EFFECT OF GAMMA RAY IRRADIATION AND FRYING ON THE THIAMINE CONTENT OF BACON

The effects of ionizing irradiation and frying on the thiamine and riboflavin content of bacon were determined. Significant destruction of thiamine but not riboflavin occurred during both the irradiation and frying. The destruction of thiamine was found to be directly related to the dose of ionizing radiation or the degree of cooking. Frying before irradiation, reduction of water content by lyophilization, and irradiation at - 40°C rather than 2°C produced significantly greater retention of thiamine. Frying the bacon following irradiation produced radiation dose-related, nonadditive, increased destruction of thiamine. The protective effect of frying before irradiation was not directly linked with the reduction of moisture by frying.     

EFFECT OF GAMMA IRRADIATION ON THE POSTHARVEST PHYSIOLOGY OF FIVE BANANA VARIETIES GROWN IN INDIA

ABSTRACT— Gamma irradiation to 20–40 krad inhibits the ripening changes in preclimacteric bananas without affecting the fruit quality. Both fruit maturity at harvest and post-irradiation storage temperature markedly influence the response to irradiation. The optimum dose and the maximum tolerable dose varied among the five varieties screened. Ability of the banana fruit to withstand higher doses of gamma irradiation depends on the physiological status of the fruit at time of irradiation. Irrespective of varietal differences, irradiation of preclimacteric bananas to doses above 50 krad resulted in severe skin discoloration and fruit splitting. Irradiation under anoxia did not markedly reduce the radiation injury, suggesting that factors other than ozone formed during irradiation in air may contribute the radiation damage. Fruits on the climacteric could tolerate up to 200 krad but no effect on ripening rate was observed. Ethylene or 2,4-D could reverse irradiation-induced inhibition of ripening in bananas. Irradiation seems to decrease the sensitivity of banana fruit to the ripening action of exogenously added ethylene.     

EFFECT OF GAMMA IRRADIATION ON SOFTENING CHANGES AND ENZYME ACTIVITIES DURING RIPENING OF PAPAYA FRUIT

The aim of this work was to study the role of cell wall and ethylene related enzymes to papaya fruit firmness. Irradiation treatment was used as an imposed stress to cause changes in firmness. Physiologically mature papaya fruits were irradiated (500 Gy) and allowed to ripen at 22C and 90% RH. Polygalacturo‐nase (PG), pectinmethylesterase (PME), βgalactosidase, cellulose and 1‐aminocyclopropane‐1‐carboxylate oxidase (ACC‐oxidase) activities were followed during ripening and correlated to changes in firmness, skin and pulp color, respiration and ethylene production. The firmness of irradiated fruits was retained at least 2 days longer than in normal fruits and also had a slower rate of softening. Total soluble solids (d?Brix), cellulase activity and ethylene production were not altered by irradiation treatment. The activity patterns of PG, PME and β‐galactosidase were related to pulp softening and affected by irradiation. ACC‐oxidase activity was influenced by irradiation treatment, but its changes were not temporally related to those in firmness. It was concluded that irradiation had no direct effect on firmness but it acted by altering the ripening induced synthesis of cell wall enzymes, mainly PME.     

EFFECT OF IRRADIATION ON THE MALTING QUALITY OF BARLEY

Two six-row barley cultivars, DL 70 and C 164 were subjected to Co⁶⁰ gamma irradiation in the range of 0 to 250 Krad and malted with and without gibberellic acid treatment. Barley irradiated with doses up to 75 Krad produced normal malts when compared to the controls. Irradiation doses of 125 and 250 Krad significantly increased the malt yields but considerably decreased the α-amylase activity. Gibberellic acid significantly increased the enzyme activity and degree of modification of the irradiated and the control malts.     

EFFECT OF GAMMA IRRADIATION ON THE LIPID PEROXIDATION IN CHICKEN, LAMB AND BUFFALO MEAT DURING CHILLED STORAGE

Chicken, lamb and buffalo meat were subjected to low-dose gamma irradiation (2.5 kGy) and stored at 0–3C. Lipid peroxidation in terms of thiobarbituric acid (TBA) number and carbonyl content were monitored during storage. While irradiated meat showed slight increase in TBA number and carbonyl content on storage as compared to nonirradiated meat, this did not affect the sensory qualities of meat. Free fatty acid content decreased markedly on irradiation. Irradiated meats were microbiologically safe and sensorily acceptable up to 4 weeks in the nonfrozen state (0–3C) while nonirradiated meat had a shelf-life of less than 2 weeks .     

EFFECT OF GAMMA IRRADIATION ON SOME CHARACTERISTICS OF SHELL EGGS AND MAYONNAISE PREPARED FROM IRRADIATED EGGS

Shell eggs were irradiated at doses of 0.0, 0.5, 1.0 and 1.5 kGy of gamma irradiation. Immediately after irradiation, bacterial, physical and chemical analyses of eggs and sensory evaluation of the mayonnaise prepared from irradiated egg yolk were performed. Results indicated that all doses of gamma irradiation reduced the total counts of mesophilic bacteria and total coliforms of eggs. The radiation dose required to reduce the Salmonella load one log cycle (D₁₀) in eggs was 448 Gy. Eggs irradiated with 1.5 kGy may be suitable microbiologically to prepare safe mayonnaise. There were no significant differences in saturated fatty acids (C14:0; C16:0; C18:0) and thiobarbituric acidvalues between the yolk lipid extracted from irradiated eggs and that of nonirradiated ones. Gamma irradiation reduced the viscosity of egg whites. Sensory evaluation showed no significant differences between mayonnaises prepared from irradiated and nonirradiated egg yolks.     

EFFECT OF GAMMA IRRADIATION ON ISOMERIZATION OF β-CAROTENE IN SWEET POTATO1

Cured Georgia Reds, sweet potato roots, were irradiated using ⁶⁰Co source for 500 Krad dose. HPLC analyses of tissue extracts indicated that irradiation did not lead to isomerization of all-trans-β-carotene. Greater than 97% of the total β-carotene was in the all-trans form. Cis isomers of β-carotene have lower provitamin A activities than all-trans-β-carotene. Since they were not produced with γ-irradiation, this process did not decrease provitamin A due to isomerization. Thus, irradiation of sweet potatoes can be used without significant changes in the provitamin A content.     

EFFECTS OF GAMMA IRRADIATION OF BARLEY AND MALT ON MALTING QUALITY

Two two-rowed barley cultivars, Tokak and Clerine, were irradiated at two different dose ranges (0.05–0.75 kGy and 0.5–5.0 kGy) using a ⁶⁰Co source. Irradiation of barley at the medium levels before malting had detrimental effects on most of the malt quality criteria. The detrimental effects of irradiation was lower at doses up to 0.25 kGy. Irradiation of malt samples caused either slight or no deterioration of quality characteristics .