Submitted to: Journal of Food Protection
Publication Type: Peer reviewed journal
Publication Acceptance Date: 3/25/2007
Publication Date: 8/1/2007
Citation: Fan, X., Sokorai, K.J. 2007. Effects of ionizing radiation on quality of frozen corn and peas. Journal of Food Protection. 70(8):1901-1908. Interpretive Summary: Human pathogens have been found in frozen vegetables due to contamination from the processing line environment after blanching. Because of the potential presence of human pathogens, it is recommended that frozen vegetables be cooked before consuming. However, frozen vegetables may be used in the thawed, ready-to-eat form in salads or salsas without the recommended cooking step, raising a need for eliminating pathogens from this type of product. In this study, frozen corn and peas were gamma irradiated at three doses, and stored for a year at 0 F. Our results suggested that irradiation at the doses that could achieve up to 5 log reduction of Listeria monocytogenes, a pathogen of concern for frozen vegetables, did not cause consistent effects on color, carotenoid and chlorophyll contents, or antioxidant capacity of frozen corn and peas. However, irradiation tended to have a detrimental effect on the texture of frozen peas, and on the vitamin C content of frozen corn. On the other hand, irradiation significantly reduced the microbial load of frozen vegetables, and increased the display life of peas. The information is useful for the frozen food industry to implement irradiation as a means to enhance safety and maintain quality of frozen vegetables.
Technical Abstract: The effects of irradiation on quality of frozen corn and peas were investigated during long term post-irradiation storage. Frozen corn and peas, irradiated at 0, 1.8, and 4.5 kGy gamma radiation, were stored for up to 12 months at -18 C. Color, texture, ascorbic acid, antioxidant capacity, chlorophyll (for pea only) and carotenoids (for corn only) were measured after 0, 1, 2, 4, 8, and 12 months of storage. Results showed that irradiation did not have a consistent effect on color, pigments or antioxidant capacity of corn and peas. As the irradiation dose increased, the ascorbic acid content of the corn decreased throughout the storage period. The ascorbic acid content of peas was not affected by irradiation in the earlier period of storage (0, 1, and 2 months), but was lower in irradiated samples after 4, 8, and 12 months of storage. Irradiation at 4.5 kGy reduced shear force (texture) for peas during the first 4 months of storage, but the difference disappeared after 8 and 12 months. Compared to the non-irradiated samples, irradiation preserved the green color of peas during post-thawing and display period at an abusive temperature (23 C), while growth of the pea microflora was delayed by irradiation. Our results indicate that irradiation of frozen corn and peas caused a reduction in ascorbic acid content of both vegetables, and a loss of texture on peas, but had no other significant effects on quality.