Yogurt Starter Obtained from Lactobacillus plantarum by Spray Drying

Abstract

Probiotics have been known to mankind for many centuries and the quest for its health benefits is increasing in this century through focused research on various food products. Researchers have a growing interest in probiotics starter cultures for fermented milk products. Lactobacillus plantarum MA2 was isolated with good fermentation characteristics from Tibet kefir and identified by morphological, physiological, biochemical, and 16S rDNA sequence analysis. This work focused on the preparation of MA2 starter cultures by spray drying and compared the physiological activity of starter cultures to that of freeze-dried powder. The experimental results showed that the best spray-drying conditions were as follows: inlet air temperature of 148.9°C, raw material flow rate of 61.5 mL/h, and a protectant : cell ratio of 3:1. The viable cells of spray-dried starter cultures was 1.82 × 10⁹ colony-forming units (cfu)/g. The in vivo experiments revealed that after the spray-drying process, starter cultures of MA2 had good milk curdling and cholesterol removal ability (45.5%), which was very close to the fresh bacteria broth (46.8%) and freeze-dried starter cultures (46.1%). Furthermore, the spray-dried starter cultures had good stability during storage at 4°C. These results showed that the modified spray-drying process achieved the intended purpose of efficient preparation of the yogurt starter cultures.

Keywords:

• Cholesterol removal rate
• Lactobacillus plantarum MA2
• Response surface methodology
• Spray drying
• Yogurt starter cultures

ACKNOWLEDGMENTS

This work was supported by the National Nature Science Foundation of China (Grant No. 31171629) and a grant from the Research Fund for the Doctoral Program of Higher Education (Grant No. 20091208110001), and a National High Technology Research and Development Program (“863” program) of China (No. 2011AA100904).

Notes

Optimization of spray-drying conditions was conducted using a CCD.

^a The factors were encoded, which affects cell survival of L. plantarum MA2 during spray drying.

^b The coded levels and actual levels were used for experiments according to the CCD.

A = inlet air temperature, B = inner speed, C = proportion of protectants and cells.

Significantly different from viable cells of spray-dried starter culture, p < 0.05.

^a A comparison of the activity of the starter powder was performed among the control (fresh broth), spray-dried culture, and freeze-dried culture. The activity included time of milk curdling and pH, cholesterol removal rate, and viable cells.

A = freeze-dried starter culture powder, B = spray-dried starter culture powder.

*Indicates significant difference from the corresponding freeze-dried powder at p < 0.05 determined using T-test.