Potatoes irradiated

Kameyama, K., Ito, H. (2000). Twenty-six years experience of commercialization on potato irradiation at Shihoro. Japan. Radiat. Phys. Chem., 57, 227-230. 

In 1958 Hetherington and Al Lillie met with officials from the Canadian Federation of Agriculture to solicit their support for the process. These representatives in turn put CPD in touch with major potato wholesalers and producers in the Maritimes. These businesses expressed interest in the concept, but there the initiative stalled because CPD could provide no tangible evidence that potato irradiation could work cost-effectively. It needed a demonstration irradiator if it was going to move the program another step towards commercial viability. Ideally it wanted a mobile unit that could be taken around to potential customers so that they could test it with as little inconvenience as possible. 

Potato irradiation seemed to be on the brink of market acceptance, but a serious reversal was in the offing. Newfield Products lost 350,000 in its first year of operation. Part of the loss was attributable to a poor crop, but Newfield had also been playing the potato futures market. Lacking enough capital to absorb the losses, it ended up going... 

A former CPD employee, John Masefield, built the first commercial potato-irradiation plant at St-Hilaire, Quebec in 1963. These potato bins illustrated the diffirence between irradiated (left) and untreated potatoes after months of storage. 

Some 40 countries have cleared irradiated foods of certain types for human consumption, or have given provisional clearance. Large scale ( 104 tons per year) irradiation of potatoes has been approved in Japan, and very large scale ( 105 tons per year) irradiation of grains has been reported from the former Soviet Union for insect control. However, it must be admitted that clearances with associated legal complications have come slowly in most countries, and even today there are ongoing debates regarding the ethics and economics of food irradiation. 

The dose required to inhibit sprouting of onions, shallots, and garlics is 0.03-0.12 kGy. For good sprout control of tubers such as potatoes and yams, somewhat higher doses, 0.08-0.14 kGy, are required. Because of decreased wound-healing ability after irradiation, doses in excess of 0.15-0.2 kGy may induce increased microbial rot in storage [24]. 

In irradiated potatoes, especially in some varieties and as a function of cultivating conditions of the raw material, after-cooking darkening may occur. This discoloration is attributed to formation of ferric-phenolic complexes. This phenomenon depends on the iron content, and is related to increased polyphenol formation and reduced citric acid levels, which are influenced by agronomic and climatic factors. Various technological measures have been developed to prevent this after-cooking darkening [23]. 

Because potatoes are good source of vitamin C, it is important to point out that irradiation does not adversely affect the vitamin C levels [23,30]. Although some ascorbic acid is converted into dehydroascorbic acid on irradiation, the latter is also biologically active. 

In Japan, where the use of chemical sprout suppressants is not permitted, commercial irradiation of potatoes has been introduced in 1973 in Shihoro, Hokkaido, where an industrial scale irradiator has been processing about 15,000-20,000 tons of potatoes armually [31,32]. The success of this system is due in large measure to careful handling of the product before and after treatment. 

In a recent study in the United States, irradiation of a prepared meal consisting of Salisbury steak, gravy, and mashed potatoes at 5.7 kGy effectively eliminated the background microbial population and high concentrations of L. monocytogenes contamination without causing adverse effects on quality [91]. 

The ICGFI [149] estimates that irradiation cost range from 10 to 15 per tonne for a low-dose application (e.g., inhibition of sprouting of potatoes or onions), and 100 to 250 per tonne for a high-dose application (e.g., to ensure hygienic quality of spices). These unit costs are considered to be competitive with alternative treatments. 

In order to develop an efficient procedure for obtaining a desired mutation, ion beams were applied to tobacco anthers, and potato virus Y (PVY)-resistant mutants have been selected. A high frequency (2.9-3.9%) of resistant mutants was obtained by the irradiation of C and He ions with a dose of 5-10 Gy [112,113]. 

Dale,M. F. B., Griffiths, D. W., Bain, H., Goodman, B. A. (1997). The Effect ofGamma Irradiation on Glyeoalkaloid and Chlorophyll Synthesis in Seven Potato Cultivars. J Sci Food Agric., 75, 141-147. 

Gokmen, V., Akbudak, B., Serpen, A. (2007). Effects of controlled atmosphere storage and low-dose irradiation on potato tuber components affecting acrylamide and color formations upon frying. European Food Research and Technology, 224, 681-687. 

Cao, W., Tibbitts, T. W. (1991b). Physiological response in potato plants under continuous irradiation. J. Amer. Soc. Hort. Sci., II6, 525-527. 

Tibbitts, T. W., Bennett, S. M., Cao, W. (1990). Control of eontinuous irradiation injury on potatoes with daily temperature cycling. Plant Physiol., 93,409 11. 

Wheeler, R. M., Tibbitts, T. W., Fitzpatrick, A. H. (1991). Carbon dioxide effects on potato growth under different photoperiods and irradiance. Crop Set, 31,1209-1213. 

Yorio, N. C., Wheeler, R. M., Weigel, R. C. (1995a). Effect of irradiance, sucrose, and CO2 concentration on the growth of potato (Solarium tuberosum) in vitro. NASA Tech Mem, 110654. 

One potentially unfavorable observation has been made by Hannan (H2). He found some tissue damage in the irradiated tubers. It remains therefore to be shown whether the irradiated potatoes can be shipped and processed via normal channels. 

Potato, com, and wheat starch was irradiated with 9 X 1014 neutrons/cm2. Neutrons cause only a weak peptonizing effect in comparison with 7-rays (2 X 106 rep) (see Table VIII). In the first case, starch becomes radioactive. Radioactive nuclei in starch are mostly phosphate isotopes and only to a very minor extent 14C. The behavior of starch of all three origins in respect to both types of irradiation is nonuniform. Generally neutron radiation does not eliminate phosphoric moieties from starch and is less destructive.77... 

Very few reports have been published on the use of X-rays for modification of starch, although the formation of deoxy compounds on irradiation of solid potato starch with 5 X 106 rads under nitrogen has been described. The amount of deoxy compounds formed is related almost linearly to the irradiation dose, and formation of 2-deoxy-D-arabi no-hexose is the major process there are almost no side-pro-cesses. Similar qualitative, but not quantitative, behavior is shown by 1% aqueous solutions of D-glucose, D-xylose, L-arabinose, D-ribose, sucrose, and cellulose powder (Fig. 14). Starch is the most resistant to irradiation among carbohydrates tested.74... 

Starch pastes irradiated with 130,000 V, 15 mA X-rays lost their viscosity, and there was concurrent decrease of iodine-binding ability and pH. Other properties measured after such treatment point to dextrinization and oxidation of starch.78-79 Other results of such irradiation is the cleavage of phosphoric acid esters from glucose units of potato starch. This effect is observed at 50,000 V and 8 mA as well as at 150,000 V and 12 mA. The effect of X-ray irradiation is similar in this respect to irradiation with 7-rays, whereas neither sonication with ultrasound nor exposure to UV light evoke such effects.5 Starch irradiated by X-rays, contains free radicals, and thus the presence of free radicals in starch provides evidence of previous irradiation. 

Irradiation of potato starch granules with high-energy electrons in doses up to 107 rads does not affect the material to any significant extent. The microscopic appearance and gelatinization temperature do not change. However, both solid... 

Properties of Granular Potato Starch, Amylose, and Amylopectin after Irradiation with High-Energy Electrons"... 

Fig. 15.—ESR signals of irradiated potato starch as a function of time of the process.81 (a) Measurements in air, 150-kV X-rays, 3-Mrad dose (a,) measurements in air, 400-keV electrons, 10-Mrad dose (n) measurements under nitrogen, 150-kV X-ray, 3-Mrad dose (n,) measurements under nitrogen, 400-keV electrons, 10-Mrad dose.

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