Combined effect of gaseous ozone treatment and other food preservation methods on physicochemical characteristics and shelf life of fruits and vegetable (Doctoral thesis)

Πάνου, Ανδρέας

In the present study the combined effect of gaseous ozone treatment and other preservation food methods on physicochemical characteristics and shelf life of fruit and vegetables was investigated. The studied fruits and vegetables were: grape (cv. Sultanina), strawberry (cv. Camarosa), apricot (cv. Bebeko) and fresh-cut lettuce salad. Additionally, gamma irradiation and mild heat treatment were applied on strawberry and passive modified atmosphere packaging on bilayer film PET//LLDPE and citric acid were applied on fresh-cut lettuce salad. Weight loss, firmness, color parameters (L*, a* and b*), total soluble solids titreatable acidity, pH, volatile compounds, sensory characteristics (appearance, taste and odor) and microbiological indexes (Total mesophilic counts, Yeast and molds counts, Enterobacteriaceae counts, Lactobacillaceae counts and fungal decay) were monitored during cold storage of the commodities above. Ozone treatment at 0,5 ppm improved appearance, taste and odour and increase the shelf life of grapes by 7 days compared to untreated grapes. The application of higher ozone concentrations 1,0 and 1,5 ppm reduce shelf life of stored grapes accelerating the degradation of appearance, taste and odor. The higher shelf life of ozone-treated grapes at 0,5 ppm could be attribute on lower percentage weight loss compared to untreated grapes and on the inhibitory effect of ozone to the tissue-browning enzymes such as polyphenol oxidase, peroxidase and phenylalanine ammonolyase. Citric acid treatment, ozonation at 0,5 ppm and ozonation at 0,5 ppm plus citric acid improved significantly the visual appearance and cut-effect tissue browning index of lettuce compared to untreated ones. Total mesophilic counts and Enterobacteriaceae counts were also reduce significantly after the application of treatments above. Yeast and molds present higher resistance on these applied treatments. An increase by 4 days was achieved in shelf life of lettuces. The application of irradiation increase shelf life of strawberry by 2 days. Same results were observed after the application of blanching, ozonation at 0,5 ppm and ozonation at 0,5 ppm plus blanching. Higher doses of gamma irradiation and ozonation accelerate the degradation of appearance and taste compared to untreated strawberries. The applied ozone concentrations of 0,5, 1,0 and 1,5 ppm improved the appearance and taste of apricots compared to untreated ones. The best results were recorded on ozone treatment at 0,5 ppm. The extension of shelf life was 5 days. As far as concerned physicochemical characteristics, pH and total soluble solids were not affected significantly by the application of ozone treatment. Ozone at low concentrations increase the firmness of fruits compared to untreated ones, while increases the lightness on account of its blanching properties. Both ozonation and irradiation affect significantly titreatable acidity of fruits.
Institution and School/Department of submitter: Πανεπιστήμιο Ιωαννίνων. Σχολή Θετικών Επιστημών. Τμήμα Χημείας
Subject classification: Όζον
Keywords: Όζον,Φρούτα,Λαχανικά,Επεξεργασία,Ozone,Fruits,Vegetables,Treatment
Appears in Collections:Διδακτορικές Διατριβές

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