Advancements in Mass Spec Analysis of Food Components, Additives, and Contaminants

Developments in Mass Spec Imaging and Data Processing for Food Testing Applications

Mass spectrometry is commonly used for analysis of agricultural products, dairy, processed food, beverages, and other consumables. One common objective is testing for residual pesticides and contaminants due to improper handling and processing. Food authenticity and fraud have become issues of growing importance as well, with a widening variety of food sources and types entering the market.

Food testing labs employ LC-MS/MS techniques for the identification of small molecules and compounds. This includes targeted quantitation of compound panels and untargeted analysis for identification of markers. The field of mass spec imaging (MSI) is growing in the food testing arena, with new techniques aiming to analyze the spatial distribution of food components, additives, and contaminants. The overall goals of MSI in food testing include new ways to improve quality, food safety, nutritional content, and the identification of food factors.

Mass spec imaging for food testing

Beyond the fundamental components that our bodies acquire from food – proteins, lipids, carbohydrates, vitamins, and minerals – there are many compounds that possess bioactive functions upon entering the body. These so-called functional factors can take the form of polyphenols, carotenoids such as lycopene, and other organic chemicals and can have either positive or negative (e.g., anti-oxidative/oxidative) effects on the body upon absorption. Food components such as fiber have constituents including arabinoxylans and beta-glucans that significantly influence the quality and subsequently the end-uses in either consumer foods, feed stocks, or ethanol production. It has become essential to identify these functional factor compounds (or lack thereof) to validate the quality and safety of food items.

Spatial distribution of these compounds through MSI analysis can help identify whether these factors are present and/or bioavailable in specific foods. Furthermore, the distribution of functional factors may contribute to the taste, color, smell, and texture of foods. LC-MS/MS approaches, although rigorous and highly valuable in food testing, have certain limitations for spatial distribution analysis including extensive extraction and sample preparation procedures. MSI technologies, borrowed from the life sciences and pharmaceutical research fields, have emerged to serve this important role in food science research and testing.

Different ionization methods have been used in food science research and testing, including secondary ion mass spectrometry (SIMS), matrix-assisted laser desorption ionization (MALDI), and desorption electrospray ionization (DESI), among others. MALDI benefits from the multitude of techniques and protocols for thin sectioning and high-resolution sample analysis. DESI – although less commonly used - benefits from the fact that it is an atmospheric technique that can be performed rapidly on minimally processed samples. Both can provide informative and actionable 2D spatial resolution results.

Advancements in MALDI mass spec imaging of fresh and processed food

A recent pre-print publication examined the distribution of components in fresh and processed food using advanced MALDI imaging techniques. The researchers targeted meat, dairy, and bakery product ingredients, contaminants, and additives.

Using an optimized workflow designed to address the specific challenges of each food sample, the investigators found the following:

• The presence of highly non-polar and polar constituents including beta-carotene and anthocyanins in fresh fruits and vegetables (kiwi and carrot)
• The first-time detection and distribution of acrylamide in processed food (German gingerbread)
• The first-time visualization and penetration of an additive into cheese (natasmycin)

The work supports the use of MSI in providing valuable information on the distribution of regulated chemicals and additives in foods. Furthermore, novel data processing tools stemming from this work may be generalized for use in investigating diffusion processes by MSI is a wide range of other applications.

New data analysis tools for food and beverage testing

A recent study titled “foodMASST a mass spectrometry search tool for foods and beverages” described the developed of an bioinformatics tool to search MS/MS spectra against a growing food and beverage reference database. The tool can interrogate both known and unknown molecules and the reference set includes extensive metabolomics data from a wide range of sources.

The investigators envision the foodMASST tool will become valuable for nutrition research and to assess the authenticity of specific foods or food classes based on dietary biomarkers.

Summary

New mass spec imaging and data analysis tools may usher in a fresh era of food quality testing where spatial distribution of compounds is used to identify additives and contaminants. The authenticity of foods may be associated with the localized presence (or absence) of key compounds that define the food source or type. The appearance of contaminants and their localization may also inform the use (or discontinued use) of certain packaging materials or processing steps.

References:

Application of Mass Spectrometry Imaging for Visualizing Food Components

MALDI mass spectrometry imaging of fresh and processed foods: constituents, ingredients, contaminants, and additives

Mass spectrometry imaging makes ingredients, additives, and contaminants of food visible

foodMASST a mass spectrometry search tool for food and beverages