The best time to pick lingonberries is from the end of August to the beginning of October. Lingonberries are picked in clean growing environments in sparsely populated areas away from population centres and where there is no polluting industry. 95% of Finnish forests are unfertilised, and so it is possible to sell the lingonberry as a certified organic product. Finland has the world’s largest picking areas that are certified organic! Approximately 10% of the annual lingonberry harvest is picked. Lingonberry-picking is a slow process since the berries are picked using handheld berry picking tools and it is not permitted to drive a motor vehicle in the forest.
During the picking phase, the lingonberries must be fully ripe and completely red. Clean buckets or boxes suitable for foodstuffs are used to pick and transport the berries. Wild lingonberries are picked using a handheld berry picking tool ("hand rake"). Industrial pickers use a so-called berry picking rake with a long handle ("long-handled rake"), which prevents backache since the picker does not have to bend over so often. Various berry picking tools are sold in Finnish stores and markets. Picking tools make the berry picking process quicker. However, berry pickers should remember not to handle the picking tool too roughly to avoid damaging the shrubs.
Lingonberries are emptied from the picking tool into buckets or containers in which the berries are transported for sale. It is best to protect picked berries from the sun, since warmth and light reduce the berries’ vitamin content. Hygienic working methods are used when handling the berries. The berry picker is the first step in a long quality chain for berry products.
Industry purchases the lingonberry for various needs
Each year, 6–11 million kilograms of lingonberries are purchased for industry from first purchasers. Berry pickers who pick berries for sale do not need to clean the berries, and loose leaves from the shrub may be included with the crop. Pickers transport the berries themselves to first purchase points. The first purchaser usually purchases the berries uncleaned. In this way, the berry keeps better before handling. Lorries transport the lingonberries from first purchase points to industrial facilities for freezing. The lingonberries are frozen in tunnels on the day they are picked at temperatures of -40 degrees Celsius.
After the harvest season, the frozen lingonberries are cleaned using industrial cleaning equipment. Debris is removed using an air blower. The machinery also removes the stem and optical food sorter removes discoloured berries. Individually quick frozen (IQF) lingonberries are sold by the berry industry to industries which produce berry products, to professional catering enterprises and to households in small packages via food stores. In industry, the quality of berries and resulting berry products is strictly monitored. This ensures that the berries’ nutritional values and quality are preserved better than is the case with slow-freezing at home.
Drying is another processing method in addition to freezing. Lingonberries are primarily air-dried in a warm air current with a maximum temperature of approximately +45 °C. Dehydration prevents enzyme and microbial activity in the berries. The lingonberry is sufficiently dry when its residual moisture content is approximately 10–12%. One kilogram of fresh berries produces approximately 100 grams of dried lingonberries.
It is also possible to use the more expensive freeze-drying process when manufacturing specialty products. Freeze-drying involves the dehydration of berries using a vacuum at extremely low temperatures (approx. ‑50 °C), whereupon the water transitions directly from a solid to a gas state. The shape, appearance and nutritional content of the products are preserved extremely well.