Since the publication of the Astwood et al. paper in 1996, there have been a number of scientific meetings, symposia and papers that have further discussed protocols (or the need for them) for testing digestive stability; these are reviewed by Dr. Ricki Helm, of the Arkansas Children's Hospital Reseach Institute, in his paper "Stability of Known Allergens (Digestive and Heat Stability)" written for the FAO/WHO expert consultation.
The paper by Dr. Helm (Helm, 2001) served as a starting point for discussion of the Joint FAO/WHO Expert Consultation on Allergenicity of Foods Derived from Biotechnology.
The final report of the Expert Consultation recommended a slightly modified version of Dr. Helm's
protocol (for example, rather than test the protein at a range of pHs to simulate the stomach at various times after feeding, the FAO/WHO Expert Consultation recommends testing only at pH 2.0), but it contained far more specific details about what the protocol should contain.
One significant extension of Dr. Helm's
protocol that the FAO/WHO Expert Consultation
included was the notion that "the expressed protein should be assessed in its principle edible form under identical pepsin degradation conditions to those used to examine the expressed protein" (FAO/WHO, 2001: 12).
Furthermore, as Dr. Helm
pointed out in his
paper for the FAO/WHO Expert Consultation
, recent industry and scientific thinking in this area concur: "The working committee on the 'Characteristics of Protein Food Allergens' held by ISLI/HESI following the symposium established the following criteria be taken into consideration. . . . 3-Deliver: Consideration should be given to how the material will be introduced into the diet.
Assessment of allergenicity should be based on the matrix/matrices that the novel protein would be introduced into the diet" (Helm, 2001: 6).
Finally, if a significant portion of the expressed protein does survive digestion in SGF, we recommend that it be tested further in SIF, using the protocol laid out by Dr. Helm
Both allergy scientists as well as the Environmental Protection Agency
(EPA) consider stability of a protein to heat to be a characteristic property of food allergens (Sampson, 1999; EPA
, 2001; Helm
, 2001; and Taylor and Hefle
In contrast to the EPA's lack of a consistent protocol, Dr. Helm
has developed a science-based protocol as part of the paper on the topic that he
wrote for the 2001 FAO/WHO Expert Consultation
: "Heat Stability: The definition of heat stability should be standardized using the following criteria.
1-Heat treatment of the novel protein, native and recombinant, should be for 5 minutes at 90°C.
2-Assessment of stability by a combination of molecular sieving using HPLC and standardized SDS-PAGE analysis (both native and denaturing/reducing gels).
See SDS-PAGE protocol below" [see the section on digestive stability, above for this protocol] (Helm, 2001: 8-9).
We urge that the FDA
require data on heat stability and use the science-based protocol as outline by Dr. Helm
Helm, R.M. 2001.
Topic 5: Stability of Known Allergens (Digestive and Heat Stability).
Working Paper Biotech 01/07 for the Joint FAO/WHO Expert Consultation
on Allergenicity of Foods Derived from Biotechnology, January 22-25, 2001.