If your hard cider is hazy, it has colloids. Cider colloids are a mixture of small particles or compounds that are insoluble and evenly suspended within your cider. Colloids are generally compounds made up of carbohydrates, color compounds, or proteins(1). The carbohydrates and color compounds are usually derived from the fruit. The proteins are usually derived from yeast, especially if autolysis is allowed. There are three main types of colloids found in wine and we can assume these are also common in cider. Just like grapes, the amount of each type will depend on the apple varieties used. Let’s explore the three main types of colloidal compounds, which include the following(1).
- Coloring Compounds
Colloid carbohydrates are also known as protective colloids and there are generally two categories: acidic and neutral polysaccharides. Acidic polysaccharides include pectin, pectic acid, and protopectins. Pectin is soluble in water but not alcohol and is the most prevalent of the three. Pectin’s insoluble nature in alcohol is why perry and some ciders will often form gelatinous masses. As ethanol is generated, it pushes the pectin out of solution. The pectin is attracted to itself, which can create large masses. This is part of the keeving process. Temperature and pH can impact this process. You can test for the amount of pectin in fruit by mixing a teaspoon of fresh juice with two teaspoons of Isopropyl alcohol, often called rubbing alcohol. If you have high pectin fruit, you should see the gelatinous masses form. Some apples and many pears are high in pectin, which can contribute to haze. Fermentation can release enzymes that breakdown pectin and help remove it but you can also support this process by adding pectic enzyme. These processes help remove the pectin particle that when suspended in solution become colloid haze. Neutral polysaccharides are composed of simple sugar molecules. They usually originate from fungal infections like Botryis cinerea (gray mold), which is common in wine. The most common compound is B-glucan. While apples can have fungal infections, its doesn’t appear to be as prevalent as what you find in grapes. One of the potential issues found in cider is ropiness (i.e. high viscosity). This can be the result of lactic acid bacteria binding polysaccharides and glucose or a fungus that converts malic to lactic acid that secretes a viscous polysaccharide.
The most common coloring compounds producing colloids in wine and cider are anthocyans and flavanols. They are called coloring compounds because they create the red and yellow colors of fruit. They are highly reactive to proteins and other compounds They also form tannins, which are condensed or polymerized phenolics. Basically, this is where multiple phenolics bind together. A good example is how anthocyains will form proanthocyains These tannins are more readily created during aging. Basically, phenolic compounds like anthocyans and catechins combine or condense forming bulkier structures. As they continue to polymerize, they become bulkier and less likely to react with other compounds like proteins. They can also precipitate out. This can help create stability of color. As the tannins are formed and they become more condensed, they are less likely to flocculate and create colloidal compounds. This is part of the complex reactions occurring during the aging of cider. Compounds like anthocyans are less stable while flavanols are more stable(1).
Proteins are amino acids that are chained together. They are positively charged at low pH and attract negatively charged compounds. They will flocculate and form colloids. The proteins released during fermentation often combine with polyphenols and precipitate out. These are not very stable. However, proteins released from autolysis, especially mannoproteins, are more stable and less likely to form colloidal compounds. Temperature plays a big part in the formation of colloids. They can actually form colloidal compounds at one temperature and then clarify at another. A great example is chill haze where a cider can become hazy when cold but clear at room temperature.
As you can see, there are a number of compounds that can impact how clear your cider might be. While carbohydrates, phenolic compounds, and proteins are some of the main contributors, the results are not straightforward. Polymerization, temperature, and types of compound can all impact whether colloidal compounds are formed or not.
(1) J. Moreno and R. Peinado, Enological Chemistry, Chapter 19 – Wine Colloids, 323-354, 2912
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