Technology of Fruits Vegetable POST HARVEST TECHNOLOGYI Products
Technology of Fruits & Vegetable POST HARVEST TECHNOLOGY-I Products Pulakesh Basak Lecturer Department of Food Science and Engineering German University Bangladesh, Gazipur.
Fruits are the ripened ovaries of flowering plants. Fruits are juicy edible products of plants and trees and contain the matured ovary including the seeds. Commonly fruits are classified as: v v v v Pomaceous fruits (apple, pear etc) Stone fruits (apricots, cherries, peaches, plums etc) Berries (strawberry, raspberry, gooseberry, grapes etc) Tropical & subtropical fruits (amla, banana, mango, papaya, pineapple etc) Citrus fruits (orange, lemon, grape etc) Shell (nut) fruits (peanut, almond, cashew nut etc) Wild fruits (rose hips, elder berry)
Fruits are divided into groups depending upon the shape, cell structure, type of seed or natural habitat. One system classifies them into the following groups: berries, citrus fruits, drupes, grapes, melons, pomes, tropical and subtropical fruits. Group Fruits name Berries Strawberries, gooseberries, blackberries, raspberries, blueberries Citrus fruits Sweet limes, oranges, sour oranges, lime, lemon, grape fruit Drupes Apricot, sweet cherry, peach, plums Grapes Green grapes, black grapes, seedless grapes Melons Musk melon, water melon Pomes Apples, pears Tropical & subtropical fruits Amla, avocado, banana, dates, guava, mango, jack fruit, papaya, pine apple, pomegranate
Fruit composition Nutritive value v v v v Fruits are very poor source of protein and fat. Avocado is the exception containing 28% fat. Alpha linolenic acid is present in plum, papaya and guava. Fruits contribute to n-3 fatty acid content of diet. Fruits contain high amount of moisture hence they are highly perishable. They are good source of fiber. Fruits are not very good sources of calories. Fruits like bananas give fairly good amount of calories. Ripe fruits contains a higher percentage of sugar than unripe fruit does and the sugar is chiefly in the form of sucrose, fructose and glucose. Generally fruits are poor source of iron. Seethaphal is a good source of iron. Mangoes are excellent source of carotenes. Apart from mango, dates and papaya are good sources of β-carotene. Oranges are fairly good source of β-carotene. Guavas and citrus fruits are sources of vitamin-C. Cashew fruits are inexpensive and rich in vitamin C. Although there is variation of vitamin content from fruit to fruit most fruits in the raw state contain some ascorbic acid. Amla is the richest source of vitamin C. If fruits are bruised, peeled, cooked or exposed to air, alkali, or copper, large amounts of the vitamin C may be oxidized. Apples, pears, cherries, grapes and citrus fruits contain flavonoids which act as antioxidants.
Fruit composition Pigments Like vegetables, fruits also contain different pigments. q Chlorophyll: Guava, gooseberry, country apple. q Carotenoids: Mango, papaya, orange, watermelon (lycopene), musk melon (β-carotene), jackfruit, peaches, tomatoes, grape pink (lycopene, β-carotene), pineapple (β-carotene, violaxanthine) q Anthocyanins: Grapes, blueberries, plum, cherries. q Anthoxanthins: Guava, apple, gooseberry, pears, custard apple, banana. Flavor Volatile flavor compounds are esters, aldehydes, acids, alcohols, ketones and ethers. The flavor of jackfruit is due to 13 esters (mostly 3 -methyl butanoates) nine alcohols, 5 aldehydes, 5 acids and traces of the unusual compounds 2 -acetyle-1 -pyrroline. Sugars, tannins, acids and mineral salts also affect the flavor of fruits. Some fruits contain essential oils which are also important flavor contributors.
Fruit composition Bitterness in Fruits q q Bitterness in citrus fruits can be attributed to compounds of two classes, the limoninoids (triterpenes) and the flavanone glycosides (flavonoids). The precursor of limonin is naturally present and stable in intact citrus tissue but when the fruit is squeezed to yield juice, the active presence of the precursor in combination with the acidic p. H result in the formation of limonin. The principal flavonoid bitter tasting component of citrus fruit is the flavanone glycoside, naringin. It is the mjaor flavonoid of grape fruit. Certain citrus products when heated can develop a bitter-off flavor. The compound thought to be responsible is limonin which is intensely bitter tasting triterpenoid dilactone which can also natarally in citrus products.
Fruit composition There are two types of fruits on the basis of tropical area. These are: (i) Climacteric fruits (ii) Non-climacteric fruits Classification of climacteric and non-climacteric fruits Climacteric fruits Non-climacteric fruits Apple Cherry Apricot Citrus Banana Figs Peach Grapes Plum Pineapples Papaya Melons Tomato Strawberry Mango
Fruit Constituents Fruit composition varies with its type and ripeness of the food. v v v v v Fruits contain water of 70 to 90% by weight. The dry matter content varies between 10 to 20%. Major constituents include sugars, polysaccharides and organic acids. Minor constituents include nitrogen containing compounds, lipids, vitamins, minerals, pigments and aroma compounds. Nuts contain about 20% nitrogen containing compounds and lipids as high as 50%. Avocado is rich in fats. Among the carbohydrates, glucose and fructose are the major mono-saccharides. Other nutrients include proteins (0. 2 to 1%), fats(0. 1 to 0. 4%) and vitamins (mainly ascorbic acid particularly in citrus fruits). Pigments (carotenoid, anthocyanin) and flavor compounds are also present. Organic acids such as malic acid and citrus acids occur in most fruits.
Storage of fruits v v Fruits can be stored for a few months either in cold storage or under controlled atmosphere. The suitability, duration and conditions of storage depends on the variety and quality of fruit. Normally -1 to +20 C temperature with 80 -90% relative humidity used for storing fruits. Fruits Storing time Apples 4 -8 Months Pears 2 -6 months Grapes 2 -3 months Berries (strawberries, raspberries) 1 -2 weeks Cherries 4 -5 days
Storage of fruits v v During cold storage moisture loss results in weight loss up to 310%. Fruits may be stored in frozen condition at -18 to -240 C up to 2 to 4 years. Rapid chilling at -300 C of air temperature is important to prevent microbial growth. Fruits may be stored under modified or controlled atmosphere to lower oxygen (O 2) content.
Fruit Products A variety of products have been developed to provide new fruit products as well as to store surplus fruits for prolonged periods. v Dried fruits v Canned fruits v Rum fruits v Fruits in sugar syrup v Jams, Jellies and Marmalades v Fruit Beverage
Fruit Products Points to be considered while serving foods: Ø Ø Ø Ø Pineapple skin should be removed along with their eyes. Jackfruit should be cut with oil and turmeric to remove the stickiness. All fruits to be eaten must be washed in water to make it safe and free from dust, dirt and insecticides. Fruits that are cut into even size cubes are attractive. Fruits should be cut just before consuming. Fruits that brown on cutting need to be served immediately or served as whole or browning should be prevented. It is better to serve the fruit rather than the juice.
Fruit Products Points to be remembered in making salad: ü ü ü ü Vegetable should be good and of good quality. Knife should be sharp to cut into desirable shape. Wash the vegetable thoroughly in running water so that the dirt as well as the chemicals or fertilizers are washed away. Served the salad immediately after preparing it. Presentation is an important aspect of salad making. Salad ingredients are handled as little as possible. Crispiness of vegetables like cucumber can be achieved by soaking for short time in ice water. Unpeeled cucumbers add considerable color interest to salads.
Vegetables v v The term vegetable generally means the edible parts of plants. Vegetables such as tomatoes, cucumbers, peppers, eggplant etc. Based on consumer acceptance and usage, vegetables are those plant parts consumed with the main course of a meal while fruits are commonly consumed as dessert. Vegetables are plants or parts of plants that are used as food. The term vegetable has through usage come to apply in a more narrow sense to those plants or parts of plants that are served raw or cooked as a part of the main course of a meal. Vegetables supply many nutrients besides providing variety to the diet. They make the food attractive by their color, texture and flavor. Various parts of plants are used as food and the botanical classification of such parts is important because it furnishes some clue to the structure and composition which in turn may influence the use of vegetables in the raw state and the method or time of cooking. Various parts of plants vary in their water, protein, vitamin, mineral and carbohydrate contents.
Classification � Vegetables are classified according to the parts of the plant consumed or color of the vegetable or according to the nutritive value. Botanical classification of vegetables Roots Carrot, beet root, radish, turnip, colocasia Tubers Potatoes, sweet potatoes, tapioca Bulb Onion, garlic, leeks Leaves Cabbage, lettuce, spinach, amaranth Flowers Plantain flower, cauliflower, neem flower, broccoli Fruits Tomatoes, lady’s finger, pumpkin, capsicum Legumes (pods & seeds) Peas, beans, bread beans, double beans, Bengal gram tender, red gram tender. Stems Plantain stem, ginger, amaranth stem Seed sprouts Green gram, bengal gram, soyabean sprouts Fungi Mushrooms Algae Spirulina
Vegetable Composition v Nutritive value: Vegetables are called protective foods as they are rich in minerals and vitamins. Nutritionally they are classified into 3 groups. Ø Green-leafy vegetables; Ø Roots and tubers; Ø Other vegetables. o Nutritive value of green-leafy vegetables: Leaves are the manufacturing organs of a plant where the life-giving process of photosynthesis takes place. In the cells, photosynthesis transforms elements into carbohydrates which are carried out to other parts of the plant. The leaves in consequence are low in carbohydrates and energy but they good sources of β-carotene, calcium, riboflavin, folic acid, ascorbic acid, iron and vitamin k. ü Generally green leaves vegetables are good sources of vitamins and minerals. They are excellent in carotenes which are converted to vitamin A. Among all the greens colocasia leaves contain highest amount of carotene & cabbage has the least. The greener the leaves the higher the carotenes. β-carotene also good antioxidants. ü Greens are good sources of B-vitamins particularly riboflavin and folic acid. Drying and withering reduce B-vitamins.
Vegetable Composition � Green leafy vegetables also contain Vitamin C (Agathi, drumstick leaves and coriander leaves) and can be used as substitute for fruits if needed. Green leafy vegetables are also rich in iron (cauliflower leaves, beetroot leaves). Agathi, colocasia leaves, drumstick leaves and fenugreek leaves contribute calcium. The availability of calcium and iron of the body is limited as green also contain oxalic acid. Greens generally are high in moisture and easily withered and need to p[reserve properly. Greens are not good sources of protein, carbohydrate and fat and hence they do not contribute to the energy value of food. Greens are good sources of fibre which help in preventing degenerative diseases. Of all the green leafy vegetables agathi is the most nutritious one. o Nutritive value of roots and tubers: ü Roots and tubers give more calories compared to green-leafy vegetables because they contain more starches. Carrots contain high amount of carotene though this amount is lower when compared to the content present in green leafy vegetables. � � � ü
Vegetable Composition � Roots and tubers are fairly good sources of vitamin C. They are poor source of calcium, iron and B-vitamins. They are poor source of protein. o Nutritive value of other vegetables: � � ü ü ü ü They contain high amount of moisture and hence they are highly perishable. They are generally poor in nutrients. They are fairly good source of vitamin C. They contribute to the fiber content of the diet. Plantain green contains high amount of iron. Capsicum contains vitamin C. Small bitter gourd is more nutritious than the ordinary one. v Pigments: The bright colors of many vegetables contribute much to their appeal. The color result from the various pigments contained in their tissues. Most of the pigments occur in plastids- specialized bodies lying in the protoplasm of the cell. Sometimes, the water-soluble are dissolved in the vacuoles and not generally distributed throughout the cell. The chief pigments of vegetables and fruits can be classified as (i) Water soluble (ii) Water insoluble.
Vegetable Composition Water- insoluble pigments: (a) Chlorophyll: Ø Chlorophyll-a is intense blue green in color and chlorophyll-b is dull yellow green in color. They occur in plant in the ratio of 3 a: 1 b. Chlorophyll-a is present in the florets of blue-green broccoli and chlorophyll-b is present in stalks. Chlorophylls are mostly insoluble in water and dominant in unripe fruits. Other pigments present are masked by dominating chlorophyll. This pigment is present in green leafy vegetables, capsicum, beans, peas and chillies. (b) Carotenoids: Food Pigments q Yellow corn Cryptoxanthin Tomatoes Lycopene, β-carotene Red capsicum Capxanthin, Lycopene, β-carotene Green capsicum Lutein, neoxanthin Carrots β-carotene, α-carotene, γ-carotene, xanthophyll, lycopene.
Vegetable Composition Water soluble pigments: These pigments are not membrane-bound molecules but are dissolved in the sap of epidermal cells of these parts. Flavonoids are classified into (i) anthocyanins and (ii) anthoxanthins. Anthocyanins are highly water-soluble pigments that range in color from red to purple. The anthoxanthins are colorless or white. Anthocyanins and anthoxanthins are important cyanidin-based compounds. q v Organic acids: Vegetables contain a number of organic acids, metabolic products of the cells. Formic, succinic, citric, acetic, malic, fumaric, tartaric and benzoic acids are present in fruits and vegetables. The concentration of acid is lower in vegetables than in fruits. Tomatoes and vegetables with the concentration of acid have a p. H ranging from 4 to 4. 6. Foods like lemon, mango green, tamarind (tartaric acid), gooseberries, raw citrus fruits and grapes have low p. H. Most of the vegetables have p. H 5 to 5. 6. Potatoes and peas have p. H 6. 1 to 6. 3, more neutral in state
Vegetable Composition v Enzymes: Enzymes are found in plant cells. They function as catalysts in chemical reactions. They are composed of proteins and destroyed by heat and by chemicals that coagulate them. There are two types of enzymes that are normally present in plant substances, (i) hydrolytic enzymes (ii) oxido reductases. v Bitter compounds: Curcurbitacins and oxygenated tetracyclic triterpenes which may occur in both the free form and as glycosides in cucumber may impart bitterness. Potatoes that have been exposed to light, mechanical damage and sprouting may become green due to rapid increase in the concentration of certain toxic steroidal glycoalkaloids such as solanine and chacomine. These impart to the potatoes a bitter taste. Gastrointestinal and neurological symptoms may develop due to solanine poisoning. These alkaloids are not destroyed during the process of cooking, baking and frying. The best way to minimize the hazards from these toxins is taking appropriate precautions against damage or insect attack during growing, harvesting, storing and processing potatoes. Sprouting during storage diminishes a potato’s processing and nutritional qualities.
Vegetable Constituents Vegetables, apart from providing nutrition, contribute to the appetizing color, texture and flavor to the food. v Most vegetables are high in water content (>80%). v Low in protein (~3 to 3. 5%) and fat contents. v Legumes (peas and beans) have higher protein content and sweet corn has a higher fat content. v Dry matter content vary between 10 to 20%. Dry matter content constitutes: Carbohydrates 3 -20% Nitrogenous compounds 1 -5% Minerals ~1% Crude fiber 1% Fats 0. 1 -0. 3%
Vegetable Constituents v v v v They also contain vitamins and minerals. Glucose, fructose (0. 3 -4%) and sucrose (0. 1 -12%) are main carbohydrates constituents. The major nitrogenous compounds include proteins, particularly ligases, lyases, hydrolases etc. Malic acid and citric acid occur in most vegetables. Oxalic acid largely present in green beans, red beet, Brussels sprouts. Most vegetables contain ascorbic acid, riboflavin and thiamine. Minerals include potassium, calcium, iron, sodium, magnesium present in vegetables. Pigments include chlorophyll, betalains and carotenoids also present in vegetables.
Storage of Vegetables Most vegetables are consumed fresh. However, vegetables can be stored for prolonged periods depending on their type. Ø Ø v v v Root and other vegetables such as potatoes, carrots celery, onions, cabbage and turnips can be stored for months while leafy vegetables such as lettuce, spinach beans, peas, cauliflower, cucumbers, tomatoes and asparagus can be stored for a few days only. Storage of vegetables brings about changes in their composition due to storage temperature. Cold storage of vegetables at -1 to +40 C With 80 -95% relative humidity is the most appropriate method. During storage, 2 -10% weight loss can occur. Deep freezing or frozen storage of vegetables is practiced in case of beans, peas, pepper, carrot, and edible mushrooms. Green beans are blanched in boiling water for 2 -4 min or by steam for 2 -5 min and cooled at -400 C in plate or air freezer and then cooled at -18 to -200 C. Most of the nutrients and vitamins are preserved by deep freezing.
Storage of Vegetables v Factors affecting storage life: Loss of water: Transpirational loss of water is one of the main processes that affects the commercial and physiological determination of vegetables after harvest. The moisture loss adversely affects the appearance, texture, flavor and weight of the products. Most noticeable effect of moisture is the softening of the tissues caused by loss of turgidity. q Respiration and metabolism: Vegetables are living commodities and continue to respire even after harvest. Respiration uses the stored food, leading to its depletion and consequently the loss of quality. Hence, storage life of vegetables is influenced by rate of respiration and is associated with biochemical activity. Vegetables are classified as follows depending on the rate of respiration. q Classification Food Very low respiring Potato, onion Low respiring Carrot, celery, cabbage, cucumber Moderate respiring Cauliflower, lady’s finger High Broccoli, pod-seed, sweet corn
Storage of Vegetables The low respiring commodities have a long shelf life in contrast to the short life of high respiring commodities. q Microbial spoilage: Vegetables are susceptible to the action of a variety of micro-organisms, thereby leading to substantial decay losses during post-harvest handling. v Factors that extend shelf life: § Harvesting at optimum maturity with minimum injuries. Using proper sanitation procedures. Providing optimum storage condition, namely, temperature, humidity and also the storage atmosphere during all marketing steps. § § v Post harvest losses: § Environment factors such as ambient temperature and relative humidity which influence the rate of deterioration of foods. The length of time between harvesting and final consumption. Post-harvest handling, storage and processing practices. In India, post-harvest losses of vegetables are around 10 -30%. § § §
Storage of Vegetables Changes during maturation: As fruits and vegetables mature, they gradually increase their content of cellulose, hemicelluloses and even lignin. This increased structural support for cell walls causes fruits and vegetables, particularly the later, to become less tender as they mature. Vegetables are much more likely to increase than fruits in lignin as they age, resulting in the development of a rather tough, woody texture. Lignin is a structural component of some plant foods that is removed to avoid a woody quality in the prepared food
Vegetable Products These include: v Dehydrated vegetables v Canned vegetables v Pickled vegetables v Vegetable pastes, juices & powders. Reference book: Food science – B. Srilakshmi Food processing and preservation– B. Shivsankar
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