fig1 shows a shell egg 10 comprising a shell 12 surrounding an interior space 14 , the interior space containing an albumen layer 16 surrounding a yolk 18 . shell 12 has an outer surface 20 . a coating 22 covers at least a portion of the shell outer surface 20 . for example , as shown in fig2 , the coating 22 may comprise a band 24 extending around the shell egg 10 . fig3 shows another embodiment , wherein the coating 22 covers the entire outer surface 20 of the egg 10 . with reference again to fig1 , coating 22 may have a thickness 24 which is uniform over the entire coating , or the thickness 24 of coating 22 may vary as a function of position about the outer surface 20 . the minimum thickness of the coating 22 is such that it strengthens the shell 12 , i . e ., coating 22 has a thickness 24 sufficient to increase the energy required to crush the shell egg 10 when compared with a comparable shell egg having no coating . the thickness 24 of the coating 22 should also be sufficient to prevent the shell egg 10 from shattering when cracked open . in one example embodiment , the coating 22 comprises a food grade natural resin , for example , shellac . the shellac may be dewaxed raw shellac , decolorized shellac , bleached shellac , and / or combinations thereof . when shellac is used as the coating 22 , the thickness 24 may range from about 0 . 04 mm to about 0 . 45 mm . the shellac may be brushed or sprayed in liquid form onto the outer surface 20 of shell 12 to form the coating 22 . in one example , the liquid shellac comprises a shellac and ethanol solution . experiments have shown that ethanol of 190 proof is an effective vehicle for the shellac . the shellac may comprise from about 5 % to about 30 % of the solution by weight . experiments have also shown that a solution comprising 190 proof ethanol and about 20 % shellac by weight is advantageous . after the liquid shellac - ethanol solution is applied to the shell eggs 10 the solution is dried to form the coating 22 . drying may be effected by subjecting the shell eggs to a stream of heated gas , such as air heated to between about 20 ° c . and about 50 ° c . multiple spraying and drying steps may be used to achieve a coating 22 having the desired thickness 24 . in another example , the liquid shellac comprises a shellac and acetone solution . the shellac may comprise from about 5 % to about 30 % of the solution by weight . after the liquid shellac - acetone solution is applied to the shell eggs 10 the solution is dried to form the coating 22 . drying may be effected by subjecting the shell eggs to a stream of heated gas , such as air heated to between about 20 ° c . and about 50 ° c . multiple spraying and drying steps may be used to achieve a coating 22 having the desired thickness 24 . in a further example , the liquid shellac comprises shellac , ethanol and acetone in solution . the shellac may comprise from about 5 % to about 30 % of the solution by weight . it is expected that the ratio of ethanol to acetone may range from about 90 : 10 to 10 : 90 by weight for practical applications . it has been found that a ratio of ethanol to acetone of about 3 : 1 by weight is advantageous and promotes rapid drying . after the liquid shellac - ethanol - acetone solution is applied to the shell eggs 10 the solution is dried to form the coating 22 . drying may be effected by subjecting the shell eggs to a stream of heated gas , such as air heated to between about 20 ° c . and about 50 ° c . multiple spraying and drying steps may be used to achieve a coating 22 having the desired thickness 24 . in another example embodiment , the coating 22 comprises a mixture of paraffin wax and beeswax . when the mixture of paraffin wax and beeswax is used as the coating 22 , the thickness 24 may range from about 0 . 05 mm to about 0 . 5 mm . the ratio of paraffin wax to beeswax in the mixture may range from about 2 : 8 to about 8 : 2 by weight , with a ratio of paraffin wax to bees wax of about 1 : 1 being found advantageous in experiments . the mixture of paraffin wax and beeswax is applied to the outer surface 20 of the shell egg 10 in liquid form and may be effected by dipping the shell eggs into a molten wax bath , or by spraying or brushing the molten wax mixture onto the outer surface . in a particular dip coating method , the paraffin and beeswax were heated in a double - walled boiler at 80 ° c . to 90 ° c . until fully liquefied . eggs at 4 ° c . to 25 ° c . were dipped in the molten wax using a wire holder and quickly removed once fully submerged . within seconds of removal from the wax , eggs were polished using a blotting paper ( although it is expected that filter paper should be equally useful ). the paper removes and spreads any excess wax that was not fully solidified . in a particular spray coating method , a gravity - fed sprayer was used to spray - coat the eggs . the sprayer used a venturi - type nozzle to pull the molten wax mixture from a reservoir and then used other air passages to force the spray pattern in a certain direction ranging from almost linear to circular application . in this example , air at ambient temperature was passed through the sprayer . to prevent cooling the wax and clogging the spry nozzles , the sprayer was heated up to 90 ° c . until it was at a temperature equal to that of the molten wax mixture . similarly , hot air could be used to maintain wax spray in the molten state . as the hot wax contacted the eggs , it solidified . as only one side of the eggs could be coated at a time , the eggs were rotated to ensure complete coverage of the outer surface 20 . this application method may be repeated until the desired number of coats , providing a desired coating thickness , is achieved . the dip and spray coating methods described above may also be used to apply a coating of only paraffin wax or only beeswax to achieve a coating having a thickness sufficient to increase the energy required to crush the shell egg as compared with a comparable shell egg having no coating . in another example embodiment , the coating 22 comprises a food grade polymeric emulsion , for example , polyvinyl acetate . when polyvinyl acetate is used as the coating 22 , the thickness 24 may range from about 0 . 02 mm to about 0 . 4 mm . the polyvinyl acetate may be brushed or sprayed in liquid form onto the outer surface 20 of shell 12 to form the coating 22 . drying may be effected by subjecting the shell eggs to a stream of heated gas , such as air heated to between about 20 ° c . and about 50 ° c . multiple spraying and drying steps may be used to achieve a coating 22 having the desired thickness 24 . the coatings listed above , i . e ., the food grade natural resin ( shellac ), the wax mixture ( paraffin and beeswax ), single wax coatings , and food grade polymeric resins ( polyvinyl acetate ) may also be mixed with other agents such as food - grade colorant ( including fd & amp ; c blue no . 1 , fd & amp ; c red no . 3 , cochineal extract , carmine , or other natural or synthetic colorants ) a food - grade fungicide ( including benzoic acid , sorbic acid , other organic acids , parabens , or natamycin ), a food - grade anti - bacterial agent ( including nitrites , nisin or other antimicrobial peptides , or antimicrobial plant extracts ) as well as combinations thereof . result summary of testing of egg shell strength as affected by processing and coating eggs tested in these experiments were obtained from hemmelgarn & amp ; sons , inc ., coldwater , ohio . each trail involved treating eggs collect on the same day from the same farm . before coating , shell eggs were processed using a procedure known to weaken the shell . this procedure involves heating shell eggs in a water bath at 58 ° c . and treating heated eggs with a high concentration of gaseous ozone ( more than 10 %, wt / wt , of ozone in oxygen ). in one of the experiments , processed eggs were coated with three coating materials ; these are shellac , paraffin wax and beeswax . different varieties of shellac were tested as coating materials . fresh uncoated eggs were included in the experiment to represent eggs with normal shell strength . additionally , processed uncoated eggs also were included in the study . eggs were tested for strength of the shell and its tendency to shatter using a material testing instrument ( instron 5542 ; instron , norwood , mass ., usa ) equipped with an appropriate compression anvil ( s5402a ). data from the tests indicates that two distinctive regions of strength are evident . the first region is simply a force required to initially crack the egg . application of a coating was shown to increase the initial cracking force above that of processed eggs . the second region described the force needed to crush the eggs when the anvil proceeds for a distance of 4 mm ( graph 1 in fig4 ). when the work ( energy ) required to crush the eggs was calculated from the data , the trends indicated that the fresh egg required more work ( 30 to 40 n * mm ) to crush its shell , compared to the work required to crushed an egg processed in a way to weaken its shells ( 15 to 20 n * mm ). the data also indicated that the processed eggs coated by dipping in beeswax had the strongest shell ( 45 n * mm ). processed eggs coated with shellac have stronger shell ( 23 - 30 n * mm ), compared to that of processed and uncoated eggs . although coatings materials varied in ability to protect egg shell , beeswax and shellac showed significant improvement in shell strength . examples of these data are presented in table 1 of fig5 and graph 2 of fig6 . the following advantages are expected from coated eggs according to the invention as disclosed herein : coated eggs are expected to have longer shelf life in consumer &# 39 ; s refrigerators . the coating allows for application of antifungal agents that prevent mold growth during storage . the coating is expected to improve the safety of shell eggs by preventing cross contamination and ingress of pathogenic organisms through cracks in the shell . the coatings are expected to decrease egg loss and improve consumers experience during egg preparation . it is expected that coated eggs will be easier to label with company logos . coating material could be colored to distinguish brands and to appeal to consumers .
coatings for shell eggs improve the strength and shatter resistance of processed eggs . the coatings include food grade natural resins such as shellac , mixtures of paraffin and beeswax , and food grade polymer emulsions such as polyvinyl acetate .