الفهرس 
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Abstract
a - Fresh Fruits :
Strawberries are among the more suitable fruits •which could be preserved by irradiation with low doses (pasteurizing doses) . The purpose of this investigation is to study the effect of applying Gamma-irradiation f or
extending t he shelf- life of strawberry fruit of the American variety Tioga during storage . Three dose levels of 100 , 200 , and 300 Krad were tested and the storage temperature was 4 1•°0
Chemical changes, organoleptic qualities and spoilage rate were studied at regular intervals during storage
period •
The fallowing conclusions could be drawn ~
1- No detectable differences were found between irradiated and non-irradiated samples with regard to moisture content , total soluble solids , sugars contents , pH and volatile acidity . While the difference s observed,
afterworlds , during storage were a result of normal physiological and biochemical processes within the fruit as affected by prolongation of storage period induced by irradiation .
2- Ascorbic acid content was markedly reduced by irradiation immediately after treatment in both ripe and
mature fruits . The decrease of ascorbic acid in the
control samples during storage was most appreciable,
while the 200 Krad lot retained the highest percentage of the vitamin at the end of storage period .
3- Anthocyanin content of t he fruits was inversely proportional to the irradiation dose but the regeneration
the pigments observed during storage could compensate
for the loss of colour resulting by irradiation.
4- The carbonyl levels produced upon gamma irradiation
at doses employed were too low.
5- No radiation effect s Were observed on Peotin- methyl
lesterase activity during the first nine days of
storage, but the irradiated samples after-wards
exhibited a lower activity of the enzyme . the enzyme inactivation was proportional to irradiation
dose .
6- Irradiation at doses of 100 , 200 and 300 Krad effectively prolonged the shelf- life of strawberries stored at 4 + iDe by 2, 10 and 12 days respectively over the shellfire of the unirradiated control for fruits picked at the ripe stage • But for the fruits picked at mature stage the same dose levels of 100,200 and 300 Krad effectively extended the storage period by 4 , 12 , 16 days respectively .
7- The extendeal period of shelf - life gained over control
resulte1 in a decrease of the organoleptic properties of the irradiated lots , but the level of the sensory qualities was acceptable.