Postharvest Processing of Spices

Abstract

Black pepper, cardamom, chilies, turmeric, ginger, and garlic can be considered as important spices, besides some more seed spices that are largely produced, consumed, as well as exported by India. Postharvest operations of spices start at the farm/plantation level primarily and secondary processing at the industry/trader’s level to reach the consumers. Tertiary processing starts at industries, and the value-added/final products are export-oriented, earning valuable foreign exchange. Postharvest technology of spices has made much advancements in the last few decades, and this industry is growing. Information on postharvest technology of important spices is detailed in this chapter.

Turmeric occupies an important position among locally consumed spices. Turmeric rhizomes are harvested by manual digging using a specially designed hoe-type hand tool after the plant withered and rhizomes are collected. Power tiller and tractor-operated diggers are used for efficient digging of rhizomes with capacities of 1.5 acre and 4 acre per day of 8 h, respectively, with 65–70% savings in time and 90% savings in cost. Curing is the primary process at the farm level involving boiling of rhizomes, drying, and polishing. Traditionally boiling of rhizomes is done using open vessels which are time-consuming, less fuel economy, more water-consuming, and labor intensive. Modern boiling systems using steam are in place which is fuel efficient, less time-consuming, etc. Though dryers are available for drying of boiled rhizomes, sun drying is followed in a large scale. The dried turmeric rhizomes are polished using power-operated polishers to remove the scales and root bases to get brighter color. Besides culinary purposes, turmeric is used in the manufacture of kum-kum, curcumin, and turmeric oil.

Black pepper, the dried mature berries of a perennial climbing vine, has been termed as the “king of spices” and is widely used as a condiment due to its characteristic aroma, pungency, and biting taste. Harvesting is done manually by climbing the trees where the vines are trained, using the ladders. The spikes are nipped of by hand and collected in bags. Traditionally threshing is done by manual trampling. Power-operated mechanical threshers with a capacity of 200–600 kg of berries per hour are in use, besides hand-operated thresher with a capacity of 60 kg/h. Both sun drying (22–26 h) and mechanical drying (7–9 h) are followed in the plantations. Dried black pepper berries are cleaned and graded according to Agmark specifications based on diameter. White pepper, canned pepper, etc. are some of the value-added products of pepper.

Cardamom, called “queen of spices,” is the dried fruit of a perennial rhizomatous herb. Curing of cardamom is the process to reduce the moisture of freshly harvested capsules from 400 to 11% (d.b.). Conventionally kiln drying method is followed, where the capsules in the trays receive heat by radiation and natural convection, and temperature in the kiln is maintained at 45–55 °C by controlled burning of fire wood in the furnace. The drying time is about 24–36 h. Exhaust fans/ventilators are provided to flush out moisture-laden air and to control the temperature. The fuel requirement is about 100 kg per 100 kg of fresh cardamom. Garbling is the process of removal of flower stalks from the dried cardamom, which is achieved by rubbing the dried cardamom capsules against coir mat or wire mesh and winnowed. Also power-operated garbling gadgets are available. Grading of cardamom capsules is done based on Agmark specifications following the diameter ranging from 5.5 to 8 mm.

Chili, also called “red pepper,” constitutes an important commercial crop used as a condiment, a culinary supplement, or a vegetable. It is harvested at a moisture content of around 300–400% (d.b.) and needs to be dried to 11% (d.b.) for further preservation and storage. Traditionally chili is dried by spreading on cement/mud floor and sand bed. It takes 5–15 days to complete the drying depending on the type of floor and climatic conditions. Greenhouse solar dryers and mechanical dryers are also popular among the farmers. For a long period of storage, cold storage of chili at 4–6°C is preferred, which prevents from discoloration, aflatoxin, etc.

Ginger is grown for its aromatic rhizomes which are used as vegetable and spice besides medicinal purposes. Harvesting of ginger is done by lifting clumps with spade or digging fork, and the rhizomes are separated from the dried-up leaves, roots, and adhering soil. At the farm level, the harvested ginger rhizomes undergo washing, peeling, and drying. Peeling serves to remove the scaly epidermis and outer skin of ginger to facilitate faster drying. Brush type and other models of mechanical peelers for gingers are reported. Traditionally, the partially peeled ginger is sun-dried in a single layer in open yard for 7–10 days to a moisture level of 10% (d.b.) and stored well. Mechanical drying of sliced ginger usually leads to the loss of volatile oil by evaporation and takes about 10–12 h in cabinet dryer. Polishing of dried ginger is done to remove the wrinkles developed during the drying, by taking dry ginger in gunny bag and rubbed against itself by moving the bag to and from by two persons standing on either side.

Garlic is valued for seasoning and flavoring vegetables and meat dishes. Garlic bulbs are harvested by uprooting the entire plant by taking firm hold of dry leaves or by digging using any tool/implement. The unit operations involved in garlic processing are curing, drying, sorting and grading, packaging, storage, and transportation. Curing of garlic is the process by which the outer leaf sheaths and neck tissues of the bulb are dried. Normally it takes about a week for drying of foliage and outer scales. The roots are removed completely, besides any chunks of dirt from the roots. Cleaning consists of trimming the leaves and roots and removing the dirty outer wrappers. Vibratory sieve separators for cleaning and sorting and centrifugal aspirator for removing husk are commonly used. For long-term storage, garlic is stored at 0–2 °C. Garlic bulb breaker, flaker, and peel remover are the gadgets used in the garlic processing unit to reduce drudgery to the laborers and increase the efficiency.

Seed spices are an important group of spices, primarily used for flavoring, seasoning, and imparting aroma in foods. A wide variety of seed spices include coriander, cumin, fennel, fenugreek, carom seeds (ajwain), dill, nigella, celery, anise, and caraway. Value addition can be from its simplest form of cleaning and grading of material to completely different products such as essential oil, oleoresins, cryogenically ground powders, pastes, pickles, etc. Indian farmers, processors, and traders follow the ASTA and ESA standards besides the Agmark standards to maintain the quality standards for both domestic and export markets.