FOOD PROCESSING OF ROOTCROP AND PLANTAION CROPSS

FOOD PROCESSING

1. Postharvest handling of Root crops VALUE ADDING ESSENTIALS TOPIC NO.4

2. Post-harvest handling and Value-adding Techniques for Root Crop s The root and tuber crops consist of the plant with swollen roots and underground stems in which large quantities of starch are stored. Root and tuber are main sources of calories for a substantial part of the rural population in many sub-Saharan countries and also an important part of the urban diet in a number of the countries. Root and tubers are high-moisture vegetables but (from 60-90%) but also considered as semi-perishable crops with relatively poor post-harvest storage qualities.

3. Another objective of processing is to eliminate undesirable constituents, such as cyanide in cassava, the removal of which can be only effected through series of operations. The most important operation in processing roots and tubers is drying. The major traditional products from roots and tubers are dried chips, non-gelatinized fermented fours, fermented gelatinized grits and pre-gelatinized flour. The root and tuber crops under consideration include: Cassava, sweet potato and yam

4. COMMON ROOT CROPS CASSAVA Cassava is the most widely cultivated root crop in the tropics and because of long growth season (8–24 months ), its production is limited to the tropical and subtropical regions in the world. Cassava is a perennial shrub belonging to the family Euphorbiaceae . Cassava originated in South America and subsequently was distributed to tropical and subtropical regions of Africa and Asia. Cassava plays an important role as staple for more than 500 million people in the world due to its high carbohydrate content .

5. A number of bioactive compounds , namely, C yanogenic Glucosides such as linamarin and lotaustralin , Non- C yanogenic G lucosides , hydroxycoumarins such as scopoletin , terpenoids , and flavonoids , are reported in cassava roots. Yams Yam is a member of the monocotyledonous family Dioscoreaceae and is a staple food in West Africa, Southeast Asia, and the Caribbean regions. Yam is consumed as raw yam, cooked soup, and powder or flour in food preparations. Yam tubers have various bioactive components, namely, mucin , dioscin , dioscorin , allantoin , choline , polyphenols , diosgenin , and vitamins such as carotenoids and tocopherols . Mucilage of yam tuber contains soluble glycoprotein and dietary fibre . Several studies have shown hypoglycemic, antimicrobial, and antioxidant activities of yam extracts.

6. Sweet potato The origin of sweet potato is Central America , but at present it is widely grown in many tropical and subtropical countries in different ecological regions. It is the seventh largest food crop , grown in tropical, subtropical, and warm temperate regions in the world. Sweet potato can be grown all around the year under suitable climatic conditions and complete crop loss under adverse climatic conditions is rare; thus it is considered as an “insurance crop.” The crop is particularly important in Southeast Asia, Oceania, and Latin America regions and China claims about 90% of total world production . Sweet potatoes are considered as a typical food security crop for disadvantaged populations as the crop can be harvested little by little over a long period of time. In addition, sweet potatoes are rich in dietary fibre , minerals, vitamins , and bioactive compounds such as phenolic acids and anthocyanins , which also contribute to the color of the flesh.

7. Gab i Colocasia esculenta is a tropical plant grown primarily for its edible corms, a root vegetable most commonly known as taro, or kalo . It is the most widely cultivated species of several plants in the family Araceae that are used as vegetables for their corms, leaves, and petioles Potato Potato , ( Solanum tuberosum ), annual plant in the nightshade family ( Solanaceae ) , grown for its starchy edible tubers. The potato is native to the Peruvian-Bolivian Andes and is one of the world’s main food crops. Potatoes are frequently served whole or mashed as a cooked vegetable and are also ground into potato flour, used in baking and as a thickener for sauces. The tubers are highly digestible and supply vitamin C, protein, thiamin , and niacin .

8. STORAGE CONSIDERATION OF ROOTS AND TUBERS Cassava Fresh roots will deteriorate if stored for more than 48 hours , even in a cool place. Primary deterioration, or physiological deterioration, begins shortly after harvest (within 48 hours) and consists of blue-black streaking followed by browning; It is usually associated with damage at harvest and the degree of susceptibility varies among varieties. Under subsistence conditions, the storage difficulty is therefore overcome by leaving the roots in the ground until needed. This system has many disadvantages. Large areas of land cannot be released for planting other crops; susceptibility to loss is increased, the quality of cassava diminishes, making it unsuitable for some preparations; and extra time is needed for intermittent harvesting of cassava, especially when farms are situated at long distances from villages.

9. Other rural cassava storage techniques include keeping uprooted in holes covered with plant material and soil, piling it in heaps and watering it daily; and putting small quantities into water. All these practices are based on the principle of preventing the loss of moisture from the cassava. However, they can only extend the storage life of cassava from a few days to a few weeks. Sweet potato After harvesting sweet potato are cured by subjecting them to a temperature of 27oC – 34oC at 85-90% humidity for 4-7 days. Curing promotes the development of suberized (cork-like) layers and reduces the incidence of infection by fungal disease - producing organisms.

10. Sweet Potato Sound, healthy tubers, can be kept for 2-3 months when stored in a cool, dark place. Also, it can be stored for short periods on the floor of well-ventilated rooms, or in trenches 40-50crn deep, with sides, lined with layer of grass. Sweet potato can be stored in lined pit and covered with a layer of grass, after which the pit is covered with at least 15cm of soil (Pfeiffer, 1982).  selecting for storage only the fully mature and undamaged roots.  curing the roots at 30° to 32°C and at 85% to 90% relative humidity for four to seven days  handling the roots carefully and limiting their handling to a strict minimum  keeping the storage temperature at the lowest level possible (an optimum of 13°C)  keeping the relative humidity as close as possible to 85%-90%.

11. Yams In practice most yams, unlike cassava, are normally stored fresh. A small proportion is however processed and stored dry as sun-dried chips or flour. The simplest storage technique is leaving the tubers in the ground until needed. A number of structures are traditionally used for yam storage, the commonest being the yam barn. In this traditional structure, lack of proper control of physical conditions, physiological processes, pests and micro-organisms lead to considerable losses (10-15% by weight in the first 3 months and 50% after 6 months)

12. Potato Temperature and tuber damage are the two most important factors in successful potato storage. Very careful handling is the key to preventing damage. Harvesting is best done when the soil is slightly moist to prevent abrasion and the tubers lifted carefully to avoid damage. Ideally they should be left to dry for few hours in the field, collected in field containers and placed in a cool, shady place. Potatoes for food (ware potatoes) must not be exposed to light for more than a few hours otherwise they turn green, develop an unpleasant taste and may become toxic.

13. It is important to make the distinction between ware potato storage and seed potato storage. The objective of ware potato storage main is to obtain the maximum quantity of tubers, of acceptable quality to the consumers, at a rate to meet consumer demand. This requires the lowest possible quantitative and qualitative losses, with no or little sprouting, kept in the dark to prevent greening and firm tubers, all at an economical cost. In seed potatoes storage the objective is to have optimum development of sprouts prior to planting. In both cases the farmer requires the maximum return from his investment in time, materials, equipment and buildings. Temperature influences the rate of respiration of the tubers, sprout growth and the development of microorganisms causing rotting Ware potatoes can be stored up to six months in tropical highlands without significant losses provided that:

14.  the variety of potato is one with a long dormancy or the tubers are treated with a sprout inhibitor if storage duration is required to continue beyond the period of dormancy;  the potatoes are free from diseases, damage or insect infestation;  storage temperatures are kept to levels that do not induce high rates of respiration;  the relative humidity within the store is kept at sufficiently high levels to reduce water loss from the tubers;  the potatoes are not wet as a result of rain or condensation. Ware potatoes can be stored up to six months in tropical highlands without significant losses provided that:

15. VALUE- ADDING OF ROOT CROPS Products of root and tuber crops are manufactures through a wide range of processes. Some products, such as beverages made from sweet potatoes, may acquire additional processing. For each process there are generally various options that differ in technological sophistication. Starch, for example, can be extracted either manually with rustics equipment or by means of high technology in a fully automated factory. The type and complexity of the technology you use depends on several factors:

16.  Scale of operation  Capital investment  Operator’s level of education  Value of product  Conversion of extraction rate  Product quality or purity  Raw material characteristics  Availability of services (water, fuel and electricity)  Cost of labor.

17. ROOTS AND TUBER PR0DUCTS PRIMARY PROCESSED 1.Fresh root and tubers At harvest Clean and graded With improved shelf life Prepared Non-commercial quality (for animal feed) Boiled (tubers) to remove anti nutritional Ensiled (roots) for storage as animal feed.

18. 2. Fresh leaves and vines 3. Sun-dried pieces, chips and slices or roots and tuber 4. Flakes and granules 5. Flour 6. Fermented starch 7. Modified starches SECONDARY PROCESS ED 1. Starch and Flour a. Bakery good, soups and sauces bases, processed meats, pastas, noodles, beverages bases and snack foods b .Textiles , paper, glue, plywood, oil and pharmaceuticals c. Animal feed rations d .Alcohol e. Glucose f. Monosodium glutamate

19. 2. Fresh roots and tubers a. Frozen, canned and vacuum-packed b. Protein enriched via fermentation c. Use in beverages, jam and sauce production d. Snack foods (chips, crisp, etc) e. Delicacies 3. By-product a . Animal feed b . Products of industrial processing