Fermenting on Bentonite

Last updated: 7/2021

Applies to: Winemakers making tank fermented whites that need early protein stabilization and preservation of aromatics, especially in high protein varietals or in difficult seasons.


Bentonite can be added to the fermentation vessel of any varietal but is particularly beneficial for tank fermented whites and rosés that need protein stabilization. More specifically, high-protein cultivars like Sauvignon blanc and Gewürztraminer, and other early-to-bottle white and rosé wines benefit most from this practice. Early protein stabilization allows for the preservation of aromatics, minimizes racking steps, and saves time when compared to post-fermentation bentonite additions.

Bentonite can be used at any stage of the winemaking process. However, different types of bentonite should be used based on the winemaking stage and winemaking goals. FERMOBENT® PORE-TEC is our recommended bentonite for use during fermentation because of its exceptional purity, good dispersion, effective protein removal, and formation of a stable deposit.


Benefits of fermentation bentonite additions include:

  • Early removal of heat unstable proteins (solubility of proteins decrease as alcohol increases)
  • Better preservation of aromatics than post-fermentation additions*
  • May stimulate fermentation by increasing surface area for the yeast
  • May eliminate some post-fermentation processes
  • May lower overall levels of bentonite needed (compared to post-fermentation treatment levels)
  • FERMOBENT PORE-TEC compacts well and leads to lower lees volumes than post-fermentation bentonite treatments


Does fermenting on bentonite affect YAN?

Trials at Erbslöh suggest fermenting on bentonite does not diminish yeast assimilable nitrogen (YAN). This is even less of a concern if a proper nutrition strategy is followed. This may include proper yeast rehydration with GO-FERM PROTECT EVOLUTION™ and additions of FERMAID O™ and/or STIMULA™ products during fermentation.

*Are aromatics affected negatively?

No, in most cases aromatics are higher in wines fermented on bentonite when compared to those receiving post-fermentation bentonite treatments (Horvat et al., 2019). Though the reasons for this preservation are not completely understood, it is hypothesized that this is due to bentonite's inhibition of aroma-degrading enzymes.

Can I use my regular bentonite?

No, standard bentonite is not pure enough. Heat and vigor during fermentation can lead to leaching of copper and iron from unpure bentonite which could result in green and brown color taints. It is important to use a consistently clean bentonite, like FERMOBENT PORE-TEC.


What is the best time to add bentonite?

Bentonite may be added at any stage of fermentation; however, studies suggest that adding bentonite mid-to-late fermentation removes protein more effectively than adding in the juice phase or early fermentation. While the reason for this is unclear, it may be because:

  • Earlier additions of bentonite may remove proteins that are less prone to haze formation, wasting the bentonite’s adsorptive properties.
  • Ethanol may open up the bentonite plates, increasing surface area, available binding sites, and potential for adsorption (Horvat et al., 2019).

How much bentonite should I ferment on?

It is always best to determine dose rate by bench trials either with heat & turbidity testing or protein juice analysis with an external lab like ETS. However, if you choose to skip a bench trial, we suggest following the dosing guidelines on the FERMOBENT PORE-TEC product information sheet:

Juice with moderate
protein content
500-1500 ppm50-150 g/hL4.2-12.5 lb/1000 gal
Juice with high protein
content and pH values
2000-3000 ppm200-300 g/hL
16.7-25lb/1000 gal


Bentonite can be used during juice settling or flotation to assist with clarification in pressed white and rosé juice. To increase efficiency, bentonite is best used on juice that has been pre-treated with enzymes to reduce the solids content*. NACALIT® PORE-TEC is our recommended bentonite for pre-fermentation treatment because of its fast flocculation and sedimentation rate and ability to compact lees. Importantly, NACALIT® PORE-TEC does not over-clarify as some solids are needed for fermentation security.

Benefits of pre-fermentation bentonite additions include:

  • Partly eliminate enzymes (tyrosinases, previously known as polyphenol oxidases) therefore offers some protection from oxidation damage
  • Absorbs traces of residual fungicides
  • Removes proteins controlling foaming during fermentation
  • May eliminate some post-fermentation processes
  • Results in cleaner, fruitier wines when used to control solids levels (See: Best practices for Juice Clarification via Settling, Flotation)



For all things bentonite, check out this webinar with our Fining and Stability Product Expert, Maggie McBride. For more information on fermenting on bentonite, watch 29:00 – 39:00.


Horvat, I., Radeka, S., Plavša, T., & Lukić, I. (2019). Bentonite fining during fermentation reduces the dosage required and exhibits significant side-effects on phenols, free and bound aromas, and sensory quality of white wine. Food Chemistry, 285, 305–315.

Erbslöh. (n.d.). Always a clear advantage: bentonite for effective clarification and stabilization. Geisenheim, Germany; Erbslöh.