14A-19

Inulin, a fructan with a degree of polymerization  (DP) between 2-65 monomers, consists of linear chains of fructose linked by b(2®1) bonds that terminate with a glucose monomer.  Fructooligosaccharide (FOS) has the same basic structure, but the fructose chains do not always terminate in a glucose unit and the DP is between 2-10 units.  Both fructans are prebiotic (bifidogenic) and escape hydrolysis from digestive enzymes.  The fructans are metabolized by colonic bacteria to produce short-chain fatty acids. 

 

Our objective was to evaluate the effects of inulin (average DP > 23) and two types of FOS (DP 3-5 and DP 2-7) on various properties of nonfat yogurt.

 

Plain, nonfat yogurt was made with 1, 2, 3 and 4% (wt/wt) of the assigned fructan, in addition to the control.  Yogurt was analyzed weekly for 4 weeks to determine syneresis, firmness, viscosity, pH, titratable acidity, sensory properties and microbiological counts. 

 

Yogurts made with FOS (DP 3-5) and inulin had significantly less syneresis than the control, with the fructans at the 4% level producing the yogurt with the greatest water-holding capacity.  Increasing levels of FOS had a negative correlation with yogurt firmness, with 4% FOS producing the least firm yogurt.  Yogurt made with 4% inulin was significantly more firm than the control at weeks 2-4.  The inulin and FOS (DP 3-5) significantly increased the yogurt’s resistance to flow when added at 4%.  Sensory analysis found the yogurts with FOS and inulin to be perceived as more smooth and more thick than the control.  Additionally, the yogurt with 4% FOS (DP 3-5) was rated with the highest overall acceptability. 

 

The results indicate that DP affects the functionality of fructans in nonfat yogurt.  Inulin and FOS can be added to nonfat yogurt at levels beneficial to the host while improving certain functional properties.