Molding Bread as a Natural Clock

By Peter Fischer

Mold accumulating on bread is but one example of many rather inadvertent natural clocks. In the span of roughly one week (depending on certain factors which will be discussed) a piece of bread will begin to show signs of mold growth. The time in which the bread takes to be covered in mold varies, but when dealing with bread that has few preservatives and a temperature in the high 70s this can happen in roughly two weeks.

mold sporesMolding bread serves as a natural clock whether people choose to consciously label it as such. Obviously, when the bread becomes moldy the consumer is aware that a number of days have passed since the bread had been bought. However, important to note is the number of days since the bread was baked – not simply bought – which must factor into the number of days for mold to take hold.

One strength of molding bread as a natural clock is that it is relatively easy to observe – simply wait until the mold appears. However, most people do not sit around and watch bread grow mold. Thus, molding bread relates to people as a natural clock without really intending to do so. While it is true that bread mold alerts people to the amount of time that has passed since the bread was fresh, the average person would not directly associate the accumulation of mold as a natural clock.

Despite molding bread being an interesting way to look at natural clocks, it is not a scientifically accurate natural clock. This is because of the various factors which must be taken into account. For one, the growth rate of the mold is proportional to the population of mold. At first, the growth rate will be exponential. Later, when the food supply (bread) begins to exhaust, the growth rate too will slow and eventually stop. Therefore, the amount of bread as well as the initial amount of mold spores must be taken into account.

Moreover, temperature is a factor. Molds grow best at temperatures between 77 and 86 degrees Fahrenheit. Consequently, the reason the mold is growing on the bread is due to the presence of mold spores (which are nearly ubiquitous in houses), the food source of bread, the presence of moisture, and a tolerable temperature (room temperature is more than adequate). Since mold growth is stunted by cold temperatures, many people choose to either refrigerate or freeze their bread. Thus, the natural clock depends largely in part on the temperature of the bread.

Yet another factor to consider in using bread mold as a natural clock is the presence of preservatives in the bread. If the bread is homemade or fresh from the bakery there will be few, if any, preservatives. However, if you buy a loaf of bread produced in bulk by a large company the number of preservatives will, in most cases, be higher. Thus, it will take longer for the mold to be visually present. Many companies add preservatives which keep their bread from showing signs of mold for up to three weeks.

moldy breadUltimately, the bread a consumer buys or bakes starts fresh. This is the initial condition. With the passing of roughly one week mold will start to become visually present. The mold begins as specks which, over time, grow larger. Finally, after one additional week the mold continues to accumulate on the bread until it reaches its final condition and the food source is exhausted. This particular natural clock varies greatly because of factors like the amount of bread, temperature, moisture level, and amount of preservatives. The two week time scale is for a loaf of bread roughly a foot long containing few, if any, preservatives and a temperature ranging from 75 to 85 degrees Fahrenheit. Due to many factors which must be taken into account, molding bread as a natural clock is not especially accurate. However, it is one interesting example of how items in everyday life act as natural clocks, whether we consciously realize it or not.