'Magnetic tongue' may help improve processed food development

Researchers from University of Aarhus in Denmark and University of Naples, Italy, tested the potential of nuclear magnetic resonance spectroscopy (NMR) as a predictive tool to measure sensory descriptors of foods - using 18 different types and brands of canned tomatoes as an initial model.

Writing in the Journal of Agricultural and Food Chemistry​, the team reported that they were able to correlate the NMR metabolomic fingerprints recorded for canned tomato samples to sensory descriptors for bitterness, sweetness, sourness, saltiness, tomato and metal taste, redness, and density; “suggesting that NMR might be a very useful tool for the characterization of sensory features.”​

“In particular, we have used an NMR metabolomic approach that allowed us to differentiate the analyzed samples based on their chemical composition,”​ wrote the authors, led by Dr Anders Malmendal, associate professor at Aarhus.

Flavour perception​

The research team explained that the perception of odour and flavours from food “is a complicated physiological and psychological process that cannot be explained by simple models.”

“This is because hundreds of compounds simultaneously influence the human olfactory receptors and because the physiological response is far from linear, and the overall effects are not just the superimposition of the effect of single stimuli,”​ they highlighted.

Malmendal and his colleagues added that in addition to the effect of complex combinations of ingredients in food, flavour perception is also somewhat altered by the taster’s emotional state.

They noted that whilst trained taste testers eliminate some of the variation, food manufacturers and researchers developing new products need more objective ways to measure the sensory descriptor of their products.

“Unfortunately, the more usual artificial tongue/nose are used to determine very specific components of the analyzed food. Furthermore, not all instrumental techniques are able to analyze directly the genuine mixture interacting with our sense without any extraction/concentration procedure,” ​said the authors.

In the new study, the team investigated the ability of nuclear magnetic resonance spectroscopy – which has been used to investigate the taste of wine – to analyze the taste of canned tomato, without the use of any other chemical analysis.

Tomato analysis​

Malmendal and his co-workers reported that the MNR data provided a number of sensory descriptors that were easily matched to sensory interpretation, including: bitterness, sweetness, sourness, saltiness, tomato and metal taste, redness, and density.

“The presence of a number of bitter amino acids like isoleucine, tryptophan, tyrosine, phenylalanine, and valine is correlated with bitterness and surprisingly to sourness,”​ reported the authors, who added that other amino acids – like glutamate, glutamine, aspartate, and asparagines – seemed to have a crucial role as taste enhancers that amplified bitter, sour, and cooked taste.

They added that ingredients such as citrate, malate, formiate, and acetate were correlated with sourness.

“Very interestingly, citrate and particularly malate seem to be crucial in the defining the taste of tomato,”​ said Malmendal and his team.

They added that the results of the study suggest that NMR “could be a very useful tool for the characterization of some sensory features” and said that further experiments to evaluate the applicability of this methodology to other kinds of food are currently underway in the labs.

Source: Journal of Agricultural and Food Chemistry​
Volume 59, Issue 20, Pages 10831–10838, doi: 10.1021/jf203803q
“NMR Spectrometers as “Magnetic Tongues”: Prediction of Sensory Descriptors in Canned Tomatoes”​
Authors: A. Malmendal, C. Amoresano, R. Trotta, I. Lauri, S. De Tito, E. Novellino, A. Randazzo