Evaluation of a small-scale desiccant-based drying system to control corn dryness during storage

Alexandra Mora; Umayr Sufi; Jedediah I. Roach; James F. Thompson; Irwin R. Donis-Gonzalez; Alexandra Mora; Umayr Sufi; Jedediah I. Roach; James F. Thompson; Irwin R. Donis-Gonzalez

doi:10.3934/agrfood.2019.1.136

AIMS Agriculture and Food

2019, Volume 4, Issue 1: 136-148. doi: 10.3934/agrfood.2019.1.136

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Research article

Evaluation of a small-scale desiccant-based drying system to control corn dryness during storage

Department of Biological & Agricultural Engineering, University of California, Davis, One Shields Ave, Davis, CA 95616, USA

Received: 13 September 2018 Accepted: 24 January 2019 Published: 14 February 2019

Approximately 4.5 billion people worldwide are negatively affected by mycotoxins, especially small-scale farmers in regions that do not have access to energy efficient and appropriately designed drying systems. Mycotoxins are produced by fungi tainting durable commodities (e.g. corn and rice), which have been inadequately dehydrated and stored. Controlling produce dryness to below 0.6 water activity (A_w) is an imperative factor to maintain their safety and quality. Unfortunately, there is a lack of inexpensive, small-scale (<15 kg) technologies to adequately dry and store durable commodities. A potential solution is to utilize small-scale desiccant-based drying systems to reduce and then maintain the optimum A_w and dry basis moisture content (M_D). Desiccants, like hygroscopic salts and DryBeads^TM, can be used to remove the moisture from surrounding commodities and potentially maintain conditions during storage. For small-scale applications, it is important to keep the design low-cost and energy efficient. Utilizing corn (Zea mays) as a model product, the current study aims to evaluate a small-scale desiccant drying system consisting of two stacked 18.9 L (5 gallon) buckets equipped with a centered 51 mm diameter acrylonitrile-butadiene-styrene (ABS) pipe to support a fan (102 mm × 102 mm × 25 mm) to circulate air (mean air-flow = 0.015 m³-s ⁻¹, 31.8 cfm). Potassium carbonate (K₂CO₃), magnesium chloride (MgCl₂), sodium iodide (NaI), and DryBeads^TM were compared against an untreated control in their ability to reduce the A_w below 0.6 and hold it over 14 days of storage without over-drying the corn. The small-scale desiccant system combined 0.73 kg of each desiccant and 9 kg of corn with an initial M_D of 19.6% (dry basis). Twelve 50 g corn samples contained in mesh bags were distributed at three levels (top, middle, and bottom) within each bucket to later infer the corn’s final M_D and A_w. In addition, temperature (T), and relative humidity (RH) at the three levels were recorded each hour with T/RH sensors. Results indicated that all of the evaluated desiccants significantly (p ≤ 0.05) reduced the corn’s A_w below 0.6, in comparison to the untreated control, after 14 days of drying/storage.
- hygroscopic,
- desiccation,
- storage,
- relative humidity,
- temperature
Citation: Alexandra Mora, Umayr Sufi, Jedediah I. Roach, James F. Thompson, Irwin R. Donis-Gonzalez. Evaluation of a small-scale desiccant-based drying system to control corn dryness during storage[J]. AIMS Agriculture and Food, 2019, 4(1): 136-148. doi: 10.3934/agrfood.2019.1.136

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Abstract

Approximately 4.5 billion people worldwide are negatively affected by mycotoxins, especially small-scale farmers in regions that do not have access to energy efficient and appropriately designed drying systems. Mycotoxins are produced by fungi tainting durable commodities (e.g. corn and rice), which have been inadequately dehydrated and stored. Controlling produce dryness to below 0.6 water activity (A_w) is an imperative factor to maintain their safety and quality. Unfortunately, there is a lack of inexpensive, small-scale (<15 kg) technologies to adequately dry and store durable commodities. A potential solution is to utilize small-scale desiccant-based drying systems to reduce and then maintain the optimum A_w and dry basis moisture content (M_D). Desiccants, like hygroscopic salts and DryBeads^TM, can be used to remove the moisture from surrounding commodities and potentially maintain conditions during storage. For small-scale applications, it is important to keep the design low-cost and energy efficient. Utilizing corn (Zea mays) as a model product, the current study aims to evaluate a small-scale desiccant drying system consisting of two stacked 18.9 L (5 gallon) buckets equipped with a centered 51 mm diameter acrylonitrile-butadiene-styrene (ABS) pipe to support a fan (102 mm × 102 mm × 25 mm) to circulate air (mean air-flow = 0.015 m³-s ⁻¹, 31.8 cfm). Potassium carbonate (K₂CO₃), magnesium chloride (MgCl₂), sodium iodide (NaI), and DryBeads^TM were compared against an untreated control in their ability to reduce the A_w below 0.6 and hold it over 14 days of storage without over-drying the corn. The small-scale desiccant system combined 0.73 kg of each desiccant and 9 kg of corn with an initial M_D of 19.6% (dry basis). Twelve 50 g corn samples contained in mesh bags were distributed at three levels (top, middle, and bottom) within each bucket to later infer the corn’s final M_D and A_w. In addition, temperature (T), and relative humidity (RH) at the three levels were recorded each hour with T/RH sensors. Results indicated that all of the evaluated desiccants significantly (p ≤ 0.05) reduced the corn’s A_w below 0.6, in comparison to the untreated control, after 14 days of drying/storage.

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