When every drop counts: tapping beer cans does not lessen the volume lost upon opening

Référence

Sopina E, Antonescu IE, Hansen T, et al. To beer or not to beer: does tapping beer cans prevent beer loss? A randomised controlled trial. https://arxiv.org/abs/1912.01999.

Sommaire

A common practice is to tap a inadvertently shaken beer can prior to opening it to prevent overflow. The investigators began with 1031 cans of Pilsner-style beer (Carlsberg). The cans were weighed and then randomly assigned to be shaken or unshaken before opening. Within each of these groups they were further randomized to be tapped or untapped before opening (allocation concealment unknown). After refrigerating overnight, the shaken cans were agitated for 2 minutes using the Unimax 2010 shaker at 440 revolutions per minute. Shaken and unshaken cans assigned to tapping were tapped, by hand, 3 times on the recycling label printed on the side of the can to assure consistency. Tapping researchers were masked to whether the can had been shaken. After opening, each beer can was immediately wiped if overflow occurred and weighed again. Comparing shaken with unshaken cans, there was a 6-fold greater loss of beer in the shaken group (average 3.45 g vs 0.51 g; P < .01). However, tapping did not produce a statistically different reduction in the loss of beer in the shaken group (difference .159 g; 95% CI .36 g to .04g). There was no effect of tapping in the unshaken group. There are several limitations to this study. For some reason, only 1000 of the 1031 cans of beer completed the study (97%). Also, the study was limited to pilsners and the results might not apply to more common varieties such as India pale ales, saisons, and, of course, stouts (for which the small amount of loss might be clinically relevant). The results may not apply to other countries in which it customary to tap the can on either the top or the bottom, rather than the side.