Effects of low-pressure storage of food commodities on the mortality of adult stored product insects

B D Rohitha Prasantha

doi:10.4038/sljb.v5i1.52

Abstract

The food industry faces serious problems regarding pest infestation leading to high storage loss of food commodities. Due to adverse impacts of chemical preservation methods, a promising physical method of food protection could be considered as an urgent need. This study investigated the effect of low-pressure (vacuum) on the mortality of adults of three stored product pests of drug store beetle (Stegobium paniceum L.), southern cowpea weevil (Callosobruchus chinensis L.) and red flour beetle (Tribolium castaneum Herbst). The pests were exposed to 20 kPa and 10 kPa vacuum at 37 ºC and 75% relative humidity. Mortality of the insects was recorded at 8 h and 32 h after vacuum treatments. There were significant differences (p<0.05) in the susceptibility to the vacuum treatment among the tested pests. Adults of C. chinensis showed comparatively less susceptibility to the vacuum treatment compared to S. paniceum and T. castaneum. Mortality of insects exposed to two low-pressure treatments did not show 100% mortality at the two exposure periods, irrespective of the type of food materials and species. The mean percentage mortality increased by about 66.0±5.7% when vacuum pressure increases from 20 kPa to 10 kP irrespective of the species, exposure time and the products. The oxygen concentration decreased to >70% inside the vacuum chamber during treatments.

Highlights

Cosmopolitan insects such as the Indian meal moth (Plodiainter punctella Hübner), Angoumois grain moth (Sitotroga cerealella Olivier), weevils (Sitophilus spp.), red flour beetle (Tribolium castaneum Herbst), southern cowpea weevil (Callosobruchus chinensis L.), lesser grain borer (Rhyzopertha dominica L.), cigarette beetle (Lasioderma serricorne F.), drug store beetle (Stegobium paniceum L.) and saw-toothed grain beetle (Oryzaephilus surinamensis L.) are some of the stored product pests found in Sri Lanka, causing considerable economic loss to the food industry
The mean moisture contents of the product remained constant (p>0.05), even after 32 h of vacuum treatments at 20 kPa and 10 kPa pressure compared to the initial sample (Table 1)
Adult stages of T. castaneum and S. paniceum were more susceptible to vacuum treatments than the adults of C. chinensis

Summary

Introduction

Cosmopolitan insects such as the Indian meal moth (Plodiainter punctella Hübner), Angoumois grain moth (Sitotroga cerealella Olivier), weevils (Sitophilus spp.), red flour beetle (Tribolium castaneum Herbst), southern cowpea weevil (Callosobruchus chinensis L.), lesser grain borer (Rhyzopertha dominica L.), cigarette beetle (Lasioderma serricorne F.), drug store beetle (Stegobium paniceum L.) and saw-toothed grain beetle (Oryzaephilus surinamensis L.) are some of the stored product pests found in Sri Lanka, causing considerable economic loss to the food industry. Adult insects fly towards food manufacturing facilities and warehouses for oviposition and feeding. Adults would later be present in the packaged foods products such as flour, pet food, biscuits, nuts, dried fruits, chocolates, powdered milk and other food commodities (Riudavets et al, 2009; Noomhorm et al, 2009). The larvae of moths about to pupation emerge through the packages for pupation (Mullen & Pedersen, 2000). Such damage to the packaging materials later incurs many insect and fungal infestations. Other larval stages grow inside the food commodities without being seen from the outside and cause heavy damage to the stored products

Methods

Results

Discussion

Conclusion