title: Fermentation optimization of goat milk with Lactobacillus acidophilus and Bifidobacterium bifidum by Box-Behnken design.
abstract: BACKGROUND
  Goat milk is only limited to the processing of goat milk powder and liquid milk, the products are mainly about milk powder and a few of them are made as milk tablet. Therefore, the study of probiotic goat milk will have great significance in the full use of goats and the development of the goat milk industry in China.
  
  
  METHODS
  The effect of fermentation temperature (35°C, 37°C, 39°C), strain ratio (1:1:1, 2:1:1, 3:1:1) and inoculum size (4%, 5%, 6%) on viable counts of L. acidophilus and B. bifidum, total bacteria and sensory value during fermentation process of L. acidophilus and B. bifidum goat yogurt (AB-goat yogurt) was investigated.
  
  
  RESULTS
  The optimum fermentation conditions for AB-goat yogurt were: fermentation temperature 38°C, the strain ratio 2:1:1, inoculum size 6%. Under the optimum conditions, the viable counts of B. bifidum, L. acidophilus, total bacteria and sensory value reached (4.30 ±0.11)×107  cfu/mL, (1.39 ±0.09)×108  cfu/mL, (1.82±0.06)×109  cfu/mL and 7.90 ±0.14, respectively.
  
  
  CONCLUSIONS
  The fermentation temperature, the strain ratio and inoculum size had a significant effect on the fermentation of AB-goat yogurt and these results are beneficial for developing AB-goat yogurt.
authors.affiliation: School of Food and Biological Engineering, Shaanxi University of Science and Technology Xi&#;an, China.
authors.forename: Guowei
authors.initials: G
authors.lastname: Shu
authors.affiliation: School of Food and Biological Engineering, Shaanxi University of Science and Technology Xi&#;an, China.
authors.forename: Chunju
authors.initials: C
authors.lastname: Bao
authors.affiliation: School of Food and Biological Engineering, Shaanxi University of Science and Technology Xi&#;an, China.
authors.forename: He
authors.initials: H
authors.lastname: Chen
authors.affiliation: School of Food and Biological Engineering, Shaanxi University of Science and Technology Xi&#;an, China.
authors.forename: Changfeng
authors.initials: C
authors.lastname: Wang
authors.affiliation: School of Food and Biological Engineering, Shaanxi University of Science and Technology Xi&#;an, China.
authors.forename: Hui
authors.initials: H
authors.lastname: Yang
mesh_terms: D000818:Animals; D000069985:Bifidobacterium bifidum / Q000378:metabolism*; D015169:Colony Count, Microbial; D005285:Fermentation; D005511:Food Handling; D005516:Food Microbiology; D006041:Goats; D007779:Lactobacillus acidophilus / Q000378:metabolism*; D008892:Milk / Q000737:chemistry / Q000382:microbiology*; D019936:Probiotics; D013649:Taste; D013696:Temperature; D015014:Yogurt / Q000382:microbiology
keywords: Bifidobacterium bifidum; Lactobacillus acidophilus; fermentation; response surface methodology; skimmed goat milk