Food Authentication with Proteomic Analysis

Food safety relies on industry attention to accurate labeling, with full disclosure on ingredients and source for authentication. Regulatory officials must protect consumers from food fraud, adulteration, and accidental contamination. In order to identify contaminants that may not be apparent on labels, they, therefore, need robust, sensitive methods for monitoring products. Ortea et al. (2016) present a review of proteomics tools that are suitable and available for food authentication¹.

Producers have a duty to inform consumers of content on all products. This is primarily for health and safety, as food allergies affect a significant proportion of the population with potentially harmful or even fatal results. Labeling also confirms authenticity since many specialty foods are sold for a higher price than regular varieties. Consumers may also wish to avoid certain foods on philosophical or religious grounds, relying on labeling to help guide their choice.

Regulation of the food industry is usually under national control, and officials must be able to tell if a food product contains potentially harmful allergens, for example, or has been adulterated with a cheaper ingredient. In order to do this, authorities must use tools that are capable of identifying very small amounts within a wide variety of food matrices. Many are now turning to new -omics techniques including mass spectrometric-based (MS) proteomics analysis to achieve this.

Proteins are ideal markers in food, showing source, ingredient and even processing signatures. Most proteomics techniques measure peptide levels, which are stable within food matrices but can retain a signature due to processing. Although traditional tools such as immunoassay, gel-based separation and isoelectric focusing (IEF) are usually the only officially approved methods, researchers are assessing mass spectrometry and other -omics approaches as tools to run in tandem. As high-throughput and sensitive assays for food authentication, they add a further level of confidence and efficiency to regulatory testing.

Mass spectrometric characterization of proteins in food requires sample preparation to extract proteins; often this needs optimization according to the biological matrix involved. Once extracted, scientists usually digest the proteins using trypsin or other proteolytic enzymes for bottom-up analysis, unless top-down intact protein characterization is preferred.

Types of mass spectrometric proteomic evaluation

Qualitative
Scientists identify and characterize protein presence in the sample, analyzing post-translational alterations and other changes that can indicate processing conditions such as the Maillard reaction.
Differential or quantitative
Using approaches such as label-free or serial reaction monitoring, scientists can quantify protein levels in food matrices. This allows comparison between samples and with reference materials.
Functional
Further analysis of the spectral data from mass spectrometry allows scientists to identify interactions and look for isoforms by characterizing protein function.

Mass spectrometric evaluation has been used to detect allergen contamination since it is sensitive to minute trace amounts of a protein that could potentially harm allergic consumers. [see allergen detection posts on Examining Food for further info]

The technique has also been used for food authentication in the following food groups:

Milk and Dairy
Premium dairy products such as goat milk may be adulterated with cheaper cow’s milk to maximize profits. By looking at key peptide markers, scientists can show the fraudulent presence of milk from another species. Although IEF will show the presence of ꙋ2 and ꙋ3 cow-specific globulins, sensitivity is an issue. Mass spectrometric proteomics can easily discriminate, in addition to showing processing alterations such as ultra-high heat treatment (UHT).
Meat
MS-based proteomics studies show adulteration with soy protein for example, in addition to confirming breed-specific markers for authenticity.
Shellfish and Fish
Studying proteomes in a product can verify the source, geographic area, and determine whether it is wild-caught or farmed.
Genetic Modification
Although proteomics can give some information, the target change in these products is genomic and research shows that there is very little alteration in proteins.
Wine
Proteomics can give answers to traceability and quality control questions; however, since very little protein is left in wine, scientists use proteomics more for ensuring removal of fining agents such as casein, since regulations require labeling of these ingredients at levels above 25mg/L.

Ortea et al. suggest that although mass spectrometric evaluation of foodstuffs is limited due to the relative lack of suitable reference materials for such a broad testing environment, it presents a robust and sensitive platform for high-throughput testing. Furthermore, the ability for multiplexed analysis makes it highly suitable for busy food authority testing laboratories. Mass spectrometric proteomics, therefore, shows great potential for future development in food safety testing.

Reference

1. Ortea, I. et al. (2016) “Review on proteomics for food authentication“, Journal of Proteomics 147 (pp.212–25)

Further Reading on Examining Food

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