The composted substrate throughout phase ii should

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Unformatted text preview: convert their specific source of carbohydrates. The composted substrate throughout Phase II should appear to have moderate “firefang”—a term referring to the white-flecking microbial growth pattern of the thermophilic microorganism (Figure 9). Pasteurization (peak heat, boost) should be completed toward the start of Phase II. Effective pasteurization will eradicate harmful bacteria, nematodes, insects, and fungi. In general, air and composted substrate temperatures should be raised together to 140ºF (60ºC) for at least 2 hours. Growers make several compromises to this range, but it is a time-temperature relationship. The good microbes grow best at temperatures from 115ºF to 140ºF; the more ammonia-utilizing microbes grow best in the temperature range of 120–128ºF (47–49ºC). The longer the microbes in the composted substrate remain in this optimum range with all the critical growth requirements available, the faster the ammonia will be converted. Understanding how these microbes grow and work in composted substrate should make the management of Phase II a little easier. The process of 8 going through this temperature range will produce the most protein or the maximum amount of food for the mushroom. A good rule of thumb is not to drop the composted substrate temperature more than 5ºF per 24 hours, which maintains the compost substrate in the desired range for about 4 or more days. Near the completion of Phase II, growers check for ammonia in the compost. The nose is usually the best tool. However, ammonia-testing kits and strips are available to supplement the nose test. Figure 9. Handful of composted substrate showing the white-flecking (“firefang”) microbial growth. Figure 10. Pure culture of mushroom mycelium growing on an agar plate. Spawn Maintenance A desirable mycelial culture is pure— free of contaminants and of sectoring of other abnormalities. Contaminants include other fungi, bacteria, or insects growing on or infesting the culture media along with the desired mycelial culture. When a culture is first obtained, it should be transferred several times to fresh media to check for any form of contamination (Figure 10). Sectoring is any type of mycelial growth that differs in appearance, growth rate, color, or in any other way from the typical appearance of a given strain. Sectoring is often observed as a more rapidly growing area near the leading edge of growth, exhibiting a different growth habit from the rest of the culture. Other abnormalities that might appear in a culture are fluffy, aerial mycelia, thick or rubbery textures, and color changes such as browning or darkening of the mycelium. Sectors of other change in vegetative growth could affect the productivity of the culture. Therefore, recognizing and avoiding propagation of abnormal mycelia to agar and further spawn production is very important. Many commercially prepared spawn strains are available to commercial and noncommercial growers. All commercially grown strains are pure culture of edible, fresh mushrooms; some may vary in texture and growing requirements. Mushroom spawn is produced in several different strains or isolates. Hybrid White is a smooth-cap, highyield, excellent processing strain. Hybrid Off-White has a cap that is slightly scaly on first break and is a preferred fresh-market strain, and Brown (Portabella, Crimini) produces a chocolate-brown, mature mushroom that is fleshy and has a strong, mature flavor. Spawn Production The process of making spawn remains much the same as Penn State professor emeritus Dr. Sinden first developed in the 1930s. Grain is mixed with a little calcium carbonate, then cooked, sterilized, and cooled. Small pieces of pure-culture mycelium are placed in small batches on the grain. Once the small batch is fully colonized, it is used to inoculate several larger batches of grain (Figure 11). This multiplying of the inoculated grain continues until the commercial-size containers— usually plastic bags with breathable filter patches—are inoculated. During the colonization of each batch, the containers are shaken every few days to distribute actively growing mycelia around t...
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This document was uploaded on 03/16/2014.

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