Eggshell and protein membrane separation

Eggshell and protein membrane separation is a recycling process. Nearly 30% of the eggs consumed each year are broken and processed or powdered into foods such as cakes, mixes, mayonnaise, noodles and fast foods.[1] The US food industry generates 150,000 tons of shell waste a year.[2] The disposal methods for waste eggshells are 26.6% as fertilizer, 21.1% as animal feed ingredients, 26.3% discarded in municipal dumps, and 15.8% used in other ways.[3] Many landfills are unwilling to take the waste because the shells and the attached membrane attract vermin. When unseparate, the calcium carbonate eggshell and protein-rich membrane have little or no value or use;[4] however, the invention of an eggshell and membrane separator has allowed for the recycling of these two products.

Eggshell composition

Chicken eggshells are made up of 95% calcium carbonate by weight and the remaining material is primarily organic matrix.[5]

Membrane composition
Main article: eggshell membrane

Eggshell membrane is primarily composed of fibrous proteins such as collagen type I.[6]

Waste eggshell uses

Pharmaceuticals

The rich calcium carbonate shell has been used in the application for calcium deficiency therapies in humans and animals.[3][5] A single eggshell has a mass of six grams which yields around 2200 mg of calcium.[7] (6000 mg × 0.95 × 0.4= 2280 mg) Eggshell particles are used in toothpaste as an anti-tartar agent.[3] Powdered eggshells have been used for bone mineralization and growth.[3][4][5]

Food industry

Recent applications of eggshells include producing calcium lactate as a firming agent, a flavor enhancer, a leavening agent, a nutrient supplement, a stabilizer, and thickener.[3][5] Eggshells are also used as a calcium supplement in orange juice.[2]

Other issues

Eggshells have been incorporated into fertilizers as a soil conditioner.[3][8] They have also been used as a supplement to animal feed.[3][8] More recently the egg calcium carbonate particles have been used as coating pigments for ink-jet printing.[8] Powdered eggshells are also used in making paper pulp.[2] Recently eggshell waste has been used as a low cost catalyst for biodiesel production.[4]

Methods

Non-chemical separators

Joseph H. MacNeil, Professor of Food Science at Penn State University, developed a machine that uses a delicate multi-bladed knife to scrape the membrane from the surface of shell fragments.[9] This invention uses a water-based method to separate the eggshell and protein membrane. The two products are processed in two streams to yield mm size particles of dry membrane and mm size particles of dried shell.

Another non-chemical separation technique utilizes steam heat, mechanical abrasion, and a light vacuum to separate the hard eggshell from the protein-containing membranes.[10] This invention passes shell fragments obtained from egg-breaking facilities through a series of heated augers. Once the shell and membrane flakes reach the appropriate moisture content, the vacuum pulls them into a cyclone device. The cyclonic action further separates the heavier eggshell flakes from the lighter membrane flakes. This invention has been commercialized and can easily separate multiple metric tons per day, allowing for the production of valuable products including commercial volumes of natural eggshell membrane or NEM.

Levi New invented a non-chemical and non-thermal separation technique that utilizes airflow to pull egg shells through a venturi. The material is subjected to pressure waves while passing through the venturi.[11] A PulverDryer machine configured with a venturi sized to process egg shell pulverizes the shell component into fine powder and discharges the membrane as an intact dry flake material. The two components are separated in post processing by a standard shaker screen table, then the membrane is cleaned via one of several standard washing processes, depending on end use. Up to several tons of egg shell material can be processed per hour.

Dissolved air-flotation separation unit

The waste eggshells are put into water and then ground to separate the eggshell from the protein membrane.[8] Then the ground eggshell is placed in a separate vessel where air is injected into the water flow. The air and water mixture causes the lighter component (protein membrane) to float and the heavier (calcium carbonate eggshells) to sink. This unit recovers 96% of eggshell membrane and 99% of eggshell calcium carbonate in two hours.[8]

Water and acetic acid

The inventor of this method is Vladimir Vlad. The machine uses unseparated eggshells that are placed in a fluid tank, applying cavitation to separate the eggshell membrane from the eggshell. The fluid tank in this case contains distilled water and acetic acid to provide continuous processing. Also this invention has a method for collecting separated eggshells to grind them into an eggshell powder.[7]

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References
  1. Sonenklar C: Famous for Egg Waste. Research/ Penn State 1999, 20.
  2. Hecht J: Eggshells break into collagen market. New Scientist 1999, 161:6-6.
  3. Daengprok W, Garnjanagoonchorn W, Mine Y: Fermented pork sausage fortified with commercial or hen eggshell calcium lactate. Meat Science 2002, 62:199-204.
  4. Wei Z, Li B, Xu C: Application of waste eggshell as low-cost solid catalyst for biodiesel production [electronic resource]. Bioresource Technology 2009, 100:2883-2885.
  5. Daengprok W, Issigonis K, Mine Y, Pornsinpatip P, Garnjanagoonchorn W, Naivikul O: Chicken eggshell matrix proteins enhance calcium transport in the human intestinal epithelial cells, Caco-Journal of Agricultural and Food Chemistry 2003, 51:6056-6061.
  6. Wong, M.; Hendrix, M.J.; van der Mark, K.; Little, C.; Stern, R. (July 1984). "Collagen in the egg shell membranes of the hen". Dev Biol. 104 (1): 28–36. doi:10.1016/0012-1606(84)90033-2. PMID 6203793.
  7. Vlad: Eggshell membrane separation method. In US Patent, vol. 7534909. United States: Biova, L.L.C; 2009.
  8. Yoo S, Kokoszka J, Zou P, Hsieh JS: Utilization of calcium carbonate particles from eggshell waste as coating pigments for ink-jet printing paper [electronic resource]. Bioresource Technology 2009, 100:6416-6421.
  9. MacNeil JH: Method and apparatus for separating a protein membrane and shell material in waste egg shells. In United States Patent (Foundation TPSR ed., vol. 6,176,376. United States: The Penn State Research Foundation; 2001.
  10. Adams: Egghell membrane separation method. In US Patent 7,017,277, United States: ESM Technologies, LLC; 2006.
  11. New: Eggshell membrane separation process. In US Patent 8,448,884 B2, United States; 2013.
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