| Topic: | Comparison of yogurt starter powder preparation by spray dry and freeze dry |
| Abstract: | The research aimed to compare the yoghurt starter powder production by spray drying and freeze drying. Due to the most fermented milk industries have to use lactic acid bacteria, So they must be imported from other countries with higher cost and time consuming. Therefore this work was tried to develop starter culture in the form of yogurt powder products. The research was done by yoghurt fermentation with 3 types of starter cultures (A, B and C) and then drying into powder by spray and freeze dry methods. Spray dried method was conducted by using inlet temperature of 160 ± 5 °C and outlet temperature about 85±5 °C with feed flow rate 1.0-1.3 L / h. While the freeze dried method was done by freezing at -40 ° C for 1 hour before taking to freeze dryer at -80 °C with the pressure at 0.5 bar for 24 hours. After that, one type of starter culture was selected by using growth rate during yoghurt production, sensory evaluation of yoghurt and survival number of microorganisms after drying. The parameters of fermentation steps, pH, acidity, time of fermentation and growth rate were also compared. The results showed that among 3 types of starter cultures, starter cultures type C showed the highest total microorganisms of 1.40 x 1011 CFU/g, after fermentation for 18 hours. While the pH and total acidity was similar to starter cultures type A but better than starter cultures type B. Therefore, starter cultures type C was chosen as starter culture in yogurt powder production. After yogurt fermentation process was done, encapsulation process by using maltodextrin and octenyl succinic anhydride modified starch (OSA) as a carrier was applied to yogurt before dried. The best results were obtained by using octenyl succinic anhydride modified starch (OSA) carrier, the survival number of microorganisms of yogurt powder after spray drying and freeze drying were 4.3x109 and 1.6x109 CFU/g, respectively, after that, the shelf life was studied. Then yogurt starter culture powder was kept at -18 oC for 45 days. The results showed the survival number of microorganisms at 45 days of yogurt powder from spray dry and freeze dry preparation were 5.3x106 and 1.2x106 CFU/g, respectively. The sensory tests of both starter cultures type C, spray dry and freeze dry was no significantly difference. |
| Author: | 59403201 :
Asst. Prof. Pornsri Charoenpanich, Ph.D.
Asst. Prof. Arunsri Leejeerajumnean, Ph.D. |