Work

The promotion effects of flat-form ultrasound on fermentation efficiency, kinetic, and quality characteristic of room-temperature-storage yogurt

Year: 2025

Type: article

Abstract: Room-temperature-storage yogurt (RTSY) is becoming increasingly popular among consumers for its conveniences in storage and drinking. However, due to the addition of a secondary pasteurization after fermentation, the flavor and stability cannot be compared to traditional low-temperature-storage yogurt. We investigated the influence of flat ultrasound-assisted fermentation (FUAF) on the fermentation and quality of RTSY. Six different ultrasonic frequency combinations (20, 28, 35, 20/28, 28/35, and 20/35 kHz) were used in the treatments. The results demonstrated that applying ultrasonic treatment at 28 kHz and 40 W/L for 6 min during the initial stage of fermentation, and stopping the process at pH 4.50, yielded superior RTSY compared to other ultrasonic conditions. Under these optimized conditions, the counts of Lactobacillus bulgaricus and Streptococcus thermophilus in RTSY prior to secondary pasteurization increased by 90.53% and 94.76%, respectively. This enhancement significantly reduced the fermentation time from 5 h (control group) to 4 h. Additionally, the water-holding capacity improved by 11.51%. Kinetic model analysis revealed that lactic acid bacteria exhibited faster growth rates, higher lactic acid production, and accelerated glucose consumption. Furthermore, texture and rheological analyses indicated significant enhancements in hardness, adhesiveness, cohesiveness, and apparent viscosity, contributing to an overall improvement in product quality. Electronic nose and headspace solid-phase microextraction-gas chromatography-mass spectrometry (HS-SMPE-GC-MS) analysis showed that, sonication increased key volatile compounds related to flavor (such as acetaldehyde, 2,3-butanedione, etc.), and thus, enhanced the flavor characteristics. In conclusion, the use of FUAF, especially at 28 kHz, in the fermentation of RTSY was beneficial in enhancing the fermentation efficacy and quality of RTSY.

Source: Ultrasonics Sonochemistry

DOI: 10.1016/j.ultsonch.2025.107390