How do they produce salad greens?

How do they produce salad greens?

Bagged salads and greens are convenient and versatile. Niki Bezzant follows the salad from field to plate.

Most salad leaves and greens for bags are grown outside, year-round, although some lettuce and rocket is grown hydroponically or under cover.

Hydroponic growing involves no soil. Plants are supplied all their nutrients in water. Greens grown in tunnels or greenhouses are grown in soil, the same as if they were outside.

Seasonal weather variations mean outdoor crops can take longer to grow in the winter than in summer so growers have to plan carefully to make sure they have a constant supply all year. Growing methods vary but most growers do need to use fungicides, insecticides and herbicides. It’s in the growers’ interests, however, to use these as little as possible, so often non-toxic chemicals and bio-protection products are also used. Whatever sprays are used, there is a stand-down period of no spraying before harvesting. This varies and can be up to 21 days, depending on the crop and the sprays used. The stand-down periods are designed to make sure the leaves are safe to eat, and testing is carried out regularly to make sure.

Leaves are picked by machine then quickly transported (within three hours) to processing factories where they are immediately cooled. Leaves are then graded to get rid of any substandard quality then washed several times. The first wash includes chlorine in a ratio of around 150 parts per million, to destroy any bacteria and other microorganisms that might be present. After the chlorine wash there’s another rinse in plain water. Once rinsed, the leaves go through drying machines to get them completely dry before bagging.

Some bagged salads (usually lettuce mixes) are ‘flushed’ with nitrogen in order to flush out oxygen and slow down the oxidation process, to slow down the ageing process of the leaves. This is mostly only done on cut salad mixes, where the edges would otherwise go brown (oxidise). Nitrogen used this way is not harmful to the food or to us.

Nitrogen is not added to bags of mesclun and spinach but the bags are filled with air to puff them up (like a potato chip packet) to help protect the delicate leaves from damage.

Bagged salad is usually in the supermarket within 48 hours of being picked. If kept refrigerated all through the process, from transport to store to home, salad leaves should last in the bag for seven days.

We’ve all had the experience of salad leaves going limp and soggy in the fridge. So as long as we keep salad refrigerated, is there anything else we can do to make sure it stays fresh? The experts at Snap Fresh Foods, who grow salads for the Krispkut brand, told us the original packaging is the best storage device, folded over and closed with a clip. If you have the luxury of a multi-compartment vegetable drawer, it is also useful to store ‘like’ produce together, ie. greens with greens and fruits with fruits.

First published: Dec 2012

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