EGG PROCESSING SAFETY, QUALITY AND SECURITY
Location: Egg Safety and Quality
Title: Food Crystals: the Role of Eggs
Submitted to: National Egg Products School Proceedings
Publication Type: Proceedings
Publication Acceptance Date: September 29, 2008
Publication Date: September 29, 2008
Citation: Jones, D.R. 2008. Food Crystals: the Role of Eggs. National Egg Products School Proceedings. p.12.1-12.8.
Sugar, salt, lactose, tartaric acid and ice are examples of constituents than can crystallize in foods. Crystallization in a food product can be beneficial or detrimental and is of particular importance in candy and frozen desserts. The most common crystal in foods is sugar which affects the quality of many products. Grape juice and wine manufacturers have some concern with tartaric acid crystallization. Lactose crystallization can be detrimental in nonfat dry milk. If the crystal reaches a certain state, it will make the dried milk difficult to disperse. Lactose crystals can also form in frozen dairy products if the amount of milk solids is too great leading to a gritty texture. Another common food crystal is salt with a vast market for various size and textures of salt.
What role do eggs perform in food crystal formation? Previous discussions have focused on the foaming and emulsification properties of eggs and egg products. Both of these also factor into food crystal formation. In this discussion, we will examine the role eggs play in food crystal formation in both confections and frozen desserts.
In candy-making, eggs can contribute to air incorporation, water binding, and product structure. The major role for eggs in the candy matrix is to control sugar crystal growth. Fat and protein helps to reduce the size and number of sugar crystals that form in the candy by interfering with the orientation of the sucrose molecules. Eggs can provide either or both fat and protein in the candy matrix. Examples of crystalline candies would include: fudge, fondant, rock candy and divinity.
Divinity candy is a special case for crystalline candies because the sugar crystals are dispersed in a foam. Albumen serves to not only disrupt crystal formation, but serves as a foaming agent helping to give divinity its distinctive texture. The small sugar crystal size and foam texture also serve to enhance the melting quality of the product in the mouth. Too little albumen could lead to a more dense, coarser texture due to the presence of larger sugar crystals and denser foam. The addition of too much albumen could lead to a “chalky” texture due to excessive foam formation for the sucrose syrup.
One of the most common frozen desserts to contain eggs is ice cream. The first wholesale ice cream industry in the U.S. developed in Baltimore, Maryland in 1851. Egg yolks are the predominant portion of the egg found in ice creams. Egg yolk is the traditional emulsifier for ice cream. In 1949, Romanoff and Romanoff listed the following egg products as acceptable ice cream ingredients: dried yolks, dried whole egg, frozen yolks, frozen whole eggs, and fresh whole eggs. Also in this book is the following table depicting average percentage of egg solids found in different types of ice creams:
Content of egg solids (%)
Average commercial brand 0.25-0.50
Vienna ice cream 0.60-1.24
Neapolitan (New York) ice cream 1.42-2.90
With the current standards of identity, these percentages are not allowable, but it is interesting to see how the product has developed over time. The Food and Drug Administration, Department of Health and Human Services has standards of identity for ice cream published in 21 CFR part 135. It states: “…Except in the case of frozen custard, ice cream contains less than 1.4 percent egg yolk solids by weight of the food, exclusive of the weight of any bulky flavoring ingredients used. Frozen custard shall contain 1.4 percent egg yolk solids by weight of the finished food: Provided, however, That when bulky flavors are added the egg yolk solids content of frozen custard may be reduced in proportion to the amount by weight of the bulky flavors added, but in no case is the content of egg yolk solids in the finished food less than 1.12 percent. A product containing egg yolk solids in excess of 1.4 percent, the maximum set forth in this paragraph for ice cream, may be marketed if labeled as specified by paragraph (e)(1) of this section.” In further paragraphs, it states “(f) Nomenclature. (1) The name of the food is “ice cream”; except that when the egg yolk solids content of the food is in excess of that specified for ice cream paragraph (a) of this section the name of the food is “frozen custard” or “french ice cream” or “french custard ice cream”.”
Eggs serve many functions in frozen desserts. Eggs impart flavor to frozen desserts, especially frozen custards where they help to add “richness” to the flavor profile. They also improve the whipping ability and fat structure formation in the ice cream mix. From previous discussions on the emulsification ability of egg yolk, it is no surprise that yolks play this role in ice cream. Egg yolks are particularly desirable as an ingredient in ice cream mixes that do not contain added emulsifiers. The viscosity of the ice cream mix is increased when egg yolks are added. Increases in mix viscosity can aid in transportation within the processing plant (pump-ability), pasteurization (thermal conductivity), and final product texture. Eggs are generally added to frozen dessert mixes before pasteurization.
The primary role of egg products in frozen desserts is to enhance the textural properties (mouth feel) of the product. The lecithin present in the yolk aids in emulsification. This is achieved by forming a film around fat globules in the ice cream mixture therefore allowing these globules to more readily adhere to other solids present in the mixture. The clumping of fat globules is therefore decreased which allows the whipability of the mixture to be improved. A table found in Romanoff and Romanoff (1949) presents the following information on the whipping time of ice cream mix with and without yolk:
Whipping time (minutes)
Sugared frozen yolk 9
Dried yolk 6
The increased interaction of the lecithin-fat globule complex with other solids present in the ice cream mixture leads to the increase in mixture viscosity. This increased interaction also suppresses ice crystal formation which leads to a smoother texture in the final product. A complete understanding of large ice crystal suppression currently can not be attained due to the nature of the freezing process and the instability of the product for laboratory testing once frozen. The formation of smaller ice crystals during freezing leads to a smoother, creamier frozen product. The presence of small ice crystals also enhances the mouth feel properties as the product begins to melt in the mouth. A sense of “grittiness” is less notable.
There are negative factors to consider when adding egg yolks to frozen desserts. Eggs are high in food value which in turn makes them an expensive ingredient. There is the advantage of being able to market the product as “all natural”, “premium”, etc. In general, the use of egg yolk in frozen desserts presents a desirable, clean and pleasant flavor. Overuse of egg yolks in ice cream can lead to undesirable flavor notes. Egg products can also develop off-flavors similar to milk products during improper storage. This is due to the oxidized and lipolyzed flavor compounds that develop. Also, as the product melts, greater foaming is noted in ice cream that contains egg products which can sometimes be viewed as a negative quality attribute by some consumers.
Egg products can be utilized to control crystallization in a diverse realm of food products. Albumen and egg yolk can aid in the control of sugar crystal formation in candies. Egg yolk can enhance the textural properties and aid in the control of large ice crystal formation in frozen desserts. In many cases, the food products that contain eggs are marketed as “premium” quality. This classification can be due to both the enhanced physical and nutritional quality of the product as well as the increased cost associated with the use of egg products as ingredients compared to other ingredients. While there is an increased cost associ