Since time immemorial, spices and herbs have been an ubiquitous part of several civilizations. Early documentation suggests that hunters and gatherers wrapped meat in the leaves of bushes, accidentally discovering that this process enhanced the taste of the meat, as did certain nuts, seeds, berries and bark. Over the years, spices and herbs were used for medicinal purposes. Spices such as caraway, pepper, fennel, garlic, mint, onion, poppy, etc. have been cited in several Egyptian medical books like the Ebers Papyrus (1500 BC).
Early Chinese publications like Pen-ts’ao Ching (The Classic Herbal) written around 2700 BC mentioned more than a hundred medicinal plants, including the spice cassia, which is similar to cinnamon. In Mesopotamia, King Merodach-Baladan II (721-710 BC) of Babylonia grew 64 different species of plants in his royal garden. He kept records on how to cultivate many spices and herbs such as cardamom, coriander, garlic, thyme, saffron and turmeric.
Closer at home, spices and herbs such as black pepper, cinnamon, turmeric and cardamom have been used by Indians for thousands of years for both culinary and health purposes. Sushruta (4th century BC) used white mustard and other aromatic plants in bed sheets to ward off malignant spirits. He also applied a poultice from sesame to post-operative wounds, which may have acted as an antiseptic. Medical writings of Charaka and Sushruta referenced several spices and herbs.
However, the same spices and many others were employed to flavour Indian food in both luxuries and daily staples. These spices steadily made their way throughout the continent, as travellers travelled through the area. Invaders and rulers have long sought India’s golden mine of spices, right from Genghis Khan of the Mongol Empire to the many rulers of the British Empire. Because of this increased interest in Indian spices, India eventually became the global hub for what became known as the “Spice Trade”. The globe couldn’t get enough of India’s tastes, from cumin to coriander, saffron to sage, black pepper to black mustard seeds.
Globally the Spices Market is projected to grow from USD 6 billion in 2021 to USD 14.51 billion in 2026 at a CAGR value of 6.5%. India accounts for almost 75% of the global spice production. The Indian spices and seasoning category is a large and attractive market. Blended spices will reach 35% market share of the total organized spices pie in India by 2025. Branded Spices Market is set to double to INR 50,000 crores by 2025. The recent acquisition of 51% stake in Badshah Masala by Dabur and Wipro Consumer Care acquisition of Nirapara spices will make this space Spicier and Hotter in days to come.
With such a vast range of cuisines and mixed cultures, the demand for different spices is increasing rapidly in the Global Market. Studies have shown that there are over 100 different varieties of species available in the market for various purposes. These spices, other than just adding flavour or aroma are also used as food preserving agents.
Experiments and research have proved that these spices show anti-microbial reactions to the activities of microorganisms that affect the food, its quality and its shelf life, thus, acting as a preservative and shield from bacterial microorganisms.
Besides acting as a preservative agent, these spices also have immense medicinal benefits. Spices such as turmeric is known to cure any kind of inflammation, which in most cases is the cause of severe diseases and illnesses. Studies have again proven that if consumed in a small proportion every day, it reduces the risk of inflammation of the brain and the chances of disorders like Alzheimer’s or depression. Animal studies have also been conducted using turmeric as the curing treatment, showing that this spice has cancer-curing properties in it. Spices like cinnamon have the properties to regulate low blood sugar levels.
Spices are seeds, dried fruits, roots and barks that are used to give flavour, aroma and colour to food. Several spices from various origins and cuisines are available in various forms, including ground, crushed and whole. Each of these spices provides a unique flavour, aroma and taste to the food. Some of the commonly used spices are cinnamon, black pepper, cumin seeds, nutmeg, cloves, chilli powder, turmeric, ginger and garlic.
Pepper accounts for almost 15.0% share of the global revenue in 2021. Pepper is an aromatic spice derived from the fruit peppercorn and has been used for centuries. It includes black pepper, green pepper and white pepper, available in whole or ground form. Black pepper is the primarily used form of pepper worldwide and is also commonly known as the king of spices. Its medicinal benefits such as pain reduction and anti-oxidant properties are increasing its usage.
Turmeric is expected to register the fastest CAGR of 7.1% from 2020 to 2027. Turmeric is relatively new in American cuisine, but has been used in Asia and the Middle East for thousands of years. It is more accessible in a ground, bright orange powder form and can be found in any spice aisle. It is a versatile powder that can be added to numerous dishes and has a range of culinary purposes, as it contributes to a peppery flavour, yellow colour and mustard-like scent. It complements both savoury and sweet dishes. However, its earthy taste makes it go well along with more savoury, spice-based recipes.
Powdered spices accounted for more than 50.0% share of the global revenue. Growing consumer preference for whole spices to save time and attain authentic flavour is anticipated to propel their demand. These products are largely sold in the form of various mixes. Powdered forms are used as marinades, rubs, snack mix and flavouring agents for curries.
Spice Grinding
Grinding is an age-old technique of particle size reduction to produce powders that can be used as intermediate or end products. Grinding aims to reduce the size of the particle by mechanical means, such as impact, compression, shear and cutting.
Hammer mill, plate mill, ball mill, pin mill, roller mill are commonly used grinding equipment for spices. Grinding is an energy-intensive process in which only 1% of the total input energy is utilized to reduce particle size and rest of the energy is dissipated as heat. Consequently, the grinding process is accompanied by a substantial rise in the temperature of the ground product, ambient air and grinding mill.
As the aromatic, flavouring and therapeutic components present in spices are heat liable in nature, an increase in temperature during grinding significantly lowers the quality of ground spices. Product temperatures of up to 90°C in ambient grinding, 40°C in wet grinding and 26°C in freeze grinding were observed. Temperature-induced quality loss to the tune of 40% was reported in the conventional grinding process.
Spices like nutmeg, clove and cinnamon contain high levels of fat, while capsicum, chilli etc. contain high moisture content. This causes clogging and gumming of mill, thus affecting the throughput and quality of the ground product. High moisture content materials often stick to the parts of the mill.
Also, due to intimate cyclone effect of the air in the vicinity of grinding zone, aromatic substances in spices oxidize and become rancid. Higher energy consumption and also increased tensile residual stress increases the maintenance cost and reduces tool life. Therefore, minimizing heat generation and quick removal of heat during grinding becomes crucial to maintaining the end product’s quality.
The schematic diagram, principle and application of different size reduction equipment are presented in Table 1.
Cryogenic Grinding
Cryogenic grinding, also known as freezer milling, freezer grinding and cryomilling is the act of cooling or chilling a material and then reducing it into a small particle size. During normal grinding process, the raising temperature can be minimized with the aid of cryogenic fluids like nitrogen in its liquid state (LN2). This low temperature makes the material brittle. When the process of grinding progresses, this helps in obtaining finer particles in the end product. This also permits to increase the rate of feeding and reduced power consumption during grinding phenomena.
Also, lower values of temperature during grinding helps to mitigate other undesirable changes such as oxidation and discolouration. Spice cryogenic grinding (cryo-grinding) is fairly an advanced technology and therefore there are very few units presently operating in India.
To achieve an end product with retained volatile oil content, freezing and chilling are the possible modes. Low temperature can also be obtained via external circulation of refrigerant or chilled water around the grinding apparatus or mixing whole spice with solid CO2 or dry ice and then carrying out the process of grinding. However, for large scale industrial operations, such methods are not feasible because of inefficient rates of heat transfer.
The very low temperature is obtained by using substances known as cryogens, (Table 2) like liquid helium, liquid nitrogen, argon, neon, krypton, methane, hydrogen, natural gas in liquid form, etc. At ambient temperatures and pressures, all cryogenic liquids are in gaseous state and hence these gases need to be cooled to the temperature below atmospheric to liquefy them. The cryogens boil at a temperature less than -150°C. The vessels which are used to keep cryogens are referred to as Dewar flask, with which enough insulation is provided.
The Cryogenic Grinding Process
Cryogenic grinding is a method where the size of solid materials is reduced in the cooling environment created by cryogens to retain quality of ground product. This process is considered as an effective mode of cooling or refrigerating many products in the Food Industry. In this process, the cryogen in liquid state around -195.6°C gives the cooling effect required for pre-cooling the spices, in order to keep up the required low values of temperature by taking away the heat produced during the process of grinding.
Liquid nitrogen not only maintains the low temperature, but also vapourization of it to the gaseous form produces dry and an inert atmosphere, by which it adds protection to the spice quality. The raw spice pre-cooling as well as maintaining uninterrupted low temperature inside the grinding mill minimizes moisture loss and loss of volatile oils; hence holding maximum strength of flavour per unit quantity of spice, in order to achieve a good quality end product.
The principle of working of a typical low temperature or cryo-grinding system is represented in Figure 1 and Figure 2.
The compressor is run before the start of grinding. The exit valve of the compressor is slightly opened in order to obtain the necessary pressure in the vessel of liquid nitrogen (LN2), based on the temperature to be kept while grinding. LN2 is made to enter into the distribution system of the screw conveyor assembly. The grinder and the assembly of screw conveyor are cooled to the required grinding temperature of the order -160°C to -70°C.
Using D.C. motor of variable speed, the speed of conveyor may be selected according to the required feed rate to the grinder. The grinder is put into operation once the sample material is sent to the inlet of the screw conveyor system. Once the material passes through the pre-cooler it is allowed to pass into the grinder.
The grinding happens at the pre-defined temperature in the range of -160°C to -70°C. If temperature goes up during powder preparation or grinding, it is desirable to increase the rate of flow of liquid cryogen. The powder is collected at the outlet of the grinder in a bag attached to the system and the nitrogen vapours are allowed to go out.
Advantages of Cryogenic Grinding System using Liquid Nitrogen:
• Reduction of microbial load;
• Preservation of natural spice quality attribute;
• Minimum thermal fatigue;
• Higher retention of volatile oils;
• Prevention of oxidation and rancidity;
• Enhanced production capacity;
• Possibility of fine grinding up to 50 Microns.
Drawbacks of Cryogenic Grinding System:
• Operations cost is very high;
• Equipment maintenance is high;
• The use of cryogen in humid atmosphere may form ice around the system piping leading to stoppage of cryogen delivery;
• The process has economic considerations that should be solved.
Summary
There are tons of data available around the potential ability of technologies like cryomilling to transform the Spice Industry. When compared to ambient ground, cryo-ground cumin and coriander powder contains 2x total phenols and anti-oxidants. Cryo-ground black pepper retains 95% volatile oils, as compared to ambient ground, which results in 50% VO loss. Cryo-ground chillies retained majority of their nutritional parameters, such as protein, moisture, crude fibre, capsaicin, when compared to ambient pulverization.
With its ability to provide a superior quality product, it’s a matter of time Cryomilling will be the Go-to-Technology for Spice Processing.
About the Author:
Bharat Sawnani
Founder, Elevantus Food Consultants
Email ID: sawnani@gmail.com
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