comparing egg quality across production systems

a paper was included in the latest issue of poultry science (december 2020) that i thought might be of interest to our readers. it looked that the quality and cost of commercially available specialty eggs and compared them with conventionally-produced eggs, that is, produced with hens in cages.

they compared brand name eggs labeled as certified organic, enriched diet, cage-free, free-range, pasture-raised, or soy-free.  for the purpose of the study, egg quality was defined as “those characteristics of an egg that affect consumer acceptance and preference.” this included an evaluation of the shell for cleanliness, strength, texture, and shape; an evaluation of the relative viscosity of the albumen; and an evaluation of the shape and firmness of the yolk. they also measured lipid oxidation. egg fat is contained in the yolk and as eggs age the ph of the yolk material changes. this change can result in an increase in free fatty acid content and an increase in the level of the breakdown products that will result in changes in yolk flavor and can cause off-odors. this is usually measured by peroxide value (pv). in addition, the yolk membrane integrity is important for the egg breaking industry (making liquid eggs) since yolk contamination will reduce the foaming volume of egg whites.

to assure that the eggs collected for the study were the same age, they selected only egg cartons that were 15 days before the sell-by date. in the u.s., the sell-by date cannot exceed 30 days after the eggs are packed. this is not necessarily the day the eggs were laid, but simply the date that the eggs were graded and placed in the carton. this could have affected the results. with convention production, eggs are typically graded and packaged within hours of being laid. many specialty eggs are produced on contract farms with regular pickup dates so it may be 1-3 days after the eggs are laid before they are collected, graded, and packaged.

in this study, egg brands of various conventional and specialty designations were shown to produce high-quality products. brand f which was labeled as free-range and pasture-raised had the stickiest yolk among all the brands tested indicating it would not be a good candidate for egg breaking since it would result in a high level of yolk contamination of egg whites. the eggs, however, had a dark yolk meeting the consumer preference for this type of egg. however, despite a cost 4 times that of the conventional egg, the yolk and albumen content, and the yolk stickiness, does not meet the quality standards demonstrated by the other brands examined.

the conventionally-produced white eggs had the greatest increase in percent fatty acids, which could result in the production of off-flavors from hydrolytic rancidity. this may be an indicator that the eggs were handled or stored improperly at some point during the supply chain.

two of the brands analyzed were certified organic with enriched nutrient content. one of these brands had pv values above the allowed threshold indicating that they were considered unsuitable for human consumption.

this study showed that good quality eggs can be produced by all the production systems compared, but proper handling and storage of the eggs, regardless of the production system, is important to maintain that quality through the supply chain.

the article can be found online at survey of egg quality in commercially available table eggs – sciencedirect

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