Lab Report/Bread Mold/Revised the Purpose

Lab Report/Bread Mold/REVISED

The purpose of this experiment was to look at two ways bread is stored in the home kitchen, in a cupboard and in the refrigerator. It was hypothesized that bread would stay fresher and be slower to develop mold when stored in the refrigerator. Commercial bakeries and retail stores must ensure the freshness of their products to remain profitable. The findings of this experiment are important to households as end consumers of these products. Moldy bread is unappetizing and may even be unsafe to eat. Because of chemicals and oils often contained in bread baked in a commercial bakery, the product should not go into the compost pile. Therefore, moldy bread is wasted and food waste, over time, can be costly. The experiment was designed to find whether such waste could be avoided with the use of refrigeration.

Literature Review

Lainez, Bergara & Barcenas (2008) evaluated partially baked bread stored in warehouses at 1° C (32° F) and 7 " (approximately 44° F). They found the bread stored at the freezing mark did not show mold until the twenty-eighth day, but that that the bread stored at 7°, still well below room temperature, showed mold on the ninth day. Karagolu, Kotancilar & Gurses (2005) reported similar findings. In their study, calcium propionate added as a preservative during the dough-mixing process helped prolong the development of mold. Calcium propionate helps to reduce moisture within the packaging. Fernandez, Vodovotz, Courtney & Pascall (2006) reported its effectiveness in extending the shelf life of soy bread. Abu-Bhoush, Herald, Dowell, Xie, Aramouni, & Madl (2008) reported similar findings with flat breads. Latou, Mexis, Badeka, & Kontominas (2010) studied hold inhibitors used in sliced wheat bread and Tosi, Re, Masciarelli, Osella, Sanchez, & de la Torre (2002) looked at mold growth in breads made of whole fat and defatted amaranth flours. Clearly, the issue of mold formation in bread products is of concern to manufacturers who seek to enhance shelf life of their products without compromising taste and texture. There did not appear to be any scientific literature on measures that could be used in home kitchens to prolong shelf life of bread and inhibit the growth of mold.

Experiment Design

As stated by Karagolu, Kotancilar & Gurses (2005), "The shelf life of bread is mainly influenced by water content and its distribution in bread that influence the softness of the crumb, crispness of the crust, and quality of the bread." For this reason, an inexpensive loaf of plain white bread was selected for this experiment. It was thought that growth of mold could be seen relatively quickly on this very soft, moist bread.

For the experiment, three slices of white bread were placed in ziptop plastic sandwich bags. One bag was stored in the refrigerator, while the other was stored in a cupboard of a home in which the average temperature was about 65° F. The conditions were selected because they replicate the conditions under which most households store their bread. The experiment could easily be duplicated in any home, or even in a school classroom with a small refrigerator. The cost of the materials is quite small. No special tools or instruments are required. The results of the experiment can be observed with the naked eye.

It was hypothesized that the bread stored in the refrigerator would develop less mold than the bread stored at room temperature and that the formation of mold would occur more quickly in the bread stored at room temperature. Results would be obtained by daily, naked-eye observation of both bread samples. The same type and quantity of bread was used for both samples. Before taking the bread out of the original packaging, it was important that the researcher washed hands thoroughly with soap to eliminate, as much as possible, the chance for contamination. The bread slices were removed from packaging and placed directly in the ziptop bags. The bread was not allowed to rest, even briefly, on another surface, again in an effort to reduce contamination. Both bread samples were stored in the dark, one sample in the refrigerator and the other in a cupboard. Exposure to light was approximately the same each day for both samples. The refrigerated sample was illuminated when the refrigerator door was opened during normal use; the room temperature sample was exposed to some light when the cupboard door was opened. The amount of light each sample received is thought to be insignificant in terms of impact on the results. To reduce threats to internal validity, one could duplicate the experiment under laboratory, rather than home conditions, where both samples could be kept in the dark for exactly the same amount of time each day.

Results

After one week, the bread stored at room temperature showed the first signs of mold. The mold appeared as three small dots, each approximately the size of a pin head, on the top slice of bread. The refrigerated bread showed no sign of mold.

The bread slices were observed daily. The packages were never opened so there was no chance of outside contamination to either. Once the mold started growing on the bread stored at room temperature, more mold growth was observed each day. By Day 13, the final day of the experiment, mold was evident on all three slices of the bread that was stored at room temperature (see photo). Beads of moisture were also observed on the inside walls of the plastic bag; this moisture undoubtedly contributed to the growth of the mold. The bread that was stored in the refrigerator still showed no signs of mold after almost two weeks.

The ziptop bags were opened to assess the moisture and texture of the slices. This was the first time during the experiment that the bags were opened. The moldy bread, not surprisingly, was extremely soft and moist. The refrigerated bread was still soft, but not as soft as the bread stored at room temperature. Although there was still some moisture in the slices, they were beginning to dry out. No mold was evident, so it was assumed that the refrigerated bread was still acceptable to eat, even though taste and mouth feel were probably somewhat compromised by the dryness.

Conclusions

The experiment confirmed the hypothesis. The experiment shows that, at least for the type of soft white bread studied, refrigeration greatly extends the shelf life of the product. The design of the experiment was a key factor in its success. As much as possible, the two bread samples were treated in exactly the same way. Anyone could easily duplicate the experiment at home and it is assumed that similar results would be observed. Duplicating the experiment would demonstrate its validity. From the experiment and literature review, it appears that refrigeration does inhibit the growth of mold on bread. The bread used in the experiment had a high moisture content, which helped to make it soft but which also seemed to encourage the growth of mold. Both bread samples were stored in the dark, but the higher temperature and humidity of the cupboard seemed to facilitate mold growth, whereas the cooler temperature and drier air of the refrigerator did not. For households that do not want to waste food, it would appear that storing bread in the refrigerator would be helpful.