Corrections is trying to prevent prisoners from stockpiling fruit after inmates were found to have made an alcoholic drink out of it before a major riot at Spring Hill Prison.
The alcoholic concoction also contained hand sanitiser, which has now been removed from all New Zealand prisons.
Corrections chief executive Ray Smith told Parliament this morning that gang-related offenders had been consuming an alcoholic substance for a long period before the eight-hour riot, the worst in a New Zealand prison in 15 years.
The substance was believed to have been made out of an alcoholic hand sanitiser and fermented fruit.
The violent melee involved 23 prisoners and led to a huge fire at the Waikato facility.
Mr Smith said that as a result of the riot, alcohol-based sanitiser had now been removed from all facilities.
Prisoners were also banned from having more than seven pieces of fruit at once. They were given two pieces a day with their meals, but could also buy more.
Mr Smith said limiting the supply of potentially alcoholic substances was a problem in New Zealand prisons and internationally.
Staff had considered initiatives to limit the risk by reducing the amount of sweeteners that were given to prisoners, because they could be used to make alcohol.
Staff had also considered putting holes in any plastic bags given to prisoners so they could not be used to store liquids.
Reviews have found a number of factors led to the riot, including a high concentration in high-risk prisoners at the time.