High-throughput differentiation of Streptococcus thermophilus and Lactobacillus spp. strains used in Swiss cheese production by infrared microspectroscopy
Advisor:Rodriguez-Saona, Luis E.
Contributors:Kocaoglu-Vurma, Nurdan A
Harper, W. James
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Series/Report no.:Food Science and Technology. Graduate student poster competition, 2009
Swiss cheese production in US was 310 million lbs (3.2% of total cheese production) in 2008. Ohio is the leading Swiss cheese producer in the US, supplying over 42% of the total US production. Strain variations of starter cultures have an impact on final quality and hence the price of Swiss cheese. A rapid and cost-effective method for identification and differentiation of starter cultures at strain level could help maintain uniform quality of Swiss cheese. The study was focused on developing a high-throughput technique to identify and differentiate Streptococcus thermophilus and Lactobacillus spp. strains involved in Swiss cheese production using the combination of hydrophobic grid membrane (HGM) filters and Fourier transform infrared (FTIR) microspectroscopy. Strains of S. thermophilus (14) and Lactobacillus spp. (15) were analyzed. Aliquots (2 µL) of each strain were transferred onto a grid of the HGM filter vacuum dried in a desiccator and analyzed using FTIR microspectroscopy. The procedure was repeated on six different days to account for growth variability. The spectra were analyzed by soft independent modeling of class analogy. The pattern recognition analysis showed tight clustering at the strain level for models developed for S. thermophilus and Lactobacillus spp. The models showed unique patterns in the spectral region from 1150 to 1000 cm-1 for the major discrimination in the S. thermophilus and Lactobacillus spp. that can be attributed to differences C-O stretching of polysaccharides. This method could be an effective tool to identify and monitor activity of dairy cultures.
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