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Happy Easter! The history of eggs and cyclodextrin

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Easter is a religious holiday, but some of its customs, such as Easter eggs, are likely linked to pagan traditions. The egg, an ancient symbol of new life, has been associated with pagan festivals celebrating spring. This gave the idea to overview the literature on eggs and cyclodextrin.

The first mention of eggs in the Cyclodextrin News database is the patent application of Kuroda and Mogi in 1974. They added 0.1-1.0% alpha-, beta- or gamma-CD (ACD, BCD or GCD) to dry egg albumin in order to obtain a product of good whipping characteristics, which can be mixed with spray-dried or frozen egg white to improve the whippability.

The most typical application of CDs with eggs is the removal of cholesterol to improve their nutritional value. Monserbio (Bayol et al. 1989) patented first the procedure: powdered egg-yolk, fresh egg-yolk and fresh egg samples were mixed with aqueous BCD solution and after mixing at 40oC for 5 hours the precipitated cholesterol-containing complex was removed by centrifugation. This procedure reduced the cholesterol content by 57-83 %. Another patent describes how to remove the residual BCD from egg yolk by using alpha-amylase from Aspergillus niger, A. oryzae, Bacillus polymyxa, B. coagulans, Flavobacterium, or swine pancreas (Cully and Vollbrecht 1991). Later combined use of cyclodextrin transglycosylases and alpha-amylases was claimed to reduce the residual CD content to less than 10 ppm (Cully et al. 1992). In another procedure also debranching enzymes were used in addition to these two (Shieh and Hedges 1996). This procedure for cholesterol removal was extended to dairy products and BCD was regenerated from the cholesterol complex by extraction of cholesterol with a solvent chosen from hexane, acetic acid or acetic acid/butanol mixtures (Oakenfull et al. 1991). Later it was shown that not only cholesterol but also triglycerides are partially removed from egg yolk (Dressnandt et al. 1995). Kwak et al. (2006) introduced the use of crosslinked BCD as an important improvement of the process. The crosslinked BCD was efficient for cholesterol removal in whole egg, but recycling was possible for only limited repeating times due to the interaction of the BCD and egg protein (Jeong et al. 2014).

Subchronic toxicity dietary studies were conducted in albino rats on the safety of residual BCD in egg samples treated for cholesterol removal at concentrations of 250, 125 and 20 ppm for a period of 90 days (Rao et al. 2000). Daily food intake, body weight gain, relative organ weights, histopathological, hematological and serum enzyme activities were studied. It was concluded that BCD-treated egg samples did not cause any toxicity.

The question arose whether the cholesterol content of eggs could be reduced by feeding hens with BCD. In the experiment of Murai et al. (1994) by feeding Japanese quail hens the opposite results were obtained: the egg production rate was rapidly decreased with the dietary beta-CD levels in a dose-dependent fashion. Egg yolk cholesterol concentration was significantly higher in the 10% CD group than in the control group; this was attributed to a decreased egg production rate. According to a Korean study, reduced cholesterol content by approx. 30% was measured using a feed containing 5 to 7% by wt. of beta-CD to poultry, in particular egg laying hens of chicken, a duck, a mallard, a quail, a turkey or an ostrich (Kang et al. 2004 Park et al. 2005). Higher concentration (8 and 10% BCD) diet, similarly to Murai’s results, reduced the food intake, egg production and egg weight. Applying low concentration of CDs is more addvantageous, e.g. a feed containing vitamins and alga stabilized by CD (less than 1% CD in the feed) results in 50% enhancement in daily egg production (Tanaka 2000). Further feed additives containing cysteamine or polyunsaturated fatty acids stabilized by CD were disclosed for improving egg-laying rate and breed egg rate in hens (Chi et al. 2003 Park et al. 2007).

Some miscellaneous curiosities:

The most important application of CDs in egg is the removal of cholesterol. The latest study was published in the last year (Alonso et al. 2019) showing that cholesterol-reduced food is still in fashion.

References

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