Should Espresso Portafilters Be Locked Back to Group Head or Left at Room Temperature? The Impact of Temperature on Coffee Flavor

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Introduction

"After extracting espresso, should the portafilter be locked onto the group head to keep warm or should it be placed at room temperature?" Coffee baristas have different views on this question. Some baristas believe that locking the portafilter onto the group head can maintain the entire portafilter (including the filter basket) at the same temperature, reducing the impact of temperature differences on coffee flavor; others believe that locking it on the group head can easily cause the entire portafilter to be at high temperature, and high temperature will affect the coffee's flavor.

Comparative Experiment

FrontStreet Coffee this time used three groups of portafilters at different temperatures for extraction to see what impact the portafilter temperature has on espresso flavor.

For this experiment, FrontStreet Coffee used Sunflower Warm Sunshine Blend coffee beans, which are a blend of Sherry coffee beans and Yirgacheffe Red Cherry coffee beans in a 7:3 ratio. Extraction parameters were: Faema E78 espresso machine, Faema 900N grinder, grind size 1.9, double portafilter, 20g coffee grounds, extracted 35g coffee (double espresso), extraction time 25 seconds.

Group A Experiment

Coffee extraction was performed when the entire portafilter (including filter basket) temperature was 26°C, and the extracted espresso temperature was 63.2°C.

Group A espresso flavor characteristics: whiskey aroma, milk chocolate, vanilla cream, gentle acidity, caramel-like aftertaste, prominent aroma, rich mouthfeel.

Group B Experiment

The room temperature portafilter was locked onto the group head and flushed with water for 5 seconds for preheating, at which point the entire portafilter temperature was 56°C. After a series of operations including dosing, distribution, and tamping, the entire portafilter temperature dropped to 50°C, and the extracted espresso temperature was 64.1°C.

Group B espresso flavor characteristics: liquor-filled chocolate, vanilla, caramel-like aftertaste, less pronounced acidity and aroma than Group A, but prominent nutty flavor.

Group C Experiment

The room temperature portafilter was locked onto the group head for 15 minutes, and the entire portafilter temperature reached 74°C. After a series of operations including dosing, distribution, and tamping, the entire portafilter temperature dropped to 69°C, and the extracted espresso temperature was 64.8°C.

The espresso extracted in this group experiment showed these flavor characteristics: dark chocolate, nuts, smoky sensation, fruit aroma and acidity not obvious, slightly burnt taste, insufficient aroma.

Experimental Results

Through comparison of the three experimental groups, we can see that the espresso extracted using a room temperature portafilter has the most balanced flavor; the espresso extracted using a preheated portafilter has more prominent nutty flavor, but slightly insufficient aroma; the espresso extracted using a high temperature portafilter has insufficient aroma and has a smoky sensation as well as a burnt taste. At the same time, we can notice that regardless of the portafilter's temperature, the temperature difference of the extracted espresso among the three experimental groups is not significant. FrontStreet Coffee believes that rather than the portafilter temperature affecting the coffee's flavor, it's more accurate to say that the filter basket temperature affects the coffee's flavor.

After preheating treatment, Group B's coffee filter basket temperature will be in a semi-high temperature state. When coffee grounds fall into the filter basket, the temperature will accelerate the volatilization speed of lightweight molecular flavor compounds (such as fruit acids, floral aromas). When the acidic and aromatic flavors weaken, medium molecular weight flavor compounds will become more prominent (such as nuts, chocolate). This explains why Group B's acidic and aromatic flavors are not as prominent as Group A's, but can better reflect nutty flavors.

Group C follows the same principle as Group B. Because the filter basket is in a high temperature state, both lightweight and medium molecular weight flavor compounds are accelerated in volatilization, at which time heavy molecular weight flavor compounds will appear (such as smoky, burnt bitterness).

FrontStreet Coffee does not recommend keeping the portafilter locked onto the group head for extended periods to maintain temperature. When extracting coffee, you can choose a room temperature portafilter or quickly preheat the portafilter based on the flavors you wish to express.

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