Thamnidium spp. (T. elegans and T. chaetocladioides): interest for aged meats. Detection by culture and morphological identification and / or molecular.  

Information 03/02/16.  

Thamnidium spp. (T. elegans and T. chaeocladioides) (Kingdom Fungi, Division Zygomycota, Class Zygomycetes, Mucorales, Mucoraceae family) is a filamentous fungus characterized by asexually propagated by sporangia at the ends of sporangiophores and sporangia which unlike other Mucorales have columela. Thamnidium elegans, the most important species, generates ramaficaciones side of esporangióforo esporangiolos leading to smaller, with a more resistant and persistent wall containing few sporangiospores. These fungi are found in soil and preserved meats. Like other Zygomycetes, Thamnidium spp. It has sexual reproduction generated by metangial zygospores conjugation and formation of dark pigment. This fungus is a producer of large amounts of linolenic acid.

The aging of meat can be done in two ways: 1) wet method, and 2) dry method. Dry aging of the meat has been for centuries a form of conservation and soften the meat by butchers. Until about 50 years ago, it was customary dry aging. Subsequently, vacuum packed, together with improved processing and transportation of meat, made lost aging dry, keeping only a small number of meat suppliers.

When meats are aged by the wet method are placed in closed containers under vacuum and stored in controlled environments for a while. The method of dry aging is carried hanging carcasses of animals (channels) or open exploded unpackaged, cold room , where they remain for several weeks to months under conditions of temperature, relative humidity and controlled ventilation.

It has now increased interest in aging dry by a large number of wholesale and retail meat suppliers in the US, Australia and Southeast Asian countries (Korea, Japan, Singapore, Taiwan and Hong Kong). This type of aging is interested today for a market sector that appreciates this kind of meat for flavor and smoothness (soft flesh).

The purpose of dry aging is to find different flavors found only in them. During this process they are absorbed and concentrated juices of meat, digestion (cleavage) protein chemistry and fatty components resulting in a nutty flavor occurs, while the meat is tenderized by digestion proteins and connective tissue of the muscle. This process has several drawbacks due to its cost, compared to other conventional processing methods because the meat contracts, part of it is lost through the necessary cuts before consumption, carries a risk of contamination, environmental conditions are required and space, requires a shelf and some special care. In addition, they can only undergo this process HOMOGENEOUS meat with fat distribution. For this reason, these meats are offered only in some special upscale restaurants which attract customers who appreciate and value.

During aging dry there is a restriction of bacterial growth, whereas the growth of beneficial filamentous fungi (molds), as Thamnidium spp promoted. Thamnidium development spp. it appears as pale gray stringy spots that develop on the fatty parts of aged meat. Thamnidium development releases proteases and collagenolytic enzymes that digest the muscle and connective tissues giving the results discussed soften and change their flavor. Thamnidium growth can begin within three weeks after the start of the aging process. Other Mucorales as Rhizopus spp. and Mucor spp. They can also develop, but provides no favorable characteristic aged meat.

From the microbiological point of view, dry aged meats should be tested for fungi and thus validate the process, detecting, if any, the presence of Thamnidium spp.

Parts can grow old dry for about 35 days without any negative effect on the taste and safety. During aging does not significantly increase the number of counts of aerobic bacteria, although it is superior to the controls unaged meats. This limitation of the development of bacterial flora can be due to inhibition of growth by surface drying as a reduction in water activity occurs. In addition, the storage temperature is low enough to delay its development.

Dry aged meat must be processed just before distributed for consumption, cutting and packing the cut pieces. In these condiones packaging has a shelf life 2 to 3 days. It should be monitored to check the count of Enterobacteriaceae and Escherichia coli so that it is within the permitted limits.

Tests den IVAMI:

  • Culture for qualitative seeding the surface of the workpiece.
  • Morphological identification of growth of filamentous fungi (mold).
  • Molecular identification of the species of filamentous fungus (mold) cultivated.

Recommended types of samples:

  • Piece cut surface with visible growth, preferable molds with fat (100 g portion).

Shipping and storage conditions:

  • Refrigerated for less than 2 days and sent in cork white box pack (frigolín) frozen.

Delivery time :

  • Culture and morphological identification: 5 to 7 working days.
  • Culture and molecular identification: 5 to 7 working days.

Cost of testing: