Abstract

                                A study was undertaken to produce freeze-dried herbal bio-yoghurt with Lactobacillus delbrueckii subsp. bulgaricus, Streptococcus thermophilus, and an additional probiotic strain Lactobacillus rhamnosus GG. Aqueous extract of licorice (Glycyrrhiza glabra) at different concentration levels (0.5, 1.0, 1.5, 2.0, 2.5%) was incorporated into the yoghurt, to study the effect of licorice as a prebiotic in promoting the growth of yoghurt starters and Lactobacillus rhamnosus GG. The incorporation of licorice extract at different levels positively affected the total viable count of the bio-yoghurt. Antioxidant properties of the herbal bio-yoghurt were analysed and it ranged between 39.26±0.02 and 68.13±0.04% when compared to control yoghurt (22.08±0.03%). The optimum level of incorporation of licorice extract was standardized based on the physico-chemical, functional, and viability of microbes. Among the five different levels of incorporation of herbal extract, 2% level was ideal based on the sensory and physico-chemical parameters for the preparation of herbal bio-yoghurt. On freeze-drying the herbal bio-yoghurt with trehalose and lactose as cryoprotectants, trehalose showed more promising results in protecting the viability of microbes during freeze-drying when compared to lactose, and there was no significant difference between two cryoprotectants and control concerning acidity, pH, moisture and ash of the freeze-dried herbal bio-yoghurt

Key words : Licorice; Bio-yoghurt;Freeze drying; Cryoprotectant; Yoghurt Powder