"The seam gets in the way and when you finally open it, hot chocolate all over your hands," she said.
Ms Hankinson said if a person with average strength can open a food package with the thumb-and-little-fingers of both hands, it is likely older people, the disabled and those with arthritis also can.
The use of the thumb and little fingers to open a food package was dubbed being able to "51-it" - as the approach used fingers 1 and 5.
Student research showed that the "51-it" was equivalent to about 30 newtons of force, with international studies showing that in older people and those with arthritis, ordinary pinch grip forces of 30 newtons can be at their upper limit.
Local companies Busck Concrete and Comer Engineering even designed and built a contraption allowing students to test products with more precision.
Ms Hankinson said the campaign, dubbed "Tear It Off", was particularly relevant as the population aged. "There are currently 630,000 people over 65 in New Zealand. That's due to double by 2040," she said.
Jonny Wilkinson at Tiaho Trust said there were standards to ensure buildings could be used by everyone, so why not packaging?
"You tend to use things like teeth as a work around," he said. "I bought a new razor the other day and was trying to open the packaging and cut my finger. It added a new dimension to the phrase, 'I cut myself shaving'."
Dr Reti said a campaign video documenting the project and featuring Northland powerlifting champion Joseph Whittaker attempting to open tricky packages had been viewed more than 3500 times. Dr Reti's idea for the project came from his role as parliamentary facilitator for Arthritis New Zealand, he said.
More information can be found at facebook.com/tearitoffcampaign.
