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Understanding the effects of high-pressure, high-temperature processing on the key quality parameters of green beans (Phaseolus vulgaris) with a view to assessing the potential quality benefits of the approach relative to conventional thermal processing.

Leadley, Craig Edward (2012)
Ph.D. thesis, University of Birmingham.

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Abstract

Studies were conducted to explore whether high pressure (up to 700 MPa) could be used in combination with elevated temperatures (up to 90°C initial temperature) to produce ambient stable green beans (Phaseolus vulgaris) with improved quality compared with conventionally heat processed samples. Colour changes, texture change and chlorophyll retention were explored at a range of pressures, temperatures and times using a surface response methodology. Texture changes were essentially related to temperature effects; higher temperatures resulted in a greater loss in texture. Significant improvements in texture retention were possible using High Pressure Sterilisation (HPS) but sample colour was negatively affected. Colour parameters were predicted primarily by time and pressure so deterioration in green vegetable quality for a commercially sterile products appears inevitable when using HPS. The use of ohmic heating as a pre-heating method greatly reduced cook values (T\(_{ref}\) = 100°C, z = 39C°) for colour degradation (down to 0.24, 0.12, 0.35 from 3.02, 2.50, 3.70 minutes for ohmically heating and water bath heated samples respectively) which yielded significant benefits in terms of colour retention of raw materials at the start of the HPS cycle; values of a* and b* for ohmically pre-heated samples were close to that of blanched beans.

Type of Work:Ph.D. thesis.
Supervisor(s):Fryer, Peter
School/Faculty:Colleges (2008 onwards) > College of Engineering & Physical Sciences
Department:Department of Chemical Engineering
Subjects:QD Chemistry
TP Chemical technology
TS Manufactures
Institution:University of Birmingham
ID Code:3333
This unpublished thesis/dissertation is copyright of the author and/or third parties. The intellectual property rights of the author or third parties in respect of this work are as defined by The Copyright Designs and Patents Act 1988 or as modified by any successor legislation. Any use made of information contained in this thesis/dissertation must be in accordance with that legislation and must be properly acknowledged. Further distribution or reproduction in any format is prohibited without the permission of the copyright holder.
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