Hermetic storage of shelled peanut using the purdue improved crop storage bags

Authors: Butts, Christopher - Chris; Dean, Lisa; Hendrix, Keith; Arias De Ares, Renee; Sorensen, Ronald - Ron; Lamb, Marshall

Submitted to: Peanut Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/30/2021
Publication Date: 5/18/2021
Citation: Butts, C.L., Dean, L.L., Hendrix, K., Arias De Ares, R.S., Sorensen, R.B., Lamb, M.C. 2021. Hermetic storage of shelled peanut using the purdue improved crop storage bags. Peanut Science. 48(1):22-32. https://doi.org/10.3146/PS20-31.1.
DOI: https://doi.org/10.3146/PS20-31.1

Interpretive Summary: One of the primary reasons for food insecurity for persons in developing countries is post harvest losses due to insects, rodents, and mold. The Purdue Improved Crop Storage (PICS) bags are a low cost, reusable, hermetic (low oxygen) storage system for small grains, soybeans, coffee, and cocao. The system consists of two polyethylene bags placed inside one and another, then placed inside an outer woven polypropylene bag to protect against abrasion and punctures. The commodity is placed in the innermost polyethylene bag, then the air is manually squeezed out, and the bag tied closed. The air is then squeezed from the second bag and tied closed. The outer polypropylene bag is closed, too. The two inner bags have very limited permeability to water vapor, oxygen, and carbon dioxide. The commodity and any insects in the bag respire and consume the oxygen. Insects then suffocate in the low oxygen atmosphere created in the bag. Peanuts are a high protein food source and source of income for small stakeholder farmers in developing countries. Peanuts are subject to losses due to insects, rodents and aflatoxin contamination. There has been no published research on the feasibility of storing shelled peanuts in the PICS bags. This study stored peanuts for 301 days in conventional 50-lb burlap bags and in PICS bags. Samples were taken periodically throughout the storage period and evaluated for moisture content, seed quality, aflatoxin, insect/rodent damage, flavor, and oil stability. During this study, the peanuts stored in the burlap bags suffered considerable damage due to insect infestation and moisture loss in response to the environmental conditions. Peanuts regained moisture when the ambient relative humidity increased. Seed germination rates remained above 70% for approximately 250 days. Several burlap bags were damaged by rodents and peanuts spilled/lost in spite of efforts to minimize rodent access. The peanuts stored in the PICS bags increased slightly in moisture because the relative humidity in the bag remained between 70 and 80%. As a result of the continuous high humidity in the bag, the germination rate decreased continuously throughout the storage period with no peanut seed germinating by the end of the study. There was no insect damage observed in the PICS bags. Only 2 of the 36 PICS bags suffered any rodent damage even though they were stored next to the burlap bags in the same structure. The peanuts stored in the PICS bags, did have a white, powdery mold that grew on the surface. The mold was identified and described as a very slow growing mold that had not been previously identified in peanut. In conclusion, PICS bags can be used to store shelled peanuts to minimize insect and rodent damage. Peanuts should not be stored in the PICS bags if their moisture content is greater than 7%.

Technical Abstract: Low oxygen or hermetic storage has been successfully used to store several commodities such as small grains, cocoa, and coffee. However, previous research using hermetic storage for peanut or groundnut has had mixed results. This research was conducted to determine the effect of storing shelled peanuts in PICS (Purdue Improved Crop Storage) bags for up to 12 months on aflatoxin contamination, seed germination, and oil chemistry. Treatments for the study included: 1) normal and high oleic peanuts, 2) two initial moisture contents, and 3) four storage treatments. The four storage treatments were 1) burlap bags as the control, 2) PICS bags, 3) PICS bags with air extracted by vacuum, and 4) PICS bags with sachets of chlorine dioxide (ClO2) dry fumigant added. There were three replications of each treatment combination. Peanuts were stored in an area maintained at a temperature above 21C. The initial seed germination of the normal oleic and high oleic peanuts was 77 and 80%, respectively. Initial aflatoxin concentration in all peanuts was less than 2 ppb. Bags were opened, sampled, and resealed at 60, 159, 249, and 301 d of storage. Approximately half of the 12 burlap bags suffered significant rodent damage, and all had significant infestation by Indian meal moth (Plodia interpunctella). Only 4 PICS bags had rodent damage with damage limited to the outer polypropylene bag. There were no live insects in the PICS bags. Seed germination decreased for all samples to an average of 6.3%. The peanuts stored in the burlap bags had an average germination of 19.2% compared to 2.1% for the peanuts stored in PICS bags. The aflatoxin concentration in one of the burlap bags with normal oleic peanuts was 75 ppb, and one of the PICS bags with high oleic peanuts had an aflatoxin concentration of 12 ppb. The remaining samples had aflatoxin below the detectable limit of 2 ppb