Cryogenic Grinding to Preserve the Original Essence of Spices
Shakeela Malik
Introduction
The term “cryogenics” is derived from the Greek word meaning ‘generation of cold temperatures.’. Cryogenic grinding is the cooling or chilling process of materials, which is capable of grinding the hardest materials effectively and also allows multi-component waste and hard composite materials to be recycled. Nearly all material breaks down when exposed to cold temperatures. The uniform size reduction technique in cryogenic uses cold energy, 0 to – -56.6°C from designated cryogenic fluids like liquid nitrogen for cooling, embrittling and inert materials before and during grinding processes. Once the materials come to a glass transition temperature, spices become brittle permitting finer grinding (Saxena et al., 2013). This technique is usually employed for the grinding of a substance containing heat-labile compounds, namely volatile oils in seed spices, and does not damage or affect the chemical composition. During the traditional grinding process, heat is produced due to the high-fat content in spices, whereas energy is employed to break a particle into a smaller size. This heat created causes the grinder to reach above 95°C during a regular grinding procedure. The increased temperature causes the final product to reduce heat-sensitive constitutes and approximately 30% loss of volatile content as well as loss of original colour. The melted fatty oils hinder grinding by sticking ground powder onto the grinder surface (Sharma et al., 2014).
Cryogenic grinding of spices
India is the largest producer and exporter of various kinds of spices, including perennials such as pepper, cinnamon, nutmeg, cloves, and cardamom as well as annuals such as chili, coriander, cumin garlic, turmeric, and many more. These spices are used as whole or ground in varied proportions in most Asian cuisines. Ground powders of various spices are among the value-added products that show great opportunities for commercial utilization (Saxena et al., 2018). The added value is mainly concerned with the extrinsic (or physical) and intrinsic (or chemical) qualities of the product. The intrinsic quality is related to the retention of secondary metabolites in essential oils and oleoresins. Appearance, shape, colour, and texture determine the extrinsic characteristics. Additionally, export quality standards require the absence of aflatoxins, pesticide residue, microbiological quality, solvent residue, heavy metals, and sulphur dioxide. The physicochemical features of the production area, harvesting, and post-harvest activities vary considerably in terms of agro-climatic circumstances. However, the ultimate export requirement for spices remains the physicochemical quality as these qualities defines its market grade. Higher technology for manufacturing, processing, packing, and delivery, therefore, requires strict rules and quality preferences. Cryogenic spice grinding hence has potency in promoting exports and the domestic market (Balasubramanian et al., 2012).
Developments in spice grinding
Cryogenic influence on ground spice quality is determined by comparing the cryogenic and ambient milling effects on the colour of spice. Cryogenically ground spices had better colour retention, due to low-temperature grinding (Liu et al., 2013). At low temperatures, a wide range of materials become embrittle making it easier to grind. Cryogrinding has proven to be an effective process for particle size reduction (Ghodki and Goswami, 2016).
Advantages of cryogenic grinding over traditional grinding
The advantages of using cryogenic grinding over traditional grinding are; improved productivity by optimizing particle size, enhanced flavour strength, decreased wearing of grinding devices (Karam et al., 2016), possibility to separate composite materials within the mill, increased rate of output, low usage of energy, fine particle size and even distribution of particles, reduced cost of grinding, enhanced pouring characteristics due to finely ground ingredients and reduction in microbial activity (Junghare et al., 2017).
Disadvantages of cryogenic grinding
Despite its many benefits, cryogenic cooling has some limitations. Extra or additional controlling setup is necessary to monitor and manage the cooling process. The initial and maintenance costs are both high. Cryogenic fluids like liquid nitrogen are non-reusable hence uneconomical.
Storage of cryogenic fluid in extremely low temperatures is a work place hazard. When a cryogenic fluid stored at extremely low temperatures comes into direct contact with a workpiece during the machining process, there is a risk of damage.
Conclusion
Given the increasing day-to-day cost of raw materials and energy, it is essential to use the optimal quantities of raw materials while achieving the quality required. In the production of spices, those aspects can be fulfilled efficiently by using cryogrinding technology. If less expensive cryogenic fluids are employed, cryogrinding would be one of the best economically viable techniques in spice-making.
References
Balasubramanian S., Gupta M. & Singhe K. 2012 Cryogenics and its Application with Reference to Spice Grinding: A Review. Critical Reviews in Food Science and Nutrition, 52(9).
Ghodki B.M. & Goswami T.K. 2016 Effect of grinding temperatures on particle and physiochemical characteristics of black pepper powder.
Gholap, T.A. & Mohod, S.A. 2015 Review on experimental analysis of cryogenic cooling on various machining processes. International Journal of Advance Research in Science and Engineering, 4(9).
Junghare H., Hamjade M., Patil C.K., Girase S.B. & Lele M.M. 2017 A Review on Cryogenic Grinding. International Journal of Current Engineering and Technology, 7.
Karam M.C., Petit J., Zimmer D., Baudelaire Djantou E. & Scher J. 2016 Effects of drying and grinding in production of fruit and vegetable powders: A review. Journal of Food Engineering, 188.
Karthigayini S., Sahana S. & Goonasekere K.G.A. 2020 Methods to increase the grinding efficiency of spices – A review. North American Academic Research, 3(5).
Liu H., Zeng F., Wang Q., Ou S., Tan L. & Gu F. 2013 The effect of cryogenic grinding and hammer milling on the flavour quality of ground pepper (Piper nigrum L.). Food Chemistry, 141(4).
Saxena R., Soni A., Saxna S., Rathore S. & Barnwal P. 2013 Cryogenic Grinding: A Physical Technique to Retain Volatile Content in Natural Products. International Journal of Modern Physics: Conference Series, 22.
Saxena S.N., Barnwal P., Balasubramanian S., Yadav D.N., Lal G. & Singhe K.K. 2018 Cryogenic grinding for better aroma retention and improved quality of Indian spices and herbs: A review. Journal of Food Process Engineering.
Sharma L.K., Agarwal D., Sharma Y., Rathore S.S. & Saxena S.N. 2014 Cryogenic grinding technology enhances volatile oil, oleoresin and antioxidant activity of cumin (Cuminum cyminum L.). International Journal of Seed Spices, 4(2).