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Chitinous material was extracted from mycelia of Aspergillus niger and Mucor rouxii grown in yeast peptone dextrose broth for 15 and 21 days, respectively. The extracted material was characterized for purity, degree of acetylation, and crystallinity and tested for antibacterial and eliciting properties. The maximum glucosamine level determined in the mycelium of A. niger was 11.10% dw and in the mycelium of M. rouxii was 20.13% dw. On the basis of the stepwise extraction of freeze-dried mycelia, it appeared that M. rouxii mycelia contained both chitin and chitosan, whereas A. niger contained only chitin. The yields of crude chitin from A. niger and M. rouxii were 24.01 and 13.25%, respectively, and the yield of chitosan from M. rouxii was 12.49%. Significant amounts (7.42-39.81%) of glucan were associated with chitinous compounds from both species and could not be eliminated by the extraction method used. The degrees of acetylation were determined to be 76.53 and 50.07% for chitin from A. niger and M. rouxii, respectively, and 19.5% for M. rouxii chitosan. The crystallinity of fungal chitin and chitosan was estimated to be less intense than in corresponding materials from shrimp shells. The extracted chitin and chitosan in a concentration of 0.1% reduced Salmonella Typhimurium DT104 2576 counts by 0.5-1.5 logs during a 4 day incubation in tryptic soy broth at 25 ° C. Furthermore, all tested chitinous materials from fungal sources significantly reduced lesions caused by Botrytis cinerea and Penicillium expansum in harvested apples.

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Accumulation of chitinous material in Agaricus bisporus stalks was determined during postharvest storage at 4 and 25 °C. The chitinous material was extracted after alkali treatment and acid reflux of alkali insoluble material and analyzed for yield, purity, degree of acetylation (DA), and crystallinity. The total glucosamine content in mushroom stalks increased from 7.14% dry weight (DW) at harvest (day 0) to 11.00% DW and 19.02% DW after 15 days of storage at 4 °C and 5 days of storage at 25 °C, respectively. The yield of crude chitin isolated from stalks stored at 25 °C for 5 days was 27.00% DW and consisted of 46.08% glucosamine and 20.94% neutral polysaccharides. The DA of fungal chitin was from 75.8 to 87.6%, which is similar to commercially available crustacean chitin. The yield of crude fungal chitin of 0.65−1.15% on a fresh basis indicates the potential for the utilization of these mushroom byproducts.

http://www3.interscience.wiley.com/cgi-bin/fulltext/118832478/PDFSTART

Pasteurized mushrooms had firmer texture and lighter color compared with those that were retorted. Addition of acid and retorting temperature resulted in extensive softening of mushrooms and solubilization of proteins and polysaccharides that diffused into brine. Total chitin was not affected by applied treatments and did not appear to be related to texture alteration of processed mushrooms. Extensive solubilization caused by acidification and retortion resulted in reduction of cell diameter and enlarged intercellular space within the cap tissue. Mild acidification of sterilized samples reduced discoloration compared with the control, but further acidification resulted in considerable darkening. In contrast, tissue and color of pasteurized mushrooms seemed to be unaffected.

http://www3.interscience.wiley.com/cgi-bin/fulltext/119036124/PDFSTART

The objective of this study was to determine ultrastructural and compositional changes in fresh mushrooms associated with adverse changes in texture during 9 d of post-harvest storage at 12 °C. Mushroom softening (2.6N to 1.5N, puncturing force) was consistent with toughening (19.2N to 33.0N, gumminess). Protein and total carbohydrate content declined, but chitin content increased during mushroom storage. Most polysaccharides were extracted after deacetylation and depolymerization of chitin, indicating that structural glucans were mainly bound with acetylglucosamine polymers. Softening paralleled expansion of intercellular space at the pilei surface, hyphae shrinkage, central vacuole disruption, and loss of proteins (r = 0.94) and polysaccharides (r = 0.84), while toughening was associated with increased chitin content (r = 0.95).