Mushrooms grown on mulch made from bay and eucalyptus leaves experience changes in flavour and, to a small degree, in colour, while those grown on bay leaves are better in quality. These are the results of a study carried out by Argentinean researchers, some of whom are working for the Public University of Navarre (UPNA). The objective is to make use of waste generated by the essential oils industry.
"A panel of experts has confirmed that the mushrooms we grew on bay leaf and eucalyptus mulch were more brown in colour, had a more 'mushroomy' taste and were more spongy than those grown in traditional ways," says Alejandra Omarini, lead author of the study and a researcher who has recently joined the UPNA's Genetics and Microbiology Research Group.
The aim of the study, which has been published this month in the International Journal of Food Science & Technology, was to evaluate use of waste products from the essential oils industry in producing edible mushrooms. Through their study, the scientists showed that bay and eucalyptus mulch change the sensory qualities -- i.e. the smell, taste and texture -- of the mushrooms.
As there is almost no information available on evaluation of the sensory qualities of edible mushrooms, the team set up a panel of experts to define and compare the attributes of two species -- Pleurutus ostreatus (oyster mushrooms) the second most commonly cultivated and eaten mushroom worldwide, and Polyporus tenuiculus, a wild edible mushroom that could potentially be produced on a commercial basis.
This group of experts showed for the first time that the sensory attributes of these two species "clearly" set them apart from others, seven if they are grown using traditional mulch. The experts felt that Polyporus tenuiculus scored more highly than Pleurutus ostreatus in terms of the intensity of its "cereal" taste, colour, firmness, fibrousness and sponginess, while the oyster mushroom had a unique acidic flavour and tang, according to the scientists.
Adding bay and eucalyptus
The researchers grew the mushrooms on mulch made from the residues left after extracting the essential oils from bay and eucalyptus leaves, as well as farming waste (wheat straw).
The bay leaf waste proved the best, since there was not only a good crop yield, but the mushrooms produced were of better quality, according to the panel of experts.
The verdict of the "expert judges" was that the mushrooms grown on eucalyptus and bay had a more intense brown colour, as well as an increase in their acidity, their characteristic "mushroomy" flavour and their sponginess, although the intensity of bitterness and firmness was lower.
The study was carried out by the Biotechnology Research Institute at the General San Martín National University (Argentina).
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