We had an interesting visit to SpringThyme Oils, a firm specializing in producing infused oils.  They buy approximately 400 tons per year of either sunflower or virgin olive oil.  This oil is infused with herbal flavorings prior to sale to commercial accounts in the restaurant trade and in bulk to bottling firms.  The most popular herbs are basil, chili pepper, garlic and mint.  Others being prepared include coriander, parsley, rosemary, spring onion, and thyme.

The processing involves placing each herb in an infusion kettle with three kilos of oil to each kilo of herb.  Diffusion is controlled with a combination of temperature and time factors.

The task for Vincent is to separate the oil from the herb once the herb’s essential flavors have been infused into the oil.  This separation must be achieved with conflicting requirements:

1. Squeeze out every drop of oil and
2. Minimize the suspended solids flowing out with the oil.

We found that pressability varied greatly.  Parsley pressed like a charm!  On the other hand, both basil and spring onion were very slimy:  they tended to channel (spit) past the cone and press capacity was reduced because they blinded (covered over) the openings in the screen of the press.

Because of the wide range of herbs involved, the screw press being built has lots of bells and whistles.  The screw is notched in order to collect fiber; these fibers will wipe (brush) the screen during operation.  The rotating cone feature is included to break up channeling of the cake as it discharges.  A VFD is being programmed both for automatic reversing pattern operation and for slow variable speed in the forward direction.  Both perforated and slotted screens are being supplied.  These will have the No Tools hinged mechanism to facilitate cleaning between batches.  The tight screw-to-screen clearance on the SpringThyme press will also help keep the screen clear and improve throughput.

We hope that it will be possible to use press aid to further improve both press capacity and the clarity of the oil.  High quality bleached cellulose fiber as well as less expensive rice hulls will be tested.  The larger fibers in press aid are known to scour the surface of the screen, while the fibers themselves both retain fine particulate and give the press something to bite on.