Countdown's meat supplies should be back to normal today after a supply glitch, but butchers are urging the government to allow them to run click-and-collect.
With smaller greengrocers, bakeries and butchers restricted to deliveries only at alert level 4, supermarkets have been dealing with high demand.
The workers have been widely praised but - perhaps due to the stress of lockdown and additional mask requirements - tension has run high for some customers.
One man was arrested for spitting at a Countdown staff member after being refused entry to a store in Christchurch while other customers have vented at a lack of meat on the shelves.
Countdown spokeswoman Kiri Hannifin told Morning Report that since the mask mandate started, staff had dealt with about 20 threatening incidents a day, but people were mostly doing the right thing.
"By and large people are very, very good and doing the right thing ... if it gets violent or aggressive or or too difficult for us we call the police."
Distribution centre workforces at risk from outbreak
The large workforce on the supply side of things was a concern, she said, raising risks for supplying the entire country if the outbreak should spread to the workforce.
"If we had Covid in one of our distribution centres that would impact food supply for all of New Zealand ... one of our DCs in Auckland looks after 40 per cent of the country," Hannifin said.
She said precautions - including strict protocols and working on split shifts - were being taken, but the outbreak had already meant some stores had not been able to reopen, with staff having to go into isolation.
Smaller retailers call for click-and-collect
Hannifin said some items with high demand were being limited to a certain number per customer.
"We put limits on the stuff that we know from bitter experience sells very well at times like this. We think Kiwis are probably back at baking but that's okay we've got good stock ... and we've got lots of fresh vegetables.
"In terms of fruit and vege, yeah of course we want all of our growers and the manufacturers and the merchandisers to be well as well ... we've been able to buy much more than usual because they're not being sold to hospitality, to restaurants, so we've been taking some of that extra - which is good, because it's selling."
The lack of meat on some shelves over the weekend had been due to a technical issue with a plant in the North Island, but there should be good supplies from today onwards, she said.
That may be small comfort for butchers, with reports of some working 15-hour days to meet demand and the deliveries-only restriction under alert level 4 piling on extra work.
Aussie Butcher New Lynn owner Reuben Sharples said it was simply not feasible, and called for the government to allow click-and-collect for stores with safe public health measures.
"If we were able to just do click and collect that would be so much more easier, but also masks are mandated now ... we are cleaning.
"My shop serves roughly 300 customers on a Monday to Friday each day ... we'd be able to produce those orders but we'd struggle to get those delivered, being a perishable good, and it's just not feasible for us to do it."
He said butchers were typically earning $25 to $30 an hour, doing 50 hours a week, and the wage subsidy simply did not cover the costs.
"It's all this uncertainty. Even with the wage subsidy I'm about $700 down just on wages a week. [The wage subsidy] barely covers a part-timer, you know, on the $600."
He questioned why they could not open when suppliers like dairies were able to.
Retail NZ chief executive Greg Harford said the click and collect model would be appropriate for level 4, had been done overseas, and would take the pressure off supermarkets.
"At the moment you're able to go down to your local supermarket, you're able to join a queue, some of those queues are very long and it's taking quite a bit of time and creating quite a lot of stress for customers.
"If your local community greengrocer, butcher or baker were able to be open that would take a lot of pressure off."
"Now, obviously, we're required to be masked at level 4 because of the complexities of Delta but also there are things that can be done around distancing and hygiene that really do help keep people safe."
Supermarkets urge shopping in store to curb demand on online services
Hannifin said supermarkets were also at absolute capacity when it came to online deliveries.
They were working on solutions like having "dark stores" set up to service online deliveries only, but those took time and would required more workers - which the supermarkets were short of at the moment.
She called on the public to help by shopping in-store if possible, to give priority to those who could not.
"What we all could do immediately is if you can shop in a store then please do because the stores are super safe ... and that would meant that the online service is freed up for those who really need it including 400 of our own team who are at home and can't leave."
"Demand is very high, we're also mindful of having to look after the Chatham Islands ... the Great Barrier to look after as well."