Effect of hawk tea (Litsea coreana L.) on the numbers of lactic acid bacteria and flavour compounds of yoghurt

Hawk tea (Litsea coreana L.) leaves were added to reconstituted milk at 2% and 4% (w/v), and inoculated with yoghurt starter to obtain hawk tea yoghurts (HTY2 and HTY4). The number of Streptococcus thermophilus, Lactobacillus acidophilus, and Lactobacillus casei in the hawk tea yoghurts were significantly higher than those in the control yoghurt (p < 0.05). In addition to 25 volatile components identified in the control yoghurt, (−)-spathulenol, α-cubebene, cadina-3, 9-diene, eudesma-4(14) and 11-diene were detected in the hawk tea yoghurts, and the amounts of acetaldehyde, caprylic aldehyde, nonanal and decanal were significantly higher than those in the control yoghurt (p < 0.05), and the relative amounts of diacetyl, acetoin and 2-heptanone also increased. All the results suggest that L. coreana L. promoted the metabolism of lactic acid bacteria in the yoghurt.