Cholesterol Oxidation Products in Stored Egg Powder

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Jonathan Swindler and Dr. Michelle Lloyd, Nutrition Dietetics and Food Science Department

Cholesterol Oxidation Products (COPs) are a family of 27-carbon cholesterol oxidation derivatives that are formed from the auto-oxidation of cholesterol. They can result in food from high-temperature processing and storage. COPs have a variety of cytotoxic effects and are believed to be involved with major chronic diseases including atherosclerosis, neurodegenerative processes, diabetes, and kidney failure (Sottero and others 2007).

Egg powder is in a wide variety of foods including bakery products and pasta products. Egg powder is also a common item found in food storage and can be an important source of protein in the diet. Whole egg powder is particularly high in cholesterol and can also have high amounts of COPs. Traditionally, whole egg powder has a shelf life of one year, and almost all recent studies on the storage of egg powder deal with storage of one year or less. The purpose of this study is to determine identities and amounts of COPs formed in egg powder stored for five years under various conditions.

Samples of whole egg powder, which were stored for five years in steel cans at various conditions, were tested for six different COPs. Egg powder samples were divided based on two variables: 1. storage at room temperature (22°C) or chilled temperatures (10°C) and 2. storage with and without oxygen absorbers. Controls included a five year-old stored frozen sample (-18°C) and three fresh samples of different lots from the same manufacturer. COP’s measured included: 7β-hydroxycholesterol (7β-OH), 7-ketocholesterol (7-Keto), 5,6α-epoxycholesterol (5,6α-Epoxy), 5,6β-epoxycholesterol (5,6β-Epoxy), cholestantriol, and 20α-hydroxycholesterol (20αOH). COPs were extracted and quantified using a method from Verardo and others (2010).

Results are summarized in Figure 1 below. Generally, samples without oxygen absorbers (high oxygen storage) had significantly (p<0.05) higher COPs than samples with oxygen absorbers (low oxygen storage). There were also some COPs in samples without oxygen absorbers that were significantly lower in chilled temperature samples than room temperature samples. Oxidation reactions are increased by high temperatures and the presence of oxygen, which can explain these results. Experimental samples, however, did not vary greatly from control samples. This could be attributed to the natural breakdown of these compounds in the experimental samples caused by extended storage (Wahle and others 1993).

In conclusion, it appears that low oxygen and low temperature storage helps decrease COPs in whole egg powder. It is unknown, however, whether the low amounts of COPs are predominantly caused by a slowing of the oxidation reaction or a destruction of the compounds over time. More research needs to be performed to determine these mechanisms and causes.
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References:

  • Sottero B, Gamba P, Gargiulo S, Leonarduzzi G, Poli G. 2009. Cholesterol oxidation products and disease: an emerging topic of interest in medicinal chemistry. Curr Med Chem 16(6):685-705.
  • Verardo V. Pasini F. Iafelice G. Messia MC. Marconi E. Caboni MF. (2010). Influence of storage conditions on cholesterol oxidation in dried egg pasta. J Agr Food Chem 58(6): 3586-90.
  • Wahle KWJ, Hoppe PP, McIntosh G. 1993. Effects of storage and various intrinsic vitamin-E concentrations on lipid oxidation in dried egg powders. J Sci Food Agr 61(4):463-469.