15B-3 |
Effects of EPS producing Streptococcus thermophilus strains on functionality of low fat Mozzarella cheeses |
N. P. SHAH and B. Zisu. School of Life Sciences & Technology, Victoria Univ., PO Box 14428, Melbourne City Mail Centre, Melbourne, VIC, 8001, Australia Many strains of lactic acid bacteria, including Streptococcus thermophilus synthesise extracellular exopolysaccharides (EPS). EPS may remain attached to the cell wall (capsular EPS) or may be excreted into the surrounding medium (ropy EPS). EPS helps retain moisture in Mozzarella cheeses. The objective was to study the effects of ropy and capsular EPS producing S. thermophilus strains on functionality of low fat Mozzarella cheeses. Eighty strains of S. thermophilus were screened for the production of capsular and ropy EPS using the wet-film India-ink staining technique. Positive strains were further screened on the basis of viscosity of the medium and the quantity of EPS produced. Selected ropy and capsular EPS strains were used for the cheese manufacture. Three batches of low fat (~6%) Mozzarella cheeses were manufactured by pairing the same EPS negative Lactobacillus delbrueckii spp. bulgaricus strain with EPS negative, capsular EPS or ropy EPS strain of S. thermophilus. Cheeses were compared in terms of their textural properties, melt, pizza bake characteristics and yield. Twelve of 80 strains of S. thermophilus were identified as capsular EPS producers. Of the twelve EPS capsular strains, 2 strains excreted ropy EPS. Capsular EPS and ropy EPS strains were used for the cheese manufacture. The moisture levels were higher in Mozzarella cheeses made with capsular EPS producing S. thermophilus starter cultures than those made with EPS negative cultures. Cheeses made with the ropy EPS strain showed the greatest moisture retention. The texture properties, melt, pizza bake characteristics and yield improved with an increase in moisture content; however, cheeses made with ropy EPS strains showed excessive and sticky water seepage. EPS producing S. thermophilus strains, particularly those producing capsular EPS can be utilised to increase the moisture content in low fat Mozzarella cheese leading to improvement in functionality.
Session 15B, Dairy Foods: Chemistry, microbiology and sensory analysis of various cheeses
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