Blue Cheese in the gluten-free diet – A research update
by Alex Anca, MHSc., RD and Advisor to the CCA Professional Advisory Board
Blue cheese has always been a hot topic in the gluten-free diet. A charming legend tells of a young shepherd watching his sheep in the Roquefort-sur-Soulzon area of France. He was resting near a cave, enjoying lunch of bread and ewe’s milk cheese when a beautiful girl caught his eye. He quickly stowed his meal in the cave and chased after his heart. A few months later, he stumbled upon the abandoned bread and cheese. Despite the mould and strong aroma, his hunger drove him to bite into the cheese, discovering the delightful flavour of what would one day become Roquefort, the unique blue cheese made from the region’s specific mould, Penicillium roqueforti.
This story has brought blue cheese to the forefront of the debate amongst those who suffer from celiac disease – is it safe for consumption or not?
Back in 1992, the second edition of the Canadian Celiac Association’s Pocket Dictionary classified Blue Cheese as “ALLOWED” in the gluten-free diet. The status was based on Dr. J. A. Campbell’s research in late 1991. It revealed that even though P. roqueforti mould may be grown on gluten-containing media, the harvesting and the amount of spores used to make blue cheese (1 g of fungus added to 10,000 L of milk!) may lead to a final gluten concentration well below the 20 parts per million threshold.
Because questions continued to arise about blue cheese’s suitability in the gluten-free diet, we decided to conduct a more in-depth investigation in an attempt to clarify and further understand the science behind blue cheese.
Blue cheese is a classification of cow’s milk or goat’s milk cheeses with green/bluish mould. Varieties of internally mould-ripened, hard-pressed cheeses include Stilton, Blue Shropshire, Blue Cheshire, Blue Wensleydale, Buton Blue, Blue Vinney, Danish Blue, Roquefort and Gorgonzola1. By international agreement, Roquefort cheese must be made from sheep milk, in the Roquefort Valley of France, and ripened in naturally air-conditioned, high-humidity caves near the town of Roquefort. Similarly, manufactured cheese produced from cow’s milk in the United States and other countries is called blue cheese2.
Blue cheese is usually made from a blend of heat-treated (raw) or pasteurized skim milk and homogenized cream. Spore suspensions of Penicillium roqueforti are added to the vat at the same time as the starter cultures. The cheese contains no other ingredients except the spores and natural milk components.
Spores of P. roqueforti may be harvested from mould grown on mixed substrates: some may be gluten-free, while others may contain malt extract. For the latter type of media, the fermentation process usually breaks down gluten. Moreover, in order to multiply, P. roqueforti fungus uses the protein portion of the media (i.e., gluten) to grow. Following fermentation, the spores are collected and the medium is discarded. Cultures (or spores) are then diluted, based on manufacturer’s specifications to 1:500,000 to 1:1,000,000 (where 1 unit is 1 g of P. Roqueforti culture). This is equivalent to 1 g of mould in 500 to 1,000 L of milk.
In order to assess and quantify whether blue cheese contains any residual amounts of gluten, we sent three samples of blue cheese that use mould grown in gluten-containing media in addition to two samples of mould culture grown on wheat-based dextrose.
The analysis was conducted by Dr. Terry Koerner’s laboratory in the Food Research Division at Health Canada. Three different commercial ELISA test kits were used:
- R-Biopharm sandwich ELISA test, with a Limit of Detection of 1.5 parts per million and a Limit of Quantification of 2.5 parts per million.
- Tepnel sandwich ELISA test, with a Limit of Detection of 1 part per million and a Limit of Quantification of 3 parts per million.
- R-Biopharm Competitive ELISA test which is used to detect gluten protein fragments, such as those produced from protein hydrolysis.
The results of the tests were as follows:
- St. Benoit Blue Cheese: No detectable gluten (all three kits). The manufacturer, L’Abbeille St. Benoit du Lac, uses P. Roqueforti mould grown on media containing malt extract.
- Roquefort Blue Cheese: No detectable gluten (all three kits). The manufacturer, Roquefort Société, uses P. Roqueforti mould grown in a medium containing rye and wheat flours.
- Alexis de Portneuf Blue Cheese: No detectable gluten (all three kits). The manufacturer uses P. Roqueforti mould grown on gluten-containing media.
- Two samples of P. Roqueforti moulds: No detectable gluten (all three kits). The mould and culture manufacturer uses wheat-based dextrose in the fermentation medium. However, this ingredient is considered safe as the manufacturing process, separation and purification techniques render it gluten-free regardless of the source.
These results are considered accurate and reliable since each product was tested three times using the most sensitive gluten detection tests available on the market. In addition, you may consider that some manufacturers of blue cheese, such as Rosenburg®, provide information on their websites about the use of gluten-free mould cultures.
Based on the most sensitive tests currently available on the market and our understanding of the minute amounts of mould spores used in the making of the cheese, we may conclude that blue cheese is safe for consumption as part of the gluten-free diet. In the future, we may attempt to test more samples of blue cheese in order to validate the results described above.
I hope that the research outlined above will put to rest the controversy surrounding blue cheese and that patients with celiac disease will enjoy the unique taste and sensory experience it has to offer.
Alexandra Anca is the principal researcher for the Canadian Celiac Association’s Pocket Dictionary of Ingredients – Acceptability of Foods & Food Ingredients for the Gluten-Free Diet.