Survey of Commercial Food Products for Detection of Walnut (Juglans regia) by Two ELISA Methods and Real Time PCR

Update on hazelnut allergy: Allergen characterization, epidemiology, food processing technique and detecting strategy

Hazelnuts are popular among people due to their dense nutrient component. However, eating them may be quite dangerous for those who are allergic. To improve food safety, this research examines current developments in the characterization, processing, and detection of hazelnut allergens. The identification and molecular knowledge of certain proteins that cause allergic responses are necessary for the characterization of hazelnut allergens. Proteomics and genomics are two techniques that have helped to advance our knowledge of hazelnut allergens and facilitate the creation of more precise diagnostic instruments. One important factor to reduce but not to eliminate the exposure to hazelnut allergens is food processing. The extractability of hazelnut proteins with regard to food processing plays a crucial role in determining allergenicity. Innovative technologies have been created to lessen allergenicity in foods containing hazelnuts while preserving their flavor and quality. These technologies include thermal and nonthermal processing techniques. To further safeguard consumers with hazelnut allergies, innovations in ingredient labeling and cross-contamination avoidance techniques have been put into place. For the purpose of management, if foods contain hazelnut, they must label it. Technological developments in analytical methods, including mass spectrometry, polymerase chain reaction, and enzyme-linked immunosorbent assays, have made it possible to identify hazelnut allergens with high specificity and sensitivity in a range of dietary matrices. Moreover, the advancement of point-of-care testing instruments presents the possibility of prompt on site identification, hence enhancing food safety for people with hazelnut allergies. The multidisciplinary efforts of researchers, food technologists, and allergists to enhance the safety of products containing hazelnuts are highlighted in this study.

An integrated microfluidic platform for on-site qPCR analysis: food allergen detection from sample to result

Improving food safety is crucial in the context of a "One Health" approach. To guarantee product quality and safety, the food industry, which has a very high turnover rate, needs short time-to-result analyses. Therefore, user-friendly systems at the point-of-need are necessary, presenting relevant analytical information and fulfilling the current regulations. To answer these challenges, a microfluidic platform integrating sample preparation and subsequent multiplex qPCR detection has been developed for on-site testing. The system consists of a fully automated instrument driving a microfluidic cartridge dedicated to the detection of multiple allergens in complex food matrices. The first part of the microfluidic cartridge contains pumps, reservoirs, valves and a filter to achieve DNA extraction, concentration and purification. Multiplex qPCR detection is carried out in the second part of the cartridge including a negative control chamber and five chambers for target analyte detection. The in-house developed instrument contains all functions to autonomously drive the microfluidic cartridge: pneumatic control for fluid actuation, thermal control for qPCR amplification and an optical system using three fluorescent wavelengths for multiplex detection of the target analytes and controls. We demonstrate the simultaneous detection of four different allergens - gluten, sesame, soy and hazelnut - from various complex food matrices. The turn-around-time from sample to result is close to two hours and controls in place validate the obtained results. For gluten, a direct comparison with ELISA shows that the regulatory threshold of 20 ppm is comfortably fulfilled. Moreover, all results are in agreement with external laboratory analyses performed in parallel on the same samples. Our findings confirm that the system can be used safely on-site without the risk of cross contamination between the various samples being analysed. In conclusion, our microfluidic platform offers a robust method for on-site allergen management.

Development and Validation of a Loop-Mediated Isothermal Amplification (LAMP) Method for the Rapid, Sensitive, and Specific Detection of Hazelnut as an Allergen in Food Matrix

Analytical verification of hazelnut in food supports risk-based approaches for proper allergen labeling to prevent unwanted allergic reactions or to quality control diagnostic or therapeutic allergen preparations for allergic subjects. We present the development and validation of a loop-mediated isothermal amplification (LAMP) assay for rapid detection of hazelnut by targeting the internal transcribed spacer 2 gene. The qualitative method requires neither sophisticated analytical equipment nor antibodies, allowing an easy-to-use application with no ethical concern related to the use of animals. It demonstrated a limit of detection at or below 10 mg/kg hazelnut in various food matrices, making it also suitable for verifying hazelnut at levels of clinically relevant eliciting doses. Validation against proficiency test samples and testing of applicability with commercial food items confirmed its usefulness in processed foods. The simplicity of the method, including visual colorimetric detection, combined with high specificity and sensitivity, represents an advancement over existing qualitative methods.

Performance Evaluation of a Commercial Real-Time PCR Method for the Detection of Lupin Traces in Food

In accordance with U.S. FDA Foods Program Regulatory Science Steering Committee guidelines, with this study, we optimized and validated a commercial real-time PCR method for the detection of low amounts of lupin in four classes of food matrices: chocolate cookies, ragù, Olivier salad, and barley and rice flour. DNA extracted from blank (true negative) samples artificially contaminated with lupin (Lupinus albus) flour at 1000 ppm underwent dilutions with the DNA extracted from the true negative samples up to 0.5 ppm. The limit of detection for real-time PCR was 0.5 ppm in the complex matrices (range, Ct 26-34), making this a specific, robust, and rapid method for lupin allergen detection and labeling. Our validation data support the suitability of this commercially available real-time PCR method for this purpose.

Discovery, verification, and validation of walnut protein marker peptides using LC-MS approaches

A key requirement of liquid chromatography-mass spectrometry (LC-MS)-based allergenic food protein analysis methods is to use protein marker peptides with good analytical performances in LC-MS analysis of commercial processed foods. In this study, we developed a multi-stage walnut protein marker peptide selection strategy involving marker peptide discovery and verification and LC-MS validation of chemically equivalent stable isotope-labeled peptides. This strategy proposed three walnut protein marker peptides, including two new marker peptides. Our LC-MS-based walnut protein analysis method using the three stable isotope-labeled peptides showed acceptable linearity (R2 >0.99), matrix effects (coefficient of variation <±15%), sensitivity (limit of detection >0.3 pg/μL, limit of quantification >0.8 pg/μL), recovery (85.1-103.4%), accuracy, and precision (coefficient of variation <10%). In conclusion, our multi-stage marker peptide selection strategy effectively selects specific protein marker peptides for sensitive detection and absolute quantification of walnut proteins in LC-MS analysis of commercial processed foods.

Detection of Allergenic Proteins in Foodstuffs: Advantages of the Innovative Multiplex Allergen Microarray-Based Immunoassay Compared to Conventional Methods

Several factors can affect the allergen content and profile of a specific food, including processing procedures often leading to a decrease in allergenicity, although no change, or even an increase, have also been reported. Evaluation of the effectiveness of a processing procedure requires the availability of reliable methodologies to assess the variation in molecules able to induce allergic reactions in the analyzed food. Conventional and innovative strategies and methodologies can be exploited to identify allergenic proteins in foodstuffs. However, depending on the specific purposes, different methods can be used. In this review, we have critically reviewed the advantages of an innovative method, the multiplex allergen microarray-based immunoassay, in the detection of allergens in foodstuffs. In particular, we have analyzed some studies reporting the exploitation of an IgE-binding inhibition assay on multiplex allergen biochips, which has not yet been reviewed in the available literature. Unlike the others, this methodology enables the identification of many allergenic proteins, some of which are still unknown, which are recognized by IgE from allergic patients, with a single test. The examined literature suggests that the inhibition test associated with the multiplex allergen immunoassay is a promising methodology exploitable for the detection of IgE-binding proteins in food samples.

Tree Nuts and Peanuts as a Source of Beneficial Compounds and a Threat for Allergic Consumers: Overview on Methods for Their Detection in Complex Food Products

Consumption of tree nuts and peanuts has considerably increased over the last decades due to their nutritional composition and the content of beneficial compounds. On the other hand, such widespread consumption worldwide has also generated a growing incidence of allergy in the sensitive population. Allergy to nuts and peanuts represents a global relevant problem, especially due to the risk of the ingestion of hidden allergens as a result of cross-contamination between production lines at industrial level occurring during food manufacturing. The present review provides insights on peanuts, almonds, and four nut allergens—namely hazelnuts, walnuts, cashew, and pistachios—that are likely to cross-contaminate different food commodities. The paper aims at covering both the biochemical aspect linked to the identified allergenic proteins for each allergen category and the different methodological approaches developed for allergens detection and identification. Attention has been also paid to mass spectrometry methods and to current efforts of the scientific community to identify a harmonized approach for allergens quantification through the detection of allergen markers.

Detection of Peanut Traces in Food by an Official Food Safety Laboratory

Food safety laboratories rely on validated methods that detect hidden allergens in food to ensure the safety and health of allergic consumers. Here we present test results for the validation and accreditation of a real-time PCR assay for the detection of peanut traces in food products. The method was tested on five classes of food matrices: bakery and pastry products, meats, ready-to-eat and dairy products, and grains and milling products. Blank samples were spiked starting with the peanut samples (Arachis hypogaea) at a concentration of 1000 ppm. Serial dilutions were then prepared with the DNA extracted from the blank samples to a final concentration of 0.5 ppm. The limit of detection in grains and milling products, ready-to-eat, meats, bakery and pastry products was 0.5 ppm (range, Ct 27–34) and 2.5 ppm in dairy products (range, Ct 25–34). In order to determine the exclusivity parameter of the method, the ragù matrix was contaminated with Prunus dulcis (almonds), Glycine max (soy), Sinapis alba (mustard), Apium graveolens (celery), Allium cepa (onion), Pisum sativum (peas), Daucus carota (carrots), and Theobroma cacao (cocoa); no cross-reactions were observed. The method was rated satisfactory for sensitivity (98%), specificity (100%), robustness, and repeatability and it was fully validated and accredited.

Establishment and Evaluation of a Loop-Mediated Isothermal Amplification Assay for Rapid Detection of Pseudomonas fluorescens in Raw Milk

Raw milk is susceptible to microbial contamination during transportation and storage. Pseudomonas fluorescens producing heat-resistant enzymes have become the most common and harmful psychrophilic microorganisms in the cold chain logistics of raw milk. To rapidly detect P. fluorescens in raw milk, the protease gene aprX was selected as a detection target to construct a set of primers with strong specificity, and a loop-mediated isothermal amplification (LAMP) assay was established. The detection thresholds of the LAMP assay for pure cultured P. fluorescens and pasteurized milk were 2.57 × 10² and 3 × 10² CFU/mL, respectively. It had the advantages over conventional method of low detection threshold, strong specificity, rapid detection, and simple operation. This LAMP assay can be used for online monitoring and on-site detection of P. fluorescens in raw milk to guarantee the quality and safety of dairy products.