Lipid oxidation of deoiled soy lecithin by lactic acid bacteria

Gas chromatography-mass spectrometry analysis revealed that lipid oxidation products such as (E,E)-2.4-nonadienal. (E,Z)-2,4-decadienal, and (EE)-2,4- decadienal were formed in a deoiled soy lecithin-reduced fat milk system du ring 24 h of fermentation by Lactococcus lactis at 32 degreesC. In addition , initial numbers of L. lactis (10(2) or 10(6) cfu/mL milk) and sot, lecith in content (0.2 or 2.0 g/100 mL milk) affected the formation of these 2,4-a lkadienals in fermented lecithin-milk system. These 2,4-alkadienals were de tected in reduced fat milk containing 0.2 g soy lecithin/100 mL milk (the l owest concentration investigated) and initial culture numbers of 10(2) cfu/ mL, milk. Other lactic acid bacteria. Lactococcus cremoris, Streptococcus t hermophilus, Lactobacillus helveticus, or Lactobacillus bulgaricus ssp. wer e subsequently evaluated in a deoiled soy lecithin-reduced fat milk system alone lecithin concentration (2.0g lecithin/100 mL milk. 10(2) cfu/mL milk) and also produced 2,4 alkadienals. Sensory evaluation confirmed the presen ce of typical lecithin associated off-flavors (mayonnaise/bread) in all fer mented milks containing lecithin across the concentration used in this stud y (0.2-2.0g/100 mL milk).