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Post Harvesting

Post Harvesting Storage: Fresh rhizomes should be washed, and cleaned from debris, shoots and roots. When available, pressure washing is preferred as it is more efficient and tends to reduce the microbial load. Traditionally, rhizomes are killed by a 10 min. immersion in boiling water, which also inactivates enzymatic processes, then sun-dried. Another method is to scrape, peel, or slice rhizomes prior to drying. Peeling or scraping is advised for reducing drying time, thus minimizing mold growth and fermentation. However, while this process decreases the fiber content by removing the outside corky skin, it also tends to remove some of the oil constituents, as they are more concentrated in the peel, and therefore reduces some of the pungency. The peeled rhizomes may be bleached to improve appearance. After peeling and washing, rhizomes are first soaked in water for 2 to 3 hours, then steeped in a solution of 1.5 to 2.0% lime (calcium oxide) for 6 hours, and sun-dried. This procedure is used when a light bright color is desired. The Indian Spice Board recommends the following sequence for preparing dry spices: soaking in water overnight to loosen the soil, peeling/scraping with pointed-end bamboo splinters, washing off the residual peel, sun drying for one week, soaking in 2% lime for 6 hours, and final drying (www.indianspices.com/html/s1926pac.htm).1 Drying should be done to 8-10% moisture, and should not exceed 12%. Expected weight loss during drying is 60-70%. Cleaning and drying procedures should be done as fast as possible after harvest to ensure minimum loss from microbial contamination, mold growth and fermentation. Mechanical washers, slicers, and solar or hot air driers may help minimize contamination from dust during post harvest handling operations. Sun-drying peeled ginger takes 7 to 9 days to reach a moisture content of 7.8% to 8.8%. If the ginger is sliced, it takes only 5 to 6 hours by using a cross-flow drier, while it takes 16 to 18 hours to dry scraped whole ginger using the same equipment and conditions. Mechanical drying will ensure a more homogenous and cleaner product. When drying with hot air, care should be taken to adjust air flow and temperature. Drying should not exceed the critical temperature of 60º C to avoid flesh darkening and discoloration. Specific equipment is suggested for optimum cleaning of the dried rhizomes. An air screen separator will help remove dead insects, excreta and extraneous matter, while a rotary knife cutter with a screen separator will help remove residual insects and other extraneous matter. Curing: The green ginger is soaked in water to facilitate the removal of the skin. The skin is scraped off with pieces of sharpened bamboo or bits of sea-shells. The scraped produce is washed and dried in the sun for 3 or 4 days and hand-rubbed. It is again steeped in water for two hours, dried and then rubbed to remove all the remaining bits of the skin. Sun-drying also bleaches the produce. Peeling should be done with great care and skill. The essential oil which gives ginger the aromatic character is present in the epidermal cells and excessive or careless scraping will result in damaging these cells leading to the loss of essential oils. Steel knives are not used as they are found to stain the produce. In Kerala there is also a practice of soaking the peeled rhizomes in a 2% clear limewater for 6 hours before drying to give the dry ginger a good appearance. The dry ginger prepared in this way is not liked in foreign markets especially in the Middle East. Sometimes big plumpy rhizomes free from diseases are selected immediately after harvesting. Dry the rhizomes under shade. Dried rhizomes are put in a pit of convenient size (2 m x 1m) and covered with a plank fitted with 2-3 holes for aeration. In some areas, the rhizomes are loosely heaped over a layer of sand or paddy husk and covered with dry leaves in a thatched shed. For processing into its products, ginger rhizomes are harvested 5 months after planting. The rhizomes are immature, tender and succulent. They are washed in water to remove soil and processed into salted ginger, preserved ginger in sugar syrup or brine and dried into crystallized ginger. Grading: In India, grading is generally done only in Himachal Pradesh. The first grade popularly known as ‘gola’ in the local market is the very bold and round bits of dry ginger, having the maximum dry matter and low fibre contents. The second grade known as ‘gatti’ includes bits of bold round to oblong and is smaller than the first grade. The third and the fourth grades are smaller bits with a small amount of dry matter and high fibre contents. PRESERVATION OF SEED: Seed-ginger has to be stored for about 4 or 5 months from the time of harvesting to planting. Rhizome-rot, dry-rot, sprouting and shriveling are commonly noticed in storage. Keeping the seed-rhizomes in pits is found to be the best method of storage. Healthy rhizomes are selected at the time of harvesting. The rhizomes are then dried in shade and stored in pits dug in a cool place and protected from sun and rain. The pits should not be more than 1 metre deep. A layer of sand or sawdust is put at the bottom of the pit before storage. Either the pit is left as such or is covered with a wooden plank and plastered with mud. In the latter case a small hole is made in the plank through which a hollow bamboo is inserted to provide aeration for the rhizomes. At higher altitudes seed-ginger can be stored safely up to the end of May in an underground store. The trials conducted at the Central Food Technological Research Institute, Mysore, have shown that a combination treatment such as a protective skin-coating containing a fungicide and plant-growth inhibitor couples with and transport of ginger rhizomes without deterioration.