The effects of gamma irradiation on the microbiological, physical and sensory qualities of diced tomatoes

Diced Roma tomatoes were treated with gamma irradiation and evaluated for changes in microbial, physical, chemical and sensory properties. Dosages for Trial I were 0.0,0.39,0.56 and 1.82kGy and in Trial 2,0.0,0.50,1.24 and 3.70 kGy. Irradiation at 3.70 kGy resulted in no aerobic populations through day 12 and significantly fewer colonies through day 15 whereas yeast and mold populations experienced a 2log reduction through day 12. Color, titratable acidity, and degreesBrix were not significantly affected by irradiation. Tissue firmness decreased with increasing dose but not with storage time. Treatment with 3.7kGy decreased firmness by 50% and 20% with 0.5kGy, however, the reduced firmness induced by 0.50kGy was undetected by a 9 member trained sensory panel. A significant (pless than or equal to0.05) inverse correlation between changes in texture and water-soluble pectin (WSP) was determined while total pectin remained relatively constant and oxalate soluble pectin content decreased slightly with irradiation dose. The significant inverse correlation between the loss of firmness and WSP indicates that the changes in WSP play an important role in the tissue softening of tomatoes, This study indicates that irradiation at 0.5 kGy can reduce microbial counts substantially to improve microbial shelf life without adverse effects on sensory qualities. (C) 2002 Published by Elsevier Science Ltd.