Effects of gamma irradiation and hot water treatment on the shelf of mango (Mangifera indica L.) var. RAD

Mature green mango fruits of Rad variety were treated with gamma radiation doses of 0.3, 0.6, and 1 kGy with and without hot water treatment and subsequently stored at 15 deg C, RH 89 %. The effects of different treatments on shelf life, physico-chemical properties and organoleptic properties were studied. The results indicated that irradiation with or without hot water treatment delayed color development and extended the shelf life but hot water treatment had no effect on color but did reduce the anthracnose. Irradiation injury increased with increasing dose and storage period. Hot water treated samples showed uniform ripening but without hot water had uneven ripening. Weight loss increased with increasing dose. Firmness, titrable acidity, and vitamin C decreased whereas total soluble solids and pH increased with storage period. Sensory evaluation showed no significant difference in quality attributes between treated and untreated samples upto 0.6 kGy. Mango samples dosed at 0.3, 0.6, and 1 kGy without hot dip extended the shelf life by 8, 12, and 18 days, respectively, as compared to control while mango samples treated with hot water and irradiated at doses 0.3, 0.6, and 1 kGy extended the shelf life by 4, 7, and 14 days, respectively, as compared to hot dip control. The actual cost for irradiation based on a source strength of 280 kCi was Baht 0.90 per kg. Including all the variable cost and storage cost for 26 days, per kg irradiation cost for 0.6 kGy hot dip irradiated sample was Baht 8.80 and net benefit was 29 %. The results indicated that ionizing radiation combined with hot water treatment (55 deg C for 5 min) not only reduced the storage decay but also extended the shelf life by 10 days. Considering the rottening approximately 10 %, samples irradiated at dose 0.6 kGy with hot dip treatment showed best results with 8.3 % rottening and no irradiation injury to pulp after 26 days of storage. However, under similar condition rottening was less in hot dip 1 kGy samples but quality was impaired due to browning of pulp.