Keeping a live-probiotic strain viable through spray-drying — what works?

Viability loss in drying is mostly osmotic/oxidative stress and membrane damage. What works: (1) protectants in the feed — trehalose/sucrose, skim milk, maltodextrin; (2) gentle inlet/outlet temps and controlling outlet water activity; (3) harvest cells in stationary/stress-adapted phase; (4) pack under low O2 / low humidity. Spray-drying is cheaper than lyo but harsher — for very fragile strains lyo or fluidized-bed still wins. Validate CFU retention through drying AND shelf-life, not just post-drying.