Fining agents are more than just compounds added to help clarify your cider. They can also remove other compounds, usually with the goal of improving stability. However, these agents can impact color and aroma. As defined by R. Marchal and E.J. Waters in the book Managing Wine Quality(1), fining is the addition of a substance that reacts or absorbs undesirable compounds. They go on to define six grouping of fining agents. These six groupings are based on where they are derived.
- Earths: Montmorillonite, Bentonite, Kaolinite
- Animal Proteins: Gelatin (pork, cow, fish), Isinglass (fish), Caseins
- Plant Proteins: Wheat Gluten, Soy, Lupine, Pea
- Wood Charcoal (Carbons)
- Synthetic Polymers: Polyvinylpolypyrrolidone (PVPP)
- Silicon Dioxide: Kieselsol
The most commonly used fining agent in wine is bentonite. For hard cider, the most common agent is usually pectinase (pectic enzyme). Apples and especially pears, can have large amounts of pectin and this pectin is often the cause for post fermentation haze. When ciders are hazy, it is more common for the haze to be from pectin versus protein. While pectin has a negative charge and could be removed by some fining agents post-fermentation, it is usually easier to deal with it pre-fermentation through an enzymatic reaction. Unlike many fining agents that work based on a molecular charge, pectinase is an enzyme so it only reacts with pectin and not other compounds, which again makes it the preferred method. However, there are a wide range of available agents that can be used to clarify and extract various undesirable compounds. You have to be careful because they sometimes extract desirable ones too. I’ve created a summary table that highlights some of the key characteristics of common fining agents. Let’s explore these characteristics in more detail.
| Fining Compound | Charge | Application | Target | Risk |
| Pectinase | Enzyme | Pre Fermentation | Pectin Haze | Can Produce Methanol |
| Bentonite | Negative | Pre & Post Fermentation | Protein Haze | Can Strip Polyphenols |
| Casein | Positive | Pre & Post Fermentation | Suspended Solids, Odors, Color | Derived from Cow Milk |
| Chitosan | Positive | Post Fermentation | Protein, Yeast, Polyphenols | Potential Shellfish Allergies |
| Gelatin | Positive | Post Fermentation | Tannins (Bitterness), Protein | Can Create Haze |
| Isinglass | Positive | Post Fermentation | Polyphenols, Colloidal Haze, Oxidation | Final Polish Only |
| Kieselsol | Negative | Post Fermentation | Peptides, Tannins | Excessive Fining |
| PVPP | Absorbent | Post Fermentation | Polyphenols & Oxidized Compounds | Removes Resveratrol |
| Sparkalloid | Positive | Post Fermentation | Tannin Haze | Long Settling Time |
Fining Compounds:
As noted by Marchal and Waters(1), fining agents often come from many different sources including animals, plants, fish, and even synthetic processes. The only agent that would naturally be present in cider is pectinase. Yeast and bacteria can release pectinase naturally during the fermentation process. The problem is that it may not be enough, so adding enzymes will help ensure all the pectin is cleaved so haze is prevented. Pectinase is an enzymatic reaction, so the compound it affects is very specific. Most fining agents are not as exact and will remove various compounds. This is because they work based on their molecular charge.
Charge
Bentonite and kieselsol are negatively charged while chitosan, gelatin, isinglass, and sparkalloid are positively charged compounds. Charges are typically the result of the electron structure found in the compound. Just like magnetic fields, opposite molecular charges are drawn to each other or will flocculate together. Like charges will repulse each other. Temperature and ethanol levels can impact the charge of a compound. However, the pH of the cider is the biggest factor in determining whether a compound is positively or negatively charged. This is especially true with proteins. The isoelectric point (pI) is the pH level where a compound switches back and forth from having a negative charge to a positive charge. For example, gelatin will normally have a pI between a pH of 5 and 9 so in cider, it will have a negative charge. If the type of gelatin used has a high pI, like 8, it will have a greater charge in cider with a pH of 3.3 than a type of gelatin with a pI of 5. The greater the charge the more attractive it will be for oppositely charged compounds. This is how most fining agents work, they attract oppositely charged particles.
Application
Most fining agents are applied post-fermentation to remove particles that are suspended in the cider. These colloidal compounds are what create haze. This is commonly pectin in cider but can be proteins and yeast that remain suspended. However, fining agents can be used to remove particles pre-fermentation. Pectic enzyme is inhibited by the presence of ethanol, so it is more effective to apply it pre-fermentation. Bentonite can also be applied pre-fermentation. The benefits of pre-fermentation application is that the agents can help remove other solids and clarify the juice. Clearer juice reduces sulfur odors and promotes fruit aromas. It can also reduce the assimilable nitrogen, which can impact the fermentation rate. Applying pre-fermentation can also help reduce loss of higher value product in the lees, and is less likely to reduce fermentative compounds, which. Are those created during fermentation. If these compounds are positive, that is good. If your goal isn’t just clarification but removal of undesirable compounds, you will have to apply the fining agent post-fermentation.
Target
Each agent has a type of compound that they tend to be better at removing. However, because most work using a charge, they will remove other compounds. If you apply a positively charged fining agent, it can remove any negatively charged compound. The stronger the attraction, difference in charge levels, the more likely the fining agent will attach to that compounds. As these clumps of compounds grow, they get heavy and sink to the bottom forming lees. This means fewer suspended particles and less turbidity (haze).
Risk
Besides removing desired compounds, fining agents can pose other risks. For example, certain pectic enzymes can create methanol. While not a concern for cider, it can be a concern for those distilling or making spirits. Other risks include the potential to actually create more haze or removing too many compounds or healthful compounds like resveratrol. Lastly, there are also concerns about agents that are animal based given recent outbreaks in mad cow disease and even the concern of gluten and fish allergies.
(1) R. Marchal and E. J. Waters, Managing Wine Quality: Winemaking Technologies and Wine Quality, Chapter 7, New directions in stabilization, clarification and fining of white wines, Woodhead Publishing Limited, 2010
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