Expeller pressure

An expeller press is a screw-type machine. The principle of the expeller press is to force the material to be extracted into a tapering tube by means of a rotating screw. The tube is perforated along its length by narrow slits and terminates in an adjustable cone that gives a variables gap between the cone and the tube exit.

The machine uses friction and continuous pressure from the screw drives to move and compress the material. The fat is forced out through the tube slit.

In processing of natural oils, the oils are crushed from seeds or grain, using the hydraulic action of an expeller press. No heat is involved in the pressing and no chemical antioxidants are added to preserve the oils. The oils seeps though small openings that do not allow seed fiber solids to pass through.

Expeller pressing yields less oil than solvent extraction, usually 50 to 70 percent of the oil, so expeller-pressed oils are usually more expansive than conventionally processed oils.
Expeller pressure

Harvesting blueberries

Blueberries are one of very few fruits native to North America, which continues to be the largest producer of them in the world. They should harvest when they are fully colored and handling should be minimized as they are very delicate and damage easily and the bloom on the fruit surface can be destroyed.

The berries are very small and have to be picked by hand and hand harvesting of highbush blueberries is labor intensive and requires as many as 1150 hours of labor per hectare.

To get the highest quality berries, harvest 4 to 6 days after the berry turns completely blue. If picked earlier, the berries will not be as large and the flavor will not fully developed.

Over the row, self-propelled vibrating machines have been developed for harvesting   blueberries. The use of mechanical vibratos nearly triples worker productivity and reduced harvesting cost by 55%.

Even though the picking cost is lower for mechanically harvested fruit, more berries are picked per hectare by hand and they have a higher value.

Harvesting blueberries, low bush blueberries like there are in Maine, was accomplished using a tool called a rake. A rake is an odd shaped tool that has a handle. Low bush blueberries require the harvester to get drown to ground level.

Mixtures of soft ripe and hard ripe fruits should be avoided as the over-ripe ones can speed deterioration.
Harvesting blueberries