| In this thesis, the efficacy of some treatments to preserve fresh fruits and vegetables isstudied by determining the shelf life from the physico-chemical characteristics andmicrobiological evaluation during storage. With this intent, green peppers (Capsicum annuumL.) were minimally processed (cut in slices) and were treated by means of chitosan coatingachieved by dipping and compressed noble gas using a compressing machine prior to storageat cold temperature (5C). The impact of the combined application of those treatments is alsoinvestigated.In order to report the characteristics of the raw peppers, different type of peppers fruitswere compared to each other. Initially, the fresh green peppers that will be used for this studywere evaluated, and a sensory vocabulary for fresh green peppers was described accordinglyto be used for application in the shelf life study. Besides, to detect main problems associatedwith cut peppers, fresh samples were evaluated without any treatments and it was observedthat sensory characteristics degraded with increasing storage temperature and time conditions.The results from proximate analysis showed that the present raw materials characteristicswere in range of those previously reported in other studies.In order to improve the storability of cut green peppers during cold storage, the effectof various chitosan concentrations (0%,0.5%,1.0%and2%(w/v) chitosan) on some physico-chemical and microbial characteristics of the slices was subsequently analyzed. The dataindicated that the results from chitosan treated samples were better than that of control free ofchitosan. The decrease of surface lightness was delayed by chitosan treatments; and thesurface green colour was kept under marginal changes compared to control. On the other hand,a greater reduction of fungal incidence, carbon dioxide concentration, and electrolyte leakageof the chitosan treated samples was chitosan concentration-dependant. Microbiologicalevaluation revealed that total viable cells count decreased with increasing chitosanconcentration that was well correlated with the sensorial characteristics. In this study, delayedchanges were significantly chitosan concentration dependent and observed changes were tothe least extent in the2%chitosan.To evaluate the effect of compressed noble gas, the cut green peppers were alsoprocessed with the compressed argon gas (CAG) by means of pressure/time combinationsranging from0to8MPa for30and60min. CAG treatments retarded visible fungal growthduring15days and delayed overall changes compared to control, while between treatments,CAG at2MPa (30and60min) presented the best appearance. CAG treatments did notsignificantly physical properties during storage period. If CAG at2MPA (30and60min)efficiently delayed weight loss and total chlorophyll degradation, treatments at4and8MPa (30and/or60min) however promoted adverse effects by accelerating loss. Results suggestedthat CAG treatment at lower pressure applied effectively delayed deterioration, and worthfurther consideration in quality preservation.An application of a mixture of noble gas was performed in order to determine theeffect of the gases on the cut peppers quality attributes. When the samples were treated withmixed argon-krypton (MG) and argon (AG) treatments, weight loss and cell membranepermeability were found to be the lowest in MG samples. Besides, lower CO2concentrationand vitamin C loss were detected in gas treated samples compared to untreated samples(control). Moderate rate of PPO activity and total phenol degradation were also effectivelyreduced. The minimum changes of quality observed in cut peppers resulted from both mixedand gas treatment alone.In order to examine the impact of a combined technique by a treatment of compressedgas and chitosan coating (NGCS), those respective treatments were sequentially applied. Theresults showed that NGCS improved preservation of FCGP compared to control. It wasobserved that NGCS enhanced surface lightness in contrast to single CNG and CS treatments.Intensity of visual changes was with less extent in NGCS than in single CNG treatment.Moreover, coated samples presented the smallest changes in firmness and green colour andchlorophyll content was the least affected with chitosan coating treatment. |
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