Fruit irradiation processes

Radiation sterilization produces foods that are stable at room temperature and requires a dose of 20 to 70 kGy. At lower doses, longer shelf life may be obtained, especially with perishable foods such as fruits, fish, and shellfish. The destruction of Salmonella in poultry is an application for radiation treatment. This requires doses of 1 to 10 kGy. Radiation disinfestation of spices and cereals may replace chemical fumigants, which have come under increasing scrutiny in recent years. Dose levels of 8 to 30 kGy would be required. Other possible applications of irradiation processing are inhibition of sprouting in potatoes and onions and delaying of the ripening of tropical fruits. 

Administration (FDA), for example, requires testing of all new drugs, and 80 percent of that testing employs radioisotopes. But radiation is also widely used to treat products, especially in agriculture, where an irradiation process exposes food to gamma rays from a radioisotope of cobalt 60 to eliminate potentially harmful or disease-causing elements. Even livestock products are covered. Like its counterparts in at least ten other countries, the FDA approves the use of irradiation for pork, poultry, and red meat as well as for fruits, vegetables, and spices in order to kill bacteria, insects, and parasites that can lead to such diseases as salmonella and cholera. 

Perhaps the most fruitful of these studies was the radiolysis of HCo(C0)4 in a Kr matrix (61,62). Free radicals detected in the irradiated material corresponded to processes of H-Co fission, electron capture, H-atom additions and clustering. Initial examination at 77 K or lower temperatures revealed the presence of two radicals, Co(C0)4 and HCo(C0)4 , having similar geometries (IV and V) and electronic structures. Both have practically all of the unpaired spin-density confined to nuclei located on the three-fold axis, in Co 3dz2, C 2s or H Is orbitals. Under certain conditions, a radical product of hydrogen-atom addition, H2Co(C0)3, was observed this species is believed to have a distorted trigonal bipyramidal structure in which the H-atoms occupy apical positions. 

HPhe radiation preservation of fresh fruits and vegetables has received considerable attention as one of the promising applications for food irradiation. As with most other applied aspects of food irradiation, however, the process is not without complications. This paper is concerned only with the effect of gamma radiation upon fresh commodities, drawn principally from work conducted at this laboratory. No effort is made to cover all of the changes occurring but rather only a few which illustrate the problems or limit the practical application of the process. 

The effect of radiation on the biochemical processes of fresh fruits and vegetables is of considerable interest from the standpoint of its influence on shelf life. A number of studies on the effect of radiation on respiration have indicated a general stimulation of both oxygen uptake and carbon dioxide evolution during the irradiation period, subsiding to near-normal rates shortly following the cessation of treatment (21, 23, 24, 38). 

What are the benefits of using irradiation It can kill viable organisms and specific, non-spore forming, pathogenic microorganisms such as salmonella, or it can interfere with physiological processes for instance it can be used for sprout inhibition of potatoes or for extending the shelf-life of fresh fruit. In short, irradiation of food is an alternative, and in some cases the only, method to ... 

In addition to the traditional canning, freezing, pickling and dehydration processes, several new processing techniques have surfaced in recent years. Irradiation with gamma rays, storage with controlled and modified atmospheric environment, reverse osmosis and ultrafiltration will be discussed in subsequent chapters. The emphasis will be on chemistry of quality improvement of the processed fruit and vegetable products. 

A recent trend in marketing fresh fruits is to wrap each fruit individually. It should improve the fruit s appearance and minimize abrasion between fruits. However, this would require finding a film with the optimal permeability for air, water vapor, ethylene and carbon dioxide between the fruit and the surrounding atmosphere so as to slow down the fruit s respiration rate, and to maintain the proper relative humidity. If irradiation and a fungicidal agent can be incorporated into the process and packaging, it should further extend the shelf-life of the fruit substantially. 

The second chirality source used in the synthesis of aminocyclopropane carboxylic acids was D-glyceraldehyde acetonide, which after Wittig-Homer-Emmons reaction provided the alkenes 61. Treatment with diazomethane and subsequent irradiation at low temperatures alforded the cyclopropanes 62, which were converted into several other derivatives by modification of the side chain (Scheme 11). Notably, the best results were obtained by irradiating in the presence of benzophenone as triplet sensitizer [33, 34]. Following a similar synthetic procedure allocoronamic acid 65 was prepared, which is one of the amino acids that can be processed by plant tissues and promises the possibility to control the enzymatic processes underlying plant growth and fruit ripening [35]. 

---