Browsing by Subject "termoviili"

Lactic acid bacteria Streptococcus thermophilus and Lactobacillus delbrueckii ssp. bulgaricus are used for yoghurt manufacture. Traditional Northern fermented milk products are typically made with mesophilic species. In traditional Finnish product, viili, also secondary culture of Geotrichum candidum is used. In Finland during last 20 years, the consumption of yoghurt is doubled while the consumption of viili has dropped by half. The aim of this study was to continue the research for designing a novel fermented milk product ”termoviili”. The aim is to develop a product that combines the main flavour compound of yoghurt, acetaldehyde, to Geotrichum candidum. There were 12 LAB strains in this study. Their ability to grow in UHT-milk and produce acetaldehyde was studied. The acetaldehyde level, microbial growth and final pH were measured. Also strain identifications were done by using PCR-methods. All the LAB strains studied were able to grow at target temperature (+ 30°C). The amount of acetaldehyde produced varied between 0−22,5 mg acetaldehyde / 1 litre product. The main problem with all the LAB strains studied was their poor ability to decrease the pH of the milk fast enough and without any supplements. Growth supplement (sodium formate) and the addition of G. candidum were found to speed up the decrease of pH in some cases. The best strain to produce acetaldehyde was isolated from a commercial product and it was confirmed as Lactobacillus delbrueckii. According to Cheng (2010) good flavoured yoghurt results when 23−40 mg/kg and at least 8−10 mg/kg of acetaldehyde are produced. Based on this evaluation, the amount of acetaldehyde found in this study, is sufficient to produce enough yoghurt aroma to the final product. More study need to be done to speed up the decrease of pH and to optimize the recipe. Also different strains of G. candidum should be tested for the possibility to increase the incubation temperature.