Byssochlamys B. fulva and Nivea, thermistors Ascomycetes: qualitative and quantitative culture and identification from canned
Byssochlamys fulva (Family Trichocomaceae) is a saprophyte fungus, initially described on earth (soil). His current interest is motivated by their involvement in the degradation of some heat - treated canned foods, being a fungus with heat - resistant elements sexual reproduction (ascospores). To survive the heat treatment to undergo some foods, packed foods can decompose containing pectins such as canned fruits or fruit juices packaged. Degradation is possible by releasing pectinolytic enzymes capable of decomposing fruit pectin. Furthermore, by generating carbon dioxide (CO 2) in their metabolism it causes a bulge of preserved. Currently, the reduction of preservatives in some packaged foods has contributed to the increase in its finding. The particularity of this fungus which has the heat resistance is the development of some forms of sexual reproduction (ascospores), which are heat resistant, even sometimes at temperatures as high as 85C.
The most important physiological characteristic of B. fulva for food mycology is the heat resistance of its ascosporas. Heat heat resistance varies type strains, the pH and the proportion of water (w) in the field where it is located, and the presence of preservatives. The ascospores are more sensitive to heat at low pH, and when there preservatives such as SO 2 (sulfites). The high concentration of sugars in the product, however, has a protective effect against heat. The second important physiological characteristic of B.fulva that facilitates the degradation in preserved products is their ability to grow with very low oxygen tensions. This feature is shared with B. nivea, and therefore both species have advantages over other heat - resistant fungi, in canned products, bottled or packaged in cartons. When found in very low oxygen concentrations, it develops anaerobically and produce CO 2, which accumulates in the container and can deform. A small oxygen in the air that can be found at the top of the container, bottle or tetrabrick amount, provide enough oxygen for their development. The third characteristic of these species is their ability to produce and release pectinolytic enzymes that cause the breakdown of solid fruit. During its growth, while the residual oxygen canned or bottled foods consumed, it produces pectinolytic enzymes that cause the first sign of fruit softening, which can progress to total disintegration of them. Moreover, these species can produce some carcinogenic toxic secondary metabolites (mycotoxins) and patulin considered, produced by both species Byssochlamys (fulva B. nivea and B.). They can also release bisoclamina A, bisoclámico acid and mycophenolic acid.
This fungus is teleomorphic form (sexual) of Paecylomyces fulvus (anamorphic form, asexual). As teleomorphic form (sexual) is included between the Ascomycetes due to the production of asci (asci), with ascospores therein when mature. These asci do not occur in any sexual fruiting body that protects (Gymnothecia, Cleisthotecia, perithecia, etc.), as with other Ascomycetes ascas but appear in clusters of white hyphae surrounded without any special structure, but only forming a framework. The anamorphic form, Paecylomyces fulvus, is very similar morphologically to Paecylomyces variotii, which can be confused with. Asexual conidia of the anamorph form are not heat - resistant, so they are destroyed during the heat treatment, while the heat - resistant ascospores persist.
The main reservoir of these fungi is soil and therefore more fruits ground contact, or dust, are more prone to contamination with them. For this reason, measures to remove it is recommended to avoid contact of the fruit with soil or dust during collection or transport, washing fruits, or filtration of fruit juice to remove these fungi. It is not advisable to increase the temperature during the preparation of cans because the quality of the packaged product is reduced, so should be prioritized control pollution from soil or dust.
The (asexual) anamorph form, which develops in the cultures from ascospores, conidiophores develops groups brush (penicilios) which appear on the surface of the hyphae, or the end of long chain hyphae. Conidiogenous cells are phialides, long neck, with tapered ends 12 to 20 microns long. The conidia are generally cylindrical or barrel shaped (doliiformes) generally narrow, 7a 10 microns long. Paemyclomyces fulvus (asexual form), it produces the same type of conidia, while morphologically similar species, Paecylomyces variotii, produces ellipsoidal and not cylindrical conidia, and lacks the teleomorphic form (sexual), so it is not isolated from the heat - treated foods.
Tests in IVAMI:
- Qualitative and quantitative culture and identification.
- Preserved with suspected impaired by pectinolytic enzymes.
Preservation and shipment of sample:
- No special requirements.
- Cultivation and identification: 2 to 3 weeks depending on the development of the fungus.
Cost of the test: