Standard test may miss food ingredients that cause milk allergy

Joseph L. Baumert, Ph.D., who headed the study, explained that thermal and non-thermal processing of foods can change the proteins responsible for milk allergy in ways that make the proteins harder to detect using the standard test, termed the enzyme-linked immunosorbent assay (ELISA). Processing, however, may still leave the milk proteins capable of causing itchy skin, runny eyes, wheezing and other sometimes more-serious symptoms of milk allergy, despite the inability to detect the milk residue.

"The results of these studies could be utilized by commercial ELISA kit manufacturers to aid in improving ELISAs for detection of milk residue in processed food products. These improved tests can be adopted by the food industry, if necessary, to allow for reliable detection of milk residue regardless of the type of processing that is used," he said. "These improvements should not result in commercial tests that are more expensive or difficult for food processors to use."

Food processors use the ELISA to assure that processed foods that do not contain milk and processing equipment in facilities that process milk products are free of milk allergens, the substances that can trigger milk allergy.

Milk allergy is not the same as lactose intolerance, a condition in which people lack adequate amounts of the enzyme needed to digest lactose, the main sugar in milk. Lactose intolerance involves the digestive system, with symptoms like bloating, stomach cramps and diarrhea, after consuming milk or milk products. Milk allergy affects the immune system and can cause swelling of the throat, which makes it difficult to breath, and other symptoms that require immediate medical help.

Baumert explained that manufacturers and food-safety agencies use ELISAs to ensure that food-processing equipment and finished products are free of allergens or labeled with appropriate warnings. ELISAs are one of the most widely used diagnostic tests in the world today, a mainstay in everything from diagnosing pregnancy and detecting the AIDS virus in human blood to diagnosing a range of other diseases in plants and animals. The tests leverage the amazing ability of antibodies, proteins formed by the body's immune system, to attach to and mark for destruction bacteria, viruses and other foreign substances. An ELISA kit for milk proteins contains antibodies that bind to milk proteins that may be in a finished food product or on the surface of shared manufacturing equipment. If a sample taken from a finished product or from the surface of food-processing equipment contains milk residue, a color change will occur in the test, indicating a positive result for contamination with milk proteins.

Baumert, who is with the University of Nebraska-Lincoln, explained that heating and other processing of foods can make milk proteins aggregate together so it is difficult to get the milk proteins into solution, which enables them to be detected by the antibodies in ELISAs. The clumping, however, does not necessarily destroy the protein's ability to trigger an allergic reaction in sensitive people. Clumped-together proteins also would be likely to maintain their potency once they reached the human body, he added. Heating and other processing can also alter the structure of the protein, which can affect the ability of the antibody to bind to the milk proteins. Alteration in the protein structure does not necessarily mean that the milk proteins become non-allergenic for the majority of milk-allergic individuals.

His team studied and documented how ELISAs perform on several measures of accuracy when milk proteins undergo changes in foods that are boiled, baked, fried or heated in other ways. The results could help the food-processing industry and ELISA manufacturers make changes that better protect consumers with milk allergies, he said, noting that other scientists are doing similar research on foods that contain eggs and peanuts — both common causes of food allergy.

More information:
Abstract
Commercial enzyme-linked immunosorbent assays (ELISAs) are commonly used by food industry for validating removal of allergenic residue from food contact surfaces and detection of allergenic residue in finished products. ELISAs are the method of choice due to their specificity, sensitivity, and ease of use in an industrial setting, however, limited validation of ELISA kits has been conducted on food matrices that have undergone thermal processing. This is important to note when selecting a commercial milk ELISA for monitoring allergenic residues as several variations in formats (qualitative and quantitative assays), specificity (detection of total milk protein, casein, or beta-lactoglobulin), sensitivity, and reporting units (NFDM, skim milk powder, casein, beta-lactoglobulin) exist. Milk proteins can be differentially affected by thermal processing thus limiting detection and affecting overall risk-assessment decisions. The effects of common processing techniques (boiling, baking, frying, retorting, and UHT) on detection of milk residue using commercial ELISAs will be discussed.

Provided by American Chemical Society (news : web)

New standard for vitamin D testing to ensure accurate test results

Karen Phinney and colleagues explain that medical research suggests vitamin D deficiency or insufficiency may be even more common than previously thought and a risk factor for more than just bone diseases. An estimated 50-75 percent of people in the U.S. may not have enough vitamin D in their bodies. Low levels of vitamin D have been linked to the development of several conditions, including rickets (soft and deformed bones), osteoporosis, some cancers, multiple sclerosis and Parkinson's disease. People can make their own vitamin D simply by rolling up their shirt sleeves and exposing their skin to sunlight. But for those cooped up in offices all day long, food and dietary supplements also can provide vitamin D. With this renewed interest in vitamin D, scientists need an accurate way to measure its levels in the blood. Measuring vitamin D itself doesn't work because it is rapidly changed into another form in the liver. That's why current methods detect levels of a vitamin D metabolite called 25(OH)D. However, the test methods don't always agree and produce different results. To help laboratories come up with consistent and accurate methods, the researchers developed a Standard Reference Material called SRM 972, the first certified reference material for the determination of the metabolite in human serum (a component of blood).

The researchers developed four versions of the standard, with different levels of the vitamin D metabolites 25(OH)D2 and 25(OH)D3 in human serum. They also determined the levels of 3-epi-25(OH)D in the adult human serum samples. Surprisingly, they found that this metabolite — previously thought to only exist in the blood of infants — was present in adult serum. "This reference material provides a mechanism to ensure measurement accuracy and comparability and represents a first step toward standardization of 25(OH)D measurements," say the researchers.

More information: Development and Certification of a Standard Reference Material for Vitamin D Metabolites in Human Serum, Anal. Chem., 2012, 84 (2), pp 956–962. DOI: 10.1021/ac202047n

Abstract
The National Institute of Standards and Technology (NIST), in collaboration with the National Institutes of Health’s Office of Dietary Supplements (NIH-ODS), has developed a Standard Reference Material (SRM) for the determination of 25-hydroxyvitamin D [25(OH)D] in serum. SRM 972 Vitamin D in Human Serum consists of four serum pools with different levels of vitamin D metabolites and has certified and reference values for 25(OH)D2, 25(OH)D3, and 3-epi-25(OH)D3. Value assignment of this SRM was accomplished using a combination of three isotope-dilution mass spectrometry approaches, with measurements performed at NIST and at the Centers for Disease Control and Prevention (CDC). Chromatographic resolution of the 3-epimer of 25(OH)D3 proved to be essential for accurate determination of the metabolites.

Provided by American Chemical Society (news : web)

New standard specification may facilitate use of additives that trigger biodegradation of oil-based plastics in landfill

Despite efforts to encourage the recycling of plastic water bottles, milk jugs and similar containers, a majority of the plastic packaging produced each year in the United States ends up in landfills, where it can take thousands of years to degrade.  To address that problem with traditional polyethylene, polypropylene, Styrofoam and PET products, researchers at the Georgia Institute of Technology are working with the Plastics Environmental Council (PEC) to expand the use of chemical additives that cause such items to biodegrade in landfills.

Added during production of the plastic packaging, the compounds encourage anaerobic landfill bacteria and fungi to break down the plastic materials and convert them to biogas methane, carbon dioxide and biogenic carbon – also known as humus.  These additives – simple organic substances that build on the known structures of materials that induce polymer biodegradation – don’t affect the performance of the plastics, introduce heavy metals or other toxic chemicals, or prevent the plastics from being recycled in current channels.

If widely used, these additives could help reduce the volume of plastic waste in landfills and permit much of the hydrocarbon resource tied up in the plastic to be captured as methane, which can be burned for heating or to generate electricity.

“Research done so far using standard test methods suggests that the treated plastics could biodegrade completely within five to ten years, depending on landfill conditions,” said Lisa Detter Hoskin, a principal research scientist in the Georgia Tech Research Institute (GTRI) and co-chair of the PEC’s technical advisory committee.  “However, legislators, regulatory agencies and consumers need more assurance that these containers will perform as expected in actual landfills. We need to provide more information to help the public make informed buying decisions.”

To provide this information, Hoskin and other Georgia Tech researchers are working with the Atlanta-based PEC to develop a set of standards that would ensure accuracy and consistency in the determination and communication of the plastic containers’ biodegradation performance.

“We are working to develop a new standard specification for anaerobically biodegradable conventional plastics,” Hoskin said.  “This certification is intended to establish the requirements for accurate labeling of materials and products made from oil-derived plastics as anaerobically biodegradable in municipal landfill facilities. The specification, along with a certifying mark, will allow consumers, government agencies and recyclers to know that the item carrying it is both anaerobically biodegradable and recyclable.”

The standard specification will provide detailed requirements and test performance criteria for products identified as anaerobically biodegradable, and will include rates for anaerobic biodegradation in typical U.S. landfills.  These rates will be based on biodegradation test data and results from research being undertaken by Georgia Tech and North Carolina State University.

With support from the PEC and its member companies, Hoskin has directed testing efforts that show mechanistically how the additives work, and are showing that the degraded plastic leaves behind no toxic materials.  With that part of the project largely completed, she now leads the development of the standard specification and certifying mark, and plans to organize a network of accredited laboratories that will test products made with the biodegradable additives to certify that they do degrade within a specific period of time.

Full development and adoption of the new standard specification by ASTM International will likely take between 18 months and two years, Hoskin said.  The project will involve research being done using landfill simulations at North Carolina State University and other independent laboratories.

Using information from laboratory-scale anaerobic reactors operated under a range of temperatures, moisture levels and solids contents, researchers will compare the time required to break down known anaerobically biodegradable materials – such as newsprint, office waste and food waste – against the time required to degrade those same wastes in real landfills.  That information will be used to project the biodegradation rate for the treated plastics in a range of real landfills, which vary considerably in moisture and other factors.

Though they are recyclable, plastics made from hydrocarbons had not been biodegradable until development of microbe-triggering additives. Bioplastics such as those made from corn may be composted, while a small percentage of specialized plastic products – known as oxobiodegradables – are designed to degrade when exposed to oxygen and ultraviolet light.  But the bulk of the plastic resins used in bottles and other containers are made from materials that will last virtually forever in landfills, noted Charles Lancelot, executive director of the PEC.

Many communities operate recycling programs for plastics and other materials such as newsprint, aluminum and steel cans or cardboard.  But because the cost of collecting, sorting, cleaning and reprocessing most plastics can be more than the cost of producing new products, such programs struggle financially unless they are subsidized, he noted.

“If you can make a product like a bread tray and use it over and over again, that is the most efficient alternative,” said Lancelot, who developed successful business-to-business recycling programs while working at Rubbermaid.  “But if you can’t reuse it and it’s not cost-effective to recycle it, where is the product going to go?  The fact is that despite the best wishes of everybody involved, 75 to 85 percent of the plastics used today end up in landfills.  We are addressing that unfortunate reality.”

Although biodegradation occurs to varying extents in all U.S. landfills receiving waste today, many of today’s landfills are optimized for biodegradation, he noted.  Moist conditions and recirculation of leachate liquids accelerate the activity of anaerobic bacteria, which will attack plastic materials containing the additives. Such landfills typically do a better job of collecting and beneficially using the methane biogas, Lancelot said.

“When the anaerobic microorganisms that thrive in landfills contact these treated plastics, they begin to colonize on the surface of the plastic and adapt to the base resin,” he explained.  “Until the bugs come in contact with the plastic, the additives remain inert and do not affect the properties of the plastic container.  We are not changing the overall plastics production process, and the base plastic is the same.”

The compounds, which have been approved by the U.S. Food & Drug Administration (FDA), are typically added to the plastic resin in small amounts, between one-half and one percent by weight.

Expanding the use of anaerobically biodegradable additives must be done in such a way that doesn’t detract from recycling programs, said Matthew Realff, a professor in Georgia Tech’s School of Chemical & Biomolecular Engineering and co-chair of the PEC’s technical advisory committee.

“From a lifecycle perspective, it is important to quantify the benefit of recycling over landfill disposal with methane recovery to energy, and to continue to make the case that whenever possible, recycling is significantly better than disposal, even if you have methane production and capture from biodegradation,” he said.

While the biodegradation of plastic materials may solve one problem, the production of methane and carbon dioxide – both atmospheric warming gases – could worsen global climate change, he noted.

“Landfill capture of methane is not 100 percent efficient, nor does it begin immediately after the material is put into the landfill,” Realff said.  “Therefore, there will be emissions from biodegradation that will reach the atmosphere.  It is important to be aware of how accelerating the production of methane would change overall emissions.”

A 45-year veteran of the U.S. plastics industry, Lancelot says he is pleased to be working with Georgia Tech on a potential solution to the problem of plastics in landfills.  The research will help close a gap in plastics “end-of-life” options where reuse or recycling are not feasible.

“Nobody had commercially biodegraded petroleum-based commodity plastics like polyethylene, polypropylene and polystyrene before these additives became available,” he noted.  “This is ground-breaking work that is based on a solid scientific platform that defines biodegradability as a practical and useful end result.”

Provided by Georgia Institute of Technology (news : web)