Effect of Ultrasonic Frequency on Lactic Acid Fermentation Promotion by Ultrasonic Irradiation

Abstract

The authors have been researching the promotion of lactic acid fermentation by ultrasonic irradiation. In the past research, it was proven that ultrasonic irradiation is effective in the process of fermentation, and the production of yoghurt and kefir was promoted. In this study, the effect of the ultrasonic frequency in this fermentation process was examined. In the frequency range of this study, it was found that the action of fermentation promotion was exponentially proportionate to the irradiated ultrasonic frequency.

Stimulating fermentative activities of bifidobacteria in milk by highintensity ultrasound

“…It was suggested that the phenomenon was due to an increase in the transport rates of oxygen and nutrients into the cells and waste products away from the cells. In previous studies on milk fermentation by lactic acid bacteria, the promoting action of ultrasound was explained as being due to either the agitation effect of ultrasound and/or a local slight temperature rise inside the solidified milk by the heat derived from ultrasonic absorption, which activates the lactic bacteria (Shimada et al, 2004), or an improvement in lactose transport and a release of intracellular enzymes such as b-galactosidase (Wang & Sakakibara, 1997;Wu et al, 2000). In our current study, another mechanism can be hypothesized.…”

“…In the production of fermented milk products, a number of studies have shown that ultrasound improves the acidifying activity of lactobacilli, thereby reducing production time and, whilst accelerating lactose hydrolysis, it induces a sweetening effect in yoghurt without increasing the caloric content (Kreft & Jelen, 2000;Masuzawa & Ohdaira, 2002;Povey & Mason, 1998;Shimada et al, 2004;Toba, 1990;Wang & Sakakibara, 1997;Wu et al, 2000).…”

Effects of ultrasound on the fermentation profile of fermented milk products incorporated with lactic acid bacteria

“…Reducing the fermentation time in cultured dairy products by US is one of the most promising approaches that has been identified previously in the literature (Barukčić, Jakopović, Herceg, Karlović, & Božanić, 2015;Nguyen, Lee, & Zhou, 2009;Riener et al, 2010;Sfakianakis et al, 2015;Shimada, Ohdaira, & Masuzawa, 2004;Wu, Hulbert, & Mount, 2001).…”

“…Apparently, the effect of US on fermentation time may rely on process parameters such as acoustic intensity, frequency, treatment duration, the point of application (before inoculation or after inoculation) and the composition of milk. In an initial investigation, Shimada et al (2004) found that the fermentation time of a kefir culture (time at which the pH reaches 4.5) was shortened exponentially when the sonication frequency was increased from 28 kHz to 200 kHz during fermentation. Consequently, authors suggested that ultrasonic waves promoted the fermentation process under conditions where cavitation was not generated, and was suppressed when cavitation occurred.…”

“…However, the influence of factors such as different milk composition, (Ewe, Abdullah, Bhat, Karim, & Liong, 2012;Nguyen et al, 2009;Wang & Sakakibara, 1997;Wu et al, 2001). Another mechanism, proposed by Shimada et al (2004) and Piyasena, Mohareb, and McKellar (2003), is that a slight local temperature rise due to the heat derived from ultrasonic absorption may activate the lactic bacteria and shorten the fermentation time. Moreover, Pitt and Ross (2003) suggested that US may accelerate the supply of oxygen and nutrients for microorganisms and increase the discharge of waste products from the cells, thus enhancing microbial cell growth.…”