Brij Bhushan

Potential application of low dose gamma irradiation to improve the microbiological safety of fresh coriander leaves

Abstract A local market survey of fresh, raw coriander leaves, which is a component of many ready-to-eat, Indian dishes showed large variation in their bacterial load (7.0×106–1.36×108 cfu/gm) and mold and fungi (3.0×103–1.0×104 cfu/gm) and presence of potentially pathogenic bacteria such as faecal coliforms, Listeria and Yersinia. Conventional chlorination treatment affected the structural integrity of leaves leading to enhancement of rotting. Exposure to a low dose of 1 kGy was efficient for bacterial decontamination and elimination of potential pathogens without affecting the keeping quality of coriander leaves upto two weeks storage at 8–10 °C, measured visually in terms of degree of yellowing and rotting. Irradiation at higher doses led to the increased rotting during storage. The total chlorophyll contents as well its components, chlorophyll a and b did not change significantly on irradiation and subsequent storage. Similarly, the total carotenoid levels remained unaffected by exposure to 1 kGy dose, however, a dose dependent enhancement in their extractability was observed in irradiated leaves. No qualitative differences were observed in the GLC profile of volatile oils of control and irradiated (1 kGy) samples. There were no significant quantitative changes in the constituents of the major aroma compounds obtained from these two samples. Effects of irradiation on storage of the seasoning were also assessed.

Quality of apples following gamma irradiation and cold storage

The physico-chemical and organoleptic quality changes in apple cvs ‘Golden Delicious’, ‘Royal Delicious’, ‘Red Delicious’ and ‘Rich-A-Red’ exposed to gamma radiation doses of 0.1, 0.2, 0.4 and 0.6 kGy for quarantine and preservation purposes, were studied up to 6 months of storage at 2–4°C. Among the four cvs, ‘Rich-A-Red’ treated with 0.1 kGy dose showed better retention of sensory attributes and minimal changes in texture, total soluble solids, acidity and vitamin C content during storage. Results indicate that irradiation has commercial potential for apples as an alternative quarantine treatment for export requirements.

Improvement of shelf-life and microbiological quality of minimally processed refrigerated capsicum by gamma irradiation.

Shelf-life, microbiological and chemical quality of minimally processed capsicum subjected to radiation doses of 1, 2 and 3 kGy followed by storage at 5°C and 10°C were evaluated. Irradiation at an optimal dose of 2 kGy reduced the initial bacterial population by 2–3 log cycles and eliminated the coliforms Listeria and Yersinia. Chemical analysis revealed that the initial contents of ascorbic acid (127.7 mg/100 g), carotenoid (110 μg/100 g) and chlorophyll (7.75 mg/g) were reduced marginally by 5–10% with increasing radiation dose. However, during subsequent storage, up to 4 weeks, the temperature-dependent losses in vitamin C and chlorophyll content of irradiated samples were less compared with non-irradiated samples. The total carotenoid content of capsicum irradiated and stored for up to 2 weeks at 10°C showed a similar trend. Thus, gamma irradiation at 2 kGy was found to improve both the hygienic quality and shelf-life without affecting the nutritional quality of minimally processed capsicum.

Activity of radiation degradation products of vitamins A and E to haemolyse erythrocyte

Exposure of vitamin A acetate in freely dissolved state to γ-radiationin vitro caused a dose dependent degradation accompanied by the formation of new products. The radiation degradation products were separated by chromatography using step gradient elution. The parent molecule, vitamin A acetate, induced negligible haemolysis of erythrocytes. In contrast, the polar products formed by irradiation were found to be potent haemolysing agents. A highly polar product, eluted with methanol revealed maximum haemolytic activity. Acetylation of these products resulted in loss of their haemolytic properties. Similarly, vitamin E acetate, a known stabilizer of the biomembranes, after irradiation yielded products which caused haemolysis of erythrocytes. It was demonstrated that irradiation introduces hydroxyl groups which impart haemolytic properties to the radiation degradation products of vitamin A