Detection and quantification of white and black sesame as potential allergenic ingredients in processed foods: A comparative gene marker study

First nanoplate digital PCR method to trace allergenic foods: Improved sensitivity for the detection of sesame

Sesame (Sesamum indicum L.) is an important allergenic food whose presence can be the cause of severe allergic reactions in sensitised individuals. In this work, nanoplate digital PCR (ndPCR) was used to develop two methods to detect trace amounts of sesame in processed foods and compared with previously proposed real-time PCR assays. Two independent ndPCR approaches were successfully advanced, achieving sensitivities of 5 and 0.1 mg/kg of sesame in dough/biscuits, targeting the CO6b-1 and ITS regions, respectively. The sensitivity using both targets was improved by one order of magnitude comparing with real-time PCR and was not affected by food processing. CO6b-1 system was not influenced by food matrix, exhibiting similar performance regardless the use of complex matrix extracts or serial diluted DNA. Herein, ndPCR was proposed for the first time for the detection of allergenic foods with the advantage of providing better performance than real-time PCR regarding sensitivity and robustness.

Quantitative Real-Time PCR for the Detection of Allergenic Species in Foods

Food allergy is an increasing challenge to public health, with widespread global distribution. With no cure for this pathology, the food-allergic individuals are forced to adopt food eviction measurements, relying on label information to avoid consuming the offending foods. To safeguard these individuals, the analytical methods based on real-time PCR approaches are currently faced as excellent tools to verify labeling compliance, aiding industry and regulatory agencies to efficiently manage food allergen control programs. Therefore, this chapter intends to describe a protocol of real-time PCR to analyze allergenic food species. For method development, the main steps to be considered are (i) in silico sequence analysis and primer/hydrolysis probe design, (ii) preparation of calibrators (model foods containing the allergenic ingredient), (iii) efficient DNA extraction from complex food matrices, (iv) amplification by real-time PCR with hydrolysis probe (90-200 bp) targeting a highly specific DNA region (allergen-encoding gene), (v) sequencing PCR products for identity confirmation, and (vi) validation and application to commercial foods. Herein, a real-time PCR approach for the detection and quantification of cashew nut as an allergenic food is described as an example protocol, including all the steps for method development and validation.

Immunocolorimetric assay based on amplified gold nanoparticles and magnetic separation beads for detection of sesame allergens in food

We have developed a magnetic separation-based immunocolorimetric assay to detect sesame allergens. Sesame monoclonal antibody (Ab) was modified onto gold nanoparticles (AuNPs) to create signal probes (AuNPs-Ab), and sesame allergens (SA) were attached to carboxyl-functionalized magnetic polystyrene microspheres (MPMs) to act as capture probes (MPMs-SA). Based on the competition format, the capture probes competed with the sesame allergens in the sample to bind the corresponding signal probes. When sesame allergens were present, two immune complexes (AuNPs-Ab@MPMs-SA and AuNPs-Ab@SA) were formed. The immune complex AuNPs-Ab@SA was used to quantify the sesame allergens in the sample. This immunoassay had a detection linear range from 50 to 800 μg L^-1 with a limit of detection (LOD) of 45.53 μg L^-1. Based on the optimized conditions, the recovery of sesame allergens in bread, biscuit, almond beverage, and energy bar samples was between 82.50% and 116.67%. The LODs for the bread, biscuit, almond beverage, and energy bar samples were 0.36, 0.36, 0.27, and 0.55 mg kg^-1, respectively.

Sesame as a source of food allergens: clinical relevance, molecular characterization, cross-reactivity, stability toward processing and detection strategies

Sesame is an allergenic food with an increasing allergy prevalence among the European/USA population. Sesame allergy is generally life-persisting, being the cause of severe/systemic adverse immune responses in sesame-allergic individuals. Herein, clinical data about sesame allergy, including prevalence, diagnosis, relevance, and treatments are described, with focus on the molecular characterization of sesame allergens, their cross-reactivity and co-sensitization phenomena. The influence of food processing and digestibility on the stability/immunoreactivity of sesame allergens is critically discussed and the analytical approaches available for their detection in foodstuffs. Cross-reactivity between sesame and tree nuts or peanuts is frequent because of the high similarities among proteins of the same family. However, cross-reactivity phenomena are not always correlated with true clinical allergy in sensitized patients. Data suggest that sesame allergens are resistant to heat treatments and digestibility, with little effect on their immunoreactivity. Nevertheless, data are scarce, evidencing the need for more research to understand the effect of food processing on sesame allergenicity modulation. The demands for identifying trace amounts of sesame in foods have prompted the development of analytical methods, which have targeted both protein and DNA markers, providing reliable, specific, and sensitive tools, crucial for the effective management of sesame as an allergenic food.