Fermenting on Bentonite

Last updated: 6/2023

Applies to: Winemakers making tank fermented whites and rosésthat 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 include:

  • Early removal of heat unstable proteins (solubility of proteins decrease as alcohol increases)
  • May eliminate some post-fermentation processes
  • Better preservation of aromatics than post-fermentation additions*
  • May stimulate fermentation by increasing surface area for the yeast
  • 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™ or GO-FERM STEROL FLASH™ 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


How much bentonite should be used?

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 Laboratories. 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/hL16.7-25lb/1000 gal

At what stage of fermentation should bentonite be added?

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 (Horvat et al., 2019). 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)

Case Study


During harvest 2021, Scott Laboratories collaborated with a Sonoma County winery to investigate how the timing of FERMOBENT PORE-TEC addition during fermentation affected heat (protein) stability. The trial was inspired by and modeled after a 2019 study published in Food Chemistry which found adding bentonite mid-to-late fermentation removes protein more effectively than adding it in the juice phase or early fermentation (Horvat et al., 2019). The trial was conducted on a lot of Sauvignon blanc that typically requires large post-fermentation bentonite additions to achieve heat stability.

Trial Setup:

Four treatments were performed: the control was fermented without bentonite and the other treatments received a FERMOBENT addition at either the beginning, middle, or end of fermentation. All bentonite additions were made at a rate of 12 lb/1000 gal*. Heat stability trials were conducted at the winery immediately following fermentation.

*The bentonite dose was chosen based on this lot’s average post-fermentation bentonite requirements over previous vintages.


The wine that received the FERMOBENT dose in the middle of fermentation was heat stable** following fermentation. This wine required no further bentonite treatments. The control, the “beginning,” and the “end” treatments were not heat stable after completing fermentation.

** The definition of “heat stability” does not have an industry-standard consensus. Scott Laboratories and the Institut Oenologique de Champagne (IOC) define heat stability as a <1.5 NTU difference between room temperature turbidity and post-heat treatment turbidity.

What We Learned:

We learned that adding FERMOBENT at any time during fermentation produces a more protein stable wine than if FERMOBENT is not added. Additionally, in this trial, adding FERMOBENT mid-fermentation yielded a protein stable wine immediately following fermentation.

Learn More

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.