Effects of high-intensity ultrasound and oil type on the Maillard reaction of d-glucose and glycine in oil-in-water systems

This study addresses the effect of high-intensity ultrasonic processing on four oil-in-water systems, using sunflower, peanut, olive and flaxseed oils, respectively, that contained an aqueous d-glucose and glycine Maillard reaction (MR) model system. The MR in the water phase was promoted as observed from higher depletion of reactants and higher amount of MR products (MRPs). A significantly higher amount of pyrazines was generated after ultrasonic processing, particularly in the sunflower and olive oil systems. These promotions were attributed to a well-mixing effect and a localised high temperature and pressure environment generated by the high-intensity ultrasound. However, upon 1h of ultrasonic processing at 80 degrees C, a significant increase of oxidation was observed with high peroxide and p-anisidine values in the post-processed oils; meanwhile, the amount of unsaturated fatty acids decreased as well. As a result, some off-flavours were also detected in the post-processed oils, which affected the overall flavour profile of the MR systems. Food processing: ultrasound betters flavour off sugar and amino acidUltrasound generates more flavour species in oil-in-water mixtures containing sugar and amino acid than heating, but meanwhile degrades oils. Weibiao Zhou at National University of Singapore and collaborators in China studied the effect of high-intensity ultrasonic processing on model food systems with sugar and amino acid in mixtures of water and different oils. The researchers found that high-intensity ultrasound can speed up the Maillard reaction, a chemical reaction that yields various flavour compounds from amino acids and reducing sugars, because it can induce a temporary condition of high temperature and high pressure and promote the mixing between water and oil. On the other hand, ultrasound is responsible for increased oxidation of unsaturated oils, leading to off-flavours and loss of nutrients. These results may help improve ultrasound-assisted food processing techniques.