Fonterra says events like the recent botulism contamination scare are extremely unlikely to occur again.
The company says the discovery of plastic in batches of protein led to reprocessing at its Hautapu plant during which a piece of "non-standard" equipment was used, which was exposed to high levels of the bacteria.
Strategy director Maury Leyland told Morning Report the company's systems had responded very well, but there is room for improvement.
She said Fonterra will continue to be cautious about any possible contamination of its products.
Chief executive Theo Spierings maintains one of the biggest mistakes was that he was not told soon enough.
He and Fonterra chair John Wilson left for China on Wednesday night.
Trade Minister Tim Groser said many questions remain unanswered and Fonterra still has plenty of work to do.
