Preventing mold on Berries

The Pacific Northwest is a treasure-trove of berries of all kinds. The soil and climate is perfect. The problem of buying perfectly ripe berries directly from a farm is that they go moldy in a heartbeat. It seems that pasteurizing them works wonders -- from the New York Times:

Prolonging the Life of Berries
One of summer�s great pleasures is eating berries of all kinds by the basketful. One of summer�s great frustrations is having baskets of berries go moldy overnight, or even by nightfall.

Over the years I�ve come up with various strategies for limiting my losses, but this summer I came across a surprising one, the most effective I�ve ever tried. Thermotherapy, it�s been called. A very hot fruit bath.

Fruits go moldy because mold spores are everywhere, readily germinate on the humid surfaces of actively respiring, moisture-exhaling fruits, and easily penetrate the smallest breach of their thin skins.

A bit more talking about technique:

The strawberries fared best when I heated them at 125 degrees for 30 seconds. In two samples from different sources, this treatment gave a total of 1 moldy berry out of 30, where the untreated baskets had 14. I also treated some bruised berries, including one with a moldy tip. After 24 hours none were moldy. The tip mold not only hadn�t spread, it had disappeared.

I tried the same treatment, 125 degrees for 30 seconds, on raspberries and blackberries, and got the same good results. There were many fewer moldy berries in the heated samples.

For thicker-skinned blueberries, a Canadian study recommended a 140-degree treatment for 30 seconds. I tested it twice, with samples of around 150 berries each time. That heat took the bloom off. It melted the natural wax that gives the berries their whitish cast, and left them midnight blue. It also cut the number of moldy berries from around 20 per sample to 2.

Research has also shown that exposure to hot air slows fruit spoilage. But hot air can take several hours, and I found it harder than hot water to apply precisely in the kitchen. I did spread some raspberries out on a sheet pan lined with towels, and put them in a 150-degree non-convection oven for 20 minutes. The berry bottoms got hotter than the tops, which were cooled by evaporation. Still, only 1 out of 48 heated berries became moldy, compared with 7 out of 52 in the unheated basket.

Interesting -- hot air also works well according to the article. Most berries are sorted and cleaned on an open mesh conveyor belt and part of the cleaning process involves a fan blowing air up through the belt to carry off leaves and dirt. Easy enough to attach a heater...