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Controlled drying and rehydrating of almonds on a farm scale in Australia

Published by the American Society of Agricultural and Biological Engineers, St. Joseph, Michigan

Citation:  2018 ASABE Annual International Meeting  1800705.(doi:10.13031/aim.201800705)
Authors:   John M Fielke
Keywords:   Almonds, Air flow, Dehydration, Moisture Content, Quality, Psychrometric, Rehumidification

Abstract. A major quality parameter for almonds is their kernel moisture content. Too dry and they are easily damaged during processing and if too wet they lose their “crunch” when eaten and are susceptible to mold growth. Hence, almond growers aim to be just under the receival moisture limit of 6% kernel moisture content. However, as almonds are a field dried product they sometimes are harvested either too dry or too wet. The objective of this work was to show that by adding an evaporative cooler to the aeration fan the air conditions being blown through the bulk almonds can be produced at the required kernel equilibrium moisture content (15-25ºC with 55-65% RH) during hot and dry weather. Alternatively, during cold and humid weather a heater could be used to produce these conditions. To demonstrate this principle 116 tonnes of over-dried almonds were placed in a triangular shaped stockpile over an aeration duct with a fan and evaporative cooler attached at each end. The almond kernel moisture content was measured in-situ using wireless temperature and humidity sensors placed on spears that went 1 m into the stockpile. Tests confirmed that the rehumidification was uniform and the kernel moisture content moved over time toward the desired moisture content with no over wetting or drying of the almonds when the aeration air‘s humidity was controlled. The results show a new paradigm in moisture control of products stored in bulk that are being aerated for moisture adjustment that does not rely on precise ambient air conditions.

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