Cold and Dry Chain to Reduce Food Loss and Waste
This post was written by Peetambar Dahal, Kent Bradford and Pedro Bello, University of California, Davis, United States; Johan Van Asbrouck, Rhino Research, Thailand; Keshavulu Kunusoth, Telangana State Seed and Organic Certification Authority, India; Irfan Afzal, University of Agriculture, Faisalabad, Pakistan; Tim Letzkus, Food Rescue, White Pony Express, Pleasant Hill, California, United States; Filippo Guzzon, European Cooperative Programme for Plant Genetic Resources (ECPGR), Alliance Bioversity International-International Center for Tropical Agriculture (CIAT), Rome, Italy; and Ravi Kafle, Department of Public Health, Washington State, United States.
Why Cold and Dry Chain preservation?
The Cold Chain, including modified ecofriendly variations, is being used for prolonging quality of perishables by utilizing refrigeration to maintain high moisture content (MC) and low product temperatures. The Dry Chain, analogous to the Cold Chain, is proposed to maintain the quality of low MC products (seeds, foods and feeds) at ambient temperatures without requiring expensive infrastructure. Low MC products are dried to safe humidity levels and packaged into moisture-proof containers until used, thereby minimizing losses at farms and through the downstream value chain. This process has been used by gene banks, seed companies, food manufacturers and the pharmaceutical industry in developed countries to minimize quality loss of dry products during storage.
The Dry Chain, developed with the support of the USAID Horticulture Innovation Lab at UC Davis, California, enables health-centric food systems by extending seed longevity and minimizing food contaminants (e.g., mycotoxins) and insect infestation and nutrient loss. It complements food, nutrition security and disaster resiliency and agrobiodiversity conservation. Furthermore, the Dry Chain could save about 25% food losses at farms in the developing countries that could help countries to improve dry product trade ratios. Although this technology complements central issues of food security identified by USAID and several other global programs, it has yet to be used by the food stakeholders in the developing countries.
Dry Chain implementation
Implementing the Dry Chain could minimize most of carcinogenic mycotoxins (aflatoxins), which affects 4.5 billion people in developing countries. In combination with good agricultural practices (GAP), including Aflasafe, the Dry Chain should be optimally initiated soon after the harvest when seed quality and nutrients are at peak levels. Seeds could be a good implementation point before scaling up Dry Chain to reduce farm food losses.
The Dry Chain can be implemented using climate-smart tools like natural drying, solar dryers, regenerable drying beads and heated air dryers. Drying beads are especially useful for low-volume and high-value seeds and can replace existing Cold Chain gene bank infrastructure. Moisture-proof packaging is essential following drying to prevent reabsorption of water from the air in humid climates. Bill and Melinda Gates Foundation (BMGF)- and USAID-supported triple-layer Purdue Improved Crop Storage (PICS) bags are handy containers to enable Dry Chain systems.
Dry Chain steps
- Preharvest measures: Seeds of improved/local varieties should be planted using GAP. Integrated Pest Management (IPM) that uses biological measures but embraces pesticides as the last resort is recommended to minimize chemical residues in both low and high MC foods. Areas receiving high rainfall, as in tropical climates, need preharvest application of Aflasafe, a mixture of country-specific atoxigenic Aspergillus strains to outcompete toxigenic ones.
- Drying after harvest: Harvest seed/grain at proper maturity and use natural or artificial drying systems to reduce MC to 10-12% or 65% equilibrium relative humidity (eRH) or lower. Drying prevents growth of toxigenic storage molds and insects that proliferate concomitant with nutrient losses at higher humidities. Dry products harvested during the dry season can utilize repeated natural drying. However, dry products harvested during the rainy season need rapid drying using artificial dryers that could also use solar energy. Ecofriendly solar drying tools have been discussed even for drying high MC foods. Seeds need lower MCs than grain products and high viability has been maintained for several decades. Expensive dehumidified cold storage has been proposed to store seed in the developing countries. Instead, regenerable drying beads could be used to maintain local and improved cultivars in dry storage, even in humid climates.
- Checking dryness: In addition to traditional drying knowledge, inexpensive handheld devices, DryCards and humidity strips could be used to measure eRH of stored products. A moisture content calculator can convert eRH values of handheld devices to traditional MC values.
- Moisture proof containers: The BMGF- and USAID-supported moisture-proof triple-layer PICS bags are preferred over other containers throughout the postharvest value chain. Other plastic or metallic containers with airtight seals could also be used to prevent moisture penetration into the storage container. These containers protect dry products from rainfall/annual flooding and enable disaster resiliency by addressing food safety.
- Quality assurance: Implementing sensitive quality monitoring systems to conform to Codex standards for both domestic and imported low and high MC foods will promote exports and improve livelihoods of smallholders.
- Dissemination of knowledge: Digital apps could be useful to disseminate such knowledge to food stakeholders. Training on drying systems and hermetic storage is needed to implement the quality-oriented, pesticide-free and climate smart Dry Chain to reduce food loss in the developing countries.