Effect of microwave combined with ultrasonic pretreatment on the flavor of composite stewed soup-stock

In order to increase the content of flavoring components and nutrients in the stock, effects of microwave (MW) combined with ultrasonic pretreatment on water-soluble proteins, flavor nucleotides, volatile gas constituents and sensory evaluation in the stewed stock were explored. The results showed that, compared with the control group (CK), MW, and ultrasonic (US) pretreatment could significantly promote the degradation of nucleotides and form a large number of 5′-flavor nucleotides. The combined treatment of MW and US promoted protein hydrolysis and increased the content of water-soluble protein. The microwave combined ultrasonication pretreated stew stock had the brightest color and the overall sensory score was better than that of the CK. In addition, GC–MS analysis showed that a total of 49 volatile substances were detected in the stock samples. After microwave combined ultrasonication pretreatment, the relative contents of aldehydes and alcohols in the stock increased significantly. The sensor response value of the electronic nose was the highest, indicating that the intensity of flavor characteristics increased. Therefore, MW combined with ultrasonic pretreatment can effectively promote the formation and dissolution of nutrients, and increase the content of flavorful nucleotides and volatile gases.

Practical application

This study provides a novel processing method for traditional stewed stock. Ultrasonic combined with MW treatment can quickly degrade the protein in the raw material and dissolve it into the stock. At the same time, it promotes the formation of flavor nucleotides and accelerates the Maillard reaction to produce more flavor substances. The technology has the advantages of short processing time, environmental protection and safety. It can be used as a potential pretreatment technology to regulate the flavor of stock-soup.