Effects of different applications on quality of some minimally processed (fresh - cut) vegetables


Thesis Type: Doctorate

Institution Of The Thesis: Bursa Uludağ University, ZİRAAT FAKÜLTESİ, GIDA MÜHENDİSLİĞİ, Turkey

Approval Date: 2009

Thesis Language: Turkish

Student: BİGE İNCEDAYI

Supervisor: Ömer Utku Çopur

Abstract:

In this research, pumpkin, celery and potato were minimally processed and stored after modified atmosphere packaging. The vegetables were treated with NaCl, Na ? metabisulphite and chlorinated, and then rinsed with tap water. After this process, a part of vegetables were treated with citric acid and the other part with L ? cysteine. They were packaged with biaxially oriented polypropylene (BOPP) film and polypropylene (PP) plate under two different modified atmosphere conditions after centrifugation. Effects of all applications and optimum processing parameters were determined.During the storage period, ascorbic acid, total phenolics and total carotenoids content were decreased. More reductions were occurred in blank samples which were not treated with any chemicals. Ascorbic acid, total phenolics and total carotenoids were respectively determined as 2.23 - 7.09 mg / 100 g, 232.93 - 490.74 mg GAE /100 g, 99.37 - 251.93 mg / kg for pumpkin; 4.59 - 8.08 mg / 100 g, 346.08 - 497.04 mg GAE / 100 g, 11.77 - 51.70 mg / kg for celery and 2.67 - 8.38 mg / 100 g, 165.36 - 283.81 mg GAE / 100 g, 25.26 - 64.21 mg / kg for potato. Generally, a positive correlation was found between total phenolics and antioxidant activity and the ratios of antioxidant activity were changed between 22.39 - 44.09 % for pumpkin; 55.84 - 93.03 % for celery and 13.38 - 25.04 % for potato.Browning was an important problem for minimally processed celery and potato and could be prevented approximately for two weeks by chemical applications. During the storage period, there was a significant difference (p <0.01) between polyphenoloxidase activities of the samples which were changed between 826.77 - 4867.63 U / g for celery and 549.86 - 6931.03 U / g for potato.Weight losses of pumpkin, celery and potato occurred by the respiration during the storage were measured as 0.03 - 0.13 %, 0.18 - 0.32 %, 0.01 - 0.04 % respectively. This loses in the samples packaged with only nitrogen gas was higher than the samples packaged with both carbon dioxide and nitrogen.Slight changes were observed in the total dry matter and total acidity values of minimally processed vegetables; but a significant difference was found statistically for these parameters (p<0.01).In blank samples, total aerobic and mesophilic bacteria counts increased after a short time and these samples were lost their consumption quality by the increase of coliform bacteria counts also. Furthermore, the microbiological quality of the vegetables was preserved for two weeks with the citric acid application.When the results of sensory analysis were evaluated it was concluded that L ? cysteine application was rejected by the panelists by 95 % probability because of its unliked odor. But at the same time, this application was prevented enzymatic browning of the celery and potato and provided preference in terms of their color and appearance. Because of so slight texture differences in the samples, they were not distinguished by the panelists.