Microbiological quality, safety, mycotoxins and heavy metals levels in underprized Kalahari truffle, Termitomyces schimperi and Ganoderma mushroom species
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Date
2020
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Publisher
University of Namibia
Abstract
In many African countries, edible mushrooms are used as a source of food and income. In Namibia, Ganoderma mushrooms are barely utilised. Kalahari truffles and Termitomyces schimperi are the common harvested for domestic consumption and/or selling in the informal markets. Though truffles in western markets fetch very high prices, the cost of truffles in Namibia is barely reported. The microbial quality, safety and heavy metal level in the edible Namibian mushrooms is not known. This study investigated the cost of truffles at a select informal market in north-central Namibia and assessed the effect of washing and drying of truffles on the microbial quality, safety, mycotoxin and heavy metal levels. The microbial quality, safety, mycotoxin and heavy metal levels were also determined in the Ganoderma and Termitomyces schimperi mushrooms collected from the wild. Microbial analyses were carried out using culture techniques. Mycotoxin analysis was carried out using ELISA kits. Heavy metal analysis was done using the ICP-OES. The price of Kalahari truffle ranged from N$ 29 to N$ 71 per kg. Truffles in Namibia are underpriced than in developed nations and has no objective price consistent with a unit mass. Generally, all mushrooms samples had total aerobic counts that are mostly within the acceptable total aerobic count limit of <5.7 log cfu/g. No yeast and Salmonella detected in Ganoderma samples. The levels of fumonisin B1 (17.4 to 142.1 µg/kg) in truffles irrespective of washing were within the permissible limits (200-300 µg/kg). The levels of all the analysed mycotoxins in Termitomyces schimperi were above the permissible limits. Nickel and mercury were not detected in truffles or Termitomyces schimperi. There is a need for appropriate processing to take place before consumption of majority of the studied mushrooms.
Description
A thesis submitted in fulfilment of the requirements for the Degree of Master of Science (Agriculture)
Keywords
Food and income, Ganoderma mushrooms, Termitomyces schimperi