Troubleshooting

Understanding recent color changes in pork (Pt. 1): A processor's perspective

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By Meatingplace Editors on 3/28/2016

The characteristic pink color of ham has always played a significant role in consumer preference for ham. Consumers prefer the color to have a generally uniform pink color without extreme light or dark colored areas.

Historically, problems associated with undesirable cured ham color would have been attributed to poor raw material selection (such as selecting different muscles in the ham that are light or dark color) or compromised manufacturing procedures (failure to develop cured pink ham color).

Beginning in 2011, Oscar Mayer began to notice an unusual increase in the number of consumer complaints associated with ham color. Complaints to the company ranged from concern over discoloring -- “This time the ham is discolored, pink then ½ very dark” -- to concern over light coloring -- “The ham was white in areas. It looks like the color was washed off. It was unappetizing.”

Two key observations made

A deeper investigation uncovered that the general color of ham indeed has become lighter compared to previous years.

In 2013, color data collected on a market basket sample of cured ham which found the colorimeter L* value to be 66.1 while the L* value of a turkey breast and white product was 71.6 (using data collected by PHD technologies and Oscar Mayer). The L* scale goes from 0 to 100 with 0 being black and 100 being white. The average human eye is able to observe L* color differences of about two L* units or greater.

Alarmingly, the market basket color of ham in this “snaphot” scenario was much closer to a white-colored turkey breast and white turkey product than many people familiar with the meat industry may expect.

One potential cause of light colored ham may be poor pink ham color development during manufacturing. However, an investigation at Oscar Mayer into the technical cause of the consumer complaints about ham color quickly determined that product was being manufactured correctly.

Next, a closer evaluation of the ham muscles revealed that there were two undesirable color observations:

The color of some muscles were quite light (although not watery or not showing any PSE properties); and
The skin side of the outside (biceps femoris; 9) ham muscle was light in color compared to the center and bone side of the biceps femoris. The light-colored ring on the skin side of the biceps femoris began to be referred to as a “halo.”

The halo effect

After concluding that the color problems were not being caused by manufacturing procedures, Oscar Mayer turned its attention to supply points.

Beginning in 2012, about 400 hams were evaluated across several suppliers to try to find the cause of the light colored halo. Oscar Mayer investigated several hypotheses:

Chilling method is affecting outside surface ham color: snap chill, -20F vs. standard chill, 9F;
Stunning method affects outside surface ham color: electric stunning vs. CO2 stunning;
Aggressive scalding is affecting outside surface ham color.

Data was collected on 400 hams for visual presence of a “halo,” or light-colored muscle, on the skin side of the biceps femoris muscle. If a halo was present, the depth of the halo into the muscle was categorized as <1/2”, ½” or >1/2.” Heme concentration, water binding, cook yield and pH data were collected on the muscles.

After visiting several suppliers, the “halo” was observed in all supply locations, and neither chilling practice, stunning practice nor scalding procedures had any impact on the presence of a halo.

Combining all treatment effects observed at all suppliers visited, 61 percent of the hams had a “halo” present. Of those that had a halo, 75 percent of them were less than half an inch thick, and only 5 percent were greater than half an inch thick.

% Hams with Halo across all suppliers	% Halo Hams < ½”	% Halo Hams ½”	% Halo Hams > ½”
61.0%	75.0%	20.0%	5.0%

When the impact of scalding was investigated, the biceps femoris muscle was examined after exsanguination, but prior to scalding. Interestingly, the “halo” was observed immediately in the warm, pre-rigor muscle.

Therefore, researchers concluded that the “halo” color defect in the biceps femoris was being caused not by various harvesting methods or ham manufacturing procedures, but rather something else – either nutrition, genetics or environment – that occurred before harvest of the pig. Perhaps the color defect has always been there.

Even though it was not part of the original project scope, an opportunity arose to evaluate populations of hams from pigs fed ractopamine and pigs not fed ractopamine; both populations had hams with the halo defect that was of equal severity.

Muscle from the biceps femoris was visually sorted into one of four groups for further evaluation based upon color differences that are obvious to the human eye.

No halo present, but muscle still light in color.
No halo present, but muscle dark in color.
Muscle from the halo portion of the biceps femoris.
Muscle from the non-halo portion of the biceps femoris.

Running out of leads

Examination of some of the physical characteristics of biceps femoris muscle from any of the four color groups showed that there was not an obvious or meaningful difference in the pH, water holding capacity or cook yield of the muscle.

The fact that there seemed to be minimal differences in the muscle's ability to function or hold water was perceived as positive from the perspective that there were no muscle properties that would be considered characteristic of PSE (pale, soft and exudative) muscle except for the light color of the muscle.

However there were large differences in the hemoglobin content of the muscle from the four different color groups. Muscle from the “halo” portion of the ham had the lowest amount of hemoglobin, followed by light-colored muscle from hams without a “halo” present. The muscle with the highest amount of hemoglobin was the dark-colored muscle from a ham that did not have “halo” colored muscle. Generally, the darker the muscle tissue appeared, the more hemoglobin it had.

Ham Muscle Color Group	Heme (ppm)
‘halo’ ham, dark colored muscle	55.22
‘halo’ ham, muscle from the ‘halo’	33.49
‘Normal ham’ dark colored muscle	73.33
‘Normal ham’ light colored muscle	44.99

A small subset of samples also was measured for fiber type (n=40). The fiber types of the samples tended to follow a similar trend in which light=colored muscle had less slow, oxidative fiber types and more fast, non-oxidative fiber types. It is expected that white or fast fiber types contain less myoglobin.

The fact that large intramuscular color variation was observed within the biceps femoris across the pig population challenges a commonly held ham processing conception that quality, high-functioning ham muscles are dark and uniform in color.

It is also interesting that one muscle (the biceps femoris in this case) phenotypically expresses muscle color or myoglobin content so differently, even though the muscle cells within the muscle would seemingly have the same genetic content.

What roles do nutrition and environment play in this?

Probably the biggest question revolves around whether the issues with ham color have had an economic impact on the pork industry. A look at cold cut consumption trends indicates that ham consumption has fallen about 50 million pounds over the last 10 years.

The potential domestic value of the 50 million pounds would be more than $250 million dollars if the average 2015 ham retail price of $5.32 is applied.

Industry impact

One may assume that ham consumption has declined because consumers have chosen turkey on perceived health benefits, but the trend for turkey consumption over the last 10 years has remained nearly flat.

Why has ham consumption declined? Is there a chance that consumption has declined because ham doesn’t look the way consumers want it to? Is the pork industry producing pork that consumers want?

(Editor's note: Part 2 of this series examining current and ongoing research into the color changes in pork will be available at Meatingplace online beginning April 4.)