Cold Grinding of spices

Process Description

For spices such as pepper, cinnamon, caraway, cardamom or cloves, aromas and flavours can be lost due to the high temperatures generated by grinding energy. Cryogenic mill cooling grinds the products gently. As a result, a significantly higher proportion of the essential oils is retained. In the case of products with a very high oil or fat content, such as nutmeg, oilseeds or meat meal, grinding tools clog up during warm grinding causing the grinding process to stop. Through cooling with cryogenic gases, the product remains free-flowing and leaves the mill without sticking to it. By cryogenic product cooling in a paddle screw cooler, the high fat or oil content is frozen and thus clogging of the grinding component is prevented. Other foods retain vitamins and proteins.

Gas Application

During mill cooling, liquid nitrogen or carbon dioxide is sprayed directly into the grinder which lowers the temperature. By suppressing the heat generated during grinding, this cooling technique ensures stable performance of the process and increases the quality of the milled product.

A product cooler freezes materials rich in oil or fat. From the feed container, the material to be ground is passed by means of a metering screw into the paddle screw cooler. Here it is cooled by sprayed liquid nitrogen and passes together with the nitrogen into the mill. This simultaneously cools the crushing process in the mill. Special temperature control and a liquid nitrogen control valve unit regulate the amount of nitrogen required to reach a defined temperature.

Advantages:

• Good grindability of products with a high proportion of oils, fats and moisture
• The material remains free-flowing; the machine does not clog up
• No thermal damage through overheating of temperature-sensitive substances
• The essential oil content remains almost unchanged and intact

Messer Solution

The Messer Group operates a highly specialised test facility, which offers the opportunity to profit from process developments, estimate production costs or produce sample batches. Qualified sample grinding is carried out using liquid nitrogen. All grinding parameters, such as throughput, electricity and nitrogen requirements, as well as the particle size distribution are measured, evaluated and made available to the customer. The results obtained can be transferred to large-scale production.

In addition to purely producing grinding samples, this also allows an estimation of production costs under production conditions and a comparison to other grinding processes. 

Customers’ existing mills can also be optimised. Granulate coolers, nitrogen control valves and temperature control can be provided for carrying out tests on these plants on site.   

 Nutmeg, before and after cryogenic grinding

More information can be found here under 'Separation of composite materials'.