CFW’s drying ovens are suitable for various nuts, including:

• Peanuts
• Pecan Nuts
• Walnuts

Late harvesting may reduce the need for drying, but also reduces quality, yields and shelf life. The oil content of most nuts prevent them from drying out completely (the exception is chestnuts). To determine whether nuts have dried adequately, several criteria are used. Pecans and walnuts should have nutmeats that shake around in the shell. The colour of the nutmeat should be light and snap sharply if bitten, and it should have a light taste. Drying nuts too long will make the shells crack.

CFW provides drying equipment for peanut production. We can supply custom equipment to provide optimal drying conditions.

Peanuts are usually dried mechanically to reduce the moisture content to below 12% (typically 7-10%). Careful and speedy drying is not only critical to product quality, but is crucial to food safety. Peanuts tend to fall prey to moulds which produce aflatoxins, which cause liver damage and are some of the most potent naturally occurring carcinogens. A significant proportion of the crop (as much as half) is lost because of contamination where drying equipment is not used. The chance of fungal penetration increases with kernel splitting, which also reduces the price of the product.

Drying peanuts in the field can result in excessively dry stems or vines, which can cause machinery to separate foreign material from the pods less efficiently.

Dryers used on the farm usually take the form of storage vessels (trailers or bins) with vents or air channels. Air heated to approximately 32 °C is blown through nuts with a high initial moisture content (> 18%), whereas the temperature can be increased to 38 °C for nuts that are dryer. These temperatures may be varied somewhat according to the relative humidity (RH) of the air that is used.

For specialised drying applications such as pecan nut drying, CFW offers equipment designed to most efficiently produce a good-quality product.

Commercial marketing of pecan nuts depends heavily on product quality. The flavour and colour must be up to standard, and a crisp texture, with an internal moisture content of below 5%, is desirable. Stale, bitter or rancid nuts are unmarketable. The flavour is especially sensitive to degradation after the harvest and is affected by many variables, but especially the oil and moisture content and harvest time of the nuts.

Properly drying pecans helps to preserve the desired characteristics and prevent product degradation, thus improving market prices. Artificial drying is reported to be viable even for pecans that have been harvested early. With artificial drying at room temperature, acceptable flavour and texture of these nuts can be obtained, while pecans dried at 35 °C have a normal flavour but are brittle.

CFW produces equipment designed for commercial walnut drying. A wide variety of drying units, fans and dehumidifiers are available.

Maximising walnut shelf life and product quality requires fast and reliable processing after harvesting. They are ordinarily hulled before drying, since this significantly reduces energy requirements.

The drying phase of this process reduces the internal moisture level from 25% to 8%. While sun or air drying without mechanical means can be used, it is too slow in bad weather and too labour-intensive for modern commercial enterprises. Today, stationery bin, pallet bin, trailer and modified grain trailer dryers are commonly used. These systems have different advantages and disadvantages. Pallet bins can handle small lots, as can stationery bins, provided that an appropriate bin size is chosen. Modified grain trailers are the most convenient for bulk delivering to handlers, and they also have low capital costs. Bins have a relatively high capital cost.

With bins, significant overdrying often happens at the bottom because a moisture gradient is produced. Dryer performance can be controlled by changing air temperature, ambient humidity, and air flow rate. Air flow rate in particular has a significant influence on drying times; doubling it can reduce drying time by about a third.

Speedy and even drying throughout the layer of nuts is clearly significantly influenced by the available equipment. CFW specialises in fan-assisted drying equipment and has provided drying systems for a wide range of industries in the past, designing and manufacturing custom-made equipment where necessary. Contact our sales engineers for more information.