Ionicon Analytik Ges.m.b.H.

PTR-MS systems for food & flavor science - Food and Beverage - Food

Aroma real-time quantification with PTR-MS. Rapid screening for complex aroma systems. Rich chemical fingerprints due to soft ionization. Real-time sampling: high throughput. Ideal for chemometric data-mining methods.

The challenge

Aroma and its perception can influence buying decisions. It is therefore indispensable for the industry to understand what we smell and taste when e.g. drinking a cup of coffee or enjoying a piece of chocolate, at the very moment the flavor molecules hit our receptors.

Flavor and taste of food can also vary over time, depending on raw materials or production processes etc. For a consistent brand image however, the aroma quality of food should remain stable. 

Coping with requirements such as very high time resolution, basically real-time and direct air sampling are challenges to traditional analytical techniques. 

IONICON PTR-MS – ultra sensitive for real-time trace VOC analysis

In order to provide scientists and the industry with a better understanding of sensory perception, IONICON provides real-time VOC analyzers and is the market leader in Proton Transfer Reaction – Mass Spectrometry (PTR-MS).

The key benefits include:
• Chemical fingerprints of food samples in real-time
• Head-space analysis of products without sample preparation
• Direct mouth- & nose-space air analysis 
• Rapid screening of complex aroma systems due to soft chemical ionization and high-resolution mass spectrometry
• Monitoring of real-time variations in aroma 
• Suitable for chemometric datamining 
The results provided by IONICON PTR-MS enhance research, flavour & fragrance development, quality control and allow for process monitoring in food & flavour industries.

In food and flavor science researchers are often confronted with highly complex matrices. Thus, in order to separate compounds of interest from other compounds which share the same nominal m/z but have a different chemical composition (isobars), very high mass resolution is of utmost importance.

By introducing trichlorobenzene from a certified gas standard we determined the Full Width at Half Maximum (FWHM) mass resolution of an IONICON PTR-TOF 6000 X2 with over 6200 m/Δm (Fig. 1).

To demonstrate the benefit of this outstanding resolution we analyzed the nosespace of a person who had consumed some freshly brewed coffee. It is well known that vanillin and 4-ethylguaiacol are important isobaric aroma compounds at nominal m/z 153 (protonated molecules). 

However, by looking at the mass spectrum around m/z 153 in Fig. 2 one can see that there are in fact four ions which share this nominal mass (black line). For a low resolution instrument all four ions would be merged into one broad mass spectral peak and only the intensity of the sum of them could be measured. The high mass resolution of the PTR-TOF 6000 X2 enables separation of all four ions. With IONICON's sophisticated data processing software the intensities are automatically deconvoluted (grey and blue lines; the orange line is the sum of the deconvoluted peaks, which perfectly reproduces the original data) and vanillin and 4-ethylguaiacol can be quantified independently, without parasitic influence of the two additional isobars.

High sensitivity is particularly important when compounds of extremely low abundance have to be quantified with high time resolution. Utilizing the high sensitivity PTR-TOF 6000 X2 we analyzed the nosespace of a person before (blank) and after drinking freshly brewed coffee. In Fig. 3 concentration values of 3-mercapto-3-methylbutyl formate at m/z 149.063 are shown during this experiment with a time resolution of 700 ms. Although this important aroma compound is present only in trace concentrations below 1 ppbv, the high sensitivity and low limit-of-detection of the PTR-TOF 6000 X2 allow for online quantification of the aroma development over numerous breath cycles after swallowing the coffee in real-time.

This novel and efficient approach of characterizing the aroma of coffee blends by on-line analysis may shorten the time required for the development of new products and improve quality control in a more automated and objective manner.

Analytical studies and sensory profiling is performed on different commercially available espresso coffee products. On-line analysis with IONICON PTR-MS is used to obtain chemical information about difference in composition of the coffee headspace characterizing the different coffee blends. In addition, an expert panels trained for coffee tasting describe each sample by scoring 10 key flavor attributes on a 10-point scale.

The overall sensory description of each sample is correlated with the analytically obtained differences in chemical composition in order to develop a statistical tool to predict the sensory profile based on analytical data. In a second step, the prediction is validated using a new series of coffee blends, which differ in the aroma profile and which are not included in the development of the predictive tool.

The overall sensory prediction of the new blends based solely on the analytically generated data shows a good match with the sensory profiles independently obtained by the expert panel.

When PTR-MS Tastes Coffee

Instrumental Approach To Predict the Sensory Profile of Espresso Coffee

A major step forward in terms of correlation of sensory with instrumental results has been achieved by Lindinger et al of the Nestlé Research Center in Switzerland using IONICON PTR-MS.

The scientists were able to develop a robust and reproducible model to predict the sensory profile of espresso coffee from instrumental headspace data.

PTR-MS with its online measurement capabilities enable researchers to quantify compounds in the nose-space air of test persons. A very low detection limit and a high time resolution allow for real-time aroma-release analysis. Insights for aroma design and flavor research can be gained through correlations between individual food perception and measured in-nose aroma concentration.

Results of PTR-MS measurements - mastication of strawberries

The graph shows a peak of isoprene (red line), an endogenous compound produced in the body, with each exhalation occurring approximately every eight seconds. When strawberries are chewed (start after 80 seconds) aroma compounds like methy-2methyl-butanoate, are released and can be measured in each exhalation.

For the real-time analysis of flavor compounds in nose-space air, IONICON has developed the N.A.S.E., an inlet system for PTR-MS optimized for this application. 

PTR-MS in Saffron Quality Control

PTR-MS can be used in the quality control of saffron. Saffron is a spice derived from the flower of Crocus sativus, and is among the world's most costly spices by weight. Despite attempts at quality control and standardisation, an extensive history of saffron adulteration, particularly among the cheapest grades, continues into modern times. 

By monitoring of VOCs from a minute amount of sample (35 mg) over a 5 weeks period researchers have found that the of initially dominant VOC safranal (m/z 151) decreased progressively. Nenadis et al. further report that examination of calculated and recorded fingerprints for various admixtures showed that PTR-MS VOCs analysis, in combination with chemometrics, could be used to screen for the presence of lower quality saffron in a commercial product in a few minutes. PTR-MS can be used in a complementary fashion, adding to the battery of advanced analytical techniques available to address the quality and authenticity issues of saffron.
High-throughput screening of food & flavor samples is now even more comfortable and faster, thanks to the IONICON autosampler.

Freshness of food in the consumer's perceptions