Influence of gamma irradiation and edible coating on shelf life of peeled garlic stored at different conditions

This study aimed to extend shelf-life of peeled Taşköprü garlic and the effects of edible film coating, irradiation and packaging with different gas compositions on the shelf-life of the samples were investigated. For this purpose, the samples were coated with film solutions, prepared with milk protein and zein. The coated samples were irridiated at 3 different doses (20, 40 and 80 Gy) and stored at 15 °C for 45 days. Weight loss, TSSC (Total soluble solids content), color, hardness, total sugar content, pyruvic acid, allicin content and aroma analyses were performed at 0 th, 3rd, 6th, 10th, 15th, 30th and 45th days of storage. The effect of the gas composition within the package was studied independently from coating process and garlics were packaged at atmospheric composition, under vacuum, 5 % CO2, 15 % CO2, 25 % CO2 than stored for 30 days at 15 °C . Weight loss, TSSC (Total soluble solids content), color, texture, total sugar content, pyruvic acid, allicin content and aroma analyses were performed 0., 3rd, 6th, 10th, 15th and 30th days of storage. In addition, the garlics packaged in same conditions and irradiated at 80 Gy were also stored and the effects of irridiation were investigated by carrying out the same analyses during storage. Research results showed that both milk protein and zein-based edible film coatings decreased the weight loss of garlic compared to the control samples during storage. The most predominant effect on weight loss was irradiation, after 45 days of storage the weight loss was determined as 27.27 % in control samples while it was determined as 21.47 %, 21.73 % and 19.55 % for the samples irradiated by 20, 40 and 80 Gy, respectively. The weight loss was changed between 3.00-4.13 % for packaged samples and the gas composition did not significantly effect on weight loss. Similar to weight loss, the gas composition alteration did not significantly effect on TSS content. The coating application and irridiation showed significant effect on the TSS contents of the samples. The control sample's TSS content was determined 43.65 °Bx at the end of storage while the samples irradiated with 80 Gy had 38.05 °Bx and it was almost unchanged from the beginning of storage. The coating application and irradiation was found to have positive effects on the hardness of garlic and at the end of 45 days of storage, control samples, 80 Gy irradiated samples, zein based film coated samples, milk protein based film coated samples hardness values were 4.40, 8.26, 6.87, and 6.37 kg, respectively. At the end of storage, the sugar content losses were determined as 36.80 %, 19.90 % and 19.50 % for control, zein and milk protein based film coated samples, respectively. It was found that control samples showed nearly two fold sugar losses compared to zein iv and milk protein based film coated samples. The sugar losses at the end of 30 days of storage were also determined for the samples packaged with different gas compositions. The garlics packaged at atmospheric composition; under vacum; 5 % CO2; 15 % CO2; 25 % CO2 were showed 16 % ; 4 %; 7 %; 11 % and 17 % sugar losses at the end of storage. Allicin content was found to be decreased during storage in coated and irradiated samples. This decrease was occurred less in the samples which were uncoated and 40 Gy irradiated and the samples coated with milk protein-based film. Allicin content was nearly not changed after 15 days of storage in the packaged samples with different gas compositions and it was found to be decrased averagely 40 % after 30 days of storage. The pyruvic acid contents in garlics were increased with storage. Aroma analysis results showed that flavor release during the storage period can be reduced by the coating application without applying irradiation. However, irradiation can be applied to prevent germination problems of garlics. The irradiation at 40 Gy in garlic covered with zein-based and 80 Gy in garlic covered with milk protein-based films were found to give better results for protecting the flavor compounds. The aroma profiles were not significantly changed in the garlics packaged with different gas compositions, but the garlic which were packaged at atmospheric composition and under vacuum, showed a better aroma profile than the others. When the results of the study analyzed overall, coated and irradiated garlics was found to be acceptable to the consumers for 30 days at 15oC, the garlics which were coated with polyethylene-polyamide mixed films were acceptable and could be stored without too many variations in terms of quality characteristics for 15 days. It was also thought that storage time could be extended by means of using these applications in combinations.