechanical damage such as scratches and penetration of shell pieces. Knowledge of kernel properties under various conditions of the fruit can assist in optimising post-harvest and processing lines to minimise kernel damage and thus maximise final kernel quality. Kernel moisture content is one of the main attributes affecting the kernel’s response to mechanical processing. Increasing the kernel moisture content to an optimum level through wetting fruit prior to processing can lead to a reduced percentage of damaged kernel. Water added to the structure of kernels acted as a plasticiser and helped the kernels to absorb the mechanical load instead of fracturing and breaking into pieces. In this study, tests were conducted on almond kernels with different moisture content levels from 5.52 to 14.09g/100g wet basis. Kernels from a Nonpareil variety were tested in dried and wetted conditions. Test results showed that kernels with higher moisture content were able to undergo a larger deformation at a given force value in comparison with dry kernels. Average deformation for dry samples was from 0.12 mm, which increased to an average of 0.25 mm in wetted samples. The effect of skin on the mechanical properties of the kernels (with and without skin) was studied using a mechanical tester. The test results showed a peak force value in samples tested with skin in comparison with the kernels tested without skin.
Highlights
Almonds are harvested dry with a kernel moisture content of less than 7 g/100g wet basis Micke.[1]
The force versus displacement curves obtained for kernels with skin layer at each moisture content level provided peak forces at average loads of 1.64, 1.88, 1.89, and 1.91 N for kernels with moisture contents of 5.52, 9.55, 10.08, and 14.09 g/100g wet basis, respectively
The mechanical properties of almond kernels were investigated at different moisture levels
Summary
Almonds are harvested dry with a kernel moisture content of less than 7 g/100g wet basis Micke.[1]. Almond processing consists of various loading stages where the fruit undergoes compression, shear and impact in order to hull and shell the fruit and release the kernel. Commercial hulling and shelling operations are done on in-hull fruit using shear rollers and/or rolls over belts Micke[1] to break the hull and shell layers and release the kernel. There are recommendations for using impact threshing systems in removing hull and shell for harder shell varieties of almonds Shirmohammadi and Fielke.[2] The current commercial systems release the kernel through several loading stages and usually create a high percentage of kernel damage including broken, chipped and scratched product. In order to define why and where the damage occurs during processing, it is essential to develop a detailed knowledge of kernel physical and mechanical properties. The properties mentioned define the sensory and textural characteristics of kernels, which are very important aspects of nut quality and standard Saeleaw and Schleining.[3]
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