Food Safety Concerns with Pork Offal
Kristin Adams, Annette M. O’Connor and James S Dickson
Iowa State University
Offal can have a wide definition, be inedible or edible, and they can also be called “variety meats” or
“brocks.” For this review, the main focus will be on the visceral organs, such as heart, liver, kidney, and
lung and will also focus upon pork (swine) offal. In 1982, it was estimated that 190,000 tons of variety
meats or offal were exported to Europe at a value of $110 million. The exportation of pork variety meats
has increased because from January to September 2014, the United States exported 384,132 metric
tons of pork variety meats with a value of $754,668,000. Despite offal being a profitable source of
revenue for meat producers, the offal produced is considered low commercial value in the United States
where edible offal consumption is low. This results in edible offal having a low priority in the US abattoir,
so they can be mishandled and are frozen before sale or distribution.
Salmonella are prevalent in edible pork offal and can cause salmonellosis. The risk of salmonellosis is
present because the prevalence of Salmonella in pork offal varies between 2% and 70%, which is a
considerable food safety hazard and concern.
Campylobacter species, such as Campylobacter jejuni and Campylobacter coli, are found on edible pork
offal. Another study reported the contamination rate of pigs livers were 28.5% (n=31) and 3.2% for
spleen and kidney (n=31), with 14.5% of the samples positive (n=93) for C. coli and 6.5% for C. jejuni.
They also reported that C. coli had a higher prevalence rate overall (30%) in organ samples than C. jejuni.
The prevalence of pathogenic Escherichia coli is unknown for pork offal for few studies have investigated
its prevalence. There was one study conducted by Zhu, W. G., S. Q. Xue in 2005 that reported that pork
lung and liver swabs had an E. coli O157:H7 prevalence rate of 0.52%.
Yersinia species, particularly Yersinia enterocolitica, has been associated or isolated from pork offal. Y.
enterocolitica is isolated from pork offal because pork is a primary reservoir for Y. enterocolitica and if
contaminated offal is consumed raw by humans, it can cause yersinosis. In one study, 80% (n=140) of
the porcine liver samples were positive for Y. enterocolitica, and most of the livers were purchased from
a retailer
Another bacterial pathogen reported in offal samples is Listeria monocytogenes. The incidence rate for
pork livers varies from 1% to 25.1% (n=171), with the most common serotype being 1/2a. Lower
incidence rates have been seen in pork kidney and lung samples, showing no L. monocytogenes present.
An Evaluation of the Suitability of Porcine Lung Tissue for Human Consumption
D.R. Woerner, D.R. Sewald, R.J. Delmore, G.L. Mason, K.E. Belk
Colorado State University
The objective of this study was to provide evidence of the safety of pork lungs for human consumption
via determining the prevalence of potentially pathogenic bacteria and infectious agents known to be
prevalent in pork. Specifically, the goal was to collect evidence that could be used to petition the current
regulation disallowing saving of pork lungs for human food. Pork lungs have been labeled by the U.S.
Meat Export Federation as a widely consumed product across Asia as well as South and Central America.
With this said, it is believed that there is profit potential in saving pork lungs and exporting them to the
specified countries. Pork lungs must first be deemed safe and edible before they can be sold on the
export market.
Lungs were collected from a total of 6 federally inspected pork processing facilities that were specific to
killing either young market barrows/gilts or sows. In an attempt to obtain a representative sample of the
production facility on an average working day, animals and corresponding lungs were randomly selected
throughout the entire production day. All of the lungs collected were removed and processed using
aseptic techniques to prevent any exogenous contamination.
The lung samples collected were tested for the prevalence of specific pathogens and other physical
contamination. The lungs did not test positive for Yersenia spp., Influenza, or Mycobacterium spp., and
they contained low yeast and mold counts. However, multiple samples that were collected from both
barrows/gilts and mature sows tested positive for Salmonella spp., Shiga toxin-producing Escherichia
coli, Campylobacter, and Streptococcus suis. Also, half of the samples collected were found to contain
physical contamination within the airways of the lungs. These results suggest that pork lungs are not
safe and should not be saved for human consumption.
Enhanced Safety and Shelf Life of US Pork Organ Meats Destined for International Trade
William Benjy Mikel, PhD
WPF Technical Services
The objective of optimizing value throughout the pork chain is now best achieved by enhancing the
value of export products that have little value to the US consumer. To further enhance pork value, these
items should be capitalized on in the export market with improved food safety and enhanced shelf-life.
In order to achieve this further added value to the pork chain, the addition of various antimicrobials to
pork variety meats was explored to determine the efficacy of enhancing the safety and the shelf life of
refrigerated and frozen liver, kidneys, hearts and lungs. Fresh pork variety meats were collected at
animal harvest, inoculated with Salmonella treated with organic and natural compounds shown to have
antimicrobial effects on other meat and poultry products (coumarin, (-) epicatechin, coumarin plus (-)
epicatechin, lactic acid, and lactic acid plus sodium bisulfate). In addition, each product was sampled for
contamination prior to inoculation and for APC to determine natural microbial load as fresh meat
products are natural reservoirs for bacterial contamination, however these levels should be minimized
during the harvest process through good manufacturing practices (GMPs) and standard sanitary
operating procedures (SSOPs) Fresh products were then stored for 0,1, 7, 14, 28, 42 and 56 days at 40F
and 28 and 56 days at 0 F before determining microbial populations. To further enhance the value of
these variety meats, a chunked and formed raw loaf was processed from liver, heart and kidney
muscles. The lung was excluded from this portion of the study due to its inability to bind to the other
meats, thus decreasing the capacity of the offal loaf. The meat chunks were cut into approximately one
cubic inch pieces, mixed with a 1.0% solution of ACTIVA TG (Ajinomoto Food Ingredients, Chicago, IL)
which contained sodium chloride, gelatin, trisodium phosphate, maltodextrin, trasglutaminase,
safflower oil (processing aid) used as a binder to facilitate product bindability to allow slicing of the
product once refrigerated or frozen. All fresh variety meats had APC populations of log 104 and
Salmonella populations in excess of Log 103 indicating contamination occurring at some point during the
harvest process. Lactic acid treatments were effective in decreasing initial contamination levels with
little impact of natural plant based antimicrobials.
Pork Harvest Plant Survey to Determine Possible Points of Variety Meat Contamination
William Benjy Mikel, PhD
WPF Technical Services
The objective of optimizing value throughout the pork chain is enhanced by improving the value of
export products that have little value to domestic consumers. Pork offal products, specifically variety
meats, are products of normal consumption for many cultures around the world. However, the initial
contamination and microbial load plays a tremendous role in product shelf life and safety. The current
project addresses the research needs to identify specific methods of organ meat contamination and
possible best management practices to avoid such. Specifically, this project attempted to determine the
opportunities during the harvest chain for potential product contamination and determine enhanced
practices that might minimize that possible contamination. Five pork harvest facilities located
throughout the Southeast and Midwest were surveyed for potential microbial contamination of offal
variety meat products. In addition, best management practices were observed to minimize product
contamination during the harvest process. At each plant data were collected to include the heart, liver,
kidney and lungs. Immediately after venting of the gut, swabs were taken of the four organs prior to
removal from the carcass. In addition, tissue samples were excised immediately post USDA inspection
for analysis of E. coli, Salmonella, and Campylobacter. When possible, scalder fluid temperature and pH
was recorded and a sample collected of analysis. Offal trays were also swabbed in two plants. Data
indicate the swabs taken immediately after venting of all the organs had less positives than organs
placed on offal pans (5 vs 14). Further, the only Campylobacter positives where from plants that skinned
vs scald plants (14 vs 0). In addition, the majority of environmental samples tested negative for
Salmonella indicating adequate sanitation in the facilities. The present study indicates that products are
less contaminated immediate after venting before products are removed from the carcass and exposed
to potential environmental cross contamination. However, situation may arise that lead to increased
contamination once the product is exposed. Diligence is necessary to ensure that proper sanitation of
product contact surfaces occurs to minimize the risk of possible cross contamination.
Impact of High Pressure Processing on Pork Organ Meats
James S Dickson
Iowa State University
The conventional approach to interventions on fresh meat products has involved the application of
washes or chemical rinses. Although these interventions are effective on surface contaminants, they are
limited by the willingness of the importing country to accept them. In addition, during the slaughter
process, some microbial contaminants may become internalized in these meats, and would not be
affected by external washes. High Hydrostatic Pressure Processing (HPP) is currently used as a post
packaging intervention in ready-to-eat meats. The advantages of HPP include its’ ability to destroy
bacteria, both spoilage and pathogens, in internal surfaces, and does not require labeling. Potential
disadvantages of the process are the operational costs and the “continuous batch” processing system.
There is no existing data within the public domain on the impact of high hydrostatic pressure processing
on pork organ meats.
Samples of liver, lung, heart and kidney were obtained from freshly slaughtered market weight hogs.
The samples were vacuum packaged and triple bagged to assure sample integrity. The samples were
processed in a Avure/Flow Pressure Systems QFB 35L-600 at ambient temperature (approximately 22oC;
samples were chilled to <5oC), at either 400 MPa or 600 MPa for 4 minutes. Processed samples were
evaluated for color, texture and microbiology, and compared to unprocessed control samples.
Color measurements were performed with a HunterLab Labscan XE, using the CIE L* a* b* scale. Lighting
was at MI illuminant D75 (Daylight at 7500K), with an observer angle of 10° and a ½ inch aperture.
Triplicate samples were analyzed with two measurements per sample. All of the organ samples
exhibited statistically significant increases in L* values (lightness) with increasing pressure, and the
samples were visibly lighter in color. The a* measurements were essentially unchanged, while the b*
values (yellow) increased with increasing pressure processes.
Texture measurements were performed with a Texture Technologies TA-XT2i texture analyzer with
Texture Exponent software, using a ½ inch ball probe set to a depth of 50% of sample height. Triplicate
samples were analyzed with two measurements per sample. With the exception of liver, peak force
increased with increasing pressure processes, indicating that the samples would likely be perceived as
“tougher” by a consumer.
Another set of samples was inoculated with a 4 strain mixture of Salmonella enterica from the ATCC MP15 panel. The individual cultures grown to late logarithmic/early stationary phase in trypticase soy broth
at 37oC, and then combined. The samples inoculated by immersion for 3 min, and then packaged. After
processing, the populations were enumerated using the Thin Agar Layer (TAL) method, with trypticase
soy agar as the non-selective medium and XLD as the selective medium. High pressure processing
reduce the inoculated populations of Salmonella enterica by -.- log10 at 400 MPA and -.- log10 at 600
MPa.
High Pressure Processing Economic Issues
James Dickson
Iowa State University
Capital Cost: As with other technologies, there are two business models. One is the construction of a
facility to be owned and used by the processor, while the other is to use a contracted service provided
by an independent contractor. Unless a very large quantity of product is to be irradiated continuously,
most processors rely on contracted services.
A commercial processing unit, such as those manufactured by Avure Technologies, would be in the $2$4 million price range. Since most facilities have a minimum of two machines, this cost would double the
cost to $4 to $8 million.
There are companies which contract high pressure processing services, such as the Universal
Pasteurization Company in Lincoln NE. As with other technologies, the cost will be dependent on the
volume of product to be processed, the length of the contract and the processing parameters of the
product. A higher volume of product over an extended period of time (e.g., one semi-truck load every 10
days, on a one year contract) will result in a lower cost per pound than a smaller amount on a shorter
contract. An estimated cost would be approximately $0.20/pound, but actual costs may be higher.
Commercial Examples: Rapidly gaining acceptance in the meat and poultry industry as a post-packaging
lethality process. Hormel processes much of their ready-to-eat meats in a corporate-owned facilities.
Based on their success, other processors are seriously evaluating the process. The process is also in
commercial use for raw oysters, and one national seafood restaurant chain only serves high pressure
processed oysters in their raw oyster menu items. Historically, high pressure processing was used for
high value juice products in Asia.
Economic Analysis:
Capital costs for two units are in the $4 to $8 million dollar range. Using a $6 million dollar average, a
10% depreciation rate and a 10% required return on investment the annual capital cost is approximately
$600,000. Compare this to a third party fee of $0.20 per pound and the breakeven annual quantity is
1,500 tons. The most likely business model would be for a company to contract the process out until this
break even value is reached. Then as volume increases purchase the two units and cause processing cost
to fall well below $0.20 per pound as volume exceeds 1500 tons.
Most of the customers who import liver, hearts and kidneys meats are price conscious and are willing to
purchase frozen products. Few of these customers will be willing to pay $0.20 to avoid freezing.
Moreover, the cost of shipping chilled as opposed to frozen product is about $0.15 per pound higher.
This addition cost is due to the need to monitor chilled cargo to avoid spoilage. It seems unlikely that the
market will bear this additional cost at this time. However there may be other variety meats where
freezing damages the quality the product to the point where the required premium would be
sustainable.
Pork muscle meat that is frozen must typically be discounted by 30%, or approximately $1/lb. in Asia. If
high pressure processing can extend shelf life in markets such as Singapore and Malaysia where transit
distances preclude shipping chilled pork then process will more than pay for itself. This seems like a
fruitful area for additional research.
Pork Fibrin Used as a Meat Binder in Pork Variety and Offal Meats
D.R. Woerner, D.R. Sewald, G. Sisney, R.J. Delmore, K.E. Belk
Colorado State University
The objective was to conduct a proof of concept for the use of fibrin from pork blood to create valueadded export items from various pork offal items and variety meats. Fibrin is a cold set binding product
that is created by recombining the two blood components thrombin and fibrinogen. The fibrin can then
be added to fresh meat to bind multiple products together into one. Fibrin is currently marketed as
Fibrimex® by Sonac, however, the patent for producing fibrin has expired which leaves the potential for
U.S. pork operations to begin to produce their own fibrin and add it to certain pork items to create their
own value-added products.
A total of eight finished products were created in this study using only Fibrimex® and pork offal/variety
meats. The products created include a boneless baby back made from pork jowl, a steak made from
diaphragms, a boneless hock, a log of skinned pork tongues, a pinwheel with pork diaphragm and
cheese, a steak made from course ground heart and back fat, fresh bacon made from pork jowl, and a
bung roll stuffed with liver, heart, and kidneys. These products are examples that show the binding
capabilities of fibrin on different textured meats. All of the final products are believed to have potential
as successful export items. It must be noted though that fibrin can be added to many other meats to
create an endless number of products, including products that are of value within our country’s own
markets.
List of products to be evaluated in this study.
Bladders
Hocks
Skins
Brains
Intestine
Spleens
Diaphragm (skirt) meat
Jowls
Stomachs
Ears
Kidneys
Tails
Esophagus
Lips
Tendons
Face Mask
Livers
Tongues
Fat- Back
Pancreas
Trachea
Fat - Leaf
Pizzles
Salivary Glands
Rectum
Hearts
Tunic
Aseptically Packaged Emulsified Pork Products Preserved by Advanced Thermal Processing –
Feasibility Study
Dana J. Hanson
North Carolina State University
Continuous flow microwave technology has been developed at North Carolina State University for
sterilization of foods and biomaterials. Processing of meat pates and other comminuted meat products
that are commercial sterilization and thus stored and distributed under ambient (room) temperature
conditions is common in Europe, Asia and other parts of the world. Currently this process represents a
very small market segment in the United States. Processing and packaging of liver pate type products to
achieve commercial sterility could be used to increase the consumption and particularly export potential
of these products.
Dielectric properties of pork trim, organs and pork pate products have been measured and evaluated for
potential compatibility with the emerging continuous flow microwave technology for thermal
sterilization of foods. Properties were measured for both industrially relevant microwave frequencies
(915 MHz and 2450 MHz) and within a temperature range encompassing refrigeration (10C) to
sterilization (120C). Test material properties followed the general trends observed previously for other
foods. The addition of salt was related to the increase in dielectric loss tangent in test formulations,
especially in the 915MHz range. Further experimental studies are recommended to define the
processing parameters and ranges for these products more precisely.
Continued research and development is anticipated to yield, in addition to the emulsifies pork organ
based shelf stable product lines in aseptic packaging, also more complex and higher grade products like
sausage in gravy, spaghetti sauces, chili sauces and taco and burrito meat based sauces, plus sauces and
gravies containing larger cut pork meat pieces – chunks or cubes.