Hand Warmers: A Cost-Effective Solution to Accelerate Oxygen Depletion During Hermetic Storage

Postharvest grain losses often result from insect infestations. Hermetic storage creates airtight conditions that limit insect survival. However, oxygen depletion can be slow during hermetic storage, leading to a loss of grain quality and market value. Oxygen scavengers offer a solution to accelerate oxygen depletion. This study evaluated hand warmers as a cost-effective alternative to commercial oxygen scavengers. Experiments in sealed empty 4-gallon glass jars with 10-h hand warmers depleted oxygen faster and more cost-effectively than those with 2000 cc Oxy-Sorb oxygen absorbers. One hand warmer depleted similar amounts of oxygen as two Oxy-Sorb oxygen absorbers and reached the 5% threshold for pest suppression in 48 h. A follow-up study found that oxygen levels in empty 4-gallon jars dropped faster than in grain-filled 25-kg hermetic bags, with jars containing two or three hand warmers reaching the 5% threshold in the first 6 h. Temperature remained constant regardless of the number of hand warmers. At the same time, the relative humidity rose in empty jars but stayed stable in grain-filled hermetic bags, with no effect on grain quality. Hand warmers can potentially serve as cost-effective alternatives to commercial oxygen scavengers in hermetic storage.