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• High-intensity ultrasound accelerated the maturation of soy sauce. • Reducing sugars and soluble salt-free solids were increased after ultrasonication. • The proportion of peptides (1–5 kDa) with umami taste was increased. • The content of free amino acids was decreased that mainly involved Maillard reaction. • Flavor compounds were largely generated, including esters, pyrazines, and ketones. High-intensity ultrasound was used as a means to promote maturation of soy sauce. The optimal conditions for ultrasound treatment were 90℃ at an ultrasound intensity of 39.48 W/cm2 for 60 min. The total reducing sugars and soluble salt-free solids content was significantly increased after ultrasound-assisted maturation. The free amino acid content was significantly decreased, mainly due to the Maillard reaction (MR). The promoted MR produced several types of flavor compounds, including esters, pyrazines, and ketones, which imparted an attractive aroma to the maturated soy sauce. The proportion of peptides with a molecular weight of 1–5 kDa provided umami as an important flavor characteristic, and the content in the ultrasound-matured soy sauce (10.19 %) was significantly higher than that in the freshly prepared soy sauce (8.34 %) and the thermally treated sample (8.89 %). Ultrasound-assisted maturation would improve product quality and meanwhile, shorten the duration and reduce the cost for the soy sauce industry. [ABSTRACT FROM AUTHOR]

A kinetic model for a high-intensity ultrasound-assisted Maillard reaction model system of d -glucose and glycine was proposed; activation energy ( Ea ) for each reaction step was calculated. Results showed that the generation of dicarbonyl compounds was significantly promoted by high-intensity ultrasound (e.g. Ea values for 1-deoxyglucosone were 60.9 ± 9.7 kJ mol −1 and 105.5 ± 9.9 kJ mol −1 in ultrasonic and thermal Maillard reaction, respectively), which resulted in a significantly higher concentration of colored and volatile Maillard reaction products generated in ultrasound-assisted Maillard reaction compared with that in thermal Maillard reaction. However, as a competitive reaction, the isomerization of d -glucose was suppressed and required significantly higher Ea values in ultrasound-assisted Maillard reaction (100.8 ± 6.2 kJ mol −1 ) compared with that in thermal Maillard reaction (84.2 ± 5.7 kJ mol −1 ). These finding may be attributed to an extremely high temperature and pressure environment, despite of being only momentarily, generated by high-intensity ultrasound. [ABSTRACT FROM AUTHOR]

• A Maillard reaction (MR) model system of d -glucose and l -lysine was investigated. • Generation mechanisms of furosine and pyrraline were revealed in the MR model system. • Furosine is preferred to undergo the reaction between methylglyoxal and l -lysine. • Pyrraline is preferentially started from 3-deoxyglucosone through Pyrrole reaction. A kinetic model for Maillard reaction (MR) model system of d -glucose and l -lysine was established; activation energy (Ea) of each step was calculated. Potential generation pathways of furosine and pyrraline were a combination of either 3-deoxyglucosone (3-DG) or methylglyoxal (MG) with l -lysine. Ea value for furosine generated through 3-DG pathway was 81.70 ± 14.01 kJ mol−1, which was significantly higher than that through MG pathway (52.08 ± 4.48 kJ mol−1). As for pyrraline, Ea for the 3-DG pathway (53.45 ± 4.02 kJ mol−1) was significantly lower than that through the MG pathway (110.22 ± 18.77 kJ mol−1). Results of the kinetic study indicated that furosine was preferred to be generated through the MG pathway since MG is more likely to react with each other and form a furan ring as a precursor of furosine. Pyrraline was more easily to be generated from the 3-DG pathway through cyclization of 1,4-dicarbonyl compounds to pyrrole. [ABSTRACT FROM AUTHOR]

• Potentials of ultrasound (US) in food fermentation and maturation are reviewed. • US stimulates growth of microorganisms, promotes enzyme activities and metabolisms. • US promotes Maillard reaction, esterification, and proteolysis during food maturation. • Texture, sensory, and functional properties of fermented foods are improved by US. • US has a great potential to improve fermentation efficacy and fermented foods quality. Conventional food fermentation is time-consuming, and maturation of fermented foods normally requires a huge space for long-term storage. Ultrasound is a technology that emerged in the food industry to improve the efficacy of food fermentation and presents great potentials in maturation of fermented foods to produce fermented foods with high quality. Proliferation of microorganisms was observed along with promoted enzyme activities and metabolic performance when treated by a short-term ultrasonication (<30 min) at a relatively low-power (≤100 W). Additionally, ultrasound at a high-power level (≥100 W) was highlighted to promote the maturation of fermented foods through promoting Maillard reaction, oxidation, esterification, and proteolysis. As a result of promoted fermentation and maturation, texture, color, flavor and taste of fermented foods were improved. All the reviewed studies have indicated that ultrasound at the proper conditions would be a promising technique to produce fermented foods with high-quality. [ABSTRACT FROM AUTHOR]