Towards galactose accumulation in dairy foods fermented by conventional starter cultures: Challenges and strategies

• Effects of accumulated galactose on functionalities of dairy foods are discussed.
• Metabolism of lactose/galactose in lactic acid bacteria is discussed.
• Distribution of Tagatose-6P and Leloir pathways in sequenced LAB is highlighted.
• Potential solutions for reducing galactose in fermented milk are suggested.

Galactose normally accumulates in dairy foods after milk fermentation with conventional starter cultures and gives rise to serious effects on functionalities of fermented dairy foods. Tagatose-6P pathway (lac operon) and Leloir pathway (gal operon) are responsible for lactose/galactose metabolism in lactic acid bacteria (LAB). Leloir pathway is a common pathway in LAB whereas Tagatose-6P pathway is mainly found in Lactobacillus casei, Lactobacillus rhamnosus, Lactococcus lactis subsp. cremoris, Enterococcus faecium, and Enterococcus faecalis. This review provides new insights into using specific above LAB as starter culture for galactose reduction in fermented dairy foods.