EFFECTS OF PERSERVATIVES AND ENVIRONMENTAL CONDITIONS ON BREAD SPOILAGE Samantha Gerold

Abstract

Discussion

ResultsFood spoilage is a topic of interest to both food manufactures and consumers because humans may deem damaged or spoiled food as inconsumable. Bread is particularly susceptible to spoilage by bacteria, yeast and molds by surface and airborne contaminants. Contamination occurs after baking because bacteria and fungal spores are killed in the baking process. One way manufactures attempt to control spoilage is with the use of preservatives, which can be natural or artificial. Natural preservatives, or Class-I Preservatives are those found in nature, such as salt, sugar, and vinegar. Artificial preservatives, or Class-II Preservatives, are those that are manmade, such as calcium propionate 282. It is our objective to test which types of preservatives, natural or artificial, are best at preventing bread spoilage. Physical conditions, such as moisture and light, can also enhance bread spoilage, and may influence the effectiveness of preservatives. This study examined the rate of fungal growth on six types of bread (one containing natural preservatives, one containing artificial preservatives, and four without any preservatives). We also examined the effect of moisture and light on fungal growth for each type of bread. If consumers have greater knowledge about which kinds of preservatives preserve breads longer and in what conditions to store breads, bread spoilage may be able to be prevented resulting in a longer consumption period. We hypothesized that bread without preservatives would have the most microbial growth, which was supported by this study.

Table 1: Fungal Growth Coverage on Day 7

The results showed that sourdough bread containing natural preservatives had the most fungal growth, thus, our hypothesis was not supported.  This study’s results were not supported by cited literature which show that "among the natural preserving systems, sourdough has long been known to improve the shelf lives of bread and bakery products” (Lavermiocca, Valerio, and Visconti) because sourdough bread produces acetic acid, which contributes to antifungal activity. Whole wheat bread was the only type of bread that did not have fungal growth. These results were not supported by cited literature which show that the “shelf-life of whole wheat flour is shorter compared to white four due to the presence of lipids and lipid-degrading enzymes. Lipolytic degradation leads to reduction in functionality, palatability and nutritional properties.” (Doblando-Maldondo, Pike, Sweley, and Rose 119-126) Results also showed that fungal growth did not occur in light and dry conditions, but occurred most in dark and moist conditions. This could be due to the fact that bread mold grows more quickly in dark, wet and warm environments. Molds are composed of mostly water, which allow cells to function properly and protect them from drying out. The enzymes that direct biochemical processes in mold cells function more efficiently at warmer temperatures, optimally around 27°C. Lastly, molds do not need light for normal growth because they do not participate in photosynthetic processes, and instead use extracellular digestion. (Shepherd) Sourdough bread samples were purchased one week after the purchase date and initial data collection of all other samples. Sourdough samples could have received slightly more or less sunlight and heat depending on the weather conditions of each week. Moreover, phenyllactic acid only prevents against limited yeast and mold growth (Schnürer).This could explain why sourdough bread had the most fungal growth. The diet whole wheat bread contains orange juice, which has ascorbic and benzoic acids. These acids are commonly used to prevent yeast growth, which could explain why the diet whole wheat bread had no fungal growth (Hazan, Levine, and Abeliovich). Lastly, the results of this study could stray from our hypothesis because all bakery breads were susceptible to microbial contamination after the baking process, particularly since bakery breads are left unpacked on shelves with the potential of being touched by several people before purchase and consumption.

Acknowledgements

Fig.1: Dark, Moist Whole Wheat, Day 7

Fig. 2: Dark, Moist Yellow Flour, Day 7

References Bengtsson, Nils, and Thomas Ohlsson. Minimal Processing Technologies in the Food Industry. Woodhead Publishing, 2002. Print.Doblando-Maldondo, Andres, Oscar Pike, Jess Sweley, and Devin Rose. "Key issues and challenges in whole wheat flour milling and

storage." Journal of Cereal Science. 56.2 (2012): 119-126. Web. 25 Mar. 2014. Print.Geetha, M., and P. Saranraj. “Microbial Spoilage of Bakery Products and Its Control by Preservatives.” International Journal of Pharmaceutical &

Biological Archive 3.1 (2012): 38-48. PrintHazan, Reut , Alexandra Levine , and Hagai Abeliovich . "Benzoic Acid, a Weak Organic Acid Food Preservative, Exerts Specific Effects on

Intracellular Membrane Trafficking Pathways in Saccharomyces cerevisiae." Applied and Environmental Microbiology . US National Library of Medicine National Institutes of Health , n.d. Web. 25 Mar 2014. http://www.ncbi.nlm.nih.gov/pmc/articles/PMC492424/.

Lavermicocca, Paola, Francesca Valerio and Angelo Visconti. “Antifungal Activity of Phenyllactic Acid against Mold Isolated from Bakery Products.” Applied andEnvironmental Microbiology 69.1 (2003): 634-640. Print.

Doblando-Maldondo, Andres, Oscar Pike, Jess Sweley, and Devin Rose. "Key issues and challenges in whole wheat flour milling and storage." Journal of Cereal Science. 56.2 (2012): 119-126. Web. 25 Mar. 2014. Print.

Schnürer, Johan. “Antifungal Lactic Acid Bacteria as Biopreservatives.” Trends in Food Science & Technology 16.1 (2005): 70-78. Print.Shepherd , Hurley. "Why is it that bread mold grows quicker in dark, wet and warm conditions?." 07 May 1997. Washington University Medical

School, Online Posting to MadSci Network: Microbiology. Web. 25 Mar. 2014. Print.

Introduction Knowledge about how to prevent bread spoilage due to type of preservative and storage conditions can greatly increase the shelf life. The consumption of foods that have exceeded their shelf life and have spoiled can lead to food borne illnesses and in serious cases, death. Breads are baked in a moist environment, which leads to high levels of microbial growth (Saranraj and Geetha). Microbial growth makes breads susceptible to yeast, mold, and other fungus. This has led to the use of natural and artificial preservatives. One of the most well studied natural preservatives is phenyllactic acid that is produced by the bacteria Lactobacillus plantarum that is present in sourdough breads (Lavermicocca, Valerio, Visconti). Artificial preservatives can appear in multiple different synthesized forms but one common preservative is the fungal inhibitor proprionic acid, and more specifically calcium propionate (Lavermicocca, Valerio, Visconti). It is commonly used in commercial bread products, and at high concentrations can extend the shelf life of many breads (Meyer, Suhe, Nielsen). This study compared the effectiveness of the artificial preservative calcium propionate and the natural preservative phenyllactic acid based on the amount of mold growth on six different types of breads. The effects of moisture and light were also tested to simulate the different ways that bread may be stored in a household. The appearance and relative size of mold was used to determine which preservative prevented the most fungal growth.

MethodsFactors of fungal growth were tested by variations in type of preservative, light exposure, and water

content. Procedure: •Each type of bakery bread was baked and purchased on the first day of data collection, with sourdough being purchased and recorded one week later. •Each type of bread (Bimbo white bread, bakery sourdough bread, white bread, whole wheat bread, diet whole wheat bread, and yellow flour bread) were cut into 10x5x2 centimeter pieces and placed into a Ziplock sandwich bag. •One bagged sample of each type of bread was kept in the following conditions:

• Light and Moist • Light and Dry• Dark and Moist • Dark and Dry

•The bags that were to receive light were kept only in the clear Ziplock bags. The bags that were to be kept in darkness were placed in the Ziplock bag, which was then placed in a brown paper bag. •5 mL of deionized water was initially added to the bread that was kept in moist conditions on the first day of data collection. Then, 2 mL of water was added to the moist bread each following day for a seven-day period. •All bags were kept at the same temperature conditions of 18°C. •Observations and photographs of fungal growth was recorded at the same time each day.

Key:0 = -1 = + 2 = ++ 3 = +++4 is negligent

At the conclusion of this experiment, sourdough bread, containing the natural preservative phenyllactic acid, displayed the most fungal growth under the dark and moist conditions. The only bread that displayed no growth was the bakery whole wheat bread. The conditions that facilitated the most fungal growth were dark and moist. The light and dry conditions showed no mold growth. Fig. 3: Dark, Moist Bimbo White, Day 7

Fig. 4: Dark, Moist Diet Whole Wheat, Day 7

Fig. 5: Dark, Moist Sourdough, Day 7Fig. 6: Dark, Moist White, Day 7

Key: +++ = Greater Than Half of Surface Area of Bread Covered in Mold ++ = Approximately Half of Surface Area Covered in Mold + = 1-2 Small Spots of Mold on Surface Area of Bread — =No Mold Growth

Graph 1: Fungal Growth Coverage on Day 7