The U.S. egg industry uses the equivalent of approximately four billion 12-egg cartons every year, assuming a constantly producing flock of 265 million hens at an average hen week production of 76% and with 2/3 of all production marketed in shell form. Allowing a nominal value of 12 cents per 12-egg carton or equivalent, annual expenditure on packaging for shell eggs approaches $500 million.
Egg cartons represent the link between producers and consumers. Cartons protect product from damage during transport and handling, ensuring intact and clean shells. Cartons with attractive artwork project a positive image for both national and store-branded products. The inner lids display nutritional information with the outer lid carrying the statuary USDA grade and shield, the UEP and other welfare logos in addition to plant identification, day of pack and use-by date. Cartons may be constructed of cellulose fiber, polystyrene foam, PET [polyethylene terephthalate] transparent polymer or PLA [Polylactic acid] potentially-biodegradable material.
Acceptability of cartons by consumers is traditionally based on the ability to inspect product for shell integrity and cleanliness at point of sale. Even transparent PET cartons, which show at least 30% of the shell surface, are opened to confirm acceptability. The tab, or thermally sealed cartons as used in the EU, would probably be rejected by U.S. consumers. This reality presumes an effective molded closure which allows cartons to be opened at point of sale to inspect the contents followed by secure closing before transfer to the basket or trolley. Practical aspects relating to the design of cartons include compatibility with packers and stampers, sizing of the cells and the thickness of partitions to protect eggs from Medium to Jumbo grades and sufficient rigidity to withstand transport in cardboard boxes, metal baskets or racks.
The significant emerging issue in selecting cartons relates to consumer perceptions of sustainability. Cartons which are manufactured either completely or partially from recycled materials are favored by environmentally conscious buyers and consumers. In addition the ability to recycle used cartons is ranked high as an attribute of acceptability. The average U.S. family consumes 50 cartons per year which has obvious environmental implications.
There is a perception that fiber cartons are more environmentally friendly than polystyrene foam or PET. Generally, U.S. consumers do not understand the triangle recycle codes and often are unaware of the environmental fate of their cartons. A study conducted by Franklin Associates LCI in 2008 demonstrated that polystyrene foam cartons which comprise 85%-90% air and 10%-15% polymer require 50% less energy to manufacture compared to fiber cartons. The materials input required for fiber cartons is approximately 2.5 times that of polystyrene foam which has a much lower solid waste component during fabrication. Although there are questions as to the biodegradability of polystyrene if it is not recycled, studies have shown that all plastic food packaging combined represents less than 1 % of the contents of municipal waste dumps.
Clear cartons constructed of PET frequently contain a high component of recycled material. The basic thermal plastic material comprises polymerized ethylene and terephthalate which can be formed into a required shape in heated molds. Clarity is derived from rapid cooling to form an amorphous solid. All PET products bear a #1 in the triangle recycle symbol. Handling at a municipal or contract plant involves separation with subsequent flake production and reprocessing to produce either polyester fibers which are used in carpets or artificial down for all-weather clothing.
Polylactic acid cartons are manufactured using a condensation reaction process which polymerises lactic acid monomers. These are derived by fermenting carbohydrate components, principally starch, contained in corn, beets or potatoes. By adjusting the manufacturing temperature and by selecting components in the formula, the proportion of D- and L- lactides influence polymer morphology from amorphous to crystalline as used in thermo-formed egg cartons. The degradation of PLA requires composting for at least 10 consecutive days at a temperature of 140 F to initiate hydrolysis of poly(lactide) units. The duration of degradation from deposit to total destruction in municipal and commercial composters may range from six months to five years depending on heat, pH, moisture and the composition of the substrate which supports the aerobic microbial flora responsible for ongoing hydrolysis to carbon dioxide and water.
Polystyrene foam containers
Polystyrene foam has been extensively used for food products since introduction in the early 1940s by the Standard Packing Company, the precursor of Tekni-Plex the holding company of Dolco, the leading U.S. manufacturer of foam cartons.
Polystyrene packs have relatively high strength for weight. The foam material provides adequate cushioning for eggs, provided that the cells and dividers are designed to protect eggs of a given grade. As with any carton, over-grading during packing will contribute to shell damage either by vertical crushing or contact between adjacent eggs usually in the end cells. Polystyrene packs can be manufactured in a range of colors corresponding to grade for easy on- shelf identification. Artwork can be applied directly onto the top and undersurface of the lid using mono- or multicolor printing which requires high precision to ensure acceptable register and clarity. Polystyrene foam has a high insulation value. It may take up to three days for in-line eggs within a foam pack to attain 42-45 F after transfer from the packing room to the cold store. In contrast thermal abuse during transport and handling and subsequent to purchase is minimized since eggs within a foam carton are well protected from external heat.
Molded fiber in cartons are produced by a number of companies in the U.S. as the process involved does not require sophisticated equipment, technology or scale of production. Hartmann North America, a subsidiary of Brodrene-Hartmann A/S of Denmark, markets a full range of fiber cartons and keys trays. Fiber cartons usually contain a high content of recycled materials and are regarded by consumers as being “environmentally friendly”. Hartmann has adopted a STEP approach to manufacture. This acronym is derived from “Sustainability Tools for the Entire Production Chain”. Engineers have analyzed each stage of the production process and have optimized energy utilization. Molded fiber cartons and trays can be recycled subject to separation at the waste receiving center. Fiber cartons are biodegradable in municipal waste dumps over various periods of time depending on conditions which promote microbial action.
Pactiv markets a Master Vue range of 6-, 12- and 18-egg fiber cartons which allow partial inspection of eggs through a slot in the lid. Molded fiber flats are available in 30- and 36-egg configurations which are inserted into a light cardboard printed sleeve. The company will soon launch Edge precision molded fiber cartons manufactured from 100% reclaimed paper.
The protective capability of molded cartons depends on the quality of the material used for their fabrication. Soft pulp products used primarily for low-cost generic eggs may contribute to breakage with rough handling especially when exposed to water or stored in an environment with high humidity for prolonged periods. In contrast, rigid molded cartons provide protection equivalent to PET cartons. Pulp cartons offer limited opportunities for printing beyond brand identification and the statuary nutritional information on the underside of the lid. Cartons which allow partial visualization of eggs obviously have a small area for artwork.
Hartmann, Pactiv and other suppliers of quality fiber cartons offer graphic design assistance to clients to prepare labels. Their service extends to creating brand names and logos and may also include point of sale material and vehicle graphics as an integrated support function.
Eggs cartons constructed of PET are available in tri-fold or bi-fold configurations. The Interplast range uses a proportion of recycled material and the company bills itself as “the original green company”. Tri-folds are available as 6-, 8- and 12-cell packs with an 18-cell bi-fold soon to be available. PET cartons are available with cells sized to accommodate either Large or Extra Large grades. In addition to cartons, Interplast produces a 30-egg PET cover which is used over a fiber tray for club store and supermarket applications.
Pactiv, located in Illinois, is a public-traded company manufacturing a wide range of plastic containers for domestic and institutional uses. Based on their commitment to food packaging, Pactiv has an extensive involvement in sustainability. Their engineers have evaluated manufacturing programs and processes in various plants and have conducted Life Cycle Inventory Studies (LCISs) on products to reduce energy utilization, emissions and waste. The Pactiv range includes PET bi-folds in various configurations and a capper for fiber 30-egg trays.
InTech of Florida import and distribute a PET bi-fold carton with effective closure and ventilation features. Their product manufactured in Uruguay incorporates an advanced design for cells to support eggs and incorporates effective and precise closing buttons. Cartons are designed to withstand a uniform weight of twenty pounds across the top surface without deformation.
Advance Engineering is a recent entrant to the market for egg cartons. Based in Michigan the company has extensive experience in the manufacture of plastic medical disposables and automotive components. The Advance tri-fold carton contains 50% recycled material and was designed in accordance with the requirements of a leading producer of specialty eggs. Features include strength and durability, and a cell which cushions and elevates the egg to provide optimal support during transport.
Both bi-fold and tri-fold PET containers require a double-sided labels which are inserted into the underside of the lid. Because PET is transparent, detailed artwork can be designed and printed to produce an extremely attractive package visible on the shelf. Detailed nutritional data, recipes and promotional text can be imprinted on the underside of the lid with greater clarity and multicolor capability than with polystyrene foam. Most suppliers of PET cartons generally have graphic design capability to support their sales activities.
The bottom line
Cartons are as important to the egg industry as corn as they facilitate mass marketing of a fragile food product. Understandably, eye appeal which projects the image of a product relates directly to costs for material and artwork. Sufficient competition exists among manufacturers to ensure competitive pricing but substantial differentials are based on volume of purchase. Relatively expensive tri-fold PET cartons are compatible with specialty and branded eggs since their higher cost can be justified by price of the total product. Ironically, many consumers purchasing the most expensive organic eggs favor molded fiber cartons based on their perceptions of sustainability and biodegradability. Foam cartons offer the greatest range of attributes including protection, insulation, printability and color corresponding to grade.
Future advances will include higher levels of sustainability, design changes which can improve on-shelf quality and eye appeal. Both the industry and carton manufacturers must become more aggressive in their informational programs regarding sustainability. Inappropriate claims and distortions of attributes regarding biodegradability and energy requirements will confuse consumers and will be self-defeating. The egg industry will have to respond to the demands of the major chains, club stores and consumers for environmentally friendly packaging. Perception is unfortunately the reality. There is an evident lack of appreciation for the beneficial characteristics of both PET and polystyrene foam and an unrealistic anticipation of the benefits of PLA given the restraints of commercial composting.