Improved extraction of peanut residues from a wheat flour matrix for immunochemical detection

Development of a Mass Spectrometry-Based Method for Quantification of Total Cashew Protein in Roasting Oil

BACKGROUND

Food allergen cross-contact during food preparation and production is one of the causes of unintentional allergen presence in packaged foods. However, little is known about allergen cross-contact in shared frying or roasting oil, which prevents the establishment of effective allergen controls and may put allergic individuals at risk. To better understand the quantity of allergen transferred to frying oil and subsequent products, an analytical method is needed for quantifying protein in oil that has been exposed to frying/roasting conditions.

OBJECTIVE

The goal of this study was to develop a parallel reaction monitoring LC-MS/MS method to quantify the amount of cashew protein in shared roasting oil.

METHODS

The sample preparation method was evaluated to improve protein extractability and peptide performance. Four quantitative peptides representing cashew 2S and 11S proteins were selected as targets based on their sensitivity, heat stability, and specificity. A calibration strategy was developed to quantify the amount of total cashew protein in oil. Method performance was evaluated using a heated cashew-in-oil model system.

RESULTS

The method showed high recovery in oil samples spiked with 100 or 10 parts per million (ppm) total cashew protein heated at 138 or 166°C for 2-30 min. Samples (100 ppm total cashew protein) heated for 30 min had more than 90% recovery when treated at 138°C and more than 50% when heated at 166°C.

CONCLUSION

The method is fit-for-purpose for the analysis of cashew allergen cross-contact in oil.

HIGHLIGHTS

A novel MS-based method was developed that can accurately quantify the amount of cashew protein present in heated oil.

Evaluation of ELISA Test Kits for Detection of Milk Protein in Frying Oil Treated at Different Temperatures

Milk is a common ingredient in fried foods. Allergen cross-contact can occur through the reuse of frying oil. To enable assessment of the allergy risk of reused oil, methods for quantification of milk protein in oil are needed. This study evaluated four commercial ELISA test kits in comparison with the 660 nm total protein assay for the detection of milk protein in oil after frying. Corn oil spiked with nonfat or whole milk powder were fried at 150 °C or 180 °C for 3 min and were analyzed by ELISA kits either directly or after preextraction with phosphate-buffered saline containing 0.05% Tween (PBST). All four ELISA kits performed well in quantifying milk protein in unheated oil, achieving normalized recoveries of 72.1-115.9% compared with that determined in reference solutions (PBST spiked with nonfat or whole milk powder, 100%). Frying lowered the amount of protein detected, but the extent of reduction differed between test kits. In nonfat milk powder-spiked oil fried at 150 °C, normalized recoveries determined by Veratox Total Milk and BioKits BLG Assay (49.9% and 43.6%, respectively) were higher than that determined by the 660 nm assay (25.4%). Normalized recoveries determined by ELISA Systems Casein and Beta-Lactoglobulin (BLG) kits were substantially lower (9.7% and 2.4%, respectively). In samples fried under typical frying temperature (180 °C), very little protein (0.1-7.4%) was detected. Inclusion of PBST preextraction improved the detection of the two test kits targeting BLG but lowered the level of protein detected by Veratox and ELISA Systems Casein in fried samples. Overall, the ELISA kits evaluated could effectively quantify milk protein in unheated oil without the need to remove the oil phase prior to analysis. Heat treatment was the key factor negatively affecting protein quantitation. Such impact needs to be considered when ELISA test results are used for assessing the allergy risk of reused frying oil.

Doses of Specific Allergens in Early Introduction Foods for Prevention of Food Allergy

BACKGROUND

Consumption of common allergenic foods, such as peanut, in early life can reduce the risk of food allergy among high-risk children and is recommended in revised clinical guidelines. Commercial early allergen introduction foods (EIF) containing single or multiple allergenic foods for feeding infants are promoted to consumers and health care providers as aids to prevent food allergy.

OBJECTIVE

To determine the concentration and doses of major food allergens in EIF.

METHODS

Extracts from 32 EIF and 4 control foods were analyzed for 17 allergens: Ara h 1, Ara h 3, Ara h 6, Bos d 5, Bos d 11, Gal d 1, Gal d 2, Ana o 3, Cor a 9, Jug r 1, Gly m 5, Ses i 1, Api g 1, Sin a 1, Cyp c 1, shrimp tropomyosin, and Tri a 19 using a validated fluorescent multiplex array. Ara h 2 was measured by enzyme-linked immunosorbent assay.

RESULTS

The EIF comprised 1-8 samples of 32 foods (n = 86). Combined peanut allergen levels of up to 26,000 μg/g were measured in peanut puffs (doses of 65-182 mg per 7 g serving). Peanut allergens were not detected in mixed food blend puffs. Major allergen levels of >10,000 μg/g were found in several milk, egg, and peanut powders, or combinations thereof, with cumulative allergen doses of 159-2946 mg in the EIF. Mixed food blend powders, puffs crackers, and fruit sauces contained much lower allergen levels, often <10 μg/g, and some had undetectable allergens. The allergen concentration in these EIF varied over a >3 log range and provided lower cumulative doses of allergen.

CONCLUSIONS

Significant variability in allergen composition, concentration, and dose per serving were observed in EIF containing the same foods. The doses of allergens consumed by potentially at-risk infants in early life were EIF dependent. Guidelines should be established to enable consumers and health care providers to make informed decisions about EIF and to improve the formulation and standardization of EIF for prevention of food allergy.

A stable and sensitive enzyme-linked immunosorbent assay (ELISA) for the determination of metsulfuron-methyl residues in foods

A hapten of metsulfuron-methyl was successfully designed and synthesized from 2-methylester-phenylsulfonamide and succinic anhydride, and the polyclonal antibody against metsulfuron-methyl was prepared by immunization procedure with the hapten-bovine serum albumin conjugate. A stable and sensitive direct competitive enzyme-linked immunosorbent assay (dcELISA) method had been developed under the optimal conditions. The sensitivity (IC₅₀ ) was 37.03 ± 1.87 µg/L, and the detection line (IC₁₅ ) was 1.57 ± 0.11 µg/L. Rice, wheat, oat, flaxseed, milk, and water were chosen to study the recovery test and the recovery rates were 83.11%-117.44% . The matrix effect was eliminated by a simple dilution of the sample extracts. The results from dcELISA were well agreement with the results from HPLC-MS. It was indicated that the developed method had good accuracy and stability. It could be applied for the detection of metsulfuron-methyl residues. It was worth mentioning that the antibody could recognize metsulfuron-methyl and tribenuron-methyl with cross-reactivities of 100% and 49.72%, respectively. In order to understand the cross-reactivity, molecular modeling including molecular alignment and electrostatic potential surfaces were introduced. It was found that the special group of metsulfuron-methyl played an important role, especially on C3 position of the phenyl group. PRACTICAL APPLICATION: A stable, sensitive, and low-cost dc ELISA method had been developed with good accuracy and applied in the determination of metsulfuron-methyl in foods. Molecular simulation was introduced to understand the specificity between the antibody and the analyst. It was a good method to study the cross-reactivity between the antibody and the analyst or analogue.

Development of a simplified, sensitive, and accurate LC-MS/MS method for peanut quantification in wheat flour-based dry matrices

In this study, an ELISA-based method was observed to overestimate quantification of peanut in three wheat flour-based dry matrices (both raw and cooked). A reliable method using liquid chromatography tandem mass spectrometry (LC-MS/MS) was developed to quantify peanut accurately in these matrices. This method simplified both sample preparation and quantification compared with previous approaches, by digesting peanut proteins without reduction and alkylation and using Ara h 1 to build calibration curves. A significantly increased amount of peanut peptides was detected by heating the extracts. The sensitivity and linearity were superior to most commercial ELISA kits. The limit of quantification (LOQ) was 0.31 mg/kg total peanut in wheat flour and the linear range was between 0.3 and 40 mg/kg. This LC-MS/MS method could be applied as a confirmatory method for peanut allergen management when positive ELISA results raise suspicion of contamination.