Document Type

Theses, Masters

Rights

This item is available under a Creative Commons License for non-commercial use only

Disciplines

Microbiology

Publication Details

Successfully submitted for the award of Master of Philosophy (M.Phil) to the Dublin Institute of Technology in 2003.

Abstract

The central aim of this study was to optimise the processing and storage of selected vegetable within the parameters of extended shelf life, time/temperature relationships and sensory quality. The vegetables were selected on the basis of the results of a survey of the Irish vegetable industry. The current literature in the field of modified atmosphere packaging (MAP) and the Irish vegetable industry was reviewed. The current state and future requirements of the Irish vegetable industry was investigated through the use of a questionnaire. This established the views of Irish vegetable purchasers (food service, fast food and retail outlets), in relation to vegetables currently purchased. It emerged that retail outlets are ultimately governed by consumer purchasing trends. Retailers purchase the widest selection of vegetables of all sectors in a variety of packaging formats. The purchasing patterns of food service outlets are strongly governed by seasonality and quality. These outlets continue to perform processing operations on site, as opposed to purchasing ready prepared samples. While retailers are interested in prolonged vegetable shelf life at an extra cost, food service outlets are constrained by budgets within their business. The questionnaire highlighted that the packaged vegetables most frequently purchased by retailers and food service outlets were broccoli, carrots, lettuce, onions, peppers and potatoes. These vegetables that were selected for modified atmosphere packaging and sensory analysis were carrot, pepper, broccoli and cauliflower. The second phase of this research involved MA packaging of these selected vegetable to generate the ideal packaging conditions to prolong their shelf life. Storage temperatures and gas atmosphere were varied for each vegetable packaged. Changes occurring in product quality over time were investigated for both raw and cooked vegetable products and analysed by a trained taste panel. Products were scored for individual quality attributes (surface moisture, colour, flavour and texture). It was concluded that higher temperatures accelerated the deterioration of sensory attributes in carrot and celery. Extended shelf life of 10 days for carrots and peppers and 7 days for celery is achievable through strict temperature control combined with passive packaging. Superior quality was observed for pepper, and mixes involving pepper in packages store at 8°C for up to 10 days. Storage temperature was found to have a greater influence on quality of carrot, celery and pepper than storage atmosphere. It was apparent that broccoli and cauliflower require an active atmosphere to optimise quality attributes for up to 7 days at either 4 or 8°C. It was found that deterioration of several sensory attributes that were detected in the raw product were not detected in the corresponding cooked product. This reveals that passive packaging would be sufficient to reduce quality deterioration of these vegetables for use as part of a cooked dish. Further research in the area of MAP is recommended to focus on the requirements of food service outlets and in outlining the benefits of use of MA packaged vegetables in increasing productivity and reducing costs within the food service business. A microbiological profile of the packaged vegetables over time is also recommended to identify the point at which it is unsafe to consume MA packaged vegetables due to microbiological risk.

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