The bitter taste often found when eating almonds has been identified by scientists in Spain. The culprit has a name: amygdalin, a diglucoside that, when in contact with enzymes present in saliva, breaks down into glucose, benzaldehyde (the cause of the bitter taste) and hydrogen cyanide. A research team from the University of Cordoba thinks it has found a way to test for the chemical, which could put an end to bitter almonds once and for all.

To reduce this unpleasant ‘surprise’, the Farming Systems Engineering and Food Technology research groups at the University of Cordoba’s School of Agricultural and Forestry Engineering, with collaboration from the Andalusian Institute of Agricultural Research and Training’s Alameda del Obispo Center, developed a method that can predict levels of the aforementioned amygdalin present in nuts analysed both with and without shells.

In addition, the team says its methods can correctly classify sweet almonds and bitter ones on an industrial scale, something that has only been done with shelled nuts, individual kernels or ground nuts to date.

The new system uses portable equipment based on NIRS technology (Near Infrared Spectroscopy) which can analyse large amounts of a product in situ in real time, without having to go into a lab.

This technological application is “of great interest to the farming sector”, explained Professor Dolores Pérez Marín. Almond bitterness in the wild can be helpful to prevent predators from ingesting the seeds of certain varieties. Yet on an industrial scale this bitterness offers no advantages and many disadvantages: an unpleasant taste, product devaluation and potential problems with food safety if consumption of bitter nuts occurs on a large scale.

The NIRS sensors use a beam of light which, when interacting with organic matter, returns a unique signal (spectrum) for each product sample – an unmistakable digital print that provides information and allows us to define the sample.

In this case, as explained by doctoral student and first author of the research paper, Miguel Vega Castellote, the portable sensors, “whose signal along with the reference values allow for the development of prediction models”, are able to analyse different parameters by “scanning” the product quickly and noninvasively, without modifying it.

Food fraud

Using NIRS technology is especially useful in the early detection of possible fraud and in food authentication, according to the researchers. Therefore, the team has initiated another research project aimed at detecting batches of sweet almonds adulterated with bitter ones and in which almost 90 percent of the fraudulent items were identified.

The system tested in this research “could be implemented at any point in the value chain, including upon reception, during processing and shipping, and could be used as a fast and affordable anti-fraud early warning method,” said Professor María Teresa Sánchez Pineda de las Infantas, another author of the paper.