Combination irradiation treatments for food safety and phytosanitary uses

Abstract

Purpose of the review: Combination of irradiation treatment with other preservation techniques is of potential importance in enhancing the effectiveness and reducing the energy or dose requirement for destroying food borne illness and spoilage organisms while retaining or improving product quality. Phytosanitary irradiation to control quarantine pests, particularly insects, in traded fresh commodities may also benefit from combination with other disinfestation techniques to enhance effectiveness, and to reduce costs, treatment time, and product damage. Main findings: Combined preservation treatments can be beneficial to eliminate pathogenic bacteria due to the synergistic or additive effect of the treatments. It also permits less extreme use of a single treatment which may protect the sensory quality of the foods. Combination with modified atmosphere packaging (MAP), refrigeration, freezing or heating has great potential for improving the quality and the safety of fresh and processed foods. Irradiation and heat treatments reduce the numbers of pathogenic bacteria and the level of normal flora, while MAP and cold suppresses the growth of the survivors during subsequent storage. The use of natural antimicrobials at concentrations that do not affect the sensory qualities can increase the relative sensitivity of bacteria by >4-fold and can reduce the radiation dose necessary to eliminate pathogens. Natural antimicrobials are normally not stable over time; microencapsulation and the use of edible coatings can improve stability of antimicrobial formulations and prolong their bioactivity. Phytosanitary irradiation doses to control insects (50 to 400 Gy) are relatively low compared to doses for food safety and sterilization applications. Lowering doses further could save money on treatment costs by reducing treatment time, increasing the capacity of irradiation facilities, and reducing any problems with commodity quality. Combining irradiation with other insect disinfestation modalities such as cold, heat, fumigation, modified atmospheres, and chemical insecticides is a possible means to reduce the radiation dose, and the duration, level, or concentration of the companion treatment while meeting the technical objectives of the quarantine treatment. Irradiation in combination with cold is particularly promising, as it may be a means to reduce the duration and therefore costs of current cold treatment protocols. Irradiation may also allow use of higher cold temperatures that do not cause chilling injury in cold-sensitive fruits. Directions for future research: The efficacy of active edible coating and active biodegradable packaging in combination with irradiation for microbial control needs further investigation and should be demonstrated at the industrial level. The use of combined treatments to eliminate viruses and parasites in food is not well studied and should be investigated. The effects of mild heat treatment before irradiation on insect radiotolerance and bacteria radiosensitization should be investigated. The relationship between MAP packaging and insect radiation tolerance needs to be explored for a wider variety of quarantine pest species, including surface pests and inherently tolerant Lepidoptera and mites. Additional research is needed to demonstrate the efficacy of irradiation plus cold combination treatments against insects in fresh produce while assessing commodity quality and the potential for commercial application.