Peter A. Follett

Irradiation for Quality Improvement and Microbial Safety of Fresh Produce

The first chapter focuses on the purposes of applying ionizing radiation to fruits and vegetables. These include the extension of their useful shelf life by inactivating postharvest pathogens or/and by delaying ripening and senescence, and inhibiting sprouting of tubers, bulbs, and roots of subterranean vegetables. Most important purposes are the improvement of microbial safety associated with human pathogenic bacteria contaminating the fresh produce and providing relevant data on wholesomeness and safety of irradiated food. Chemical and nutritional changes occurring after irradiation should be provided.

Postirradiation Changes in Fruits and Vegetables

This chapter reviews the postirradiation changes in fruits and vegetables, including microbiological changes, changes in quality parameters, nutritional changes (vitamin C content), and chemical changes, including antioxidant capacity, phenolic compounds, and enzymatic changes.

Irradiation for Quality Improvement of Individual Fruits

This chapter reviews the effects of radiation alone or combined with other postharvest treatments on quality parameters of fruits, including citrus fruits, avocados, mangoes, papayas, bananas, pineapples, litchis, persimmons, guavas, annona fruits, pomegranates, dates, figs, pome and stone fruits, strawberries, raspberries, blueberries, blackberries, and kiwifruits. Review on each fruit is accompanied by the beneficial effects of irradiation versus the adverse effects. To allow the use of radiation doses beneath those inducing peel damage, the combination of low doses with other postharvest techniques, acting synergistically or additively, were used. These included heating, modified or controlled atmosphere, modified-atmosphere packaging, various coatings and polymeric film wrapping, chemical application, heated chemicals, cold storage, and others.

Irradiation for Quality Improvement of Individual Vegetables Including Mushrooms

This chapter reviews the effects of radiation alone or combined with other postharvest techniques on shelf life and quality parameters of vegetables. The vegetables included are tomatoes, bell peppers, melons, lettuce, cilantro, cabbage, broccoli, carrots, potatoes, onions, garlic, and mushrooms. Each review is accompanied by beneficial effects of irradiation versus the adverse effects. The combined techniques included heat radiation, heat–chemical radiation, irradiation and modified-atmosphere packaging, irradiation with refrigeration, and wrapping materials.

Sprout Inhibition of Tubers, Bulbs, and Roots by Ionizing Radiation

This chapter focuses on sprout inhibition by irradiation of potato tubers, onion and garlic bulbs, and carrot roots. Factors affecting sprout inhibition and postirradiation changes in these subterranean organs were described.

Irradiation Effects on Mycotoxin Accumulation

This chapter discusses the radiation effects on mycotoxins in infected fruits and vegetables, including patulin, aflatoxins, ochratoxin, and Alternaria mycotoxins. The best way to reduce mycotoxin level is to eliminate the appearance of toxin-producing fungi at preharvest, during harvest, or mainly at postharvest stages.

Benefits of Fruit and Vegetable Irradiation, Labeling and Detection of Irradiated Food, Consumer Attitude, and Future Research

Studies carried out for more than six decades clarified that ionizing radiation can serve as alternative physical means for shelf life extension of fresh produce, decay control, retardation of fruit ripening and senescence processes, maintenance of wholesomeness, enhancement of microbial safety, and sprout inhibition of subterranean vegetables. Irradiation has also been associated with maintenance or enhancement of antioxidant activity. Comparison of irradiation with other preservation techniques of fresh produce clarified its advantages. However, the acceptance of irradiation as a means for preservation of fresh produce and microbial safety has generally met with public opposition because of economic and logistic factors or psychological problems. Attention has been given to the need of sensitive and reliable analytical techniques to identify irradiated food.

Current Issues in Phytosanitary Irradiation

Several issues present barriers to the wider use of phytosanitary irradiation. Because irradiation is characterized as a food additive rather than a process, its use must be disclosed on a label. The labeling requirement may be a drawback for retailers who believe consumers are reluctant to buy irradiated food. The 1-kGy limit is archaic and reduces the efficiency of applying the treatment. The United States Department of Agriculture (USDA) Animal and Plant Health Inspection Service (APHIS) has placed limits on the use of modified atmosphere packaging with irradiation, which disrupts commercial practices that ensure superior commodity quality. The limited number of countries that have approved phytosanitary uses of irradiation is hampering broader adoption because of closed markets.

Ionizing Radiation for Shelf Life Extension

Response of fungal cells to inactivation by ionizing radiation is governed by several factors of which the inherent resistance is the first. Factors affecting the sensitivity to irradiation of postharvest fruits and vegetables and their enzymatic activity have been reviewed. This chapter focuses on the suppressive effects of irradiation on decay development. The impact of irradiation alone or combined with other postharvest techniques on decay suppression and on the ripening process of fruits was discussed.

Phytosanitary Irradiation of Fresh Horticultural Commodities for Market Access

Phytosanitary treatments such as irradiation disinfest host commodities of quarantine insect pests before they are exported to areas where the pests do not occur and are often the simplest approach to overcome regulatory trade barriers and gain market access. Irradiation is a versatile technology to disinfest fresh and durable agricultural commodities of quarantine pests. Irradiation is broadly effective against insects and mites, cost competitive with other disinfestation methods such as chemical fumigation, and fast. Irradiation generally does not significantly reduce commodity quality at the doses used to control insect pests and may extend shelf life. Additionally, irradiation can be applied to the commodity after packaging. Research methods for developing irradiation treatments for insect disinfestation and the history of developing regulations for phytosanitary irradiation are discussed.