Japanese study finds ‘optimum’ aluminum bottle opening size for Coke drinkers

By Ben Bouckley

- Last updated on GMT

Related tags Drink

N.B. This photo is purely for illustrative purposes, and does not denote a bottle used in the study. Picture Copyright: Tom Marshall/Flickr
N.B. This photo is purely for illustrative purposes, and does not denote a bottle used in the study. Picture Copyright: Tom Marshall/Flickr
The majority of Japanese consumers believe that the opening diameters of screw-top aluminium bottles are too small, a study has found, while also determining that 33mm is the optimum size for 'drinking ease'.

Writing in the journal Applied Ergonomics​, researchers Takanori Chihara and Koetsu Yamazaki said that Japanese consumers were now familiar with such bottles, but that the majority felt that a 28mm opening was too small and a 38mm opening too large.

Therefore, the researchers developed a model to assess consumer feelings (14 Japanese university students: 4 of whom were female) when they drank directly from a bottle opening, to help assess the optimum bottle opening diameter.

Optimal drinking ease

“We know that there exists an ideal volume of beverage flowing into the mouth, at which consumers feel most comfortable while drinking directly from bottles.

“Therefore, we define the evaluation function of drinking ease in terms of the difference between the actual volume of fluid in the mouth and the expected ideal volume.”

If this difference was small, consumers probably felt comfortable drinking the beverage, the researchers said, adding that they considered a design variable (opening diameter) and two state variables – the volume of beverage remaining in the bottle and consumer height.

Conducting tests on green tea and Coke, Chihara and Yamazaki found that the optimal opening diameters for consumers were 35.4mm and 34.4mm respectively.

They cautioned that their results only applied to study participants, but said the results conformed with a previous study finding that 33mm was best-suited for young Japanese adult consumers, irrespective of beverage type.

“These results are in agreement with results of our previous study that an opening diameter of 33m is optimum for young Japanese adults.

“Thus, we confirm that the proposed function is accurate; it can be used to design bottle openings to suit consumers of various age groups and types of beverage,” ​the authors wrote.

Beverage type affects opening...

Beverage manufacturers should optimise bottle opening dimensions according to beverage type, Chihara and Yamazaki wrote, and important variables such as height that affected preference.

One weakness of the study was an over-dependence on students as subjects, they added, adding that children would perhaps prefer smaller openings.

Drinking satisfaction was affected by opening diameter, material and shape of bottles, Chihara and Yamazaki said, adding that the latter two factors hardly changed due to “ease of recycling and the forming process”,​ hence the cap diameter focus.

Thirst levels and beverage preference might also affect drinking satisfaction, the researchers wrote, before noting that these variables – as well as the material, shape, and opening diameter of the bottle – should be subjected to an ‘uncertainty analysis’.

Title: ‘​Evaluation function of drinking ease from aluminium beverage bottles to optimum bottle opening diameter and beverage type’

Authors:​ Takanori Chihara and Koetsu Yamazaki

Source: Applied Ergonomics ​43 (2012) 157-165 

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