B

tose or too little lactose at the start, due to insufficient or excessive cooking, then the pH can end up being less than 5.0 or above 5.4.Both of these situations could result in poor quality cheese, as described below.

After the primary fermentation period, the cheese blocks or wheels are placed into brines containing 20% salt for as long as three days.The blocks may be flipped and additional salt may be applied.Then the blocks are removed and allowed to air dry in coolers at 10°C to 15°C for five to ten days. As noted for Cheddar cheese, salt provides flavor and influences the activities of microorganisms and enzymes present in the cheese, although the average concentration in Swiss cheese is much lower (< 1%). In the case of traditional Swiss cheese and other brined cheeses, salt also helps form a natural rind, due to dehydration at the surface of the cheese.The hard rind provides an excellent natural protective barrier or casing. Brining, in contrast to direct or dry salt methods, also creates a salt gradient, with the concentration decreasing from the surface toward the interior of the cheese. This also affects the development of the microflora.

The next step is perhaps the most crucial. The dried blocks or wheels are moved into warm rooms where the temperature is maintained at 20°C to 25°C. It is during the ensuing three to four weeks that growth of Propioni-bacterium freudenreichii subsp. shermanii occurs.Although this bacterium is morphologically, physiologically, and genetically distant from the lactic acid bacteria, it is similar in that it prefers an anaerobic atmosphere and has a fermentative metabolism. Propionibacteria are neutrophiles and are salt-sensitive, so low pH and high salt conditions are inhibitory. They are added to the milk as part of the starter culture, but at a much lower rate—the inoculated milk contains only about 102 to 103 cells per ml.And although these bacteria are moderately resistant to high temperature, growth does not occur until the cheese is moved into the warm room. When these bacteria are grown on lactose or other fermentable carbohydrates, large amounts of propionic and acetic acids and lesser amounts of carbon dioxide are pro duced. However, as explained above, by the time Swiss cheese is placed in the warm room, there should not be any carbohydrate still in the curd and available for fermentation. So what does P. freudenreichii subsp. shermanii use as a substrate? In fact, this organism is capable of metabolizing the lactic acid produced by the lactic starter culture via the propionate pathway (Figure 5-8).This pathway yields pro-pionic acid, acetic acid, carbon dioxide and ATP. If, however, any lactose is still available, then more of these products will be formed. Moreover, excess production of carbon dioxide, in particular, has serious consequences for the final product.

As noted above,P. freudenreichii subsp. sher-manii is initially present at relatively low levels in the cheese. As it grows in the warm room, small micro-colonies within the curd matrix are formed. Likewise, the fermentation end products are evolved in that same vicinity and diffuse out into the neighboring region within the curd. Although the acids are readily dissolved, the carbon dioxide molecules will diffuse through the curd only until they reach weak spots, where they will then collect along with other CO2 molecules made by other microcolonies. Eventually, enough CO2 molecules will have accumulated, and voila—an eye is formed. However, this entire sequence of events depends on several hard-to-control variables.

First, CO2 formation must be slow and steady. If too much CO2 is produced all at once or the curd is too firm, the gas pressure can exceed the ability of the curd to sustain the gas and large, even exploded holes are formed. If the body of the curd is too soft and the weak spots too numerous, then many small eyes will form.The hard rind produced as a result of the brining and drying steps also serves an important role; without a rind, the CO2 could theoretically escape clear out of the cheese. Of course, CO2-impermeable bags provide an easy remedy for this problem (thus was born rind-less Swiss, as described below). Obviously, time is a critical factor as well—too much or not enough incubation time will result in less than perfect eye development. Experienced cheese

Brew Your Own Beer

Brew Your Own Beer

Discover How To Become Your Own Brew Master, With Brew Your Own Beer. It takes more than a recipe to make a great beer. Just using the right ingredients doesn't mean your beer will taste like it was meant to. Most of the time it’s the way a beer is made and served that makes it either an exceptional beer or one that gets dumped into the nearest flower pot.

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