The effect of ultrasound process on lactic acid bacteria, physicochemical and sensory properties of yoghurt, before and after inoculation of starter cultures into milk

Abstract

The effect of ultrasound (US) applied before (US + i) and after (i + US) inoculation of yoghurt starter into cows' milk on some parameters of yoghurt was investigated. Lightness (L*) values, amounts of acetaldehyde, diacetyl, acetoin, ethanol, lactic, pyruvic, and acetic acid were higher in the US-treated groups compared with control (P < 0.05). In the US + i group, the total amount of ketones increased. Lactobacillus and Streptococcus spp. numbers reached log =7.0 cfu/g in all groups (P > 0.05). It can be concluded that low-intensity ultrasound applied to cows' milk before or after inoculation of yoghurt starters increases the aroma components and organic acid content of yoghurt.