Managing thermal damage during spice grinding - Conventional V/S Advanced Spice Grinding Method

The importance of spices is reflected in their use as preservatives and the fact that they endow foods with flavors and aromas while also acting as a therapeutic agent, especially in the food and pharma industry.

Worldwide, the quality standards of spices are closely associated with various processing techniques one such critical process is grinding. Due to high-fat content in spices, heat is generated, while energy is used to fracture a particle into a smaller size in the conventional grinding process. Grinding of the spices causes a reduction in particle size and increases the availability of volatile oils inside the seed. The process involves material tearing or breaking by mechanisms such as impact, compression, attrition, or cutting and shearing. The methods used for grinding spices may be categorized into the following:

Conventional grinding- Hammer, Pin mill

Superfine grinding - Ball, Jet, Roller mill

Improved/Advanced grinding- Cryogenic, Dry Ice, Pre-chilling, Chilled air, multiple stage grindings

Mentioned below are some major problems of using a conventional method of grinding spices.

• More grinding time and specific energy requirement

• Higher loss of volatile oils as compared to advanced grinding methods

• Higher flavor and aroma loss as compared to advanced methods

Heat-induced quality loss- A major technical challenge

The grinding process is a very energy-intensive operation, which makes the spices prone to thermal damage. Energy consumption varies with grinding methods, moisture content, speed, feed rate, and sieve size. Due to the high energy generated during conventional grinding, volatile oil compounds, natural flavor, and the aroma of spices will be lost. Thus, the grinding step in spice processing needs special emphasis.

Over the years, it is observed that a continuous operation is difficult in normal grinding process as the fat melts and powder sticks on the grinding surface. The loss of volatile content can be significantly reduced by using the advanced grinding process of cryogenic technique using liquid carbon dioxide that provides the necessary refrigeration needed to pre-cool the spices and maintain the desired low temperature by absorbing the heat generated during the grinding operation.

Studies have shown that in improved grinding, chilled water circulation at 5°C retains 2.5% more volatile oil than ambient grinding. Double-stage grinding has 15–25% more volatile oil, active oleoresin compounds, curcumin, and fine turmeric powder than single-stage. Ultra-low temperature (−3.33 to −1.25 °C) has a significant effect on the retention of volatile oil (17%), and oleoresin (2%–3%) content with a 2–3% increase in moisture content of the powder. Finer particles with higher surface area and homogeneity in particle size distribution release more volatile oil than coarse particles.

Cryogenic grinding- Overcoming the shortcomings of traditional methods

Cryogenic grinding is a method in which liquid CO2 (boiling point of −195.6 °C) is used to pre-freeze the material before grinding. The reduced temperature during grinding leads to better retention of physicochemical properties, better sensory characteristics, flavor, aroma, and taste. It also offers other benefits like reducing grinding force, lowering specific energy requirements, and avoiding sieve clogging.

The extremely low temperature is maintained during grinding which allows condensation of the volatile matter and helps retain their presence in spices. This process involves the use of high-pressure liquified CO2 stored in a cylinder which is released at the atmospheric pressure to form carbonic snow/dry ice. The dry ice is mixed in the Ethylene Glycol water mixture bath and is further circulated by a pump to the heat exchanger to cool the air used by a downstream process. The chilled fluid is recirculated into the bath. The low temperature retains the volatile compounds in the spices for optimum quality and aroma. This technique helps maintain a consistent particle size while grinding and does not alter the chemical composition of the spices.

Benefits of CO2 Grinding:

• The circulating gas which is ambient air does not come in contact with CO2, so cylinders containing commercial grade CO2 can be used.

• Fast cooling, temperature independent efficiency and thermal stability.

• The only power consuming equipment is the pump required for circulating cold fluid.

• The chilled gas coming out of the heat exchanger is 100% saturated leading to less moisture loss from spices.

• CO2 is relatively inexpensive leading to economical operation.

• A complete skid mounted system is delivered.

Post grinding scenario

Post-processing, the cryogenic powder obtained needs to be stored and packaged carefully. Storage under ambient conditions and poor packaging may cause the cryogenic powder to become more unstable than convectional grounded powder.

Spice grinding leads to the generation of dust. Particle sizes lower than 420 μm may cause health and fire explosion issues. Dust emission may cause wear and damage to equipment, loss of material, unpleasant smell, and workers' health issues. Maintaining a clean environment by using dedusting systems in the process of spice grinding is key to a safe facility.

Jaivik Foods- Ensuring a smooth grinding process

Considering the current situation in production, processing, and increasing demand for quality spices from consumers, there is a need to develop a suitable and sustainable grinding technology for spices.

Jaivik Foods offers a complete dedusting system that allows you to carry your spice grinding activities without worrying about dust generation. Jaivik invests in pioneering research and innovation to bring its diverse clientele superior dedusting, high-performing, durable, and cost-saving systems. The company also allows you to explore grinding solutions suited to your product needs. Adept in advanced spice-grinding technology, Jaivik Foods can guide you in choosing the best equipment for your business. Contact them for a discussion and enhance your production activities.