Effect of roasting history and buffer composition on peanut protein extraction efficiency (1)
In some cases, highly processed peanuts may not be detected by commercial ELISA kits, but the same samples showed high binding capacity to human sera immunoglobulin E (IgE) from peanut allergic individuals. This may be due to low affinity of the employed animal IgG antibodies of the ELISA assay to the antigen (e.g., antibodies raised against raw material can have low affinity to heat- treated analyte) or inefficient extraction procedures (matrix effects, impaired solubility of denatured proteins, hydrophobic proteins remain bound in the food matrix). Moreover, animal IgG and patient IgE might react to different epitopes having different stabilities (e. g., after heat process- ing) and neo-epitopes might be generated by food process- ing, which are variably recognized by IgG and IgE antibodies.
Temperature/time profiles were selected to produce light and dark products of oil and dry roasted American and Chinese peanuts in-house.
Extraction with Tris-buffered saline (TBS, pH 8.2) at 48C overnight yielded approximately 127 mg and 104 mg of peanut protein from American and Chinese peanuts, respectively. oil-roasting decreased the yield of soluble peanut protein by approx. 50% and dry-roasting by 75 – 80% after TBS (pH 8.2) extraction.
Extracted protein quantities ranged between 187 and 135 mg soluble protein/ g whole peanut and the yield was decreased for oil-roasted peanuts by approximately 75% and for dry-roasted peanuts by 80%.
Best yields were obtained with buffers in the range of pH 8 – 11. Most protein was extracted with the sodium borate buffers at pH 9, different salt concentrations (0.3% and 0.6%) did not majorly affect the extraction efficiency for peanut protein. The TBS buffer at the higher pH (8.2) extracted approximately 35% more protein from peanuts than the TBS buffer at pH 7.4. Buffers at higher pH, such as sodium carbonate buffer (pH 11) and sodium borate buffer (pH 9) achieved generally higher protein yields.
