MODEL RELEASED. Yoghurt manufacture. Technician attending to factory equipment used to make thermally treated yoghurt. Yoghurt is made by adding a bacterial culture of Lactobacillus acidophilus and Streptococcus thermophilus to milk. The bacteria are introduced to a fresh batch of concentrated milk by adding a portion of a previous batch. Thermally treated yoghurt is then pasteurised to kill the culture and improve the product's storage life. Yoghurt is widely consumed as a health food.