Fermenting Frozen Seeds
Can you freeze cacao seeds to ferment later?
When talking story with other tiny batch cacao fermenters, I am regularly asked if cacao seeds can be harvested from the pod then frozen to ferment later. Usually the reason they would like to do this is they don’t have enough pods for a full, even if tiny, fermentation. They may freeze a couple pods’ worth one month, two pods the next month, and a month later thaw to combine with a half dozen fresh pods for a fermentation. Can you ferment frozen beans? Sure, people do this. Does it yield good results? That’s a better question.
Having never tried fermenting frozen seeds myself, my answer had been: “I’m not sure, if you try this please let me know how it turns out.” I have heard back from several people who regularly ferment previously frozen seeds and have liked the outcome. A few months ago, I finally remembered to freeze some seeds to try it myself. I fermented a mixed batch of frozen and fresh seeds side by side with an all-fresh batch. In retrospect, I might have designed this experiment better, but this experiment is a start.
My hesitation to advise people that freezing seeds before fermentation is completely fine is less due to any concern about the ferment itself, but a concern that the enzymes in the seeds will be damaged and unable to perform their tasks. As a reminder, cacao fermentations have two main aspects. One is the direct result of fermentation: Microbes ferment the fruit, which results in acids and other molecules diffusing into the seeds and alkaloids and other molecules diffusing out of the seeds. The other is indirect. When the fermentation reaches a high enough temperature, the enzymes present in the seeds are activated to cause molecular changes that lead to flavors we recognize as chocolatey.
Freezing the pulp shouldn’t damage the sugars, the fuel for fermentation. Some microbes may not survive freezing, but mixing in fresh seeds, or inoculating some other way, should take care of potential microbe deficiencies. The enzymes in the seed are more of a concern. Can they survive being frozen?
I still don’t know the answer to how freezing seeds affects the seeds’ enzymes, but here are the results of my first experiment to address this question. Spoiler alert - the experiment below suggests that the frozen+fresh batch fermented at least as well as the all-fresh batch. However, the flavor of the all-fresh ferment had a deeper chocolatey flavor. More experimentation is crucial to know whether this is a reliable result or a fluke.
I began by freezing the fruit and seeds of four pods. I opened the pods and scooped out the fruit and seeds. I weighed the mass and put it in a freezer-safe, plastic ziplock bag, making sure to squeeze out the air before putting it in the freezer.
A couple of months later, I thawed the frozen beans and mixed them with fresh beans. A second jar of just fresh beans was used as a control. These two batches were taken through the steps of fermentation and drying in parallel.
(A huge caveat is that the even the exact same batch of seeds divided into jars to undergo the same fermentation conditions can be different. I’ve done that experiment. It’s a disappointing result if you want to have definite answers, but not too surprising given the huge number of variables in fermentation. Small difference and random chance can affect the outcome. Understanding that this simple trial cannot be definitive, curiosity about frozen seeds made me want to try anyway.)
I fermented the two batches in separate Mason jars using the heated water bottles in a cooler method, as detailed in my book. The seeds fermented for about 8 days. The ferments didn’t look or smell too different, but a few cut tests suggested that, if anything, the frozen+fresh batch was fermenting better. The seeds had more brown acidic liquid (I like to call “gravy,” and the cotyledons had more grooves. After fermentation, I dried the beans for about a week. The dried beans looked and smelled similar.
After roasting and winnowing the beans and detecting no huge difference, I prepared a sample for a taste test by grinding an assortment of beans and dissolving in hot water. This is a method often used to ascertain the quality of cocoa. Grinding many beans together is more accurate than tasting a few individually, and water is a good medium for cocoa flavor to come through.
I ground the samples in an electric spice grinder and molded into tablets. I grated the same amount of each and added the same amount of hot water. After stirring to dissolve, I taste tested them multiple times as the water cooled. They were both sour and toasty with a similar flavor, not my best tasting cocoa beans ever. I was honestly surprised to detect more of a deep chocolate note in the all-fresh version. While I know it is important to keep an open mind, I was expecting no detectable difference in flavor or perhaps that the frozen+fresh ferment would taste more fermented since the signs of fermentation were stronger. But here it was: the result I would expect if the enzymes in the seeds were not properly working for whatever reason.
This experiment is admittedly poor evidence one way or the other. It’s just a toe dipped in the water. But this experience will slightly change my advice to people asking about freezing cacao before fermentation. I will ask for more information about their intention and desired outcome. For some, this type fermentation may be perfect, while others may not achieve the results they want. Certainly freezing the beans will affect the final flavor of the chocolate, just like ripeness at harvest, temperature and length of fermentation, and just about everything else. What will not change is my recommendation to try it to find out if they like the result. And to let me know, too.
Have you used fermented cacao seeds? Let me know in the comments!
Thanks for this experiment. It seems promising, and agree more testing is necessary. Bravo.
I've spent last weeks with these questions. Such a good reading at this moment. Can't wait to test it. I'm freezing some pulp today. Thank you for always sharing, Hanna!
Lets go! hu hu