Study: the impact of freezing techniques on lactobacilli survival rates

Preserving viable lactobacilli is an important part of developing probiotic foods and powders – freeze-drying is one method used to get the bacteria from A to B in one piece. We are examining this  research simply to figure out what damage freezing (in a regular freezer) lactobacilli has on the bacterial survival rates.

Here’s what we found

One study[1. Study of the cryotolerance of Lactobacillus acidophilus: Effect of culture and freezing conditions on the viability and cellular protein levels, Leı̈la Bâati, Cathy Fabre-Gea, Daniel Auriol, Philippe J Blanc, International Journal of Food Microbiology (Impact Factor: 3.08).10/2000; 59(3):241-7. DOI: 10.1016/S0168-1605(00)00361-5] showed that slow-cooling and pre-freezing stressors on bacteria make the bacteria more hardy and improve cell resistance and the preservation of their physiological characteristics.

  • In temperature drops from 37 C to -80 C, there was a considerable loss of cell viability
  • Slow temperature drop rates preserved survival rates of 75 per cent
  • Pre-incubation at 22 C over six hours led to cryotolerance – after 24 hours at -80 C, survival was 75 per cent
  • pH also affected cell resistance

What does this mean for us?

Bacteria are very adaptable, so doing things slowly (ish) in terms of freezing allows the bacteria to get used to the idea and bust out their cell resistance. This means we can do lots of things to bacteria and they will survive, but we need to take care to be slow and allow them to adapt.

Freezing any liquid containing lactobacilli in a regular freezer from room temperature therefore is unlikely to cause any major loss of bacteria in the short-term (24 hours).


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Jessica Lloyd - Vulvovaginal Specialist Naturopathic Practitioner, BHSc(N)

Jessica is a degree-qualified naturopath (BHSc) specialising in vulvovaginal health and disease, based in Melbourne, Australia.

Jessica is the owner and lead naturopath of My Vagina, and is a member of the:

  • International Society for the Study of Vulvovaginal Disease (ISSVD)
  • International Society for the Study of Women's Sexual Health (ISSWSH)
  • National Vulvodynia Association (NVA) Australia
  • New Zealand Vulvovaginal Society (ANZVS)
  • Australian Traditional Medicine Society (ATMS)