Bad Espresso - what went wrong?

[Bafa]

There is a coffer shop on my way to work that makes the yummiest espressos i have ever had. The last two days a new girl was working the late afternoon when i stopped on my way home. The espressos she made me were gawd awful! I have no p robalem with a little sediment at the bottom of the cup, but hers even floated at the top in the weak crema. The crema lasted maybe 30-50 seconds tops, then it was just a black cup of liquid. It tatsed a litle burnt, and thin like too much water or something. Also it gave me the feeling that it was made with grounds that had been wet before the pull.

Thos two cups were undrinkable. Lord knows I tried to choke em down, but they were not the glowing yummy taste I am used to from this shop. I stopped by this morning and we discussed what could have been wrong and they blame it on the humidity and grinder problems, but I got the vibe from both of the girls that it was the fault of the new girl that made my espresso. They made me a cup and it was apparent the grinder and everything else was fine because it was another great espresso from the people who usually make them.

So basiclly I am curious, what could have made those two cups so awful? I ask simply for the trouble shooting knowledge should I ever defile my beans at home the way she did at the shop. Plus I enjoy "coffee talk" and if there is any knowledge I could impart to a new barista I would certainly offer it up.

 

[cafemakers]

Sounds like a classic case of over-extraction, probably (but not necessarily) caused by grinding at a particle size too fine for conditions or by using too little coffee in the portafilter basket.

The information that you received is correct. Throughout the day, atmospheric changes (temperature, humidity) and the replacement of fresh coffee in a grinder hopper requires a barista to adjust his or her grinder, normally no less than 5 times daily. It is possible that some of these variables changed without the barista noticing (or perhaps the 'new girl' was just learning at your expense).

The bitterness is caused when too many of the chemicals in coffee are drawn out by the water, mainly quinic acid - that same stuff that gives quinine its characteristic bitter flavor. Grinding too fine for a matched variable set of temperature, extraction time, coffee volume and water volume opens up too much surface area of the coffee, thus causing excessive transfer of the coffee into your cup as the water passes by.

You can replicate the same conditions by manipulating the other variables in this equation; for example, by reducing the volume of coffee used (with an ideal particle grind size) or by increasing the time of the extraction (by packing down the coffee with too much pressure so that the water is slowed) or by increasing the volume of water. Increasing the temperature of the extraction has a similar effect by speeding the rate of the chemical reaction.

It was good that you went back to tell them about the problem so that they may correct the issue; most consumers are not so kind.

 

[cafemakers]

Incidentally, I'd also like to point out that these same variables exist outside of espresso extraction. For example, look at the model again when considering simple brewed coffees: larger particle size, similar water temperature, larger water volume, greater volume of coffee, much longer extraction time. You can apply it to whatever method of extraction you prefer and it's just about always the same - the goal is to grab the "right" chemicals out of coffee and leave behind the stuff that we don't want to taste.

 

[Bafa]

Great explaination! Thanks. I did know that humidity has an effect on what size grind you should use, but i had no idea it meant that much.

Also I "thought" I noticed several mistakes she made when making it. Her tamping was almost non existant. Barely did the 5 lbs for the first tamp and then that was it... no packing the coffee. But as I said I couldnt really see that well, so i couldnt really say much. Then i noticed she was doing probably 10 second pull if that, but ending up with much more volume of coffee than I usually get. So then i was doubting my timing, because of the volume she got. But the not tamping correctly would explain that.

Last was the proof in the cup. Even after I pour the coffee out on the ground there was enough fine powder sediment at the bottom of my cup to completely cake and cover the corner of half my cup.

Yes as embarressing as it was to go to them and say that the last two cups I had were undrinkable was a little embarressing, but worth it to me if they can correct the problem and get me a good espresso.

Thanks again for the reply.

 

[cafemakers]

Over-extraction can sometimes be confused for under-extraction; the opposite problem.

The scenario that you have described (quick extraction following a weak tamp) makes me think that the coffee was in contact with the water for too short a time, not bringing some of the critical flavor chemicals to the cup. Are you certain that the coffee was bitter and not sour instead?

It is still possible that the problem was a result of over-extraction (this is the confusing part): if far too little ground coffee was used in the portafilter basket, even a 10 second shot may be over-extracted.

 

[CafeBlue]

Bafa;
From your description, you noticed several things the new staffer did completely incorrectly. She could use better training and better supervision, or else she ignored her better training and should be reprimanded or dismissed. Please approach the cafe' management/owner as you did the morning crew. At least forward a link to this forum's posting. It sounds like the morning crew has better practices, so at least some of the skills and knowledge base is available. You and your cafe will benefit from best practices.
The shot was too fast, the shot was under-extracted. Andrew is right, under-extraction usually results in sour taste. The coffee most likely also channeled in the portafilter, due to the light tamp - this means the overall under-extracted brew is compounded by over-extraction at the high water flow channels, so it is also bitter. She likely under-dosed as well as under-tamped - then the "puck" of spent coffee would come out of the portafilter soggy/wet/loose. She also may have adjusted the grinder setting way too fine in compensation for her other poor practices, yielding fines and sludge in the cup. It is also likely that the spouts of the portafilter dragged in spilled grinds and transferred the loose grinds to your espresso.
You can learn more from the WBC, training videos, workshops and classes, coffee roasters, espresso equipment dealers, or on-site training/consultants.

 

[La Crema Coffee]

The grounds in the bottom: Maybe she packed her portafilter on a surface that had grounds on it: And the spouts transfered them onto you espresso.

 

[Bafa]

It seems they have worked with this girl as I have given her yet another chance. She still isnt as good as the other ladies that make my espresso, but a great improvement and still an enjoyable cup. Also the shop got a new shipment of beans in, the whole store is stuffed with bags stacked high. Great coffee too! They sell the beans unroasted so I think I will try my hand at roasting some to see what I get.