Roasting conditions & polyphenol levels in cocoa beans.

Image credit: Geoseph Domenichiello.  Depicts Raaka Chocolate (raw bean to bar) vs Sirene Chocolate (roasted bean to bar).  

Żyżelewicz, Dorota, Krysiak, W., Oracz, J., Sosnowska, D., Budryn, G. & Nebesny, E., The influence of the roasting process conditions on the polyphenol content in cocoa beans, nibs, and chocolates, Food Research International (2016), doi: 10.1016/j.foodres.2016.03.026

This experiment looked at how roasting affects the levels of polyphenols (antioxidants) in cocoa beans. Roasting cocoa beans, just as cooking in general, will diminish some nutritional elements, including antioxidants. However, cooking will also sometimes improve them, as in the case of cooking tomatoes where vitamin c levels will diminish, but lycopene (an antioxidant) will increase. Nevertheless, unroasted cacao beans do contain much higher levels of total antioxidants than roasted cacao, which has lead to a raw chocolate movement in North America. This movement for the most part stands by the idea that raw chocolate is healthier because of the higher levels of antioxidants.

Why is cacao roasted anyway? Unroasted cocoa beans don’t taste much like chocolate. Roasting allows for the development of favorable aroma molecules to form within the cocoa bean. These favorable aromas include the classic cocoa flavour we associate with chocolate. If the cacao is also of a high quality variety, other aromas (such as berry, butter, and nutty) will also develop within the cocoa bean. All these aromas form in the presence of heat above 130*C. None of these aromas be possible if the cacao beans are not properly roasted. Roasting also kills microorganisms that may be living outside the cocoa bean, originating where the seeds were fermented, dried, and stored.

What does this mean for raw chocolate? Because cocoa beans used to produce raw chocolate are not heated above 42*C (this differs according to the manufacturer), the typical cocoa flavour aromas do not get a chance to form. The result is a chocolate that is much more “wild” in flavour, and unlike what you would expect from traditional chocolate. Many enjoy this flavour, while others find it off putting. Because of the lack of flavour development compared to roasted chocolate, raw chocolate makers most often add other flavourful ingredients to widen the range of flavours in their raw chocolate, as well as tame the more wild aromas some find difficult to get used to. Some voice concern over the idea that the raw cocoa beans may contain harmful microorganisms that are not killed off due to not being roasted at a high enough temperature. I have come across claims of people falling ill when in contact with unroasted cacao, but there is also a thriving raw chocolate industry that appears to be doing well, and people consuming raw chocolate without falling ill.

Zyzeleicz et al. compared the antioxidant levels of raw cocoa beans, roasted cocoa beans, and roasted cocoa nibs. They also looked at how different roasting variables contributed to polyphenol degradation. These variables included roasting temperatures (135 vs 150*C), time (from 15 min to 60+), air flow velocity (0.5 vs 1 m/s), and humidity (0.3 vs 5% RH). They focused mostly on the polyphenols catechin, epicatechin, and procyanidins, which make up the bulk of the antioxidants in chocolate and cacao. The largest group of polyphenols in raw cocoa are flavanols (flavan-3-ol catechin and favan-3,4-diols - leucoanthocyanins). These constitute 60% of the total polyphenol content. It has been reported that the richest in phenolic compounds are Forastero cocoa beans. Up until now, most researchers analyzed the effects of roasting in general, but did not look at the effect of specific variables of roasting.

So is raw chocolate really packed with more antioxidants? This study looked more at the effects of roasting on the cocoa beans themselves, not comparing raw and roasted chocolate per se. The raw cocoa beans they analyzed contained a total of 484.54 mg (±14.77) of polyphenols per 100g. Roasted cocoa beans contained a range of total polyphenol content, due to duration of roasting time, as well as relative humidity and air flow velocity. For instance, at 15 minutes of roasting, some batches of cocoa beans contained anywhere from 197 mg to 467 mg of polyphenols per 100g. At 35 minutes of roasting, these numbers dropped to 162 mg to 224 mg. At 50 minutes or greater, levels ranged from 164 mg to 220 mg. Roasting didn’t totally diminish total polyphenol content in all the samples, but most samples contained polyphenol levels half or less than half the amount found in raw cocoa beans. Below is a table from the research paper that includes the levels of polyphenols at various temperatures, humidity levels, and air velocity within the convection oven.

Figure 1: Table 3 from Zyzelewicz et al. (2018) Depicting the flavanol content of catechin, epicatechin, and procyanidin levels at various treatments of cocoa beans.

This was one experiment, using cacao beans originating in Togo, and were said to be of the Forastero variety. Measuring phenolic compounds, and using them as a standard for all cocoa beans isn’t advised. The content of phenolic compounds vary according to variety (genes), region of cultivation, and the curing process (how they were fermented and dried). The authors stated that processes such as fermentation, drying, alkalization, and roasting all contribute to the degradation of phenolic compounds. Therefore, all chocolate makers have different techniques and times for roasting, use cacao beans that may be fermented and dried differently, and so the levels of polyphenols in their cacao beans may vary greatly.

What were some of the findings according to the different variables? The greatest finding for both whole roasted cocoa beans and roasted cocoa nibs, was that “humid air” (at 5% relative humidity) appeared to slow down the degradation of polyphenols. It appears to have a protective action that preserves the phenolic content in the presence of heat.

Figure 2. Table is from USDA Database Flavanol Content (2014)

https://www.ars.usda.gov/ARSUserFiles/80400525/Data/Flav/Flav_R03-1.pdf

Let’s compare to other foods that contain high amounts of polyphenols. The USDA Database on flavanol content lists many foods and their levels of specific polyphenols. The polyphenols we are concerned with here, especially in regards to chocolate, are flavanols (catechins, epicatechins, and procyanidins. You can click on the link or copy and paste it into your browser to check out the database yourself.

According to this 2014 publications by the USDA, blueberries contain about 6.69 mg of flavanols per 100g. Blueberries are considered a food with moderate to high levels of antioxidants. In contrast, the raw cocoa beans above contain close to 500 mg of flavanols per 100g. Roasted cocoa beans contained on average just under 200 mg to close to 400 mg depending on time and other variables as seen in figure one above. The USDA lists dark chocolate as containing 108.6 mg of flavanols, and milk chocolate containing 15.04 mg per 100g. Brewed green tea contains 132.8 mg of flavanols per 100g.

What can you take from these numbers? Yes, raw unroasted cocoa beans contain very high levels of flavanols. However, roasted cocoa beans as well as dark chocolate contain the same if not more flavanols than a cup of green tea, or 100 g of blueberries. Moderation is key. As well, chocolate is a calorie dense food, containing a high amount of fat, and is to be eaten in moderation.

Antioxidants are a controversial topic, and how much one needs in order to live a healthy life still debated. Maximizing on your antioxidant intake as a priority when it comes to chocolate is one way to live, but not the only way. Chocolate is also enjoyed for its flavourful aromas, fine smooth texture, and comfort we feel when we bite into a delicious bar. Enjoying raw chocolate for its unique wild flavours and aromas, its texture, and the range of flavourful combinations makers come up with seems to be a more reasonable reason to consume it. Put flavour first, be informed about the benefits, and then enjoy chocolate based on your level of satisfaction!

The front image of this article depicts two bars, Raaka Chocolate (raw) on the left, and Sirine Chocolate (roasted) on the right. Both delicious on their own right, but very different as far as how they were processed, and final flavour notes. Try them for yourself, juxtapose them as you taste, and come to your own conclusions about the flavour and total satisfaction. Decide for yourself if you’d like to add raw, roasted, or both chocolates to your chocolate eating habits.