When someone says bacteria, we generally have a negative reaction. Bacteria is a bad thing, right? We want to kill it to keep us from getting sick. However, not all bacteria is bad and especially when you are fermenting hard cider. Lactic Acid Bacteria, commonly called LAB, is the under-appreciated and often abused element in the creation of good hard cider. It is part of the microflora of your juice and cider. It is why you can have malolactic fermentation (MLF) but more importantly, it is a key element of positive maturation such as when you age your cider on the lees. Bacteria can also prevent some reactions you don’t want. Therefore, why is it common for people to kill and suppress it. Let’s explore the types of bacteria found in the hard cider making process.
When you press apples into juice, your juice naturally has bacteria. Guess what, when you eat a fresh whole apple, your apple has bacteria. You can’t really get away from bacteria. Like yeast, it literally lives all around us. F. Cousins and associates found that bacteria is naturally found in all aspects of the apple, which is highlighted in the below table(1).
Some of these these families contribute positively to the hard cider making process. Lactobacillaceae or LAB is the main bacteria supporting MLF. It also has very positive contributions to maturation in the aging process. Acetobacteraceae on the other hand wants to finish the fermentation process and convert your hard cider to vinegar. This is great for preserving vegetables or making salad dressing but not great if you want hard cider. Let’s explore these families of bacteria in more detail.
Acetobacteraceae: Also commonly referred to as acetobacter, is a bacteria that converts ethanol into acetic acid, i.e. vinegar. This is an aerobic process meaning it needs oxygen, which is why cider makers are instructed to avoid oxygen exposure of their cider after fermentation completes. Preservatives like potassium sulfite can be added to help suppress acetobacter bacteria but the most common and effective method is simply to limit oxygen exposure after fermentation completes.
Enterobacteriaceae: Often referred to as Enterocabter, it is commonly found in animal gut microflora and soils but not commonly found in human gut microflora. This is a vast family of bacteria and contains some of the human pathogens salmonella and escherichia coli. As I have written about previously in my post on sulfites and sorbates, this bacteria, including the human pathogens, can’t live within hard cider. That is why you naturally see it disappear once juice is fermented. This is why you want to wash your fruit and use healthy fruit if you are eating or drinking it fresh. This bacteria doesn’t really impact the hard cider process but it’s good to understand it’s there.
Lactobacillaceae: You will see these bacteria referred to as Lactobacillus, Lactic Acid Bacteria, or LAB. You find these throughout the process of hard cider making. It’s on the flower, the fruit, and in the cider. It enables the conversion of malic acid to lactic acid during MLF. It also creates many chemical reactions during maturation. Some of these may create undesirable flavors and aromas but many are positive reactions. The results is many compounds that together can form complex aromas and flavors.
Leuconostocaceae: This is a type of lactic acid bacteria but unlike the other families in LAB genus, it has the ability to ferment hexos. They are non-pathogenic and while they are more often found in milk and milk-based products, they can be found in hard cider as well. This family produces lactic acid but also the biogenic amine, Putrescine, which can create the aroma of putrefying flesh(1). While that doesn’t sound appetizing, remember that the aroma complexity of hard cider is quite high and small amount of various compound can create aromas and flavors that are quite enjoyable.
Sphingomonadaceae: There are over 18 types of bacteria in the Sphingomonadaceae family. These are not considered harmful to humans or plants. One of the genera, Zymomonas mobilis, is actually capable of fermenting glucose into ethanol and CO2 more effectively than saccharomyces cerevisiae. It creates a framboise type of cider sickness, especially in sweet hard ciders. It has an aroma of rotten lemon peel or grass, which is caused by acetaldehyde(2). pH below 3.7 helps to prevent this but it is known to be active in a wide range of pH, alcohol, and SO2 level.
Sporolactobacilliaceae: Sporolactobacillus is the most common of this bacteria type. It is known to produce tyramine, a biogenic amines like histamine that can produce headaches and hypertension in large dosages(1). It also contributes to the aroma in smaller dosages.
So, what should you do about all this bacteria and even the microflora in your apple juice and hard cider? The biggest risk is acetobacter. However, this risk is easily managed through limiting oxygenation. Suppressing it through potassium metabisulfite or pasteurization risks killing off all the other bacteria and microflora, especially the extremely beneficial LAB that enables MLF and maturation benefits as well as positive probiotic health benefits. To ensure these benefits, you would need to inoculate your hard cider again with at least various LAB bacteria. This is another example where blindly following the path of wine, may not produce the best tasting or most healthy hard ciders. It’s another argument for not treating your juice prior to fermentation to ensure your natural bacteria microflora is viable and able to provide positive aroma and flavor characteristics.
(1) Fabien J. Cousin and associates, Microorganisms in Fermented Apple Beverages, Microorganisms 2017, 5, 39
(2) M. Coton and associates, LWT 39, 2006, 972–979