Title page for ETD etd-12152011-145312


Document Type Master's Dissertation
Author Van Jaarsveld, Louis Pieter
Email lpjaars@gmail.com
URN etd-12152011-145312
Document Title Chemical, physical and microbial properties of casing materials used in the commercial production of white button mushrooms [Agaricus bisporus (Lange)]
Degree MSc
Department Microbiology and Plant Pathology
Supervisor
Advisor Name Title
Prof L korsten Supervisor
Keywords
  • casing materials
  • characteristics
  • chemical and microbial properties
  • physical
  • Agaricus bisporus
  • Chromelosporium fulvum
  • heat capacities
  • phenols
Date 2011-09-09
Availability restricted
Abstract
Agaricus bisporus (Lange) Sing (white button mushroom), is the most common cultivated mushroom in South Africa and many other places in the world. Agaricus bisporus was first cultivated on a commercial scale in South Africa in 1940. Since then, approximately 35 commercial mushroom growing facilities have been established. These farms produce about 20 000 tons per annum. Peat is commonly used as casing material for mushroom production in South Africa. Natural indigenous peat sources are limited and expensive. Due to governmental legislation to prevent and restrict depletion of wetlands, mining thereof has been discontinued since 2006. Mushroom farmers were therefore forced to either use a local alternative waste product or imported peat. South African peat was previously pasteurised to eliminate pests and diseases. This treatment often resulted in the growth of Chromelosporium fulvum (Link) McGinty (C. fulvum) particularly when alternative casing materials such as wattle bark was used. Although the mushroom itself is not affected; this mould can significantly affect button mushroom production. A micro-mushroom growing unit was build and designed to evaluate the effect of C. fulvum on A. bisporus mycelium growth as well as to determine the yield of several casing materials due to pasteurisation.

The function of a casing material is well known and the physical and chemical parameters defined. Assessment of the influence of heat on these properties permits a broad estimation of the requirements needed for a suitable casing medium in order to produce mushrooms in a sustainable manner. This information can also provide some insight why weed moulds proliferate after pasteurization. In addition, the effect of heat on the total soluble phenols content may explain the growth of C. fulvum on certain materials. This investigation suggests that C. fulvum grows and sporulate at different rates on different casing materials. The presence of C. fulvum on pasteurized and unpasteurized casing materials affect the growth of A. bisporus mycelium as well as the time of the 1st flush formation.

This study therefore provides some insight into the various parameters that can be used to profile an ideal casing media and the value of the system to predict whether a particular material has the potential to be used as an alternative to peat. An alternative to South African peat need to be found, however, partial substitution of peat with other materials is more promising than complete replacement. This was the first study that investigated specific heat capacities of casing materials, the effects of heat on the chemical properties as well as the use of a micro-mushroom unit to see the interaction of C. fulvum on A. bisporus. The determination of the sporulation rate of C. fulvum on several materials and mixes was a newly tested method to describe the preferred incidence of C. fulvum on certain materials.

2010, University of Pretoria. All rights reserved. The copyright in this work vests in the University of Pretoria. No part of this work may be reproduced or transmitted in any form or by any means, without the prior written permission of the University of Pretoria.

Please cite as follows:

Van Jaarsveld, LP 2010, Chemical, physical and microbial properties of casing materials used in the commercial production of white button mushrooms [Agaricus bisporus (Lange)] , MSc(Agric) dissertation, University of Pretoria, Pretoria, viewed yymmdd < http://upetd.up.ac.za/thesis/available/etd-12152011-145312 / >

E11/9/9/197/gm

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