Wickerhamomyces anomalus

Wickerhamomyces anomalus is the current name for a yeast widely reported in older food literature as Pichia anomala or Hansenula anomala. Candida pelliculosa has also been used for an asexual form.

The species occurs in fermented foods, brines, grain, dairy and meat environments and can tolerate conditions that allow film formation at oxygen-exposed surfaces.

Selected strains can produce volatile aroma compounds or killer toxins active against susceptible yeasts and moulds, which has led to research on ripening and bioprotection.

Those properties are strain-specific. Other isolates can form unwanted films, gas or off-flavours, and the species has also been reported as an opportunistic organism.

Deliberate use therefore requires a characterised food-grade strain and product evidence. A film previously called Hansenula should not be encouraged or identified from appearance alone.