How to get rid of mildew?

[Klara]

Yes, the leather is as white as in the picture  - some sort of mould or mildew. I have cleaned the bags several times with saddle soap, they were stored in a dry place and with plenty of air (not under cover). The mildew always returns. A few years ago even while the bags were in use in my living room. Any ideas (apart from binning them)?

[Beehive]

I believe the mold is feeding on whatever the leather was oiled with. It'll continue to feed on it. 

Since it's already a mess. Spray it down with lemon juice and lay it in the sunlight. Rotate it around for a day. Or apply a mold killer like, "Mold Armor". Let the item dry out.

Afterwards apply a conditioner and store in a ventilated area. Stuff the bags with brown paper to absorb any extra moisture.

 

If that doesn't work, either burn it or bury it. Just keep it away from other tack.