Évaporation de l'avant vers l'arrière

BH Unlimited Update, Sep 17th 2022.

You know how bakers reckon they get better results and a nicer crust if they have a tray of hot water in the oven as they bake? The reasons why steam is beneficial to baking are manifold, but we only bring this up because when you look into the science of coffee roasting, you begin to realise that it is steam that’s responsible for a lot of the difficulties in managing a roast.

Bakers don’t have any issues with keeping the steam in their ovens, but with coffee roasters, the moisture that comes out of the beans just disappears right up the chimney (with the exception of certain recirculating air roasters like Loring). Then there’s the added complexity of a sudden arrival of steam during première fissure — the probable cause of crashes in bean temp RoR; and then steam's sudden disappearance only seconds later — the probable cause of the ‘ flick of death ’ (a sudden acceleration in the bean RoR).

Just take a look at this data collected by James Davison , a chemical engineer and founder of Williamstown Roasters . These measurements were taken in a drum roaster, and show a distinct spike in moisture evaporation at première fissure.

You’ve got to wonder whether adding some steam-injection capabilities onto a roaster might be a handy means of mitigating flicks. We’re hatching a plan on how to test that ATM — of course we’re expecting Prototype A will involve a steam wand.

So folks, we’ve put together a huge post for you on what happens to moisture during roasting. BH Illimité subscribers who have been working through the Roasting Science online course will already be acquainted with the evaporation front . It’s a topic which has had very little direct study, so we go into plenty of depth there, too.

Science de la torréfaction

Dans notre Science de la torréfaction course this week, we have begun looking at the physical changes that take place in coffee during roasting. Coffee beans lose mass and increase in size as water and carbon dioxide escape, becoming porous and less dense. These changes are essential in making it possible to grind and extract coffee beans.

The amount of mass loss is an important indicator of the degree of roast — and yet how the beans swell and lose mass during the roast depends on the kind of roaster being used, and the roasting conditions. A long, slow roast will never achieve the same mass loss as a fast, hot one, and this makes it very hard to compare results between different roasters. Even the variety of coffee plays a part: the cell wall structures of different varieties seem to break down at different rates.

There’s more than one kind of pore in a coffee bean. Different types of pore play different roles in a coffee bean

In this week’s lessons, we explore these conflicting results, and the role that the changes in the bean’s structure play in the final properties of the coffee, such as how quickly it goes stale, or how easy it is to grind.

BH Illimité les abonnés ont un accès avancé à chaque nouveau lesson au fur et à mesure de la progression du course.

Le guide de l'acheteur de café en Colombie

Dans notre Guide d'achat de la Colombie , we look at two very different regions in the country that have each been recognised with Denominations of Origin (DO).

Santander was probably the site of the very first coffee plants grown in Colombia, but was in many ways a late bloomer. When Norte de Santander was in its heyday, Santander lagged behind and developed a reputation for poor-quality coffee — not helped by the fact that the only route to export was through Venezuela. In the last decade or so, however, Santander’s enterprising producers have overcome challenging growing conditions, and the DO is just one sign of how much things have changed.

The beautiful Camino Real, a pre-colonial road in the heart of Santander

The Sierra Nevada de Santa Marta, in the far north of Colombia, is the only growing region in the country that is not located in the Andes mountains. The Sierra Nevada is a separate mountain range that juts into the Caribbean sea, famed for its unique biodiversity. Culturally and geographically, this region is quite distinct from the other growing regions in the country, and the DO reflects this.

In this week’s lessons, we detail the dramatic changes in Santander’s coffee production over its history. Meanwhile, we explore how coffee growers in the Sierra Nevada de Santa Marta may play an important role in protecting the region’s ecosystem in the future.

Liens rapides

Anyone lucky enough to be coming out to Melbourne for the Melbourne International Coffee Expo, aside from the WBC action, there’s a couple of side hustles going on which you should know about. Sous zéro , the original and still the best frozen coffee pop-up company, have announced an event to be held at Axil Coffee in the Melbourne CBD, for the two days immediately following MICE.

Don’t miss Scott Rao’s Melbourne roasting masterclass on the 1st of October at the St Ali Roastery. We can tell you from past experience visiting these fabulous workshops that Scott’s an early riser — class kicks off at 8am.

Also on the 1st of October, Samo Smrke is giving a talk on Espresso Grinding and Extraction Science at Victoria Arduino Australia, where he promises to present brand new data on — among other things — the role of fines in espresso extraction.

In case you actually are a home baker and wanted to check out a really good bread blogger on the subject of steam, check out this post by Maurizio Leo .

Bols à ventouses de nouveau en stock

Nos bols à ventouses légers bien-aimés sont de retour en stock au Boutique mondiale (Expédition dans le monde entier depuis Hong Kong). Nous proposons également des commandes en carton 40%, idéales pour une torréfaction ou un laboratoire de dégustation à grande échelle nécessitant au moins 192 bols par jour.

Une expérience d'apprentissage sans publicité

Chez BH, nous ne faisons jamais de publicité pour les produits d'autres entreprises sur notre site web. Aucun placement de produit n'est effectué dans nos newsletters, nos newsletters ou nos articles de blog. Nos seuls revenus proviennent de vos abonnements. Lorsque vous voyez des machines ou des équipements à café mentionnés dans nos supports pédagogiques ou présentés dans nos vidéos, nous avons choisi de les utiliser parce que nous aimons les utiliser, parce que nous pensons qu'ils ont une importance historique dans l'évolution de la machine à expresso, ou parce qu'ils vous renseignent sur la culture du café moderne. C'est aussi simple que ça.