A very appropriate subject if indeed pork is to become the "Meat
of Choice" by the millennium. Of course we need to bear
in mind that pork is already the most consumed muscle food of
animal origin on a global basis as we speak. Pork quality has
been researched, described, cussed and discussed for well over
fifty years, and we still find ourselves conducting conferences
trying to figure out what it is as if it was a single entity in
mere need of description and at which point the needs of all segments
of the industry ranging from production through consumption would
be met. The Pork Chain Quality Audit (1994) thoroughly reviewed
the multiple factors involved in the evaluation of pork quality
with the exception of bacteriological safety. The National
Pork Producers Council (1997) hosted a conference earlier this
summer under the banner "Quality Summit," again with
little attention paid to food safety but with excellent and extensive
reviews of the technologies of physical pork quality assessment
and progress on the implementation of known technologies in industrial
settings. I commend both to your review as excellent sources
of material in the multiple facets of the "Quality"
WHAT IS MEAT QUALITY?
Meat quality is a variable trait of which the definition depends
on whose needs are to be met. The target is a consumer product
which delivers safety/wholesomeness, and tenderness, juiciness
and flavor (palatability traits). Greer (1988) and Kauffman et.
al. (1969) defined meat quality as including a combination of
traits that provide for a wholesome product that loses a minimum
of constituents during handling, is free of spoilage and other
abnormalities after processing and storage, is attractive in appearance,
maintains a natural, healthful image, is convenient to prepare
and appetizing, nutritious and palatable to eat. Kauffman et.
al. (1990) suggests three levels of quality. The survival
level demands that wholesomeness, as it affects safety and image,
and nutrition as highlighted by proteins, vitamins and minerals,
be maintained permanently in place. The economy level
includes, in addition to wholesomeness and nutrition, minimum
shrinkage during processing as affected by pH, and proper cooking
conditions. Finally, the ideal level includes all characteristics
of the survival and economy levels but insists on attractiveness,
as controlled by color, convenience and consistency, and the ultimate
in juiciness, tenderness, flavor and texture. Satisfying these
levels requires five discussion categories of: wholesomeness,
nutrition, shrink, appearance and palatability (tenderness, flavor
and juiciness). Measures most often used in the assessment of
the tissue are: pH, drip loss (water holding capacity), shear
values, color (uniformity) and marbling. Wholesomeness (freedom
from contamination), consistency, and nutrition are more akin
to standards of identity and strongly influence consumer purchase
decisions in ways difficult if not impossible to accurately measure.
Wholesomeness / safety
Not always thought of as a trait of meat quality, the safety from
a food-borne illness potential perspective has become increasingly
important. The pork industry cannot afford the bad publicity
of food poisoning outbreaks. USDA needs to continue as a strong
(reasonable) advocate pursuant with the objective of limiting
the occurrence of cross-contamination. Keep in mind that, in
the absence of infection or disease, muscle is essentially a sterile
tissue until processors make it available to contamination. Abscesses
(which are primarily of producer origin and often due to poor
injection technique, equipment, etc.) are the leading cause of
condemnation or trimming loss initiated during the postmortem
inspection process (Cannon et. al., 1994). Healthy product originates
from healthy animals. Contamination is the fourth leading cause
of condemnation and the most common cause for necessitated trimming.
HACCP must be at the forefront of processing procedures. What
are the "critical control points" and how do we modify
procedures? In the distribution of fresh product, contamination
must be held to a minimum and handling (and storage) procedures
must minimize the opportunity for the growth of pathogens and
food spoilage organisms as well as minimizing deterioration such
as oxidative rancidity. Products distributed as "fully cooked"
must provide a kill step without opportunity for recontamination.
Simultaneously, USDA needs to be reasonable (science based) in
approaches to sanitation and recall procedures.
Nutrient contribution and eating enjoyment rank as dominant support
factors for the inclusion of meat in the human diet. Lean muscle
foods have long been recognized for their nutrient density. Again,
healthy product comes from healthy animals. The avoidance of
undesirable conditions like PSE, the product of which shrinks
excessively before and during processing thereby losing water
soluble nutrients, and excessive fat (more than 5% in fresh meats
and more than 20% in processed) helps position muscle foods in
a nutritious lifestyle.
Arguably, the single most important factor in the evaluation of
meat quality, the ability of muscle (meat) to retain its own or
added moisture is related primarily to the factors of pH and protein
denaturation. Postmortem pH decline and myofibrillar protein
denaturation are thought to be responsible for the softness and
accelerated drip loss of PSE meat (Forrest et. al. 1997). Forrest
et. al. (1997) report that water in meat is primarily contained
in the myofibrillar lattice and as the pHu drops near the isoeletric
point (5.0 - 5.1) of myosin and actin, water-binding capacity
is at a minimum. Therefore, higher pHu values result in greater
net charges on muscle proteins and greater percentages of bound
and immobilized water, keeping natural juices bound in the cells
and reducing drip loss. The degree of denaturation of sarcoplasmic
and myofibrillar proteins (attributed to low pH and high temperature
during the early postmortem period) is believed to contribute
to an increase in extracellular space and surface wateriness.
Systems which minimize the rate and extent of postmortem pH decline
will have a positive effect on the ultimate water - holding capacity
of muscle. In addition to the genetic influence or susceptibility
to stress (Porcine Stress Syndrome, RN gene, etc.), a remaining
factor in the tendency for the development of PSE is that muscles
that are high in the "Type II" fiber type, being more
metabolically glycolytic, are more subject to the condition -
a factor in both swine and poultry.
Everything effects appearance in muscle foods ranging from age
and abnormalities through composition, presentation, processing,
and stress. PSE product is prone to early color deterioration
in addition to purge or free exudate in packaging while DFD product
which is considered off color because of its dark color is prone
to more rapid microbiological deterioration because of its more
neutral pH. The age of animals within a specie influences color
attributed to myoglobin accumulation while species possess their
inherent differences as well. Product appearance is largely a
function of processing as well, including control of fat content
in processed products, trimming and deboning level in fresh meats
and the use of additives such as nitrite. Finally, the avoidance
of abnormalities such as blood splash, steotosis and discolored
fat is essential if muscle foods are to portray a positive image
in the market. Packaging, presentation and marketing are very
often among the most rewarded components in the market chain.
Tenderness, flavor and juiciness, the traits most often used in
the definition of ultimate quality are all difficult to objectively
assess by virtue of the fact that the ultimate testing machine
is a human. Humans are quite variable in their responses and
given to error and inconsistencies, thus the dependency on tools
like the Warner Bratzler Shear and Instron. Of course this isn't
the only place that humans present problems in the determination
of quality of muscle foods. Among the most common predictors
of meat quality you won't find any that provide a greater correlation
to final eating quality than 0.50. The statisticians among us
will go on to explain that this means those very same predictors
explain less than 25% of the variation in palatability. Method
of preparation (Is it cooked right?) is the single greatest contributor
to palatability. The challenge for processors is to provide a
product which is complete in the other components of quality and
which is easily prepared on a consistent basis.
Tenderness is the trait generally listed to be the dominant of
the three palatability traits. Of the most consumed animal tissues,
beef is the most highly variable. This tendency is largely explained
by the degree of variation in the age of cattle (steers and heifers)
at the time of slaughter which easily ranges from 12 to 26 months
and beyond, combined with the variable post-slaughter (aging)
time to consumption ranging from 5 to well beyond 30 days. Advancing
animal age leads to greater connective tissue content and greater
crosslinking of that tissue, while aging of the carcass or cut
allows for proteolytic enzymes to degrade muscle proteins leading
to increased tenderness. Tenderness in poultry and pork is less
of a problem given the more consistent and youthful age at harvest.
Here again the water holding capacity of the tissue is a major
contributor to the tenderness profiles of products from all of
Flavor and juiciness tend to parallel each other in most consumer
tests. Generally, as juiciness goes, so does flavor perception.
Again, as a function of water-holding capacity and processing,
the ability of a product to retain its own or added moisture play
a major role in the flavor / juiciness profile. Recognition is
due with respect to the impact of specie on flavor but with increased
leanness in a number of product offerings accompanied by spices
and flavors, little of the flavor profile of many products has
anything to do with the specie of origin. Does it matter?
PRACTICAL MEAT QUALITY TECHNOLOGY
Opportunities to modify meat quality parameters takes place at
many points along the production chain leading from animal production
all the way through to the final consumed product. Following
is a partial review of a number of efforts and techniques that
occur at the various stages of meat production. The list is not
exhaustive but attempts to highlight and touch briefly on some
of the more often used processes and some that appear promising.
Efforts will continue to identify stress prone animals whether
through halothane testing or via work on identification of the
RN gene in various lines of swine which others in this conference
are covering in its entirety. The influence of stress susceptibility
(excitability) and ultimately less desirable meat quality is not
limited to hogs and poultry. Voisinet, et. al. (1997) demonstrated
a negative relationship between cattle temperament and beef quality
traits of color and tenderness. Without doubt, animals (especially
hogs and poultry) benefit from a rest period following shipping
and prior to slaughter. In work by van der Wal, et. al. (1997)
the length of resting period was negatively related with the temperatures
of the m. longissimus and m. semimembranosis at
45 minutes postmortem, while the ultimate pH values, at longer
periods of lairage, were significantly higher in combination with
a darker color according to Hunter L* values and a color scale.
Data supported the hypothesis that stress immediately prior to
slaughter affects meat quality much more than stress experienced
earlier on. In the same work the relationship between proper
stunning of the live hog was associated with a decreased incidence
of aberrant quality. Incorrect stunning procedures resulted in
an increase in muscle activity during shackling and exsanguination,
an earlier onset of rigor mortis, lower initial pH values
and ultimately lower water-holding capacity in the product. A
wide array of work has and is being done on the feeding of various
compounds for the improvement of color (Work originally done at
the University of Wisconsin, with vitamin E supplementation in
cattle, has shown marked improvement in color stability resulting
in increased shelf life for beef.), tenderness (Preliminary work
with vitamin D by researchers at Colorado State has suggested
improvements in beef tenderness.) and leanness (Researchers at
the University of Wisconsin are in the early stages of work with
conjugated linoleic acid - CLA - which is showing great promise
in the improvement of carcass leanness in swine.). A number of
other compounds, administered through either injectable or oral
routes of administration, have been and are being researched generally
with objectives of enhanced efficiency or rate of lean growth.
Lean quality, in terms of tenderness, juiciness and flavor, are
unfortunately often reduced in such scenarios.
The primary technology which is applied during the slaughter process
is that of electrical stimulation (ES). ES has been utilized
very effectively in beef and lamb slaughter plants and the list
of its benefits includes: enhanced lean color (thereby increasing
Quality Grade), decreased incidence of cold shortening (resulting
in increased tenderness) and increased blood yield at exsanguination.
ES works primarily by accelerating the cascade of postmortem
reactions in muscle including rapid pH decline. Thus, the fairly
obvious reason that the same technology does not work well in
the processing of pork.
In pursuit of increased wholesomeness / safety, slaughter technologies
that have gained momentum in the beef industry are the use of
steam pasteurization and organic acid spray washes for the purpose
of beef carcass decontamination. Both technologies have been
shown to decrease the levels of bacteria, including E. coli 0157:H7
and Salmonella species, but do not result in complete elimination.
Technology is rapidly advancing which provides for the sorting
of products into known and established quality categories. The
work by Morgan and Forrest (1997) shows great promise in the sorting
of products by a color vision system. The result of which could
be the separation of products which could be distributed "fresh"
and those which could be distributed as "less expensive"
or undergo "quality enhancement." Additionally sited
is work with a tetrapolar impedance probe which shows promise
of being able to predict ultimate meat quality as early as 36
minutes after slaughter. Currently available technologies are
limited to sorting pork into the extremes, which still leaves
the problem of exudative pork of normal color. Kauffman (1997)
reported the ability to sort carcasses in to the quality categories
of "desirable" and "undesirable." Why not
take advantage of that ability and market the products accordingly?
The beef industry has in place a system for the categorization
of fresh beef into different "quality" groups via USDA,
while pork in many systems of distribution is just "pork."
In response to continuing concerns about the inconsistency of
beef, Boleman, et. al. (1997) researched the tendencies of consumers
to pay premiums for beef of guaranteed tenderness and found willingness
to pay premiums approaching 10 to 20 %. In associated work, Shackelford
and coworkers (1997) are developing a system for the early (24
hour postmortem) classification of beef according to tenderness
class. The proposed system utilizes a Warner-Bratzler Shear to
evaluate beef loin steaks at 1 or 2 days postmortem to predict
tenderness following 14 days aging.
The most commonly recognized "processing" techniques
for the improvement of pork (and poultry) quality are the use
of "rapid chilling" and moisture enhancement. Rapid
chilling of the carcass has been shown to decrease the severity
of the PSE condition, by slowing postmortem glycolysis rates,
but not prevent it. However, carcasses (musculature) predisposed
to extremes in PSE have already been exposed to the low pH / high
temperature muscle conditions responsible for development of the
condition. Moisture enhancement (injection with solutions of
salt, sodium phosphate, etc.) has been used in the poultry (turkey)
industry for many years and has more recently been effectively
applied to "normal quality" pork products to provide
products that excel in juiciness, flavor, and tenderness. The
use of salt or sodium phosphate increases the water-holding capacity
of meat so when injected in solution, provides the benefits of
moisture and flavor (salt is an enhancer). The tenderness factor
is accounted for via greater moisture retention, dilution of protein
and the fact that water is tender.
More recently, work at the University of Wisconsin - Madison (Russell,
et. al., 1997) has shown positive effects from the early identification
of PSE pork and intervention treatments with sodium bicarbonate
(baking soda) in a saline solution. The buffering capacity of
the bicarbonate counteracts the rapid pH decline of the musculature
resulting in a product that is elevated from PSE to normal or
"ideal" quality. Combine this ability with early detection
of PSE prone carcasses (Morgan and Forrest, 1997.) and the potential
exists to greatly reduce the negative impacts of PSE. Flavor
tended to be improved but not to the degree of statistical significance.
Finally, with respect to processing treatments that influence
meat quality (wholesomeness), at the time of this writing, FDA
announced approval of the use of irradiation of meat for pathogen
control. Irradiation has been approved for use in poultry for
some time. The use of this technology has the potential to greatly
reduce the incidence of food-borne illness, but has to overcome
the large obstacles of cost and consumer fear. At the same time,
the ability to destroy E. coli 0157:H7 and Salmonella species
in fresh meats without other deteriortative effects to the product
is no substitute for sanitation during processing and preparation.
Cross-contamination remains as a major source of bacteria which
contribute to illness as well as spoilage.
The primary purpose of packaging is maintenance of the product
in as near its original condition as possible. Vacuum packages
have the problem of visual purge which is of course exacerbated
by poor water-holding capacity of the original product. However
the protective role against oxidative rancidity is of great benefit.
Work with the development of modified atmosphere packaging continues
with the goal of finding the right combination of gasses to provide
for color stability as well as protection against oxidation.
Jeremiah and Gibson (1997 a,b) have demonstrated the usefulness
of 100% CO2 atmospheres in the maintenance of color
stability in pork loin roasts stored for extensive periods at
sub-zero storage conditions (below 0 C, but above the freezing
point of the tissue), while atmospheres of 70% O2 and
30% CO2 were the most effective in the avoidance of
off-odor development. Composite results clearly emphasized the
importance of sub-zero storage to the retail properties, and storage
life of pork for all the types of storage atmospheres utilized.
Both studies were conducted because for centralized processing
and packaging of pork cuts to be effective, the chilled storage
life of such cuts needs to be extended sufficiently to permit
widespread distribution and merchandising.
The first criteria any perishable product must feature is that
of safety. Food safety (hysteria) has become intrinsic to the
consideration of nutrition sources, especially those of animal
origin. Secondly, products must be palatable and preparable ("user
friendly"). Palatability is a feature any product needs
to sustain or improve consumption rates, while the ease of preparation
has become an ever increasing criteria in food selection. Nutrition
(defined in many consumer minds as a product which is not too
fatty, but very subject to niche tendencies, while being considered
an important source of protein) which has often been touted as
a primary feature to stimulate consumption appears to be of lesser
importance but still relevant. Features of "price/value,"
"brand loyalty," "source verified product,"
"organic," etc. are features around which consumers
have a confidence, loyalty and/or trust based on knowledge, experience,
or belief. Ultimately, a blend of all of the preceding come together
in buying decisions with nearly as many different priorities as
there are consumers.
Where do we go?
I commend to you reading the best selling book: The 7 Habits
of Highly Effective People by Stephen R. Covey. While not
being a read on meat quality, the principles contained within
may be applied to personal management as well as organizations.
Habit 1: Be Proactive.
Think outside the box and don't let fear of the unknown keep you from looking into possibilities. Virtually every thing we do is by choice. Just do it!
Habit 2: Begin with the end in mind.
Define your objectives before just starting in helter skelter. What is the market? How can we adapt?
Habit 3: Put first things first.
Plan and organize. Determine your priorities and let the rest slide. If you're preoccupied with pleasing everyone or doing everything, you'll please no one and get nothing done. The main thing is to keep the main thing the main thing.
Habit 4: Think win-win.
The delivery of a "consumer preferred" product is win-win for the swine industry. Too often the adversarial relationship between producers/packer/retailers has contributed to a finger pointing blame game. Win-win or no deal.
Habit 5: Seek first to understand, then to be understood.
Listen. An industry that is preoccupied with "educating" the consumer is an industry in trouble. What do consumers want? Dollars spent out of the home for food have increased dramatically over the past decade and all indications are that in our growing economy, the trend will continue.
Habit 6: Synergize.
Capitalize on the strengths of diversity of abilities. Already evident in many segments of the industry at the producer level. Professionals (academics) are getting better, but are slow learners.
Habit 7: Sharpen the Saw.
Research must continue with emphasis on food quality with safety
assurance. Read the literature. Regenerate. Learn from others
Boleman, S.J., S.L. Boleman, R.K. Miller, J.F. Taylor, H.R. Cross, T.L. Wheeler, M. Koohmaraie, S.D. Shackelford, M.F. Miller, R.L. West, D.D. Johnson, and J.W. Savell. 1997. Consumer Evaluation of Beef of Known Categories of Tenderness. J. Anim. Sci. 75:1521-1534.
Cannon, J.E., J. Heavner, J.B. Morgan, F.K. McKeith and G.C. Smith. 1994. Pork Chain Quality Audit: A Review of the Factors Influencing Pork Quality. Manuscript No. JMF-21-94-1. NPPC. Des Moines.
Covey, S.R. 1989. The 7 Habits of Highly Effective People. Simon and Simon Pub. New York.
Forrest, J.C., E.B. Sheiss, M.P. Morgan and D.E. Gerrard. 1997. Pork Quality Measurement Tools - Now and In The Future, Proceedings NPPC Quality Summit, Des Moines, IA. July 7-8, 1997.
Greer, G.G. 1988. Bacteria and Meat Quality. Can. Inst. Food Sci. Technol. J. 22:116.
Jeremiah, L.E., and L.L. Gibson. 1997a. The Influence of Storage and Display Conditions on the Color Stability of Display-ready Pork Loin Roasts. Meat Science. Vol. 47, No. 1/2, 1-16.
Jeremiah, L.E., and L.L. Gibson. 1997b. The Influence of Storage and Display Conditions on the Retail Properties and Case-life of Display-ready Pork Loin Roasts. Meat Science. Vol. 47, No. 1/2, 17-27.
Kauffman, R.G. 1997. National Pork Quality Project, A Final Report to The National Pork Producers Council, Proceedings NPPC Quality Summit, Des Moines, IA. July 7-8, 1997.
Kauffman, R.G., W. Sybesma and G. Eikelenboom. 1990. In Search of Quality. J. Can. Inst. Food Sci. Technol. Vol. 23, No. 4/5.
Morgan, M.T., and J.C. Forrest. 1997. Color Vision System and Tetrapolar Electrodes for Assessing Pork Quality, Proceedings NPPC Quality Summit, Des Moines, IA. July 7-8, 1997.
Russell, R.L., R.G. Kauffman, M.L. Greaser, C.A. Cornelius, C.E. Suckow, and R. van Laack. 1997. Can PSE be Prevented by Injection of Sodium Bicarbonate into Pork? Abstract. ASAS/ADSA Meetings Midwest Section, Des Moines, Iowa. March 16-19.
Shackelford, S.D., T.L. Wheeler, and M. Koohmaraie. 1997. Tenderness Classification of Beef Longissimus Shear Force at 1 or 2 Days Postmortem as a Predictor of Aged Beef Tenderness. J. Anim. Sci. 75:2417-2422.
van der Wal, P.G., B. Engel and B. Hulsegge. 1997. Causes for Variation in Pork Quality. Meat Science. Vol. 46, No. 4, 319 - 327.
Voisinet, B.D., T. Grandin, S.F. O'Connor, J.D. Tatum and M.J.
Deesing. 1997. Bos Indicus - Cross Feedlot Cattle with
Excitable Temperaments have Tougher Meat and a Higher Incidence
of Borderline Dark Cutters. Meat Science. Vol. 46, No. 4, 367